RT Journal Article
SR Electronic
T1 Saccade Modulation by Optical and Electrical Stimulation in the Macaque Frontal Eye Field
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 16684
OP 16697
DO 10.1523/JNEUROSCI.2675-13.2013
VO 33
IS 42
A1 Shay Ohayon
A1 Piercesare Grimaldi
A1 Nicole Schweers
A1 Doris Y. Tsao
YR 2013
UL http://www.jneurosci.org/content/33/42/16684.abstract
AB Recent studies have demonstrated that strong neural modulations can be evoked with optogenetic stimulation in macaque motor cortex without observing any evoked movements (Han et al., 2009, 2011; Diester et al., 2011). It remains unclear why such perturbations do not generate movements and if conditions exist under which they may evoke movements. In this study, we examine the effects of five optogenetic constructs in the macaque frontal eye field and use electrical microstimulation to assess whether optical perturbation of the local network leads to observable motor changes during optical, electrical, and combined stimulation. We report a significant increase in the probability of evoking saccadic eye movements when low current electrical stimulation is coupled to optical stimulation compared with when electrical stimulation is used alone. Experiments combining channelrhodopsin 2 (ChR2) and electrical stimulation with simultaneous fMRI revealed no discernible fMRI activity at the electrode tip with optical stimulation but strong activity with electrical stimulation. Our findings suggest that stimulation with current ChR2 optogenetic constructs generates subthreshold activity that contributes to the initiation of movements but, in most cases, is not sufficient to evoke a motor response.