Brain activation on fMRI and verbal memory ability: Functional neuroanatomic correlates of CVLT performance

We have recently reported (Saykin et al., 1999b) selective activation of le ft medial temporal lobe structures during processing of novel compared to f amiliar words using functional magnetic resonance imaging (fMRI). The curre nt study describes the relationship between a widely used clinical test of verbal learning, the California Verbal Learning Test (CVLT), and the previo usly reported fMRI activations. Thirteen right-handed healthy adult partici pants were studied with whole brain echo-planar fMRI while listening to nov el and recently learned (familiar) words intermixed pseudorandomly in an ev ent-related design. These participants were also tested with the CVLT Score s for CVLT Trial 1 (immediate encoding of novel words) and recognition disc riminability (recognition of familiar vs, novel words) were correlated with fMRI signal change during processing of novel versus familiar words using a covariance model implemented in SPM96. For the novel words analysis, voxe ls in the right anterior hippocampus correlated significantly with Trial 1 (r = .76 at the maxima). For the recognition analysis, a significant cluste r of voxels was found in the right dorsolateral prefrontal cortex (r = .88 at the maxima). Our prior results of separable left medial temporal activat ion to novel and familiar words, together with results of the covariance an alyses reported here, suggest that in addition to the left medial temporal lobe (MTL) regions that are engaged during novel and familiar word processi ng, the right hippocampus and right frontal lobe are also involved, particu larly in those participants with better memory ability. This positive relat ionship between fMRI activation and CVLT performance suggests a role for th ese right hemisphere regions in successful memory processing of verbal mate rial, perhaps reflecting more efficient encoding and retrieval strategies t hat facilitate memory.