Hippocampectomy and feature-positive discrimination

Attention, configuration, and hippocampal function

“…The top panel of Figure 5 demonstrates that normal, HPL, and CL cases, but not the HFL case, exhibit feature-positive discrimination. These results are in agreement with Loechner and Weisz's (1987) data showing that acquisition of feature-positive discrimination is impaired in HFL animals when CS 2 is more salient than CS 1 . Although not shown in the figure, the model also correctly predicts that feature-positive discrimination is preserved in HFL, HPL, and CL animals when CS 1 is more salient than CS 2 (Schmajuk and Buhusi, in press).…”

Cell assemblies, coherence, and corticohippocampal interplay

“…But they would contribute only a small fraction to the total information stored in cortical cell assemblies. As discussed in more detail by Miller (1991Miller ( , 1993 and Kuroda (1991), this idea is compatible with many experimental and clinical observations (e.g., Kimble, 1963;Gaffan, 1974Gaffan, , 1977O'Keefe and Nadel, 1978;Olton et al, 1979Olton et al, , 1980Hirsh, 1980;Winocur, 1980;Weiskrantz, 1982;Mishkin et al, 1984;Rawlins, 1985;Aggleton et al, 1986;Squire, 1986Squire, , 1987Loechner and Weisz, 1987;Parkinson et al, 1988;Squire et al, 1988;George et al, 1989;Ridley et al, 1989;Sutherland and Rudy, 1989;Sutherland and McDonald, 1990), but also related to other theoretical models for the hippocampus (e.g., Marr 1971 ;Wickelgren, 1979Wickelgren, , 1992McNaughton, 1988;Miller 1989Miller , 1993. For example, anterograde amnesia, which is typically induced by hippocampal lesions in humans, is a loss of the ability to store new information that is typically complex and multimodal and thus might require the recruitment of "chunking" subassemblies in cortical association areas.…”

Perirhinal cortex lesions impair simultaneous but not serial feature-positive discrimination learning.

“…For example, Loechner and Weisz (1987), using nictitating membrane conditioning with rabbits, showed that hippocampal lesions impair simultaneous feature-positive discrimination (A− /XA+), but only when A was more salient than X. It is unlikely that stimulus salience or overshadowing interfered with the lesion-induced deficit in the acquisition of simultaneous feature-positive discrimination in the present study because the stimulus modalities were counterbalanced and produced the same CR percentage when presented as the target stimulus (A).…”