Functional Anatomy of Spatial Mental Imagery Generated from Verbal Instructions

TLDR

Positron emission tomography measured regional cerebral blood flow while subjects mentally constructed 3‑D cube assemblies from auditory instructions, contrasting this spatial imagery task with passive listening and silent rest, all performed in darkness. The spatial imagery task activated a bilateral occipitoparietal‑frontal network—including superior occipital, inferior parietal, and premotor cortices—and the right inferior temporal cortex, with no primary visual area activation, while bilateral superior and middle temporal cortices were engaged in both imagery and listening versus rest, demonstrating that the dorsal visuospatial route can be recruited by auditory verbal stimuli and that some imagery tasks bypass early visual areas.

Abstract

Positron emission tomography (PET) was used to monitor regional cerebral blood flow variations while subjects were constructing mental images of objects made of three-dimensional cube assemblies from auditorily presented instructions. This spatial mental imagery task was contrasted with both passive listening (LIST) of phonetically matched nonspatial word lists and a silent rest (REST) condition. All three tasks were performed in total darkness. Mental construction (CONS) specifically activated a bilateral occipitoparietal-frontal network, including the superior occipital cortex, the inferior parietal cortex, and the premotor cortex. The right inferior temporal cortex also was activated specifically during this condition, and no activation of the primary visual areas was observed. Bilateral superior and middle temporal cortex activations were common to CONS and LIST tasks when both were compared with the REST condition. These results provide evidence that the so-called dorsal route known to process visuospatial features can be recruited by auditory verbal stimuli. They also confirm previous reports indicating that some mental imagery tasks may not involve any significant participation of early visual areas.