D1R photo-activation in neurons of the dorsomedial striatum combined with two-photon imaging of activity in L5 cortico-striatal projection neurons. Photo: Nuria Vendrell-Llopis, Jonathan Read, University of California, Berkeley
Dopamine can modify already set patterns in our brain thus leading to a change of behavior. This neurotransmitter is doing so by activation a certain receptor in a group of brain cells located near cortex.
Why medicine may be seen as an art? Because its major trick is to asses what’s missing and enable to fix it. In a needed quantity in the case of drugs. In German, the word doctor is ,,Arzt” with the pronunciation similar to English ,,art”. Having in mind, roots of many/Indoeuropean languages come from the same tree, it could be possible that during spreading human groups which were acquiring new lands, expression of some words have changed. But to regain the main plot, why this is dopamine so important for our minds and why it has the potential to substantially change them?
One signal to another
In the newly published study in journal ,,Neuron”, scientists of University of California, Berkely claim, timed dopamine signals underlie reinforcement learning, favoring neural activity patterns that drive behaviors with positive outcomes. And, in opposite, its missing may be harmful for brain. This may be why this neurotransmitter has been, among some other, named a happiness hormone. Neurotransmitter is a sort of protein which is capable to change electric impulse flowing from one brain cell to another for a chemical signal. The effect also depends on proteins – receptors taking the signal, in the membrane of the other cell. The whole process is taking place in synapse which is a place where the longer part of a brain cell (neuron) connects the next cell and acts as a link between them.
American scientists write that in general, dopamine activates five receptors and the process occurs in striatum, a structure belonging to cerembrum which includes also the front-head cortex. These five receptors are differentially expressed in striatal neurons. Moreover, the role of specific dopamine receptors in reinforcement is poorly understood. But, as state scientists, their study on mice proves that activation of specified one may lead to the reinforcement. Applied technique with particular photo-tracker showed the receptor D1R activation is sufficient to change the firing pattern in a group of neurons located in a specific part of stratum. And, what is more, it reinforces it.
The reinforcement is cumulative and time dependent, with an optimal effect when D1R activation follows the selected neural pattern after a short interval,
says Nuria Vendrell-Llopis, University of California, Berkeley
She underlines, that the study results show that D1R activation in striatal neurons can selectively reinforce cortical activity patterns, independent of a behavioral outcome or a reward, crucially contributing to the fundamental mechanisms that support cognitive functions like learning, memory, and decision-making.
Redirect towards good outcome
Dopamine is thus pivotal to reinforcement learning, as it bridges the gap between actions and their consequences. Without it or with too low volumes we may feel completely lost and unable to undertake daily tasks in our life. And, in opposite, too high expression may lead to hyperactivity what is also not profitable for our cognitive functions. We may be stuck in the past unable to go forward as our set neural patterns can not change due to constant reinforcement of them in our brains. But as dopamine may leave us in this trap, it can also redirect. How is this possible?
Scientists hold that, as is typical of learning associated with reward, our focused D1R activation in dorsal striatal neurons results in cumulative and time-dependent reinforcement. The optimal effect occurs when the activity of the cortical neurons briefly precedes D1R activation. Scientists claim, the results show that, independent of a traditional reward, cortical activity patterns can be selectively reinforced by timed D1R activation in dorsal striatal projection neurons. In other word, dopamine certain volumes may create a window for a change with positive outcome particularly when the final activity of the focused path has been preceded by cortical neurons activity. Does it mean think twice before you undertake any action? Yes and not. Dopamine is therefore the one which enables us the right direction of thinking independent from traditionally obtained reward.
Leave a Reply