Organization of the experimental paradigm for IOS. Chronicle and acute experiments. Available areas of the brain: visual and auditory cortex, olfactory bulbs, somatosensory cortex, cerebellum. Presentations of the sensory stimuli, the trial, averaging of trials.

Stimuli (acoustic, visual, etc) usually generated digitally and presented via earphones, monitor, or etc. The animal is firmly fixed by the headholder on a vibroisolated table. Intrinsic signals were measured to visualize functional maps of the investigated area using standard techniques; The cortex was illuminated with monochromatic light of 540-nm, 650-nm or another wavelength, un depends of the experimental conditions using one or two fiber-optical light guides to achieve uniform illumination of the cortical surface as much as possible. The focal plane was adjusted at 100 - 500 nm below the cortical surface using a tandem-lens microscope arrangement. Images were obtained using a CCD camera and digitized using a differential video-enhancement system. Video images of the investigated area acquired in few (10 – 1000 or more) frames; the duration of each frame is vary from 1 ms to 1 s. Acquisition of intrinsic signals must be synchronized with acoustic stimulus presentation so that the stimulus onset was delayed by several frames in each recording. The data acquisition period was followed by a silent interval of few tens – few thousands. In the data analysis, usually first of all, we can subtracted the average signals over the first three frames preceding the stimulus onset from the recorded signals at each frame to extract stimulus-related intrinsic signals. This procedure was applied to the recorded signals at each trial. Next, we can reconstruct intrinsic signals elicited in response to each stimulus using the generalized indicator function method, which can project the optical imaging data onto a subspace of high signal-to-noise ratios (Yokoo et al., 2001).

Experimental paradigm in case of intrinsic optical imaging of the cat auditory cortex. A. Stimulus consists of 5 shot peeps, 20 frames per trial. First three frames were used for baseline. B. Region of interesting *auditory cortex) C. One sound peep and example of the electrophysiological response