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Dopamine promotes cognitive effort by biasing the benefits versus costs of cognitive work

dopamine adhd motivation

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#1 gamesguru

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Posted 11 June 2020 - 05:32 PM


Quoted from https://science.scie...t/367/6484/1362

 

Dopamine promotes cognitive effort by biasing the benefits versus costs of cognitive work

Responsible use of psychostimulants

Psychostimulants have a place in the therapy of attentional disorders. However, they are also widely used off-label to enhance cognitive performance, and their mechanisms of action remain elusive. Westbrook et al. studied the effects of these drugs and concurrently measured striatal dopamine synthesis capacity in young, healthy participants (see the Perspective by Janes). They administered a placebo, methylphenidate (a dopamine and noradrenaline reuptake blocker), and sulpiride (a selective D2 receptor antagonist) while participants made explicit cost-benefit decisions about whether to engage in cognitive effort. Higher dopamine synthesis capacity in the caudate nucleus was associated with greater willingness to allocate cognitive effort. In addition, methylphenidate and sulpiride increased subjective values and motivation to work specifically for people with low dopamine synthesis capacity. Cognition-enhancing drugs may thus act at the motivational level rather than directly boosting cognition per se.

Science, this issue p. 1362; see also p. 1300

Abstract

Stimulants such as methylphenidate are increasingly used for cognitive enhancement but precise mechanisms are unknown. We found that methylphenidate boosts willingness to expend cognitive effort by altering the benefit-to-cost ratio of cognitive work. Willingness to expend effort was greater for participants with higher striatal dopamine synthesis capacity, whereas methylphenidate and sulpiride, a selective D2 receptor antagonist, increased cognitive motivation more for participants with lower synthesis capacity. A sequential sampling model informed by momentary gaze revealed that decisions to expend effort are related to amplification of benefit-versus-cost information attended early in the decision process, whereas the effect of benefits is strengthened with higher synthesis capacity and by methylphenidate. These findings demonstrate that methylphenidate boosts the perceived benefits versus costs of cognitive effort by modulating striatal dopamine signaling.

 

 

I wouldn't be surprised in the norepinephrine effects have something to do with dopamine downstream even.  I'd be curious to see how this stacks into a natural treatment which has received some studies and some success (though much less than Adderall on the Conners ADHD Scale).

 

Thoughts?

 

Rich rewards: Scientists reveal ADHD medication's effect on the brain

Researchers scan the brain to uncover how medication for ADHD affects the brain's reward system

January 17, 2020

Okinawa Institute of Science and Technology (OIST) Graduate University

Researchers have identified how certain areas of the human brain respond to methylphenidate -- a stimulant drug which is used to treat symptoms of ADHD. The work may help researchers understand the precise mechanism of the drug and ultimately develop more targeted medicines for the condition.

Attention-deficit hyperactivity disorder (ADHD) is a neurobiological disorder characterized by symptoms of hyperactivity, inattention and impulsivity. People with the condition are often prescribed a stimulant drug called methylphenidate, which treats these symptoms. However, scientists do not fully understand how the drug works.

Now, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have identified how certain areas of the human brain respond to methylphenidate. The work may help researchers understand the precise mechanism of the drug and ultimately develop more targeted medicines for the condition.

Scientists believe that methylphenidate helps people with ADHD maintain focus by influencing dopamine availability in the brain. Therefore, Dr Furukawa and her colleagues set out to examine how the drug affects a brain region called the ventral striatum, which is a vital component of the reward system and where dopamine is predominantly released.

"We wanted to take a look at how methylphenidate affects the ventral striatum's responses to reward cues and delivery," said Furukawa.

Delving into the brain

The researchers used fMRI to measure brain activity in young adults with and without ADHD as they played a computer game that simulated a slot machine. The researchers scanned individuals in the ADHD group on two separate occasions -- once when they took methylphenidate and another time when they took a placebo pill. Each time the reels of the slot machine spun, the computer also showed one of two cues, either the Japanese character み (mi) or そ (so). While familiarizing themselves with the game before being scanned, the participants quickly learned that when the slot machine showed み, they often won money, but when the slot machine showed そ, they didn't. The symbol み therefore acted as a reward-predicting cue, whereas そ acted as a non-reward-predicting cue.

The researchers found that when individuals with ADHD took the placebo, neuronal activity in the ventral striatum was similar in response to both the reward predicting and non-reward predicting cue. However, when they took methylphenidate, activity in the ventral striatum increased only in response to the reward cue, showing that they were now able to more easily discriminate between the two cues.

The researchers also explored how neuronal activity in the striatum correlated with neuronal activity in the medial prefrontal cortex -- a brain region involved in decision-making that receives information from the outside world and communicates with many parts of the brain, including the striatum.

When the individuals with ADHD took placebo instead of methylphenidate, neuronal activity in the striatum correlated strongly with activity in the prefrontal cortex at the exact moment the reward was delivered, and the participants received money from the slot machine game. Therefore, the researchers believe that in people with ADHD, the striatum and the prefrontal cortex communicate more actively, which may underline their increased sensitivity to rewarding external stimuli. In participants who took methylphenidate, this correlation was low, as it was in people without ADHD.

The results implicate a second neurotransmitter, norepinephrine, in the therapeutic effects of methylphenidate. Norepinephrine is released by a subset of neurons common in the prefrontal cortex. Researchers speculate that methylphenidate might boost levels of norepinephrine in the prefrontal cortex, which in turn regulates dopamine firing in the striatum when rewards are delivered.

"It's becoming clear to us that the mechanism by which methylphenidate modulates the reward response is very complex," said Furukawa.


Edited by gamesguru, 11 June 2020 - 05:33 PM.

  • Pointless, Timewasting x 1
  • Disagree x 1

#2 kurdishfella

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Posted 13 June 2020 - 01:52 AM

my thought is are you gonna dedicate 1 whole thread to 1 study. why not compile bunch of things make it more interesting for more potential discussion. waste of time and space imo with these 1 question threads that can probably be figured out with a little research and own thinking.

Edited by kurdishfella, 13 June 2020 - 02:08 AM.

  • Agree x 1

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#3 Rorororo

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Posted 13 June 2020 - 03:32 AM

my thought is are you gonna dedicate 1 whole thread to 1 study. why not compile bunch of things make it more interesting for more potential discussion. waste of time and space imo with these 1 question threads that can probably be figured out with a little research and own thinking.

 

Well said.







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