Interpreting sensory and cognitive signals in the cortical reading network

Receptive field properties measured in the reading portion of the ventral occipital-temporal (VOT) cortex are task- and stimulus-dependent. To understand these effects, we analyzed responses in visual field-maps (V1-3, hV4, VO1) whose signals are likely inputs to the VOT. Within these maps, each voxel contains neurons that are responsive to specific regions of the visual field; these regions can be quantified using the moving bar paradigm and population receptive field (pRF) analysis. We measured pRFs using several types of contrast patterns within the bar (English words, Hebrew words, checkers, and false fonts). Word and false-font stimuli produce estimates that are as much as 3-4 deg closer to the fovea than checker stimuli in all visual field maps, becoming very pronounced in V3, hV4 and VO-1. The responses in the visual field maps suggest that the pRF shifts depend mostly on the visual characteristics of the stimulus, and may be explained by sensory signal models and their known neural circuitry. Responses in the VOT reading regions do not follow the same pattern as the visual maps. The pRF centers are confined to the central five degrees, and the responses to false-fonts differ from the responses to words. To understand these VOT signals, we suggest it is necessary to extend the sensory pRF model to include an explicit cognitive signal that distinguishes words from false-fonts.

Human primary visual cortex shows larger population receptive fields for binocular disparity-defined stimuli

The visual perception of 3D depth is underpinned by the brain’s ability to combine signals from the left and right eyes to produce a neural representation of binocular disparity for perception and behaviour. Electrophysiological studies of binocular disparity over the past 2 decades have investigated the computational role of neurons in area V1 for binocular combination, while more recent neuroimaging investigations have focused on identifying specific roles for different extrastriate visual areas in depth perception. Here we investigate the population receptive field properties of neural responses to binocular information in striate and extrastriate cortical visual areas using ultra-high field fMRI. We measured BOLD fMRI responses while participants viewed retinotopic mapping stimuli defined by different visual properties: contrast, luminance, motion, correlated and anti-correlated stereoscopic disparity. By fitting each condition with a population receptive field model, we compared quantitatively the size of the population receptive field for disparity-specific stimulation. We found larger population receptive fields for disparity compared with contrast and luminance in area V1, the first stage of binocular combination, which likely reflects the binocular integration zone, an interpretation supported by modelling of the binocular energy model. A similar pattern was found in region LOC, where it may reflect the role of disparity as a cue for 3D shape. These findings provide insight into the binocular receptive field properties underlying processing for human stereoscopic vision.

Human primary visual cortex shows larger population receptive fields for binocular disparity-defined stimuli

1AbstractThe visual perception of 3D depth is underpinned by the brain’s ability to combine signals from the left and right eyes to produce a neural representation of binocular disparity for perception and behavior. Electrophysiological studies of binocular disparity over the past two decades have investigated the computational role of neurons in area V1 for binocular combination, while more recent neuroimaging investigations have focused on identifying specific roles for different extrastriate visual areas in depth perception. Here we investigate the population receptive field properties of neural responses to binocular information in striate and extrastriate cortical visual areas using ultra-high field fMRI. We measured BOLD fMRI responses while participants viewed retinotopic-mapping stimuli defined by different visual properties: contrast, luminance, motion, correlated and anti-correlated stereoscopic disparity. By fitting each condition with a population receptive field model, we compared quantitatively the size of the population receptive field for disparity-specific stimulation. We found larger population receptive fields for disparity compared with contrast and luminance in area V1, the first stage of binocular combination, which likely reflects the binocular integration zone, an interpretation supported by modelling of the binocular energy model. A similar pattern was found in region LOC, where it may reflect the role of disparity as a cue for 3D shape. These findings provide insight into the binocular receptive field properties underlying processing for human stereoscopic vision.

Human Primary Visual Cortex Shows Larger Population Receptive Fields for Binocular Disparity-Defined Stimuli

The visual perception of 3D depth is underpinned by the brain's ability to combine signals from the left and right eyes to produce a neural representation of binocular disparity for perception and behavior. Electrophysiological studies of binocular disparity over the past two decades have investigated the computational role of neurons in area V1 for binocular combination, while more recent neuroimaging investigations have focused on identifying specific roles for different extrastriate visual areas in depth perception. Here we investigate the neural population receptive field properties of responses to binocular information in striate and extrastriate cortical visual areas using ultra-high field fMRI. We measured BOLD fMRI responses while participants viewed retinotopic-mapping stimuli defined by different visual properties: contrast, luminance, motion, correlated and anti-correlated stereoscopic disparity. By fitting each condition with a population receptive field model, we were able to compare quantitatively the size of the population receptive field for disparity-defined vs not disparity-defined stimulation conditions. We found larger population receptive fields for disparity compared to the contrast and luminance stimuli in area V1, the first stage of binocular combination, which likely reflects the binocular integration zone, an interpretation supported by modelling of the binocular energy model. A similar pattern was found in region LOC, where it may reflect the role of disparity as a cue for 3D shape. These findings provide insight into the binocular receptive field properties underlying processing for human stereoscopic vision.

Sensory coding of limb kinematics in developing primary motor cortex

Primary motor cortex (M1) undergoes protracted development in rodents, functioning initially as a sensory structure. As we reported previously in neonatal rats (Dooley and Blumberg, 2018), self-generated forelimb movements—especially the twitch movements that occur during active sleep—trigger sensory feedback (reafference) that strongly activates M1. Here, we expand our investigation by using a video-based approach to quantify the kinematic features of forelimb movements with sufficient precision to reveal receptive-field properties of individual M1 units. At postnatal day (P) 8, nearly all M1 units were strongly modulated by movement amplitude, but only during active sleep. By P12, the majority of M1 units no longer exhibited amplitude-dependence, regardless of sleepwake state. At both ages, movement direction produced changes in M1 activity, but to a much lesser extent than did movement amplitude. Finally, we observed that population spiking activity in M1 becomes more continuous and decorrelated between P8 and P12. Altogether, these findings reveal that M1 undergoes a sudden transition in its receptive field properties and population-level activity during the second postnatal week. This transition marks the onset of the next stage in M1 development before the emergence of its later-emerging capacity to influence motor outflow.

Learning receptive field properties of complex cells in V1

The authors have withdrawn their manuscript due to a duplicate posting on our website. Please visit doi.org/10.1101/2020.05.18.101881 to access the current version of this preprint on bioRxiv