The study investigates the minimal volume and location of hippocampal tissue required for spatial learning. Using ibotenic acid to create bilateral lesions of varying sizes (20-100% of hippocampal volume), researchers found that even a small transverse block (minislab) of the hippocampus, specifically at the septal (dorsal) pole, was sufficient to support spatial learning in a water maze. Lesions of the septal pole, leaving 60% of the hippocampus intact, caused a learning deficit, despite normal electrophysiological responses, synaptic plasticity, and preserved acetylcholinesterase staining. This suggests that hippocampal-dependent spatial learning only requires a minislab of dorsal hippocampal tissue. The findings also indicate that spatial learning can be performed by minislabs oriented in the lamellar plane and located at either the septal pole or closer to the border between the dorsal and ventral halves of the hippocampus. These results support the idea that the hippocampus functions as a distributed memory system and that spatial learning may not be locked to a specific group of cells within the dorsal hippocampus.The study investigates the minimal volume and location of hippocampal tissue required for spatial learning. Using ibotenic acid to create bilateral lesions of varying sizes (20-100% of hippocampal volume), researchers found that even a small transverse block (minislab) of the hippocampus, specifically at the septal (dorsal) pole, was sufficient to support spatial learning in a water maze. Lesions of the septal pole, leaving 60% of the hippocampus intact, caused a learning deficit, despite normal electrophysiological responses, synaptic plasticity, and preserved acetylcholinesterase staining. This suggests that hippocampal-dependent spatial learning only requires a minislab of dorsal hippocampal tissue. The findings also indicate that spatial learning can be performed by minislabs oriented in the lamellar plane and located at either the septal pole or closer to the border between the dorsal and ventral halves of the hippocampus. These results support the idea that the hippocampus functions as a distributed memory system and that spatial learning may not be locked to a specific group of cells within the dorsal hippocampus.