Psychobio Chapter 11: Learning, Memory, and Amnesia

information processing model

• sensory information → sensory memory → (transfer) short-term memory

  • sensory memory has an infinite amount of storage

short-term memory

• has 5-7(+-2) items

• within 18 seconds everything here can be forgotten

• moving information from STM to LTM is known as consolidation

• it’s an active process — that’s why it is also called working memory

consolidation

• tricks for memorizing things (ex: rehearsal)

long-term memory

• infinite amount of storage and sticks because of schema development

  • moving information from LTM to STM is known as reconsolidation

reconsolidation

• moving information from LTM to STM is known as _____

• each time a memory is retrieved from LTM, it is temporarily held in STM

• memory in STM is susceptible to post-traumatic amnesia until it is _____ed

• support: anisomycin, a protein synthesis inhibitor, prevents reconsolidation of conditioned fear in rats if applied directly to the amygdalae

Larry Squire’s Memory Taxonomy

• memory

  • nondeclarative (implicit) = procedural

    • nonassociative

      • skills and habits = driving a car

    • priming

      • simple classical conditioning = Pavlo’s dog/bell experiment

  • declarative (explicit) = facts you can declare/state

    • semantic memory = facts

    • episodic memory = events

nondeclarative (implicit) memory

• = procedural

2 types of nondeclarative (implicit) memory

1. nonassociative

2. priming

nonassociative learning (nondeclarative)

• skills and habits = driving a car

priming (nondeclarative)

• phenomenon whereby exposure to one stimulus influences response to subsequent stimulus, without conscious guidance or intention

• simple classical conditioning = Pavlo’s dog/bell experiment

declarative (explicit)

• = facts you can declare/state

semantic memory (declarative)

• = facts

episodic memory (declarative)

• = events

2 types of amnesia

1. retrograde

2. anterograde

retrograde amnesia

• back-acting

• unable to remember the past

anterograde amnesia

• forward-acting

• unable to form new memories

H.M. (Henry Molaison)

• epileptic who had his medial temporal lobes removed in 1953

  • 2 thumb sizes on each side of the brain

  • original surgery was to alleviate his seizures

• problem revolves around his declarative memory

• his seizures were dramatically reduced but so was his ability to form long-term memory

  • no longer able to form new memories

• mild retrograde amnesia and severe anterograde amnesia

  • can still remember some aspects of his past

amnesic effects of “bilateral medial temporal lobectomy”

• unable to form most types of new LTM

• STM is still intact

3 major scientific contributions of H.M.’s case

1. medial temporal lobes are involved in memory

2. STM and LTM are distinctly separate — H.M. is unable to move memories from STM to LTM

   • problem with memory consolidation

3. memory may exist but not be recalled as H.M. exhibits a skill he does not know he has learned (explicit/declarative VS implicit/procedural)

R.B. (unknown)

• effects of cerebral ischemia (due to heart bypass surgery) on the hippocampus and memory

  • suffered damage to just one part of hippocampus (CA1 pyramidal cell layer) and developed anterograde amnesia (minimal retrograde amnesia 2 years before his surgery)

  • case suggests that hippocampal damage alone can produce amnesia

  • H.M.’s damage and amnesia were more severe than his

N.A. (unknown)

• has been amnesic since 1960 when at age of 22 he sustained a penetrating brain injury with a miniature fencing foil

  • injury occurred in the thalamus — showing that it is involved in consolidation aka the formation of LTM

• the anterograde amnesia of verbal material and the absence of other detectable cognitive deficits

• CT scans demonstrated damage in region of left mediodorsal thalamic nuceus but no additional damage was revealed

amnesia of Korsakoff’s syndrome

• most commonly seen in severe alcoholics (or other with a thiamine deficiency)

  • characterized by amnesia, confusion, personality changes, and physical problems

  • recommended to take vitamin B1 supplements to help with the thiamine deficiency

• damage in the medial diencephalon (medial thalamus + medial hypothalamus)

• amnesia comparable to medial temporal lobe amnesia (HM) in the early stages

amnesia of Alzheimer’s Disease (AD)

• begins with slight loss of memory and progresses to dementia

• general deficits in predementia AD:

  • major anterograde and retrograde amnesia of explicit memory

  • deficit in STM

  • and some implicit memory — verbal and perceptual

• implicit sensorimotor memory is intact

types of biomarkers and tests for diagnosing dementia

• brain-imaging: CT, MRI, and PET

• cerebrospinal fluid biomarkers (CSF)

• blood tests

• genetic testing

brain-imaging: CT, MRI, and PET (biomarkers for dementia)

• beta-amyloid (plaques) and tau PET scans

• tau protein — not amyloid — may be key driver of Alzheimer’s due to the accumulation of it predicts the cognitive decline

cerebrospinal fluid biomarkers: CSF (biomarkers for dementia)

• beta-amyloid (plaques) and tau proteins (neurofibrillary tangles)

genetic testing (biomarkers for dementia)

• late-onset: APOE 4 gene in chromosome 19

• early-onset: (rare 10%)

  • amyloid precursor protein (APP) on chromosome 21 (down syndrome)

  • Presenilin 1 (PSEN1) on chromosome 14

  • Presenilin 2 (PSEN2) on chromosome 1

amnesia after concussion: evidence for consolidation

• post-traumatic amnesia: concussions may cause retrograde amnesia for period before the blow and some anterograde amnesia after

• the same is seen with comas, with the severity of the amnesia correlated with the duration of the comma

• period of antergroade amnesia suggests a temporary failure of memory consolidation (STM → LTM)

post-traumatic amnesia

• concussions may cause retrograde amnesia for period before the blow and some anterograde amnesia after

theories of hippocampal function on spatial memory

• established by Tolamn

  • observed as trials went on the rats were getting out of the maze faster

    • were able to get faster because of markers in environment to navigate — aka spatial memory gives a map in our brain to get around

  • rats are remembering parts of the maze

perirhinal cortex

• involved in storage of memory

• in the case of H.M. they took away the _____ and the hippocampus

• plays an important role in objection recognition

tests of spatial memory

• morris water maze test

  • used to asses spatial learning and memory in rodents

  • measuring their ability to navigate to a hidden platform in a pool of water

  • relying on visual cues in environment

• radial arm maze test

  • used to measure spatial learning and memory in rats

theories of hippocampal function

• cognitive map theory = hippocampus constructs and stores allocentric maps of the world

cognitive map theory

• hippocampus constructs and stores allocentric maps of the world

hippocampus and memory for spatial location

• perirhinal cortex plays an important role in objection recognition

• hippocampus plays a key role in memory for spatial location

  • hippocampextomy produces deficits on Morris maze and radial arm maze

• many hippocampal cells are

  • place cells = respondent when a subject is in a particular place and to other cues

    • John O’Keefe discovered this

      • “cognitive map is how we know where we are”

  • grid cells = found in hippocampus and entorhinal cortex

hippocampus

• plays a key role in memory for spatial location

  • hippocampextomy produces deficits on Morris maze and radial arm mase

place cells

• respondent when a subject is in particular place and to other cues

  • John O’Keefe discovered this

    • cognitive map is how we know where we are”

John O’Keefe

• discovered place cells

  • “cognitive map is how we know where we are

grid cells

• found in hippocampus and entorhinal cortex

where are memories stored?

• each memory is stored diffusely throughout the brain structures that were involved in its formation

• some structure have particular roles in storage of memories

  • hippocampus = spatial location

  • perirhinal cortex = object recognition

  • mediodorsal nucleus (thalamus) = Korsakoff’s syndrome

  • basal forebrain (nucleus basalis) = Alzheimer’s syndrome

  • prefrontal cortex = temporal order of events and working memory

  • cerebellum = sensorimotor skills (athletes knowing how to play their sport)

  • striatum (part of basal ganglia) = habit formation (routines of our behavior)

mediodorsal nucleus (thalamus)

• structure involed in the storage of memory

• korsakoff’s syndrome

basal forebrain (nucleus basalis)

• structure involved in the storage of memory

• Alzheimer’s symptoms

prefrontal crotex

• structure involved in the storage of memory

• temporal order of events and working memory

cerebellum

• structure involved in the storage of memory

• sensorimotor skills (athletes knowing how to play their sport)

striatum (part of basal ganglia)

• structure involved in the storage of memory

• habit formation (routines of our behavior)

synaptic mechanisms of learning and memory

• cellular and molecular events that appear to underlie learning and memory

  • Hebb = changes in synaptic efficient are the basis of LTM

  • long-term portentiation (LTP)

    • synpases are effectively made stronger by repeated stimulation

    • just like studying repeatedly leads to better memory

hebb

• changes in synaptic efficients are the basis of LTM

long-term potentiation (LTP)

• synapses are effectively made stronger by repated stimulation

• just like studying repeatedly leads to better memory!

• synapses composed of presynpatic and postsynaptic neuron

  • glutamate (excitatory transmitter) is released by the presynpatic neuron

    • receptors for glutamate is the NMDA and AMPA

      • NMDA opens up and Ca²⁺ enters

        • because it’s positive there will be some depolarization of the membrane

      • AMPA opens up and Na⁺ enters

  • when both of the channels open nitric oxide is released

    • which will stimulate additional production of glutamate

• as long as the neurons are stimulating each other they will remember this and keep doing it → LTP

• this is the cellular basis of memory

  • without it NO LTP will develop and NO memory will be stored

glutamate

• excitatory transmitter in LTP that is released by the presynaptic neuron

  • receptors are NMDA and AMPA

NMDA

• opens up and Ca²⁺ enters

  • because it’s positive there will be some depolarization of the membrane

AMPA

• opens up and Na⁺ enters

infantile amnesia

• not yet developed:

  • language and hippocampus

• explicit and implicit memory can be demonstrated in normal, intact subjects

  • skin conductance responses (implicit memory) elicited by pictures of preschoolers whether they were explicitly recognized or not (when tested at 9-10 yrs old)

  • modern incomplete-pictures test = previously seen pictures were recognized sooner (implicit memory) than new pictures, whether the old pictures were explicitly recognized or not

skin conductance responses (implicit memory)

• elicited by pictures of preschoolers whether they were explicitly recognized or not (when tested at 9-10 yrs old)

modern incomplete-pictures test

• previously seen pictures were recognized sooner (implicit memory) than new pictures, whether the old pictures were explicitly recognized or not

the incomplete pictures test (or Gollin figure test)

• developed by E.S. Gollin in 1960 it is a psychological test used to assess implicit and explicit memory

• subjects are shown a series of drawing in sequence from least to most clear and asked to identify the image

  • object cannot possibly be identified from first sketch and most people must see several panels before they can identify it (explicit memory)

• on retention test some time later subjects identify the image sooner than they did on the first test indicating some form of memory from the image (implicit memory)

• amnesiac subjects also show improvement on this test, even though they do not recall taking the test before (implicit memory)

who developed the incomplete picture test?

• E.S. Gollin in 1960

nootropics (smart drugs: do they work?)

• “smart drugs” or “cognitive enhancers” are substances thought to improve memory

  • limited research has shown that no purported nootropic has memory-enhancing effects in normal people

who coined the term “nootropic” in 1964

• Dr Corneliu E Giurgea

nootropic are said to work in 1 of 3 fashions

1. stimulating production of neurochemicals in the brain

2. increasing oxygen supply

3. by stimulating nerve growth factors (NGF)

propranolol

• bet-blockers (memory blockers)

  • when in fight or flight we release norepinephrine and epinephrine (adrenaline) — that’s why heart rate increase

• helps slow down heart rate but there is the adrenaline receptors in the brain

  • It helps to enahce memory

• research being done to see if it can help combat PTSD

  • seeing if they can give it to soldiers before they go to war to help with PTSD