Lecture 16-Basal Ganglia.pdf

Basal Ganglia Dr. Kelly C. S. Roballo [email protected] VCOM-Main Building Room 341 Learning Objectives • 1. Identify the basal ganglia structures and identify neural structures surrounding the basal ganglia. • 2. Describe the overall function of the basal ganglia in movement control and initi...

Basal Ganglia Dr. Kelly C. S. Roballo [email protected] VCOM-Main Building Room 341 Learning Objectives • 1. Identify the basal ganglia structures and identify neural structures surrounding the basal ganglia. • 2. Describe the overall function of the basal ganglia in movement control and initiation in association with medial and lateral motor systems. • 3. Identify the tracts exiting and entering the basal ganglia. • 4. Identify the neuronal order of tracts entering and exiting the basal ganglia. • 5. Identify the direct and indirect pathway • Chapter 8- basic clinical neuroscience book Basal Ganglia Striatum receives all inputs to the basal ganglia n The basal ganglia are a collection of gray matter nuclei located deep within the white matter of the cerebral hemispheres Blumenfeld, Neuroanatomy through Clinical Cases Neural structures involved in the control of movement Why do we need Basal Ganglia? Basal ganglia are involved in generation of goal-directed voluntary movements: § Motor learning § Motor pattern selection § Initiation of movements Location of basal ganglia Purves, Neuroscience Purves, Neuroscience Purves, Neuroscience Purves, Neuroscience Basal Ganglia Patients with basal ganglia lesions can have either hypokinetic or hyperkinetic movement disorders Parkinson’s disease (hypokinetic): rigidity, slowness, and marked difficulty initiating movements Huntington’s disease (hyperkinetic): uncontrolled involuntary movements produce a random pattern of jerks and twists *Clinical Correlation Blumenfeld, Neuroanatomy through Clinical Cases Basal Ganglia & Thalamus Blumenfeld, Neuroanatomy through Clinical Cases Basal Ganglia & Thalamus Blumenfeld, Neuroanatomy through Clinical Cases Inputs to the Basal Ganglia The main input comes from massive projections from the entire cerebral cortex to striatum Putamen is the most important input nucleus of the striatum for motor control pathways: most cortical inputs are excitatory and use glutamate Another important input is the substantia nigra pars compacta: this dopaminergic nigrostriatal pathway is excitatory to some cells and inhibitory to others Blumenfeld, Neuroanatomy through Clinical Cases Basal Ganglia Outputs For motor control, the substantia nigra pars reticulata convey information for the head and neck, while the internal segment of the globus pallidus conveys information for the rest of the body These output pathways are inhibitory and use GABA. The main output pathways are to the VL and VA nuclei of the thalamus via the thalamic fasciculus Blumenfeld, Neuroanatomy through Clinical Cases Basal Ganglia Internal Connections Direct pathway: travels from the striatum directly to the internal segment of the globus pallidus or the substantia nigra pars reticulata Indirect Pathway: takes a detour from the striatum, first to the external segment of the globus pallidus and then to subthalamic nucleus, before reaching the internal segment of the globus pallidus or the substantia nigra pars reticulata Blumenfeld, Neuroanatomy through Clinical Cases Basal Ganglia Internal Connections • The net effect of excitatory input from the cortex through the direct pathway will be excitation (less inhibition) of the thalamus • The net effect of excitation of the indirect pathway will be inhibition of the thalamus, resulting in inhibition of movements through connections back to the cortex • GPi: globus pallidus pars interna • GPe: globus pallidus pars externa • SNr: substantia nigra pars reticulata • STN: subthalamic nucleus *Clinical Correlation Direct- Parkinson’s disease Indirect- Huntington's disease Blumenfeld, Neuroanatomy through Clinical Cases Blumenfeld, Neuroanatomy through Clinical Cases Basal ganglia loops – motor and non-motor Frontal Lobe Outputs of the Four Parallel Channels through the Basal Ganglia Blumenfeld, Neuroanatomy through Clinical Cases Bradykinetic (slowed movements) disorders can be caused by increased inhibitory basal ganglia outflow to the thalamus *Clinical Correlation Blumenfeld, Neuroanatomy through Clinical Cases • The abnormalities associated with basal ganglia are the results of an imbalance in activity in the direct/indirect pathways.