Functional anatomic dissociation of description and picture naming in the left temporal lobe

Functional magnetic resonance imaging (fMRI) was used in a non-patient experimental sample to assess the neuroanatomical dissociation of picture and description naming (PN and DN) in temporal lobe (TL). The purpose was to determine the generalizability of findings in semantic organization in the epilepsy patient population to the broader population. It was hypothesized that, akin to patient derived findings, DN would uniquely activate left TL regions anterior to those associated with PN, while overlapping in middle and posterior left TL. Participants (n = 16) underwent fMRI while silently naming target words during a picture naming task (PNT; line drawings) and description naming task (DNT; orthographic phrases). Analysis was a priori restricted to the left TL. Group results of direct contrasts (DNT > PNT and PNT > DNT) confirmed the hypothesized dissociation with DNT > PNT activating anterior left TL. Within-condition contrasts (DNT and PNT alone) yielded additional support, revealing areas of shared and unique activation in each condition. This is the first imaging study to contrast DN and PN in the same sample. The results suggest DN and PN are meaningfully different constructs subserved by converging and diverging TL neuroanatomy and may be differentially affected by disease.