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Separating Storage from Retrieval Dysfunction of Temporal Memory in Parkinson’
s DiseaseChara Malapani, Bernard Deweer, John Gibbon
Presented by:
Vincent Fang
Background Info:
Parkinson’s Disease (PD):- dysfunction of BG + brain nuclei leading to disturbances of movement and cognition- disordered timing of movements- impaired time estimation (*), encoding vs. decoding.
Dysfunctions can be treated with dopaminergic agents, but different results
Background Info Cont’d:
Dopaminergic neurons originating in SN + striatum represents pacemaker interval timing (clock).
Increase Dopamine = faster clock time (rats) Dopamine lesion to striatum eliminate timing i
n rodents, if treated with L-dopa after, timing doesn’t return. (but L-dopa works on SNc).
Introduction:
Idea: examining PD patients’ drug state to determine whether dopamine deficiency selectively affects memory storage, retrieval, or both.
Storage or Retrieval? Either ON or OFF drug.
Introduction Cont’d:
Migration Effect: Overestimate the short interval & underestimate the longer interval.
Experimental Design:
Encode-Decode Experiment:
- ON group – given DA antagonists
- OFF group – no drugs given (18hrs)
- at maximal parkinsonian disability
Subjects:
36 patients: idiopathic PD (mini-mental state & Montgomery and Asberg Depression Rating) X2, no anticholinergic drugs
4 groups: (assessed 90min after)– ON-ON– OFF-ON– ON-OFF– OFF-OFF
Subjects Cont’d:
Methods:
Used Peak Interval (PI) timing procedure:
- compare elapsing interval to a remembered interval.
80 Trials: 10 trials X2 & 60 trials. 2 days
- encode vs. decode
Methods Cont’d:
Computer:
- 2.1X2.1 in. blue square magenta square Remember the time interval
- refrain from counting or tapping
- avoid extraneous timekeeping
*random digits superimposed over square (then read aloud)
Method Cont’d:
Actual Experimental Trial:
- “bracket” termination of target interval
use space bar (1st press & release)
- ended when: 3X target interval had elapsed
Results:
Migration observed when comparing:
- ON vs. OFF PD Patients (decoding) Restoring DA during decoding improves retrieval deficit
**migration in PD patients DA-dependent dysfunction of retrieving temporal memory
Results Cont’d:
OFF-ON group:
- (OFF) when encoding incorrect storage incorrect retrieval (ON)
Discussion:
Results are similar to their previous experimental data– Mutual attraction between temporal estimate of 2
intervals: underestimation of long interval, overestimation of short interval
Discussion Cont’d:
Normal reproduction of time in ON Migration (overest. Short / underest. Long) in
OFF OFF-ON (during ON, overest. of both interva
l)
Discussion Cont’d:
Discussion Cont’d:
Future Research:
Whether the dysfunction caused by either storage or retrieval have distinctive neural pathways.
-then there will be brain images
Limitations:
Hard to follow PD patients have muscle jerks, might not be
precise Confusing data explanations
Strengths:
Graphs were easy to read Based on his own previous research
– Eliminated many possible confounds
Questions?