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. 2017 Feb;40(2):72–82. doi: 10.1016/j.tins.2016.11.004

Figure 2.

Figure 2

Evolutionarily Conserved Brain Areas for Processing Adjacent Sequence Relationships in Human and Monkey Frontal Cortex. Humans and rhesus macaques were first exposed to exemplary sequences from an artificial grammar that generates variable sequences, based on several adjacent relationships[9] (bottom right of Figure 1, main text). The participants were then presented with ‘consistent’ and ‘violation’ testing sequences during fMRI scanning. Group results from 12 human participants are displayed alongside representative results in an individual macaque, from the three that were studied (for details, see [9]). The results showed voxels in the brain that responded more strongly to violation sequences than to consistent sequences, shown here on rendered lateral surface representations of the human and monkey brain. The effects are illustrated for the right hemisphere, but are not significantly lateralized [9]. A key result was the strong engagement of ventral frontal and opercular cortex (vFOC) in both monkeys and humans, including the frontal operculum and anterior insula. These findings highlight the role of these regions in processing adjacent sequencing relationships. Areas 44 and 45 were not strongly engaged in either species, although the effect was statistically more pronounced in monkeys than in humans. These general impressions are supported by independent neuroimaging evidence in monkeys and humans (see the section Sequence Processing in the Primate Brain: Testing Neuroevolutionary Hypotheses’ in the main text). Parietal activation was observed in both species, including area 39 in humans and area 7 in macaques. These regions form part of the dorsal processing pathway and, in humans, are involved in a range of language tasks, including sentence comprehension 14, 81, 82, 83, but are not thought to form part of the core perisylvian circuit for hierarchical syntax [84]. Involvement of parietal regions is less evident than the involvement of frontal cortex during sequence processing in humans (e.g., 39, 61) and is not consistently observed in monkeys 9, 10.