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PubMed1998

Working and strategic memory deficits in schizophrenia.

Working memory and its contribution to performance on strategic memory tests in schizophrenia were studied. Patients (n = 18) and control participants (n = 15), all men, received tests of immediate memory (forward digit span), working memory (listening, computation, and backward digit span), and long-term strategic (free recall, temporal order, and self-ordered pointing) and nonstrategic (recognition) memory. Schizophrenia patients performed worse on all tests. Education, verbal intelligence, and immediate memory capacity did not account for deficits in working memory in schizophrenia patients. Reduced working memory capacity accounted for group differences in strategic memory but not in recognition memory. Working memory impairment may be central to the profile of impaired cognitive performance in schizophrenia and is consistent with hypothesized frontal lobe dysfunction associated with this disease. Additional medial-temporal dysfunction may account for the recognition memory deficit.

Adult↗
PubMed2001

Brain activity evidence for recognition without recollection after early hippocampal damage.

Amnesic patients with early and seemingly isolated hippocampal injury show relatively normal recognition memory scores. The cognitive profile of these patients raises the possibility that this recognition performance is maintained mainly by stimulus familiarity in the absence of recollection of contextual information. Here we report electrophysiological data on the status of recognition memory in one of the patients, Jon. Jon's recognition of studied words lacks the event-related potential (ERP) index of recollection, viz., an increase in the late positive component (500--700 ms), under conditions that elicit it reliably in normal subjects. On the other hand, a decrease of the ERP amplitude between 300 and 500 ms, also reliably found in normal subjects, is well preserved. This so-called N400 effect has been linked to stimulus familiarity in previous ERP studies of recognition memory. In Jon, this link is supported by the finding that his recognized and unrecognized studied words evoked topographically distinct ERP effects in the N400 time window. These data suggest that recollection is more dependent on the hippocampal formation than is familiarity, consistent with the view that the hippocampal formation plays a special role in episodic memory, for which recollection is so critical.

Adult↗
PubMed1999

Executive function and attention deficit hyperactivity disorder: stimulant medication and better executive function performance in children.

BACKGROUND: Executive function deficits have been reported repeatedly in children with Attention Deficit Hyperactivity Disorder (ADHD). Stimulant medication has been shown to be effective in improving cognitive performance on most executive function tasks, but neuropsychological tests of executive function in this population have yielded inconsistent results. Methodological limitations may explain these inconsistencies. This study aimed to measure executive function in medicated and non-medicated children with ADHD by using a computerized battery, the Cambridge Neuropsychological Test Automated Battery (CANTAB), which is sensitive to executive function deficits in older patients with frontostriatal neurological impairments. METHODS: Executive function was assessed in 30 children with ADHD: 15 were stimulant medication naive and 15 were treated with stimulant medication. These two groups were compared to 15 age, sex and IQ matched controls. RESULTS: The unmedicated children with ADHD displayed specific cognitive impairments on executive function tasks of spatial short-term memory, spatial working memory, set-shifting ability and planning ability. Impairments were also seen on spatial recognition memory and delayed matching to sample, while pattern recognition memory remained intact. The medicated children with ADHD were not impaired on any of the above executive function tasks except for deficits in spatial recognition memory. CONCLUSIONS: ADHD is associated with deficits in executive function. Stimulant medication is associated with better executive function performance. Prospective follow-up studies are required to examine these effects.

Adolescent↗
PubMed1999

Memory performance of geriatric and nongeriatric chronic schizophrenic patients: a cross-sectional study.

Memory functioning has been studied extensively in nongeriatric schizophrenic patients, leading to the suggestion that schizophrenic patients manifest a "subcortical" pattern of memory deficits. Few previous studies examined very poor outcome patients with a chronic course of hospitalization. This study examined the association of age and global cognitive dysfunction with verbal and spatial learning and delayed recall, as well as examining differential impairments in delayed recall as compared to delayed recognition memory. Sixty-six chronic schizophrenic patients were studied, with 30 of these patients over the age of 65. Verbal (California Verbal Learning Test) and spatial (Biber Figure Learning Test) serial learning and delayed memory tests were administered. All aspects of memory functioning were correlated with estimates of global cognitive status. When global cognitive status was controlled, age effects were still found for the majority of the memory measures. Delayed recognition memory was not spared, being performed as poorly as delayed recall. In contrast to previous studies of better-outcome patients with schizophrenia, geriatric patients with chronic schizophrenia performed more poorly than nongeriatric patients. The lack of sparing of delayed recognition memory suggests that previous findings of specific recall memory deficit and a subcortical profile of memory impairments may apply to schizophrenic patients with less severe global cognitive impairments. These data suggest that poor-outcome patients may have a pattern of memory impairments that has some features in common with cortical dementia.

Adult↗
PubMed2005

The role of the hippocampus in object recognition in rats: examination of the influence of task parameters and lesion size.

Studies examining the effects of hippocampal lesions on object recognition memory in rats have produced conflicting results. The present study investigated how methodological differences and lesion size may have contributed to these discrepancies. In Experiment 1 we compared rats with complete, partial (septal) and sham hippocampal lesions on a spontaneous object recognition task, using a protocol previously reported to result in deficits following large hippocampal lesions . Rats with complete and partial hippocampal lesions were unimpaired, suggesting the hippocampus is not required for object recognition memory. However, rats with partial lesions showed relatively poor performance raising the possibility that floor effects masked a deficit on this group. In Experiment 2, we used a second spontaneous object recognition protocol similar to that used by the two other studies that have reported deficits following hippocampal lesions . Rats with complete hippocampal lesions were significantly impaired, whereas rats with partial lesions were unimpaired. However, the complete lesion group showed less object exploration during the sample phase. Thus, the apparent recognition memory deficit in Experiment 2 may be attributable to differential encoding. Together, these findings suggest that the hippocampus is not required for intact spontaneous object recognition memory. These findings suggest that levels of object exploration during the sample phase may be a critical issue, and raise the possibility that previous reports of object recognition deficits may be due to differences in object exploration rather than deficits in object recognition per se.

Analysis of Variance↗
PubMed2000

Effect of a subanesthetic dose of ketamine on memory and conscious awareness in healthy volunteers.

RATIONALE: Ketamine is an NMDA receptor antagonist with psychotogenic and cognitive effects in healthy volunteers and schizophrenic patients which has been proposed to be a useful tool to investigate neurobiological basis of schizophrenia. OBJECTIVE: The present study characterized the effects of a subanesthetic dose of ketamine on memory and related subjective states of awareness in healthy volunteers. METHODS: Twenty-six subjects were given either a 60-min ketamine (0.5 mg/kg per hour) or a placebo infusion. To obtain constant plasma ketamine throughout the experiment, ketamine was administered using a computer-controlled infusion system. Subjects carried out episodic memory tasks involving words presented before and during infusion. Memory performance was assessed with recognition and free recall tasks. Subjective states of awareness were assessed using an experiential approach. Levels of psychopathology were evaluated with BPRS. RESULTS: Ketamine impaired performance in free recall and recognition of words presented during, but not before, infusion. There were no differences between groups concerning states of awareness associated with recognition memory. Subjects under ketamine had higher BPRS total scores as well as BPRS negative and positive cluster scores than control subjects. CONCLUSIONS: Ketamine decreases episodic memory performance by impairing encoding, but not retrieval processes. It does not selectively impair subjective states of awareness associated with recognition memory as it has been seen in patients with schizophrenia. Ketamine might mimic the memory impairment associated with acute, but not chronic, forms of schizophrenia.

Adult↗
PubMed1999

P300 as an index of recognition in a standard and difficult match-to-sample test: a model of amnesia in normal adults.

Earlier research has supported the use of a P300 (P3)-based procedure to detect simulated amnesia. In the present experiment, an attempt was made to model the behavior and event-related potentials (ERPs) that amnestic patients might demonstrate with relatively easy recognition memory tests, by increasing the difficulty of a match-to-sample recognition memory test taken by 18 memory-unimpaired undergraduates. None of the participants in the modeled amnesic condition were classified as having intact recognition memory as the result of P3-based intra-individual tests (specificity = 100%). The results support the utility of a P3 procedure for the detection of malingering by demonstrating the procedure to be a valid measure of impaired recognition with this model of amnesia.

Adult↗
PubMed1988

The influence of expertise on X-ray image processing.

Observers with four different levels of radiological experience performed a recognition memory task on slides of faces and chest X-ray films. Half of the X-ray films revealed clinically significant abnormalities and half did not. Recognition memory for faces was uniformly high across all levels of radiological experience. Memory for abnormal X-ray films increased with radiological experience and, for the most experienced radiologists, was equivalent to memory for faces. Surprisingly, recognition memory for normal films actually decreased with radiological experience from above chance to a chance level. These results indicate that radiological expertise is associated with selective processing of clinically relevant abnormalities in X-ray images. Expert radiologists appear to process X-ray images the way that we all process faces, by quickly detecting and devoting processing resources to features that distinguish one stimulus from another. However, the selective processing of X-ray films appears to be restricted to clinically relevant abnormalities. As they develop the ability to detect these abnormalities, radiologists appear to lose the ability to detect variations in normal features.

Clinical Competence↗
PubMed1981

Developmental changes in infants' retention of visual stimuli.

In the first of 2 studies of visual recognition memory, 6- and 9-month-old infants were tested for their ability to differentiate novel from familiar test stimuli immediately following brief amounts of familiarization. After all problems were given, the paired test stimuli were re-presented for a test of delayed recognition memory. The delay test thus occurred after a period during which the infant had been looking at a number of different intervening stimuli. The 6- and 9-month-olds both showed significant recognition memory on 3 of the problems immediately following familiarization. While the older infants continued to show recognition on each of these problems after a delay, the younger infants failed to show evidence of retention on 2 of the 3 problems they had been able to recognize initially. In a second study, 6-month-olds were tested for delayed recognition under conditions where the interval between the familiarization and test was free of any interpolated visual stimuli. Despite this effort to minimize interference, the pattern of responding remained virtually identical to that of the first study. Thus the 6-month-olds appeared to have difficulty recognizing the stimuli over short delays, even in the absence of intervening distractors. The greater capacity for delayed recognition memory among the 9-month-olds is discussed in terms of other memory changes that may be taking place at that age.

Age Factors↗
PubMed2001

Excitotoxic lesions of the pre- and parasubiculum disrupt object recognition and spatial memory processes.

Rats with bilateral ibotenic acid lesions centered on the pre- and parasubiculum and control rats were tested in a series of spatial memory and object recognition memory tasks. Lesioned rats were severely impaired relative to controls in both the reference and working memory versions of the water maze task and displayed a delay-dependent deficit in a delayed nonmatch to place procedure conducted in the T-maze. Lesioned rats also displayed reduced exploration in a novel environment, and performance was altered in an object recognition procedure as compared with the control group. These findings indicate that the pre- and parasubiculum plays an important role in the processing of both object recognition and spatial memory.

Animals↗
PubMed1995

Representation of rotated objects in explicit and implicit memory.

The effects of rotating familiar and novel objects in depth between study and test were explored on short-term recognition, long-term recognition, and priming tasks. Short-term recognition memory was not affected by rotation in depth when the study and test views shared the same visible parts. However, long-term recognition was sensitive to rotation, even when all the parts were visible in both views. Priming was also affected by rotation, but only when study and test views did not share the same parts, or when test views were generated from rotations greater than 67 degrees. Together, the results suggest that long-term recognition memory is mediated by representations that specify viewpoint in depth precisely, whereas priming is mediated by representations that are more broadly tuned with respect to orientation. Furthermore, the insensitivity of the short-term recognition memory task to rotation suggests the possibility that viewpoint-invariant descriptions are generated from multiple successive views.

Humans↗
PubMed1991

Perception and memory for faces in Parkinson's disease.

This study investigated face processing abilities in patients with late-onset Parkinson's disease. In the first experiment, the Parkinson's disease patients were impaired on a recognition memory test for unfamiliar faces but showed no deficit relative to controls in recognition memory for words. The Parkinson's disease patients were also impaired at matching different photographs of unfamiliar faces. Experiment 2 revealed that the memory deficit affected recognition of familiar as well as unfamiliar faces and extended the face perception impairment to sex decisions and to the analysis of facial speech. An additional verbal recognition memory test again revealed no significant differences between the performance of the Parkinson's disease and control groups. It is argued that the memory impairment is not accountable for simply in terms of the perceptual deficits, and the problems that the patients experience are discussed in terms of the functional model of face processing put forward by Bruce and Young (Brit. J. Psychol. 77, 305-327, 1986).

Aged↗
PubMed2001

Opposite relationship of hippocampal and rhinal cortex damage to delayed nonmatching-to-sample deficits in monkeys.

Three recent studies in macaque monkeys that examined the effects on memory of restricted hippocampal lesions (Murray and Mishkin, J Neurosci 1998;18:6568-6582; Beason-Held et al., Hippocampus 1999;9:562-574; Zola et al., J Neurosci 2000;20:451-463) differed in their conclusions about the involvement of the hippocampus in recognition memory. Because these experiments used a common behavioral procedure, trial-unique visual delayed nonmatching-to-sample (DNMS), a quantitative synthesis ("meta-analysis") was performed to determine whether hippocampal lesions produced a reliable net impairment in DNMS performance, and whether this impairment was related to the magnitude of hippocampal damage. A similar analysis was performed on data from monkeys with perirhinal or rhinal cortex damage (Meunier et al., J Neurosci 1993;13:5418-5432; Buffalo et al., Learn Mem 1999;6:572-599). DNMS performance scores were transformed to d' values to permit comparisons across studies, and a loss in d' score, a measure of the magnitude of the recognition deficit relative to the control group, was calculated for each operated monkey. Two main findings emerged. First, the loss in d' following hippocampal damage was reliably larger than zero, but was smaller than that found after lesions limited to the perirhinal cortex. Second, the correlation of loss in d' with extent of hippocampal damage was large and negative, indicating that greater impairments were associated with smaller hippocampal lesions. This relationship was opposite to that between loss in d' and rhinal cortex damage, for which larger lesions were associated with greater impairment. These findings indicate that damage to the hippocampus and to the rhinal cortex affects recognition memory in different ways. Furthermore, they provide a framework for understanding the seemingly disparate effects of hippocampal damage on recognition memory in monkeys, and by extension, for interpreting the conflicting reports on the effects of such damage on recognition memory abilities in amnesic humans.

Animals↗
PubMed1976

Recognition gradients for random shapes following distinctive or equivalent verbal association training.

The effect of distinctive and equivalent verbal label training on a subsequent test of recognition memory for random shapes were assessed. Shape continua, systematically relating the labeled shapes, were used in the memory test so that gradients of recognition memory were obtained. Distinctive-nonrepresentative-label training produced symmetrical recognition gradients with a single mode at the correct target shape. Equivalent-label training produced symmetrical gradients that were as steep as the distinctive-label gradients, but the mode of the equivalent-label gradients was shifted to a distractor shape that varied from the target in the direction of the equivalent-label shape. The results offered support to a Gestalt/configurational account of the effects of verbal labels on memory for form, but the data were also consistent with an extension of Ellis' conceptual coding hypothesis. It was concluded that, rather than being a competing alternative account, the conceptual coding hypothesis may be viewed as an updated, more analytic statement of the older Gestalt view.

Association Learning↗
PubMedDate not supplied

Cognitive decline associated with normal aging in rats: a neuropsychological approach.

The effects of aging on cognitive capacities were examined by comparing the performance of young and old rats on tasks characterized as dependent on different brain systems. This neuropsychological approach was employed to determine the extent to which multiple neural systems are compromised in aging and whether deterioration of one system correlates with that of another. The two tasks used in the present study were an odor-guided recognition memory task, for which different aspects of performance have been shown to be dependent on the integrity of the orbital prefrontal and perirhinal-entorhinal cortex, and the Morris water maze, for which performance depends on the medial prefrontal cortex and hippocampus. Rats were trained on the recognition memory task under minimal memory load and then challenged with longer memory delays and higher levels of inter-item interference. Considerable variation was observed in the performance of aged rats on acquisition of the recognition memory task, and unlike young rats, some aged rats could not acquire the task. Nevertheless, those aged rats who did acquire the cDNM task performed as well as young animals when the memory delay was extended and interference was elevated. In addition, consistent with previous findings, the performance of the same aged rats was highly variable in the Morris water maze task. Furthermore, although correlations between scores on the two tasks for individual aged rats were not reliable, only those aged rats that performed outside the performance range of young rats in the water maze were impaired on acquisition of the recognition memory task. This pattern of findings is consistent with age-related dysfunction in multiple subdivisions of the prefrontal cortex as well as the hippocampus and suggests that these brain regions may deteriorate in the same subgroup of aged rats.

Aging↗
PubMed1995

Remembering versus knowing the past: children's explicit and implicit memories for pictures.

Two studies are reported examining children's explicit and implicit memory for pictures, using measures of recognition memory and perceptual facilitation. In Experiment 1, 3-year-olds showed significant implicit memory, as assessed by perceptual facilitation in identifying blurred pictures after a 3-month delay, even though they showed no explicit memory for the pictures, as assessed by recognition. This was true even though initial exposure to the pictures had been only in clear focus. The finding was replicated in Experiment 2, which also included 5-year-olds and adults. Recognition memory and perceptual facilitation were related for adults, but not for children at either age. The data suggest that age-related improvements in explicit memory could be due, at least in part, to the realization that perceptual fluency can be an indicator of prior experience.

Adult↗
PubMed2000

Resampling approach to statistical inference: bootstrapping from event-related potentials data.

We propose the use of the bootstrap resampling technique as a tool to assess the within-subject reliability of experimental modulation effects on event-related potentials (ERPs). The assessment of the within-subject reliability is relevant in all those cases when the subject score is obtained by some estimation procedure, such as averaging. In these cases, possible deviations from the assumptions on which the estimation procedure relies may lead to severely biased results and, consequently, to incorrect functional inferences. In this study, we applied bootstrap analysis to data from an experiment aimed at investigating the relationship between ERPs and memory processes. ERPs were recorded from two groups of subjects engaged in a recognition memory task. During the study phase, subjects in Group A were required to make an orthographic judgment on 160 visually presented words, whereas subjects in Group B were only required to pay attention to the words. During the test phase all subjects were presented with the 160 previously studied words along with 160 new words and were required to decide whether the current word was "old" or "new." To assess the effect of word imagery value, half of the words had a high imagery value and half a low imagery value. Analyses of variance performed on ERPs showed that an imagery-induced modulation of the old/new effect was evident only for subjects who were not engaged in the orthographic task during the study phase. This result supports the hypothesis that this modulation is due to some aspect of the recognition memory process and not to the stimulus encoding operations that occur during the recognition memory task. However, bootstrap analysis on the same data showed that the old/new effect on ERPs was not reliable for all the subjects. This result suggests that only a cautious inference can be made from these data.

Adult↗
PubMed1999

Extending the spontaneous preference test of recognition: evidence of object-location and object-context recognition.

The natural preference for novel objects which is displayed by rats has been used as a behavioural index to test object recognition. In this series of experiments the standard spontaneous recognition task was extended to look at other types of recognition memory; memory for place (recognition that an object is in a location where previously there had been no object), memory for object in place (recognition that a specific object has changed position with another object) and memory for context (recognition that a familiar object is in a context different to that in which it was previously encountered). We also included a standard test of object recognition in which successful discrimination relied primarily on visual cues. In addition, we looked at how the differential exploration of objects varied within the 3 min of the test phase. The results showed that rats were sensitive to the changes made in all of the test conditions and that the level of discrimination varied within the 3 min test phase. In the standard condition and the context condition, the first 2 min were found to be the most sensitive period. In the two conditions involving a position change, discrimination was only evident in the first minute.

Animals↗