Abstract
Natural vision involves processing complex visual information where multiple objects or features interact to influence current gaze position. Such interactions can be competitive (e.g. multiple salient items competing for foveation) or complimentary (e.g. using allocentric cues to help guide gaze shifts). Experimentally however; the influence of stimulus interactions are often ignored when the spatial response fields (RF) of visual neurons are mapped with single stimuli. Historically, it has been assumed that RFs are stable across altered task demands or stimuli complexity. This classical idea of stable RFs has been challenged recently by Cavanaugh et. al (JNeurosci, 2012) who showed that visual RFs in the frontal eye fields (FEF) were influenced by stimulus size. We hypothesized that lateral interactions (local excitation, distal inhibition) resulting from multiple stimuli should be apparent within individual FEF RFs since they represent computationally important elements of visuomotor transformations. To address this issue we recorded from visually responsive FEF neurons in head-free monkeys while they performed variants of a rapid visual RF mapping task. Complete visual RFs were mapped with 1 (control) or 2 simultaneously presented stimulus flashes. When a 2nd stimulus was presented, it could appear inside or outside of the classical RF. On some trials, a saccade target was presented (either inside or outside the RF) that remained visible during the RF mapping flashes and was saccaded to at the end of the trial. Results show that the addition of a 2nd stimulus or saccade target increased RF size and visual response magnitude when it was presented within the RF, whereas a 2nd stimulus presented outside the RF reduced RF size and visual response magnitude. These results provide insight into the nature of excitatory and inhibitory interactions between multiple visual stimuli in the FEF. Supported by CIHR, NSERC CREATE, and CRC.
Meeting abstract presented at VSS 2014