TY - JOUR
T1 - Induced and evoked neural correlates of orientation selectivity in human visual cortex
AU - Koelewijn, Loes
AU - Dumont, Julie R.
AU - Muthukumaraswamy, Suresh D.
AU - Rich, Anina N.
AU - Singh, Krish D.
PY - 2011/2/14
Y1 - 2011/2/14
N2 - 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.
AB - 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.
KW - orientation
KW - magnetoencephalography
KW - primary visual cortex
KW - gamma oscillations
KW - event-related fields
KW - oblique effect
UR - http://www.scopus.com/inward/record.url?scp=78650950964&partnerID=8YFLogxK
U2 - 10.1016/j.neuroimage.2010.11.045
DO - 10.1016/j.neuroimage.2010.11.045
M3 - Article
C2 - 21112405
AN - SCOPUS:78650950964
SN - 1053-8119
VL - 54
SP - 2983
EP - 2993
JO - NeuroImage
JF - NeuroImage
IS - 4
ER -