Scene coherence can affect the local response to natural images in human V1

Abstract

Neurons in primary visual cortex (V1) can be indirectly affected by visual stimulation positioned outside their receptive fields. Although this contextual modulation is intensely studied, we have little notion of how it manifests with naturalistic stimulation. Here, we investigated how the V1 response to a natural image fragment is affected by spatial context that is consistent or inconsistent with the scene from which it was extracted. Using fMRI at 7T, we measured the BOLD signal in human V1 (n=8) while participants viewed an array of apertures. Most apertures showed fragments from a single scene, yielding a dominant perceptual interpretation which participants were asked to categorize, and the remaining apertures each showed fragments drawn from a set of 20 scenes. We find that the V1 response was significantly increased for apertures showing image structure that was coherent with the dominant scene relative to the response to the same image structure when it was non-coherent. Additional analyses suggest that this effect was mostly evident for apertures in the periphery of the visual field, that it peaked towards the centre of the aperture, and that peaked in the middle to superficial regions of the cortical gray matter. These findings suggest that knowledge of typical spatial relationships is embedded in the circuitry of contextual modulation. Such mechanisms, possibly augmented by contributions from attentional factors, serve to increase the local V1 activity under conditions of contextual consistency.

Normalization by orientation-tuned surround in human V1-V3

“…In closed-loop experiments in which models are used in real time to find the optimal stimulus for mouse V1 cells, the most effective stimuli were often quite complex, differing from simple Gabor patterns [ 23 ]. In human fMRI studies, the responses to natural/complex images in V1 also appear to be influenced by statistical dependencies and image context [ 24 , 25 ], factors unlikely to influence the predictions of the normalized energy model. Even in relatively simple artificial images with a fixed amount of total contrast energy, the BOLD response is lower when there is a single orientation compared to when there are two divergent orientations [ 26 , 27 ].…”

Normalization by orientation-tuned surround in human V1-V3

“…Other studies with single unit electrophysiology found that a normalization model could be successful but only if the normalization was flexible, such that its strength depended on statistical dependencies in the image (Coen-Cagli et al, 2015). In human fMRI studies, the responses to natural/complex images in V1 also appear to be influenced by statistical dependencies and image context (Mannion et al, 2015;Qiu et al, 2016), factors unlikely to influence the predictions of the normalized energy model.…”

Temporal multivariate pattern analysis (tMVPA): A single trial approach exploring the temporal dynamics of the BOLD signal

“…Even at 3 T, where voxels traditionally measure 2–3 mm isotropic resolutions, MVPA can successfully extract neural information – such as orientation preference (Kamitani and Tong, 2005) – which exists at a much finer spatial scale than the resolution of single voxels. These approaches are believed to increase the sensitivity to such fine-grained information present in lower resolution images by exploiting the micro-feature-selective biases of single voxels that stem from the variability of the distribution of cortical columns or their vascular architecture (Op de Beeck, 2010; Freeman et al, 2011; Kamitani and Tong, 2005; Mannion et al, 2009, 2015; Sasaki et al, 2006).…”