Semantic categorization in the human brain: spatiotemporal dynamics revealed by magnetoencephalography.
We examined the cortical representation of semantic categorization using magnetic source imaging in a task that revealed both dissociations among superordinate categories and associations among different base-level concepts within these categories. Around 200 ms after stimulus onset, the spatiotemporal correlation of brain activity elicited by base-level concepts was greater within than across superordinate categories in the right temporal lobe. Unsupervised clustering of data showed similar categorization between 210 and 450 ms mainly in the left hemisphere. This pattern suggests that well-defined semantic categories are represented in spatially distinct, macroscopically separable neural networks, independent of physical stimulus properties. In contrast, a broader, task-required categorization (natural/man-made) was not evident in our data. The perceptual dynamics of the categorization process is initially evident in the extrastriate areas of the right hemisphere; this activation is followed by higher-level activity along the ventral processing stream, implicating primarily the left temporal lobe.
Löw
Andreas
A
University of Konstanz, Konstanz, Germany. loew@ufl.edu
Bentin
Shlomo
S
Rockstroh
Brigitte
B
Silberman
Yaron
Y
Gomolla
Annette
A
Cohen
Rudolf
R
Elbert
Thomas
T
D000328:Adult; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D016000:Cluster Analysis; D003210:Concept Formation / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011601:Psychophysics; D011930:Reaction Time / Q000502:physiology; D012660:Semantics