Cerebral Hemispheres

Frontal lobe:

• The largest lobe, anterior to the central sulcus, superior to the lateral sulcus, houses the primary motor cortex, premotor/supplementary motor areas, Broca's area (dominant hemisphere), and the prefrontal cortex (executive function, personality, judgment).

Parietal lobe:

• Posterior to the central sulcus, superior to the lateral sulcus, anterior to the parieto-occipital sulcus, houses the primary somatosensory cortex and association areas involved in spatial awareness, language (dominant hemisphere, angular/supramarginal gyri), and sensory integration.

Temporal lobe:

• Inferior to the lateral sulcus: houses the primary auditory cortex, Wernicke's area (dominant hemisphere), and (on its medial surface) structures central to memory and emotion (hippocampus, amygdala).

Occipital lobe:

• The most posterior lobe, posterior to the parieto-occipital sulcus: houses the primary visual cortex, predominantly on its medial surface flanking the calcarine sulcus.

Insula:

• A lobe buried within the depths of the lateral sulcus, not visible on the brain's external surface unless the frontal/temporal/parietal opercula are retracted, involved in visceral sensation/autonomic processing, taste, and interoceptive awareness.

Central sulcus (of Rolando):

• Separates the frontal lobe from the parietal lobe, running obliquely from the superomedial hemisphere surface down toward the lateral sulcus, the boundary between the primary motor cortex (precentral gyrus, anterior) and primary somatosensory cortex (postcentral gyrus, posterior), a critical functional landmark.

Lateral sulcus (Sylvian fissure):

• A deep sulcus separating the temporal lobe (inferiorly) from the frontal and parietal lobes (superiorly), with the insula buried within its depths.

Parieto-occipital sulcus:

• Visible predominantly on the medial hemisphere surface, separating the parietal lobe from the occipital lobe.

Calcarine sulcus:

• On the medial occipital lobe surface, the anatomical landmark for the primary visual cortex, which lies along its upper and lower banks (the cortex here representing the visual field in a precisely retinotopic manner, a key anatomical basis for localising visual field defects to specific cortical regions).

Precentral gyrus:

• Immediately anterior to the central sulcus, housing the primary motor cortex (M1): organised somatotopically (the "motor homunculus"), with the leg/foot region on the medial surface, and the face/hand region occupying a disproportionately large lateral surface area (reflecting the fine motor control these regions require).

Postcentral gyrus:

• Immediately posterior to the central sulcus, housing the primary somatosensory cortex (S1): similarly organised somatotopically (the "sensory homunculus"), mirroring the motor homunculus's disproportionate representation pattern.

Superior, middle, and inferior frontal gyri:

• The three horizontally arranged gyri occupying the lateral frontal lobe surface anterior to the precentral gyrus, contributing to premotor, prefrontal, and (in the inferior frontal gyrus's posterior part, dominant hemisphere) Broca's area function.

Superior temporal gyrus:

• The most superior of the temporal lobe's lateral gyri, housing the primary auditory cortex on its superior surface (within the lateral sulcus, Heschl's gyri) and, in its posterior part (dominant hemisphere), Wernicke's area.

Cingulate gyrus:

• A medial surface gyrus arching over the corpus callosum, part of the limbic system, involved in emotional processing, motivation, and autonomic regulation.

Parahippocampal gyrus:

• A medial temporal lobe gyrus, continuous with the hippocampal formation, part of the limbic system, critical for memory encoding.

Lateral surface:

• Houses the majority of the primary motor and somatosensory cortex, the lateral sulcus/insula, Broca's and Wernicke's areas, and most of the frontal/parietal/temporal association cortex.

Medial surface:

• Houses the cingulate gyrus, the corpus callosum (viewed in cross-section), the medial extent of the motor/sensory homunculi (leg/foot representation), the parieto-occipital and calcarine sulci, and the primary visual cortex.

Inferior surface:

• Houses the orbital frontal cortex (anteriorly), the parahippocampal gyrus and hippocampal formation, and the inferior/fusiform temporal gyri (posteriorly), including regions important for visual object/face recognition.

Primary motor cortex (M1):

• Precentral gyrus (Brodmann area 4): initiates voluntary movement, giving rise to a major component of the corticospinal/corticobulbar tracts, somatotopically organised.

Primary somatosensory cortex (S1):

• Postcentral gyrus (Brodmann areas 3, 1, 2): receives conscious touch, proprioception, vibration, pain, and temperature information (relayed via the thalamus), somatotopically organised, mirroring M1's homunculus.

Primary visual cortex (V1):

• Calcarine sulcus region, occipital lobe (Brodmann area 17): receives visual information from the lateral geniculate nucleus (thalamus) via the optic radiations, organised retinotopically.

Primary auditory cortex:

• Superior temporal gyrus (Heschl's gyri, within the lateral sulcus, Brodmann areas 41, 42), receives auditory information from the medial geniculate nucleus (thalamus), organised tonotopically (by sound frequency).

Broca's area:

• Posterior inferior frontal gyrus (Brodmann areas 44, 45), classically in the dominant hemisphere (left, in most right-handed and many left-handed individuals), responsible for the motor programming of speech production; its lesion causes expressive (Broca's/non-fluent) aphasia: effortful, non-fluent speech with relatively preserved comprehension.

Wernicke's area:

• Posterior superior temporal gyrus, dominant hemisphere: responsible for language comprehension; its lesion causes receptive (Wernicke's/fluent) aphasia: fluent but often nonsensical/paraphasic speech with impaired comprehension.

Prefrontal cortex:

• The anterior frontal lobe, anterior to the premotor areas: responsible for executive function (planning, judgment, working memory, inhibition of inappropriate behaviour) and personality; its damage classically produces disinhibition, poor judgment, and personality change (the classic historical illustration being the Phineas Gage case) rather than a discrete, easily testable focal deficit like the primary sensory/motor areas.