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
16
Q
Scoville + Milner 1957 / Milner 1968
A
- HM had intact procedural learning e.g. mirror drawing
- also intact priming, both perceptual e.g. Gollins picture task and semantic e.g. word association
17
Q
Cohen + Squire
A
distinction between declarative and procedural memory
18
Q
Baddeley + Warrington (1970)
A
STM vs LTM
19
Q
Squire + Zola-Morgan 1991
A
- HC lesioned monkeys impaired on DNMTS task (except for very short delays)
- showed RA gradient for associations before lesion
- can still acquire procedural skills (independent of MTL)
20
Q
Roof 1993
A
Gender-specific impairment on Morris water maze task after entorhinal cortex lesion
21
Q
Yin 2004
A
anterior vs posterior striatum lesions - only anterior impaired
22
Q
Hallock (2013)
A
- conditional discrimination T maze: turn left if mesh, right if wood (simple association between cue and spatial location, learned as habit)
- delayed spatial alternation T maze: remember last trial and choose alternate arm
- transiently inactivated either dorsal striatum or dorsal HC using muscimol
- inactivation of striatum (but not HC( impaired CD task while inactivation of HC (but not striatum) impaired DA task performance
- double dissociation between roles of DS and DH in each task
23
Q
Sternberg (1966)
A
- mean RT for digit span increases by 38 ms per digit added (length of gamma cycle so time-matched)
- serial scanning mechanism (must scan whole list)
- MEG recordings: theta power increases incrementally with task load, but doesn’t increase once limit of 7 has been reached
- supports role of theta in maintaining WM
24
Q
theta + gamma
A
- single items in an episodic memory e.g. components A-G activated sequentially as a “fast” list on different gamma cycles (30-80Hz)
- 7 +/- 2 gamma cycles on each theta cycle (Ebbinghaus STM capacity)
- theta cycles (4-10 Hz, slow list) with repeated activation of A-G on each one = represent complete episodic memory
represents STM encoding at cellular level - as rat moves through place field, place cell fires earlier and earlier in theta phase i.e. phase-specific firing
- centre of place field = fires at trough (time of firing dictates location)
- theta phase precession and population code = predict exact location from temporal code
25
Q
Sutherland (1989)
A
- associations between memories relies on MTL
- trained on paired associates, one rewarded and one not, e.g. AB pair = A rewarded, B not
- then present novel pair BD (but both individual components have appeared before and been rewarded depending on situation and rat has memory of this) = tests transitive interference. should choose B as rewarded over C whereas D is not (AE doesn’t need transivity as A always rewarded and E never rewarded)
- lesion HC (fornix) or paraHC or perirhinal cortices = impair transivity for BD, but AE fine
- rat can still make associations / memories, but cannot compare episodic memories to produce relational behaviour
26
Q
Rempel-Clower (1996)
A
- RB, LM, WH
- more extensive damage = more severe AA + RA goes back further
- STM/LTM distinction
- also declarative/non-declarative distinction
27
Q
Aggleton (1996)
A
HC damage = impaired explicit recall (but recognition okay)
28
Q
Bowles (2007)
A
no HC damage but damage to perirhinal + entorhinal cortices = impaired familiarity but normal recall
29
Q
Moscovitch (2016)
A
- regularities of memories stored in neocortical traces and bound together in relational representations mediated by the MTL
- explains why memories can be triggered by situations which have similar elements to a stored memory
- as memories become older and more remote, they become more semantic / abstract and rely less on MTL
MTL damage = no memory traces are transferred to neocortex to be stored long-term
30
Q
Alvarez (1994) + Lynch (2004)
A
models of LTP / consolidation by MTL
31
Q
Kan (2007)
A
- cued recognition paradigm
- controls showed enhanced performance for same-cue as opposed to different-cue items but amnesics did not, even when they managed to show single item recognition
- suggests the HC is required to bind together information to form relational memory
32
Q
Verfaellie (2017)
A
- relational memories are more stable than familiarity info processed in perirhinal cortex and tend to be forgotten through decay rather than interference
- semantic memory can be more well-preserved than episodic memory in amnesics
33
Q
Dewar 2010
A
- HC lesions = increased interference effects
34
Q
Hales (2014)
A
- MEC lesions only partially disrupt HC place cells and specific types of HC-dependent memory
- bilateral lesion of whole MEC in rats caused lower proportion of active HC cells
- remaining cells had place fields but had decreased spatial precision and decreased long-term stability
- impaired on morris water maze task (like HC lesioned rats)
- combined MEC and HC lesion = even more impaired
- MEC lesioned rats not impaired on other HC-dependent tasks e.g. those where object location or context was remembered
- MEC input not required for all types of spatial coding / HC-dependent memory, but is necessary for normal acquisition of place memory
