ILABS Brain Seminar

October 29 - Jason Yeatman Hierarchical coding of letter strings in the ventral stream: dissecting the inner organization of the visual word-form system. Vinckier F1, Dehaene S, Jobert A, Dubus JP, Sigman M, Cohen L. Neuron. 2007 Jul 5;55(1):143-56.

Abstract Visual word recognition has been proposed to rely on a hierarchy of increasingly complex neuronal detectors, from individual letters to bigrams and morphemes. We used fMRI to test whether such a hierarchy is present in the left occipitotemporal cortex, at the site of the visual word-form area, and with an anterior-to-posterior progression. We exposed adult readers to (1) false-font strings; (2) strings of infrequent letters; (3) strings of frequent letters but rare bigrams; (4) strings with frequent bigrams but rare quadrigrams; (5) strings with frequent quadrigrams; (6) real words. A gradient of selectivity was observed through the entire span of the occipitotemporal cortex, with activation becoming more selective for higher-level stimuli toward the anterior fusiform region. A similar gradient was also seen in left inferior frontoinsular cortex. Those gradients were asymmetrical in favor of the left hemisphere. We conclude that the left occipitotemporal visual word-form area, far from being a homogeneous structure, presents a high degree of functional and spatial hierarchical organization which must result from a tuning process during reading acquisition.

A good related paper for background: Binder, Jeffrey R., et al. "Tuning of the human left fusiform gyrus to sublexical orthographic structure." Neuroimage 33.2 (2006): 739-748.

November 5 - No Brain Seminar

November 12 - Open

November 19 - Open

November 26 - Thanksgiving

December 3 - Mark Wronkiewicz Something cool with decoding and single trial MEG analysis