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?