COMPUTERIZED INFRARED IMAGING-SYSTEM FOR STUDYING THERMAL-ACTIVATION ON THE SKULL FOLLOWING SOMATIC STIMULATION IN SMALL ANIMALS

A computerised infrared imaging system has been developed to measure i nfrared radiation as a means of functionally mapping the cerebral cort ex. In two species of small mammal, rat and gerbil, the authors locali sed the thermal changes at the skull overlying the somatic sensory cor tex following somatic stimulation of the mystacial vibrissae. Though t ypically small in magnitude, a thermal response could be detected thro ugh the skull. To enhance detection sensitivity, a number of measures were taken to improve various aspects of data acquisition, stimulus de livery and control of experimental conditions. Regarding data analysis , a coordinate system based on skull landmarks was adopted to localise thermally-active regions for comparison across animals of the same sp ecies. To extract the region of weak temperature changes, a coarse-to- fine detection strategy was developed, which searched automatically fo r clusters of temporally-and spatially-correlated pixels above a data- driven threshold. Thus, the dynamic aspect of the thermal changes at a ny region of interest on the skull could be-studied efficiently. The d etection algorithm was tested against simulated responses in addition to empirical data obtained from animals. All of the above software was integrated in a user-friendly package.