Distinct effects of trial-driven and task Set-related control in primary visual cortex

Abstract

Task sets are task-specific configurations of cognitive processes that facilitate task-appropriate reactions to stimuli. While it is established that the trial-by-trial deployment of visual attention to expected stimuli influences neural responses in primary visual cortex (V1) in a retinotopically specific manner, it is not clear whether the mechanisms that help maintain a task set over many trials also operate with similar retinotopic specificity. Here, we address this question by using BOLD fMRI to characterize how portions of V1 that are specialized for different eccentricities respond during distinct components of an attention-demanding discrimination task: cue-driven preparation for a trial, trial-driven processing, task-initiation at the beginning of a block of trials, and task-maintenance throughout a block of trials. Tasks required either unimodal attention to an auditory or a visual stimulus or selective intermodal attention to the visual or auditory component of simultaneously presented visual and auditory stimuli. We found that while the retinotopic patterns of trial-driven and cue-driven activity depended on the attended stimulus, the retinotopic patterns of task-initiation and task-maintenance activity did not. Further, only the retinotopic patterns of trial-driven activity were found to depend on the presence of intermodal distraction. Participants who performed well on the intermodal selective attention tasks showed strong task-specific modulations of both trial-driven and task-maintenance activity. Importantly, task-related modulations of trial-driven and task-maintenance activity were in opposite directions. Together, these results confirm that there are (at least) two different processes for top-down control of V1: One, working trial-by-trial, differently modulates activity across different eccentricity sectors—portions of V1 corresponding to different visual eccentricities. The second process works across longer epochs of task performance, and does not differ among eccentricity sectors. These results are discussed in the context of previous literature examining top-down control of visual cortical areas.

Retinotopic patterns of functional connectivity between V1 and large-scale brain networks during resting fixation

“…Sustained signals from the cingulo-opercular network are related to the maintenance of task sets (Dosenbach et al 2008; Nelson et al, 2010), though their precise function remains unclear (Dubis et al 2014). Recent work by our lab has demonstrated that sustained task-driven responses occur in early visual areas including V1 (Elkhetali et al 2015), but do not show the spatial specificity of cue-driven and stimulus-driven responses (Griffis et al 2015b). While we have interpreted these sustained V1 responses as reflecting ongoing task maintenance signals that are likely to have originated in the cingulo-opercular network, it is unclear why this network would show preferential connectivity to the near-periphery of V1 during fixation.…”

“…Task and stimulus details have been described in detail elsewhere (Elkhetali et al 2015; Griffis et al 2015b), and will only be briefly described here, as current analyses focus on the rest periods only. Task blocks consisted of unimodal and bimodal visual and auditory attention tasks.…”

“…While retinotopic localizers were performed during the first scan session as described in our previous publications (Elkhetali et al 2015; Griffis et al 2015b), they were not used to define the primary V1 regions of interest in the current study for several reasons. Primarily, the retinotopic localizers obtained for these participants only mapped to approximately 8° visual angle, whereas using the Freesurfer anatomical template enables the inclusion of the entirety of V1.…”

“…the sector of the V1 label with an estimated eccentricity of 1.3° visual angle according to the probabilistic template) without loss of generalizability. Nonetheless, because retinotopic mapping was performed on these participants, supplemental analyses were performed using retinotopically defined calcarine sulcus regions of interest that were described in our previous publication (Griffis et al 2015b) in order to provide a more complete characterization of the data and to demonstrate that our results do not differ substantially when alternate ROI definitions are employed.…”

Age-Dependent Cortical Thinning of Peripheral Visual Field Representations in Primary Visual Cortex

“…These include differences in the cellular structure of retinal inputs to the lateral geniculate nucleus (LGN; Curcio and Allen, 1990; Dacey, 1993; Neitz et al, 2006), neuronal density (Collins et al, 2010), inter-regional connections (Hadjikhani and Tootell, 2000; Clavagnier et al, 2004; Palmer and Rosa, 2006), sensitivity to threatening stimuli (Bayle et al, 2009; Gomez et al, 2011), responses during cross-modal attention (Cate et al, 2009; Griffis et al, 2015), and modulation of activity by spatial attention (Roberts et al, 2007). Thus, it is reasonable to hypothesize that foveal vs. peripheral retinotopic representations in V1 might be differentially affected by processes such as aging.…”