2-Minute Neuroscience: ADHD

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Attention-deficit/hyperactivity disorder, or ADHD,   is a condition characterized by difficulties with  attention and/or hyperactivity and impulsivity.   ADHD involves strong genetic influences, but  environmental factors, and interactions between   genetics and the environment, are thought  to play an important role in ADHD as well.
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Much of the recent research into the neuroscience  of ADHD has focused on understanding the brain   networks that might underlie different  aspects of cognitive function in ADHD.   One example is the default mode network,  which is a collection of brain regions   that is more active during mind-wandering and  introspection, and less active when a person   is attempting to complete a specific task.  Studies have found that people with ADHD have   atypical connectivity in the default mode network,  which might be associated with distractibility. Individuals with ADHD also display  lower activity in brain networks   that are involved in attention and cognitive  control. Typically, activity in these networks   increases when activity in the default  mode network decreases, and vice versa.   Thus, one hypothesis is that in ADHD activity  in the default mode network is dysregulated   and interferes with the function of networks  involved in attention and cognitive control.
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Studies have also found that people with ADHD tend  to display atypical activity in the reward system,   a group of structures that are  involved in motivated behavior,   anticipation, and reinforced learning.  This atypical reward system activity   might be associated with a tendency to  overestimate the value of short-term rewards   in comparison to long-term rewards, which  could also affect planning and decision-making.   The reward system includes some of the major  dopamine pathways in the brain, and dopamine is   often implicated in ADHD because medications that  are commonly used to treat the condition, such as   amphetamine and methylphenidate, cause increased  transmission of dopamine and norepinephrine.