Clustered functional domains for curves and corners in cortical area V4

Abstract

The ventral visual pathway is crucially involved in integrating low-level visual features into complex representations for objects and scenes. At an intermediate stage of the ventral visual pathway, V4 plays a crucial role in supporting this transformation. Many V4 neurons are selective for shape segments like curves and corners, however it remains unclear whether these neurons are organized into clustered functional domains, a structural motif common across other visual cortices. Using two-photon calcium imaging in awake macaques, we confirmed and localized cortical domains selective for curves or corners in V4. Single-cell resolution imaging confirmed that curve or corner selective neurons were spatially clustered into such domains. When tested with hexagonal-segment stimuli, we find that stimulus smoothness is the cardinal difference between curve and corner selectivity in V4. Combining cortical population responses with single neuron analysis, our results reveal that curves and corners are encoded by neurons clustered into functional domains in V4. This functionally-specific population architecture bridges the gap between the early and late cortices of the ventral pathway and may serve to facilitate complex object recognition.

Large-scale calcium imaging reveals a systematic V4 map for encoding natural scenes

“…Additionally, domains that prefer straight borders may correspond to previously reported orientation domains 52 . We also found domains that prefer curvature or round objects, which may correspond to previously reported curvature domains [54][55][56] . Our results indicate that some artificially designed stimulus features, such as color, orientation, and curvature, are indeed important features in natural scenes encoded by the V4 neural population.…”

Columnar processing of border ownership in primate visual cortex

“…Functional clustering is a recurring theme in primate cortical visual areas ( Hubel and Livingstone, 1987 ), and has been reported for several modalities in V4 including orientation, hue, direction of motion, spatial frequency, and recently curvature ( Hu et al, 2020 ; Jiang et al, 2021 ; Li et al, 2013 ; Liu et al, 2020 ; Lu et al, 2018 ; Roe et al, 2012 ; Tang et al, 2020 ; Tanigawa et al, 2010 ). We find here that border ownership preference is preserved across layers within a vertical penetration, indicating that this modality is also organized in a columnar fashion.…”

High-density recording reveals sparse clusters (but not columns) for shape and texture encoding in macaque V4

“…When studies could examine tuning similarity, e.g. with multiphoton imaging of single neuron responses, or with electrode recording across layers, authors have found considerable diversity in the tuning of nearby neurons (Jiang et al, 2021; Tang et al, 2020). For example, using electrode recordings, Li and colleagues found consistency in categorical organization across layers, i.e.…”

“…In the face of this hurdle, studies in V4 and inferior temporal cortex have typically used optical imaging, and more recently multiphoton imaging, to evaluate clustered tuning at a categorical level, e.g. preferred tuning for curved vs rectilinear stimuli or 2D vs 3D shapes, and across the cortical sheet rather than across laminae (Hu et al, 2020; Jiang et al, 2021; Li et al, 2013; Lu et al, 2018; Sato et al, 2009; Srinath et al, 2021; Tang et al, 2020; Tanigawa et al, 2010). Here, for the first time, we leverage the use of high-density Neuropixels probes to examine the fine-scale columnar structure, namely the similarity in the profile of the tuning curve, for shape and texture encoding in cortical area V4 of the awake primate.…”