LATERALIZATION AND BEHAVIORAL CORRELATION OF CHANGES IN REGIONAL CEREBRAL BLOOD-FLOW WITH CLASSICAL-CONDITIONING OF THE HUMAN EYEBLINK RESPONSE

Laterality of changes in regional cerebral blood flow (rCBF) during cl assical conditioning of the human eyeblink response was studied and ch anges in rCBF were correlated with conditioned responses. In 10 normal volunteers, rCBF was mapped with positron emission tomography and (H2 O)-O-15 during pairings of a binaural tone conditioned stimulus and an air puff unconditioned stimulus to the left eye. Control conditions c onsisted of explicitly unpaired presentations of the tone and air puff before (control) and after (extinction) pairings. During pairings, rC BF increased significantly in right primary auditory cortex (contralat eral to air puff) and decreased significantly in left and right cerebe llar cortex. There were also increases in rCBF in right auditory assoc iation cortex and left temporoccipital cortex. Decreases in rCBF were noted bilaterally in the temporal poles and in the left prefrontal cor tex. Positive correlations between changes in rCBF and percent conditi oned responses were located in middle cerebellum, right superior tempo ral cortex, left dorsal premotor cortex, right middle cingulate, and r ight superior temporal cortex. There were negative correlations in lef t inferior prefrontal cortex, left middle prefrontal cortex, and right inferior parietal cortex. The data replicate our previous findings of lateralized changes in rCBF following presentations of a binaural ton e and air puff to the right eye and indicate that there are pairing-sp ecific changes in primary auditory cortex and cerebellum that are not unique to the left or right hemisphere but are a function of the side of training. The commonalities as well as differences in regional invo lvement in our present and previous experiment as well as in other eye blink studies illustrate the advantage of functional neuroimaging to q uantify different strategies used by the brain to perform seemingly si milar functions. Indeed, the data support the notion that learning-rel ated changes can be detected in a number of specific, but not necessar ily invariant, brain regions, and that the involvement of any one regi on is dependent on the characteristics of the particular learning situ ation.