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A Case Study of auditory Agnosia: Linguistic and Non-Linguistic Processing
A CASE STUDY OF AUDITORY AGNOSIA: LINGUISTIC AND NON-LINGUISTIC PROCESSING' Martin L. Albert, Robert Sparks, Theodor von Stockert and Daniel Sax (Boston Veterans Administration Hospital and Boston University Medical School)
Auditory agnosia is a generahly accepted name applied to the clinical condition of disturbed capacity to recognize the nature of heard non-verbal sounds. Cases describing this condition, usually in combination with other auditory perceptua1 defects, have appeared in the neurologka:l literature ·since the Latter part of the nineteenth century (Edgren, 1895; Liepmann, 1898). However, this syndrome is rare, and its underlying neurological mechanisms are poorly undevstood. Recent system~tic attempt)s to clarify these mechanisms have demonstrated cont)radictory results (Spinnler and V.ignolo, 1966; Faglioni, Spinnler and Vignolo, 1969; Albert, Goldblum, Hecaen and Benson, 1971). Recently, we hav·e had the opportunity to evaluate at length an individual who had a~s a major neurological disturbance an impaired capacity to recognize the nature of heard non-verbal sounds. Techniques of testing, including, among other tests, accelerated and delayed audioory feed-back, presentation of dichotic stimuli, and auditory evoked corticad responses have yielded resuhs which aid in the interpretation of the mechanisms underlying this disorder. CASE REPORT
A 58-year-dld male right-handed self-employed leather goods designer was admitted to the Aphasia Research Section of the Boston 1 Some of the work reported here was supported by Public Health Service Grant NS-06209 to the Boston University School of Medicine.
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M. L. Albert, R. Sparks, T. von Stockert and D. Sax
V'et:erans Admin±stration Hospirral on May 25, 1971, for ev,aluation of auditory perceptual defecus. On May 20, 1971 the following sequence of events had occurred. While he was working in his leather goods shop his speech suddenly became garbled. He then slumped to the floor, hitting the back of his head. He rose immediately and pointed to his ears. He then turned off the ~lectridty for the machinery and asked a co-worker if the machinery had been turned off. He left his shop, went to his car, started the engine. However, he could not be sure if the engine was on. He continued to try to start the engine which was, indeed, running a:nd finahly drove home. By the t,ime he reached home his speech was incomprehensible. Because of his bizarre behavior, his wife drove him to a near"by hospital. The admitting physician thought the patient had suffered a stroke and had him sent immediat:ely to the Neurology Service of the Boston Veterans Administration Hospital. Pertinent highlights of the admission evaluation included a description of "inappropriate gesturing and jargon-like speech." What was considered confusion was the patient's attempt to wvite with the eraser end of a pencil. Peripheral hearing "seemed to be intact ". A brief language examination demonstrated inappropriate responses to questions but, in general, "... he seemed to comprehend." He could fallow written commands and he "copied well." The remainder of the neurological examination was within normal limits. Among the initial diagnostic considerations was that of "conversion hysteria." During the next few days his condition rapidly evolved. It became clear that he had a continuing deficit of auditory processing, and he was transferred to the Aphasia Research Seccion for further evaluation. Past medical a:nd social history are pertinent. The patient was born in a small town in Rusrsi,a. His family left Russia when he was about 8 yearrs old an.d travelled for four years through Europe, then Cuba, ,and fina1ly the United States . .A:s a 'result, the patient speaks Yiddish as well as English, and has some knowledge of Russian, Ukran>ian, Polish, German, and Spanish. He graduated from college in the United States and was a high-school teacher for 19 years until two years ago. Since then he has worked as a self-employed designer of leather goods. In 1968 he had an inguinal he.vniorrhaphy. Immediately following this operation he discovered that he could not hear as well as previously, especially with his left ear. Although he had always used his left ear for listening on the telephone, he had now started using
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his right ear. In the years following 1968 he had seven admissions to a phychiatric hospital with di'agnoses of depressive reaction and acute anxiety reactions. He did not receive electro-convu[sive therapy.
Physical evaluation The neurologicrul examination showed a short, slender, hyperactive, middle-aged man. He was oriented to time, place, and person. Recent and remote memory were intact. Blood pressure was 130/80 in hoth arms. Corrected visual acuity was 20/20 in hoth eyes. Visual fieild testing on the Goldman perimeter revealed no visual field defect. However, extinction of visual stimuli from the left homonymous half-field was present with double simultaneous stimulation. Cranial nerves were otherwise intact except for the auditory nerves. A description of examination of auditory pathways is included below. Reflexes were slightly exaggerated on the right side. No Babinski respoll!se was elicited. Motor and cerebehlar function were normal. Somesthetic sensation was normal and there was no somesthetic extinction to double simU'ltaneous stimulation. Repeated electroencephalography demonstrated persistent and abnormal theta activity from the right parieto-temporo-occipital deviations. Radioisotope brain scanning demonstrated a left posterior sylvian lesion. This evidence, therefore, is suggestive of bilateral posterior corticaJ lesions.
PROCEDURE
Study of this patient included examination for aphasia, audiological examination, testJs for sound localization, dichotic signals tests, recognition of non-verbail sounds and poplllla:r songs, parts of the Seashore Measures of Musical Talents, testing of his ability to receive and send Morse code because of a pre-morbid proficiency as a "ham" radio operator, and an examination for auditory evoked cortical 1Cesponse. Other tests concerned with manipulation of side-tone in auditory feed-hack and a test involving auditory masking were used to study their effect upon the patient's prosody of speech and frequency of paraphasia. These tests included delayed and accelerated feed-back, and excessive white noise masking.
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M. L. Albert, R. Sparks, T. von Stockert and D. Sax
Aphasia examination On initial detai[ed language evaluation on May 25, 1971 the following characteristics were observed. Spontaneous speech was fluent with many verba!l and phonemic paraphasias and frequent attempts at self-correction. Naming was correct about 80% of the time, and naming errors involved predominantly verbal paraphasias. Comprehension of spoken language was moderately impaired. His understanding of sentences was better than that for single words. His repetition was grossly impaired. Serial speech was better than repetition or spontaneous speech, but was not normal. Writing was paragraphic with both hands. Reading aloud was poor and demonstrated errors simi1lar to thos•e in his spontaneous speech. Reading comprehension was good. Related corticad function testing showed essentially normal results for right-1left orientation, spatiail orientation, finger recognition, color recognition, and vi•sua,l object recognition. Singing was poor, both words and melody. Gailcu1ating ability was impaired. The over~a11 impression was of a predominantly posterior type of aphasia. Repeat language evarluation on June 10, 1971 using the Boston Diagnostic Aphasia Examination (Goodglass and Kaplan, 1972) showed considerable improvement. The patient's auditory compre hension was now only minimally impaired. Comprehension of isola ted words was almost completely normal. Sub-test scores showed minor errors in both body-parts identification and compliance with the most complex multi-part commands. The patient's speech output continued to show some paraphasias, but without signifi·cant limit·ations on his ability to communicate. Articu1lation and grammatical structure were normal with an average phrase length of six or seven words. The paraphasias were predominanuly phonemic in quaHty with near-miss approximations to the target words. This on:ly moderately impaired his performance on such sub-tests as responsive speech, confrontatlion naming, body-part naming, and oral reading. He was frequently self-critica!l of Ms errors and often eflident at voluntary self-correction. Repetition of words and high-probability phmses was mildly impaired by phonemic paraphasia. Repedt,ion of low-probability phrases was more impaired. His speech output had a dysprosody which cou[d best be characterized as dysrythmic. Phrases were rapidly delivered but with frequent elongation of vowel sounds. Each phrase wars followed by a
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pause before the next burst of words. The over-a!Jtl impres·sion was of a rather explosive and loud type of speech similar to that sometimes observed with normal individual•s in reaction to delayed auditory feed-back. Throughout the period the patient was in the hospital he complained frequently about what he described as an echo-Hike quarlity of his own voice. He stated, "It's almost as if I hear my own voice [ater than I shoU!ld." Narrative writing (description of a picture) was within normal limit•s. Phonemic paragraphic errors appeared in writing single words to dictation but not in sentences. Ability to sing a familiar melody was severely impaired but this was apparently no wol'se than his pre-morbid deficiency. Duplication of tapped rhythms was severely impaired. Related cortical function examination showed moderately impaired abil.ity to draw to command, mildly impaired abiJ.ity to use arithmetic processes, and a more severe degree of impairment in clock-setting and duplication of block-designs. Memory for stick designs was norma[ and there was no evidence of finger agnosia. On the Wechsler Adult Intelligence Scale, performed on June 11, 1971, his scores were: Verbal121, Performance 101, Fu:ll Scale 113. Audiological examination
Hearing was tested with pure-tone audiometry using ISO standards. The first examination, performed on May 25, 1971, showed a significant bi!lateral sensori-neural loss of questionable re!liability due to what appeared to be a poor attention span, particularly when signal strength approached his thresholds. A second and third examination (June 3 and 15) demonstrated a less impaired hearing profile. The results of these two latter examinatJions were identical and their reliability was further confirmed by Bekesy audiometry. An averaging of thresholds at 500, 1000, and 2000 Hz produced an estimated ·speech reception threshold of 24 dB in the left ear and 20 dB in the right. Thresholds for the higher frequencies were more elevated. The SIS I test scores suggested some recruitment but only at 4000Hz. Of some interest was the patient's report that he heard all pure tone signals and accompanying contralateral narrow-band masking bilatarally. Figure 1 shows his audiogram.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
432
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Sound localization The patient',s confusion concerning the source of auditory signals during the audiometric test led to a further examination for sound locailization ability. The resuhs were compared with those of a control group of aphasic male patients and a group of normal adult males. The patient was blind-folded and then exposed to a series of short bursts of noise generated by a Barany box. Twenty trials were given for each condition. The first condition tested for left-tight localization with the source of sound parallel to the left or right ear at a distance of two feet,. He was correct in localizing the source of the sound in on!ly 35% of the trials on the left and 55% on the right. By compadson, the mean score of a control group of six aphasic patients was 85% correct on the left and 80% correct the right. The mean score of a group of five normals was 90% correct on the left and 92% on the right. The patient's errors consisted of mis-location of the sound as coming from above or behind him. The second condition tested for above-below locailization on the right or left. In this case the Barany box was three feet above or below each ear. His acruracy under these conditions was further diminished. He continued to mis-locate the side of the source of sound and was
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accurate for above-below choices onJy 5% of the time on the left and 15% on the right. By comparison, the aphasic control group produced a mean of 75% correct on the left and 85% on the right. The means for the normail control group were 92% on the left and 95% on the right. Dichotic signals
Results of dichotic tests for digits and words showed total extinc tion by the left ear for both digits and words. Correct repetition of monaural presentation of digits occurred in 80% of the items for each ear. Errors demonstrated residual! in-sphere paraphasic responses. Correct repetition of monaura!l presentation of words occurred in 70% of the items presented to the left ear and 80% on the right. Again, the same kind of errors occurred. Explanation for such left earr extinction in right-handed brain-damaged patients has been suggested by Sparks, Goodglass and Nickel (1970). Recognition of non-verbal sounds
One of the most striking auditory processing defects present in tMs patient was an impairment in his ability to recognize the meaning of non-verbal sounds. This deficit was tested using the technique described by Albert et aJ.. (1971 ). The subject is shown an array of 20 pictures of sound-producing objects, animals, or events. Ten sounds are presented by tape recorder. For each test sound the subject must indicate the picture which represents the natural source of the sound. For each sound there are pictures which represent: 1) the natural source of the sound, 2) the source of a sound in the same acoustic category as the sound presented, 3) the source of a sound in the same semantic category as the sound presented, and 4) the source of a sound which has no relationship to the sound presented. All pictures remain before the subject during the entire test procedure. This methodology is a modification of a similar test described by Vignola (1969). At the time of the first presentation of this test on May 20 the subject was able to name correctly aM the pictures when they were presented alone. He could aJ:so point correctly to aM of the pictures when the na:me was given. Exposure to the test itself showed a remarkable inability to identify the meaning of sounds. He failed nine out of ten trials. The one correct identification was a violin.
434
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
When hearing several cows mooing he said, "I hear a lot of noise but I dont't know what it is." When hearing a piano he said, "It sounds like music perhaps - very loud like a drum." His reaction to a dog barking was, "How come I can understand your voice but not these sounds? " A second presentation on June 4 showed only miM improvement with seven errors out of ten triak His correct identifications were all musical instruments - drums, a piano, and a violin. Again, his reaction were similar. When he heard a bird singing he said, "I hear the sound but I cant't seem to associate it with any of these pictures." Immediately after the above binaural presentation, the same ma terial was presented monaurally with contradatera~ white noise masking. He fahled to identify nine of ten items in each ear. Again, his correct identification was a violin. A third presentation on June 8 showed some improvement. He was corvect in identifying five of the ten items - three musical instruments and also the sound of birds singing and of a typewriter. On June 8 a second test, similar in principle to the first, used some of the pictures and recorded sounds from the test of meaningful sound recognitrion reported by SpinnJer and V,ignolo ( 1966 ). In this case; however, the patient is asked to select one of only four pictures as the correct source of the sound. This more limited choice selection is simpler and as a resudt perhaps less sensitive than the procedure described abov·e. Correct selection of the appropriate picture occurred 88% of the time. Verbal identification of the sound without pictures was correct ot11ly 25% of the time. In thfs instance there were interesting verhal misidentifications. For instance, the sound of a vidlin was identified as a musicllll instrument but "not in the string group." The neighing of a horse was identified as a bird. The rather good non-verbal sound recognition on this test is consistent with the improvement with tiffie on this task noted on the previously described test. Recognition of melodies
Free field presentation of such popular songs as "Yankee Doodle," "Happy Birthday," and "Sidewalks of New York" yielded the follow ing results: verbal identification, 30% correct; multiple-choice written titles, 100% correct. This would suggest that recognition of the melodies was normal!. The poor verbail identification score,
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parallel to the poor verbal performance in identifying non-verbal sounds on the Vignolo test, reflects a defect in retrieving the verbal components on both these tasks. Dichotically presented popular melodies
The same popular songs as used above were presented dichoticru1ly, one song delivered to the left ear simuhaneously with another to the right ear. Again, multiple-choice printed titles were presented. The results showed complete extinction by the left ear, consiJsvent with the left ear extinction of digits and words. Morse code and Seashore Measures of Musical Talent
The patient's long-standing interest and profidency in sending and receiving Morse code suggested that certain of the sub-tests of the Seashore Measures of Musical Talents might be of inverest. Results of the vests for pivch discrimination, loudness, rhythm and time ail showed scores at less tha:n the fifth percentile. Of specific interest, considering Ms avocationatl interest in Morse code, was the remarkable insensiti\nity to rhythm and time differences. The patient's pre-morbid skill in Morse code led to examination of his current aptitude. Accuracy in receiving s·ingle l·etters was 35% correct, receiving words was 0% correct. Sending individual letters was 58% correct, sending words was 90% correct. Although it is not unusual for proficiency of sending Morse code to be better than that for receiving, the discrepancy here is cons1dered significant and focuses attention, again, on his central auditory processing defects. Relaved to his poor performance on the rhythm-tapping part of the aphasia examination was the awkward dysrhythmic manner in which he managed the key while sending the code. Accelerated and delayed side-tone (Auditory feedback)
Examinations for the effects of accelerated and delayed side-tone were administered by Dr. Sheila Blumstein and Dr. Harold Goodglass. Davidson (1958) report's that in his normal popu1ation the acceleration of side-tone from a normatl delay of one mHlisecond to one-half a millisecond (vocal chords to cochlea) faciHvated the speech process by increasing the rate of oral reading a:nd increasing the extent and rate of inflection.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
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Using the conditions of accelerated feedback s·et forth by Davidson, no observable change in the prosody of this patient's speech was noted. His speed of oral reading increased over that of normal conditions, using the same reading maberial, by 26%. This, however, is not significantly faster than the increased rate of 19% he achieved through practke effect under normal conditions. Figuve 2 shows the effect of practice on five trials and the effect of acceleration and delay of side tone. Practice Effect ec.
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Delayed side-tone (delayed auditory feedback) exaggerated the abnormal features characteristic of this patient's speech production. Nor:ma:1ly, his speech was produced with short staccato bursts of three words or more, his intonation pattern tended to end with a rising rather than falling pitch contour, vowels were lengthened and often distorted, and phonemic paraphasias commonly occurred. Under de layed side-tone all of these features were more pronounced. As the delay increased the padent's speech rhythm was characterized by short bursts of speech with increasingly longer pauses between bursts,
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intonation patterns had more of a "sing-song" quality, vowels became increasingly lengthened and exaggerated, voice intensity rose, and production errors such as sound transpositions, repetition of syllables, etc. became more frequent. The effect of delay.ed side-tone on speed of reading was variable. Delay of one-sixth of a second showed a slight increase in the time required on the :first trial and approximately the same amount of increased speed on the second. Delay of one-:thhd of a second showed a uniform degree of slowed rate on both trials. Delay of two-thirds of a second again produced variability. Trial One showed some slowing, trial Two showed increase in speed. The variability might suggest some effect of delayed side-tone when compared with the steady rate of incr·ease in speed resulting from practice effect arlone. Effect of white noise masking
Ninety decibels of white noise masking were presented binaurally and the patient was asked to read test paragraphs. There was no apparent change in the prosody or frequency of paraphasic errors as a result of almost total masking of air-conduction auditory feedback. However, the patient stated that it was pleasant to get temporary l'eilief from the echo~like quality of his voice. Auditory evoked cortical response
Silver EEG needle electrodes with high impedance at low fre quencies were used in a:hl evoked response recordings. The electrode placements chosen corresponded to the international 10/20 system and used bipolar recordings £rom T3-T5 and T4-T6 posritions respec tively. A bipolar FP1-FP2 electrode was also used to rule out extraneous changes in the response 2° to eye movement. The evoked l'esponse was recorded on a Grass Model 610, 8 channel pdlygraph and then into an PM tape recorder with an audiomonitor channel. The gains were set accurately using a Fabritek averager. Low frequency filtering, 3Hz or less, and high frequency filtering, 300 Hz, were employed. The signals on the magnetic tape were then fed into a signal averager (Fabritek) which displayed the results on an X-Y plotner. The clock pulse generator drigitimer with a marker pulse triggered the stimulator which triggered both the polygraph and the stimulator that suppilied a olick at irregular intervals which varied between 2 and 4 duration.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
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In obtaining the auditory evoked potientials 256 tria:ls were averaged. The bipo1ar recording revealed a small evoked response of 2(.1.V which is partially obscured by muscle artifact. An initial negative deflection (N1) was recorded bilaterally at 100 msec; it was followed by a positive wave which peaked at 210 msec. This negativity was noted at 260 msec on the left and 270 msec on the right, whi1le P2 (the second positive wave) was seen at 305 msec on the left and 320 msec on the right. Corresponding negative, N3, was slower on the right- 315 as compared to 320 msec. By the appearance of the final positive wave relative synchrony of the evoked response returned. Figure 3 demonstrates the averaged auditory evoked response of our patient compared with the evoked response of a control subject. AUDITORY EVOKED RESPONSE left temporal, bipolar /"" ./
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Figure 4 is a diagrammatic comparison of right-sided and left sided evoked respons·es in our patient. In comparing these responses to the studies in p;ormal individuaLs in our laboratory, one sees that the responses recorded from both left and right side are slower and
439
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of sma11er amplitude than normal. In addition, however, there is a difference noted between right and left side in that the later com ponents of the evoked response on the dght lay behind that on the left. Though the changes are small, they suggest that there is a delay in processing of auditory stimuli bilaterally, and in addition the right side is more affected. This delay .i:s even more significant in light of Cohn',s observations (1971) that click sdmuli in normal subjects generate shorter Latency and higher amplitude potentials in the right hemisphere as compared to that on the left.
Summary of major findings This is a case of a normaLly intelligent, well-educated right-handed 58 year-old man who developed, acutely, major disturbances of centra:! auditory processing. Initi:aHy he had signs of ,a posterior aphasia with predominant features of word deafness, auditory neglect, and defective recognition of the meaning of non-verbad sounds. There was a raP'id evolution; within days the word deafness disappeared and the major defects which remained were in sound locaLization and sound·meaning vecognition. The left sided auditory neglect was persistent. DetaiJ.ed testing of the capacity of his auditory system revealed extinction of the left ea-r with dichotic stimulation; strikingly impaired ability to recognize the meaning of non-verbail sounds despite an intact comprehens1on of words, phrases, and sentences; impaired
440
M. L. AJbert, R. Sparks, T. von Stockert and D. Sax
perception of pitch, loudness, rhythm, a:nd time; abnorma:Ny delayed and reduced cortical auditory evoked potential wave forms, worse on the right than on the left. Delayed auditory feedback produced a marked exaggeration of the patient's mildly abnormal speech produc tion. Accelerated auditory feedback produced a slightly increased rate of speaking, but no change in prosody. A left posterior sylwan lesion wars demonstr·ated by brain scan. Repeated e!lectroencephaJlographic studies indicated a persistent struc tural ahnovmality in the right parieto-temporo-ocdpiva:l region.
DISCUSSION
Auditory agnosia
Although the neurological literature contains many references to auditory agnosia, this term has not been used in a consistent manner. As Vignolo (1969) indicates, "this expression has sometimes been extended to encompass defective identification of alllcinds of auditory material, including speech and music." We use the term to refer to an impaired ab.ililty to recognize the meaning of non-verbal sounds, in the presence of an intact ability to recognize the meaning of spoken words. The nature of auditory agnosia is clea.tily demonstrated in this case. At one stage in the evolution of this patient's disease, he could neither name nor point to the. sound-producing object when its appropriate sound was presented. However, he could name the object when it was shown to him and he could select the object on a multiple choice task when its name was given. His :hearing was relatively intact, as shown by audiometric studies. His auditory comprehension of language was inmct, as shown by the aphasia evad.ruation. His general level of intelHgence was normal, as shown by the WAIS. What was not intact was the ability to associate a perceived non-verbal sound with its meaning. This is not simply an inabillity to assooiate a perceived meaningful sound with its name. Rather, it is an inability to establish the correspondence between the perceived sound and ivs sensory or motor associatlions. Since the patient wa:s able to attach meaning to heard word-sounds but was not able to attach meaning to heard non-verbal sounds, one may postulate that the brain is organized to process differenti.ally the linguistic and non-linguistic aspects of acoustic inputs. Yamadori and
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Albert (1972) have suggested that there may be a "step-wise series of neuropsychological processes dealing differentiallly with the percep tion of mean~ngful non-word sounds and word-sounds, each of which has word-meaning attached at a different level." AdditJion'lrl support for this position comes ~rom a recent srudy designed to test auditory cortical evoked potentials during speech perception. In their report, Wood, Goff and Day ( 1971) demonstrared that "different neural events occur in the ·left hemisphere during ana:lysis of linguistic versus non~linguistJic paramete:t'ls of the same acoustic sigrml." Thus, the case reported here may represent a clinical support of the experiment&! position stating that there are two central auditory processing mecha nisms, Linguistic and non~linguistic. The folJowing tentative interpretation is proposed to explain the functionaJ neuroJogical mechanisms underlying audhory agnosi:a. Acoustic non-verbal impulses in normal individua:ls reach the temporal lobes of both hemispheres for initial central auditory perceptua:l processing (Albert, 1972). The partially processed impulses from the mght hemisphere are transmitted via the corpus caillosum to the left hemisphere where they interact with acoustic impuhes which have a:lready been pa.vtiaJly processed in the left hemisphere. After this interaction in the left hemisphere, the next step is that of "establishing correspondences" (Chalfant and Scheffelin, 1969). This involves the setting up of reciprocal associations between the acoustic impuJses and other characteristics of objects and events as they are stored in the association areas of other sensory SY'stems in the left hemisphere. In this stage meaning would be attached to the perceived sounds. This norma1 flow of acoustic impulses from an inhial central auditory pl'IOCessing in both hemispheres to an interaotion of these processed impulses in the left hemisphere involves a certain discrete time factor in n011mal individuals. In this patient there is evidence from the cortical evoked potentials that the central auditory processing is delayed. in both hemispheres, more in the right than the left. This delay results in an asynchrony of interaction of the auditory impulses i:n the left hemisphere. It may be posrulated that this asynchrony interferes with the normal process of establishing correspondences or making necessary associations. Thus non-verbal auditory inputs may be heard but not undersrood. Since verba:l auditory inputs are treated aJmost exolusively in the left hemisphere (Albert et al., 1971; Kimura, 1961), and since
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the linguistic aspects of an acoustic input may be treated separately from the non-Hnguisitc aspects (Wood et al., 1971), the auditory verbal inputs would not be affected by the asynchronous arrival of the non~Hnguistic acoustic impulses from the right hemisphere. Linguistic analysis could thus remain intact. The above discussion proposes that the basis for the defective auditory processing in this case is an associative (or semantic) type of agnosia. An alternative interpretation may ail:so be considered: our patient may have had an apperceptive (or discriminative) type of agnosia . .Mthough he couM hear pure tones and although he couM disaiminate auditory verbal inputs, he may have had an inability in discriminating the acoustic structure of the heard non-verbal sounds. Support for this alternative interpretation is the patient's poor performance on the subtests of the Seashore Test. In either case, whether his agnosia was of the associative or the apperceptive type, the major conclusion remains unchallenged: there may be two separate centrail auditory processing mechanisms, one dealing with linguistic input's, the other dealing with non-linguistic inputs. Auditory neglect
The patient demonstrated persistent left-sided inattention to auditory stimurli. The Spar~s et al. model (1970) permits two possible explanations for left-ear extinction of verbal signa1ls in this patient with bilateral cortical damage. One possibility is a disruptive lesion in the auditory areas of the right temporal lobe. A second possibility is that acoustic impulses are unimpaired in the right hemisphere but are disrupted at their point of reception in the auditory area of the left temporal! lobe after crossing the corpus callosum. Explanation for left ear neglect of melodies would be difficult using the same model unless we p;esume that recognition of a familiar melody is enhanced by the linguistic component involved in the name of a song. Heitlman and Vailenstein ( 1972) have proposed that the pathologi cal locus responsible for auditory neglect 1n man is usually the inferior parietal lobe of the non-dominant hemisphere. Bender and Diamond (1965) have spoken out against attempts to localize precisely the portion of the cerebrum responsible for abnormalities of perceptual interactions such as neglect. In the case reported here there is evidence of bHateral parieto-temporal pathology; the pathological locus respon sible for the auditory neglect cannot be stated with certainty.
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SUMMARY
We have evaluated at length an individual who had as a major neurological defect an impaired ability to recognize the nature of heard non-verbal sounds, that is, auditory agnosia. Wood et al. (1971) have demonstrated that «different neural events occur in the left hemisphere during analysis of linguistic vs non-linguistic parameters of the same acoustic signal». This case provides additional clinical support for the theoretical position that there may be two central auditory processing mechanisms, one treating linguistic inputs and the other non-linguistic inputs.
REFERENCES
ALBERT, M. (1972) Aspects de la comprehension auditive du langage, "Langages," 7, 37-51. - , GoLDBLUM, M., HECAEN, H., and BENSON, D. (1971) Mechanism of auditory comprehension. II. Cerebral dominance, Trans ANA, 96, 132-135. BENDER, M., and DIAMOND, S. (1965) An analysis of auditory perceptual defects with observations on the localization of dysfunction, "Brain," 88, 675-685. CHALFANT, J., and SCHEFFELIN, M. (1969) Central processing dysfunction in children: A review of research, USPHS..HEW-NINDS Monograph 9, 1969. CoHN, R. (1971) Differential cerebral dominance to noise and verbal stimuli, Trans ANA, 96, 129-132. DAVIDSON, G. (1958) Sidetone delay and reading rate, articulation, and pitch, "J. Speech Hear. Res.," 2, 266-270. EDGREN, J. C. (1895) Amusie (musikalische Aphasie), "Dtsch. Z. Nervenheilk," 6, 1-28. FAGLIONI, P., SPINNLER, H., and VIGNOLO L. (1969) Contrasting behavior of right and left hemisphere-damaged patients on a discriminative and a semantic task of auditory recognition, "Cortex," 5, 366-389. GooDGLASS, H., and KAPLAN, E. (1972) Assessment of Aphasia and Related Disorders, Lea and Febiger, Philadelphia. HEILMAN, K., and VALENSTEIN, E. (1972) Auditory neglect in man, "Arch. Neural.," 26, 32-35. KIMURA, D. (1961) Cerebral dominance and the perception of verbal stimuli, "Canad. J. Psychol.," 15, 166-171. LIEPMANN, H. (1898) Bin Fall von reiner Worttaubheit, in Psychiatrische Abhandlungen, ed. by C. Wernicke, Schletter, Breslau. SPARKS, R., GooDGLAss, H., and NICKEL, B. (1970) Ipsilateral versus contralateral extinction in dichotic listening resulting from hemisphere lesions, "Cortex," 6, 249-260. SPINNLER, H., and VIGNOLO, L. (1966) Impaired recognition of meaningful sounds in aphasia, "Cortex," 2, 337-348. VIGNOLO, L. (1969) Auditory agnosia: A review and report of recent evidence, in Contributions to Clinical Neuropsychology, ed. by A. L. Benton, Aldine, Chicago. WooD, C., GoFF, W., and DAY, R. (1971) Auditory evoked potentials during speech perception, "Science," 173, 1248-1251. YAMADORI, A., and ALBERT, M. (1972) Word category aphasia. Paper presented at the American Academy of Neurology, April 29.
Martin L. Albert, M.D., Robert Sparks, M.A., Theodor von Stockert, M.D., Daniel Sax, M.D., Aphasia Research Section and Clinical Neurophysiology Section, Department of Neurology, Boston Veterans Administration Hospital, !50 South Huntington Avenue, Boston, Massachusetts 02130.
Auditory agnosia is a generahly accepted name applied to the clinical condition of disturbed capacity to recognize the nature of heard non-verbal sounds. Cases describing this condition, usually in combination with other auditory perceptua1 defects, have appeared in the neurologka:l literature ·since the Latter part of the nineteenth century (Edgren, 1895; Liepmann, 1898). However, this syndrome is rare, and its underlying neurological mechanisms are poorly undevstood. Recent system~tic attempt)s to clarify these mechanisms have demonstrated cont)radictory results (Spinnler and V.ignolo, 1966; Faglioni, Spinnler and Vignolo, 1969; Albert, Goldblum, Hecaen and Benson, 1971). Recently, we hav·e had the opportunity to evaluate at length an individual who had a~s a major neurological disturbance an impaired capacity to recognize the nature of heard non-verbal sounds. Techniques of testing, including, among other tests, accelerated and delayed audioory feed-back, presentation of dichotic stimuli, and auditory evoked corticad responses have yielded resuhs which aid in the interpretation of the mechanisms underlying this disorder. CASE REPORT
A 58-year-dld male right-handed self-employed leather goods designer was admitted to the Aphasia Research Section of the Boston 1 Some of the work reported here was supported by Public Health Service Grant NS-06209 to the Boston University School of Medicine.
428
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
V'et:erans Admin±stration Hospirral on May 25, 1971, for ev,aluation of auditory perceptual defecus. On May 20, 1971 the following sequence of events had occurred. While he was working in his leather goods shop his speech suddenly became garbled. He then slumped to the floor, hitting the back of his head. He rose immediately and pointed to his ears. He then turned off the ~lectridty for the machinery and asked a co-worker if the machinery had been turned off. He left his shop, went to his car, started the engine. However, he could not be sure if the engine was on. He continued to try to start the engine which was, indeed, running a:nd finahly drove home. By the t,ime he reached home his speech was incomprehensible. Because of his bizarre behavior, his wife drove him to a near"by hospital. The admitting physician thought the patient had suffered a stroke and had him sent immediat:ely to the Neurology Service of the Boston Veterans Administration Hospital. Pertinent highlights of the admission evaluation included a description of "inappropriate gesturing and jargon-like speech." What was considered confusion was the patient's attempt to wvite with the eraser end of a pencil. Peripheral hearing "seemed to be intact ". A brief language examination demonstrated inappropriate responses to questions but, in general, "... he seemed to comprehend." He could fallow written commands and he "copied well." The remainder of the neurological examination was within normal limits. Among the initial diagnostic considerations was that of "conversion hysteria." During the next few days his condition rapidly evolved. It became clear that he had a continuing deficit of auditory processing, and he was transferred to the Aphasia Research Seccion for further evaluation. Past medical a:nd social history are pertinent. The patient was born in a small town in Rusrsi,a. His family left Russia when he was about 8 yearrs old an.d travelled for four years through Europe, then Cuba, ,and fina1ly the United States . .A:s a 'result, the patient speaks Yiddish as well as English, and has some knowledge of Russian, Ukran>ian, Polish, German, and Spanish. He graduated from college in the United States and was a high-school teacher for 19 years until two years ago. Since then he has worked as a self-employed designer of leather goods. In 1968 he had an inguinal he.vniorrhaphy. Immediately following this operation he discovered that he could not hear as well as previously, especially with his left ear. Although he had always used his left ear for listening on the telephone, he had now started using
Auditory agnosia
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his right ear. In the years following 1968 he had seven admissions to a phychiatric hospital with di'agnoses of depressive reaction and acute anxiety reactions. He did not receive electro-convu[sive therapy.
Physical evaluation The neurologicrul examination showed a short, slender, hyperactive, middle-aged man. He was oriented to time, place, and person. Recent and remote memory were intact. Blood pressure was 130/80 in hoth arms. Corrected visual acuity was 20/20 in hoth eyes. Visual fieild testing on the Goldman perimeter revealed no visual field defect. However, extinction of visual stimuli from the left homonymous half-field was present with double simultaneous stimulation. Cranial nerves were otherwise intact except for the auditory nerves. A description of examination of auditory pathways is included below. Reflexes were slightly exaggerated on the right side. No Babinski respoll!se was elicited. Motor and cerebehlar function were normal. Somesthetic sensation was normal and there was no somesthetic extinction to double simU'ltaneous stimulation. Repeated electroencephalography demonstrated persistent and abnormal theta activity from the right parieto-temporo-occipital deviations. Radioisotope brain scanning demonstrated a left posterior sylvian lesion. This evidence, therefore, is suggestive of bilateral posterior corticaJ lesions.
PROCEDURE
Study of this patient included examination for aphasia, audiological examination, testJs for sound localization, dichotic signals tests, recognition of non-verbail sounds and poplllla:r songs, parts of the Seashore Measures of Musical Talents, testing of his ability to receive and send Morse code because of a pre-morbid proficiency as a "ham" radio operator, and an examination for auditory evoked cortical 1Cesponse. Other tests concerned with manipulation of side-tone in auditory feed-hack and a test involving auditory masking were used to study their effect upon the patient's prosody of speech and frequency of paraphasia. These tests included delayed and accelerated feed-back, and excessive white noise masking.
430
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
Aphasia examination On initial detai[ed language evaluation on May 25, 1971 the following characteristics were observed. Spontaneous speech was fluent with many verba!l and phonemic paraphasias and frequent attempts at self-correction. Naming was correct about 80% of the time, and naming errors involved predominantly verbal paraphasias. Comprehension of spoken language was moderately impaired. His understanding of sentences was better than that for single words. His repetition was grossly impaired. Serial speech was better than repetition or spontaneous speech, but was not normal. Writing was paragraphic with both hands. Reading aloud was poor and demonstrated errors simi1lar to thos•e in his spontaneous speech. Reading comprehension was good. Related corticad function testing showed essentially normal results for right-1left orientation, spatiail orientation, finger recognition, color recognition, and vi•sua,l object recognition. Singing was poor, both words and melody. Gailcu1ating ability was impaired. The over~a11 impression was of a predominantly posterior type of aphasia. Repeat language evarluation on June 10, 1971 using the Boston Diagnostic Aphasia Examination (Goodglass and Kaplan, 1972) showed considerable improvement. The patient's auditory compre hension was now only minimally impaired. Comprehension of isola ted words was almost completely normal. Sub-test scores showed minor errors in both body-parts identification and compliance with the most complex multi-part commands. The patient's speech output continued to show some paraphasias, but without signifi·cant limit·ations on his ability to communicate. Articu1lation and grammatical structure were normal with an average phrase length of six or seven words. The paraphasias were predominanuly phonemic in quaHty with near-miss approximations to the target words. This on:ly moderately impaired his performance on such sub-tests as responsive speech, confrontatlion naming, body-part naming, and oral reading. He was frequently self-critica!l of Ms errors and often eflident at voluntary self-correction. Repetition of words and high-probability phmses was mildly impaired by phonemic paraphasia. Repedt,ion of low-probability phrases was more impaired. His speech output had a dysprosody which cou[d best be characterized as dysrythmic. Phrases were rapidly delivered but with frequent elongation of vowel sounds. Each phrase wars followed by a
Auditory agnosia
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pause before the next burst of words. The over-a!Jtl impres·sion was of a rather explosive and loud type of speech similar to that sometimes observed with normal individual•s in reaction to delayed auditory feed-back. Throughout the period the patient was in the hospital he complained frequently about what he described as an echo-Hike quarlity of his own voice. He stated, "It's almost as if I hear my own voice [ater than I shoU!ld." Narrative writing (description of a picture) was within normal limit•s. Phonemic paragraphic errors appeared in writing single words to dictation but not in sentences. Ability to sing a familiar melody was severely impaired but this was apparently no wol'se than his pre-morbid deficiency. Duplication of tapped rhythms was severely impaired. Related cortical function examination showed moderately impaired abil.ity to draw to command, mildly impaired abiJ.ity to use arithmetic processes, and a more severe degree of impairment in clock-setting and duplication of block-designs. Memory for stick designs was norma[ and there was no evidence of finger agnosia. On the Wechsler Adult Intelligence Scale, performed on June 11, 1971, his scores were: Verbal121, Performance 101, Fu:ll Scale 113. Audiological examination
Hearing was tested with pure-tone audiometry using ISO standards. The first examination, performed on May 25, 1971, showed a significant bi!lateral sensori-neural loss of questionable re!liability due to what appeared to be a poor attention span, particularly when signal strength approached his thresholds. A second and third examination (June 3 and 15) demonstrated a less impaired hearing profile. The results of these two latter examinatJions were identical and their reliability was further confirmed by Bekesy audiometry. An averaging of thresholds at 500, 1000, and 2000 Hz produced an estimated ·speech reception threshold of 24 dB in the left ear and 20 dB in the right. Thresholds for the higher frequencies were more elevated. The SIS I test scores suggested some recruitment but only at 4000Hz. Of some interest was the patient's report that he heard all pure tone signals and accompanying contralateral narrow-band masking bilatarally. Figure 1 shows his audiogram.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
432
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Sound localization The patient',s confusion concerning the source of auditory signals during the audiometric test led to a further examination for sound locailization ability. The resuhs were compared with those of a control group of aphasic male patients and a group of normal adult males. The patient was blind-folded and then exposed to a series of short bursts of noise generated by a Barany box. Twenty trials were given for each condition. The first condition tested for left-tight localization with the source of sound parallel to the left or right ear at a distance of two feet,. He was correct in localizing the source of the sound in on!ly 35% of the trials on the left and 55% on the right. By compadson, the mean score of a control group of six aphasic patients was 85% correct on the left and 80% correct the right. The mean score of a group of five normals was 90% correct on the left and 92% on the right. The patient's errors consisted of mis-location of the sound as coming from above or behind him. The second condition tested for above-below locailization on the right or left. In this case the Barany box was three feet above or below each ear. His acruracy under these conditions was further diminished. He continued to mis-locate the side of the source of sound and was
Auditory agnosia
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accurate for above-below choices onJy 5% of the time on the left and 15% on the right. By comparison, the aphasic control group produced a mean of 75% correct on the left and 85% on the right. The means for the normail control group were 92% on the left and 95% on the right. Dichotic signals
Results of dichotic tests for digits and words showed total extinc tion by the left ear for both digits and words. Correct repetition of monaural presentation of digits occurred in 80% of the items for each ear. Errors demonstrated residual! in-sphere paraphasic responses. Correct repetition of monaura!l presentation of words occurred in 70% of the items presented to the left ear and 80% on the right. Again, the same kind of errors occurred. Explanation for such left earr extinction in right-handed brain-damaged patients has been suggested by Sparks, Goodglass and Nickel (1970). Recognition of non-verbal sounds
One of the most striking auditory processing defects present in tMs patient was an impairment in his ability to recognize the meaning of non-verbal sounds. This deficit was tested using the technique described by Albert et aJ.. (1971 ). The subject is shown an array of 20 pictures of sound-producing objects, animals, or events. Ten sounds are presented by tape recorder. For each test sound the subject must indicate the picture which represents the natural source of the sound. For each sound there are pictures which represent: 1) the natural source of the sound, 2) the source of a sound in the same acoustic category as the sound presented, 3) the source of a sound in the same semantic category as the sound presented, and 4) the source of a sound which has no relationship to the sound presented. All pictures remain before the subject during the entire test procedure. This methodology is a modification of a similar test described by Vignola (1969). At the time of the first presentation of this test on May 20 the subject was able to name correctly aM the pictures when they were presented alone. He could aJ:so point correctly to aM of the pictures when the na:me was given. Exposure to the test itself showed a remarkable inability to identify the meaning of sounds. He failed nine out of ten trials. The one correct identification was a violin.
434
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
When hearing several cows mooing he said, "I hear a lot of noise but I dont't know what it is." When hearing a piano he said, "It sounds like music perhaps - very loud like a drum." His reaction to a dog barking was, "How come I can understand your voice but not these sounds? " A second presentation on June 4 showed only miM improvement with seven errors out of ten triak His correct identifications were all musical instruments - drums, a piano, and a violin. Again, his reaction were similar. When he heard a bird singing he said, "I hear the sound but I cant't seem to associate it with any of these pictures." Immediately after the above binaural presentation, the same ma terial was presented monaurally with contradatera~ white noise masking. He fahled to identify nine of ten items in each ear. Again, his correct identification was a violin. A third presentation on June 8 showed some improvement. He was corvect in identifying five of the ten items - three musical instruments and also the sound of birds singing and of a typewriter. On June 8 a second test, similar in principle to the first, used some of the pictures and recorded sounds from the test of meaningful sound recognitrion reported by SpinnJer and V,ignolo ( 1966 ). In this case; however, the patient is asked to select one of only four pictures as the correct source of the sound. This more limited choice selection is simpler and as a resudt perhaps less sensitive than the procedure described abov·e. Correct selection of the appropriate picture occurred 88% of the time. Verbal identification of the sound without pictures was correct ot11ly 25% of the time. In thfs instance there were interesting verhal misidentifications. For instance, the sound of a vidlin was identified as a musicllll instrument but "not in the string group." The neighing of a horse was identified as a bird. The rather good non-verbal sound recognition on this test is consistent with the improvement with tiffie on this task noted on the previously described test. Recognition of melodies
Free field presentation of such popular songs as "Yankee Doodle," "Happy Birthday," and "Sidewalks of New York" yielded the follow ing results: verbal identification, 30% correct; multiple-choice written titles, 100% correct. This would suggest that recognition of the melodies was normal!. The poor verbail identification score,
Auditory agnosia
435
parallel to the poor verbal performance in identifying non-verbal sounds on the Vignolo test, reflects a defect in retrieving the verbal components on both these tasks. Dichotically presented popular melodies
The same popular songs as used above were presented dichoticru1ly, one song delivered to the left ear simuhaneously with another to the right ear. Again, multiple-choice printed titles were presented. The results showed complete extinction by the left ear, consiJsvent with the left ear extinction of digits and words. Morse code and Seashore Measures of Musical Talent
The patient's long-standing interest and profidency in sending and receiving Morse code suggested that certain of the sub-tests of the Seashore Measures of Musical Talents might be of inverest. Results of the vests for pivch discrimination, loudness, rhythm and time ail showed scores at less tha:n the fifth percentile. Of specific interest, considering Ms avocationatl interest in Morse code, was the remarkable insensiti\nity to rhythm and time differences. The patient's pre-morbid skill in Morse code led to examination of his current aptitude. Accuracy in receiving s·ingle l·etters was 35% correct, receiving words was 0% correct. Sending individual letters was 58% correct, sending words was 90% correct. Although it is not unusual for proficiency of sending Morse code to be better than that for receiving, the discrepancy here is cons1dered significant and focuses attention, again, on his central auditory processing defects. Relaved to his poor performance on the rhythm-tapping part of the aphasia examination was the awkward dysrhythmic manner in which he managed the key while sending the code. Accelerated and delayed side-tone (Auditory feedback)
Examinations for the effects of accelerated and delayed side-tone were administered by Dr. Sheila Blumstein and Dr. Harold Goodglass. Davidson (1958) report's that in his normal popu1ation the acceleration of side-tone from a normatl delay of one mHlisecond to one-half a millisecond (vocal chords to cochlea) faciHvated the speech process by increasing the rate of oral reading a:nd increasing the extent and rate of inflection.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
436
Using the conditions of accelerated feedback s·et forth by Davidson, no observable change in the prosody of this patient's speech was noted. His speed of oral reading increased over that of normal conditions, using the same reading maberial, by 26%. This, however, is not significantly faster than the increased rate of 19% he achieved through practke effect under normal conditions. Figuve 2 shows the effect of practice on five trials and the effect of acceleration and delay of side tone. Practice Effect ec.
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Delayed side-tone (delayed auditory feedback) exaggerated the abnormal features characteristic of this patient's speech production. Nor:ma:1ly, his speech was produced with short staccato bursts of three words or more, his intonation pattern tended to end with a rising rather than falling pitch contour, vowels were lengthened and often distorted, and phonemic paraphasias commonly occurred. Under de layed side-tone all of these features were more pronounced. As the delay increased the padent's speech rhythm was characterized by short bursts of speech with increasingly longer pauses between bursts,
Auditory agnosia
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intonation patterns had more of a "sing-song" quality, vowels became increasingly lengthened and exaggerated, voice intensity rose, and production errors such as sound transpositions, repetition of syllables, etc. became more frequent. The effect of delay.ed side-tone on speed of reading was variable. Delay of one-sixth of a second showed a slight increase in the time required on the :first trial and approximately the same amount of increased speed on the second. Delay of one-:thhd of a second showed a uniform degree of slowed rate on both trials. Delay of two-thirds of a second again produced variability. Trial One showed some slowing, trial Two showed increase in speed. The variability might suggest some effect of delayed side-tone when compared with the steady rate of incr·ease in speed resulting from practice effect arlone. Effect of white noise masking
Ninety decibels of white noise masking were presented binaurally and the patient was asked to read test paragraphs. There was no apparent change in the prosody or frequency of paraphasic errors as a result of almost total masking of air-conduction auditory feedback. However, the patient stated that it was pleasant to get temporary l'eilief from the echo~like quality of his voice. Auditory evoked cortical response
Silver EEG needle electrodes with high impedance at low fre quencies were used in a:hl evoked response recordings. The electrode placements chosen corresponded to the international 10/20 system and used bipolar recordings £rom T3-T5 and T4-T6 posritions respec tively. A bipolar FP1-FP2 electrode was also used to rule out extraneous changes in the response 2° to eye movement. The evoked l'esponse was recorded on a Grass Model 610, 8 channel pdlygraph and then into an PM tape recorder with an audiomonitor channel. The gains were set accurately using a Fabritek averager. Low frequency filtering, 3Hz or less, and high frequency filtering, 300 Hz, were employed. The signals on the magnetic tape were then fed into a signal averager (Fabritek) which displayed the results on an X-Y plotner. The clock pulse generator drigitimer with a marker pulse triggered the stimulator which triggered both the polygraph and the stimulator that suppilied a olick at irregular intervals which varied between 2 and 4 duration.
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
438
In obtaining the auditory evoked potientials 256 tria:ls were averaged. The bipo1ar recording revealed a small evoked response of 2(.1.V which is partially obscured by muscle artifact. An initial negative deflection (N1) was recorded bilaterally at 100 msec; it was followed by a positive wave which peaked at 210 msec. This negativity was noted at 260 msec on the left and 270 msec on the right, whi1le P2 (the second positive wave) was seen at 305 msec on the left and 320 msec on the right. Corresponding negative, N3, was slower on the right- 315 as compared to 320 msec. By the appearance of the final positive wave relative synchrony of the evoked response returned. Figure 3 demonstrates the averaged auditory evoked response of our patient compared with the evoked response of a control subject. AUDITORY EVOKED RESPONSE left temporal, bipolar /"" ./
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Figure 4 is a diagrammatic comparison of right-sided and left sided evoked respons·es in our patient. In comparing these responses to the studies in p;ormal individuaLs in our laboratory, one sees that the responses recorded from both left and right side are slower and
439
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of sma11er amplitude than normal. In addition, however, there is a difference noted between right and left side in that the later com ponents of the evoked response on the dght lay behind that on the left. Though the changes are small, they suggest that there is a delay in processing of auditory stimuli bilaterally, and in addition the right side is more affected. This delay .i:s even more significant in light of Cohn',s observations (1971) that click sdmuli in normal subjects generate shorter Latency and higher amplitude potentials in the right hemisphere as compared to that on the left.
Summary of major findings This is a case of a normaLly intelligent, well-educated right-handed 58 year-old man who developed, acutely, major disturbances of centra:! auditory processing. Initi:aHy he had signs of ,a posterior aphasia with predominant features of word deafness, auditory neglect, and defective recognition of the meaning of non-verbad sounds. There was a raP'id evolution; within days the word deafness disappeared and the major defects which remained were in sound locaLization and sound·meaning vecognition. The left sided auditory neglect was persistent. DetaiJ.ed testing of the capacity of his auditory system revealed extinction of the left ea-r with dichotic stimulation; strikingly impaired ability to recognize the meaning of non-verbail sounds despite an intact comprehens1on of words, phrases, and sentences; impaired
440
M. L. AJbert, R. Sparks, T. von Stockert and D. Sax
perception of pitch, loudness, rhythm, a:nd time; abnorma:Ny delayed and reduced cortical auditory evoked potential wave forms, worse on the right than on the left. Delayed auditory feedback produced a marked exaggeration of the patient's mildly abnormal speech produc tion. Accelerated auditory feedback produced a slightly increased rate of speaking, but no change in prosody. A left posterior sylwan lesion wars demonstr·ated by brain scan. Repeated e!lectroencephaJlographic studies indicated a persistent struc tural ahnovmality in the right parieto-temporo-ocdpiva:l region.
DISCUSSION
Auditory agnosia
Although the neurological literature contains many references to auditory agnosia, this term has not been used in a consistent manner. As Vignolo (1969) indicates, "this expression has sometimes been extended to encompass defective identification of alllcinds of auditory material, including speech and music." We use the term to refer to an impaired ab.ililty to recognize the meaning of non-verbal sounds, in the presence of an intact ability to recognize the meaning of spoken words. The nature of auditory agnosia is clea.tily demonstrated in this case. At one stage in the evolution of this patient's disease, he could neither name nor point to the. sound-producing object when its appropriate sound was presented. However, he could name the object when it was shown to him and he could select the object on a multiple choice task when its name was given. His :hearing was relatively intact, as shown by audiometric studies. His auditory comprehension of language was inmct, as shown by the aphasia evad.ruation. His general level of intelHgence was normal, as shown by the WAIS. What was not intact was the ability to associate a perceived non-verbal sound with its meaning. This is not simply an inabillity to assooiate a perceived meaningful sound with its name. Rather, it is an inability to establish the correspondence between the perceived sound and ivs sensory or motor associatlions. Since the patient wa:s able to attach meaning to heard word-sounds but was not able to attach meaning to heard non-verbal sounds, one may postulate that the brain is organized to process differenti.ally the linguistic and non-linguistic aspects of acoustic inputs. Yamadori and
Auditory agnosia
441
Albert (1972) have suggested that there may be a "step-wise series of neuropsychological processes dealing differentiallly with the percep tion of mean~ngful non-word sounds and word-sounds, each of which has word-meaning attached at a different level." AdditJion'lrl support for this position comes ~rom a recent srudy designed to test auditory cortical evoked potentials during speech perception. In their report, Wood, Goff and Day ( 1971) demonstrared that "different neural events occur in the ·left hemisphere during ana:lysis of linguistic versus non~linguistJic paramete:t'ls of the same acoustic sigrml." Thus, the case reported here may represent a clinical support of the experiment&! position stating that there are two central auditory processing mecha nisms, Linguistic and non~linguistic. The folJowing tentative interpretation is proposed to explain the functionaJ neuroJogical mechanisms underlying audhory agnosi:a. Acoustic non-verbal impulses in normal individua:ls reach the temporal lobes of both hemispheres for initial central auditory perceptua:l processing (Albert, 1972). The partially processed impulses from the mght hemisphere are transmitted via the corpus caillosum to the left hemisphere where they interact with acoustic impuhes which have a:lready been pa.vtiaJly processed in the left hemisphere. After this interaction in the left hemisphere, the next step is that of "establishing correspondences" (Chalfant and Scheffelin, 1969). This involves the setting up of reciprocal associations between the acoustic impuJses and other characteristics of objects and events as they are stored in the association areas of other sensory SY'stems in the left hemisphere. In this stage meaning would be attached to the perceived sounds. This norma1 flow of acoustic impulses from an inhial central auditory pl'IOCessing in both hemispheres to an interaotion of these processed impulses in the left hemisphere involves a certain discrete time factor in n011mal individuals. In this patient there is evidence from the cortical evoked potentials that the central auditory processing is delayed. in both hemispheres, more in the right than the left. This delay results in an asynchrony of interaction of the auditory impulses i:n the left hemisphere. It may be posrulated that this asynchrony interferes with the normal process of establishing correspondences or making necessary associations. Thus non-verbal auditory inputs may be heard but not undersrood. Since verba:l auditory inputs are treated aJmost exolusively in the left hemisphere (Albert et al., 1971; Kimura, 1961), and since
442
M. L. Albert, R. Sparks, T. von Stockert and D. Sax
the linguistic aspects of an acoustic input may be treated separately from the non-Hnguisitc aspects (Wood et al., 1971), the auditory verbal inputs would not be affected by the asynchronous arrival of the non~Hnguistic acoustic impulses from the right hemisphere. Linguistic analysis could thus remain intact. The above discussion proposes that the basis for the defective auditory processing in this case is an associative (or semantic) type of agnosia. An alternative interpretation may ail:so be considered: our patient may have had an apperceptive (or discriminative) type of agnosia . .Mthough he couM hear pure tones and although he couM disaiminate auditory verbal inputs, he may have had an inability in discriminating the acoustic structure of the heard non-verbal sounds. Support for this alternative interpretation is the patient's poor performance on the subtests of the Seashore Test. In either case, whether his agnosia was of the associative or the apperceptive type, the major conclusion remains unchallenged: there may be two separate centrail auditory processing mechanisms, one dealing with linguistic input's, the other dealing with non-linguistic inputs. Auditory neglect
The patient demonstrated persistent left-sided inattention to auditory stimurli. The Spar~s et al. model (1970) permits two possible explanations for left-ear extinction of verbal signa1ls in this patient with bilateral cortical damage. One possibility is a disruptive lesion in the auditory areas of the right temporal lobe. A second possibility is that acoustic impulses are unimpaired in the right hemisphere but are disrupted at their point of reception in the auditory area of the left temporal! lobe after crossing the corpus callosum. Explanation for left ear neglect of melodies would be difficult using the same model unless we p;esume that recognition of a familiar melody is enhanced by the linguistic component involved in the name of a song. Heitlman and Vailenstein ( 1972) have proposed that the pathologi cal locus responsible for auditory neglect 1n man is usually the inferior parietal lobe of the non-dominant hemisphere. Bender and Diamond (1965) have spoken out against attempts to localize precisely the portion of the cerebrum responsible for abnormalities of perceptual interactions such as neglect. In the case reported here there is evidence of bHateral parieto-temporal pathology; the pathological locus respon sible for the auditory neglect cannot be stated with certainty.
Auditory agnosia
443
SUMMARY
We have evaluated at length an individual who had as a major neurological defect an impaired ability to recognize the nature of heard non-verbal sounds, that is, auditory agnosia. Wood et al. (1971) have demonstrated that «different neural events occur in the left hemisphere during analysis of linguistic vs non-linguistic parameters of the same acoustic signal». This case provides additional clinical support for the theoretical position that there may be two central auditory processing mechanisms, one treating linguistic inputs and the other non-linguistic inputs.
REFERENCES
ALBERT, M. (1972) Aspects de la comprehension auditive du langage, "Langages," 7, 37-51. - , GoLDBLUM, M., HECAEN, H., and BENSON, D. (1971) Mechanism of auditory comprehension. II. Cerebral dominance, Trans ANA, 96, 132-135. BENDER, M., and DIAMOND, S. (1965) An analysis of auditory perceptual defects with observations on the localization of dysfunction, "Brain," 88, 675-685. CHALFANT, J., and SCHEFFELIN, M. (1969) Central processing dysfunction in children: A review of research, USPHS..HEW-NINDS Monograph 9, 1969. CoHN, R. (1971) Differential cerebral dominance to noise and verbal stimuli, Trans ANA, 96, 129-132. DAVIDSON, G. (1958) Sidetone delay and reading rate, articulation, and pitch, "J. Speech Hear. Res.," 2, 266-270. EDGREN, J. C. (1895) Amusie (musikalische Aphasie), "Dtsch. Z. Nervenheilk," 6, 1-28. FAGLIONI, P., SPINNLER, H., and VIGNOLO L. (1969) Contrasting behavior of right and left hemisphere-damaged patients on a discriminative and a semantic task of auditory recognition, "Cortex," 5, 366-389. GooDGLASS, H., and KAPLAN, E. (1972) Assessment of Aphasia and Related Disorders, Lea and Febiger, Philadelphia. HEILMAN, K., and VALENSTEIN, E. (1972) Auditory neglect in man, "Arch. Neural.," 26, 32-35. KIMURA, D. (1961) Cerebral dominance and the perception of verbal stimuli, "Canad. J. Psychol.," 15, 166-171. LIEPMANN, H. (1898) Bin Fall von reiner Worttaubheit, in Psychiatrische Abhandlungen, ed. by C. Wernicke, Schletter, Breslau. SPARKS, R., GooDGLAss, H., and NICKEL, B. (1970) Ipsilateral versus contralateral extinction in dichotic listening resulting from hemisphere lesions, "Cortex," 6, 249-260. SPINNLER, H., and VIGNOLO, L. (1966) Impaired recognition of meaningful sounds in aphasia, "Cortex," 2, 337-348. VIGNOLO, L. (1969) Auditory agnosia: A review and report of recent evidence, in Contributions to Clinical Neuropsychology, ed. by A. L. Benton, Aldine, Chicago. WooD, C., GoFF, W., and DAY, R. (1971) Auditory evoked potentials during speech perception, "Science," 173, 1248-1251. YAMADORI, A., and ALBERT, M. (1972) Word category aphasia. Paper presented at the American Academy of Neurology, April 29.
Martin L. Albert, M.D., Robert Sparks, M.A., Theodor von Stockert, M.D., Daniel Sax, M.D., Aphasia Research Section and Clinical Neurophysiology Section, Department of Neurology, Boston Veterans Administration Hospital, !50 South Huntington Avenue, Boston, Massachusetts 02130.