The cerebral cortex is the outermost layer of the cerebrum, responsible for higher cognitive functions, sensory processing, and motor command generation. It is characterized by its folded appearance (gyri and sulci) and layered cellular organization.

Gross Anatomy: Gyri and Sulci

Major Sulci and Fissures

Sulcus/Fissure	Location	Significance
Longitudinal fissure	Midline, separates hemispheres	Contains falx cerebri, anterior cerebral arteries
Lateral sulcus (Sylvian)	Separates frontal/parietal from temporal	Contains middle cerebral artery
Central sulcus (Rolando)	Separates frontal from parietal	Primary motor (anterior) and sensory (posterior)
Parieto-occipital sulcus	Medial, separates parietal from occipital	Visual cortex boundary
Calcarine sulcus	Medial occipital	Contains primary visual cortex (area 17)
Cingulate sulcus	Medial frontal/parietal	Above cingulate gyrus
Preoccipital notch	Lateral temporo-occipital	Visual association boundary

Major Gyri

Gyrus	Location	Function
Precentral gyrus	Anterior to central sulcus	Primary motor cortex (M1)
Postcentral gyrus	Posterior to central sulcus	Primary somatosensory cortex (S1)
Superior temporal gyrus	Superior temporal lobe	Primary auditory cortex (Heschl gyrus)
Middle temporal gyrus	Middle temporal lobe	Language, auditory association
Inferior temporal gyrus	Inferior temporal lobe	Object recognition, visual association
Fusiform gyrus	Inferior temporal/occipital	Face recognition (fusiform face area)
Parahippocampal gyrus	Medial temporal	Memory, scene recognition
Lingual gyrus	Medial occipital	Visual processing
Cuneus	Medial occipital (above calcarine)	Visual
Precuneus	Medial parietal	Visuospatial, self-awareness
Angular gyrus	Posterior superior temporal	Language, mathematical cognition
Supramarginal gyrus	Parietal operculum	Tactile perception, language
Straight gyrus (gyrus rectus)	Orbitofrontal	Olfactory, behavior

Lobes of the Cerebral Cortex

Frontal Lobe

The frontal lobe is the largest lobe, responsible for motor function, executive control, and language production.

Area	Brodmann	Function
Primary motor cortex (M1)	4	Voluntary movement (contralateral)
Premotor cortex	6	Motor planning, sequencing
Supplementary motor area	6 (medial)	Motor initiation, bimanual coordination
Frontal eye field	8	Voluntary eye movements
Broca area	44, 45	Speech production (dominant hemisphere)
Dorsolateral prefrontal	9, 46	Executive function, working memory
Orbitofrontal cortex	10, 11, 47	Decision-making, reward, social behavior
Anterior cingulate (frontal portion)	24, 32	Error detection, motivation

Parietal Lobe

The parietal lobe integrates sensory information and spatial awareness.

Area	Brodmann	Function
Primary somatosensory (S1)	1, 2, 3	Touch, pain, temperature, proprioception
Secondary somatosensory (S2)	43	Tactile recognition
Posterior parietal cortex	5, 7	Spatial attention, visuomotor integration
Supramarginal gyrus	40	Tactile object recognition, language
Angular gyrus	39	Reading, arithmetic, semantic processing
Precuneus	7 (medial)	Visuospatial imagery, episodic memory

Temporal Lobe

The temporal lobe processes auditory information, language comprehension, and memory.

Area	Brodmann	Function
Primary auditory cortex (A1)	41, 42	Hearing (tonotopic organization)
Auditory association	22	Sound recognition, language comprehension
Wernicke area	22 (posterior)	Language comprehension (dominant)
Middle temporal gyrus	21	Auditory association, semantic memory
Inferior temporal cortex	20, 37	Object recognition, visual association
Fusiform face area	37 (lateral)	Face recognition
Parahippocampal place area	36, 37	Scene recognition
Hippocampus (archicortex)	—	Memory formation, spatial navigation
Amygdala	—	Emotion, fear conditioning

Occipital Lobe

The occipital lobe is dedicated entirely to visual processing.

Area	Brodmann	Function
Primary visual cortex (V1)	17	Initial visual processing (retinotopic)
Visual association (V2)	18	Contour, orientation processing
Visual association (V3, V4, V5)	19	Motion (V5/MT), color (V4), form
Lateral occipital complex	19, 37	Object recognition

Insula

The insula is a hidden lobe deep within the lateral sulcus.

Region	Function
Anterior insula	Interoception, emotion, taste, pain
Posterior insula	Visceral sensation, sensorimotor

Limbic Lobe

The limbic lobe forms a ring on the medial surface of the cerebrum.

Structure	Function
Cingulate gyrus	Emotion, pain, attention
Parahippocampal gyrus	Memory, scene recognition
Isthmus (bridge between cingulate and parahippocampal)	Visual memory

Brodmann Areas

Brodmann areas are numbered regions of the cerebral cortex defined by their cytoarchitecture (cellular organization). The numbering system includes 52 areas.

Key Brodmann Areas by Category

Motor areas:

Area	Name	Function
BA 4	Primary motor cortex (M1)	Voluntary movement
BA 6	Premotor cortex, SMA	Motor planning
BA 8	Frontal eye field	Eye movements
BA 44	Pars opercularis	Broca area (speech)
BA 45	Pars triangularis	Broca area (language)

Somatosensory areas:

Area	Name	Function
BA 1	Primary somatosensory	Texture perception
BA 2	Primary somatosensory	Proprioception, joint position
BA 3	Primary somatosensory	Cutaneous sensation

Visual areas:

Area	Name	Function
BA 17	Primary visual (V1)	Initial visual processing
BA 18	Visual association (V2)	Contour, orientation
BA 19	Visual association (V3, V4, V5)	Motion, color, form

Auditory areas:

Area	Name	Function
BA 41	Primary auditory (A1)	Hearing
BA 42	Auditory association	Sound recognition

Association areas:

Area	Name	Function
BA 9, 10	Dorsolateral prefrontal	Executive function
BA 11, 47	Orbitofrontal	Decision-making, reward
BA 22	Superior temporal	Wernicke area (language comprehension)
BA 39	Angular gyrus	Reading, arithmetic
BA 40	Supramarginal gyrus	Tactile recognition, language
BA 37	Fusiform gyrus	Face/object recognition

Cortical Layers

The neocortex has six layers (laminae):

Layer	Name	Cells	Connections
I	Molecular	Few neurons, mainly dendrites	Apical dendrites of pyramidal cells
II	External granular	Small pyramidal and stellate cells	Corticocortical connections
III	External pyramidal	Medium pyramidal cells	Commissural and association fibers
IV	Internal granular	Stellate cells	Main input layer (thalamic afferents)
V	Internal pyramidal	Large pyramidal (Betz cells in M1)	Output to subcortical structures
VI	Multiform	Fusiform cells	Output to thalamus

Cortical types by layer prominence:

Type	Prominent Layer	Location
Granular (koniocortex)	Layer IV	Primary sensory areas
Agranular	Layer IV absent (layers II/III/V prominent)	Primary motor, premotor
Dysgranular	Layer IV thin	Association areas

Hemispheric Specialization

Function	Dominant Hemisphere (usually left)	Non-Dominant Hemisphere (usually right)
Language	Comprehension and production	Prosody, emotional tone
Motor praxis	Skilled movement planning	—
Visuospatial	—	Spatial attention, navigation
Face recognition	—	Holistic face processing
Emotion	—	Emotional recognition
Music	Rhythm	Pitch, melody
Arithmetic	Calculation	Estimation

White Matter Tracts

Tract Type	Examples	Function
Association fibers (within hemisphere)	Superior longitudinal, inferior longitudinal, uncinate, arcuate, cingulum	Connect cortical regions in same hemisphere
Commissural fibers (between hemispheres)	Corpus callosum, anterior commissure, hippocampal commissure	Connect corresponding cortical areas
Projection fibers (to/from subcortex)	Internal capsule, corona radiata, fornix	Connect cortex to brainstem, spinal cord, basal ganglia, thalamus