A voxel-based morphometry study of semantic dementia: Relationship betweentemporal lobe atrophy and semantic memory

The cortical anatomy of G patients with semantic dementia (the temporal lob e variant of frontotemporal dementia) was contrasted with that of a group o f age-matched normal subjects by using voxel-based morphometry, a technique that identifies changes in gray matter volume on a voxel-by-voxel basis. A mong the circumscribed regions of neuronal loss, the left temporal pole (Br odmann area 38) was the most significantly and consistently affected region . Cortical atrophy in the left hemisphere also involved the inferolateral t emporal lobe (Brodmann area 20/21) and fusiform gyrus. In addition, the rig ht temporal pole (Brodmann area 38), the ventromedial frontal cortex (Brodm ann area 11/32) bilaterally, and the amygdaloid complex were affected, but no significant atrophy was measured in the hippocampus, entorhinal, or caud al perirhinal cortex. The degree of semantic memory impairment across the G cases correlated significantly with the extent of atrophy of the left ante rior temporal lobe but not with atrophy in the adjacent ventromedial fronta l cortex. These results confirm that the anterior temporal lobe is critical ly involved in semantic processing, and dissociate its function from that o f the adjacent frontal region.