Basal ganglia movement modulation Domina Petric, MD

Introduction Basal ganglia are collection of nuclei that are found deep in the base of the forebrain. Basal ganglia are developed from the telencephalon so the basal ganglia relate to the functions of the cerebral cortex. Basal ganglia recieve inputs from various regions of the cerebral cortex.

Basal ganglia Basal ganglia interact with upper motor neurons and are concerned with gating proper initiation of movement. Ventral anterior-ventral lateral (VA-VL) complex of the thalamus sends signals up into the motor cortex: excitatory trigger for the execution of the movement. Basal ganglia provide inhibitory output to the thalamus. Thalamic input is crucial for the upper motor neurons to send excitatory signals to the lower motor neurons. The basal ganglia has inhibitory control over the motor thalamus and that is how basal ganglia modulate movement control.

Major basal ganglia function is MODULATION OF THALAMO-CORTICAL ACTIVITY!

Basal ganglia function initiation of behavior suppression of unwanted behavior

Parallel pathways (streams) Body movement loop Oculomotor loop Motor loops Prefrontal loop Limbic loop Non-motor loops

Parallel pathways (streams) Cortical input Basal ganglia: striatum Basal ganglia: pallidum Thalamus Cortical targets

Body movement loop Cortical input is from primary motor cortex, premotor cortex, supplementary motor cortex and somatosensory cortex. That input goes first to the PUTAMEN and from the putamen to the LATERAL GLOBUS PALLIDUS. From the basal ganglia input goes to the VA-VL thalamic nuclei complex. Motor thalamus then sends signals into the motor cortex: INITIATION OF THE MOVEMENT or SUPRESSION OF UNWANTED MOVEMENTS.

Oculomotor loop Cortical input is from the frontal eye field and supplementary eye field. That input goes into the body of CAUDATE and from caudate into the GLOBUS PALLIDUS and SUBSTANTIA NIGRA (PARS RETICULATA). Input then goes into the MEDIODORSAL AND VENTRAL ANTERIOR THALAMIC NUCLEI and then to cortical targets.

Prefrontal loop Cortical input is from dorsolateral prefrontal cortex. Input goes then into the ANTERIOR CAUDATE and then into the GLOBUS PALLIDUS and SUBSTANTIA NIGRA. Input then goes into the MEDIODORSAL and VENTRAL ANTERIOR NUCLEUS of the THALAMUS. Last station is cortical target.

Limbic loop Last station is cortical target. Thalamic station is MEDIODORSAL NUCLEUS. Next station is VENTRAL STRIATUM and then VENTRAL PALLIDUM. Cortical input is from anterior cingulate cortex, orbital frontal cortex, amygdala and hippocampus.

Basal ganglia dysfunction Hypokinetic movement disorders (Parkinsonism): failure of initiation of the movement. Hyperkinetic movement disorders (Huntington´s disease): failure of suppression of the unwanted movement. Affective and cognitive disorders (depression, schizophrenia, Tourette´s syndrome): failure of initiation of a particular behavior program and/or failure of supression of an inappropriate behavior program.

Dopamine Dopamine from the midbrain (Substantia nigra, pars compacta) is important neuromodulator of basal ganglia function.

Ventral tegmental area (VTA) Ventral tegmental area provides a dopamine projection to the ventral part of the striatum that is included into the limbic processing stream.

They are important source of modulation of the basal ganglia. Subthalamic nuclei Subthalamic nuclei provide input to the internal part of the globus pallidus. They are important source of modulation of the basal ganglia.

Putamen Putamen is the principal recipient of the inputs from the frontal motor cortex and the parietal somatosensory cortex: MODULATION OF THE BODY MOVEMENTS.

Caudate nucleus Caudate nucleus recieves inputs from the frontal cortex, the anterior part of the premotor cortex which includes frontal eye field: MODULATION OF THE EYE MOVEMENTS AND MOVEMENT OF THE MIND.

Nucleus accumbens Nucleus accumbens is recieving input from the ventromedial parts of the forebrain that are concerned with processing EMOTION or AFFECT.

Basal ganglia pathways SUBTHALAMIC NUCLEUS MODULATES ACTIVITY OF GLOBUS PALLIDUM INTERNAL SEGMENT. Basal ganglia pathways Direct pathway Indirect pathway CORTEX STRIATUM PALLIDUM (INTERNAL SEGMENT) THALAMUS CORTEX STRIATUM GLOBUS PALLIDUM EXTERNAL SEGMENT SUBTHALAMIC NUCLEUS GLOBUS PALLIDUM INTERNAL SEGMENT

Literature https://www.coursera.org/learn/medical-neuroscience/lecture: Leonard E. White, PhD, Duke University