The evolution of a disparity decision in human visual cortex

Abstract

We used fMRI-informed EEG source-imaging in humans to characterize the dynamics of cortical responses during a disparity-discrimination task. After the onset of a disparity-defined target, decision-related activity was found within an extended cortical network that included several occipital regions of interest (ROIs): V4, V3A, hMT+ and the Lateral Occipital Complex (LOC). By using a response-locked analysis, we were able to determine the timing relationships in this network of ROIs relative to the subject's behavioral response. Choice-related activity appeared first in the V4 ROI almost 200 ms before the button press and then subsequently in the V3A ROI. Modeling of the responses in the V4 ROI suggests that this area provides an early contribution to disparity discrimination. Choice-related responses were also found after the button-press in ROIs V4, V3A, LOC and hMT+. Outside the visual cortex, choice-related activity was found in the frontal and temporal pole before the button-press. By combining the spatial resolution of fMRI-informed EEG source imaging with the ability to sort out neural activity occurring before, during and after the behavioral manifestation of the decision, our study is the first to assign distinct functional roles to the extra-striate ROIs involved in perceptual decisions based on disparity, the primary cue for depth.

Specialization of mid-tier stages of dorsal and ventral pathways in stereoscopic processing

“…Moreover, MT and V4 share a common link between the disparity-tuning shape and the type of disparity representation. It is possible that the interactions between the dorsal and ventral pathways play several roles in solving the correspondence problem, deriving 3D object representation, making decision about stereoscopic depth, and generating object-oriented motor action (e.g., reaching and grasping), as suggested by a broad range of evidence from neuroanatomy, single-neuron recording, electro-encephalography, psychophysics, and brain imaging (Borra et al, 2008(Borra et al, , 2010Cottereau et al, 2014;Farivar, 2009;Fujita and Doi, 2016;Freud et al, 2016;Janssen et al, 2018;Van Polanen and Davare, 2015).…”

How to use fMRI functional localizers to improve EEG/MEG source estimation

“…As an example, figure 4 shows the results obtained in one of our previous EEG studies where we were interested in the cortical mechanisms implied in decision-making (Cottereau et al, 2014b). …”

“…This comparison is shown for stimulus-locked (figure 4C) and response-locked (figure 4D) data. The complete details of the analysis and the responses in the other ROIs can be found in (Cottereau et al, 2014b). What is interesting to observe is how different the shapes of the responses in the three ROIs are.…”

“…D) Comparison between the response-locked data (blue) and a surrogate dataset computed from the Misses (red) in the 3 same ROIs. Figure adapted from Cottereau et al (2014b).…”

“…Functional ROI-based comparisons both simplify and increase the accuracy of the pooling of the results between subjects, because a co-registration of the individual anatomies, with its inevitable distortion is not necessary. Over the last several years, this approach has been used to study different properties of the visual system: motion processing (Cottereau et al, 2014a; Ales and Norcia, 2009), chromatic processing (Wang and Wade, 2011; Xiao and Wade, 2010), binocular disparity processing (Cottereau et al, 2011; 2012bc), attention (Kim and Verghese, 2012; Verghese et al, 2012; Palomares et al, 2012; Lauritzen et al, 2010), figure-ground segmentation (Appelbaum et al, 2006; 2008; 2010), perceptual decision-making (Cottereau et al, 2014b; Ales et al, 2013) and contrast normalization (Busse et al, 2009; Tsai et al, 2012). Beyond the scope of the visual system, this approach can easily be applied to other sensory systems where fMRI can be used to reliably map functional areas (see e.g.…”