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Induced and evoked neural correlates of orientation selectivity in human visual cortex

Koelewijn, Loes, Dumont, Julie R., Muthukumaraswamy, Suresh Daniel, Rich, Anina N. and Singh, Krish Devi 2011. Induced and evoked neural correlates of orientation selectivity in human visual cortex. NeuroImage 54 (4) , pp. 2983-2993. 10.1016/j.neuroimage.2010.11.045

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Orientation discrimination is much better for patterns oriented along the horizontal or vertical (cardinal) axes than for patterns oriented obliquely, but the neural basis for this is not known. Previous animal neurophysiology and human neuroimaging studies have demonstrated only a moderate bias for cardinal versus oblique orientations, with fMRI showing a larger response to cardinals in primary visual cortex (V1) and EEG demonstrating both increased magnitudes and reduced latencies of transient evoked responses. Here, using MEG, we localised and characterised induced gamma and transient evoked responses to stationary circular grating patches of three orientations (0, 45, and 90° from vertical). Surprisingly, we found that the sustained gamma response was larger for oblique, compared to cardinal, stimuli. This “inverse oblique effect” was also observed in the earliest (80 ms) evoked response, whereas later responses (120 ms) showed a trend towards the reverse, “classic”, oblique response. Source localisation demonstrated that the sustained gamma and early evoked responses were localised to medial visual cortex, whilst the later evoked responses came from both this early visual area and a source in a more inferolateral extrastriate region. These results suggest that (1) the early evoked and sustained gamma responses manifest the initial tuning of V1 neurons, with the stronger response to oblique stimuli possibly reflecting increased tuning widths for these orientations, and (2) the classic behavioural oblique effect is mediated by an extrastriate cortical area and may also implicate feedback from extrastriate to primary visual cortex.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Cardiff University Brain Research Imaging Centre (CUBRIC)
Neuroscience and Mental Health Research Institute (NMHRI)
Subjects: R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Uncontrolled Keywords: Orientation; Magnetoencephalography; Primary visual cortex; Gamma oscillations; Event-related fields; Oblique effect
Publisher: Elsevier
ISSN: 1053-8119
Last Modified: 31 Jan 2020 03:49

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