Saccade Planning Evokes Topographically Specific Activity in the Dorsal and Ventral Streams

Abstract

Saccade planning may invoke spatially-specific feedback signals that bias early visual activity in favor of top-down goals. We tested this hypothesis by measuring cortical activity at the early stages of the dorsal and ventral visual processing streams. Human subjects maintained saccade plans to (prosaccade) or away (antisaccade) from a spatial location over long memory-delays. Results show that cortical activity persists in early visual cortex at the retinotopic location of upcoming saccade goals. Topographically specific activity persists as early as V1, and activity increases along both dorsal (V3A/B, IPS0) and ventral (hV4, VO1) visual areas. Importantly, activity persists when saccade goals are available only via working memory and when visual targets and saccade goals are spatially disassociated. We conclude that top-down signals elicit retinotopically specific activity in visual cortex both in the dorsal and ventral streams. Such activity may underlie mechanisms that prioritize locations of task-relevant objects.

Neural Differences between Covert and Overt Attention Studied using EEG with Simultaneous Remote Eye Tracking

“…Response amplitudes did not significantly differ between covert and overt shift conditions. Therefore, the suggestion that saccade planning can enhance brain activity related to visual processing (Saber et al, 2015) was not confirmed in this study. Enhancement due to planning a saccade may not be significantly different from that due to planning a lateralized manual response.…”

“…Functional MRI has been used to investigate covert and overt attention shifts (e.g., Corbetta et al, 1998; Kelley et al, 2008), but its low temporal resolution does not allow eye movements artifacts to be excluded unless subjects are instructed to delay their eye movements (memory guided saccades, e.g., Saber et al, 2015). The temporal resolution of EEG allows selection of data from the period before saccade onset (here up to 180 ms from target onset).…”

“…The visual components of neural responses were expected to be similar for the identical visual stimuli in the overt and covert attention conditions. Previous studies have suggested that saccade planning can enhance brain activity related to visual processing (Saber et al, 2015) and that saccade planning may also involve fronto-central and prefrontal areas (Neggers et al, 2005). Therefore, we looked for differential frontal activation in overt compared to covert attention shift conditions.…”

The Müller-Lyer illusion affects visuomotor updating in the dorsal visual stream

“…Anti-reach and anti-saccade tasks have been performed to distinguish between sensory target representations and movement plans. During the delay phase preceding a pro-or anti-saccade, the PPC shows a sustained response to both the visual target and the saccade goal, with a stronger response to the visual stimulus during the first part of the delay, and a stronger response to the saccade goal during the second part of the delay (Medendorp et al, 2005;Saber et al, 2015;Van Der Werf et al, 2008). In contrast, participants who were adapted to left-right reversing prisms in a delayed reaching task showed directional selectivity in the PPC that was fixed to the visual coordinates of the remembered goal throughout the delay (Fernandez-ruiz et al, 2007).…”

Parietal and Frontal Cortex Encode Stimulus-Specific Mnemonic Representations during Visual Working Memory

“…More recent human neuroimaging studies have used multivariate analyses to successfully decode simple visual features or spatial positions held in WM from delay-period multivoxel activation patterns in regions of posterior occipital and parietal cortex (see Serences et al, 2009; Harrison and Tong, 2009; Ester et al, 2009; Riggall and Postle, 2012; Emrich et al, 2013; Christophel et al, 2012, 2015; Jerde et al, 2012; Saber et al, 2015). Importantly, sustained activity changes can be dissociated from information storage during WM, as decoding is often successful even though the amplitude of the blood-oxygenation-level-dependent (BOLD) response typically returns to baseline levels during the memory delay period (Serences et al, 2009; Harrison and Tong, 2009; Riggall and Postle, 2012; Emrich et al, 2013).…”