Workshop: Hippocampal cellular activity and spatial cognitive processing

The following five papers discuss hippocampal cellu­ lar activity in freely behaving rats as it relates to spatial cognitive processing. They were presented at a workshop at the 1988 Meeting of the Society for Neuroscience in Toronto (Best & Ranck 1988). The hippocampus is an area of the brain that has received a great deal of attention recently because of its obvious involvement in higher cognitive processes. Some of the memory disturbances and disorientation seen in senile dementia of the Alzheimer's type seem to be due, in part, to damage to the hippocampus and its connec­ tions (Solomon, Pomerleau, Bennett, James, & Morse, in press). Similar memory and information-processing dis­ turbances are seen in other patients with damage to the hippocampus and/or its connections with the rest of the brain (Zola-Morgan, Squire, & Amaral, 1986). Many recent animal studies on the role of the hip­ pocampus in cognition have focused on the role of this brain structure in the processing of spatial information. Higher animals navigate effectively about their environ­ ment by keeping track of where they are relative to im­ portant places in their environment. As they move toward or away from one particular place in the environment, they have the ability to register how that movement modi­ fies the directions and locations of other important places. This registration of allocentric space is not a trivial problem. It requires complex cognitive processing. Le­ sions of the hippocampus or its major connections dis­ rupt this ability, and, more surprisingly, certain neurons in the hippocampus-the pyramidal cells-show evidence that they are involved in the processing of this infor­ mation. The first suggestion that the hippocampus may be in­ volved in processing information about the location of an organism in its environment came from a study by O'Keefe and Dostrovsky (1971), who reported that the activity of individual hippocampal neurons was related to the location or "place" of the animal in the environ­ ment. These cells frred selectively in one location or place in the test environment. John O'Keefe was not oniy the first to recognize the relationship between the cell' s ac­ tivity and the animal's location in space, but he and Lynn Nadel provided a theoretical framework with which to study "place-cell behavior" and the behavioral effects of Iesions of the hippocampus and its connections, in their now classic book, "The Hippocampus as a Cognitive Map" (O'Keefe & Nadel, 1978). Although many of us found the observation and the the­ oretical model interesting, our original reaction ranged from healthy skepticism to sarcastic cynicism. The incor­ poration by O'Keefe and Nadel (1978) ofthe many studies of the behavioral effects of hippocampal lesions into the cognitive map theory gained credibility and acceptance prior to the belief in place-cell activity. Most notably, Abe Black joined the "spatial" camp (see Black, Nadel, & o 'Keefe , 1977), and those who were not ready to accept the cognitive map theory were at least not ignoring it. However, none of us who were recording from hippocam­ pal neurons even bothered to attempt to replicate O'Keefe and Dostrovsky's (1971) results. Other labs were examin­ ing the relationship between hippocampal cellular activity and leaming and memory (Berger, Clark, & Thomp­ son, 1980; Best & Best, 1976), sleep and arousal (Mays