Topic 10 - Memory

Blue Whale Study

probably have a good long-term memory to remember migration routes for reproduction or tracking resources for foraging - must attend to more than just proximate cues

study looked at whether they track phytoplankton blooms, which fluctuate as a function of temperature by studying migration patterns vs. randomly simulated paths to changes in surface temperature and green-up → whales track green-up 

Proximate Cues

an immediate, observable environmental or social trigger that influences its behavior or physiology

Ebbinghaus

first to look at memory, but did it on himself with nonsense syllables above the capacity of our memory using a metronome for pacing

image shows forgetting cureb

William James

came up with 2 memory systems: primary and secondary

primary memory is information in current conscious awareness, the current sensory experience that is initially vivid then fades quickly unless captured by attention

secondary memory: former state of mind that has dropped out of consciousness (bringing a copy of the original event to mind)

Broadbent

important guy for attention, said that information flows through sensory channels where it can be filtered out and lost or selected for further processing

also has primary and secondary memory systems:

• primary has S-system for pre-attentive memory store (sensory buffer) and P-system, a limited capacity memory store constituting conscious awareness

• secondary memory is permanent storage

What do we take from historical ideas?

• memory is not monolithic in a mechanistic or anatomical sense (there are different forms)

• short-term (primary) stores are capacity limited

• going from short to long-term memory takes more processes to consolidate the memory (aka rehearsal according to Broadbent)

Short-term Memory

aka working memory

refers to limited capacity to hold information in mind for short periods of time, from seconds to minutes

Long-term Memory

storage of information that can be retrieved over longer periods of times (minutes to years) - is actually a collection of stores

• episodic: you were the actor

• semantic: knowledge of things about the world

• procedural: abilities like riding a bike

Learning

a form of memory referring to changes in behaviours in the nervous that are brought about through experience - basically memory as a function of experience

How long does echoic memory last?

3-4 seconds

this is a large capacity store that decays rapidly that allow us to access only very recent sensory information

Which lasts longer - echoic or iconic memory?

echoic memory since it lasts 3-4 seconds, iconic (visual information short-term memory store) lasts about 500ms

Partial Report Task

an array of stimuli are shown that are more than what short-term memory capacity can handle (7 ± 2)

participants are asked to report on one row of that array but they are not told which row beforehand → people are able to accurately recall cued information even when they don’t know which row it’ll be

Imagery and Perception Task (Ganis)

• control condition - in the dark with eyes closed, people heard the word “tree” and asked to make a mental image of the item 

• experimental condition - presented with a low contrast lime image of similar items

brain activation was compared between the perception and imagery (control) conditions → subtracting the two showed basically no difference in activation

this means you recreate the thing you’re trying to remember in the mind, therefore activating the same brain areas you used when you first made the memory

Successful retrieval of words that were paired with ____ was associated with ____ ____ activation, while words paired with ____ were associated with ____ ____ activation.

images; visual cortex; sound; auditory cortex

this suggests that memory needs some activation of perceptual areas → evidence that memory is a recreation process that uses the same neural networks that were engaged when we first encountered that thing

Tom James Perceptual Learning Study

similar to priming study, people were shown things that were hard to see because of noise or it is gradually revealed

when you show the sequences multiple times, fusiform gyrus shows peak of activity diminishing overtime (less brain activity is evidence of learning and better efficiency at recognizing the object → priming)

• key was that the gradually revealed objects were shown many times to compare first vs. fourth viewing

Classical Conditioning

• unconditional response (UR): response/reflex with no association to secondary stimulus e.g. blinking to a puff of air

• unconditioned stimulus (US): stimulus that produces unconditioned response e.g. blinking puff of air to eyelid

• conditional stimulus (CS): stimulus closely in time with US e.g. tone paired with air puff

• conditioned response (CR): response to the CS, without the US e.g. blinking at the tone with no air puff

Operant Conditioning - Skinner

more direct stimulus response mapping - pairs specific behaviours with specific outcomes

used pigeons with specially designed boxes, you can show that the bird will learn to peck a lever to get food reward

• rewarding stimulus reinforces a behaviour since it leads to something the organism wants

• behaviour can be reinforced if it is paired with unpleasant outcome

• negative reinforcement: positive outcome is removed to extinguish a behaviour

Operant Conditioning Overview

stimulus-response conditioning using:

• reinforcing stimuli (perceived as positive)

• punishing stimuli (perceived as negative)

reinforcement/punishment occurs after the response

Variable Reward Schedule

one method that Skinner used since he found to be stronger than giving consistent rewards associated with behaviours

Transference

Little Albert tested by James Watson (behaviourist)

Albert was classically conditioned to fear rats when paired with a loud noise, then just seeing the rat was enough for a fear response, then similar stimuli (anything white and furry) would make the response

extinguishing: conditioned response for him was showing him enough rats without the loud sound attached

Elisabeth Phelps Extinguishing Conditioned Response

done by pairing conditioned stimulus without associated negative outcome in early parts of extinction protocol

• red square shown with electric shock

• eventually, you exhibit fear (measured by galvanic skin response) by just seeing the red square

• extinguish fear response with either a reminder that red square no longer comes with a shock or given no reminder

  • reminder group did not show any return of fear response

To have something in short term memory that you can use, you have to be able to ______.

pay attention to it

Working Memory

aka short-term memory

delayed match-to-sample task with monkeys:

• monkey learns the rules where food reward is under the card with a cross on it

delayed non-match-to-sample:

• switch the rule to make sure the monkey isn’t just responding to what he saw last - monkey learns the food is at the location that ISN’T cued

• delay period had nothing on the screen

results showed regions of prefrontal cortex had neurons that the monkey needed to remember were still firing in the delay

Miller

7 ± 2 persecuting integer is for verbal memory

• visual memory span is likely around 4 items but that could be because humans are language-bound since we talk a lot

• we can push past this number with various techniques such as chunking

Method of Loci

used to break through the 7 ± 2 number by creating a memory palace for a familiar route

for example, put grocery list items in certain locations as you walk to the store and you can recall walking that way and which item was where → helps because you don’t need to remember the path itself since you’re already familiar with it

What happens to information that is forgotten?

2 possibilities:

1. decay - without rehearsal, memory diminishes and remembering it gets worse

2. interference - new things get in the way of the old

Primacy

relies on the ability to rehearse things over and over

• rehearsal transfers info from short to long term memory (consolidation)

• memory system has the resources to put items from the beginning of a list to long term memory

• presenting items interferes with primacy

Recency

depends on short term/ working memory

• don’t need rehearsal since items at the end of a list are still in short term memory

• adding a distractor task at the end would interfere with remembering the later things but not the earlier

Baddeley’s Working Memory Model

mentions visuospatial sketch path and phonological loop which are domain-specific stores

• visuospatial sketch pad is for visual information, things you can manipulate and work with in relation to space

• phonological loop is more for word information - maintained and manipulated auditory information

  • even when presented with the visual letters P and T vs O and Q, we are worse at disambiguating P and T since they sound the same even if they look different

• central executive - not specific to modality, important for interrupting routine behaviours to direct resources to new circumstances

dorsolateralprefrontal cortex is important for working memory, left STG for verbal and right for visual information

If asked to do a visual task and an auditory task, your ____ memory is not affected by the ____ task, and vice versa.

visual; auditory

evidence for these being separate is from studies with interference, where it is only observed when two tasks are in the same domain

Declarative Memory

knowledge that you’re conscious of:

• episodic/autobiographical - things about yourself in episodes for example a day at a time; you are the actor

• semantic - conceptual knowledge, understanding facts about the world

Forms of Long-term Memory

• declarative memory

  • episodic/autobiographical

  • semantic

• non-declarative

  • procedural learning

  • conditioning

Non-declarative Memory

experience dependent changes in the brain and behaviour (learning) that we do not have conscious access to 

• procedural memory like learning to ride a bike involves conscious processes early on but done without conscious guidance once mastered

• classical conditioning

• priming: alteration of responding based on prior exposure

• non-associative learning - systemic desensitization for phobias (teaching relaxation to cure phobia)

Retrograde Amnesia

loss of memories prior to brain injury, about 6 months of effects

Anterograde Amnesia

inability to make new memories after the brain injury, about 2 months of effects

Post-traumatic Amnesia

period of time after a traumatic injury for example concussion or acceleration-deceleration injuries after car crashes

this patient is usually disoriented in time and place, tested by asking standard questions like what year is it, where are you, etc

HM

had severe intractable epilepsy that did not respond to medication so had surgery to remove his bilateral medial temporal lobes (where they thought the seizures came from)

• structures removed include hippocampus, entorhinal cortex, amygdala - these regions give context to the memories we want to create

he now had anterograde amnesia and couldn’t form new memories but personality didn’t change and ability to learn new information of certain kinds stayed, just not autobiographical

also had some retrograde amnesia

What remained for HM?

patient with medication-resistent seizures who had hippocampus taken out, among other structures

• semantic memory stayed

• procedural memory

• remote memories from childhood - the older the memory, the more robust to brain injury it is since it’s been consolidated and re-remembered

• language/social skills 

Mirror Drawing Task

done on HM to see if he could make new procedural memories

he has to trace the image of a star by looking at his hand in a mirror, not at it directly (essentially a visuomotor transformation)

he did pretty poorly on day 1 but got better and maintained this improved performance across a number of days → couldn’t even remember doing the test but was performing it well

could also show implicit learning like with a stem word completion but not with free recall

Which brain regions are important for memory?

• hippocampus - builds a map of the distributed brain regions that are engaged when first encoding a new memory

• parahippocampal cortex - contextual and spatial information

• perihrinial and entorhinal cortices give context to the new memories we want to create

• amygdala - giving emotional colour

Dissociative Fugue

rare; complete loss of memory for personal identity (don’t remember who you are)

could be psychogenic in nature

Korsakoff’s Syndrome

for chronic alcoholics

1. severe anterograde amnesia

2. temporally graded retrograde amnesia - recent memory is very bad but older memories are easier to remember

3. confabulation: filling in the gaps of memory by making a story rather than acknowledging the loss of memory (not delusions) - this sets amnesics apart from Korsakoff’s

alcoholism combined with vitamin B deficiency leads to degradation of the mammilothalamic tract is thought to be responsible for the memory deficits

Alcoholic Brains

big spaces and loss of tissue - sulcal widening (spaces between gyri), enlarged ventricles

Hemispheric Encoding-Retrieval Asymmetry (HERA)

this model says retrieval of episodic memories is a mostly in the right hemisphere whereas the left was involved in encoding episodes and retrieving semantic information

There is ____ activity in the prefrontal and medial temporal cortices for successfully recalled items.

higher; there is still some activity in the same regions when we recall them unsuccessfully, just less of it

prefrontal activations tend to be material specific with verbal information activating the left and visual information the right

• hippocampus doesn’t differentiate between what you think you saw and what you actually saw, but shows a difference in activation for new items

• parahippocampal gyrus surrounds the hippocampus and it accurately distinguish between old and new items

London Cabbies

a morphometry study about shape and size of brain regions on London cab drivers showed they had larger posterior hippocampi in the right hemisphere vs. non-cab drivers

they need to pass a really hard test and not use a map

follow-up study showed more experienced cab drivers had larger hippocampi than those are new

greater density of synapses (synaptogenesis) comes from experience

Working memory dysfunction in delusional disorders: an fMRI investigation

we think we see everything we open our eyes, but we don’t really have a full and complete representation

setup: working memory is a foundational skill and people with delusional disorder have non-bizarre delusions and may have executive function deficits

WM represents core function that executive functions are built on

• method had 2 groups: deluded and control with a block design of a 2-back task in fMRI

• delusional guys were worse behaviourally, even at the 0-back task

• activations that are higher in delusions than in controls: superior temporal gyrus, PCC, left MTG, right amygdala

results left us with more questions since hyperactivity in posterior areas or hypoactivity in the frontal part could prevent you from putting things in order