Localisation of memory Chapter 28

Memory Brain’s capacity to retain & retrieve info Versatile – sights, sounds, smells etc Large capacity – experiences stored for a lifetime Declarative memory (‘remembering that’): Recall of personal or general facts Associated with areas of the temporal lobe Limbic system – surrounds the hypothalamus - Possesses the hippocampus Procedural memory (‘remembering how to..’): Ability to recall how to perform mental & motor skills e.g reading, playing chess, swimming, cycling etc Cerebellum very active

Localisation of memory Amnesia – partial or complete loss of memory Results from injury, surgery, disease, stroke, electrical shocks Case history – removal of limbic system Limbic system – formation & transfer of new declarative memories Temporal lobes – storage of declarative memories Cerebellum & cerebrum – storage of procedural memories Personal & general memories stored in different areas Memories of different categories stored in different areas However, many areas interconnected (constant exchange of info)

Memory at neuronal level Procedural skills not easily forgotten Many declarative memories also permanently stored Probably due to long-term change in the brain Each memory held in a ‘memory circuit’ (group of neurones) Retrieved by nerve impulses passing through & reactivating the circuit Interchange allows one memory to trigger other memories

Molecular basis of memory Memory likely based on chemical changes in neurones Certain neurotransmitters released – impulses flow through ‘memory circuits’ Increased impulses, memory is longer lasting Alzheimer’s: - abnormal tangled neurones - brain cell death - irreversible memory loss - Cells in limbic system producing acetylcholine are lost Monkeys – visually impaired if acetylcholine blocked

Molecular basis of memory (ctd.) New memories dependent on hippocampus region In this region, glutamic acid is the neurotransmitter released This binds to NMDA receptor - alters electrical state in postsynaptic membrane Long term – neurones change biochemically Proteins are synthesised – alter size and shape of postsynaptic neurone More dendrites More synapses Increased sensitivity = stronger memory