Figure 3.

We propose a rostro-caudal abstraction gradient within the left inferior frontal gyrus in terms of two parallel but intertwined abstraction features, integrating the temporal abstraction gradient from figure 2 with an abstraction gradient of domain generality. The red lines in this figure correspond to BA 44 being subdivided into a ventral and dorsal part (44v and 44d) and BA 45 comprising an anterior and posterior part (45a and 45p), based on receptor architectonic parcellations [80]. These divisions can be used to describe a rostro-caudal gradient in more detail. In this model, 44d and 6v are engaged in phonological processing (light blue), which instantiates sequence rules at the word level; 44v and 45p are engaged in processing e.g. syntactic rules at the word and sentence processing level and perhaps also semantic rules at the sentence level; and 45a and BA 47 are engaged in the integration of these processes as well as information from other domains (such as gesture information) with the goal of extracting the meaning (light green) at longer time scales.