Transcript Lecture powerpoint

Memory and
consciousness
Human verbal and visual
memory; awareness of
memory
Aim
 Learning
 unconscious
 motor
learning
 conditioning
 conscious

memory of place
 Biology of Memory
 neural
“substrate”
 Self v non self
 awareness
Types of learning
 Perceptual learning
 recognise
stimuli you have seen before
 Motor learning
 Stimulus-response learning
 classical
conditioning
 instrumental (=operant) conditioning
 Relational learning
 episodic
 spatial
First: motor learning and
the cerebellum
Motor learning
Cerebellum
Vestibuloocular reflex
 VO reflex to stabilize image on retina when
head moves
 eyeball muscles rotate eye to compensate
 no
sensory feedback
 gain has to be exactly 1
Control of VO reflex
gain = E/H = a-b
Purk cell
Inf Olive
accessory optic tract
hair cell  vestibular nucleus  optic motor neuron
VO gain need Cerebellum
prism
on
prism
off
- -x- - intact
prism left on
no cerebellum
cats rotated on platform in dark
Control of VO reflex
 without cerebellum, cannot adapt
 adaptation during aging and disease
Types of learning
 Perceptual learning
 recognise
stimuli you have seen before
 Motor learning
 Stimulus-response learning
 classical
conditioning
 instrumental (=operant) conditioning
 Relational learning
 episodic
 spatial
Next: one trial classical conditioning
Classical conditioning
 food - bell
Pavlovian fear conditioning
 CS conditional stimulus
 US
 unconditional
stimulus
 noxious stimulus – eg electric shock
 learnt fear response
 autonomic
NS; eyes dilate, blood pressure
rises, heart rate up; hormonal response
 Single trial
 last
for years
Amygdala
 initial stimulus associated with high levels of
adrenaline and corticosterone
 NMDA receptors in amygdala required for
fear learning –
role for LTP
 NMDA
antagonists /
GluR knockouts
prevent
acquisition of
learning
Consolidation
 fear conditioning, then ECS (electroconvulsive
shock)
 ECS
soon after, memory never formed
 ECS after 24hr, memory fixed
 requires protein synthesis soon after
stimulus
Generic feature of memories
ReConsolidation
 fear conditioning, then ECS
 ECS
soon after, memory never formed
 ECS after 24hr, memory fixed
 ECS after reactivating memory, memory lost
 requires NMDA receptors and protein
synthesis soon after reactivation stimulus
Long / short term memory
 STM requires protein synthesis
 amygdala
 Aplysia
 Honeybee
 Fruityfly
 hippocampus
• relational memory
 Let’s try it…
STM test
Cortex activity in learning
 word list
 difference in memory
effect
Short term memory
 different sensory
modalities are
associated with
different areas of the
cortex during STM
STM is distributed
Types of learning
 Perceptual learning
 recognise
stimuli you have seen before
 Motor learning
 Stimulus-response learning
 classical
conditioning
 instrumental (=operant) conditioning
 Relational learning
 episodic
 spatial
Now on to: Relational learning
Amnesia
 retrograde amnesia
 inability
to remember something which
happened before brain damage
 anterograde amnesia
 Korsakoff’s
syndrome – alcohol abuse
 cannot form new memories
 tell a fable when asked for recent events
(rather than say don’t remember)
HM

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
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
hippocampus removed bilaterally
remember sentences by rehearsal
learn motor skills
recall old memories
do mental arithmetic
 cannot identify by name new people
 cannot recognise surroundings
Hippocampus is
 not location of long term memory
 HM
would not know how to dress himself
 not location of short term memory
 could
not carry out a conversation
 site for consolidation of memory
HC active in learning
 areas of brain which correlate with rehearsal
- learning list of words
 PET
scan while playing word list
 test words learnt
 correlate
hippocampus
This leads to:
 declarative memories
 explicitly
available to conscious recall as
facts, events or specific stimuli (=explicit M)
 maybe verbal (as in declare)
 non-verbal – e.g. as video recall
 non-declarative memories
 not
necessarily conscious
 =implicit M
Hippocampal organisation
 RB stroke – hippocampus has high NMDA
receptors and very sensitive to ischaemia
 amnesia
 lost CA1 neurons of hippocampus
CA1
CA1
HC Place cells
 taxi drivers enlarged
CA1 region
 Rat place cells
 Induce LTP in
CA1/CA3 neurons
→ new place cells
 CA1 conditional
NMDA knockout –
longer to learn
Morris water maze
rat running in
triangular path
Summary so far
 amygdala : Pavlovian fear conditioning
 short
/ long term memory
 reconsolidation
 hippocampus crucial to memory
 cognitive
maps of the environment
 consolidation phase
 clinical
 animal
models (CA1, CA3?, LTP)
Next: where do we Find LTM ?
Lashley rat exploration
Cortex as I/O of Hc
Summary so far
 amygdala : Pavlovian fear conditioning
 short
/ long term memory
 reconsolidation
 hippocampus crucial to memory
 cognitive
maps of the environment
 consolidation phase
 STM associated with cortex
 does
not require hippocampus
Finally – memories in the future?
Prospective memory
imagining episodes in the future
Does this look familiar?
Frontal regions for “self”
 DB, amnesiac who lost experience of own
past but not non personal past
Lesion data
ventromedial frontal damage → loss
of personal future time perspective
dorsolateral frontal damage
non-frontal damage.
fMRI Data
 Big difference
between
Clinton/self
 Small
difference
between
future/past
Summary to end
 amygdala : Pavlovian fear conditioning
 short
/ long term memory
 reconsolidation
 hippocampus crucial to memory
 cognitive
maps of the environment
 consolidation phase
 STM associated with cortex
 does
not require hippocampus
 frontal region for prospective memory
Happy Christmas !!