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basal-ganglia.md
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@@ -15,17 +15,17 @@
Note:
- also with the non-motor loops (limbic system class):
* Learning, reward mechanisms
* Response-outcome associations
* Stimulus-response associations
* Modulate the initiation, termination, amplitude, and selection of movement
* But basal ganglia also has varied non-motor roles:
- also with the non-motor loops (limbic system class):
- involved in learning, reward mechanisms
* Response-outcome associations
* Stimulus-response associations
- and also non-motor prefrontal cortex loops to help in selection of conscious goals, decisions
[http://www.youtube.com/watch?v=Td4QGHNJ8Q0](http://www.youtube.com/watch?v=Td4QGHNJ8Q0)
* Modulate the initiation, termination, amplitude, and selection of movement
*and selection of movement*
*Used in dopamine circuits*
--
@@ -43,7 +43,7 @@ Today we will begin our examination of the pathways in the nervous system that m
* Anatomical connectivity
* Function– modulation through disinhibition
* Neuromodulators– dopamine
* Neurotransmitters– dopamine, GABA, glutamate
* Diseases of the basal ganglia
@@ -86,6 +86,18 @@ Note:
Note:
mammillary body
: part of diencephalon, at junction with hypothalamus
: part of limbic system
: location at anterior end of the fornix
: relay from amygdala and hippocamus to thalamus by mamillo-thalamic tract
: role in recall of episodic memories
basal forebrain nuclei
: major source of acetylcholine input to cerebral cortex
: roles in attention, wakefulness, REM sleep
---
## Anatomy of the basal ganglia: caudate and putamen
@@ -95,9 +107,9 @@ Note:
Note:
Main inputs: Striatum– caudate and putamen
Main input structures of basal ganglia system: Striatum– caudate and putamen
Main outputs of basal ganglia system include: Globus pallidus interna (thalamus) and substantia nigra pars reticulata (superior colliculus, eye movements)
Main output structures of basal ganglia system: Globus pallidus interna (projects to thalamus) and substantia nigra pars reticulata (projects to superior colliculus; eye movements)
Intermediate nuclei in the basal ganglia system: Globus pallidus externa, STN, and substantia nigra pars compacta
@@ -120,9 +132,6 @@ Note:
Kreitzer Ann Rev Neurosci 2009
*Inputs from cortical, thalamic, and brainstem structures?*
Medium spiny neuron in the corpus striatum
TODO: new image
@@ -134,10 +143,12 @@ TODO: new image
* Caudate receives cortical projections primarily from multimodal association cortices and motor areas from frontal lobe that control eye movements
* Putamen receives input from the primary and secondary somatic sensory cortex and extrastriate visual cortex in occipital and temporal lobes, premotor and motor cortex, and auditory association areas in temporal lobe
* These inputs are excitatory, glutamatergic synapses
* Each spiny neuron can get synapses from lots of different cortical neurons. Each cortical neuron synapses onto a few MSNs
* Each medium spiny neuron can receive input from lots of different cortical neurons
Note:
Each cortical neuron synapses onto more than one MSN
---
@@ -194,23 +205,25 @@ Note:
<div style="font-size:0.8em">
<div></div>
* Substantia nigra pars reticulata (SNr) neurons project to upper motor neurons in the superior colliculus that command eye movements without going to the thalamus
* **Globus pallidus and pars reticulata neurons are GABAergic**. Unlike MSNs they have high levels of spontaneous activity– they are tonically active
* Thus the output from the basal ganglia is normally inhibitory-- tonic inhibition
* When MSNs fire (in anticipation of movement) this inhibits the inhibition (**disinhibition**) and allows upper motor neurons to send commands to local circuit and lower motor neurons that initiate movement
* When MSNs fire (in anticipation of movement) this inhibits the inhibition (**disinhibition**) and allows upper motor neurons (in cortex and superior colliculus) to send commands to local circuit and lower motor neurons that initiate movement
* Called the direct pathway
</div>
Note:
* Substantia nigra pars reticulata (SNr) neurons project to upper motor neurons in the superior colliculus that command eye movements without going to the thalamus
---
## Direct pathway of outputs from the basal ganglia
<figure><img src="figs/Neuroscience5e-Fig-18.04-2R_cc3e2e7.jpg" height="400px"><figcaption>Neuroscience 5e Fig. 18.4</figcaption></figure>
<figure><figcaption>sign shows normal effect (excite or inhibit) at that synapse</figcaption><img src="figs/Neuroscience5e-Fig-18.04-2R_cc3e2e7.jpg" height="400px"><figcaption>Neuroscience 5e Fig. 18.4</figcaption></figure>
*Remember that caudate/putamen medium spiny neurons are usually not active*
Note:
@@ -281,18 +294,20 @@ Overall inhibitory. Serves to modulate the disinihibitory actions of the direct
---
## Center–surround functional organization of the direct and indirect pathways
## 'Center–surround' functional organization of the direct and indirect pathways
<figure><img src="figs/Neuroscience5e-Fig-18.08-0_909067a.jpg" height="400px"><figcaption>Neuroscience 5e Fig. 18.8</figcaption></figure>
Note:
think center-surround receptive fields for luminance contrast in retinal ganglion cells mediated by synaptic interactions between photoreceptors, bipolar cells, and horizontal cells in the outer plexiform layer.
Importantly, there is more spatially discrete connectivity in the converging input from MSNs onto selective patches of microcircuits in the GPi for the direct pathway. For the indirect pathway, the input is much broader from MSNs onto patches of microcircuits in the GPi-->STN-->GPe. Results in greater upper motor neuron excitation in center of microcircuit (channel of information) due to the direct pathway overriding a diffuse broader inhibition for competing surround circuits (different motor programs for example) from the indirect pathway.
think about center-surround receptive fields for luminance contrast in retinal ganglion cells mediated by synaptic interactions between photoreceptors, bipolar cells, and horizontal cells in the outer plexiform layer.
-difference of Gaussians is a feature enhancement algorithm
-mexican hat distribution (shaped like a sombrero)
-'mexican hat' distribution (shaped like a sombrero) (normal distribution with a postive central tendancy and negative side saddles)
-multidimensional generalization of this wavelet is called the Laplacian of Gaussian function
@@ -300,7 +315,7 @@ think center-surround receptive fields for luminance contrast in retinal ganglio
[-automatic scale selection in computer vision applications; see Laplacian of Gaussian https://en.wikipedia.org/wiki/Mexican_hat_wavelet](https://en.wikipedia.org/wiki/Mexican_hat_wavelet)
Attentional field has a Mexican hat distribution
Attentional field has a 'Mexican hat' distribution:
http://www.sciencedirect.com/science/article/pii/S0042698904005735
@@ -578,15 +593,13 @@ Note:
15-34 cytosine-adenine-guanine (CAG) DNA repeats normally, 42-66 in Huntingtin's disease resulting in an unstable triplet repeat in coding region of gene. Polyglutamine
--
## The huntingtin protein has expanded glutamine repeats in the diseased state
<!--
The huntingtin protein has expanded glutamine repeats in the diseased state
<div><img src="figs/image3_40b3e0b.png" height="400px"><figcaption></figcaption></div>
Note:
TODO: img src unknown
-->
---