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1 Basal Ganglia module (next slide). 2 Basal Ganglia menu Basal Ganglia Overview of Basal Ganglia structure Basal Ganglia circuitry (the Striato-Pallido-Thalamic.

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Presentation on theme: "1 Basal Ganglia module (next slide). 2 Basal Ganglia menu Basal Ganglia Overview of Basal Ganglia structure Basal Ganglia circuitry (the Striato-Pallido-Thalamic."— Presentation transcript:

1 1 Basal Ganglia module (next slide)

2 2 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 Select a blue button to move to that topic (next slide)(previous slide)(select this button to return to this slide)

3 3 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)

4 4 overview Extrapyramidal 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 #1 #2a #2b

5 5 Initiate 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. Play Movie (return…)

6 6 Stereotypic 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. (return…) Play Movie

7 7 Stereotypic 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? (return…) Play Movie

8 8 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

9 9

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11 11 Basal Ganglia menu

12 12 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)

13 13 circuitry Neural circuits of the Basal Ganglia Cortex Caudate Putamen The basal ganglia form an internal motor circuit …

14 14 The cortex receives motor planning information, then passes that information to the caudate & putamen, which govern timing of events

15 15 The information then is passed to the globus pallidus …

16 16... which helps govern movement magnitude, and then passes this basal ganglia output to thalamus nuclei

17 17 The thalamus combines information from the basal ganglia and the cerebellum, then sends it to the motor cortex Basal Ganglia menu

18 18 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)

19 19 Input modulation Modulation of input to the Basal Ganglia The caudate & putamen receive input from the cortex, and …

20 20 … from the thalamus.

21 21 The substantia nigra also modulates input to the basal ganglia.

22 22 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.

23 23 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 24Basal 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.

25 25 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)

26 Output modulation 26 Modulation of output from the Basal Ganglia - part 1 1) The putamen provides processed information to the globus pallidus.

27 27 - part 1 In addition to modulating input to the basal ganglia, the substantia nigra also modulates the output.

28 28 - part 1 The substantia nigra, in turn, has many connections.

29 29 - part 2 2) The subthalamus plays a role in modulating output from the basal ganglia

30 30 Basal Ganglia menu - part 2 Deterioration of the subthalamus results in the ballisms, or explosive movements occurring periodically, that characterize Huntington’s disease.

31 31 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)

32 32 Basal Ganglia menu Summary

33 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)

34 34 Basal Ganglia clinical signs Basal Ganglia menu Parkinson’s disease resting tremor poverty of movement bradykinesia stooped posture cogwheel rigidity masked face Chorea Choreaform movements.. Tics Ballisms #1 #2 #3 #4 #5 #6 #9 #8 #7 #10a Clinical signs related to Basal Ganglia dysfunction Select a blue button to view the video #10b (YouTube’s website also can be a good source of example videos…)

35 35 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! Play Movie

36 36 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. Play Movie

37 37 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. Play Movie

38 38 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. Play Movie

39 39 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...” Play Movie

40 40 Masked facial expression Clinical signs menu “The Phantom of the Opera” Warner Brothers, 2004 Gerard Butler as the Phantom 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!

41 41 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. Play Movie

42 42 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). Play Movie

43 43 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. Play Movie

44 44 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. Play Movie

45 45 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. Play Movie

46 46 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)

47 47 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 the nervous system Effects of Drugs on the nervous 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.

48 48 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 Play Movie

49 49 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 Play Movie

50 50 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. Play Movie

51 51 Basal Ganglia menu That ends the Basal Ganglia tutorial!


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