Anatomy of the Brain
The human brain is organized into distinct anatomical regions with specialized structures that work together to support cognitive, sensory, motor, and emotional functions 1.
Major Anatomical Divisions
The brain consists of four primary lobes (frontal, parietal, temporal, and occipital), along with deeper structures including the central core, limbic system, and infratentorial components 2.
Cerebral Lobes
The cerebral hemispheres are divided into:
- Frontal lobe: Controls executive functions, motor planning, and contains Broca's area for language production
- Parietal lobe: Processes sensory information and spatial awareness
- Temporal lobe: Manages auditory processing, memory formation, and contains Wernicke's area for language comprehension
- Occipital lobe: Dedicated to visual processing 2
Central Core Structures
The central core represents the deep brain structures and includes several critical components 3:
The insular cortex forms the most superficial aspect of the central core, divided by a central sulcus into anterior (typically 3 short gyri) and posterior portions (2 long gyri), bounded by anterior, superior, and inferior limiting sulci 3.
Deep gray matter nuclei arranged from lateral to medial include:
- Claustrum: Located between extreme and external capsules
- Putamen and globus pallidus (lentiform nucleus): Positioned between external and internal capsules
- Caudate nucleus: Lies medial to the internal capsule in the anterior half
- Thalamus: The major sensory relay station, positioned medial to the internal capsule in the posterior half 3, 4
White Matter Pathways
The internal capsule serves as a critical parasagittal barrier containing motor and sensory tracts, with major functional importance 3. Key white matter structures include:
- Extreme capsule: Short association fibers extending to opercula
- External capsule: Contains uncinate fascicle, inferior fronto-occipital fascicle, and claustrocortical fibers in anteroposterior sequence
- Internal capsule: Houses the corticospinal tract, corticoreticular pathway, medial lemniscus, and spinothalamic tract 2, 3
- Commissural tracts: Connect corresponding regions between hemispheres 4
- Association bundles: Link different cortical areas within the same hemisphere 4
Limbic System
The limbic system controls emotion, motivation, behavior, memory, and olfaction 2. This system includes interconnected structures essential for emotional processing and memory consolidation.
Language Centers
Critical language structures include:
- Broca's area: Motor speech production (frontal lobe)
- Wernicke's area: Language comprehension (temporal lobe)
- Arcuate fasciculus: Connects these two language centers 2
Infratentorial Structures
The posterior fossa contains:
- Brainstem: Includes medulla oblongata, pons, and midbrain with periaqueductal gray matter
- Cerebellum: Cerebellar hemispheres and peduncles
- These structures connect to the central core through multiple white matter pathways without natural anatomical separation 3, 5
Ventricular System
The brain contains a system of CSF-filled spaces:
- Lateral ventricles: Adjacent to periventricular white matter
- Third ventricle: Between thalami
- Fourth ventricle: Between brainstem and cerebellum 5
Clinical Relevance
Understanding brain anatomy is essential for localizing neurological deficits and planning treatment approaches. The internal capsule and its vascularization represent a particularly important functional barrier when considering surgical approaches to deep brain structures 3. Different quadrants of the central core require distinct surgical considerations based on their relationship to critical white matter tracts and vascular structures.