✔️Precentral gyrus contains the primary motor cortex
✔️Premotor cortex lies immediately anterior to Primary motor cortex ( Brodmann’s area 6 on the lateral surface of the frontal lobe.)
✔️Premotor cortex is active in response to EXTERNAL visual or somatic sensory cues (e.g. reaching for an object in full view, or identifying an object by touch alone). Also has role in bilateral postural fixation (e.g. stabilization of the hips during walking).
✔️The supplementary motor area occupies a neighbouring part of Brodmann’s area 6 on the medial surface of the frontal lobe.
✔️The supplementary motor area seems to respond to INTERNAL cues, especially intentions to make voluntary movements (even if the movement is not carried out).
✔️Lesions of the supplementary motor cortex are associated with contralateral inability to initiate movements (akinesia).
✔️The inferior frontal gyrus of the dominant hemisphere (usually the left) contains the (Broca’s) motor speech area (Brodmann’s areas 44 and 45)
✔️The somatic sensory cortex, occupies the entire postcentral gyrus (Brodmann’s areas 3, 1 and 2, rostral to caudal).
✔️ Caudal to the somatosensory cortex is the sensory association cortex, which is divided into a superior and an inferior parietal lobule by an intraparietal sulcus.
✔️ The superior lobule is thought to be responsible for conscious awareness of the contralateral half of the body. Lesions of this part of the cortex may result in neglect of the contralateral side of the body.
✔️ The inferior lobule in the dominant (usually left) hemisphere is associated with language functions.
✔️ The cortex adjacent to the parieto-occipital sulcus and the calcarine sulcus, which lies on the medial surface of occipital lobe, constitutes the primary visual cortex (Brodmann’s area 17).
✔️ The superior surface of the temporal lobe contains the primary auditory cortex (Brodmann’s areas 41 and 42), responsible for the conscious perception of sound. Unilateral lesions of the primary auditory cortex will therefore cause partial deafness in both ears.
✔️ The auditory association cortex, known as Wernicke’s area corresponds to Brodmann’s area 22 in the dominant hemisphere. It allows for understanding of the spoken word, and connects with other language areas of the brain.
✔️ The temporal lobe curls inward to form the hippocampus which lies in the floor of the inferior horn of the lateral ventricle, and forms part of the limbic system. Its functions relate to short-term memory and the emotional aspects of behaviour.
✔️ Lying close to the anterior end of the hippocampus is the amygdala. Its a mass of subcortical grey matter that also forms part of the limbic system. It is associated with the conscious appreciation of smells.
✔️ The insula is one of the cortical centres for pain, and is also involved in involuntary activities such as the control of viscera by the autonomic nervous system.
✔️ The basal ganglia includes
• striatum (caudate nucleus, putamen of the lentiform nucleus and the nucleus accumbens)
• pallidum (globus pallidus of the lentiform nucleus)
• subthalamic nucleus
• compact part of the substantia nigra
✔️ Four basic circuits are known to occur from the cerebral cortex, through the basal ganglia and back to the cortex, by a direct or indirect route:
-a motor loop is concerned with learned movements;
-a cognitive loop with motor intentions;
-a limbic loop with emotional aspects of movement and
-an oculomotor loop with voluntary saccades.
✔️ Limbic system is composed of the the parahippocampal and cingulate gyri, the septal area, the hippocampal formation and the amygdala. Declarative memory (i.e. of new facts and events) may occur as modifications of synapses within the hippocampus.
✔️ Diencephalon comprises, from superior to inferior, the epithalamus, thalamus, subthalamus and hypothalamus.
✔️ The thalamus is the largest component of the diencephalon and is composed of numerous nuclei.
✔️ The epithalamus consists principally of the pineal gland that secretes melatonin and is involved with circadian rhythm and regulation of the onset of puberty and the habenular nuclei.
✔️ The subthalamus contains the subthalamic nucleus which connects to the globus pallidus and substantia nigra and is involved with the control of movement.
✔️ The hypothalamus has important connections with the limbic system, a controlling influence on autonomic nervous system activity and a role in neuroendocrine function.
✔️ The cerebellum coordinates movement by maintenance of equilibrium, posture and muscle tone at an unconscious level. Also concerned with muscular coordination, including trajectory, speed and force of movements.
✔️ The tectum (roof) of the midbrain is formed by four colliculi –the paired superior colliculi are associated with the visual system, and the inferior colliculi with the auditory system.
Reference: The brain: functional divisions, Leo Donnelly, Neurosurgery, Neuroradiology & Neurocritical Care in Anaesthesia
