Lecture 8 - The remembering brain P1

Question 1

the MTL system

Answer 1

medial temporal lobe

- includes the hippocampus and three cortical structures of the entorhinal lobe

Question 2

the cortical structures of the entorhinal lobe are also referred to as:

Answer 2

the parahippocampal gyrus

Question 3

how is info organised in MTL

Answer 3

• hierarchical organisation
• info is initially collected through the perihinal and parrahippocampal cortices then to entorhinal cortex then to hippocampus

Question 4

what can the hippocampus be further divided into

Answer 4

dendate gyrus or CA subfields

Question 5

anterograde amnesia

Answer 5

difficulties acquiring new memories

Question 6

retrograde amnesia

Answer 6

difficulty remembering old memories

Question 7

The case of H.M.

Answer 7

• had severe epilepsy
• so had bilateral MTL (removed hippocampus and amygdala)
• seizures stopped
• BUT - had minor retrograde amnesia and severe anterograde amnesia.
• global amnesa : affected all sensory modalities
• problems limited to declarative/explicit memory

Question 8

HM and the digit span +1 test

Answer 8

normal subjects can do up to 18 digits
- after 25x trials, HM couldnt do more than 7 digits

(problem with transfer of info STM to LTM)

Question 9

HMs implicit memory - mirror drawing task

Answer 9

HM substantially improved after 3x days of practice

• implicit memory intact

Question 10

Wagner et al 1998 - remembered versus forgotten stimuli (aims)

Answer 10

• does the brain activity at encoding predict what items are later going to be recognised and which will be forgotten?

Question 11

Wagner et al 1998 - remembered versus forgotten stimuli - findings

Answer 11

activity in the left ventrolateral PFC and the left MTL were predictive of later remembered versus forgotten stimuli.

Question 12

Wagner et al 1998 - remembered versus forgotten stimuli - procedure

Answer 12

scanned Ps when they were studying a list of words that were subsequently tested in a recognition memory test.

after test - looked at brain activity during encoding to see if brain activity predicted which items are later going to be recognised/forgotten?

Question 13

encoding specificity hypothesis

Answer 13

events are easier to remember when the context at retrieval is similar to the context of encoding

Question 14

familiarity:

Answer 14

context-free memory in which recognised item feels familiar

Question 15

recollection

Answer 15

context-dependent memory that involves remembering specific information from the study episode

Question 16

familiarity/recollection corresponding brain region? (Eichenbaum et al 2007)

Answer 16

• the perihinal cortex processes item representations (important for FAMILIARITY)
• The parrahippocampal cortex is assumed to process ‘context’ (including scene perception)
• the hippocampus binds items in context (important for recollection)

Question 17

Ranganath et al 2004

Answer 17

fMRI study that shows hippocampal activity in recollection
- whereas familiarity selectively activated perihinal cortex

activity with the perihinal cortex was predictive of the degree of familiarity based recognition

Question 18

role of hippocampus

Answer 18

• encoding and retrieving constituent elements of an experience

e. g.
- names with faces
- locations of objects within a scene

Question 19

what is consolidation

Answer 19

process that stabilises a memory over time after it is acquired

Question 20

two types of consolidation

Answer 20

synaptic consolidation

system consolidation

Question 21

what is synaptic consolidation

Answer 21

• structural changes int he synaptic connections between neurones
• may take hours - days to complete.

Question 22

what is system consolidation

Answer 22

gradual shift of memory from hippocampus to the cortex related to declarative memory

(much slower)

Question 23

Ribots law

Answer 23

• memory loss following brain damage has a temporal gradient
• more recent memories are likely to be lost

BECAUSE: remote memories have undergone systems consolidation - so don’t rely upon MTL anymore ARE cortex-dependent.

Question 24

HM and Ribots Law

Answer 24

• HM demonstrated a degree of temporal gradient

- memories lost from 2 years prior

Question 25

patient RZ and temporal gradient

Answer 25

• had Kosakoff’s syndrome
• unable to learn new paired associates
• remembered some famous people from 1930s but not after

Question 26

two theories of system consolidation

Answer 26

standard consolidation theory : temp role of hippocampus

multiple trace theory : permanent role of hippocampus

Question 27

standard consolidation model

Answer 27

initially, the hippocampus binds the information in many regions of the brain to form coherent episode

• overtime has less of a role

Question 28

memory reacitvation (standard consolidation)

Answer 28

• reactivation is the core mechanism
• = reinstatement of patterns of neural activity in the cortex
• such reactivation subsequently results in STABILISATION and REFINEMENT of cortical traces
• this process leads to storage + recall relying solely on cortex (not hippocampus)

Question 29

retrieval of nonconsolidated and consolidated memory

Answer 29

• any event contains different elements and sensory information
• hippocampus holds together different elements to get coherent episode
• hippocampus plays a role in reactviiating all elements in the early stages of memory existence - after consolidation this is no longer necessary

Question 30

the temporal gradient in amnesia and semantic dementia

Answer 30

SD - damage to anterior temporal lobes (cortex)
AD: damage to hippocampus and related structures

SD patients can remember recent but not old events - as memories not dependent on cortex.

Question 31

Multiple Trace Theory

Answer 31

• hippocampus has a permanent role in EPISODIC memory recall
• older memories have been reactivated many times
• each reactivation creates a new trace in MTL and in other neocortical structures
• the extent that damage is not global, older memories are more likely to be remembered as they have more traces

Question 32

Gilboa at el 2004 - fMRI of remote personal memories (procedure)

Answer 32

• family members of Ps provided pictures of events
• from remote past to more recent time
• Ps scanned while thinking about the event and depicted its vividness

Question 33

Gilboa at el 2004 - fMRI of remote personal memories - findings

Answer 33

• hippocampus activated for recent AND remote memories

- hippocampal activation was related to the richness of re-experiencing RATHER THAN the age of memory

Question 34

place cells

Answer 34

neurons mapping locations within an environment. each neruon represents one location

Question 35

grid cells

Answer 35

neurons in entorhinal cortex (EC) mapping multiple locations in 2-D environments

Question 36

boundary/border cells

Answer 36

neurons in EC activate when the animal is near the borders of the environment

Question 37

cognitive map theory

Answer 37

the theory that the hippocampus contains a spatial map of the environment