The Role of the Temporal Lobes in Recognizing Visuospatial Materials: Remembering versus Knowing

35, 5–25 (1997) BR970902

BRAIN AND COGNITION ARTICLE NO.

The Role of the Temporal Lobes in Recognizing Visuospatial Materials: Remembering versus Knowing Teresa A. Blaxton and William H. Theodore National Institute of Neurological Disorders and Stroke, National Institutes of Health Recognition memory for abstract visuospatial designs was assessed in unilateral temporal lobe epilepsy (TLE) patients and normal controls using a remember/know recognition paradigm. Subjects assigned ‘‘remember’’ judgments to recognized items for which they could recall the study presentation, and ‘‘know’’ judgments to items recognized on the basis of familiarity without conscious recollection of the study episode. In Experiment 1 normal controls and left TLE patients gave more ‘‘know’’ than ‘‘remember’’ recognition judgments for visuospatial materials. Right TLE subjects, however, showed the opposite response pattern. Experiment 1a demonstrated that this dissociation between left and right temporal patients occurred in both presurgery and postsurgery patients. In Experiment 2 recognition was assessed following encoding conditions in which subjects answered questions about either the number of lines in the designs or the appropriateness of verbal labels for presented stimuli. The previous pattern of ‘‘know’’ and ‘‘remember’’ responses was replicated for all groups in the line count condition, but was reversed for normal controls in the label condition. These results are interpreted within a theoretical framework in which ‘‘remember’’ responses are based on the contribution of distinctiveness of individual items to recognition whereas ‘‘know’’ judgements reflect perceptual fluency.  1997 Academic Press

The notion that the left and right temporal lobes support memory for different types of materials in the human has been a widely held hypothesis among memory researchers. The first part of the hypothesis, that left temporal cortex subserves verbal memory, has been well established. Experiments conducted with unilateral temporal lobe epilepsy (TLE) patients have shown that lesions of the left mesial temporal lobe are associated with selective verbal memory deficits (e.g., Andrewes, Puce, & Bladin, 1990; Fedio & Mirsky, 1969; Meyer & Yates, 1955; Milner, 1967; Milner, Corkin, & Teuber, This work was supported by the Epilepsy Research Branch of the NINDS. Appreciation is expressed to Mark Wilson and James Carpenter for assistance in preparing stimulus materials and to Michael Tierney for help in testing subjects. The authors also thank Drs. John Gardiner and John Gabrieli for helpful comments on an earlier version of the manuscript. Address reprint requests to Teresa A. Blaxton, 1831 Abbotsford Drive, Vienna, VA 22182. 5 0278-2626/97 $25.00 Copyright  1997 by Academic Press All rights of reproduction in any form reserved.

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1968; Mungas, Ehlers, Walton, & McCutchen, 1985). As reviewed by Milner (1967, 1971), left temporal lesions result in impairment on such tasks as free recall of prose passages and paired associate learning of both auditorily and visually presented materials. The second half of the materials specificity hypothesis is that similar lesions in the right hemisphere produce memory deficits for nonverbal information. In support of this claim, some researchers have reported demonstrations of impaired perception and memory in right hemisphere TLE patients for stimuli that are difficult to describe with verbal labels such as visual designs and tonal stimuli (e.g., Andrewes et al., 1990; Jones-Gotman, 1986; Kimura, 1963; Shankweiler, 1966). Unfortunately, these memory deficits for nonverbal information in right temporal patients are sometimes elusive, especially in presurgical patients (e.g., Glowinski, 1973; Goldstein, Canavan, & Polkey, 1988; Mayeux, Brandt, Rosen, & Benson, 1980). As a result, there is now substantial uncertainty about both the theoretical question of the role of the temporal lobes in supporting visuospatial memory and the clinical issue of which types of tests might best be used to assess right temporal memory function (see also Barr, this volume). The experiments reported in this paper explore the utility of a recognition paradigm developed in the normal memory literature for characterization of memory for visuospatial materials in TLE patients. The remember/know recognition paradigm used in the present experiments grew out of a line of theoretical work suggesting that recognition memory is based on multiple components (e.g., Jacoby, 1983a,b; Jacoby & Dallas, 1981; Mandler, 1979, 1980, 1989). These components have been characterized in different ways using such dichotomies as recollection versus familiarity, integration versus elaboration, and conceptual versus perceptual processing. What has been common to all accounts is the claim that the components are distinct and that it is possible to devise experimental paradigms so as to assess these components separately. The remember/know recognition task, first suggested by Tulving (1985), and later developed more fully by Gardiner and his colleagues (e.g., Gardiner, 1988; Gardiner & Java, 1990, 1991, 1993; Gardiner & Parkin, 1990) has been used with this goal in mind. In this paradigm subjects study materials and then receive a yes/ no recognition test. For each item on the test to which a subject responds ‘‘yes’’, s/he is asked to make a further judgment. If the subject actually recollects the original presentation of the item on the earlier study list, a ‘‘remember’’ judgment is given. On the other hand, if the subject is sure that the item was previously presented but cannot consciously recall studying it, a ‘‘know’’ response is given. It has now been shown in several experiments that, given careful instructions, normal subjects can readily make these judgments and that the data obtained produce principled outcomes (see Gardiner & Java, 1993 and Rajaram & Roediger, in press, for reviews). For example, experiments examining the levels of processing effect have shown that the superior recognition for items processed to a semantic (deep) as compared to a phonemic (shal-

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low) level is due entirely to differences in frequency of ‘‘remember’’ judgments (Gardiner, 1988; Rajaram, 1993). The levels of processing manipulation produces no effect on ‘‘know’’ judgments. The same type of finding has been observed in other experimental paradigms including those investigating generation effects (Gardiner, 1988; Java, 1994), picture superiority effects (Rajaram, 1993), word frequency effects (Gardiner & Java, 1990), retention interval (Gardiner & Java, 1991), subjective vocalization versus silent reading (Gregg & Gardiner, 1994), divided/nondivided attention (Gardiner & Parkin, 1990), and the effects of aging on normal memory (Mantyla, 1993; Parkin & Walter, 1992). In all cases the superiority of recognition in one condition over another is mediated by differences in frequency of ‘‘remember’’ judgments across conditions. Evidence that ‘‘remember’’ and ‘‘know’’ responses may be manipulated independently is provided by demonstrations that other experimental variables affect the frequency of ‘‘know’’ responses or produce opposing effects in the frequency of the two judgments. These include more ‘‘know’’ judgments for nonwords in word/nonword recognition (Gardiner and Java, 1990), more ‘‘know’’ judgments for words studied and tested in the same perceptual format (Rajaram 1993), more ‘‘know’’ responses following maintenance rehearsal as opposed to more ‘‘remember’’ responses following elaborative rehearsal (Gardiner, Gawlick, & Richardson-Klavehn, 1994), an increase in ‘‘know’’ responses following masked presentation of targets immediately prior to recognition (Rajaram, 1993), and more ‘‘know’’ than ‘‘remember’’ judgments in recognizing unstructured passages of jazz music (Vernon, 1989). The theoretical interpretation that most completely accounts for all of these findings derives from observations that memory may be improved by enhancements of both distinctiveness of the original encoding episode (e.g., Hunt & McDaniel, 1993) and perceptual fluency (e.g., Luo, 1993). By this account, analysis of distinctive or salient attributes of an item during encoding results in the later subjective experience of conscious recollection, or ‘‘remembering’’. Further, conditions which enhance the fluency with which an item is processed give rise to later ‘‘know’’ judgments. ‘‘Remember’’ judgments are affected by variables which enhance the distinctiveness of studied items during encoding whereas ‘‘know’’ judgments more closely reflect a component of recognition that is based on perceptual fluency (Rajaram, 1996; Rajaram & Roediger, 1997). Thus, for example, the relatively greater distinctiveness afforded to items studied under semantic as compared to phonetic encoding conditions in levels of processing paradigms and to targets that are generated rather than read in generation tasks result in more ‘‘remember’’ responses on recognition tests. Conversely, processing of unstructured materials such as nonwords and jazz music involves perceptual analysis of surface features and the resulting perceptual fluency for studied items is reflected in a higher incidence of ‘‘know’’ responses to these items. The present set of studies was designed to assess several questions using

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the remember/know paradigm. First, since all of the studies reported with this paradigm thus far have employed verbal materials (with the exception of the jazz passages), it was of interest to evaluate the utility of this task in assessing recognition memory for nonverbal stimuli, namely visuospatial designs. If the distinctiveness/fluency framework is correct, this choice of study materials should elicit perceptual processing (at least in normal subjects), thus producing more ‘‘know’’ recognition judgments during recognition. The second question was whether the remember/know paradigm could be successfully used to study memory in neurologically impaired subjects, in this case TLE patients having unilateral mesial and lateral temporal damage. All of the studies reported thus far using remember/know recognition tests have been ones assessing memory function in normal young and elderly subjects. It is unknown whether the task might be used to study recognition in memory-impaired subjects having neurological damage. Assuming that TLE patients could perform the remember/know task, the third question addressed in these experiments concerned the patterns of performance that would be observed for left and right TLEs on this task— specifically whether this test would reveal reliable differences in left and right TLE patients in recognition memory for visuospatial designs. Differences in patterns of data obtained between left and right TLE patients should serve to extend the distinctiveness/fluency theoretical framework, possibly suggesting separable neurological substrates for distinctiveness processing and perceptual fluency. Moreover, should group differences in patterns of responses and not simply level of recognition be obtained, the data would bear upon a question often raised with regard to the remember/know paradigm, namely whether these judgments reflect differences in trace strength rather than differences among separable components of recognition memory. For instance it has been suggested that ‘‘remember’’ judgments might be given for items whose trace strength is relatively strong, whereas subjects might give more ‘‘know’’ judgments for weaker items. Findings of different patterns of ‘‘know’’ and ‘‘remember’’ responses for the two patient groups would argue against the trace strength argument.1 EXPERIMENT 1

Recognition memory was tested for nonnameable, novel visuospatial designs. These materials were designed to be unfamiliar and meaningless so that subjects’ analysis of these items during study should be largely perceptual. Following Rajaram’s analysis of processes underlying ‘‘remember’’ 1 The fact that both ‘‘know’’ and ‘‘remember’’ judgments can be modulated by experimental manipulations suggests that there is more mediating these recognition responses than simple trace strength or confidence level. Indeed experiments investigating this specific issue fail to support this type of account (Gardiner & Java, 1990; Parkin & Walter, 1992; Rajaram, 1993).

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and ‘‘know’’ judgments in recognition, it was predicted that recognition of these items should be largely based on perceptual fluency, rather than distinctiveness, resulting in more ‘‘know’’ than ‘‘remember’’ responses given on a recognition test for these materials for normal volunteers. Since left TLE patients typically do not show deficits in experiments assessing memory for visuospatial materials, it was expected that their pattern of ‘‘know’’ and ‘‘remember’’ judgments should look much like that of the normals. The right TLEs, on the other hand, were expected to show a different pattern of responses since damage to right temporal structures might result in visuospatial memory deficits that would be measurable by the remember/know task. Method Subjects. Three groups of female subjects were tested. These groups included 8 left hemisphere TLE patients, 8 right hemisphere TLE patients, and 16 normal controls matched for gender, age, and years of education. All subjects gave informed consent prior to the experiment in accordance with procedures approved by the NINDS. Normal control subjects were paid $25.00 each for their participation. TLE patients had either already had temporal lobectomies or had been admitted to the NIH Clinical Center as surgical candidates for the lobectomy procedure. Four presurgery and four postsurgery patients were tested in each of the left and right temporal groups. Extent of resection for the postsurgery left temporal patients included a mean of 1.6 cm of the anterior hippocampus (range 1.0 to 2.0), all of the amygdala and uncus, 4.25 cm of the superior temporal gyrus from the anterior pole of the temporal lobe (range 4.0 to 5.0), 5.6 cm of the middle temporal gyrus (range 5.0 to 7.5) and 6.6 cm of the inferior temporal gyrus (range 6.0 to 8.0). All postsurgery right temporal patients had undergone removal of 2.5 cm of the anterior hippocampus as well as the entire amygdala and uncus. Right temporal resections also included an average of 2.7 cm of the anterior portion of the superior temporal gyrus (range 1.0 to 4.5), 6.7 cm of the middle temporal gyrus (range 6.5 to 7.0) and 7.3 cm of the inferior temporal gyrus (range 7.0 to 8.0). Presurgery patients were classified as unilateral on the basis of data obtained from electroencephalography, positron emisson tomography, magnetic resonance imaging, and neuropsychological testing. Epileptogenic zones included lateral as well as mesial temporal lobe structures. Other relevant characteristics of the subject groups are presented in Table 1.2 Materials and design. A set of 70 abstract visuospatial designs similar to ones described elsewhere (Musen & Triesman, 1990) was created for use in the experiment. Examples of the designs are shown in Fig. 1. Stimuli were constructed within a 3 3 3 dot matrix in which each dot was assigned a number one through nine. Using a random number generator, six unique digits from one to nine were chosen and connected for each design with the restriction that a single connection not simultaneously traverse both a column and a row (e.g., a line would not be drawn connecting dot 2 directly to dot 9). The dot grids were omitted in the final designs which were created on a Macintosh IIc, printed on a HP LaserJet printer, and mounted on index cards for presentation.3 2 Based on findings that right temporal lesions produce memory deficits for spatial materials (e.g., Kimura, 1963; Milner, 1967, 1971), one might expect that WMS-R subtest scores for visual reproduction tasks would be lower for right TLEs than for left TLEs. As may be seen in Table 1, this is not the case for the NIH patients, nor is it necessarily the finding reported in other epilepsy centers (see Barr, this volume). 3 It has been suggested that verbal recording of visuospatial materials can obscure true memory effects, especially in patient studies (e.g., Milner & Teuber, 1968). In order to avoid

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TABLE 1 Characteristics of Subject Groups Tested in Experiment 1 Left TLEs

Right TLEs

Normal controls

N, Gender

8 Female

8 Female

16 Female

Age (Years)

Mean 31.3 Range 28–40

Mean 35.0 Range 25–49

Mean 31.0 Range 20–46

Education (Years)

Mean 13.1 Range 12–16

Mean 14.0 Range 12–16

Mean 14.2 Range 12–16

Pre-post surgery

4 Pre 4 Post

4 Pre 4 Post

WAIS-R

Mean 91.5 Range 82–101 Mean 89.1 Range 76–99 Mean 94.3 Range 82–105

Mean 96.5 Range 82–117 Mean 96.3 Range 81–119 Mean 97.5 Range 80–122

Mean 102.7 Range 77–133 Mean 17.9 Range 6–31 Mean 11.3 Range 4–21

Mean 120.9 Range 100–152 Mean 24.1 Range 15–34 Mean 19.2 Range 10–31

—

Visual reproduction I

Mean 26.0 Range 16–35

Mean 27.5 Range 19–35

—

Visual reproduction II

Mean 16.7 Range 10–23

Mean 23.3 Range 10–36

—

Verbal Performance WMS-R Logical memory I Logical memory II

— —

— —

— —

The 70 items were divided into two base lists of 35 designs each and each subject studied only one of these base lists. The index cards were shuffled prior to study so that each subject viewed the items in each base list in a different random order. All items were presented on the recognition test and the studied items for half of the subjects were the nonstudied items for the other half and vice versa. Procedure. Subjects were tested individually. They were told that they would see abstract visual designs presented one at a time on index cards and that each item would be shown for six seconds. Subjects were instructed that they would later be given a memory test, although the nature of the test was not specified. Immediately following study subjects were given the recognition test. The experimenter explained that half of the designs on the test had been presented earlier and that half were new. Subjects were instructed to circle ‘‘NO’’ if they believed that the item had not been studied. Subjects were further told to circle either ‘‘REMEMBER’’ or ‘‘KNOW’’ for those items they believed they had studied. Subjects were told to circle ‘‘REMEMBER’’ only if they actually recalled the event of studying the design during the study phase and to circle this problem, pilot testing was undertaken with the nonverbal stimuli chosen for the present experiments. Items that could readily be described verbally by pilot subjects were omitted from the stimulus set.

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FIG. 1. Examples of visuospatial designs used as study materials. ‘‘KNOW’’ if they were sure that the item had been presented, but did not have conscious recollection of that earlier presentation. Conscious recollection was described to the subjects in terms of their ability to recall what they were thinking when the item was presented, whether they noted some aspect of the item’s appearance or noticed some other event in the testing room, etc. In order to enable subjects to grasp this distinction more clearly, further examples adapted from Gardiner and Java (1990) were provided. In terms of the ‘‘remember’’ judgment, subjects were told to think of the name of the last movie they saw. The experimenter pointed out that in addition to the name of the movie, the subject likely also recalled where the movie was playing, whom s/he went with, whether the theater was crowded, and so on. Thus it was illustrated that subjects likely recalled the actual event of seeing the movie in addition to factual information such as its title. To contrast the ‘‘remember’’ with the ‘‘know’’ judgment, each subject was asked to think of his/her mother’s first name. It was explained that this information was likely retrieved without reference to any particular event in time, although it was certainly information that the subject knew well. After giving all of these instructions, the experimenter asked the subject to reiterate the difference between the ‘‘remember’’ and ‘‘know’’ responses before proceeding. Subjects were allowed to complete the recognition test at their own pace. The entire procedure lasted approximately 30 min.

Results and Discussion Corrected recognition performance scores (hits minus false alarms) for Experiment 1 are presented in Fig. 2. An ANOVA performed on the corrected recognition scores for all three subject groups revealed a main effect of group, F (2, 58) 5 4.65, MS e 5 .05, reflecting the fact that overall response rates were higher for the normal controls than for either patient group. (All significance levels were set at p , .05). Of greater interest was the reliable Group 3 Response Type interaction, F(2, 58) 5 20.36, MS e 5 .22. With an overall least significant difference (LSD) of .06, the reader will see in

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FIG. 2. Corrected recognition performance (hits minus false alarms) as a function of subject group and response type in Experiment 1.

Fig. 2 that both the normal controls and left TLE patients made more ‘‘know’’ than ‘‘remember’’ judgments whereas the right TLE group made significantly more ‘‘remember’’ than ‘‘know’’ judgments to these items. False alarm data for the remember/know recognition test are presented in Table 2. An ANOVA on false alarm rates revealed a main effect of judgment type, F(1, 58) 5 10.72, MS e 5 .20, with subjects being more likely overall to respond ‘‘know’’ than ‘‘remember’’ for nonstudied items incorrectly judged to have been studied earlier. This main effect was qualified by a reliable interaction between the factors of subject group and judgment type, F (2, 58) 5 3.39, MS e 5 .06. With an LSD of .06, the reader will note in Table 2 that more ‘‘know’’ than ‘‘remember’’ false alarms were given by both TLE groups, although the normal control group produced statistically TABLE 2 False Alarm Scores as a Function of Judgment Type and Subject Group in Experiment 1

Normal controls Left TLEs Right TLEs

Remember

Know

.15 .18 .05

.17 .27 .30

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equivalent numbers of each response type. Further, right TLE subjects produced fewer ‘‘remember’’ false alarms than either of the other two groups. The main effect of subject group was not reliable, F(2, 58) 5 1.18, MS e 5 .02. The data from Experiment 1 show that when perceptual processing was induced during the study of abstract visuospatial designs, recognition memory for subjects with intact right temporal lobes (both normal controls and left TLEs) was based more on perceptual fluency (‘‘know’’ judgments) than on distinctiveness (‘‘remember’’ judgments). The right hemisphere TLE patients, however, showed the opposite pattern of results. They gave virtually no ‘‘know’’ recognition judgments for the designs (.02). Rather, their responses were based more on distinctiveness as reflected in their comparatively high frequency of ‘‘remember’’ judgments (.24). Thus, the findings from Experiment 1 suggest that the abnormal recognition of visuospatial materials sometimes described for right hemisphere TLE patients may result from impaired processing of perceptual fluency. EXPERIMENT 1A

The patterns of responses within patient groups in Experiment 1 were quite consistent across patients who had previously had temporal lobectomy surgery and those who were surgical candidates. Equal numbers of pre- and postsurgical patients were tested in both subject groups, and although the number of subjects included was small, every individual subject in each group showed the same transfer pattern as the overall group average. That is, the test discriminated between all left and right temporal patients, regardless of surgical status. Although this outcome is suggestive of a general similarity between preand postsurgical patients’ performance in the remember/know paradigm, it is not particularly compelling due to the small number of patients tested. The nature of expected performance differences between pre- and postsurgical groups is a matter of some uncertainty with differences being obtained on some cognitive tasks (e.g., Andrewes et al., 1990; Delaney, Rosen, Mattson, & Novelly, 1980) but not others (e.g., Novelly, Augustine, Mattson, Glaser, Williamson, Spencer, & Spencer, 1982). To determine whether preand postsurgery TLE subjects differ in their performance on the remember/ know task, a follow-up study to Experiment 1 was conducted which included four groups of TLE patients not tested in Experiment 1. The groups included pre- and postsurgery left TLEs, as well as pre- and postoperative right TLEs. Method Two groups of 16 left and 16 right temporal lobe epilepsy patients were tested, half preand half post-surgery. Characteristics of the patients tested in Experiment 1a are presented in

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TABLE 3 Characteristics of Subject Groups Tested in Experiment 1a

N, Gender Age (years) Education (years) WAIS-R Verbal Performance WMS-R Logical memory I Logical memory II Visual reproduction I Visual reproduction II

Presurgical Left TLEs

Postsurgical Left TLEs

Presurgical Right TLEs

Postsurgical Right TLEs

4 Female 4 Male Mean 38.6 Range 30–53 Mean 13.0 Range 10–18 Mean 92.6 Range 77–106 Mean 92.1 Range 76–108 Mean 95.4 Range 82–110 Mean 102.1 Range 77–131 Mean 17.4 Range 4–31 Mean 11.5 Range 3–25 Mean 33.4 Range 29–41 Mean 24.0 Range 12–38

4 Female 4 Male Mean 34.9 Range 29–43 Mean 14.2 Range 12–16 Mean 94.5 Range 86–114 Mean 92.5 Range 77–121 Mean 96.5 Range 88–104 Mean 109.0 Range 90–133 Mean 18.4 Range 8–28 Mean 12.6 Range 5–19 Mean 24.5 Range 16–30 Mean 16.9 Range 9–30

4 Female 4 Male Mean 33.9 Range 18–50 Mean 13.6 Range 12–16 Mean 101.4 Range 80–117 Mean 104.0 Range 81–119 Mean 98.3 Range 80–122 Mean 115.5 Range 83–152 Mean 22.1 Range 10–34 Mean 20.6 Range 13–31 Mean 32.6 Range 19–40 Mean 26.1 Range 22–39

4 Female 4 Male Mean 32.8 Range 24–43 Mean 14.4 Range 12–18 Mean 103.4 Range 85–129 Mean 105.5 Range 91–128 Mean 98.5 Range 81–118 Mean 125.7 Range 84–167 Mean 24.9 Range 11–41 Mean 18.1 Range 7–37 Mean 30.1 Range 20–37 Mean 16.8 Range 8–40

Table 3. The left temporal postsurgery patients’ resections included all of the amygdala, uncus, 1.8cm of the anterior hippocampus (range 1.0 to 2.0), 4.7 cm of the anterior superior temporal gyrus (range 4.0 to 6.0), 6.0 cm of the middle temporal gyrus (range 5.0 to 8.0), and 6.5 cm of the inferior temporal gyrus (range 6.0 to 8.0). Right temporal resections included amygdala, uncus, 2.5 cm of the anterior hippocampus, 4.25 cm of the anterior superior temporal gyrus (range 1.0 to 7.0), 6.7 cm of the middle temporal gyrus (range 6.0 to 7.0), and 7.3 cm of the inferior temporal gyrus (range 6.5–8.0). Materials and procedure were identical to those described for Experiment 1. The only difference was the manipulation of surgical status between left and right TLE patients.

Results and Discussion Results from Experiment 1a are presented in Fig. 3. An ANOVA including factors of subject group (left versus right temporal focus), surgical status (pre versus post), and response type (remember versus know) was conducted on the corrected recognition data. This analysis revealed no reliable main effects of any of these factors. In particular, the main effect of surgical status did not reach statistical significance, F(1, 56) ,1, MS e 5 .003. Subjects within a group produced the same patterns of recognition judgments whether they had previously had lobectomies or not. As in Experiment 1, there was a reliable Group by Response Type interaction, F(1, 56) 5 53.93, MS e 5

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FIG. 3. Corrected recognition performance (hits minus false alarms) as a function of patient group and response type in Experiment 1a.

.50. The reader will see in Fig. 3 that regardless of surgical status, subjects with left temporal epileptogenic zones gave more ‘‘know’’ than ‘‘remember’’ judgments on the recognition test whereas right temporal patients showed the opposite pattern of responses, LSD 5 .04. No other interactions reached statistical significance. An ANOVA performed on false alarm data revealed a main effect of response type, F(1, 56) 5 39.97, MS e 5 .50. As may be seen in Table 4, all subject groups produced more ‘‘know’’ than ‘‘remember’’ false alarms. There was also a reliable Group by Response Type interaction, F(1, 56) 5 7.07, MS e 5 .09. With an LSD of .07, the reader will see in Table 4 that the right temporal patients produced fewer ‘‘remember’’ false alarms than TABLE 4 False Alarm Scores as a Function of Judgment Type and Subject Group in Experiment 1a

Left TLEs Presurgery Postsurgery Right TLEs Presurgery Postsurgery

Remember

Know

.15 .16

.30 .22

.06 .08

.32 .32

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did the left temporal patients. No other main effects or interactions reached statistical significance. The results of Experiment 1a clearly demonstrate that side of lesion rather than pre- or postsurgical status was the primary determinant of response patterns on the remember/know recognition test. Because there were no main effects of surgical status or interactions involving this variable, data were combined across pre- and postsurgical patients in Experiment 2. EXPERIMENT 2

Perceptual processing was induced during encoding in Experiments 1 and 1a through the presentation of nonnameable, abstract visuospatial designs. Aside from the selection of these unfamiliar materials, no other study manipulation was employed. Thus it was not possible to determine the degree to which various types of analysis of these visuospatial designs might impact patterns of recognition judgments. For example, it would be of interest to determine whether normal subjects always show an advantage for ‘‘know’’ over ‘‘remember’’ judgments with visuospatial designs regardless of the nature of analysis performed during study. In terms of the patient groups, it is useful to ask whether study manipulations might affect the pattern of more ‘‘know’’ than ‘‘remember’’ judgments for left TLE subjects as well as the result of more ‘‘remember’’ than ‘‘know’’ judgments given by right TLE patients. These questions were addressed in Experiment 2 in which subjects studied the visuospatial designs under two different orienting conditions. In the line count condition subjects answered questions regarding the number of vertical or horizontal lines in the designs. This orienting task was analogous to shallow or perceptual tasks frequently used with verbal materials in levels of processing paradigms in which subjects are asked to count ascending and descending letters or to report whether words are printed in upper or lower case type. In the label condition subjects made decisions regarding which of two verbal labels best fit each design. The line count condition was intended to induce perceptual processing and the label condition was constructed so as to enhance distinctiveness (e.g., Lockhart, Craik, & Jacoby, 1976). These manipulations resulted in a 3 (subject group) 3 2 (study condition) 3 2 (type of recognition judgment) design. For normal control subjects, the distinctiveness/fluency processing account predicts that the line count study condition should produce the same pattern of results observed in Experiment 1, with more ‘‘know’’ than ‘‘remember’’ responses given on the recognition test. For the label condition in which individual items are made more distinct during encoding, however, a reversal of this pattern was expected with more ‘‘remember’’ than ‘‘know’’ judgments being made. For the patient groups the same response patterns obtained in Experiment 1 were expected. This was because it was presumed

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TABLE 5 Characteristics of Subject Groups Tested in Experiment 2

N Gender Age (years) Education (years) Pre-post surgery WAIS-R Verbal Performance WMS-R Logical memory I Logical memory II Visual reproduction I Visual reproduction II

Left TLEs

Right TLEs

Normal controls

12 6 Male 6 Female Mean 32.3 Range 25–51 Mean 13.6 Range 12–18 6 Pre 6 Post Mean 95.6 Range 79–115 Mean 94.3 Range 82–108 Mean 98.6 Range 80–139 Mean 101.9 Range 77–123 Mean 16.2 Range 4–24 Mean 10.7 Range 3–19 Mean 24.8 Range 5–35 Mean 17.9 Range 5–33

12 7 Male 5 Female Mean 30.6 Range 23–41 Mean 13.6 Range 12–18 6 Pre 6 Post Mean 100.4 Range 84–115 Mean 103.1 Range 81–122 Mean 95.8 Range 83–114 Mean 126.8 Range 74–164 Mean 25.8 Range 6–39 Mean 22.1 Range 9–32 Mean 28.7 Range 12–40 Mean 27.1 Range 8–40

12 6 Male 6 Female Mean 32.3 Range 22–48 Mean 13.3 Range 12–16 — —

— — — — — — —

that the patients’ left and right temporal lesions were producing deficits in processing that should not change qualitatively as a result of study manipulation, although effects might be somewhat attenuated. Method Subjects. Subject characteristics are presented in Table 5. Three groups of 12 subjects each were tested including unilateral left and right TLE patients as well as a group of normal controls similar to these patients on variables of age, gender, and years of education. All six postsurgery left temporal patients had undergone removal of amygdala and uncus, as well as the anterior 1.7 cm of the hippocampus (range 1.0 to 2.0), 4.5 cm of the superior temporal gyrus (range 4.0 to 5.5), 5.3 cm of the middle temporal gyrus (range 5.0 to 5.5), and 6.1 cm of the inferior temporal gyrus (range 5.5–7.0). All postsurgery right temporal patients except 1 had resections which included the amygdala and uncus, along with 2.5 cm of the anterior hippocampus. (These regions were spared in one patient.) Right temporal resections also included the anterior 4.6 cm of the superior temporal gyrus (range 1.0 to 7.0), 6.1 cm of the middle temporal gyrus (range 5.0 to 7.0), and 7.5 cm of the inferior temporal gyrus (range 7.0 to 8.0).

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Design and materials. In addition to the manipulation of subject type as a between subjects factor, the design included study condition as a within-subjects factor. All subjects studied items both in a condition in which they were encouraged to assign verbal labels to visuospatial designs as well as in a line count condition in which they were asked to choose which of two numbers were correct in representing the number of horizontal or vertical lines in these designs. Sixty-eight of the 70 designs used in Experiment 1 were chosen and divided into two base lists of 34 items each. Within each base list, items were further divided into two sublists of 17 items each, and each subject studied one sublist in each orienting condition. Subjects saw each item only once during the study period. Items within a base list were always presented in the same order, but study condition was counterbalanced across subjects such that half of the subjects received the label condition first and half received the line count condition first. Prior to the experiment, a label of one to three words was assigned to each item. Referring to the designs presented in Figure 1 starting at the top left hand design and proceeding clockwise, the labels ‘‘fountain pen,’’ ‘‘knee,’’ ‘‘army tank,’’ and ‘‘hockey sticks,’’ respectively were assigned. As each item was presented for study in the label condition, the experimenter asked the subject to choose which of two labels was most appropriate for that design. For example, a subject studying base list 1 received the items in the left hand column of Fig. 1 and was asked the questions ‘‘Does this look more like a fountain pen or a knee?’’ and ‘‘Does this look more like an army tank or hockey sticks?’’ as the top left and lower left items, respectively, were presented. Subjects studying base list 2 saw the items in the right hand column of Fig. 1 and received the same questions, but were expected to choose the labels not selected by the subjects studying the other base list. Thus, queries were held constant as studied base list was varied. The position in the query (first or second) of the experimenter-assigned labels was randomly balanced across each sublist of 17 studied items. A similar method was adopted for the line count orienting condition. Referring again to Figure 1, subjects studying base list 1 were asked the questions ‘‘Does this design have one or two horizontal lines?’’ and ‘‘Does this design have zero or one vertical line?’’ as the top and lower left hand items were presented. Subjects studying base list 2 were asked the same questions as the top and lower right hand items were presented, but the correct answer for those subjects was the number not selected by the subjects studying base list 1. Thus, queries were held constant across subjects studying different base lists. Again, position of correct alternatives within the queries was randomized across sublists. Procedure. The procedure employed was identical to that described in Experiments 1 and 1a except that subjects received the label and line count orienting conditions during the study phase. For the label condition, subjects were instructed to choose the more appropriate label for each item given the two alternatives provided by the experimenter. Subjects were told that although the designs were very abstract and they might not feel that either label was particularly appropriate, they should nevertheless make a choice for each item. The reader will note that there were no right and wrong answers to these queries. Rather, the aim was to induce subjects into a labeling mode regardless of whether they happened to pick the label assigned by the experimenter. In the line count condition the experimenter described the types of questions that would be asked and reviewed what was meant by horizontal and vertical lines to ensure minimal mistakes (such as counting diagonal lines). Items were presented for 6 sec each during study. The recognition test was administered immediately following presentation of the two sublists. The entire procedure lasted approximately 30 min.

Results and Discussion An ANOVA performed on the responses given by subjects during the study phase of the experiment revealed a main effect of study condition, F(1, 66) 5 78.06, MS e 5 .66. (All significance levels were set at p , .05).

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FIG. 4. Corrected recognition performance (hits minus false alarms) as a function of subject group, study condition, and response type in Experiment 3.

Overall, more correct responses were given to queries in the line count orienting condition (95%) than in the label condition (76%). This discrepancy was expected, of course, since only the line count condition had true right and wrong answers. ‘‘Correctness’’ in the label condition was defined in terms of whether subjects’ choices for labels matched those determined preexperimentally. The primary points of interest concerning responses made during study were that no main effect of group was observed, F(2, 66) , 1, and that the group by study condition interaction did not approach significance, F(2, 66) 5 1.33, MS e 5 .01. The corrected recognition data (hits minus false alarms) obtained in Experiment 2 are presented in Fig. 4. An ANOVA performed on the corrected recognition scores revealed a main effect of study condition, F(1, 132) 5 19.15, MS e 5 .46, indicating that there were more correct recognition judgments made for items studied in the label than in the line count condition. This finding replicates the numerous levels of processing effects reported previously in the memory literature. Of greater interest were several interactions, including ones obtained between variables of study condition and type of recognition judgment, F(1, 132) 5 38.41, MS e 5 .92 and between variables of subject group and type of recognition judgment, F (2, 132) 5 34.67, MS e 5 .83. Additionally there was a reliable overall subject group x study condition x recognition judgment interaction, F(2, 123) 5 10.22, MS e 5 .24. (No other main effects or interactions were significant.) The nature of these interactions was examined more closely with individ-

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TABLE 6 False Alarm Scores as a Function of Judgment Type and Subject Group in Experiment 2

Normal controls Left TLEs Right TLEs

Remember

Know

.10 .16 .09

.11 .11 .14

ual cell comparisons. With an LSD of .06, the reader will see in the left panel of Fig. 4 that normal controls gave more ‘‘know’’ (.25) than ‘‘remember’’ (.01) judgments in the perceptual line count condition, thus replicating the pattern of responses obtained in Experiment 1. When distinctiveness was enhanced during encoding in the label condition, however, this pattern was reversed with normal subjects making more ‘‘remember’’ than ‘‘know’’ judgments (.46 versus .06). In contrast to the specificity of transfer obtained for normal controls, left TLE patients failed to show differences in patterns of recognition judgments for the two encoding conditions, giving more ‘‘know’’ than ‘‘remember’’ responses in both the label (.34 versus .09) and line count (.34 versus 2.04) conditions. Thus, recognition memory for left TLE patients was based on perceptual fluency even in the label condition in which distinctiveness was emphasized. As in Experiment 1, patterns of responding between the two patient groups were completely dissociated. Patients with right temporal lesions showed the opposite pattern of responses, producing more ‘‘remember’’ than ‘‘know’’ judgments in both the label (.34 versus .08) and line count (.12 versus .02) conditions. Thus, recognition judgments for the right temporal patients were based on distinctiveness regardless of encoding condition. All of the individual TLE subjects showed the transfer pattern of the overall group with the exception of one postsurgery left TLE and one postsurgery right TLE. As in Experiments 1 and 1a, then, the remember/know recognition paradigm proved very useful in discriminating among patients having left and right temporal lesions, regardless of side of lesion or pre/post surgical status. The false alarm data obtained in Experiment 2 are presented in Table 6. An ANOVA failed to show main effects for either subject group or type of recognition judgment (both Fs , 1). Similarly, the interaction between subject group and type of recognition judgment did not approach statistical significance, F(2, 66) 5 1.59, MS e 5 .02. This finding runs counter to the ones observed in Experiments 1 and 1a in which all patient groups made more ‘‘know’’ than ‘‘remember’’ false alarms. Although one cannot know with any certainty, it seems reasonable to suggest that the discrepancy is due in

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part to strategies induced by the study manipulation employed in Experiment 2. However, questions such as this await further investigation. GENERAL DISCUSSION

To summarize, both normal control and left TLE groups made more ‘‘know’’ than ‘‘remember’’ judgments on a recognition test of visuospatial materials in Experiment 1, although the right TLE patients showed the opposite response pattern. Experiment 1a demonstrated that this pattern of recognition judgments was obtained for presurgical as well as postsurgical patients. Orienting conditions were manipulated at study in Experiment 2 in order to enhance either perceptual fluency or distinctiveness of the visuospatial designs. Normal subjects gave more ‘‘know’’ responses for items studied in the line count (fluency) condition and more ‘‘remember’’ judgments for items studied in the label (distinctiveness) condition. The patient groups, however, showed the same patterns of transfer as those obtained in Experiments 1 and 1a for both study conditions. Returning to the questions set out in the introduction, these findings demonstrate that principled results may be obtained using the remember/know paradigm to test memory for visuospatial materials. As already noted, all other experimental tests of this paradigm have been conducted using verbal materials, with the exception of an unpublished study assessing memory for musical jazz passages (Vernon, 1989). These experiments show that one may enhance the perceptual fluency component of recognition memory by choosing nonnameable visual materials as study items and that this fluency will be revealed in normal subjects by a predominance of ‘‘know’’ as opposed to ‘‘remember’’ recognition judgments. These results corroborate Rajaram’s (1996; Rajaram & Roediger, 1997) previous interpretations of findings obtained in the remember/know paradigm and were predicted by a distinctiveness/fluency processing framework for recognition memory. When study conditions emphasized perceptual processing, either by choice of study materials (Experiment 1) or by encoding condition (line count condition in Experiment 2), normal subjects gave more ‘‘know’’ recognition judgments based on perceptual fluency than judgments based on distinctiveness. However, when study conditions enhanced distinctiveness of individual items (the label condition of Experiment 2), normal subjects gave more ‘‘remember’’ judgments. The second question motivating these experiments was whether the remember/know test might prove useful as an evaluation device for neurologically impaired patients. All studies in which this paradigm has previously been used have been ones in which normal young or elderly subjects were tested. The present studies show that the test is one that the patients can perform quite reliably if tested individually and given careful instructions.

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Furthermore, the consistency of patterns of responses obtained across patients was high, with all subjects showing the group pattern except one left temporal and one right temporal patient in Experiment 2. A final line of inquiry in these studies concerned the contribution of left and right temporal lobe structures to specific patterns of ‘‘remember’’ and ‘‘know’’ judgments obtained on the recognition tests. The results obtained with the TLE patient groups provide evidence that different components of recognition memory are supported by structures in the left and right temporal lobes. This finding extends the distinctiveness/fluency framework, suggesting that, at least in part, neurological substrates of the left temporal lobe mediate distinctiveness processing whereas right temporal lobe structures subserve processes underlying perceptual fluency. The predominance of perceptual fluency exhibited by the normal controls in Experiments 1 and 1a was eliminated in the label condition in Experiment 2 in which recognition judgments were based more on distinctiveness. The left TLE patients did not show this reversal in response patterns, however, presumably because their particular lesions limited the amount and quality of pertinent conceptual processing that they could perform. Indeed, verbal memory experiments using such paradigms as semantic cued recall, answering general knowledge questions, and category member production have shown deficits in conceptual memory for left TLE patients (Blaxton, 1992). As a result, left TLE recognition judgments in this paradigm were made largely on the basis of perceptual fluency, as was reflected by the fact that they gave more ‘‘know’’ than ‘‘remember’’ judgments. By the same token, the right TLEs were limited in their ability to make recognition judgments on the basis of perceptual fluency, and so relied more heavily on detection of distinctiveness. This was reflected in their tendency to give more ‘‘remember’’ than ‘‘know’’ judgments, even following study conditions designed to be largely perceptual. These data speak to another concern sometimes raised about the interpretation of ‘‘remember’’ and ‘‘know’’ judgments in this recognition paradigm. Specifically one might wonder whether these judgments reflect differences in trace strength rather than differences among separable components of recognition memory, with ‘‘remember’’ judgments given for items whose trace strength is relatively strong, and ‘‘know’’ judgments given for weaker items. The patient data from all three experiments argue persuasively against this view. In all cases the patterns of ‘‘remember’’ and ‘‘know’’ judgments were completely dissociated with left TLE patients giving more ‘‘know’’ judgments and right TLE patients giving more ‘‘remember’’ judgments. This occurred despite the fact that overall levels of performance collapsed across judgment type were statistically equivalent between groups. This result cannot be readily explained by a trace strength account of ‘‘remember’’ and ‘‘know’’ judgments. The fact that the remember/know paradigm successfully discriminated between left and right TLEs has potential clinical implications as well. Al-

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though standard neuropsychological tests such as the WMS-R are often useful in implicating left temporal damage, performance patterns on these tests cannot always be used reliably to identify right temporal patients. This may be because right temporal patients can often verbally recode the visuospatial stimuli used in standard evaluations (e.g., Milner & Teuber, 1968). Since these patients do not usually exhibit verbal memory deficits, they may appear unimpaired on these verbally codable tests for visuospatial materials. It will be of interest, then, to determine whether the present results which show clear differences in response patterns between right TLEs and normal subjects may be extended to other clinical populations. REFERENCES Andrewes, D. G., Puce, A., & Bladin, P. F. 1990. Post-ictal recognition memory predicts laterality of temporal lobe seizure focus: Comparison with post-operative data. Neuropsychologia, 28, 957–967. Barr, W. B. in press. Examining the right temporal lobe’s role in nonverbal memory. Brain & Cognition. Blaxton, T. A. 1992. Dissociations among memory measures in memory-impaired subjects: Evidence for a processing account of memory. Memory & Cognition, 20, 549–562. Delaney, R. C., Rosen, A. J., Mattson, R. H., & Novelly, R. A. 1980. Memory function in focal epilepsy: A comparison of non-surgical unilateral temporal lobe and frontal lobe samples. Cortex, 16, 103–117. Fedio, P., & Mirsky, A. F. 1969. Selective intellectual deficits in children with temporal lobe or centrencephalic epilepsy. Neuropsychologia, 7, 287–300. Gardiner, J. M. 1988. Functional aspects of recollective experience. Memory & Cognition, 16, 309–313. Gardiner, J. M., Gawlik, B., & Richardson-Klavehn, A. 1994. Maintenance rehearsal affects knowing, not remembering: Elaborative rehearsal affects remembering, not knowing. Psychonomic Bulletin and Review, 1, 107–110. Gardiner, J. M., & Java, R. I. 1990. Recollective experience in word and nonword recognition. Memory & Cognition, 18, 23–30. Gardiner, J. M., & Java, R. I. 1991. Forgetting in recognition memory with and without recollective experience. Memory & Cognition, 19, 617–623. Gardiner, J. M., & Java, R. I. 1993. Recognising and remembering. In A. F. Collins, S. E. Gathercole, M. A. Conway, & P. E. Morris (Eds.), Theories of memory. Hillsdale, NJ: Erlbaum. Gardiner, J. M., & Parkin, A. J. 1990. Attention and recollective experience in recognition memory. Memory & Cognition, 18, 579–583. Glowinski, H. 1973. Cognitive deficits in temporal lobe epilepsy. The Journal of Nervous and Mental Disease, 157, 129–137. Goldstein, L. H., Canavan, A. G. M., & Polkey, C. E. 1988. Verbal and abstract designs paired-associate learning after unilateral temporal lobectomy. Cortex, 24, 41–52. Gregg, V. H., & Gardiner, J. M. 1994. Recognition memory and test awareness: A large effect of study-test modalities on ‘‘know’’ responses following a highly perceptual orienting task. European Journal of Cognitive Psychology, 6, 131–147. Hunt, R. R., & McDaniel, M. A. (1993) The enigma of organization and distinctiveness. Journal of Memory and Language, 32, 421–445. Jacoby, L. L. 1983a. Perceptual enhancement: Persistent effects of an experience. Journal of Experimental Psychology: Learning, Memory, and Cognition, 9, 21–38.

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