CA1

CA1, short for Cornu Ammonis area 1, is a subfield of the hippocampus, a key structure of the limbic system located in the medial temporal lobe. It lies along the longitudinal axis of the hippocampus, between CA2/CA3 and the subiculum, and is a component of the hippocampal formation that participates in memory processing. The CA1 region is composed primarily of pyramidal neurons distributed across the strata oriens, pyramidale, radiatum, and lacunosum-moleculare. Its pyramidal cells receive major excitatory input from CA3 via the Schaffer collateral pathway and also receive direct input from the entorhinal cortex via the temporoammonic pathway, which terminates in the distal dendrites. CA1 neurons project predominantly to the subiculum, with additional projections to other cortical and subcortical areas through the entorhinal cortex.

Functionally, CA1 is involved in the encoding and retrieval of episodic memory and plays a role in the temporal organization of experiences and spatial navigation. It supports synaptic plasticity, including NMDA receptor–dependent long-term potentiation, which is a widely studied model of memory mechanisms. Electrophysiological activity in CA1 is associated with theta rhythms during navigation and memory tasks, and CA1 place cells contribute to spatial representation.

Clinical relevance: CA1 shows high vulnerability to hypoxic-ischemic injury and is affected in various conditions such as Alzheimer's disease and temporal lobe epilepsy. Because of its pivotal position in the trisynaptic circuit, CA1 is a frequent focus of research on memory formation and hippocampal diseases. In addition to neuroscience, the acronym CA1 may appear in other contexts, but in scientific literature it most commonly denotes this hippocampal subfield.