Week 8 Vocabulary Flashcards
(25 cards)
Ataxia
The classic sign of cerebellar damage, essentially uncoordinated movements. There are many signs and symptoms of ataxia.
Purkinje Cell
Classic neurons of the cerebellum, they have massive dendritic arborizations oriented in a single plane. They are GABAergic, meaning they are inhibitory neurons. They are responsible for integrating the many inputs to the cerebellum, ultimately resulting in motor coordination.
Afferent
An input to a system
Efferent
An output from a system
Efference Copy
The copy of information the cerebellum receives from two sources: 1) the cerebral cortex that sends information to motoneurons and 2) the command that motoneurons receive. This is important for detecting discrepancies, and letting the cerebellum know what the planned movement was. The cerebellum uses this information in concert with sensory reafference to modulate movement.
Sensory Reafference
A copy of sensory information sent to the cerebellum so it knows the result of a movement, this includes information on joint angles and proprioceptive information. The cerebellum uses this information along with efference copy to ensure that the movement plan matches the outcome of the movement, and sends signals to adjust subsequent movements if they do not match.
Associative Learning
The cerebellum allows us to learn what it feels like to perform a movement correctly, this allows us to master movements and “feel” when they have been performed incorrectly.
Vermis
Medial portion of the cerebellum that controls midline structures that are responsible for postural control, gait, and speech.
Paravermis
The region just lateral to the vermis that controls movements of the limbs.
Lateral Lobes
The largest areas of the cerebellum, whose function is still under investigation. It is possible that these are involved in motor learning, or non-motor functions such as language communication.
Flocculus
Another region of the cerebellum that is involved in eye movement coordination, such as keeping the eye steady and smooth pursuit.
Vestibulo-ocular Reflex (VOR)
This reflex moves eyes in opposition to head movement, allowing you to maintain gaze on a single point. The vestibular system is much quicker than the visual system, and so the cerebellum uses vestibular input to control eye movements appropriately. The flocculus and nodulus (regions of the cerebellum) are responsible for modulating the gain of this reflex, or turning it off if you want your eyes to move with your head.
Ipsilateral
This means the same side. Cerebellar damage causes ataxia on the ipsilateral (same side) of the body. This is in contrast to the contralateral (opposite side) paralysis caused by injury to the cerebral cortex or other parts of the hindbrain.
Basal Ganglia
The deep telencephalic region of the brain that is responsible for action selection, specifically selecting single actions to perform; importantly, it is also responsible for selecting a single mood, perception, or thought.
Pallidum
A basal ganglia structure that is always active at rest to inhibit actions. Cells here contain GABA and are inhibitory. This region is also called the globus pallidus.
Striatum
The second major basal ganglia structure that also contains inhibitory neurons. These neurons project to the palladium, and their activation leads to disinhibition of an action. The striatum is composed of the caudate and the putamen.
Disinhibition
The palladium tonically (conntly) inhibits actions through persistent GABA activity. If these neurons are inhibited, it releases actions form this inhibition. Inhibiting an inhibitor is a process known as disinhibition.
Direct Pathway
The pathway of the basal ganglia by which actions are initiated. An excitatory neuron contacts the striatum → inhibitory striatal neurons contact pallidal neuron → the normally active pallidal neuron is inhibited → this disinhibition leads to the action being performed. This pathway is impaired in Parkinson’s Disease leading to a lack of movement.
Indirect Pathway
The pathway of the basal ganglia responsible for suppressing actions through excitation of pallidal neurons. This is important for the performance of only a single action at once. Damage to this pathway leads to excessive movements such as those in Huntington’s Disease.
Operational Learning
Actions that lead to a positive outcome are preferred by the basal ganglia, the opposite occurs in actions that lead to a negative outcome.
Dopamine
In the basal ganglia, this neurotransmitter promotes craving, and is responsible for facilitating basal ganglia action pathways that result in a positive outcome. Interestingly, this only works if the positive outcome occurs very quickly after the action. This neurotransmitter also acts like the motor oil for movement, promoting movement initiation and smoothness by facilitating the direct pathway. It is also the neurotransmitter that is reduced in Parkinson’s Disease.
Chunking
Combining multiple individual movements into a single consolidated action (example: scanning faces, brushing your teeth, driving, etc). This makes actions much faster and allows you to not focus on each individual movement, however, one disadvantage is that the action is inflexible.
Habit
Chunked actions that are done regardless of outcome (ex: drug abuse).
Parkinson’s Disease
A disease whose primary symptom is a reduction in movement, primarily the slowness of movement and the inability to initiate movement. Symptoms develop once 90% of dopaminergic neurons in the substantia nigra die. Chunked actions are hugely impacted, and chunked actions must be deconstructed to individual movements in order to be performed.
