PSYCH 377 - Memory + Amnesia

Short term memory

Sensory, motor, cognitive

< 15 seconds

• working memory

• Ability to hold a limited amount of information in mind for a short period of time, usually a few seconds or minutes

• Temporary storage space for information that you’re actively using or thinking about

• Limited capacity

• Finite duration

• Active maintenance

Long Term Memory

Vast, mostly permanent store of information and experiences

• Virtually unlimited capacity and duration

• Incoming information is encoded and stored in the brain

• Some memories are easily recalled, while others require prompts

Explicit Long Term Memory

Involves the conscious and intentional recall of facts and events

Declarative memory

Episodic:

• Personal

• Autobiographical

Semantic:

• Facts

• Knowledge

Implicit Long Term Memory

Operates unconsciously and influences behaviour without explicit recall

Procedural memory + behavioural response

Acquired through experience

Stable + persistent

• skills

• Habits

• Priming

• Conditioning

Emotional Long Term Memory

Conscious + unconscious

More likely to be retained in long term memory compared to neutral memories

• Attraction

• Avoidance

• Fear

Working memory

Special case of STM requiring active manipulation of STM contents

• a cognitive system that temporarily stores and manipulates information needed for complex tasks like reasoning, comprehension, and learning

• holding information while working with it

• temporary storage

• active processing

• essential for complex tasks

Encoding

Process of memory storage

Study processes

Memory Function Relies on 3 Stages

1. Encoding Learning

2. “Storage” Consolidation: rehearsal + re coding

3. Retrieval Memory

Retrieval

Process of remembering

Free recall

Retrieval without the aid of cues

Cued recall

Retrieval with the aid of cues

Recognition

Stimulus triggers remembering

Different Brain regions involved in memory

Left parietal cortex

Prefrontal regions

Hippocampus

Amygdala

Striatum (Putamen and globes pallidus + caudate nucleus)

H.M

• bilateral transaction of temporal lobes

• After surgery, left with anterograde amnesia + some retrograde amnesia

• Above average IQ

• Good memory for events before surgery, but unable to describe job he was worked for 6 months

• Good spatial memory for his immediate surroundings

Amnesia

Partial or total loss of memory

• resulting from localized brain lesions

Anterograde Amnesia

Inability to acquire new memories

Global Anterograde Amnesia

HM

Impairment in ability to form new memories across a variety of areas

• e.g: spatial, semantic

Retrograde Amnesia

Inability to remember old memories

• may be incomplete, with older memories being accessible, whereas more recent memories are not

Infantile Amnesia

Loss of memory for the early years of life

• structures of rain weren’t developed enough yet

Transient Global Amnesia

• Sudden onset, acute, and short course

• Loss of old memories and inability to form new memories

• Concussion, epilepsy, migraine, hypoglycemia

ECT (Electroconvulsive Shock Therapy)

Involves inducing a controlled seizure in a patient under general anesthesia by passing a small electric current through the brain

Treatment for depression

Can produce a transient amnesia: temporary, sudden loss of memory for recent events and the inability to form new memories, lasting for a few hours

Ribot’s Law

Proposes that in retrograde amnesia, more recent memories are more vulnerable to impairment than older memories

Time gradient:

• memories formed closest to the time of the brain injury are mor susceptible to damage compared to older, established memories

Characterization of Korsakoff’s Syndrome

• anterograde amnesia

• Retrograde amnesia

• Confabulation

• Merger content in conversion

• Lack of insight

• Apathy

Korsakoff’s Syndrome

Chronic memory disorder

Caused by thiamine (vitamins B1) deficiency, often caused by prolonged alcohol abuse

Damage may be in medial thalamus, mammill bodies of hypothalamus, and general atrophy

Cannot be cured, but can slow progression by stopping alcohol intake

Auditory-verbal working memory

cognitive system that allows you to temporarily store and manipulate verbal information you hear

• phonological store: involves both passive storage and active rehearsal of auditory information

• input + output buffer

Visual-nonverbal working memory

cognitive function that allows individuals to hold and manipulate visual information in their minds without relying on verbal or auditory representations

• visuospatial scratchpad

• dorsolateral prefrontal cortex: involved in controlling attention and suppressing distracting information to facilitate the retention of relevant visual details

• mental rotation

• navigation

• spatial reasoning

• remembering visual details

• reading comprehension

Delayed Response Paradigm

Monkeys with DLPFC bilateral lesion

Food - screen + delay of 1-10s: found the food 50/50, don’t go directly to it, there will be no memory of where the food is

Connection of visual memory and location info: lost ability to hold visual info in storage at all

Single Cell DLPFC

Represents how DLPFC plays a role in motor planning, particularly in relation to visual info

• monkey fixes its gaze on an “X”

• After stimulus disappears the money must maintain fixation for a few seconds; highest level of activation during delay stage

Spared Working Memory in Amnesia

H.M: spared ability to hold small amounts of information over brief periods of time

Digit span task: 7 digits - can be done by those with anterograde amnesia

Delayed non-match-to-sample (eye movements)

• monkeys with lesion end hippocampus: can do the task if delay is less than 10-15 secs

Goblin Incomplete Pictures Task

When shown the figures again after a delay, intact people recognize the objects at a less complete stage than initially, indicating that prior exposure influences performance; amnesia patents show the same effect

• repetition priming in amnesia

• Benefits from previous exposure

• Something sorted implicitly

Stem Completion

Delay well beyond ST memory

• those with anterograde amnesia more likely to complete these words with the word that were in the word list; show a relatively preserved ability to perform this tasks

• Suggests that implicit memory systems, are still functional

H.M - Deficits in learning new words

Hippocampus damage + semantic memory

• hippocampus is crucial for forming new memories; converts STM into LTm by organizing, storing and retrieving memories within the brain

• Struggled to learn the meaning of new words and facts, could recall familiar vocabulary learned before the surgery, but had difficulty acquiring new semantic info