Biomedical subjects

R D McKee

Publications and source records attributed to R D McKee.

4 recordsLinked to original sources

PubMed1995

The deferred imitation task as a nonverbal measure of declarative memory.

We tested amnesic patients, patients with frontal lobe lesions, and control subjects with the deferred imitation task, a nonverbal test used to demonstrate memory abilities in human infants. On day 1, subjects were given sets of objects to obtain a baseline measure of their spontaneous performance of target actions. Then different event sequences were modeled with the object sets. On day 2, the objects were given to the subjects again, first without any instructions to imitate the sequences, and then with explicit instructions to imitate the actions exactly as they had been modeled. Control subjects and frontal lobe patients reproduced the events under both uninstructed and instructed conditions. In contrast, performance by the amnesic patients did not significantly differ from that of a second control group who had the same opportunities to handle the objects but were not shown the modeled actions. These findings suggest that deferred imitation is dependent on the brain structures essential for declarative memory that are damaged in amnesia, and they support the view that infants who imitate actions after long delays have an early capacity for long-term declarative memory.

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PubMed1993

On the development of declarative memory.

In the visual paired-comparison task, which has been used to demonstrate memory abilities in human infants, Ss view pairs of pictures and then view new pictures paired with old ones. Memory is demonstrated when Ss spend more time looking at new pictures than at old ones. In a series of studies involving amnesic patients and normal Ss, the authors evaluated what kind of memory is exhibited in this task. The results suggest that performance ordinarily depends on the brain structures essential for declarative memory. These and other findings suggest that the visual paired-comparison test also depends on declarative memory when the task is given to human infants. Thus, successful performance on this task by infants probably reflects an early capacity for declarative memory. The relevance of these findings to the phenomenon of infantile amnesia is discussed.

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PubMed1993

Declarative and nondeclarative memory in opposition: when prior events influence amnesic patients more than normal subjects.

Amnesic patients and normal subjects read the names of nonfamous persons. Then, after being told that all the names were nonfamous, subjects judged the fame of names on a mixed list of new famous names, old nonfamous names, and new nonfamous names. Finally, they took a recognition memory test involving old and new nonfamous names. In this way, declarative (explicit) memory and nondeclarative (implicit) memory were placed in opposition. That is, recollection that a name had been recently presented (and was therefore nonfamous) opposed the facilitatory effect by which prior presentation ordinarily increases the tendency to judge that name as famous. Normal subjects exhibited good recognition memory and no fame-judgment effect--that is, no difference in fame judgments for new and old nonfamous names. By contrast, for the amnesic patients recognition memory was poor, but a strong fame-judgment effect occurred--that is, amnesic patients judged old nonfamous names as famous. The results provide additional evidence that the fame-judgment effect is supported fully by nondeclarative (implicit) memory and is independent of the limbic/diencephalic brain structures damaged in amnesia.

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PubMed1992

Equivalent forgetting rates in long-term memory for diencephalic and medial temporal lobe amnesia.

Amnesia can result from damage to either the midline diencephalon or the medial temporal lobe. An important related question has been whether these two forms of amnesia result in similar or different kinds of memory impairment. Earlier studies raised the possibility that differences might exist in the rate of forgetting within long-term memory, specifically, that the forgetting rate is normal in diencephalic amnesia but abnormally rapid in medial temporal lobe amnesia. In the present study, forgetting was studied in five amnesic patients with damage to the medial temporal lobe, six amnesic patients with damage to the diencephalon, and 10 normal subjects. One hundred twenty pictures were presented to the control subjects for 1 sec each and to the amnesic patients for 8 sec each. Retention was then tested after 10 min, 2 hr, and 30-32 hr using four different procedures for testing recognition memory. The different exposure times for the pictures succeeded in matching the performance scores of both groups of amnesic patients and the control subjects at the 10 min retention interval. Both groups of amnesic patients also performed similarly to control subjects at retention delays of 2 hr and 30-32 hr. In addition, performance was nearly identical, regardless whether recognition memory was assessed by asking subjects to select the new items or the old items. The findings emphasize the similarities between medial temporal lobe and diencephalic amnesia.

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