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Review: General Control Theory

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Presentation on theme: "Review: General Control Theory"— Presentation transcript:

1 Review: General Control Theory
-Cortex -Basal Ganglia -Cerebellum

2 Review: Primary M. Cortex
Directionality: yellow = one cell’s firing vectors (broad) red = “best” vector No one (1) cell can generate an appropriate directional code! Population Tuning

3 Motor Cortex Topographical Orientation …great question from last time

4 Current Research Topics
Conserved Topographical Organization? (Bizzi E):

5 PreMotor Cortex PreMotor Cortex - Rostral Pre-Central Gyrus
- Activated by cues for well-learned events (monkey)

6 PreMotor Cortex Continued
Lateral PreMotor elements conditional tasks fire before action external cues (in monkey anyway) damage = inability to select appropriate response movements Medial PreMotor elements initiate internally / voluntarily driven motor tasks internal cues damage = reduced spontaneous movements

7 - Somatosensory Cortex
Primary vs. PreMotor Inputs: - Premotor Cortex - Somatosensory Cortex Inputs: - Pre-Frontal Cortex - Areas 5 and 7

8 Review Be familiar with the contribution of each particular anatomical structure / region: Cortex 2 regions discussed Brainstem the 3 nuclei discussed & pathways -Spinal Cord spatial significance / distribution Local Circuitry / MNs / Muscle those properties discussed

9 Basal Ganglia (Group #3)


11 Anatomical Components:
Globus Pallidus Corpus Striatum (striped) caudate nucleus putamen ventral striatum Associated Nuclei substantia nigra subthalamic nuclei *

12 Basal Ganglia Function Direct Pathway: interrupt tonic inhibition
- Active before and during movements Inputs: majority of cortex multiple parallel pathways Output: thalamus, superior colliculus, cortex… “Upper Motoneurons” - High levels of efferent tonic inhibition - GABAergic output Direct Pathway: interrupt tonic inhibition Indirect Pathway: internal loop increases inhibition

13 Basal Ganglia Continued
Cerebral Cortex Corpus Striatum (caudate & putamen) Medium Spiny Neurons Globus Pallidus & Substantia Nigra Upper MNs Medium Spiny Neurons majority of cells in striatum 75,000,000 (!) labeled line occur in patches: striosomes normally not tonic Globus Pallidus 1/100 number of m. spiny neurons 750,000 INTEGRATOR high level tonic output GABAergic Primary pathway back to motor cortex is via internal G. P.

14 Direct Pathway (tonic only)
Normal activity of the direct pathway = hypokinesia

15 Direct Pathway (phasic activation)
Reduced activity of the direct pathway (GP) = hyperkinesia

16 Enhanced activity in the indirect pathway = hypokinesia

17 Parkinson’s Disease damage to Nigrostriatal cells
medium spiny neurons damage to Nigrostriatal cells - increased thalamic inhibition - seldom can coordinate movements bursts of activity

18 Parkinson’s Disease treatments
Must attenuate activity in the Globus Pallidus - l-Dopa (there are several pharmacological treatments) - thalamotomy - pallidotomy

19 Huntington’s Disease sequence is known, protein function is not - yet
medium spiny neurons sequence is known, protein function is not - yet genetic test is available - excessive excitability involuntary movements eventual loss of mental cohesion

20 Huntington’s Disease treatments
Must augment activity in the Globus Pallidus - ACh (acetylcholine) - Striatal tissue implants genetic treatments (?)

21 Cerebellum (Group #4)

22 Cerebellum Anatomical Components: Cerebellar Cortex: - Spinocerebellum
gross movt’s vermis Cerebrocerebellum complex movt’s Vestibulocerebellum posture / balance nodulus flocculus

23 Cerebellum Anatomical Components Cerebellar Deep Nuclei:
continued: Cerebellar Deep Nuclei: (All receive input from the cerebellar cortex – though functionally distinct) Dentate (invaginations) Fastigial Interposed (2) Cerebellar Peduncles Superior efferent pathways Middle afferent pathways Inferior Both afferent & efferent

24 Cerebellum General Function (still not completely understood)
- measure motor error motor learning output to cortex (via thalamus) and vestibular nucleus Modify activity pattern of “Upper MNs” - inputs from: pre-motor, primary motor, primary / secondary somatic, anterior parietal, secondary visual (not primary) behavior modulation inputs: “learning” inferior olive locus coruleus

25  Cerebral Cortex Pontine Nuclei Cerebellar Cortex
[Report what’s happening] Pontine Nuclei [Relay / Process] Cerebellar Cortex [Compute error(?)] Deep Cerebellar Nuclei Thalamus (Cortex) & Vestibular Nucleus [Tell control centers] middle peduncle

26 Cerebellar Cell Types Purkinje Cells: (inhibitory)
If there were a brain of the cerebellum, it would be the Purkinje cells Mossy Fibers: (excitatory) From: - pontine nuclei (via middle peduncle) - other pons / brainstem loci To: - deep cerebellar nuclei - granule cells Granule Cells: (most abundant in brain) From & To: cerebellar cortex… ~unipolar Give rise to: Parallel Fibers: (excitatory) Climbing Fibers: (excitatory) From: - inferior olive To: - Purkinje shaft Local Interneurons: Basket Cells Stellate Cells Golgi Cells (inhibitory) “control the flow of information through the cerebellar cortex”

27 Cerebellar Cell Types Extraordinary branching integrative properties

28 Clinical Implications
Normal Function (to reiterate): Smooth motor functions (reduce error) Coordinate target acquisition Lesion or Degeneration: Loss of smooth movements Rarely stop on target

The ability to successfully complete an organized sequence of movements requires the appropriate coordination of MANY elements. Spatial organization (rubrospinal pathways, spinal signals, cerebellar integration) Temporal organization (cortical planning) Accuracy and uniformity (error measures, sensory integration) Sequencing (spinal circuitry)

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