Bilateral saccadic deficits following large and reversible inactivation of unilateral frontal eye field.

Authors

Tyler R Peel, The Brain and Mind Institute, London, Ontario, Canada & Graduate Program in Neuroscience, Western University, London, Ontario, Canada
Kevin Johnston, The Brain and Mind Institute, London, Ontario, Canada & Department of Physiology and Pharmacology, Western University, London, Ontario, Canada & Department of Psychology, Western University, London, Ontario, Canada
Stephen G Lomber, The Brain and Mind Institute, London, Ontario, Canada & Department of Physiology and Pharmacology, Western University, London, Ontario, Canada & Department of Psychology, Western University, London, Ontario, Canada & Graduate Program in Neuroscience, Western University, London, Ontario, Canada
Brian D Corneil, The Brain and Mind Institute, London, Ontario, Canada & Robarts Research Institute, London, Ontario, Canada & Department of Physiology and Pharmacology, Western University, London, Ontario, Canada & Department of Psychology, Western University, London, Ontario, Canada & Graduate Program in Neuroscience, Western University, London, Ontario, CanadaFollow

Document Type

Article

Publication Date

1-1-2014

Journal

Journal of neurophysiology

Volume

111

Issue

2

First Page

415

Last Page

433

URL with Digital Object Identifier

10.1152/jn.00398.2013

Abstract

Inactivation permits direct assessment of the functional contribution of a given brain area to behavior. Previous inactivation studies of the frontal eye field (FEF) have either used large permanent ablations or reversible pharmacological techniques that only inactivate a small volume of tissue. Here we evaluated the impact of large, yet reversible, FEF inactivation on visually guided, delayed, and memory-guided saccades, using cryoloops implanted in the arcuate sulcus. While FEF inactivation produced the expected triad of contralateral saccadic deficits (increased reaction time, decreased accuracy and peak velocity) and performance errors (neglect or misdirected saccades), we also found consistent increases in reaction times of ipsiversive saccades in all three tasks. In addition, FEF inactivation did not increase the proportion of premature saccades to ipsilateral targets, as was predicted on the basis of pharmacological studies. Consistent with previous studies, greater deficits accompanied saccades toward extinguished visual cues. Our results attest to the functional contribution of the FEF to saccades in both directions. We speculate that the comparative effects of different inactivation techniques relate to the volume of inactivated tissue within the FEF. Larger inactivation volumes may reveal the functional contribution of more sparsely distributed neurons within the FEF, such as those related to ipsiversive saccades. Furthermore, while focal FEF inactivation may disinhibit the mirroring site in the other FEF, larger inactivation volumes may induce broad disinhibition in the other FEF that paradoxically prolongs oculomotor processing via increased competitive interactions.