BRAIN ACTIVATION DURING WORD IDENTIFICATION AND WORD RECOGNITION

Previous memory research has suggested that the effects of prior study observed in priming tasks are functionally, and neurobiologically, di stinct phenomena from the kind of memory expressed in conventional (ex plicit) memory tests. Evidence for this position comes from observed d issociations between memory scores obtained with the two kinds of task s. However, there is continuing controversy about the meaning of these dissociations. In recent studies, Ostergaard (1998a, Memory Cognit. 2 6:40-60; 1998b, J. Int. Neuropsychol. Sec., in press) showed that simp ly degrading visual word stimuli can dramatically alter the degree to which word priming shows a dissociation from word recognition; i.e., e ffects of a number of factors on priming paralleled their effects on r ecognition memory tests when the words were degraded at test. In the p resent study, cerebral blood flow changes were measured while subjects performed the word identification treading) and recognition memory ta sks used previously by Ostergaard. The results are the direct comparis ons of the two tasks and the effects of stimulus degradation on blood flow patterns during the tasks. Clear differences between word identif ication and word recognition were observed: the latter task evoked con siderably more prefrontal activity and stronger cerebellar activation. Stimulus degradation was associated with focal increases in bilateral fusiform regions within the occipital lobe. No task, degradation, or item repetition effects were demonstrated in mesial temporal regions, no repetition effects were observed in any region, and there was no ev idence for different effects of stimulus degradation in the priming an d recognition memory conditions. Power limitations may have contribute d to the null effects. (C) 1998 Academic Press.