those portions of the lateral sulcus extending into, and dividing, the inferior frontal gyrus into its parts. The anterior ascending ramus of the lateral sulcus is located in between the pars opercularis and the pars triangularis, whereas the anterior horizontal ramus of the lateral sulcus is located in between the pars triangularis and the pars orbitalis. SYN: ramus anterior sulci lateralis cerebri [TA].