lunedì 2 maggio 2016

Language and the cortex or language in the cortex?

By Alberto Carrara, LC

Few days ago Alexander G. Huth, Wendy A. de Heer, Thomas L. Griffiths, Frédéric E. Theunissen and Jack L. Gallant, scientists at the University of California, Berkeley, published in Nature an interested article titled “Natural speech reveals the semantic maps that tile human cerebral cortex” (Nature. Published online April 27 2016) including a video.
What if a map of the brain could help us decode people’s inner thoughts?

These scientists have taken a step in that direction by building a “semantic atlas” that shows in vivid colors and multiple dimensions how the human brain organizes language (bottom-up) or how language shapes and structures the human cortex (top-down).
The atlas identifies brain areas that respond to words that have similar meanings. The findings are based on a brain imaging study that recorded neural activity while study volunteers listened to stories from the “Moth Radio Hour”. They show that at least one-third of the brain’s cerebral cortex, including areas dedicated to high-level cognition, is involved in language processing.

Notably, the study found that different people share similar language maps.

The study starts from two main premises. The first one deal with the intrinsic relationship between mental activity and brain activation/function: «The meaning of language is represented in regions of the cerebral cortex collectively known as the ‘semantic system’» (Abstract). “Representation” is a core concept in Mind Philosophy and needs a deeper explication.
The second premise deal with the real state-of-art in mental-brain-mapping analysis: «However, little of the semantic system has been mapped comprehensively, and the semantic selectivity of most regions is unknown» (Abstract).

«Here we systematically map semantic selectivity across the cortex using voxel-wise modelling of functional MRI (fMRI) data collected while subjects listened to hours of narrative stories. We show that the semantic system is organized into intricate patterns that seem to be consistent across individuals. We then use a novel generative model to create a detailed semantic atlas. Our results suggest that most areas within the semantic system represent information about specific semantic domains, or groups of related concepts, and our atlas shows which domains are represented in each area. This study demonstrates that data-driven methods—commonplace in studies of human neuroanatomy and functional connectivityprovide a powerful and efficient means for mapping functional representations in the brain» (Abstract).

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