Morphology And Asymmetry Of The Anterior Ascending Ramus And The Horizontal Ascending Ramus Of The Lateral Sulcus

The anterior ascending ramus of the lateral sulcus(aals)and the horizontal ascending ramus of the lateral sulcus(hals)are two defining sulci of the posterior ventrolateral frontal cortex of the human brain.The aals and the hals extend dorsally the inferior gyrus from the lateral sulcus,form the morphological boundary of the pars opercularis(PO)and the pars triangularis(PTR).Broca’s area is located in the inferior frontal gyrus above the lateral sulcus.In addition to participating in speech production,Broca’s area is also involved in sensorimotor learning and integration of language understanding.Damage to the Broca’s area leads to aphasia,often referred to as Broca aphasia.The clinical symptoms of Broca aphasia are speech fluency and grammatical or prosodic errors in speech.Both electrical stimulation of the area and functional imaging studies have demonstrated the specific role of the Broca’s area in languageA large number of brain structure studies using magnetic resonance imaging mostly focus on the cortical thickness and surface area of Broca’s area,and relatively few studies on the characteristics of the cortical sulcus,especially using the data of Chinese people.The morphometry of these two sulci maybe have potential effects on the various functions of Broca’s area.In addition,significant hemispheric and sex differences have been observed in the studies of Broca’s area.However,there are few studies on the morphological changes and the hemispheric and sex differences of the morphological parameters between of these two sulci adjacent to Broca’s area.To explore the morphology variation,hemispheric and sex difference of these two sulci,so as to enable better understanding of their patterns and the functions of the Broca’s area.BrainVISA was used to reconstruct and parameterize these two sulci with 3D MR images of 90 healthy right-handed subjects.The 3D anatomic morphology of these two sulci was presented using 4 sulcal parameters,including average depth(AD),average width(AW),top length(TL)and bottom length(BL).The aals could be identified in 98.89%of the hemispheres,while the hals could be identified in 98.33%.The morphological patterns of these two sulci were categorized into four main types and other atypical types.There were no statistically significant interhemispheric and sex differences in the frequency of the morphological patterns.There was statistically significant interhemispheric difference in BL of the aals and AW of the hals.Significant gender differences were found in the bilateral AD of the aals and the BL and TL of the hals in right hemisphere.Our results will not only provide structural basis for the functional studies that related to Broca’s area,but also be helpful for the precise positioning of Broca’s area in neurosurgery.