Saccadic latency during electrical stimulation of the human subthalamic nucleus

Yasin Temel, Veerle Visser-Vandewalle, R.H.S. Carpenter
Current Biology, Vol 18, R412-R414, 20 May 2008

High-frequency electrical stimulation of the subthalamic nucleus (‘deep brain stimulation’) has rapidly become a popular method for treating patients with Parkinson's disease [1], and is now widely recognised as one of the most effective long-term treatments. So far, the neural mechanisms underlying its effectiveness have been elusive. However, measuring saccadic latency — the time taken to look at a sudden visual stimulus — seems a promising approach. Latency varies randomly from trial to trial, and analysis of the resultant statistical distributions provides information about the parameters of the underlying decision-making mechanisms of the brain. Measurement of these parameters can then provide a sensitive and non-invasive way of quantifying the effects of clinical interventions, and providing information about the underlying neural mechanisms. In a group of Parkinson patients with electrodes previously implanted in the subthalamic nuclear complex, we found that bilateral electrical stimulation dramatically reduces the time taken to initiate a saccade. The effect on the distribution of latency corresponds to an increase in the rate of accumulation of the underlying decision signal, suggesting that stimulating this region specifically enhances the gain of descending pathways through the basal ganglia that contribute to saccadic initiation.

Fulltext: http://download.current-biology.com/pdfs/0960-9822/PIIS0960982208003059.pdf