entorhinaltoCA1

EntorhinaltoCA1 refers to the direct synaptic connection from the entorhinal cortex to the CA1 region of the hippocampus, a major component of the hippocampal formation that links neocortical input to hippocampal processing. This pathway, along with indirect hippocampal circuits, supports memory formation, spatial navigation, and contextual processing.

Anatomy and pathways: The entorhinal cortex provides two principal routes to the hippocampus. The perforant pathway from entorhinal layer II projects to granule cells in the dentate gyrus and to CA3 (indirect route). In addition, layer III neurons send a direct projection to CA1 in the stratum lacunosum-moleculare, forming the temporoammonic pathway. The entorhinal cortex contains medial (MEC) and lateral (LEC) subdivisions, with MEC primarily contributing spatial and directional information and LEC conveying object- and context-related information. CA1 integrates inputs from entorhinal cortex and CA3, and serves as a convergence site for cortical and hippocampal signals.

Function: The temporoammonic TA-CA1 input is thought to contribute to episodic memory formation and contextual associations by delivering cortical information directly to CA1. CA1 neurons then relay processed signals to downstream targets, participating in theta-band activity and synaptic plasticity processes such as long-term potentiation, which support memory encoding and retrieval.

Clinical relevance: Early dysfunction of the entorhinal cortex and its projections to CA1 is observed in aging and Alzheimer’s disease, correlating with memory impairment. Experimental disruption of the TA-CA1 pathway in animal models can impair memory encoding and retrieval, underscoring its role in hippocampal-dependent learning.