Friday, December 14, 2012

Lateralization of word and face processing

A few weeks ago I was at the annual meeting of the Psychonomic Society where, among other interesting talks, I heard a great one by Marlene Behrmann about her recent work showing that lateralization of visual word recognition drives lateralization of face recognition. Lateralization of word and face processing are among the most classic findings in cognitive neuroscience: in adults, regions in the inferior temporal lobe in the left hemisphere appear to be specialized for recognizing visual (i.e., printed) words and the same regions in the right hemisphere appear to be specialized for recognizing faces. Marlene and her collaborators (David Plaut, Eva Dundas, Adrian Nestor, and others) have shown that these specializations are linked and that the left hemisphere specialization for words seems to drive the right hemisphere specialization for faces. It's a nice combination of: 
  1. Behavioral experiments showing that lateralization for words develops before lateralization for faces, and that reading ability predicts degree of lateralization for faces (Dundas, Plaut, & Behrmann, 2012).
  2. ERP evidence also showing earlier development of lateralization for words than for faces.
  3. Computational modeling showing how this specialization could emerge without pre-defined modules (Plaut & Behrmann, 2011).
  4. Functional imaging evidence that the lateralization is relative: the right fusiform gyrus is more involved in face processing, but the left is involved also (Nestor, Plaut, & Behrmann, 2011).
It's a beautiful example of how different methods can come together to provide a more complete picture of cognitive and neural function.

Less than one week after I posted this, there is a new paper by Behrmann and Plaut (in press, Cerebral Cortex, doi:10.1093/cercor/bhs390) reporting further evidence, this time from cognitive neuropsychology, that lateralization of face and word processing is relative. They tested a group of individuals with left hemisphere damage and deficits in word recognition ("pure alexia") and a group of individuals with right hemisphere damage and deficits in face recognition ("prosopagnosia"). The individuals with pure alexia exhibited mild but reliable face recognition deficits and the individuals with prosopagnosia exhibited mild but reliable word recognition deficits.

ResearchBlogging.orgDundas EM, Plaut DC, & Behrmann M (2012). The Joint Development of Hemispheric Lateralization for Words and Faces. Journal of Experimental Psychology: General. PMID: 22866684. DOI: 10.1037/a0029503.

Nestor A, Plaut DC, & Behrmann M (2011). Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis. Proceedings of the National Academy of Sciences, 108(24), 9998-10003 PMID: 21628569

Plaut DC, & Behrmann M (2011). Complementary neural representations for faces and words: a computational exploration. Cognitive Neuropsychology, 28(3-4), 251-275 PMID: 22185237

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