DORSAL STRIATUM

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DORSAL STRIATUM

• ANATOMY.
• ELECTROPHYSIOLOGY.
• BEHAVIOR.

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ANATOMY

• RECEIVES EXTENSIVE POLYMODAL SENSORY INFORMATION
  REPRESENTING EXTERNAL WORLD.
• TOPOGRAPHICAL ORGANIZATION.

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DORSAL STRIATUM

• LASHLEY (1950)
• The evidence seems conclusive that in mammals
  the basal ganglia are not an essential link in
  the patterning of learned activities.

• WEBSTER (1961)
• The discovery of the corticostriate projections
  from sensory areas was important in implicating
  the dorsal striatum in higher-order behavioral
  functions.

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ANATOMY

• RECEIVES INFORMATION ABOUT LIMB AND WHOLE BODY
  MOVEMENTS.

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ANATOMY
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ELECTROPHYSIOLOGY

• VISUAL DISCRIMINATIONS.
• ACTIVE AVOIDANCE.
• STIMULUS-GUIDED HEAD TURNING.

• SENSORY RESPONSES.
• MOTOR RESPONSES.
• SENSORY-TRIGGERED MOVEMENTS.

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ELECTROPHYSIOLOGY
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BEHAVIOR

• ACTIVE AVOIDANCE.
• EGO-CENTRIC MAZE LEARNING.
• VISUALLY-GUIDED MAZE LEARNING.
• REACHING, GROOMING, WATER MAZE.

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TRIPLE DISSOCIATION

• SPATIAL.
• STIMULUS-RESPONSE.
• CLASSICAL CONDITIONING.

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Spatial Task
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S-R Habit Task

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Conditioned Cue Preference Task


Food
Paired
Unpaired
No Food
Training
Testing
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INTERACTIONS BETWEEN LEARNING AND MEMORY SYSTEMS

• Between system competitions
• Hippocampus and dorsal striatum

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Method

• 3 groups of subjects prepared
• Group1 neurotoxic lesions of the dorso-lateral
  striatum.
• Group 2 radio-frequency lesions of the fornix.
• Group 3 sham lesions

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CUE/PLACE TASK

• A modified version of the standard spatial
  version of the water task

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Cue-Place Acquisition
31 cue-place series repeated 3 times (12 days)
Competition Test
Visible platform moved to opposite quadrant
adapted from McDonald, R.J., White, N.M.
(1994). Parallel information processing in the
water maze Evidence for independent
memory systems involving dorsal striatum and
hippocampus. Behavioral and Neural
Biology, 61, 260-270.
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Water maze Competition Test
Cue Response
Place Response
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Control

Control
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TRAIT DIFFERENCES
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Dorso-Lateral Striatum
Hippocampus
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SUMMARY

• There is a balance between learning and memory
  systems in normal subjects.
• Damage to one system enhances control by intact
  systems.
• Abnormal behavior is caused by a shift in the
  balance between these systems.

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Summary of Radial Arm Maze Results
McDonald White (1993). A triple dissociation of
memory systems Hippocampus amygdala, and
dorsal striatum. Behavioral Neuroscience, 107,
3-22.
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STIMULUS-RESPONSE TASK (HABIT)

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L
D-
response
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Challenge 1

• Design a set of procedures to more rigorously
  assess the extent of associative structures
  linked to the visual discrimination training
  experience.
• institute reversal learning procedures
• manipulate context
• develop novel transfer tests

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Question

• Does the amygdala acquire information during
  acquisition of the visual discrimination task?

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Method

• train subjects to asymptotic performance on the
  visual discrimination task.
• Reversal learning in a context different from
  original training.

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REVERSAL LEARNING (L-, D) DIFFERENT CONTEXT
TRIAL BLOCK
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Interim conclusion

• The amygdala appears to acquire an association to
  the reinforced light cue during original
  training, an association that enhances reversal
  learning.

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Question

• What is the nature of the representation acquired
  by the amygdala?

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Method

• 3 groups of subjects prepared
• Group1 lesions of the dorso-lateral striatum.
• Group 2 lesions of amygdala.
• Group 3 sham lesions

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Method

• Train subjects on the visual discrimination task.
• after training execute a transfer test.
• Conditioned cue preference task.

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STIMULUS-REWARD


Food
Paired
Unpaired
No Food
Training
Testing
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S-R ACQUISITION (L,D-)
100
90
80
70
60
MEAN CORRECT
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SHAM
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AMYGDALA
30
20
1
2
3
4
5
6
7
8
9
10
11
12
13
14
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TRIAL BLOCK
S-R ACQUISITION (L, D-)
100
90
80
70
MEAN CORRECT
60
50
SHAM
40
DLS
30
20
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
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TRIAL BLOCK
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Conclusions

• The amygdala incidentally acquires an association
  between the light cue and the reinforcer during
  visual discrimination training.
• The dorso-lateral striatum simultaneously
  acquires a necessary association between the
  light cue and a turning response.

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reward
L
D-
response
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Question

• Does the hippocampus acquire information during
  acquisition of the visual discrimination task?

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Control experiments

• Context-specificity.
• Reversal learning in the same or different
  context from original learning.
• Competition test.

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CONTEXT DETECTION (L, D-)
100
100
same
same
diff
diff
90
95
80
90
MEAN CORRECT
LATENCY (sec)
70
85
60
80
50
40
75
PRE-SHIFT
SHIFT
POST-SHIFT
PRE-SHIFT
SHIFT
POST-SHIFT
DAY
DAY
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Conclusion

• expression of the stimulus-response (habit) is
  not context specific.

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Design
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Reversal learning
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Conclusion

• The rate of reversal learning is enhanced when it
  occurs away from the original training context.
• We have hypothesized that a CS-no event
  association accrued to the non-reinforced dark
  arm during original training that hinders
  reversal learning in that context.

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Competition

• Return the group of subjects reversed in the
  different context to the original.

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Conclusions

• A competition between memory systems occurs when
  subjects are brought back into the original
  training context after reversal learning.

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Hippocampus

• One mnemonic function linked to the hippocampus
  is context conditioning.
• Assess the effects of hippocampal lesions on the
  context-specific inhibition effect.

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REVERSAL LEARNING (L-, D) SAME CONTEXT
HPC
SHAM
100
90
80
70
60
50
40
11
13
15
17
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21
23
25
27
29
31
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TRIAL BLOCK
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COMPETITION (L. D-)
100
90
80
70
60
MEAN CORRECT
50
40
30
HPC
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SHAM
10
0
1
2
3
4
5
TRIAL BLOCK
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Conclusions

• The hippocampus acquires a context-specific
  inhibitory association during original training
  of the visual discrimination task.

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context
reward
L
D-
response
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Implications

• Raises questions about attempts to link
  plasticity processes in specific brain areas to a
  type of learning.
• Neurogenesis.
• Plasticity cascades.
• Non-invasive imaging.