Schizophrenic feature recognition deficits are independent of task criterion

Sd~ixphrenitr Rmwrch, 7 ( 1992) 185%189 I(? 1992 Elsevier Science Publishers B.V. All rights reserved

SCHIZO

185 0920-9964;‘92;$05.00

00221

Schizophrenic

feature recognition deficits are independent criterion B.D. Schwartz,

Tul~tw CJtzivcwit~~ Mdcd (Received

W.J.

Evans,

F. Sautter

Center rmri Vercrm

IO July 1991: revision

received

and

Atlt?rinistrrrtiotl, NW

I I November

D.K.

Winstead

Orlems,

1991: accepted

of task

LA 70112, U.S. A

21 November

1991)

The present study determined the minimal exposure time (i.e., critical stimulus duration (CSD) necessary for feature registration and recognition by normals and chronic schizophrenics. Our interest was whether the longer exposure times required by schizophrenics than by normals could be attributed to an inability of schizophrenics to maintain attention when the task criteria were stringent as opposed to ‘loose’. The present findings support previous findings of impaired feature recognition by chronic schizophrenics. Chronic schizophrenics’ and normals’ CSDs were not affected by task criterion. The consistent performance by these groups on the ‘loose’ and ‘rigid’ task criteria suggest that if attentional lapses occur then they are as likely to occur for chronic schizophrenics as for normals and they are independent of the task’s criterion. It is concluded that impaired feature registration for chronic schizophrenics is a consequence of a deficit at the earliest stage of encoding. K<,j,Itwds; Critical stimulus duration:

Encoding

deficit; (Schizophrenia)

INTRODUCTION

Schizophrenics have a dysfunction during the first several hundred milliseconds of information processing. (Galloway, 1970; McGhie and Chapman, 1961; Miller, et al., 1979; Saccuzzo and Braff, 1981; Spring and Zubin, 1978; Yates, 1966; Schwartz et al., 1983; Green and Walker, 1986; Green and Walker, 1984; Nuechterlein and Dawson, 1984; Saccuzzo and Schubert, 198 I; Storonko and Woods, 1978; Asarnow et al., 1983; Balogh and Merritt, 1987). It has been hypothesized that deficits in visual recognition, faulty stimulus registration, and irregularities in the representation of features in the attentional trace might be ascribed to a deficit occurring at the earliest phase of encoding. To establish the extent of the early information Corrc,spon~k~~nc,c10: B.D. Schwartz, Department of Psychiatry and Neurology. 1430 Tulane Avenue, Tulane University Medical Center. New Orleans. LA 70112, U.S.A.

processing deficit in schizophrenics, a ‘low load’ task assists in circumventing possible confounds associated with later cognitive processing components. The encoding of very familiar letter or number characters is ‘low load’ and usually considered automatic. The Critical Stimulus Duration (‘CSD’) procedure can be used as a stand alone task or as a component of psychophysical paradigms (i.e., Backward Masking). It is used by many investigators as a means to minimize subject variability associated with initial visual input factors (Brody et al., 1980; Braff, 1981; Braff and Saccuzzo, 1981, 1982, 1985; Saccuzzo and Braff, 198 I, 1982; Saccuzzo et al., 1982, 1984; Merritt and Balogh, 1984; Balogh and Merritt, 1985; Merritt et al., 1986; Weiner et al., 1990). The CSD procedure obtains a minimal target exposure duration required to meet criterion. Typically, the CSD is the duration that meets a criterion of seven consecutive correct target identifications. This is a rigid response criterion that may overestimate the encoding deficit of

186 ‘;i : E

110 100

T

0 I

CONTROL SCHIZOPHRENIC

70

T

PERCENT

7 CONSECUTIVE CRITERIA

Fig. I. Critical stimulus duration required for target recognition as a function of ‘rigid’ (i.e., seven consecutive correct identifications) and ‘loose’ (i.e., 70% correct identifications) criteria.

schizophrenic spectrum individuals. For example, subjects could be identifying the targets quite well, but through a lapse of attention on a trial respond with an incorrect identification. Consequently, the target’s duration will be increased for the next string of seven trials. Thus, a rigid response criterion might serve to confound encoding deficits with attentional deficits. Nuechterlein and Dawson (1985) also suggest that task difficulty may contribute to poor performance. As an example, Nuechterlein and Dawson (1985) indicate that longer CSD’s associated with identification of a single letter from an array of sixteen letters (Merritt and Balogh, 1985) likely reflects the demand for more extensive or less efficient processing to identify the target letter. Although the above suggests that task difficulty and task response criterion have an impact on a schizophrenic spectrum individual’s performance, it remains to be determined empirically whether schizophrenic early registration deficiencies are associated with a disruption of either automatic or attentional processes. The purpose of the present study was to evaluate the efficiency of initial registration of visual information associated with automatic processes by schizophrenics and whether schizophrenics’ CSD threshold varies as a function of attentional demands (i.e., ‘loose’ or ‘rigid’ task criterion).

PROCEDURE

AND

METHODS

Subjects

Thirty-one subjects participated in the present study. Patients were volunteers from the inpatient

service of the Veterans Administration Medical Center, Tulane Medical Center Hospital, and Charity Hospital, New Orleans. Normal controls were employees from these institutions who were well matched sociodemographically. There were thirteen normal controls and eighteen chronic schizophrenics. For inclusion in the study, the patients met the following criteria: (I) research diagnostic criteria for schizophrenia (Spitzer et al., 1978); (2) between 18 and 40 years of age; (3) normal intelligence (IQ equal or greater than 80) as measured by the Shipley Institute of Living Scale; (4) no history of electroconvulsive treatment; (5) no significant history of head trauma; (6) normal or corrected to normal vision (i.e., at least 20/30) as assessed by Snelling Acuity. Stimuli and apparatus

The stimuli were presented in a three field Scientific Prototype N 1000/A tachistoscope. The subjects viewed the targets from a distance of 129 cm. Target stimuli, ‘A’ and ‘T’, were presented randomly. The test stimuli were formed by Letraset 26-24-CLN letters mounted on white unlined 5 x 7inch stimulus cards. The letters subtended a visual angle of approximately 0.21” and appeared in the center of the visual field. Luminance of the target stimulus was set at 16 foot-Lamberts. Luminance levels were measured at the eyepiece of the tachistoscope with a Tektronix (Model 516) photometer. All stimuli were viewed binocularly. Procedure

The subjects, after entering a dimly lighted room, were allowed sufficient time to dark adapt. They were then read a set of standardized instructions. The instructions indicated that the subjects were to look through the visor of the tachistoscope. On each trial, the subjects were to report verbally the appearance of an ‘A’ or ‘T’. They were then allowed practice trials until it was apparent that they were able to perform the task. Information processing efficiency was indexed by obtaining the CSD which was defined as the minimum time required for the initial registration of the target stimulus. The subjects were tested on the ‘loose’ and ‘rigid’ criteria. The loose criteria established the CSD as the minimal stimulus duration necessary for subjects to obtain seven out of ten correct identifications (i.e., 70%), while the rigid criteria required subjects

187

to obtain seven consecutive correct target identifications. A target stimulus duration starting point was established for each subject based on practice trials. The ‘A’ and ‘T’ were presented randomly for an equal number of times within each block of ten trials. The target duration for each block was increased or decreased by a millisecond until the CSD was obtained for each criterion. The order of presentation for criterion was counterbalanced between subjects with each subject obtaining a CSD on one criterion before proceeding to the second.

RESULTS

A Repeated Measures Analysis of Variance was performed on the data. Normal controls and chronic schizophrenics composed the subjects within groups (SS/GRP) component of the analysis with repeated measures performed upon the criterion component (70% versus seven consecutive correct target identifications). The dependent variable was the CSD. An analysis of variance performed on age did not reveal significant differences between the groups (p > 0.05). The mean ages were 35.4 for normal controls and 28.6 chronic schizophrenics. Age of the subjects also was used as a co-variate to assess whether age correlated with performance. Age did not correlate with performance (F= 0.41; df= 1,28; p=O.53). A significant main effect for CSD was obtained between chronic schizophrenics and normal controls (F= 5.66; df= 1,28; p=O.O2). A nonsignificant main effect for CSD was obtained between the ‘loose’ and ‘rigid’ criterion (F= 1.55; df = 1,29; p = 0.22). Also, a nonsignificant groups x criterion (‘loose’ versus ‘rigid’) effect was obtained (F= 1.55; df = 1,29; p = 0.22). Thus, CSDs did not significantly differ between subjects or groups as a function of criterion.

DISCUSSION

The finding from the present study offers support for a schizophrenic visual information processing deficit that occurs during the stage of stimulus

registration. The deficit is primarily associated with automatic processing of information. There are two types of processing that can take place. Automatic processing is a fast, parallel, fairly effortless process, that is not limited by short-term memory capacity, is not under direct subject control, and is responsible for performance of well-developed skilled behavior. In contrast, control processing is characterized as a slow, generally serial, effortful, capacity limited, subject regulated processing mode that must be used to deal with novel information. Since automatic processing circumvents higher cognitive processes as opposed to controlled processes, attentional demands are minimal. A physiological interpretation of automatic processing is that presentations of a very familiar visual stimulus channels activates neurophysiological visual required for registration of information (Jonides and Yantis, 1988; Yantis and Jonides, 1984). Consequently, the familiar stimuli used in the present study which required minimal processing indexed automatic processing assdciated primarily with stimulus registration. A possible factor that could contribute to the deficit in stimulus registration for chronic schizophrenics is a deficit in active, sustained, attention (Holzman et al, 1978). However, in the present study, the nonsignificant differences in performance between schizophrenics and normal controls on the ‘loose’ and ‘rigid’ response criterion (i.e. the repeated measure) suggest that if distraction occurred it was as likely to occur for chronic schizophrenics as for normals. The significantly longer CSD for chronic schizophrenics is consistent with previous reports of longer CSD for poor-prognosis nonparanoid schizophrenics (Saccuzzo and Brat?, 1981) paranoid and nonparanoid schizophrenics (Braff and Saccuzzo, 1985; Brody et al., 1980; and Saccuzzo et al., 1974) negative schizophrenic subtypes (Weiner et al., 1990) and process schizophrenics (Traupmann, 1975). Green and Walker (1984, 1986) findings indicate that positive and negative syndrome schizophrenics have different types of attentional and cognitive deficits. Negative symptom patients, whose profiles likely are similar to the chronic schizophrenic patients used in the present study, were observed to be less efficient in their early information processing than positive symptom patients. Positive schizophrenics are

188

more distractible and unable to maintain attention while negative symptom schizophrenics have poorer automatic processing ability. The backward masking literature indicates that the more chronic, poor prognoses schizophrenics are more likely to have abnormally long stimulus registration thresholds (Braff and Saccuzzo, 1985; Nuechterlein and Dawson, 1985). Weiner et al. (1990) found significantly impaired CSDs and backward masking performance for negative as opposed to positive schizophrenic patients suggesting that negative, chronic patients have a lower processing capacity at the earlier stage of sensory registration and/or they are less efficient processors. Future research designed to evaluate automatic processes and attentional components may benefit by evaluating negative and positive symptom schizophrenics as a function of chronicity to better determine the role for trait and state dependent components. Also relevant to our findings of a registration deficit for chronic schizophrenics is a proposal by DiLollo (1980) that automatic processing can be categorized into two successive phases of sensory coding, ‘recruiting’ and ‘interpreting’. During the recruiting phase stimuli configuration become encoded as features. The interpreting phase of sensory coding identifies and categorizes the information. This processing sequence culminates in the ability to make comparisons between the newly encoded stimuli and long-term memories. The recruiting and interpreting phases have different distinguishing characteristics, those associated primarily with the recruiting phase (e.g. masking by integration of contours and feature integration) are typically where deficits are identified for schizophrenics. Regardless of which sensory encoding phase (i.e. recruiting/interpretive) is less efficient in processing, the deficit in stimulus registration by some schizophrenics likely represents a deficient sensory coding mechanism that is responsible for the formation and identification of feature encoded stimuli.

REFERENCES

Asamow, R.F., Nuechterlein. K.H. Span of apprehension performance.

and Marder. S.R. (1983) neuropsychological func-

tioning, and indices of psychosis-proneness. J. Nervous Mcntal Dis., 171, 662-669. Balogh, D.W. and Merritt R.D. (1985) Susceptibility to Type A pattern masking among hypothetically psychosis-prone collcge students. J. Abnor. Psychol.. 94, 377-383. Balogh, D.W. and Merritt. R.D. (1987) Visual masking and the schizophrenia spectrum: interfacing clinical and experimental methods. Schizopr. Bull. 13. 679-698. Braff. D.L. (1981) Impaired speed of information processing in nonmedicated schizotypal patients. Schizophr. Bull., 7. 499-508. Brafl: D.L. and Saccuzzo. D.P. (1981) Information processing dysfunction in schizophrenia: a two-factor deficit theory. Am. J. Psychiatry. 138, 1051-1056. Braff, D.L. and Saccuzzo, D.P. (1982) Effect of antipsychotic medication on speed of information processing in schizophrcnit patients. Am. J. Psychiatry, 139, 1127-l 130. BraIT, D.L. and Saccuzzo, D.P. (1985) The time course of information-processing deficits in schizophrenia. Am. J. Psychiatry, 142. 170-174. Brody, D., Saccu770, D.P. and Braff, D.L. (1980) Information processing for masked and unmasked stimuli in schizophrenia and old age. J. Abnorm. Psychol. 89. 617-622. Galloway. E., III. (1970) Schizophrenia and interference. An analogy with a malfunctioning computer. Arch. Gen. Psychiatry. 22, 193-209. DiLollo. V. (1980) Temporal integration in visual memory. J. Exp. Psychol. 109, 75-97. Green, M. and Walker, E. (1984) Susceptibility to backward masking in schizophrenic patients with positive or negative symptoms. Am. J. Psychiatry. 141, 1273-1275. Green. M. and Walker, E. (1986) Symptom correlates of vulnerability to backward masking in schizophrenia. Am. J. Psychiatry. 143, 181-186. Holzman, P.S., Levy. D.L. and Proctor, L.R. (1978) The several qualities of attention in schizophrenia. In: Wynne, L.D., Cromwell, R.L. and Matthysse, S., eds, The Nature of Schizophrenia: New Approaches to Research and Treatment. New York: Wiley. pp. 295-306. Jonides, J. and Yantis, S. (1988) Uniqueness of abrupt visual onset in capturing attention. Percept. Psychophys.. 43, 346-354. McGhie, A. and Chapman. J. (1961) Disorders of attention and perception in early schizophrenia. Br. J. Med. Psychol. 34, 103-l 16. Merritt. R.D. and Balogh. D.W. (1984) The use of a backward masking paradigm to assess the visual information processing of schizotypics: a re-evaluation of Steronko and Woods. J. Nervous Mental Dis. 172, 216-224. Merritt, R.D., Balogh. D.W. and Lcvcnthal. D.B. (1986) The use of metacontrast and a pamcontrast procedure to assess the visual information processing of schizotypics. J. Abnorm. Psychol. 94. 74480. Miller. S., Saccuz70, D.P. and Braff. D.L. (1979) Information processing deficits in remitted schizophrenics. J. Abnorm. Psychol. 88. 446-449. Nuechterlcm, K.H. and Dawson, M.E. (1984) Information processing and attentional functioning in the developmental course of schizophrenic disorders. Schizophr. Bull. 10. 16OG203.

189 Nuechterlein, K.H. and Dawson, M.E. (1985) Increased stimulus duration: vulnerability or episodic indicator? Schizophr. Bull. I I, 3444346. Saccuzzo, D.P. and Braff, D.L. (1981) Early information processing deficits in schizophrenia. Arch. Gen. Psychiatry, 38, 175-179. Saccuzzo, D.P. and Braff, D.L. (1981) Early information processing deficits in schizophrenia: new findings using schizophrenic subgroups and manic controls. Arch. Gen. Psychiatry, 38, 175-179. Saccuzzo, D.P., Braff, D.L., Sprock, J. and Sudik, N. (1984) The schizophrenia spectrum: a study of the relationship among the Rorschach, MMPI, and visual backward masking. J. Clin. Psychol., 40, 1288-1294. Saccuzzo, D.P., Braff, D.L. and Sprock, J. (1982) The effect of mental retardation and schizophrenia on information processing. J. Nerv. Mental Dis. 170. 1022106. Saccuzzo, D.P., Hirt, M. and Spencer, T. (1974) Backward masking as a measure of attention in schizophrenia. J. Abnorm. Psychol. 83, 512-522. Saccuzzo, D.P. and Schubert, D. (1981) Backward masking as a measure of slow processing in schizophrenia spectrum disorders. J. Abnorm. Psychol. 90, 305-312. Schwartz, B.D., Winstead, D.K. and Adinoff, B. (1983) Tempo-

ral integration deficit in visual information processing by chronic schizophrenics. Biol. Psychiatry, 18, I3 1l-1320. Spitzer, R.L., Endicott, J. and Robins, E. (1978) Research diagnostic criteria. Arch. Gen. Psychiatry 35, 773-782. Spring, B.J. and Zubin, J. (1978) Attention and information processing as indicators of vulnerability to schizophrenic episodes. In L. Wynne, R.L. Cromwell, S. Matthysse (Eds.), The Nature of Schizophrenia: New Approaches to Research and Treatment. New York: Wiley, pp. 3666375. Steronko, R.J. and Woods, D.J. (1978) Impairment in early stages of visual information processing in nonpsychotic schizotypic individuals. J. Abnorm. Psychol. 87, 481-490. Traupmann, K.D. (1975) Effects of categorization and imagery on recognition and recall by process and reactive schizophrenics. J. Abnorm. Psychol. 84, 30773 14. Weiner, R.U., Opler. L.A., Kay, S.R. et al. (1990) Visual information processing in positive. mixed, and negative schizophrenic syndromes. J. Nerv. Mental Dis. I78 (IO), 616-626. Yantis. S. and Jonides, J. (1988) Abrupt visual onsets and selective attention: evidence from visual search. J. Exp. Psychol. IO, 601l621. Yates. A. (1966) Psychological deficit. Annu. Rev. Psychol., 17, 111-114.