Abstract
The role of dopamine in visual working memory (WM) functions is not fully understood. We investigated the effects of dopaminergic drugs on precision of WM recall in Parkinson’s disease (PD) and healthy people. In PD patients, we examined precision of memory on a serial order task, in which participants observed four differently coloured oriented bars presented sequentially, one at a time at screen centre. Afterwards, they were asked to adjust a coloured probe bar’s orientation to match the orientation of the bar with the same colour in the sequence. We quantified precision as the reciprocal of the standard deviation of error in response orientation. The results show a deficit in WM precision in drug-naïve PD patients compared to age-matched controls. But this deficit was restored back to normal within 2-3 months of being treated with a regular daily dopamine agonist medication. Sensorimotor control tasks showed no change in performance pre- and post-medication, and compared to age-matched controls. We next investigated the effect of a single dose (1.5 mg) of cabergoline, a dopamine agonist, and placebo in healthy young participants performing the same WM task. The results showed that the effect of cabergoline on performance was dependent on participants’ baseline performance. While high baseline performers were impaired with cabergoline, those with low baseline performance improved on the drug. There was a negative correlation between improvement in precision on medication and baseline performance. These findings demonstrate that dopaminergic stimulation can improve WM precision in PD patients and healthy low performing individuals. Conversely, it can impair performance in healthy high performers, consistent with the view that there might be an inverted U-shaped function relating dopaminergic dose to optimal WM precision.
Meeting abstract presented at VSS 2012