Effects of memory processing on regional brain activation: cerebral blood flow in normal subjects

The role of the temporal lobe in memory has been implicated in lesion studies, which have also suggested the hypothesis of greater left hemispheric involvement in verbal, and right hemispheric involvement in facial memory. We tested these hypotheses in a sample of 27 normal right-handed subjects using the 133Xenon clearance method for measuring cerebral blood flow (CBF). The CBF was measured during resting baseline, word recognition, and face recognition conditions in counterbalanced order. CBF increased during recognition compared to baseline, and for the midtemporal lobe this increase was asymmetric to the left hemisphere for words and to the right for faces. While overall CBF levels and task related increases in CBF were uncorrelated either with performance or with delta performance (excess performance relative to basal memory abilities), laterality of task-related CBF correlated with both performance indices, showing regional specificity of correlations. This neurobehavioral probe paradigm can be applied in the study of neural substrates of normal and disturbed memory.