LATERALIZED CHANGES IN REGIONAL CEREBRAL BLOOD-FLOW DURING PERFORMANCE OF VERBAL AND FACIAL RECOGNITION TASKS - CORRELATIONS WITH PERFORMANCE AND EFFORT

Functional neuroimaging has been used to investigate neural substrates of mnemonic processes, and cerebral blood flow (CBF) measures have be en sensitive to activation with memory tasks. Studies of memory with t wo-dimensional (133)Xenon clearance techniques found that word and fac e recognition tasks produced contralateral CBF changes in mid-temporal cortical regions. This study replicated the activation paradigm, expa nding to the three-dimensional resolution of positron emission tomogra phy (PET). Word and face recognition, and a control baseline task were administered to 19 healthy right-handed volunteers (11 men, 8 women) during successive 10 min PET O-15-water measures of CBF. Quantitative CBF rates were calculated with the arterial input function and the equ ilibrium model. Redistributions of blood flow were compared across tas ks using both absolute and relative (region/ whole brain) CBF. Replica ting the '''Xenon clearance findings, CBF was ''appropriately'' latera lized during task performance (left-right for words > left-right for f aces) in the midtemporal region. Contrary to predictions, the recognit ion tasks did not activate expected mesolimbic or prefrontal areas. Th e task-induced CBF changes also correlated with performance. Bilateral CBF in mid-temporal and parahippocampal gyrus regions ofinterest corr elated with the ability to correctly identify word targets (sensitivit y). Left-lateralized CBF in the amygdala and hippocampus correlated wi th better word sensitivity as well as specificity (ability to correctl y reject foils). Complementally, right-lateralized CBF in the parahipp ocampal gyrus correlated face memory tasks, respectively. Thus, wherea s this recognition task showed the expected lateralized increase in th e mid-temporal region and not in frontal and limbic areas, lateralized activation in some of these areas was associated with better performa nce. In addition, left-lateralized CBF in the amygdala and right-later alized CBF in the parahippocampal gyrus and hippocampus correlated wit h ''mental effort'' indices (task performance relative to basal abilit y) for word and face memory tasks, respectively. Thus, whereas this re cognition task showed the expected lateralized increase in the mid-tem poral region and not in frontal and limbic areas, lateralized activati on in some of these areas was associated with better performance. Expl oratory analyses on other regions showed lateralized changes in one ad ditional temporal region, the occipital-temporal, and several limbic r egions. (C) 1997 Academic Press.