Temporal development of power spectra in response to a 400 μm-amplitude flutter stimulus. A: Light absorbance images obtained at selected times before and during flutter stimulation. B: Power spectra of OIS activity sampled in the anterior-posterior dimension across the activated cortical region. With increasing stimulus duration, the most prominent frequency band in the power spectra shifts to the left relative to the pre-stimulus condition. C: Temporal shift in relative power in the 6–9.5 cycles/mm band (top) and in the 1.5–3 cycles/mm band (bottom). As stimulus duration increases, the relative power decreases in the 6–9.5 cycles/mm band, but increases in the 1.5–3 cycles/mm band.