STATISTICAL-METHODS IN FUNCTIONAL MAGNETIC-RESONANCE-IMAGING WITH RESPECT TO NONSTATIONARY TIME-SERIES - AUDITORY-CORTEX ACTIVITY

In awake animal and human auditory cortices, it is a common experience with electrophysiological and suitable imaging methods for responses to steady stimulation to be strongly state-dependent and to exhibit no nstationarities, even over short periods of observation, If such nonst ationary behavior is also reflected by hemodynamic responses in the hu man auditory cortex, conventional methods of analysis of fMRI data, al though applicable for instance to largely stationary responses in visu al and other cortices, may be misleading in attempts to parcellate aud itory cortex into fields and to demonstrate functional maps, Time-Wind ows, described in this article as a convenient tool for the detection and analysis of time-variant brain activities, solves some of these pr oblems. Time-Windows demonstrates that activity is evoked reliably in three separate territories of human auditory cortex, parts of which ma y show nonstationary behavior, depending on the auditory stimuli and t asks.