Objective: To investigate the neural correlates of verbal and nonverbal semantic processing in neurodegenerative disease.
Background: Semantic memory is often impaired in neurodegenerative disease. Neuropsychologic and functional neuroimaging studies suggest that the semantic processing of verbal and nonverbal stimuli may depend on partially distinct brain networks.
Methods: We examined this possibility using voxel-based morphometry to correlate performance on verbal and nonverbal versions of a semantic association task with regional gray matter atrophy in 144 individuals with a variety of neurodegenerative diseases.
Results: Results showed that, regardless of stimulus type, semantic processing correlated with atrophy in both temporal lobes. In addition, material-specific correlations were found in left temporal regions for verbal stimuli and the right fusiform gyrus for nonverbal stimuli.
Conclusions: These results provide evidence for a differential role of the left and right hemispheres in the extraction of semantic information from verbal and pictorial representations. Areas in right inferior temporal lobe may be necessary to access structural descriptions of visually presented objects.
*Division of Clinical Neurosciences, University of Edinburgh, Scotland, UK
†Memory and Aging Center, UCSF Department of Neurology, San Francisco, CA
‡Centre de Recherche, Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada
Supported by the National Institute of Neurological Diseases and Stroke (R01 NS50915), the National Institute on Aging (P01 AG019724 and P50 AG-03-006), and the California Department of Health Services (DHS 04-35516).
Reprints: Maria-Luisa Gorno-Tempini, MD, PhD, Memory and Aging Center, UCSF Department of Neurology, San Francisco, CA (e-mail: email@example.com).
Received for publication July 2, 2008; accepted November 23, 2008