Physiology 3120 Lecture Notes - Lecture 5: Thalamus, Tourette Syndrome, Mptp

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Physiology 3120
Dr. Hore
Basal Ganglia
- Another structure that helps in the programming of movements and projects to the motor
cortex
- Basal ganglia projects to the supplementary motor area which projects to the motor cortex
- Supplementary motor area is on the medial aspect of the hemisphere and goes down along the
surface of the medial (aka mesial) wall of the hemisphere
- Important thing: it projects to the motor cortex
o Note: premotor cortex and parietal cortex also project to the motor cortex
- The motor cortex is on the precentral gyrus infront of the central sulcus
- Three areas of cortex which interact with motor cortex
- Structures of the basal ganglia: caudate nucleus and putamen (together known as striatum or
the neostriatum)
- There are 2 structures in the globus pallidus: external and internal segment
- Subthalamic nucleus and the substantia nigra
- If you try to make a connection diagram of neural connections bw these various structures:
- You have to know only the 6 facts about this diagram don’t have to know this entire diagram
- Before they thought that the function of the basal ganglia was only to control movement - bc ppl
with lesions in the basal ganglia often had severe motor disorders (ex: Parkinsons/huntingtons)
- Now we know this is not true it does control motor functions but it also controls other
functions this is presented in the diagram
1. 4 loops
o there are 4 loops throughout the basal ganglia
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o the original loop is a motor loop
if you started at areas of the cerebral cortex, and take the motor loop, so there
would be areas of the motor cortex that would project without the
neostriatum (caudate/putamen) through the pathways and then back into the
motor and supplementary motor area parts of the cerebral cortex
so it starts in the supplementary motor areas in the motor cortex, goes
through the basal ganglia and back to these same areas
o there is an adjacent loop that controls the ocular motor system
so voluntary saccades can be generated from the cerebral cortex to some
degree
there are areas in the cerebral cortex, just in front of the motor cortex called
the frontal eye fields which then come in through the caudate/putamen down
the pathways and go back to ocular motor areas int eh motor cortex
o there is a limbic loop
these are the old reptilian areas in the brain that we inherited from reptiles
the limbic cortex is normally associated with emotion
the limbic cortex is said to have a loop through the basal ganglia down to the
internal segment of the globus pallidus across to the external segment of the
subthalamic nucleus and then back to the a limbic areas of the cortex
o there is a cognitive prefrontal cortex loop
does the same thing as limbic loop but back to the cognitive prefrontal cortex
2. 2 inputs to Caudate/Putamen
o caudate/putamen is the area which receives incoming information
o inputs come from widespread areas of the cerebral cortex (motor, oculomotor, limbic,
cognitive) and the substantia nigra pars compacta
o the substantia nigra pars compacta sends dopamine
o the caudate and putamen have different dopamine receptors (Type 1 dopamine
receptor and type 2 dopamine receptor one of them is excitatory and the other is
inhibitory)
o this is the major pathway associated with parkinsons disease
3. Major transmitters:
o Glutamate
comes from the cortical connections
usually excitatory projects with an excitatory synapse with the
caudate/putamen
o Dopamine
Very important in the basal ganglia
o Ach
Inihibitory interneuron neurotransmitter in the caudate/putamen
o Neurologists balance Ach/Dopamine
The disorder in parkinsons disease is lack of dopamine and so if you give
LDopa that will get het dopamine levels back up again but you don’t want
them to get too high
And so there is a balance bw dopamine and ACh which is optimal for
parkinsonian patients
4. Direct/Indirect Pathways
o If you have some processing going on in the caudate/putamen, the output of that goes
directly to the internal segment of the globus pallidus via a direct pathway but it also
gets it indirectly by connections through the external globus pallidus and back to the
internal segment or then via the subthalamis nucleus and then back to the internal
globus pallidus
o So it gets back either directly or indirectly to the internal globus pallidus
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Document Summary

Another structure that helps in the programming of movements and projects to the motor cortex. Basal ganglia projects to the supplementary motor area which projects to the motor cortex. Supplementary motor area is on the medial aspect of the hemisphere and goes down along the surface of the medial (aka mesial) wall of the hemisphere. Important thing: it projects to the motor cortex: note: premotor cortex and parietal cortex also project to the motor cortex. The motor cortex is on the precentral gyrus infront of the central sulcus. Three areas of cortex which interact with motor cortex. Structures of the basal ganglia: caudate nucleus and putamen (together known as striatum or the neostriatum) There are 2 structures in the globus pallidus: external and internal segment. If you try to make a connection diagram of neural connections bw these various structures:

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