Separating Storage from Retrieval Dysfunction of Temporal Memory in Parkinson’s Disease Chara 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 in 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 interval)

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?