Basal Ganglia

• Basal ganglia

  A group of subcortical nuclei responsible primarily for: control of voluntary motor movements, procedural learning, habit learning, conditional learning, eye movements, cognition, emotion
• Major basal ganglia structures

  • Corpus Striatum
  • Pallidum
  • Lentiform Nucleus
• Corpus Striatum

  • Ventral striatum is the nucleus accumbens and olfactory tubercle
  • Dorsal striatum is the caudate nucleus and putamen
• Nucleus accumbens

  Cognitive processing of motivation, aversion, reward
• Olfactory tubercle

  Locomotor and attentional behaviors, multisensory integration of olfactory information
• Caudate nucleus

  Motor processes, procedural learning, associative learning and inhibitory control of action
• Putamen

  Regulates movements at various stages (e.g. preparation and execution) and influence various types of learning
• Cell death of the striatum is associated with Huntington's disease. Symptoms: jerky, random, and uncontrollable movements (chorea)
• Pallidum


  • Globus pallidus: regulation of voluntary movement, primarily inhibitory action that balances the excitatory action of the cerebellum
  • Ventral pallidum: regulation of motivational salience, behavior, and emotions
• Related basal ganglia structures

  • Subthalamic nucleus
  • Substantia nigra
  • Ventral tegmental area
  • Amygdala
• Subthalamic nucleus

  Movement regulation
• Substantia nigra

  • Eye movement, fine motor control, motor planning, reward-seeking, learning, and addiction
  • Cell death in SN is associated with Parkinson's Disease. Symptoms: tremor, rigidity, slowness of movement, and difficulty with walking
• Ventral tegmental area

  Reward system (mesocorticolimbic circuit), motivation, cognition, and drug addiction
• Amygdala

  Processing of memory, decision-making, and emotional responses
• Basal ganglia coronal sections


  • Corpus callosum
  • Caudate
  • Claustrum
  • Putamen
  • Crus Cerebri
  • Lateral Ventricles
  • Internal Capsule
  • External Capsule
  • Fornix
  • Hippocampus
  • Red Nucleus
  • Substantia Nigra
  • Subthalamic Nucleus
  • Thalamus
  • Septum Pellucidum
  • Uncus
• Basal ganglia coronal sections

  • Corpus callosum
  • Caudate
  • Claustrum
  • Crus Cerebri
  • Lateral Ventricles
  • Fornix
  • Hippocampus
  • Thalamus
  • Septum Pellucidum
  • Uncus
  • Medial Geniculate Nucleus
  • Lateral Geniculate Nucleus
  • Middle Cerebellar Peduncle
• Direct pathway

  1. Cortical activation activates inhibitory projections to the substantia nigra SNpr and the internal globus pallidus (GPi)

  2. This inhibition of the SNpr and GPi leads to a disinhibition of the thalamic glutamatergic neurons

  3. Resulting in locomotor activation/movement
• Indirect pathway


  1. Activation of the indirect pathway inhibits globus pallidus externa (GPe), leading to a disinhibition of the excitatory neurons of the subthalamic nucleus (STN)

  2. This inhibition of the GPe (by now active STN) increases discharge of excitatory STN neurons and in turn activates the SNpr inhibitory neurons projecting

  3. Resulting in the reduction of locomotor activity and movement
• The basal ganglia is involved in motor, learning, cognitive and emotional processes
• The basal ganglia consists of

  • Caudate nucleus
  • Putamen
  • Nucleus accumbens
  • Globus pallidus
  • Subthalamic nucleus
  • Substantia nigra
  • Ventral pallidum
  • Olfactory tubercle
• The basal ganglia nuclei are located subcortically and best visualised in coronal or horizontal brain sections or by imaging
• The direct and indirect pathway are neural pathways by which movement can be regulated
• Basal ganglia disorders are characterized by symptoms of abnormal movement
• Spinal reflex

  A simple motor action containing: muscle receptors, sensory axons within a peripheral nerve and dorsal root, lower motor neuron and its axon, muscle without central input
• Corticospinal pathway


  • Primary motor cortex (precentral gyrus)
  • Internal capsule
  • Cerebral peduncle
  • Pons (corticospinal fibers)
  • Pyramids
  • Decussation (85 to 90% of fibers) at the level of the medulla/spinal cord junction
  • Travels through spinal cord through the lateral corticospinal tract
  • This upper motor neuron synapses on the ventral horn before the lower motor neuron exits to the muscle
• Lateral corticospinal tract


  Controls extremity muscles and cortical control is contralateral
• Ventral corticospinal tract


  Controls trunk or axial muscles and the control is both ipsilateral and contralateral
• Motor cortical areas


  • Primary Motor: plan and execute voluntary movements
  • Premotor: planning movement, spatial guidance of movement, sensory guidance of movement, in understanding the actions of others, and in using abstract rules to perform specific tasks
  • Supplementary motor area: postural stabilization of the body, the coordination, the control of movements that are internally generated, and the control of sequences of movements
  • Posterior parietal cortex: planned movements, spatial reasoning, and attention
  • Frontal eye fields: control of visual attention and eye movements
• Rubrospinal tract


  • Function: control over the tone of limb flexor muscles
  • Receives input from motor cortex and cerebellum (non-pyramidal route)
  • Red nucleus
  • Cross in the ventral tegmental decussation
  • Descend the spinal cord ventrolateral and partly intermingled with with lateral corticospinal tract
• Tectospinal tract


  • Function: mediate reflexive eye movements
  • Superior colliculus (non-pyramidal route)
  • Cross in the dorsal tegmental decussation
  • Descend near the anterior median fissure terminate mostly in cervical segments
• Vestibulospinal tract

  • Function: maintenance of posture
  • Vestibular nuclei receive input from vestibular apparatus (non-pyramidal route)
  • Cells of the lateral vestibular nucleus descend ipsilaterally as the lateral vestibulospinal tract in the ventral funiculus
• Motor deficits

  • Paralysis: the loss of the ability to move
  • Hypertonia: abnormally high level of muscle tone or tension
  • Ataxia: lack of voluntary coordination of muscle movements
  • Chorea: spasmodic involuntary movements of the limbs or facial muscles
• Stroke

  • Damage to the brain from interruption of its blood supply
  • Haemorrhagic (aka bleed): e.g. Clots, debris, fatty embolisms
  • Ischemic (aka blockage): e.g. High blood pressure, aneurysm
• Haemorrhagic stroke

  • High blood pressure, aneurysm
• Ischemic stroke:

  Clots, debris, fatty embolisms