Structural connectivity among language areas

Leaving the cortical microstructure behind (at least temporarily), this week’s focus will be on the macro level, i.e. language related brain areas and interconnections among them. I’d like to start with the hardware (citoarchitectural area and structural connectivity level) and build up. Language related brain areas (this itself is a dubious labeling, since the areas mentioned may subserve non-linguistic functions – but I move on), focusing on the temporal and prefrontal cortices.

The temporal cortex here includes areas 41, 42, 21, and 20. The frontal cortex includes 45, 44, (prefrontal) and 6 (premotor). There are structural connections between anterior 22 (anterior) and 45 through Extreme Fiber Capsule System, and between anterior 22 and occluded part of the inferior frontal cortex (Frontal Operculum) through unicite fasciculus (Friederici 2011). Posteriorly there are structural connections between posterior 22 and 44, and between posterior 22 and 6 both served by Arcuate Fascile and Superior Longitudinal Facile III (Friederici 2011). Friederici 2011 focuses on peri-Sylvian cortex, but extending the scope a little to include so called lexical areas (21) and a sensory/motor hub (40) (Hickock and Poppel 2011), I get my Figure 1.

The auditory input flows from 41, 42, and from there flows both anteriorly through and posteriorly through area 22 and 21. The motor intention / control flow is from 45, 44, and to  6, where 6 connects to the motor output area. Fiber tracking in primate brain suggests that the ventral pathway runs from the temporal to prefrontal lobe, whereas the ventral pathway is considered bidirectional (Rauschcker 2011). From here I’d like to characterize processing taking place at each area, but it’s been long enough, so to be continued …

Friederici AD. The brain basis of language processing: from structure to function. Physiological reviews. 2011 Oct 1;91(4):1357-92.

Hickok G, Poeppel D. The cortical organization of speech processing. Nature Reviews Neuroscience. 2007 May 1;8(5):393-402.

Kelly C, Uddin LQ, Shehzad Z, Margulies DS, Castellanos FX, Milham MP, Petrides M. Broca’s region: linking human brain functional connectivity data and non‐human primate tracing anatomy studies. European Journal of Neuroscience. 2010 Aug 1;32(3):383-98.

Rauschecker JP. An expanded role for the dorsal auditory pathway in sensorimotor control and integration. Hearing research. 2011 Jan 31;271(1):16-25.