Local haemodynamic changes associated with neural activity in auditory cortex

We used an optical technique to study haemodynamic changes associated with acoustically driven activity in auditory cortex of the chinchilla. Such cha nges are first delectable c. 0.5 s after stimulation, peak at 2-3 s, and de cay within a Further 3-6 s. This intrinsic signal imaging reveals activity in separate cortical areas, including primary auditory cortex (AI), seconda ry auditory cortex (AII) and an anterior auditory field (AAF). We have meas ured the timing of haemodynamics associated with each area, and find that A I has a different time course from AII and AAF; its haemodynamic change rec overs more rapidly. We also show that within AI and AII, place specific act ivity related to acoustic stimulus frequency can be resolved by this optica l imaging method. Our results show the close association between blood flow change and the local metabolic demands of neural activity. The data provid e information about the potential of other functional imaging methods (e.g. PET, fMRI) which rely on activity related haemodynamic events.