Influences of local and global context on local orientation perception

Abstract

Visual context modulates perception of local orientation attributes. These spatially very localised effects are considered to correspond to specific excitatory–inhibitory connectivity patterns of early visual areas as V1, creating perceptual tilt repulsion and attraction effects. Here, orientation misperception of small Gabor stimuli was used as a probe of this computational structure by sampling a large spatio‐orientation space to reveal expected asymmetries due to the underlying neuronal processing. Surprisingly, the results showed a regular iso‐orientation pattern of nearby location effects whose reference point was globally modulated by the spatial structure, without any complex interactions between local positions and orientation. This pattern of results was confirmed by the two perceptual parameters of bias and discrimination ability. Furthermore, the response times to stimulus configuration displayed variations that further provided evidence of how multiple early visual stages affect perception of simple stimuli.

A large‐scale neuronal network modelling study: Stimulus size modulates gamma oscillations in the primary visual cortex by long‐range connections

“…V1 neurons receive visual information from a specific range of the retina, the classical receptive field (CRF), via the lateral geniculate nucleus (LGN), and the collection of feedforward input within the CRF largely determines the neuron's firing pattern. As the size of the visual stimulus increases, the portion outside of the CRF can also affect and generally attenuates neuronal firing activity, known as 'surround suppression' (Huang et al, 2023;Nienborg et al, 2013;Orekhova et al, 2020;Wang et al, 2009). Biological experiments have demonstrated that gamma oscillations are significantly modulated by size, namely, the oscillatory power in each frequency band increases with the most pronounced changes in the low gamma range (30-80 Hz) as stimulus size is increased, and the peak frequency of gamma oscillation decreased monotonically with increasing stimulus size (Gieselmann & Thiele, 2008;Jia et al, 2011;Ray & Maunsell, 2011).…”

“…Numerous physiological experiments and modelling studies have answered this question using firing rates as an entry point. Experimental evidence suggests that size modulation effects may be contributed by feedforward connections, longrange horizontal connections within cortical areas and feedback connections between different areas of the cortex within the primary visual cortex at different spatiotemporal scales and stimulus properties (Angelucci et al, 2017;Huang et al, 2023;Nurminen et al, 2018;Ozeki et al, 2004;Sato et al, 2014). Modelling studies similarly emphasize the role of feedforward, feedback, lateral connections and other special circuits (Di Santo et al, 2022;Keller et al, 2020;Li & Young, 2021;Schwabe et al, 2006).…”