A new addition to the language network: the anterior temporal lobe.

Wernicke proposed a theoretical area for language comprehension in the 1800s, and we have been searching for it ever since. Studies of primary progressive aphasia (PPA) now suggest that the left anterior temporal lobe fulfills much of the functionality originally ascribed to Wernicke's area. I will review several metrics we have established to assess word knowledge in PPA, including those derived from event-related potentials, eye movements, and magnetic resonance imaging. Results link word knowledge to the anterior temporal lobe rather than other putative areas for Wernicke's area such as the temporoparietal junction. Degradation of word knowledge in PPA takes on the form of "taxonomic blurring", where words from the same category such as "dog" and "cat" can no longer be differentiated. Hemispheric differences in anterior temporal functionality are also described, being more important for word knowledge in the left hemisphere and object knowledge in the right hemisphere. [ABSTRACT FROM AUTHOR]