Neuroscience: A Medical Student's Guide

The largest of the lobes of the brain is the frontal lobe. It is inclusive of the cortex rostral to the central sulcus and dorsal to the cingulated sulcus. Included in this region of the brain is the precentral gyrus. This structure houses the tissue mass that is known as the primary motor cortex. Spatially, the premotor cortex is seen to lie just rostral to the precentral gyrus. Moving more rostral, the superior, middle and the inferior frontal gyri are found. The inferior frontal gyrus is able to be further subdivided into the pars triangularis, the pars opercularis, and the pars orbitalis. These structures are of prime importance with relation to functional properties, as the pars triangularis and the pars opercularis constitute Baroca’s area or the region of verbal expression. This is seen in and is indicative of the dominant hemisphere. These anatomic structures will be reviewed as a discussion of pathologic conditions is undertaken. The parietal lobe is inclusive of the cortex that extends from the cingulate gyrus to the anterior pole of the occipital lobe. The lateral sulcus is the defining border of the parietal and the temporal lobes. The postcentral gyrus is located on the posterior aspect of the central sulcus. Within this gyrus is found the somatosensory cortex. There is also a demarcation sulcus called the intraparietal sulcus that is the demarcation line between the subdivision of the parietal lobe into the superior and inferior parietal lobules. The inferior parietal lobule is important in the interpretation of the integrative information sent via the somatosensory, auditory and visual regions of the adjacent tissue. The temporal lobe is seen to lie within and occupy the entire middle cranial fossa. The exterior surface of the temporal lobe is subdivided into the superior, middle and inferior gyri. Anatomically, these gyri are found in a parallel orientation with the Sylvian Fissure. Within the confines of the superior aspect of the tissue, there is additional inclusive tissue that will form the auditory cortex. The duties of the primary auditory cortex are many. The primary auditory cortex is involved in the integration of the processed language center and language comprehension. Therefore, any compromise to this region of neural tissue will exhibit devastating deficit. Within the temporal lobe are the regions responsible for the processing of the visual information through the occipitotemporal and parahippocampal gyri. The primitive sense of olfaction is found to lie within a region of tissue called the uncus. The uncus is found to occupy the most medial aspect and the very tip of the parahippocampal gyrus.