Based on behavioral procedures aimed at measuring working or data-based memory for spatial location, response, and visual object information, it is shown that there is a triple dissociation among the hippocampus, caudate nucleus, and extrastriate visual cortex in mediating spatial location, response, and visual object information, respectively. The hippocampus appears to subserve only spatial location, the caudate nucleus only response, and the extrastriate visual cortex only visual object information. The results support the neurobiological foundation of the attribute memory model.

Since the hippocampus is likely to be a major site of phencyclidine (PCP) action, the effects of various doses of PCP (1.8, 18 or 36 nM) as well as 3.6 nM MK-801 or saline injected directly into the dentate gyrus of the hippocampus was tested for acquisition of a spatial navigation task (dry land version of a water maze) using a paradigm that assesses short term memory based on learning within a day and long term memory based on learning between days. Results indicated that relative to saline or 1.8 nM PCP injected rats, rats with 18 or 36 nM PCP or 3.6 nM MK-801 injections were impaired in acquisition of the task as measured by increased distances traveled to find the food location between days but not within days. In additional experiments 36 nM PCP or 3.6 nM MK-801 did not produce any deficits in the acquisition of an object discrimination task. It is suggested that PCP through its blocking action of the NMDA receptor in the dentate gyrus or CA1 region of the dorsal hippocampus mediates the consolidation of new spatial location information.

In the first experiment rats with 1, 2, 3 or 4 mg/kg phencyclidine (PCP), or saline injections were tested for acquisition or retention of a cheese board spatial task (dry land version of a water maze). Results indicate that relative to controls or rats with injections of 1 and 2 mg/kg PCP, rats with 3 or 4 mg/kg PCP injections were impaired in acquisition and retention of the task as measured by increased distances traveled to find the correct food location. This impairment was primarily observed in between days but not within days performance. In the second experiment rats with 4 mg/kg PCP or saline injections were tested for memory performance of a delayed spatial matching-to-sample task. Results indicate that relative to controls rats with 4 mg/kg PCP injections were not impaired at either 1-5 or 30 s delays. It is suggested that PCP through its blocking action of the NMDA receptor mediates long- but not short-term memory for spatial location information as well as the ability to retrieve previously learned spatial location information.

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