Nuclei Basales Overview

Nuclei Basales

• Nuclei basales are masses of gray matter formed by groups of neurons within the substantia alba of the cerebrum

• These structures are hidden within the substantia alba encephali, making them difficult to view without cerebral sectioning.

• They are also known as subcortical nuclei of the telencephalon.

• Nuclei basales play a crucial role in the coordination of motor movements, initiation of voluntary movements, and posture control associated with voluntary movements.

• Three fundamental tasks of basal ganglia include:

  • Controlling complex motor activities (e.g., writing, using scissors, sports)
  • Controlling sequential motor movements and integrating information from memory and performing tasks
  • Controlling speed and magnitude (number of steps and distance) of movements

Components of Nuclei Basales

• Nucleus caudatus: The largest basal ganglion, divided into caput, corpus, and cauda sections.

  • Works together with the putamen to form the neostriatum, a functional unit
  • Afferent connections: cortex cerebri, thalamus, substantia nigra, corpus amygdaloideum
  • Efferent connections: globus pallidus, substantia nigra
  • Located below the lateral ventricles, above the thalamus

• Nucleus lentiformis: Located on the outer side of the nucleus caudatus and thalamus

  • Composed of putamen (outer part) and globus pallidus (inner part)
  • The putamen is separated from the claustrum by the capsula externa
  • The globus pallidus is separated from the nucleus caudatus by the crus anterius capsula internae; and from the thalamus by the crus posterius capsula internae
  • Afferent connections: neostriatum, subthalamic nucleus, substantia nigra
  • Efferent connections: thalamus, subthalamic nucleus

• Corpus amygdaloideum: Almond-shaped structure located at the anterior end of the temporal horn of the lateral ventricle

  • Plays a major role in emotion formation and processing within the limbic system
  • Receives external stimuli after the primary sensory cortex
  • Associates stimuli with positive and negative emotions from memory
  • Involved in emotional evaluation and expression

• Claustrum: Located beneath the insula cortex; separated from the cortex cerebri by the capsula extrema, and from the putamen by the capsula externa

  • Connected to cortical centers, such as vision and audition (hearing)

Other Information

• Descending pathways originating from the cerebral cortex are part of the pyramidal system; basal ganglia pathways are part of the extrapyramidal system.

• The subthalamic nucleus is located at the dorsal lateral part of the upper end of the substantia nigra. Damage to this area can cause contralateral hemiballismus (involuntary, severe shaking and jumping movements).

  • Afferent connections: globus pallidus
  • Efferent connections: globus pallidus, substantia nigra

• The substantia nigra is a core component of the mesencephalon (midbrain), dark-colored due to melanin pigment

  • Dysfunction leads to Parkinson's disease
  • Afferent connections: neostriatum
  • Efferent connections: neostriatum, thalamus, superior colliculus

• The cerebral cortex and basal ganglia exhibit extensive communication networks. This allows the basal ganglia to influence structures in the brainstem and spinal cord where there is no direct connection.

• The fasciculus uncinatus connects the frontal lobe to the limbic system enabling the integration of rational thought with emotional processing; and directly connects the limbic system to the olfactory bulb for sensory processing.