memory systems Flashcards
1
Q
O’Keefe and Nadel (1976)
A
- place cells in HC fire when animal moves over place field
- positional and contextual information
- form basis of cognitive map
- allocentric (whereas egocentric coded for by cells outside HC e.g. grid)
population activity of HC place cells encode whole environments - formed basis of argument that HC was selectively specialised for processing of spatial info, as HC was required for spatial tasks but not non-spatial
- although, some of these studies also differed in not just spatial/nonspatial but also relational/flexible memory vs rigid/response-only memory
- research now shows that HC is also required for nonspatial aspects of episodic memory (e.g. Eichenbaum 2000)
2
Q
Wilson 1993
A
- recordings from 80 CA1 neurons
- well-defined place fields
3
Q
Eichenbaum 2000
A
- HC not just for spatial navigation!
- damage to HC impairs both spatial and nonspatial info
- T maze spatial alternation task: most HC cells that fired to location on arm of T (common area) only fired if subsequent turn was in specific direction i.e. either left or right
- so also encodes non-spatial aspects of events e.g. intended direction of movement
separate HC networks encode sequences of behaviours and places separately for left and right turns - episode-specific encoding of aspects including spatial location = “memory space”
- consistent with neuropsychological findings that show HC is required for factual info in memory episodes
4
Q
Kesner (2005)
A
- rats learned to associate objects with reward, separated by temporal gap
- CA1 lesion impaired associations between objects over time (CA3 lesion had no effect)
5
Q
Eichenbaum (2017)
A
- plasticity mechanisms of highly interconnected HC circuits integrate events that neighbour in space and time
- creates continuous mapping of adjacent elements that have proximity in space (place cells), time (time cells) or both at same time
- HC network creates maps of arbitrary spaces by adding neurons that code for specific events
- elements are linked when they occur together, and linkages extended between elements that have similar attributes (allows for relational memory)
- these direct and indirect associations form basis of complex memory space where memories are linked in space, time, context etc
- space and time initially processed by overlapping brain networks and coded in different scales but then signals are integrated in HC to create spatiotemporal organisation of memory
6
Q
Moscovitch (2017)
A
component process model
- during perception, MTL integrates objects and contexts, and objects bound together in HC via spatiotemporal context
- during encoding, part of representation is transferred to long-lasting format in HC and neocortex (supported by schematic relational processes in vmPFC and semantic processes in vlPFC)
- during retrieval, integrated event representations in HC are activated which reactivate MTL and cortex representations etc (explains how similar / adjacent memories can reach consciousness)
= creates multidimensional memory trace / engrams
7
Q
Eichenbaum (2014)
A
- HC time cells that fire at successive moments in temporally structured experiences
- not caused by external events, specific behaviours or spatial dimensions of an experience
- instead represent flow of time within a specific memory
- provide additional dimension that is integrated with spatial mapping etc, helps organise elements of an event into coherent memories i.e. combine time and space
- so episodic memory involves embedding a record of events in a representation of spatiotemporal context
8
Q
Libby (2014)
A
- fMRI showed HC activity patterns predicted accurate memory for specific object-location relationships
- demonstrates HC role in spatial memory
9
Q
Lehn (2009)
A
- subjects recalled order of movie scenes
- strong fMRI activation in HC related to retrieval of temporal order (and predicted accuracy)
10
Q
Kyle (2015)
A
- virtual reality game where subjects visited stores in specific spatial layout and in particular temporal order
- made near or far judgements either related to spatial layout / distance, or how close they were in temporal order
- comparable levels of activity throughout HC so space and time both processed throughout / not localised to particular regions of HC
- but space and time judgements were characterised by distinct patterns of neural activity, so suggests they are processed via different neural networks within HC
11
Q
Packard + McGaugh (1996)
A
- rats trained on T maze = place strategy when tested after 1 week
- overtrained = response strategy
- so initially, place memory and cognitive map guided acquisition of memory (learning task) then switched to response memory as habit developed
- lidocaine into HC abolished place memory
- lidocaine into striatum abolished “response” memory in week 2 (but still could do task as could use place memory)
12
Q
cued radial arm (olton) and morris water mazes
A
- use response strategy if they are cued e.g. with a light (associative learning only)
- not impaired by HC lesion
13
Q
Cook + Kesner (1988)
A
- rats with striatum lesion = impaired on response tasks e.g. visual discriminant water maze, or turning right on arm of maze through habit
- normal performance on place tasks using cognitive map e.g. normal radial arm maze / spatial discriminant water maze
14
Q
Kernadi (1995)
A
- monkeys trained to follow certain sequence of dots then repeat pattern by fixating each location in order of presentation, then reaching to target position
- some striatal neurons respond to particular location but only within certain sequence
15
Q
Thompson (1994)
A
- rabbit pavlovian eye blink conditioning
- tone/light (CS) then air puff to eyelid (US) = reflexive eye blink (UR)
- several CS-US pairings = CR to CS
- lesion interpositus nucleus in cerebellar cortex = CR not learnt
- inactivation of red nucleus (between cerebellar cortex and motor cortex) = CR learnt but can’t be produced until inactivation reversed (only prevents motor output from cerebellum to cortex)
association builds up in cerebellum and feeds out to motor nuclei
