Lecture 4 Basal Ganglia Flashcards
What is the basal ganglia? Is it white or grey matter?
The “basal ganglia” refers to a group of subcortical nuclei within the brain responsible primarily for motor control, as well as other roles such as motor learning, executive functions, emotional behaviors, and play an important role in reward and reinforcement, addictive behaviors and habit formation. It is grey matter.
what are the 5 nuclei of the basal ganglia?
the caudate and putamen (striatum), the globus pallidus, the subthalamic nucleus, and substantia nigra.
what is the basal ganglia involved in?
The basal ganglia is involved in motor control. It is involved in eye movement (planning on where to look), cognitive functions (planning, using body and space well), and the limbic system (emotions)
What is the direct and indirect motor pathway for the basal ganglia?
Cortical input will go to the striatum (caudate and putamen) and will go through the direct pathway OR the indirect pathway. Substantia nigra provides dopamine to the neurotransmitter to promote basal ganglia function.
The direct pathway carries inhibitory information from the striatum directly to GP internus which then goes to the thalamus. The thalamus then sends excitatory information to the cortex.
The indirect pathway goes through the GPe and STN and sends excitatory information to the GP internus which wil then go to the thalmus. The thalamus then sends excitatory information to the cortex.
What is the current viewpoint of the basal ganglia and motor function? What happens if there is dysfunction?
It is believed that the basal ganglia is intimately connected with the cortex through parallel loops. The parallel loops can be divided into motor, cognitive and limbic loops.
Most commonly, dysfunction within the basal ganglia can lead to movement disorders (dyskinesias) like akenesia, bradykinesia, or hyperkinesia.
What are the outputs and inputs of the basal ganglia?
The basal ganglia receives input from the cerebral cortex and the limbic system.
The basal ganglia outputs information to the limbic system, thalamus, and midbrain. As stated before, there are parallel loops which influence voluntary movement, cognitive processes, as well as emotional motor behavior.
How does the basal ganglia influence perceptual motor decision-making? what happens to someone with PD?
The basal ganglia impacts the way someone interprets sensory information from the environment which influences motor decisions.
When the basal ganglia is affected by Parkinson’s disease, turning is a perceptual decision that becomes difficult. Turning involves planning of cervical and trunk rotation while changing the angles of hip rotation and simultaneously anticipating changes in the environment.
People with PD will have slow, small, and narrow steps.
What are the basal ganglia motor loops?
The body movement loop and the oculomotor loop
What are the basal ganglia non-motor loops?what common pathologies arise from non-motor loops?
The prefrontal loop and the limbic loop.
Pathologies characterized by non-motor loops include emotional, cognitive, and psychiatric deficits. Examples include OCD, Tourette’s syndrome, and attention deficit disorders.
The prefrontal loop is the connection from the prefrontal cortex for initiation and selection of motor activities.
The limbic loop (emotion) is the connection between the hippocampus, amygdala, and anterior cingulate which influences motor output.
what happens when there is damage to the indirect pathway?
Damage to the indirect pathway will result in overstimulation of the motor cortex HUNTINGTONS DISEASE. People have chorea and involuntary movements.
what happens when there is damage to the direct pathway?
Damage to the direct pathway will result in increased inhibition of the motor cortex PARKINSONS DISEASE. People will have a loss of automatic movement, increased rigidity, and bradykinesia.
What causes a movement disorder like Parkinson’s Disease?
Parkinson’s disease arises because there is a loss of dopaminergic production in the substantia nigra
What are current concepts on Parkinson’s disease and connections to the midbrain and spinal cord? (MLR and PNN)
When the basal ganglia is affected, it can no longer send messages to the mesencephalic locator region (MLR) of the brainstem which will affect the control of gait and balance. Dysfunction of cholinergic neurons of the PNN that are located in the MLR will cause axial symptoms that affect muscle tone (stooped posture).
Studies have shown that stimulation of structures that are apart of the MLR alleviates locomotor symptoms in patients with PD.
How is a movement formed concerning corticospinal tracts?
Preplanning takes place in the prefrontal cortex.
Preparation of movement takes place in the premotor cortex. This structure is in charge of determining how many motor units to fire and the rate at which they will fire.
Initiation, selection, memory, and emotional arise from the basal ganglia.
Activation takes place at the primary motor cortex.
what is bradykinesia?
Bradykinesia arises when there is a loss of function of the neurotransmitter dopamine and loss of inhibitory pathways from the striatum. Therefore, there is a loss of automatic movement.
