![]() ![]() ![]() Electrical microstimulation of the SCi in monkeys induces saccades 25, and the properties of the evoked movements are modulated by stimulation parameters and the location of stimulation within the SC, with larger saccade responses (e.g., peak velocity) evoked using stronger stimulation parameters and larger amplitude saccades evoked by moving toward the caudal SCi 26. Moreover, the SCi projects to the premotor circuitry in the brainstem that initiates the orienting response 8, 10, 24. The SCs receives visual signals from the retina and visual cortex, whereas the SCi receives multisensory and cognitive inputs from various cortical and subcortical areas 15– 18, including structures and neuromodulatory systems involved in the control of pupil size, such as the locus coeruleus (LC), frontal eye field (FEF), and cholinergic projections from the pedunculopontine tegmental nucleus (PPTN) 19– 23. The SC is organized into a retinotopic map of contralateral visual space and has anatomically and functionally differentiated superficial (SCs) and intermediate/deep (SCi) layers 14. Are the neural mechanisms underlying the cognitive modulation for pupil size similar to those for saccades? Further, what is the role of the SC in coordinating saccade and pupil responses? Pupil size and saccadic eye movements are becoming popular and promising indices of cognitive and disease processes 13. Recent evidence, particularly in monkeys, has shown that pupil dilation is evoked by presentation of a visual target, enhanced by acoustic stimuli, modulated by stimulus saliency, and triggered by microstimulation of the superior colliculus (SC) 4– 7, a midbrain sensorimotor center that is phylogenetically conserved and causally involved in producing orienting responses 8– 12. Our results demonstrate an integrated role of the SC on coordinating saccade and pupil responses, characterizing luminance independent modulation in the SC, together elucidating the differentiated pathways underlying this behavior.Ī series of responses, including saccadic eye movements and pupil dilation, are evoked by the presentation of a salient stimulus as part of the orienting response 1– 3. Global luminance only modulated pupil, but not, saccade responses. Stimulation frequency modulated saccade and pupil responses, with trial-by-trial correlations between the two responses. Here, we used microstimulation to causally determine how the SC coordinates saccade and pupil responses, and whether global luminance modulates these responses by varying stimulation frequency and global luminance in male monkeys. The SC also receives global luminance signals from the retina, but whether global luminance modulates saccade and pupil responses coordinated by the SC remains unknown. Although the role of the superior colliculus (SC) in saccade and pupil dilation has been established separately, whether and how these responses are coordinated remains unknown. The appearance of a salient stimulus evokes saccadic eye movements and pupil dilation as part of the orienting response. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |