Alpha, gamma and haemodynamic responses –how are they related? S Haigh1, N Cooper2, V Romei2, A Wilkins2 |
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1Department of Psychology, Carnegie Mellon University, PA, United States |
| We measured the oxyhaemoglobin response to grating patterns using near-infrared spectroscopy and simultaneously, the associated change in gamma and alpha power in the electroencephalogram. Of the 22 participants, 6 had migraine. We presented square-wave grating patterns (1) with bars alternating in colour, or (2) with achromatic bars that were static, drifted at a constant velocity towards central fixation, or had a vibrating motion with similar contour velocity. For the chromatic gratings, regardless of hue, those with large separation in the chromaticity of the bars evoked a relatively large oxyhaemoglobin response, greater alpha suppression, and a lower gamma power. For achromatic gratings, the moving patterns (drifting and vibrating) evoked a shorter oxyhaemoglobin response, and greater alpha suppression than the static pattern. The gamma response was inconsistent. Migraineurs, who generally have a hyper-responsive cortex, showed a larger-amplitude/shorter-duration oxyhaemoglobin response and greater alpha suppression to the same gratings, but did not show consistently different gamma responses. The association between oxyhaemoglobin response and alpha suppression may reflect the extent of cortical activation by a stimulus. The gamma response, however, is less consistent. |
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