title: Neural correlates of target selection for reaching movements in superior colliculus.
abstract: We recently demonstrated that inactivation of the primate superior colliculus (SC) causes a deficit in target selection for arm-reaching movements when the reach target is located in the inactivated field (Song JH, Rafal RD, McPeek RM. Proc Natl Acad Sci USA 108: E1433-E1440, 2011). This is consistent with the notion that the SC is part of a general-purpose target selection network beyond eye movements. To understand better the role of SC activity in reach target selection, we examined how individual SC neurons in the intermediate layers discriminate a reach target from distractors. Monkeys reached to touch a color oddball target among distractors while maintaining fixation. We found that many SC neurons robustly discriminate the goal of the reaching movement before the onset of the reach even though no saccade is made. To identify these cells in the context of conventional SC cell classification schemes, we also recorded visual, delay-period, and saccade-related responses in a delayed saccade task. On average, SC cells that discriminated the reach target from distractors showed significantly higher visual and delay-period activity than nondiscriminating cells, but there was no significant difference in saccade-related activity. Whereas a majority of SC neurons that discriminated the reach target showed significant delay-period activity, all nondiscriminating cells lacked such activity. We also found that some cells without delay-period activity did discriminate the reach target from distractors. We conclude that the majority of intermediate-layer SC cells discriminate a reach target from distractors, consistent with the idea that the SC contains a priority map used for effector-independent target selection.
authors.affiliation: Department of Cognitive, Linguistic & Psychological Sciences, Brown University, Providence, Rhode Island; Brown Institute for Brain Science, Brown University, Providence, Rhode Island; The Smith-Kettlewell Eye Research Institute, San Francisco, California; and joo-hyun_song@brown.edu.
authors.forename: Joo-Hyun
authors.initials: JH
authors.lastname: Song
authors.affiliation: The Smith-Kettlewell Eye Research Institute, San Francisco, California; and Graduate Center for Vision Research and SUNY Eye Institute, SUNY College of Optometry, New York, New York.
authors.forename: Robert M
authors.initials: RM
authors.lastname: McPeek
mesh_terms: D000818:Animals; D004192:Discrimination, Psychological; D006225:Hand / Q000294:innervation / Q000502:physiology; D008253:Macaca mulatta; D009068:Movement; D009474:Neurons / Q000145:classification / Q000502:physiology*; D011597:Psychomotor Performance; D013477:Superior Colliculi / Q000166:cytology / Q000502:physiology*
keywords: reaching; superior colliculus; target selection