9. Hippocampus 1

functions associated with the hippocampus

rapid place and declarative learning

behavioural control, including emotional, motivational and sensorimotor functions

what memory is affected by hippocmpal damage

declarative memory: especially episodic memory whilst semantic memory remains often quite intact)

place memory

contextual memory

limitations to human case studies re hippocampal lesions

damage often not specific/hard to ensure that it is specific

patients often have other problems e.g. H.M. also had epilepsy and was on medication for this

what is the complementary learning systems theory?

the hippocampus mediates rapid learning of place and declarative information, whilst extra-hippocampal (neocortical) sites can mediate slow incremental learning of such information. like this, the two goals of rapidly learning about specific experiences and of extracting generalities from routine experiences can be reconciled

describe the neuroanatomical basis of hippocampal learning

studies suggest the entorhinal cortex (part of the mediofrontal lobe) is important funnel of sensory information into the hippocampus.

the cortices of all sensory modalities interact with the hippocampus and the entorhinal cortex which then gets passed on to the hippocampus

entorhinal cortex controls what can get integrated into the hippocampus and into memory representations

what is Hebb’s hypothesis re hippocampal learning

long lasting change in the strength of the connections (synapses) between neurone is the physiological basis of lasting memory

synapses between neurone are strengthened when the neurone are active together: ‘neurons that fire together, wire together’

link between hippocampal overactivity and atrophy in schizophrenia

continuous overactivity can lead to excitotoxic cell damage - wearing neurone out- leads to neuronal atrophy/damage

if this occurs in early stages, it could lead to the reduced volume of hippocampus - causal link between overactivity causing reduced volume in later stages

relation between hippocampal dysfunction and schizophrenia symptoms - particularly hippocampus dependent memory

overactivity in hippocampus could lead to memory deficits

if neutrons are too ‘trigger happy’ and fire in response to irrelevant stimuli, this could disrupt memory

balanced neural activity is what is important

SZ patients show impairments in hippocampal-dependent learning

how may hippocampal dysfunction contribute to other functional impairments characterising schizophrenia

abnormal interactions between hippocampus and sensory association cortices may cause sensory hallucinations