Inferior frontal gyrus (Broca’s area)

Impairment in language and syntactic processing has been implicated in ALS patients [67–70]. Pathological changes in Broca’s area, associated with speech production and a wide range of language and communication related functions [71–73], have been reported in ALS with and without other FTD features [67]. Broca’s motor speech area and its homologue in the right hemisphere occupy the caudal part of the inferior frontal gyrus demarcated by the precentral sulcus posteriorly, inferior frontal sulcus superiorly and the lateral fissure inferiorly [65]. The area is further delineated macroscopically by the opercular and triangular gyri corresponding to BA 44 and 45 [71, 74]. Broca’s area was sampled from the inferior frontal gyrus, including the depth of the circular insular sulcus in two coronal slices (~ 2 cm) rostral to the precentral sulcus (Fig. 3).