All about the ganglia (basal, that is) Flashcards
Input areas of the basal ganglia (who receives input?)
Input comes from the __ or the __
Input areas of the basal ganglia are the caudate nucleus and the putamen
Input comes from the cortex or from the thalamus
Output areas of the basal ganglia (i.e. path of signal from input areas)
After processing of input, the output leaves from the globus pallidus internal or it goes to the pars reticularis of the substantia nigra
That goes back up to the thalamus and then to the cortex
Direct vs indirect pathway of BG circuit
Information processed from putamen or caudate nucleus can either go directly into the globus pallidus internal then to the thalamus (see previous slide); DIRECT pathway
OR
It can go into the globus pallidus internal, then to the subthalamic nucleus then to the globus pallidus external, then back to the globus pallidus internal then to the thalamus/cortex; INDIRECT pathway
___ ___ of the substantia nigra – contains dopaminergic neurons that innervate the __ nucleus and the ___; loss of these = Parkinson’s disease.
The subthalamic nucleus also receives direct excitatory input from the ___
Pars compacta
Caudate nucleus and putamen
Cortex
Parallel processing loops (hint: LMAO!!)
location of each loop (e.g. for motor - premotor and supplementary motor areas)
Motor (premotor, supplementary motor area)
Occulomotor (frontal eye field, saccades)
Association (prefrontal cortex)
Limbic (cingulate gyrus)
Cells in the caudate nucleus and putamen (what are they called, what do they do? there’s 2 populations; hint: something about spines)
Within the caudate nucleus and the putamen, most of the neurons are Medium spiny neurons (aka GABAergic/inhibitory projection neurons); they start from the caudate/putamen and project long distances
The other neurons are aspiny neurons: interneurons; can be cholinergic or send other signals; their modulatory role is not well understood
The cells in the globus pallidus internal and the substantia nigra reticularis
GABAergic projection neurons similar to those in caudate nucleus and putamen
At baseline:
The cells in the CN and P are firing at a very ___ rate, while those in the GP and SN are firing at a ___ rate
After processing of input:
As signal leaves input area, it leaves at ___ activity, then as it leaves from the output areas, it leaves at ___ activity
low
high
high
low
Cortical input is ___
So cortical input acting on the GABAergic neurons is going to ___ their INHIBITORY activity on the output neurons, so the output is (more/less)___ inhibitory, and the final effect going from the thalamus back to the cortex is ___
Cortical input is stimulatory
So cortical input acting on the GABAergic neurons is going to INCREASE their INHIBITORY activity on the output neurons, so the output is LESS inhibitory, and the final effect is disinhibition (i.e. the signal that’s sent to the cortex is a stimulatory signal because the inhibition on the thalamus has been removed)
Indirect pathway:
Input comes from cortex (stimulatory) and acts on the GABAergic neurons in the CN/P. From there, an increasingly ___ signal is sent to the GABAergic neurons in the globus pallidus external, which ___ inhibition to the neurons in the subthalamic nucleus, so the signal from there is ___. That then ___ the inhibitory signal to the thalamus, and from there to the cortex, the signal is ___
(essentially, using the indirect pathway results in more ___)
Input comes from cortex (stimulatory) and acts on the GABAergic neurons in the CN/P. From there, an increasingly inhibitory signal is sent to the GABAergic neurons in the globus pallidus external, which decreases inhibition to the neurons in the subthalamic nucleus, so the signal from there is stimulatory. That then increases the inhibitory signal to the thalamus, and from there to the cortex, the signal is inhibitory
(essentially, using the indirect pathway results in more inhibition, NOT DISINHIBITION)
Role of basal ganglia in gating motor activity:
T/F: disinhibition of thalamocortical pathway by the BG cause motor activity
T/F: The disinhibitory signal from the BG to the thalamocortical pathway tells the motor system which neurons should discharge, as well as how strongly they should discharge.
Disinhibition (direct pathway) by basal ganglia basically brings us closer to motor activity but doesn’t actually cause motor activity (indirect pathway has opposite effects)
Basal ganglia also enable certain movements and control their sequence but they don’t cause them (so basically the signal from the cortex is the cause of things, the BG are just middle men)
The disinhibitory signal from the BG to the thalamo-cortical pathway tells the motor system which neurons should discharge rather than how strongly they should discharge.
Function of indirect pathway:
(why is it contrast-enhancing, what else does it do?)
The indirect pathway is contrast-enhancing in that all other pathways surrounding the direct pathway are shutdown so that the cortex knows to receive signals only pathway? (I think)
The indirect pathway also dampens the activity in the direct pathway
Role of dopamine in indirect vs direct pathway:
dopamine will always cause an ___in activity, regardless of which path its acting on
The Dopaminergic neurons in the indirect pathway in the CN and P are inhibitory; they express the __receptor, which when activated is inhibitory
The dopaminergic neurons in the direct pathway are ___ b/c they express the D1 receptor which when activated is excitatory
The Dopaminergic neurons in the indirect pathway in the CN and P are inhibitory; they express the D2 receptor, which when activated is inhibitory
The dopaminergic neurons in the direct pathway are excitatory b/c they express the D1 receptor which when activated is excitatory
(dopamine will always cause an increase in activity, regardless of which path its acting on)
Role of glutamate in direct vs indirect pathway
Glutamate does the opposite; in the direct pathway, it causes stimulation but in the indirect pathway it causes a decrease in stimulation/inhibition
The neurons of the globus pallidus are involved in ___
Postural adjustments
