Learning, Memory and Amnesia: Memory
- Created by: meg_lou
- Created on: 25-04-17 15:53
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- Memory
- Interesting Cases
- KC
- Motorbike accident resulting in brain damage, including MTL
- Severe amnesia for personal experiences (episodic)
- All other cognitive abilities intact e.g. playing card games
- RB
- Botched cardiac bypass surgery
- Suffered cerebral ischemia - disruption of blood supply to the brain
- Postmortem showed damage to just the CA1 subfield of the hippocampus
- Hippocampaldamage alone can cause MTLA
- KC
- Neurobiology of Memory
- Maguire et al. (2000)
- MRI scans of taxi drivers and controls
- Correlation between time spent as taxi driver and volume of posterior hippocampus
- Extensive practice on spatial navigation affects the hippocampus
- Hippocampus
- Plays a key role in memory for spatial location
- Hippocampallesions cause deficits on spatial tasks e.g. Morris water maze
- Rats placed in murky water learn to swim to a platform below the surface
- Hippocampallesions cause deficits on spatial tasks e.g. Morris water maze
- Place cells respond when a subject is in specific location
- Each place cell has a place field for a part of the environment
- Fires only when in that environment
- Each place cell has a place field for a part of the environment
- Grid cells are found in the entorhinal cortex
- Array of evenly spaced place fields producing a pattern
- Even spacing of the place fields could provide more information for place cells
- Array of evenly spaced place fields producing a pattern
- Plays a key role in memory for spatial location
- Cognitive map theory
- Hippocampus constructs and maintains allocentric maps of the external world from the sensory input it receives
- Allocentric - representations of space based on relations between external objects
- Firing of place cells doesn't just depend of spatial location
- Hippocampaldamage sometimes impairs performance on tasks without spatial component
- Large and complex so unlikely to have a single function
- Hippocampus constructs and maintains allocentric maps of the external world from the sensory input it receives
- Memory storage
- Memories stored where in the brain structures involved in its formation
- Hippocampus - spatial location
- Perirhinal cortex - object recognition
- Mediodorsal nucleus - Korsakoff's symptoms
- Basal forebrain - AD symptoms
- Damage to structures results in memory deficits
- Inferotemporal cortex - visual perception of objects
- Amygdala - fear learning
- Prefrontal cortex - working memory
- Cerebellum - sensorimotor skills, striatum - habit formation
- Memory consolidation
- Hebb - memories of experiences stored in the ST by neural activity circulating in closed circuits
- Studied by administeringECS
- Length of period of RA produced by it provides an estimate of time needed for consolidation
- Studied by administeringECS
- Standard consolidationtheory (Moscovitch et al., 2006)
- Memories temporarily stored in hippocampusuntil transferred to a more stable cortical storage system
- Retained memories become more resistant to disruption by hippocampusdamage
- Each time a similar experience occurs, a new engram is established and linked to the original engram
- Each time a memory is retrieved from LTM it is held in unstable STM
- Susceptible to amnesia until it is reconsolidated
- Hebb - memories of experiences stored in the ST by neural activity circulating in closed circuits
- Maguire et al. (2000)
- Synaptic Mechanisms of Learning
- Long-term potentiation
- Facilitation of synaptic transmission after high-frequency electrical stimulation to presynaptic neurons
- Can last many weeks and occurs only if presynaptic firing is followed by postsynaptic firing
- LTP effects structures in learning and memory
- Behavioural conditioning can produce LTP like changes in hippocampus
- LTP can be elicited by low levels of stimulation that mimic normal neural activity
- 3 part process
- 1. Induction (learning)
- Simultaneously, glutamate must bind to NDMA receptor and postsynaptic neuron must be partially depolarised
- Allow release of calcium ions
- Simultaneously, glutamate must bind to NDMA receptor and postsynaptic neuron must be partially depolarised
- Maintenance (memory) and expression (recall)
- Involve changes in both pre and post synaptic neurons
- 1. Induction (learning)
- Long-term potentiation
- Interesting Cases
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