Se. Molchan et al., A FUNCTIONAL ANATOMICAL STUDY OF ASSOCIATIVE LEARNING IN HUMANS, Proceedings of the National Academy of Sciences of the United Statesof America, 91(17), 1994, pp. 8122-8126
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.