Saccadic eye movements evoked
by microstimulation of striate cortex.
Tehovnik EJ, Slocum WM, Schiller PH
Eur J Neurosci. 2003 Feb;17(4):870-8.
Experiments were performed to assess the excitability of neural elements activated
while inducing saccadic eye movements electrically from different cortical layers
of striate cortex (area V1) in rhesus monkeys. Excitability was assessed by measuring
current thresholds, saccadic latencies, chronaxies, and the effectiveness of anode-first
vs. cathode-first pulses. Minimum current thresholds for the evocation of saccades
(i.e. less than 5 microA) were observed when the deepest layers of V1 were stimulated.
The shortest saccadic latencies were also observed at these depths. The shortest
latency at 10 times the threshold current was 49 ms on average. The chronaxies
of the elements mediating saccades were less in deep V1 (i.e. 0.17 ms) than in
superficial V1 (i.e. 0.23 ms). Anode-first pulses were more effective at evoking
saccades from superficial V1, whereas cathode-first pulses were more effective
at evoking saccades from deep V1. These results indicate that the excitability
properties of superficial and deep V1 are distinct for the generation of saccades.
Moreover, the excitability of elements mediating saccades in V1 of monkeys is
comparable to that of elements mediating phosphenes in human V1.