Action selection Flashcards
What is meant by action selection?
A computational challenge. Motor actions and their organisation into action sequences are achieved by facilitating appropriate motor programmes while inhibiting competing ones.
Action selection is the task of what to do next by doing the right thing at the right time. It requires the assessment of available alternatives, executing those most appropriate, and resolving conflicts among competing goals. (by Seth, Prescott and Bryson)
What brain parts make up Striatum (2)?
Putamen
Caudate Nucleus
Which part of the brain pathway is depicted here?
Basal Ganglia
What is optogenetics?
It is a way to express light-sensitive proteins in targeted neurons.
Fibre-optic cable plus electrodes are implanted in the brain.
The expression of the molecule channelrhodopsin in a specific cell type and upon a light stimulus causes the activation of that neuron.
What is depicted in the picture?
What was discovered?
This is a remarkable experiment which was the first one to prove that the D1 and D2 pathway in the basal ganglia are absolutely intricately involved in action selection, and thus the initiation, maintenance and termination of movements, which is nicely illustrated here.The direct pathway activity facilitates movement, whereas the D2 pathway activity terminates movement
What is depicted here?
What is key finding?
We have action sequences that can be divided into a start, a stop, a sustained activity or an inhibited activity.
Jin & Costa found out is that those two pathways never act in isolation. For a long time, people thought this is an either/or scenario- like in a car, you either go on the accelerator or you go on the brake. That’s not really what’s the case. What Costa and colleagues showed is that they are simultaneously, concomitantly active, which is nicely illustrated in panel b where you see the percentage of activity of the direct SPNs, which are striatal pathway neurons, and iSPN are the indirect SPNs.
Describe concomitant activity.
So somehow, the two pathways work together to manage a directed movement and that makes sense. You can’t turn left and right at the same time. That means, on the one hand, the desired motor programme needs to be facilitated, where the D1 pathway is involved, and the undesired movement needs to be suppressed, which obviously requires D2 activity.
What is dyskinesia?
A disorder where dopamine innervation into the striatum is affected, and people afflicted with dyskinesia engage in uncoordinated movements; that is, some movements are not suppressed, other movements are facilitated, but they are uncoordinated, they are often not voluntarily. So, this is impaired action selection.
When action selection is impaired, and it has to do with the basal ganglia direct and indirect pathway disorders might be:
- Parkinson
- Motor neuron desease
- Frontotemporal dementia
What dysfunctions happens in Parkinson’s disease?
What are the symptoms?
Loss of the nigrostriatal pathway.
Symptoms are tremor, rigidity, and bradykinesia, and very typically, in a progressed stage of Parkinson’s disease, people have problems initiating actions and to maintain them.
What is depicted here?
It illustrates that from the substantia nigra pars compacta, there are very specific nigrostriatal pathways that innervate the putamen and the cordate, which together form the striatum. In Parkinson’s disease, those dopaminergic neurons get lost, which in turn leads to the loss of the nigrostriatal pathway, and there is no more dopaminergic innervation into the striatum.
What is MPTP?
MPTP is a drug that very specifically affects the dopaminergic neurons and inactivates their activity via a complex interaction with complex 1 and the mitochondria.
What behavioural manifestations are in both vertebrate basal ganglia and insect central complex?
What was the main discovery made by Wystrach and colleagues in 2014?
The existence of an internal neural representation of a sensation, (in this case, a visual input in a very specific area of the sensory field).
The main discovery of Seeli and Jayaraman in 2015?
The existence of an internal neural representation of an optical stimulus and the orientation of the animal towards it.
The ellipsoid body ring neurons and especially the central complex are involved in functions of(6):
- higher motor control
- visual short-term memory and place learning
- direction-selective orientation tuning
- landmark orientation and angular path integration
- attention and arousal
- decision-making
These behaviours are controlled by the same neural network, which is involved in the regulation of action selections.
