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Erin M Woller, Rachel J Tesla, Bertram R Payne, Stephen G Lomber; Cortico-collicular interactions mediating visual attention. Journal of Vision 2003;3(9):471. doi: 10.1167/3.9.471.
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Unilateral deactivation of cat posterior middle suprasylvian (pMS) sulcal cortex or the superior colliculus (SC) results in a contralateral neglect, with the cats unable to report the position of visual stimuli introduced into the contralateral visual hemifield. To compare the interactive effects of cortical and collicular deactivations on visual attention, we implanted cooling loops bilaterally in the pMS sulcus and over the dorsal surface of the SC in three cats. As expected, unilateral deactivation of either pMS cortex or the SC in the right hemisphere resulted in an elimination of visual orienting responses into the left visual field. This deficit was reversed by additional deactivation of the homotopic site in the left hemisphere. However, deactivation of the heterotopic locus did not yield the same result. During deactivation of right pMS cortex, additional deactivation of the left SC was sufficient to restore some visual orienting responses into the left visual field. The opposite order of deactivations did not yield the same result. During cooling of the right SC, additional deactivation of the left pMS cortex was unable to restore visual orienting responses into the left field. Therefore, while left SC deactivation was capable of restoring orienting responses following right pMS cortex cooling, left pMS sulcus deactivation following right SC deactivation was unable to achieve the same restoration. Simultaneous cooling of pMS cortex and the SC in the same hemisphere also resulted in an orienting deficit in the contralateral hemifield, yet additional deactivation of the opposite pMS cortex was unable to restore orienting responses into the neglect hemifield, whereas deactivation of the opposite SC did result in a partial restoration. Finally, deactivation of all four loci resulted in nearly normal orienting performance throughout the visual field. Therefore, dynamic interactions both between and within the two sides of the brain mediate visual attention.
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