Hippocampus

The hippocampus is primarily responsible for consolidating new declarative memories — converting recently formed memories into stable long-term storage — and for spatial navigation. It plays a key role in both episodic memory (memories of specific events) and semantic memory (general knowledge). It works closely with the prefrontal cortex during encoding and retrieval, and with the amygdala during emotionally significant experiences.

Damage to the hippocampus typically produces anterograde amnesia — the inability to form new long-term explicit memories — while leaving older memories and procedural skills largely intact. This pattern was most clearly demonstrated in Patient H.M., whose bilateral hippocampal removal in 1953 left him unable to remember any new events day to day for the rest of his life, despite normal intelligence and intact short-term memory.

Yes. Research by Eleanor Maguire and colleagues at University College London found that the posterior hippocampus of London taxi drivers was significantly larger than in non-drivers, and that this enlargement correlated with years of navigational experience — demonstrating activity-dependent structural plasticity in the adult human brain. The hippocampus is one of the few brain regions known to support neurogenesis (the birth of new neurons) in adults, though the extent of human adult neurogenesis remains debated.

The hippocampus is highly sensitive to glucocorticoids (stress hormones such as cortisol), which it expresses in large quantities via glucocorticoid receptors. Chronic stress and prolonged elevated cortisol are associated with hippocampal atrophy in both animal models and humans. Reduced hippocampal volume has been consistently observed in post-traumatic stress disorder (PTSD) and major depression, though it remains debated whether this is a consequence of stress or a pre-existing vulnerability.