| Abstract No.: | B-G2188 |
| Country: | Canada |
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| Title: | EFFECT OF MICROSTIMULATION OF MACAQUE ANTERIOR CINGULATED ON PRO- AND ANTI-SACCADES AFTER A TASK SWITCH |
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| Authors/Affiliations: | 1 Jessica M Phillips*; 1 Kevin Johnston; 1 Stefan Everling;
1 University of Western Ontario, London, ON, Canada.
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| Content: | The dorsal anterior cingulate cortex (ACC) has been implicated in decision-making, error detection, task-switching, and other aspects of executive control. We have recently demonstrated that ACC neurons exhibit an increased task-selectivity following a task switch when monkeys were required to alternate between blocks of pro- and anti-saccade trials (Johnston, Levin, Koval and Everling (2007) Neuron 53: 453-62). This task-selectivity was attenuated as the blocks progressed.
OBJECTIVE: We have further investigated the ACC’s role in top-down control and in task-switching by administering electrical microstimulation in the ACC while monkeys performed alternating blocks of pro- and anti-saccades. The animals had to acquire the correct task rule by trial and error based on the delivery or omission of reward after each trial.
MATERIALS AND METHODS: 3 macaque monkeys were included in these experiments. Experimental paradigm was identical to that used in the Johnston (2007) study. Microstimulation pulse trains were administered (biphasic, 0.3 ms, 100 Hz, 50 microA) 200 ms prior to stimulus presentation and persisted for a duration of 300 ms. Eye movements were recorded using magnetic search coil technique and infrared video eye-tracking.
RESULTS: Microstimulation resulted in increased reaction times and more errors committed in comparison to no stimulation trials for pro-saccades in the contralateral direction to the stimulation site. The microstimulation-induced errors were highest after switching to pro-saccades from anti-saccades, and this effect decreased throughout the block, disappearing by the end. Reaction times for anti-saccades generated in both directions were decreased compared to the no stimulation condition, and this effect was present throughout the entire block (not switch-dependent).
CONCLUSION: These results support a role for the ACC in top-down control and task switching from anti- to pro-saccades. Namely, microstimulation in the ACC appears to create a bias in the oculomotor network in favour of the antisaccade task, which requires a higher level of cognitive control.
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