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Biomedical subjects

G Winocur

Publications and source records attributed to G Winocur.

At least 55 records · Page 3Linked to original sources
PubMed1990

Hippocampal and prefrontal cortex contributions to learning and memory: analysis of lesion and aging effects on maze learning in rats.

Young adult rats with bilateral lesions to the hippocampus or prefrontal cortex, young operated controls, and normal old rats were tested on two complex mazes in the Hebb-Williams series. Approximately half the animals were previously trained on one of the mazes; the remainder received no previous training. The trained hippocampal rats showed sparing of memory for the general skill of maze learning but poor recall of the specific maze on which they had been previously trained. The opposite pattern was observed in trained prefrontal rats. In contrast, the aged rats' memory for maze-specific and maze-general information was impaired. The results confirmed the importance of the hippocampus for recalling highly specific information and pointed to a possible role for the frontal lobes in learning and remembering nonspecific skill-related information. The generalized deficit of the aged rats indicates that both types of memory were compromised and offers further evidence of frontal lobe and hippocampal dysfunction in normal aging.

Aging↗
PubMed1990

A comparison of cognitive function in community-dwelling and institutionalized old people of normal intelligence.

Two carefully matched groups of normal old people living in institutions or in the community were administered a neuropsychological cognitive test battery. In general, the institutionalized group performed worse than the community group. Discriminant function analysis identified a subgroup of high-functioning institutionalized subjects whose performance more closely resembled that of the community group than the remainder of the institutionalized group. Differences between the various groups were not due to differences in IQ, age, health, or other controlled variables. The critical tests that differentiated the groups were sensitive to impaired function in frontal and medial-temporal lobe brain regions. The results suggest a complex interaction involving effects of age and environmental factors on brain function and cognition.

Aged↗
PubMed1988

Long-term memory loss in senescent rats: neuropsychological analysis of interference and context effects.

Four experiments are reported in which normal, senescent (25-27 months) and young adult (6 months) rats were tested for recall of a passive avoidance response 1 hr or several weeks after conditioning. There were no age differences at the 1-hr test, but a decrement was observed in old rats tested under standard conditions after long delays. The age-related impairment was exaggerated when additional approach training was administered in an identical apparatus between avoidance conditioning and testing. When the approach training was administered in an apparatus that contrasted markedly from the original, no age differences were observed. It was concluded that increased susceptibility to interference and contextual factors contributed to rapid forgetting in old rats, a pattern very similar to that observed previously in young adult rats with selective lesions to the hippocampus.

Aging↗
PubMed1987

Contextual cuing and memory performance in brain-damaged amnesics and old people.

In Experiment 1, groups of Korsakoff amnesics and alcoholic controls learned a list of paired-associate words in a standard testing room or in a room with distinctive contextual features. Recall was tested 48 hr later in the same or other context. This procedure was repeated in Experiment 2 with old people living in institutions or in the community, but matched for age, health, education, and socioeconomic background. The amnesic patients and institutionalized old people, relative to their comparison groups, were more impaired in recalling the lists under standard conditions and were more responsive to contextual cuing, especially when the distinctive cues were provided during original learning. The results highlight the susceptibility to interference of Korsakoff amnesics and institutionalized old people and offer further evidence that both groups are more responsive to salient contextual cues than either young people or old people living in the community.

Aged↗
PubMed1987

The hippocampus and conditioning to contextual cues.

Two experiments are reported in which behavioral control by contextual cues was assessed in groups of rats with dorsal hippocampal (HC), neocortical (NC), or operated control (OC) lesions. Following Odling-Smee's (1975) procedure, a Pavlovian conditioning paradigm was followed in which conditioned stimuli (CSs: tone, light) predicted an unconditioned stimulus (US:footshock) always, never, or half the time. Conditioning trials took place in a small black box. Subsequently, conditioning to background contextual cues was assessed by measuring the amount of time rats spent in the black box in preference to an adjacent white one with neither CS nor US presented. In OC groups and, to a lesser extent, NC groups, conditioning to background cues was inversely related to the probability that CS predicted US. In contrast to graded contextual conditioning in control groups, the HC groups consistently showed abnormally strong conditioning to context that was at or near asymptotic level. The results, which were related to current theories of the relation between contextual stimuli and CSs, suggest that the hippocampus may play an important role in stimulus selection during learning.

Animals↗
PubMed1986

Memory as assessed by recognition and reading time in normal and memory-impaired people with Alzheimer's disease and other neurological disorders.

Three experiments are reported that examine the dissociations in performance on two tests of retention, speeded reading and recognition in young people, home-dwelling and institutionalized elderly people, and people with severe memory disorders. In Experiment 1, subjects read sentences in normal and in geometrically transformed script at initial presentation, 1-2 hr later, and again 4-14 days later. On the latter two occasions, they were required to distinguish old sentences that they had read previously from new ones. In general, the young and elderly subjects could distinguish old from new sentences at the short delay, and all but the institutionalized elderly people could do so at the long delay. Retention as measured by reading speed typically paralleled recognition performance in that those items that were recognized best were read most quickly. The dissociation between these two tests of retention is seen only in people with memory disorders. Although these people could not distinguish old from new items even at short delays (most could not even remember having seen any sentences), their retention as assessed by reading time was similar to that of the other groups. Old sentences were read most quickly, indicating retention of item-specific information, and reading time of new sentences improved, indicating the acquisition and retention of a general skill. Experiment 2 examined what type of item-specific information was retained. Young, elderly, and memory-disordered subjects studied weakly associated word pairs and sentences. A few minutes later they were tested on both recognition and speeded reading of old, new, and recombined pairs and sentences, the last being those in which words from a studied pair or sentence were recombined with words from other such pairs or sentences. The results of both retention tests indicated that young and elderly people could distinguish old from new and recombined items. People with memory disorders, however, again failed on recognition but performed normally on speeded reading. Like the other two groups, they read old items faster than either recombined or new items. In Experiment 3, similar results were obtained even when the word pairs were constructed using randomly associated items. The results of all three experiments suggest that on implicit tests of memory, such as speeded reading, people with memory disorders can be shown to have formed and retained new associations despite failing utterly on explicit tests, such as recognition, that require conscious recollection of a previous episode.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1986

Memory decline in aged rats: a neuropsychological interpretation.

Groups of old and young rats were administered a delayed alternation task in which memory for specific events was assessed over intervals ranging between 0 and 80 s. There was no age difference in performance at relatively short intervals, but old rats showed significant memory loss at longer intervals. The pattern of behavior exhibited by old rats was very similar to that seen in young rats with selective hippocampal lesions, tested in a previous experiment under identical conditions. The present results were interpreted as reflecting an integrative deficit in old animals related to the process of establishing and/or storing associations between temporally-separated events.

Aging↗
PubMed1985

The hippocampus and thalamus: their roles in short- and long-term memory and the effects of interference.

Rats with dorsal hippocampal, dorsomedial thalamic, and operated control lesions were administered a delayed alternation (DA) task in which recall was assessed over intervals ranging between 0 and 80 s, and a passive avoidance (PA) task, involving training-test delays of between 1 h and 21 days. On both tasks, hippocampal groups performed normally at relatively short intervals, but showed significant memory loss at longer intervals. Thalamic groups were generally impaired on the DA task, but performed as well as operated control groups at all intervals in the PA task. The data also indicated an exaggerated susceptibility to interference in the hippocampal groups and a loss of episodic and reference memory following hippocampal or thalamic lesions. Similarities between the performance of rats with hippocampal or thalamic lesions and comparably brain-damaged human amnesics were noted. In line with current hypotheses, it was concluded that memory loss following thalamic damage is related to a deficit in the early stages of new learning, whereas hippocampal amnesia results from impairment at a later, integrative stage in which long-term memories are formed and durably stored.

Animals↗
PubMed1984

The effects of retroactive and proactive interference on learning and memory in old and young rats.

The effects of interference on learning and memory in old and young rats were compared using a visual discrimination task. In Experiment I, discrimination training was followed by one of three interference treatments and finally by retesting on the discrimination task. There were no age differences in original learning but old rats were significantly impaired in remembering the visual discrimination when a high-interference treatment involving similar stimuli was introduced between original learning and retesting. In Experiment II, old rats were impaired on discrimination learning when the high-interference treatment was administered before discrimination training. Analysis of response patterns showed that the exaggerated susceptibility of old rats to interference effects resulted in a general behavioral inflexibility similar to that observed in young adult rats with damage to the hippocampal region.

Aging↗
PubMed1984

Dorsal bundle lesions do not affect latent inhibition of conditioned suppression.

Three experiments are reported which examine the effects of lesions of the dorsal ascending noradrenergic bundle (DB) on latent inhibition using a conditioned suppression procedure in rats. In none of the experiments did the DB lesion have any effect, despite changes in the extent of latent inhibition and in the control procedures used to assess it. The results are discussed in relation to the attentional theory of DB function.

Animals↗
PubMed1984

Amnesia in a patient with bilateral lesions to the thalamus.

A case of anterograde amnesia is described in a 38-yr-old man with bilateral thalamic lesions. The patient appeared to have suffered no general intellectual loss and performed normally on standard memory tasks involving immediate recall of new material. There was, however, consistent impairment in recalling material, verbal and non-verbal, over delays as brief as a few seconds. Impairment was especially marked on tests involving free recall and partial cueing procedures; recognition memory was also impaired. Premorbid memory tested normally and susceptibility to interference was less than in other organic amnesics. Various interpretations of the patient's amnesia were considered but a deficit at the initial stages of information processing appeared to be indicated.

Adult↗
PubMed1984

The hippocampus, context, and information processing.

Two experiments are described in which groups of rats with bilateral hippocampal lesions, cortical lesions, and operated controls are compared on tests of discrimination learning, retention, and reversal learning. Experiment 1 examined the effects of varying prior training and context on new learning. Experiment 2 used a transfer paradigm to compare extent of original learning by hippocampal and control groups in a discrimination task involving multiple discriminanada . The major findings were that rats with hippocampal damage were less efficient at processing information and were more constrained by contextual influences than control rats.

Animals↗
PubMed1983

The hippocampus, collateral behavior, and timing.

Rats with hippocampal lesions (HC), cortical control lesions, or sham operations were trained to lever press on a differential reinforcement of low rates (DRL) schedule requiring 12 sec between responses. In four experiments, factors affecting performance efficiency in this paradigm were manipulated. Providing extra opportunities for collateral mediating behavior (Experiment 1) aided all groups nondifferentially. Adding a limited hold (Experiment 2) or administering chlordiazepoxide HCl (Experiment 3) reduced DRL efficiency in all groups nondifferentially. However, adding an auditory stimulus marking the halfway point in the DRL requirement (Experiment 4) differentially aided the HC group. The implications of these findings for different theories of hippocampal function are discussed.

Animals↗
PubMed1983

Paired-associate learning in institutionalized and noninstitutionalized old people: an analysis of interference and context effects.

Groups of old people were impaired, relative to young adults, on a test of negative transfer involving lists of paired-associate words. Susceptibility to interference effects were greater in old people living in institutions than in old people living in their own homes. The effects of varying contextual cues on performance on this task were also assessed. All participants, regardless of age, benefitted from manipulations that were intrinsic to the task (e.g., relatedness of paired associates), but only the institutionalized aged responded to extrinsic contextual manipulations (e.g., environmental changes). In general, the performance of institutionalized old people resembled that of brain-damaged amnesic patients tested under similar conditions; old people living at home generally behaved more like normal, young people. The results were discussed in terms of specific age differences in cognitive function, declining brain function, and possible selective effects of institutionalization.

Adult↗
PubMed1982

Radial-arm-maze behavior by rats with dorsal hippocampal lesions: effect of cuing.

Rats with bilateral dorsal hippocampal lesions were impaired when tested on standard (non-cued) versions of the radial arm maze, but other hippocampal groups performed almost as well as cortical and operated control groups when salient visual cues were added to each arm. Preoperative training on the non-cued, but not the cued, maze interfered with the benefits of postoperatively cuing hippocampal groups. Control groups performed equally well under all cuing and training conditions. Procedures that eliminated response sequencing did not affect performance of hippocampal or control groups. The results were interpreted as reflecting hippocampal involvement in mediating spatial cues but not necessarily along the lines predicted by cognitive map theory. It is suggested that deficits animals with hippocampal lesions represent one manifestation of a general impairment in processing information.

Animals↗
PubMed1981

The effect of cuing on release from proactive interference in korsakoff amnesic patients.

Korsakoff amnesic and alcoholic control patients were asked to recall successive lists of nine nouns of the same category. The expected progressive decrease in recall was reversed by a category shift on the fifth list for controls but not for amnesics. A context shift on the fifth list (changed color of words and background) led to improved performance by amnesics but not by controls. However, amnesics did show "release from proactive interference" at category shift if it was the second shift in a sequence (on trial nine) or if they were told to expect the shift. These findings relate amnesics' known vulnerability to proactive interference to an impaired use of available cues to segregate new from old material--unless the cues are made additionally salient. This difficulty could operate both during learning and at retrieval.

Alcohol Amnestic Disorder↗