basal ganglia module
DESCRIPTION
Basal Ganglia module. (next slide). Basal Ganglia menu. Basal Ganglia Overview of Basal Ganglia structure Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop) Modulation of inputs to the Basal Ganglia Modulation of outputs from the Basal Ganglia - PowerPoint PPT PresentationTRANSCRIPT
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Basal Ganglia menu
Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
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overviewExtrapyramidal Motor System
The basal ganglia perform two functions:
1. Initiate movements
1. Regulate stereotypic movements
Overview of the Basal Ganglia
Select a button to view that example
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#2a
#2b
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Initiate movementsInitiate movements
The basal ganglia govern the initiation changes in motor behavior - meaning both starting AND stopping of motor actions. Sipping from a cup requires proper initiation or stopping of multiple, sequential actions.
PlayMovie
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Stereotypic movements #1Stereotypic movements #1
Stereotyped movements, like other habits, often are context dependent. The cerebellum governs the movement itself, but the initiation of the motor pattern in context is governed by the basal ganglia. The basal ganglia have been implicated in the expression of obsessive-compulsive disorders.
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PlayMovie
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Stereotypic movements #2Stereotypic movements #2
Not all stereotyped behaviors are rhythmic, and the motor pattern can be difficult to halt once it has begun. Have you ever tried to stifle a yawn?
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PlayMovie
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This cartoon represents a horizontal slice through the brain at the level of the thalamus.It is a midline view from above, with anterior at the top of the screen and posterior at the bottom of the screen.
Basal ganglia structures
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
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circuitry
Neural circuits of the Basal Ganglia
CortexCaudate
Putamen
The basal ganglia form an internal motor circuit …
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The cortex receives motor planning information, then passes that information to the caudate & putamen, which govern timing of events
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... which helps govern movement magnitude, and then passes this basal ganglia output to thalamus nuclei
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The thalamus combines information from the basal ganglia and the cerebellum, then sends it to the motor cortex
Basal Ganglia menu
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
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Input modulation
Modulation of input to the Basal Ganglia
The caudate & putamen receive input from the cortex, and …
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Reciprocal connections with the caudate & putamen allow exitatory inputs from the substantia nigra to modulate the amount and type of output sent to the globus pallidus. Dopamine is the neurotransmitter used by these substantia nigra pathways.
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When the substantia nigra isn’t working properly, input to the basal ganglia isn’t modulated properly, and the globus pallidus receive progressvely less information. Without this information, the initiation of movement (i.e., timing) message is less effective and the person’s movements progressively become slower (i.e., bradykinesia).
24 Basal Ganglia menu
Parkinson’s disease is related to a deterioration of the substantia nigra and globus pallidus, and is characterized by resting tremors and bradykinesia.
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
Output modulation
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Modulation of output from the Basal Ganglia
- part 1- part 1
1) The putamen provides processed information to the globus pallidus.
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- part 1- part 1
In addition to modulating input to the basal ganglia, the substantia nigra also modulates the output.
30 Basal Ganglia menu
- part 2- part 2
Deterioration of the subthalamus results in the ballisms, or explosive movements occurring periodically, that characterize Huntington’s disease.
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
33
Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System
(next)
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Basal Ganglia clinical signs
Basal Ganglia menu
Parkinson’s diseaseresting tremor . . . . . . . . . .poverty of movement . . . . . .bradykinesia . . . . . . . . . . .stooped posture . . . . . . . . .cogwheel rigidity . . . . . . . . .masked face . . . . . . . . . . .
Chorea . . . . . . . . . . .Choreaform movements . . Tics . . . . . . . . . . . . .Ballisms . . . . . . . . . . .
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#10a
Clinical signs related toBasal Ganglia dysfunction
Select a blue button to view
the video
#10b
(YouTube’s website also can be a good source of example videos…)
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Resting tremor
Clinical signs menu
An hallmark feature of Parkinson’s disease is the resting tremor - involuntary, oscillating movements at rest, often of the hands or head and neck.
It is not a resting tremor if it occurs during execution of a movement!
PlayMovie
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Poverty of movement
Clinical signs menu
Limited or no movement - often described by the person as becoming “stuck” in position - also is characteristic of Parkinson’s disease. Remember that the basal ganglia are responsible for initiating a change in movement patterns. Here, the individual is attempting to rise from a chair - a complex motor sequence where timing of the component movements is critical.
PlayMovie
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Bradykinesia
Clinical signs menu
“Slowed movement” is another feature of Parkinson’s disease, and is particularly noticeable with walking - a motor behavior where the center of gravity shifts forward, and placing each foot forward alternately is what keeps you from falling. Slowed movements allows the center of gravity to shift too far forward, too rapidly.
PlayMovie
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Stooped posture
Clinical signs menu
A biomechanical feature of many disorders, but characteristic of Parkinson’s disease when seen in combination with other symptoms. Here, note the resting tremor, bradykinesia, and - despite the poor quality image - a masked facial expression.
PlayMovie
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Cogwheel rigidity
Clinical signs menu
An animation of the concept, meant to illustrate the lack of smooth movements at the joint. The feeling is similar to that of a cogwheel:
“click - stop - click - stop...”
PlayMovie
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Masked facial expression
Clinical signs menu
“Th
e P
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ra”
Wa
rne
r B
roth
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, 2
00
4G
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Conveying emotion through facial expression requires initiation of motor behavior. Without these behaviors, the person may have a “masked” facial expression. Be aware, however, that emotional capacity is undiminished even if the emotion can’t be expressed!
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Chorea
Clinical signs menu
Huntington’s disease and other choreas typically are disorders in modulation of the output from the basal ganglia. Ongoing, smoothly flowing movements are typical - but the constant movement consumes calories rapidly. The movements do not occur during sleep.
A different form of chorea (now called Sydenham’s chorea) was once termed St. Vitus’ dance due to the frenzied limb movements and contorted facial expressions. This form of chorea can appear after rheumatic fever, but also may co-occur with obsessive-compulsive disorder - which also is associated with basal ganglia dysfunction.
PlayMovie
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Choreaform movements
Clinical signs menu
Other intrusive movements may appear similar to those of Huntington’s chorea and Sydenham’s chorea, but do not arise from the same causes (genetic source or bacterial infection). These movements are termed “choreaform” and they can be significant barrier to function. This individual has been asked to touch her nose with each index. Unlike true choreas, her impairment primarily is unilateral (right side).
PlayMovie
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Tics
Clinical signs menu
A tic is a sudden, repetitive, stereotyped, nonrhythmic, involuntary movement (motor tic) or sound (phonic tic) that involves discrete groups of muscles. Tics can be invisible to the observer - such as abdominal tensing or toe crunching. Tics must be distinguished from symptoms of other disorders, such as choreas, autism, seizures, or obsessive-compulsive disorder.
PlayMovie
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Ballisms #1
Clinical signs menu
Ballisms are sudden, explosive, large-amplitude, flinging motions of the limbs. If confined to one limb or one side of the body, they are termed “hemiballisms.” This motor intrusion may cause postural instability and lead to falls and cause problems with everyday activities (such as eating, cooking, or dressing), but frequently also is a significant social barrier.
PlayMovie
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Ballisms #2
Clinical signs menu
Caused by a lesion of the contralateral subthalamic nucleus or its connections, ballisms may be less severe, more severe, or may progressively become worse over time. The severity may relate to the size or to the frequency of the ballism. This individual has been asked to touch his nose with his left index finger.
PlayMovie
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Basal Ganglia
Overview of Basal Ganglia structure
Basal Ganglia circuitry (the Striato-Pallido-Thalamic loop)
Modulation of inputs to the Basal Ganglia
Modulation of outputs from the Basal Ganglia
Summary of extrapyramidal circuitry
Clinical signs related to the Basal Ganglia
Effects of drugs on the Nervous System(next)
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Drug effects
Basal Ganglia menu
Tardive dyskinesia- a side effect of many anti-psychotic drugs
L-dopa therapy- side effects related to treatment
of Parkinson’s disease
Catatonic rigidity- side effect of Phenothiazine, an
anti-psychotic medication
video #2
video #3
video #1
Click on a button to view the video
Effects of Drugs on thenervous system
Effects of Drugs on thenervous system
Drug side effects may occur when a drug is introduced into a system that already is malfunctioning, or when the drug acts on brain regions other than just the intended target area.
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Tardive dyskinesia
Drug Effects menu
Tardive dyskinesia occurs as a result of long-term use of certain anti-psychotic medications, such as those used in the treatment of schizophrenia. Characterized by periodic involuntary movements (tongue & mouth movements in particular), tardive dyskinesia is addressed by halting the use of that particular drug - but the damage is done, and the presence of these intrusive movements cannot be reversed.
Tardive dyskinesia
PlayMovie
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L-dopa
Drug Effects menu
L-dopa is used to treat Parkinson’s disease. While very effective in the earlier stages of the disorder, symptoms continue to develop and larger doses of drug are required. Eventually the side effects if high doses of L-dopa will impair function and diminish quality of life. This is an example of a drug regime that allows the symptoms of a disorder to be managed - at least for a time - but is NOT a cure for the disorder. This example also shows three stages of drug action - prior to treatment (poverty of movement; resting tremor; stooped posture; shuffling gait), soon after administration (intrusive movements), and later on - during the therapeutic phase of the drug’s action.
L-dopa therapy
PlayMovie
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Catatonic rigidity
Drug Effects menu
Catatonic rigidity occurs as a side effect after long-term use of certain anti-seizure medications. Use of modern medications has limited the incidence of this iatrogenic disorder.
PlayMovie