Abstract
The dorsal visual stream of the brain primarily processes visual spatial information, whereas the ventral visual stream processes the shape, category, and identity of visual objects. In primates, the ventral visual stream contains regions that preferentially respond to visual categories, such as faces and objects. However, even in the ventral visual stream, neural activity can be modulated by the location of an object in the visual field. Early visual areas are retinotopically organized, with many responding preferentially or exclusively to stimuli in the contralateral visual field. Early visual areas can also exhibit a preference for the upper or lower visual field. It is unclear how spatial preferences are retained as information travels down the ventral visual stream. In particular, it is not known whether shape selective areas in the inferior temporal cortex show spatial preferences. To assess the retinotopic dependence of face-selective areas, we measured fMRI responses in two rhesus macaques to the presentation of static monkey faces (and objects) in four quadrants of the visual field during a central fixation task. We evaluated responses in six face-selective areas, many of them in the superior temporal sulcus, and found they all exhibited a similar retinotopic pattern of activation. Activation was greater when complex objects were presented in the contralateral quadrants than in the ipsilateral quadrants of the visual field. Activation was also greater when faces were presented in the lower visual field quadrants than in the upper quadrants. The results suggest that visual field location information is retained throughout the ventral visual stream, and effects the processing of complex shape stimuli such as faces and objects. The preferences also suggest that a face in the lower hemifield of the visual field may be assessed and recognized more consistently than one in the upper half of the visual field.
Meeting abstract presented at VSS 2017