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Biomedical subjects

E Marshall

Publications and source records attributed to E Marshall.

At least 523 records · Page 29Linked to original sources
PubMed1982

Visual memory and stimulus repetition effects.

Recent investigations of memory for randomly configured patterns indicate that visual memory can involve distinct short-term and long-term components. The appearance of a visual recency effect that is confined to the last-presented item is believed to result from the active visualization of this item during the retention interval. Studies of the retention of familiar visual information have also suggested that the short-term effects observed are a result of active visualization. In a review of these studies, however, we argue that the effects obtained with familiar visual information are not necessarily a result of active visualization and, indeed, may not involve anything other than long-term visual memory. For example, Rabbitt and Vyas (1979) observed a visual recency effect in a serial choice reaction time task involving familiar information. That this recency effect was confined to the final item accords with the results obtained with unfamiliar visual information. However, this choice reaction time task did not require subjects to remember previous stimuli, so it is unlikely that they actively visualized them. With the case for a distinct short-term visual memory currently resting on the recency effect interpreted as reflecting a process of active visualization, this result is especially important. In the second part of the present paper, we report a series of experiments that provides an understanding of the visual recency effect in the serial choice reaction time task. We conclude from these studies that this effect is not due to visualization or to a visual trace either decaying or being overwritten by a succeeding stimulus.

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PubMed1981

Characterization of the nude rat (rnunz). Functional characteristics.

Gross histopathological and morphological observations in an accompanying paper confirmed the absence of a thymus and thymus-derived lymphocytes in the New Zealand athymic nude mutant (rnunz). In the present studies an analysis of the cell-mediated immune status of the rnunz rat is reported. Lymphocyte transformation studies showed that lymphocytes from the rnunz strain did not respond to mitogenic stimulation with the T lymphocyte specific mitogen Concanavalin A. This confirmed the absence of potentially functional T lymphocytes suggested by the morphological analysis. Lymphocytes from the rnunz strain also failed to initiate a graft versus host response, and the absence of host versus graft response established the immune deficit in cell-mediated immunity in the intact animals. Additionally, the rnunz strain has been used as a reference point to determine the effectiveness of neonatal thymectomy and adult thymectomy with irradiation as a means of depleting the host of T cells.

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