Basal Nuclei- added paths Flashcards
What structure is similar in structure and function to GPi?
substantia nigra pars reticulata
What are the fibers called from the striatum to the pars reticulata?
striatonigral fibers
What does the pars reticulata inhibit?
the VA/VL thalamus with GAGAergic inhibitory neurons
What do neurons of the pars compacta release?
Dopamine (DA)
What are the two actions that dopamine produces on the striatum?
- inhibition via D2 receptors of the indirect pathway
2. excitation via D1 receptors on the striatal neurons of the direct pathway
With both actions of the SNc, what does it promote?
thalamic excitation.
neurons of the SNc are inhibited by ______, but excited by _______
- striatal GABAergic input
- cholinergic input from pedunculo-pontine nucleus (PPN)
What is the other role in movement that the PPN has other than facilitating disinhibition of the thalamus?
it is one of the brainstem nuclei that contributes to the pontine reticulospinal tract (therefore it can produce descending excitation of the spinal LMN)
What are the four parallel channels of functions involving the basal nuclei?
- Motor channel
- Oculomotor Channel
- Prefrontal channel
- Limbic channel
What is the motor loop associated with?
regulation of voluntary movement
What does the motor loop arise from?
supplementary motor cortex and other cortical areas
What does the motor loop regulate?
VA/VL thalami and motor cortex excitability via connections through the putamen and the GPi(direct) and the GPe and subthalamus (indirect_
SMA generates readiness that precedes what movements?
volitional, self paces, voluntary
Functions associated with the motor channel include?
- initiated by the intention to act
- preparation, organization and execution of action
- endogenous generation of responses when environmental stimuli fail to provoke responses
What is the oculomotor channel associated with?
regulation of eye movements
What does the oculomotor channel begin in?
the SMA & posterior parietal cortex
What does the oculomotor channel project via?
caudate nucleus, GPi and SNr
What does the oculomotor channel regulate?
excitability of VA and DM thalamic nuclei.
What are the cortical targets (output) of the oculomotor channel?
prefrontal areas in the vicinity of the frontal eye fields
What are the oculomotor channel functions?
- higher order control of eye movements
- orientation of eyes toward specific objects in the environment
- implicated in visual exploration and visual learning
What is the prefrontal channel associated with?
cognition
Where is input from in the prefrontal channel?
dorsolateral prefrontal cortex
from the dorsolateral prefrontal cortex, where does the prefrontal channel go?
the head of the caudate
In the prefrontal channel, what does the caudate influence?
the GPi and SNr to regulate excitability of the VA and DM thalamic nuclei (then the nuclei project to the prefrontal cortex)
Functions of the prefrontal channel
- processing information about fairness of decision making
- trusting in “fair” decisions and those who make them
- ‘altruistic punishment’- the desire to punish violations of social norms even when we have not been personally wronged
- regulation of “worry”
What is the limbic channel associated with?
regulation of emotions and motivational drives
Where does input of the limbic channel come from?
temporal cortex, hippocampus and amygdyla
What are the inputs of the limbic channel via?
nucleus accumbens, ventral putamen, and caudate
What are the input locations of limbic channel connected to for output?
GPi
where does the output of the limbic channel go to?
DM of thalamus
of the limbic channel, what does the DM project to?
anterior cingulate cortex and orbitofrontal cortex
Limbic channel functions include?
- evaluation of personal actions and environmental resources
- social, behavioral and affective self regulation
- might be channel implicated in excessive gambling seen in Parkinson’s pts on L-Dopa and dopamine agonists
