The neural bases of attentive reading.

Recent studies have suggested that attention facilitates the formation of synchronous neural assemblies in the gamma range (>40 Hz) to amplify behaviorally relevant signals. Whether this mechanism is general or confined to sensory cortices is still a matter of debate, since there is little evidence of a direct link between attention and increased gamma synchronization in high-level brain regions. We recorded the intracerebral EEG of 10 epileptic patients while manipulating their attention during reading, and compared the neural responses to attended and unattended words. Visual presentation of attended words induced gamma band responses in the major brain regions associated with reading and those responses were attenuated for unattended words. The attenuation was not uniform within the reading network but followed a gradient from the posterior visual to the frontal areas. Altogether, these results support the view that the gamma band response can be used as a quantitative marker of attention.