Connections


These can be divided into three main categories:-

Afferents

  • Corticostriate
  • thalamostriate
  • Nigrostriate

Main entry point is the neostriatum

Efferent

  • Pallidothalamic
  • Pallido-rubral
  • Pallido-reticular

Globus pallidus is the main exit point

Two main bundles :

  • Lenticular fasciculus
  • Ansa lenticularis..

Reciprocal interconnections among the nuclear masses of the basal ganglia, for example:

  • Nigrostriate and strionigral
  • Striopallidal and pallidostriate
  • Pallido-sub thalamic and subthalamo-pallidal
 

The direct loop
The indirect loop

  • Cortical fibres project to the neostriatum

  • Striatal efferents project to the globus pallidus

  • Efferents from the Globus pallidus to the dorsal thalamus

  • Thalamic neurons project to specific areas of the cerebral cortex
  • Cortical fibres project to the neostriatum

  • Striatal efferents neurons project to globus pallidus

  • Efferents from Globus project to Globus Pallidus (GPi) and / or Substantia Nigra (SNr)

  • Efferents from Substantia Nigra / Subthalamic nucleus project to the dorsal thalamus
  • Thalamic neurons project to cerebral cortex

Functions
  • To Modulate and execute motor commands initiated by cerebral cortex

The function of basal ganglia is often described in terms of brake hypothesis . To sit still, you must put the brakes on all movements except those reflexes that maintain the upright posture. To move, you must apply brakes on some postural reflexes and release brakes on voluntary movements.

  • Integration of neurobehavioral variables

Basal ganglia are involved in integration of a vast number of neurobehavioral variables such as motivation, memory, olfaction, target location,