Separating Storage from Retrieval Dysfunction of Temporal

Memory in Parkinson’s DiseaseMalapani, Deweer & Gibbon (2002)

Tiffany Wang

Symptoms:o Bradykinesia - slowing in motoro Bradyphrenia - slowing in cognitiono Poor time estimation

Associated brain areas:o Dysfunction of basal ganglia & brain nuclei

Dopamine deficiency in substantia nigra projecting to striatum

Parkinson’s Disease

Temporal memory – the ability to compensate for the passage of time during locomotory behaviour

“Migration effect”o Dependent on two learned time intervalso Overestimate the shorter of two intervals, and

underestimate the longer of the two

Definitions

Test whether it is storing or retrieval dysfunction responsible for the distortion of time interval with dopamine deficiency.

Research Question

Using encode-decode experimentoON or OFF medication (L-dopa) during

2 experimental days

ControlsON-ON: no distortion in timingOFF-OFF: migration in both sessions

Predictions

Predictions

Participants 36 Parkinson’s Disease diagnosed patients

Encode-decode experiment Short time interval (6sec) Long time interval(17sec)

Method

Day 1 storage session 20 fixed-time trials 30 peak trials with feedback 10 peak trials without feedback

Day 2 Retrieval session 60 peak trials without feedback

Method

Results

- Migration in all OFF state

- Overestimation for both target intervals in the OFF – ON state

Dissociation between deficits in storage and retrieval temporal memory processes

Dopamine deficiency leads to:o Process of time interval storing in memory slowedo Interference/coupling occurs during retrieval

Suggests neuroanatomy of these functions separateo Storage: rely on simple, excitatory corticostriatal

neuro patho Retrieval: involvement of inhibitory striato-pallidal

circuit

Discussion

Strengthso Effectively tested for storage separate from

retrieval processes

Limitationso All participants diagnosed with PDo No specification of gender/ageo Lack of brain imaging

Strengths & Limitations

Test whether dysfunction in storing and retrieving temporal memories rely on distinct neural networkso Using brain imagingo Compare PD subjects with normal subjects

Future Directions

Malapani, C., Deweer, B., & Gibbon, J. (2002). Separating Storage from Retrieval Dysfunction of Temporal Memory in Parkinson's Disease. Journal of Cognitive Neuroscience, 14(2), 311 - 322.

Questions?