BASAL GANGLIA

Basal ganglia are subcorticle nuclei of grey matter located in the interior part of cerebrum near about base 3

the four principle nuclei of the basal ganglia are the : 1.striatum (caudate&p utamen) 2.globus pallidus 3.substantia Nigra 4.subthalami c nucleus

Functions of basal ganglia It play important motor function in starting and stopping motor functions and inhibiting unwanted movement. 1. Selection, Initiation of movement, Planning & programming (discharge before movement begins ). 2. Motor control of the final common pathway It changes the timing and scales the intensity of movements. Putamen circuit is inhibitory. Executes skilled motor activities for example cutting paper with a scissor, hammering on nail, shooting a basket ball & like throwing a base ball. Putamen circuit has indirect connection to cortex via thalamus.while caudate has direct conection to the cortex from thalamus. 6

Cont… Caudate circuit is excitatory, has instinctive function which works without thinking and need quick response. eg. response after seeing a lion. [Note: effects of basal ganglia on motor activity are generally inhibitory.] 7

Muscle tone (lesion increases). Cognitive functions (Frontal cortex) Lesions disrupt performance. Speech, lesion of left caudate results in disturbed speech dysarthria. Many nonmotor functions –memory & other cognitive functions Cont…

Lesions of basal ganglia Lesions of the basal ganglia produce effects on contra lateral side of the body Damage to basal ganglia does not cause paralysis. However it results in abnormal movements

Parkinson’s Disease Each side of the midbrain contains a nucleus called the substantia nigra. Neurons in the substantia nigra inhibit the activity of basal nuclei by releasing dopamine. Damage to SN neurons Decrease in dopamine secretion Increased activity of basal nuclei Gradual increase in muscle tone Appearance of symptoms of Parkinson’s disease: tremor, slow movement, inability to move, rigid gait, reduced facial expression,tremor at rest