FIGURE 2.

Hypothetical pathways of speech perception: the phonological network – including secondary areas of left- hemisphere auditory cortex in superior temporal gyrus and sulcus (STG/STS) and frontal speech generation mechanisms – is colored in green, including additionally left fusiform gyrus (FG) in blind subjects. This network seems to be linked to a right-dominant syllable-prosodic network via subcortical structures and supplementary motor area (SMA). In normal subjects, this prosodic network is mainly localized in the right-hemisphere auditory system (brown arrows). In order to overcome temporal constraints regarding this prosodic stream as an independent signal (independent from segmental processing and from pitch processing), blind subjects seem to be able to recruit part of their visual cortex – presumably via subcortical afferent auditory information (red arrows) – to represent this prosodic information and to transfer it as an event-trigger channel to the frontal part of the speech processing network. Arrows to and from left FG were omitted in order to avoid an overload of the model and since the major aspect addressed here is the interplay between the right-dominant prosodic and the left-dominant phonological network. Furthermore, direct pathways between visual and auditory cortex were also omitted since the “bottleneck” for understanding ultra-fast speech seems to be located in the interface between sensory processing and frontal speech generation mechanisms.