BRODMANN AREA

Frontal lobe boundaries

Central sulcus separates frontal from parietal lobe; lateral (Sylvian) fissure separates frontal from temporal lobe

Brodmann area (BA)

Numbering system of cerebral cortex regions based on function, coined by Korbinian Brodmann

Primary motor cortex (BA 4)

Located in precentral gyrus; responsible for voluntary movement of contralateral skeletal muscles

Precentral gyrus

Gyrus anterior to central sulcus; contains primary motor cortex (BA 4)

Contralateral motor control

Left motor cortex controls right body and vice versa

Lesion of BA 4

Results in contralateral weakness (paresis)

Paresis

Partial weakness due to motor pathway damage

Paralysis

Complete loss of motor function due to complete denervation

Motor homunculus

Map of body representation in primary motor cortex

Somatotopy

Body is mapped in a specific spatial organization in the cortex

Medial motor homunculus

Lower limb representation

Lateral motor homunculus

Upper limb and trunk representation

Inferolateral motor homunculus

Face and head representation

Cortical magnification

Larger cortical area for body parts needing fine motor control (hands, face)

Gray matter location

Outer cortex composed of neuronal cell bodies

White matter

Myelinated axons forming tracts connecting CNS regions

Projection fibers

White matter fibers connecting cortex to lower CNS structures

Phantom limb sensation

Perception of sensation in amputated limb due to cortical representation

Corticospinal tract

Motor pathway from cortex to spinal cord controlling trunk and limbs

Corticobulbar tract

Motor pathway from cortex to brainstem controlling head and neck

Corona radiata

Fan-shaped white matter fibers above internal capsule

Internal capsule

White matter structure where descending motor fibers pass

Posterior limb of internal capsule

Carries corticospinal fibers (limbs and trunk)

Genu of internal capsule

Carries corticobulbar fibers (face and head)

Decussation of motor pathways

Corticospinal fibers cross to opposite side in brainstem/spinal cord

Upper motor neuron pathway

Starts in cortex and synapses on lower motor neurons in brainstem/spinal cord

Primary motor cortex output

BA 4 sends signals via corticospinal and corticobulbar tracts

Anterior cerebral artery (ACA)

Supplies medial frontal lobe and medial motor homunculus (lower limb)

Middle cerebral artery (MCA)

Supplies lateral cerebrum including face and upper limb areas

ACA stroke deficit

Lower limb weakness greater than upper limb weakness

MCA stroke deficit

Face and upper limb weakness greater than lower limb weakness

Dominant hemisphere MCA stroke

May cause speech/language impairment

Cerebrovascular disease (CVD)

Any brain vascular disorder including ischemic and hemorrhagic stroke

Stroke definition

Vascular event causing interruption of cerebral blood supply

Hemorrhagic stroke

Blood vessel rupture causing bleeding into brain tissue

Ischemic stroke

Blood vessel blockage causing reduced blood flow

Hypertension risk in hemorrhagic stroke

Severely elevated BP can cause vessel rupture

Aneurysm

Weak arterial wall bulge that may rupture causing hemorrhage

Atherosclerosis

Plaque buildup causing vessel narrowing and ischemic stroke

Cerebral embolism

Traveling clot or material blocking cerebral artery

Thrombolytics

Drugs used to dissolve clots in ischemic stroke

CT scan brain use

Primary imaging for detecting ischemic vs hemorrhagic stroke

Normodense brain tissue

Gray matter appears gray and homogenous on CT

Hyperdense CT appearance

Bone, blood, calcium appear white on CT

Hypodense CT appearance

CSF and ventricles appear black on CT

Midline shift

Deviation of brain structures due to mass effect like hemorrhage

Primary motor association cortex (BA 6)

Plans and sequences voluntary movement

Motor planning function of BA 6

Determines which muscles contract and in what order

BA 6 role

Refines motor commands before execution in BA 4

Basal ganglia function

Initiates and stops movement; motor control modulation

Cerebellum function

Coordinates movement accuracy and balance

Motor association network

BA 6 + basal ganglia + cerebellum integration

Frontal eye field (BA 8)

Controls voluntary eye movements (saccades)

BA 8 lesion effect

Conjugate gaze deviation toward lesion side

BA 8 stimulation

Both eyes move away from stimulated side

Saccadic eye movement

Rapid voluntary eye movement shifting gaze

Prefrontal cortex (BA 9,10,11)

Higher cognitive functions like planning, judgment, personality

Executive function

Decision-making, reasoning, planning, motivation

Frontal lobe role in behavior

Controls personality and social behavior regulation

Phineas Gage case

Frontal lobe injury caused personality and behavioral changes

Broca’s area (BA 44)

Motor speech production area in dominant hemisphere

Broca’s aphasia

Non-fluent speech with preserved comprehension

Expressive aphasia

Impaired speech production despite intact understanding

Wernicke’s area (BA 22)

Language comprehension area

Wernicke’s aphasia

Fluent but meaningless speech with poor comprehension

Arcuate fasciculus

White matter tract connecting Broca’s and Wernicke’s areas

Repetition ability

Depends on intact arcuate fasciculus

Aphasia definition

Language disorder affecting speech, comprehension, reading, writing

Primary somatosensory cortex (BA 3,1,2)

Postcentral gyrus; processes touch sensation

Somatosensation

Touch, pain, temperature, proprioception, vibration

Sensory homunculus

Map of body sensory representation in cortex

Sensory vs motor homunculus

Motor (BA4) sends output; sensory (BA3,1,2) receives input

Spinothalamic tract

Carries pain, temperature, and crude touch

Dorsal column-medial lemniscus

Carries fine touch, vibration, proprioception

Trigeminal pathway

Sensory pathway for head and neck

Thalamus role

Relay station for all sensory pathways except olfaction

Contralateral sensory processing

Sensory cortex processes opposite side of body

Somatosensory association cortex (BA 5)

Interprets touch (size, texture, shape)

Stereognosis

Ability to identify objects by touch without vision

Astereognosis

Inability to recognize objects by touch

Graphesthesia

Recognition of writing on skin by touch

Agraphesthesia

Inability to recognize writing on skin

Statognosia

Ability to perceive limb position in space

Astatognosia

Inability to perceive limb position

Barognosis

Ability to distinguish weight differences

Abarognosia

Inability to distinguish weight differences

Posterior parietal cortex (BA 7)

Integrates multisensory information for spatial awareness

Multimodal integration

Combining visual, auditory, and somatosensory input

BA 7 function

Sends integrated information to prefrontal cortex for decision-making

Occipital lobe function

Primary center for visual processing

Primary visual cortex (BA 17)

Processes raw visual input near calcarine fissure

Visual association cortex (BA 18)

Interprets and recognizes visual stimuli

Visual agnosia

Inability to recognize objects despite intact vision

Primary auditory cortex (BA 41)

Processes basic auditory perception

Auditory association cortex (BA 42)

Interprets sound features like pitch and location

Temporal lobe function

Auditory processing and language comprehension

Wernicke area location

Junction of temporal and parietal lobe (dominant hemisphere)

Language comprehension

Process of understanding spoken and written language

Motor speech pathway

Broca’s area → brainstem nuclei → speech muscles

Voluntary movement pathway

BA4 → corticospinal/corticobulbar tracts → muscles