Transcript Amnesia and Hippocampal area

Learning
References:
1. Packard M, Knowlton B, Learning and memory functions of the basal ganglia,
Annual Reviews neuroscience, Vol 25, 563-593, 2002
2. Clark, RE, Squire, LR, Classical Conditioning and Brain Systems: The role of
awareness, Science, Vol 280, pp. 77-81, 1998
3. Knowlton B, Mangels JA, Squire LR, A Neostriatal habit learning system in
humans, Science, Vol 273, 1399-1402, 1996
4. Willingham DB, Salidis J, Gabrieli J, Direct comparison of neural systems
mediating conscious and unconscious skill learning, Journal of Physiology, pp
1452-1460, 2001
intact in amnesia
ex: motor/habitual skills
ex: word priming studies
ex: simple CS
Working
Memory
DLPFC
Parietal
(striatum=caudate+putamen
diencephalon=thalamus and vicinity)
Squire, 2004
Explicit Memory
– memory of facts and experiences that one can
consciously know and declare
– hippocampus- neural center in limbic system
that helps process explicit memories for
storage
Implicit Memory
– retention without conscious recollection
– motor and cognitive skills
– dispositions- conditioning
Non-declarative memory:
Occurs through modifications within specialized
performance systems.
May be revealed through deactivation of systems
through which learning originally occurred.
It is dispositional, being expressed through performance
rather than recollection. So it can not be true or false.
Priming
Repetition priming (Gabrieli, 1998)
Defn: A change in the processing of stimulus due to prior exposure to
related stimulus.
Types:
Perceptual priming:
Study versus test phases use stimuli from same or different modalities.
(visual, auditory, words). Example tasks: word-fragment completion,
picture naming. Effect is more observed when both stimuli are from the same
modality
Conceptual priming:
Study versus test phases use associative pairs. Example tasks: word-association
generation, category-examplar generation. Effect is more observed when study
phase enhances stimulus meaning.
Lesions:
Amnesic patients exhibit normal performance in all these example priming tasks.
as long as the task requires implicit recall. When the task requires explicit recall
(for ex: cued recall) amnesic patients failed
Basal ganglia damage patients also show intact priming
Systems:
Looks like separate areas in neocortex mediate perceptual and conceptual
priming. For perceptual priming, modality specific areas, for conceptual
priming, amodal association cortices are in action.
For example, in visual word-stem completion,, bilateral occipital cortex
activation occurs. In abstract/concrete decisions about words, L frontal
cortex activity is reported.
For example in AD (Alzheimer's), association cortices are affected, resulting
with intact perceptual but impaired conceptual priming. Also patients with
right occipital lesions show intact conceptual priming but impaired visual
word-identification.
Repetition priming in a given domain reflects experience-induced changes
in the same neural networks that subserved initial processing in that domain
For ex: in fMRI, activity decreases when priming occurs
Skill Learning
and basal ganglia
Procedural/Skill memory (Gabrieli, 1998)
Defn: acquisition, retention, retrieval of knowledge expressed through
experience induced changes in performance
Tests: implicit tests where no direct reference is made to the experience
(ex: skill learning, repetition priming, conditioning)
Sensorimotor skills: rotary pursuit, mirror tracing...
Lesions:
Sensorimotor and perceptual skills such as reading are intact in amnesic
patients who have poor declarative memory
Basal ganglia damage impairs:
sensorymotor skill learning (ex: Parkinson's)
cognitive skills such as probabilistic classification
Cerebellar damage impairs mirror tracing
One hypothesis indicates basal-ganglia is effective in open-loop skill learning
(skills related to planning of movements) cerebellum is effective in closed-loop
skill learning (continuous external feedback about errors in movement)
* While a skill is being learned, the area of brain responsible for skill-related
function is predominantly active. Once the skill is learned, separate areas
of brain are engaged, but the activity in the early skill-learning areas diminish.
Ex: in piano players, contra-lateral motor area activates while complex finger
movements are practiced. In non-musicians, premotor (BA 6) activate while
movements are practiced, but when movements are learned the activity in
BA6 diminishes .
Ex: Similarly, in finger tapping experiments, a decrease occurs in cerebellar
activation with the learning of finger-tap sequences
Probabilistic Learning
Probabilistic Learning
Knowlton, 1996
Probabilistic Learning
Survey questions
about experiment
Weather prediction
Knowlton, 1996
Probabilistic Learning
Erdeniz, 2007
Parkinson Patients vs Controls Non-Monetary Feedback
Irrelevant Information Task
Frequency of Blue Choice
Frequency of Blue Choice
100
90
80
70
60
50
Parkinson Patients
Controls
40
1
2
3
Blocks
4
5
Erdeniz, 2007
Parkinson Patients vs Controls Non-Monetary Feedback
Irrelevant Information Task PD Reaction Time Graph
1600
Reaction Time (msec)
1400
1200
1000
800
Parkinson Patients
600
Normal Controls
400
1
2
3
Blocks
4
5
Erdeniz, 2007
Parkinson Patients vs Controls Non-Monetary Feedback
WM and Basal Ganglia are at competition
Erdeniz, 2007
Stimulus-Response Learning
Willingham, 2002
Stimulus-Response Learning
Willingham, 2002
Stimulus-Response Learning
Willingham, 2002
Stimulus-Response Learning
Willingham, 2002
Classical Conditioning
• Involves making connections between two forms of
stimuli:
– Unconditional (US): reliably provokes a response
• Response is termed unconditional (UCR)
– Conditional (CS): neutral: does not provoke the
response
– Pair the CS and UCS over many trials
– Does the CS alone produce a response?
Reflex (delay) conditioning: (Gabrieli, 1998)
Experiment: CS 250-500 ms tone, US airpuff, both terminate together.
US initiates eyeblink. After CS is learned, eyeblink occurs without airpuff.
Electrophysiology: Hippocampus and cerebellum activity correlates
with this behavior
Lesion:
Hippocampal lesions do not impair delay conditioning but cerebellar
lesions abolish this response (humans and rabbits)
Delay eyeblink conditioning is impact in amnesic patients with bilateral
medio-temporal (MTL) or bilateral thalamic lesions or in patients with
basal-ganglia damage
Trace conditioning (complex):
Experiment: CS 250-500 ms tone, US airpuff, delay between the end of
CS and onset of US. Delay is 500-1000 msec
System: Same system active in declarative memory: MTL
Lesion:
Delay eyeblink conditioning is impaired in amnesic patients with
medio-temporal (MTL) damage (also in animals)
Cerebellum is good enough for delay conditioning
Classical Conditioning
Clark, 1998
Classical Conditioning
Clark, 1998
Worthy of note
Piano training changes the depth of your central sulcus
ILPG measure
n= 30 control, 21 pianists
MRI:T1 1.17 mm
Katrin Amunts