A FUNCTIONAL ANATOMICAL STUDY OF ASSOCIATIVE LEARNING IN HUMANS

The purpose of the study was to map the functional neuroanatomy of sim ple associative learning in humans. Eyeblink conditioning was studied in eight normal volunteers using positron emission tomography and (H2O )-O-15. Regional cerebral blood flow was assessed during three sequent ial phases: (i) explicitly unpaired presentations of the unconditioned stimulus (air puff to the right eye) and conditioned stimulus (binaur al tone), (ii) paired presentations of the two stimuli (associative te aming), and (iii) presentation of the conditioned stimulus alone. Duri ng associative learning, relative to the unpaired phase, blood now was significantly increased in primary auditory and left posterior cingul ate cortices and significantly decreased in areas of the right cerebel lar, right prefrontal, right parietal, and insular cortices and right neostriatum. The lateralization of the changes may relate to the funct ional organization of memory and learning processes in the brain. The activation in primary auditory cortex is an example, using a neuroimag ing technique, of a learning-related change in primary sensory cortex in humans. The changes in areas such as the cerebellum, prefrontal cor tex, and neostriatum provide support for their roles in associative le arning as proposed by animal models. Moreover, these findings show tha t in humans, even simple classical conditioning involves distributed c hanges in multiple neural systems.