L4 - How the Brain Acquires New Memories

Question 1

What are the 4 common paradigms used to study memory acquisition?

Answer 1

• maze learning in rats
• eye blink response
• hand-eye coordination in monkeys
• spatial navigation in taxi drivers

Question 2

What does t-PA stand for, and what is it?

Answer 2

tissue-type plasminogen activator

It is a protein which modifies the cell after learning has taken place.

Question 3

How could we identify specific regions of the cerebellar cortex that are involved in memory formation?

Answer 3

Visualising proteins involved in memory formation could act as molecular markers of the areas of the brain involved.

Question 4

How can we study memory encoding using brain activity?

Answer 4

The Subsequent memory paradigm/Difference due to memory paradigm:

PPS are shown words whilst their EEG response to each word is recorded. They are later tested for the same, and novel items and asked whether the item is novel or seen.

EEG responses to remembered words and forgotten words were averaged, and compared, revealing the EEG activity associated with forgetting and remembering of an item.

Question 5

What does the Difference due to memory paradigm enable us to see?

Answer 5

The average EEG activity in response to remembered/forgotten words - allows an insight into memory encoding.

Question 6

What is pattern separation?

Answer 6

The laying down of distinct information by the hippocampus, to encode a specific episode.

Question 7

What is pattern completion?

Answer 7

Partial inputs/cues can later activate the full record/all other items in the memory/episode - retrieval.

Question 8

What is the binding item and context theory (Diana et al., 2007)?

Answer 8

Hippocampus binds together information from the what (ventral) and where (dorsal) pathway.

Question 9

Describe Staresina and Davachi’s (2009) test of the binding item and context theory.

Answer 9

Items were pictures of boxes with an object inside it.

During the encoding phase, items were presented either:

• combined: coloured object inside the box
• spatially dis-contiguous: the object was black and white, and the colour of the object was represented by the colour of the box.
• spatiotemporally dis-contiguous: the colour of the object was presented as the colour of the box, without an object inside. 0.5s later, the colouring of the box disappeared and the colourless object appeared inside.

During the retrieval phase, participants were tested on whether the item was new or old, what colour it was, and how confident they were in their response.

Question 10

What were the results of Staresina and Davachi’s (2009) test of the binding item and context theory?

Answer 10

Greater hippocampus activity the greater the difficulty of binding (spatiotemporally discontinguous led to the most hippocampus activity, and combined stimuli led to the least)

Question 11

What does MTL stand for?

Answer 11

Medial temporal lobe

Question 12

What does the MTL consist of?

Answer 12

Hippocampal formation, as well as the perirhinal, parahippocampal and entorhinal cortices.

Question 13

What does neuroimaging evidence conclude about the role of the MTL in encoding?

Answer 13

• The hippocampus shows subsequent memory effects, more strongly for associative encoding (object/colour binding).
• Perirhinal cortex shows subsequent memory effects for item or object information independent of contextual binding.

Question 14

What is the left PFC especially implicated in the encoding of?

Answer 14

Verbal material. Also important for visual material.

Question 15

What is the fusiform gyrus important for, in encoding?

Answer 15

Specific role is unclear, but thought to be crucial for recognition.

Question 16

What did Otten et al., (2001) test about the role of the PFC in encoding?

Answer 16

Measured brain activity in response to encoding words in a shallow (syllables) or deep (animacy; whether the word presented was an animal or not) task.

Question 17

What did Otten et al., (2001) find about the role of the PFC in encoding?

Answer 17

• Left IFG shows stronger subsequent memory effect for encoding of deep, compared to shallow, words
• suggests left IFG activity could reflect deep, semantic encoding

Question 18

What is the subsequent memory effect?

Answer 18

The ‘difference in memory’, or difference in brain activity during encoding when something is remembered vs forgotten.

Question 19

What does IFG stand for?

Answer 19

Inferior frontal gyrus.

Question 20

What did Blumenfeld and Ranganath, (2007) find in their meta-analysis of subsequent memory effects in the PFC?

Answer 20

• Positive memory effects in the ventral PFC
• Negative memory effects in the dorsal PFC

–> Therefore, activity was greater following encoding for remembered objects compared to forgotten objects in the vPFC.

But, activity was greater for forgotten objects than remembered objects in the dPFC.

Question 21

What is the parietal lobe typically associated with, in terms of its function?

Answer 21

Attention

Superior parietal lobe typically associated with goal oriented, top-down processing.

Inferior parietal lobe associated with bottom-up, stimulus driven processing.

(Corbetta & Shulman, 2002)

Question 22

Describe parietal activity in response to SME.

Answer 22

Superior parietal lobe demonstrates positive subsequent memory effects (SMEs), whereas inferior demonstrates negative SMEs.

–> when an item is remembered correctly, more activity is found in the superior lobe. When an item is forgotten, more activity is found in the inferior lobe.

Question 23

What does AtoM stand for?

Answer 23

Attention to memory

Question 24

What is the AtoM framework?

Answer 24

Top down attention is good for later memory, while bottom up attention is bad for later memory - distraction.

Question 25

Explain parietal activity in response to subsequent memory effects.

Answer 25

Activity is as follows: greater superior lobe activation for remembered items, and grater inferior lobe activation for forgotten items. Lobe functions as follows: superior - top down processing/attention inferior - bottom up processing/attention Therefore, superior lobe activity is associated with successful item recall, as top down processing leads to greater memory. Bottom up processing is stimulus driven and leads to poorer memories, hence the association of inferior lobe activity with items that were later forgotten.

Question 26

What are the 4 major regions neuroimaging demonstrates may play a role in encoding? What is the role that each plays?

Answer 26

- Hippocampus: associative processing/binding - perirhinal: item-specific (familiarity) processing - prefrontal: organisation and selection (task completion) - parietal: attention

Question 27

What does the phase of brain oscillations tell us?

Answer 27

How much in line the peaks are aligned between activity recorded from 3 different parts of the brain.

Question 28

What does the power of brain oscillations tell us?

Answer 28

Suggests there is more coherence/communication between the 3 areas that activity is recorded from.

Question 29

What is the basal state of brain oscillations?

Answer 29

It's resting state, that we expect to see when there is no input.

Question 30

Which rule relates to how brain oscillations can explain encoding and retrieval? Based on this rule, how can it explain these?

Answer 30

Hebbian learning - cells that fire together, wire together. A memory will form if a specific network of cells are active simultaneously (encoding) If one cell in the network is activated, the other cells in the network will also be activated (retrieval).

Question 31

What do time-frequency plots show?

Answer 31

Plots electrical activity recorded from a single electrode site. Exactly which frequency band that single cell is firing at.

Question 32

What did Markram et al., (1997) find about the timing of action potentials between two cells, in its effects on LTP?

Answer 32

Increase in coupling between cell A and B when the two cells were stimulated at the same time. Greater LTP as the frequency of the stimulation increases.

Question 33

What have human intracranial EEG studies shown about SMEs?

Answer 33

Higher gamma power for items that were later remembered, than items that were later forgotten. (Sederberg et al., 2008)

Question 34

How is memory measured in monkeys?

Answer 34

Longer looking times were interpreted as items that they had seen before.

Question 35

What did evidence from single neuron recordings in monkeys find (Jutras et al., 2009)?

Answer 35

Activity within the gamma frequency band accompanied remembered items, but not forgotten items. Hippocampus may use these gamma oscillatory signal as a mechanism for memory formation.

Question 36

What do human intracranial EEG studies show about synchronous activity between brain regions (Fell et al., 2001)?

Answer 36

Increased coupling (communication) between hippocampus and rhinal cortex, but only for items that were later remembered. Vice versa for items that were later forgotten. This coupling activity was found in the gamma frequency band.

Question 37

What is the relationship between the synchrony of gamma activity and communication between two regions?

Answer 37

Gamma synchronisation enhances neural communication, induces LTP - facilitates memory formation.

Question 38

What are place cells (O'Keefe, 1976)?

Answer 38

Fire only when a rat re-enters a part of its environment that was previously conditioned.

Question 39

What is local field potential?

Answer 39

Activity within the neighbouring environment of a single cell that is being recorded.

Question 40

What has been found about the activity of place cells and local field potential?

Answer 40

Only when the activity of the place cell is firing in phase with the local field potential, does the animal become aware of that particular place in the environment. - this is all theta activity Therefore, place and phase activity together code for spatial location (O'Keefe & Reece, 1993).

Question 41

What is the relationship between remembering something, and theta activity in humans?

Answer 41

Synchrony between single cells and phase activity, in the theta frequency, appeared only when subjects correctly remembered something.