Basalganglier

Basal ganglia, in Swedish often referred to as Basalganglier, are a group of interconnected subcortical nuclei in the brain that participate in the regulation of voluntary movement, as well as aspects of cognition and emotion. They form part of motor, associative, and limbic circuits that link the cerebral cortex with the thalamus and brainstem.

Anatomy: The term typically includes the striatum (caudate nucleus and putamen) and the lentiform nucleus (putamen together with the globus pallidus), the subthalamic nucleus, and the substantia nigra (pars compacta and pars reticulata). The ventral striatum, which contains the nucleus accumbens, is involved in reward and motivation. The main output from the basal ganglia is via the internal segment of the globus pallidus and the substantia nigra pars reticulata to thalamic nuclei that project back to the cortex.

Function: Basal ganglia contribute to action selection by facilitating intended movements and suppressing competing or unwanted movements. They operate within two major pathways: the direct pathway, which tends to promote movement, and the indirect pathway, which tends to inhibit competing motor programs. Dopamine, released from the substantia nigra, modulates these pathways and influences movement control.

Clinical significance: Disruptions of basal ganglia function lead to movement disorders. Parkinson's disease involves loss of dopaminergic neurons in the substantia nigra, producing rigidity, bradykinesia, and tremor. Huntington's disease causes degeneration of striatal neurons with involuntary movements and cognitive decline. Other conditions include dystonia, Tourette syndrome, and hemiballismus. Treatments range from dopaminergic and other pharmacological therapies to surgical approaches such as deep brain stimulation targeting the subthalamic nucleus or the internal globus pallidus.