AN62.1-6 | Cranial nerve nuclei & Cerebral hemispheres — Glossary

V-shaped white matter structure between the basal ganglia carrying projection fibres between the cortex and brainstem/spinal cord; lacunar infarcts here cause pure motor hemiplegia

Areas 44 and 45 in the left inferior frontal gyrus; motor speech centre; damage causes non-fluent (expressive) aphasia with intact comprehension

Area 22 in the left superior temporal gyrus; sensory speech centre; damage causes fluent but meaningless speech with lost comprehension

Long association fibre bundle connecting Broca's and Wernicke's areas; damage causes conduction aphasia (impaired repetition)

Largest commissural fibre bundle connecting homologous areas of both hemispheres; sectioning causes split brain syndrome

Deep grey matter nuclei (caudate, putamen, globus pallidus, subthalamic nucleus, substantia nigra) modulating voluntary movement via direct and indirect pathways

Caudate nucleus + putamen; the main input nucleus of the basal ganglia receiving cortical afferents

GPi — main output nucleus of the basal ganglia sending inhibitory projections to the thalamus (VL/VA nuclei)

Facilitatory basal ganglia circuit: cortex → striatum → GPi (inhibited) → thalamus disinhibited → movement promoted

Inhibitory basal ganglia circuit: cortex → striatum → GPe → STN → GPi (activated) → thalamus inhibited → movement suppressed

Loss of dopaminergic neurons in the substantia nigra pars compacta; bradykinesia, rigidity, resting tremor, shuffling gait

Violent involuntary flinging movements of the contralateral limbs from subthalamic nucleus lesion

Gateway to consciousness — egg-shaped grey matter flanking the 3rd ventricle relaying all sensory modalities (except smell) to the cortex

Temporal lobe structure essential for consolidation of short-term to long-term memory; bilateral damage causes anterograde amnesia

Almond-shaped nucleus in the temporal lobe for emotional processing, especially fear; bilateral damage causes Kluver-Bucy syndrome

Arterial anastomotic ring at the base of the brain formed by ACA, AComm, ICA, PComm, and PCA; berry aneurysms form at its junctions

MCA — largest cerebral artery supplying the lateral hemisphere; occlusion causes the most common stroke pattern: contralateral face/arm weakness + aphasia

Branches of the MCA supplying the basal ganglia and internal capsule; 'arteries of stroke' — most common site of hypertensive haemorrhage

Loss of vision in the same half of the visual field of both eyes; from lesion of the optic tract, radiation, or visual cortex

Limbic circuit for emotional memory: hippocampus → fornix → mammillary bodies → anterior thalamus → cingulate gyrus → hippocampus

Thiamine (B1) deficiency causing mammillary body damage; anterograde amnesia with confabulation; common in Indian alcoholics

Small deep brain infarct from occlusion of a single perforating artery; most common stroke type in Indian hypertensives; typically in the internal capsule or basal ganglia