However, even in persistent cases, the number of
symptoms decrease during adolescence and usually
decrease further in adulthood. The types of symptoms
also change. Hyperactivity and impulsivity tend to disappear, although adults with ADHD will often comment on their mental as opposed to physical restlessness.
From a biological vantage point, the reduction of symptoms
probably reflects brain maturation that continues
through adolescence and beyond.
What parts of the brain are affected in ADHD?
In studies of ADHD children, the structures that most
often have been found to play a role are the frontal
lobes, the striatum (particularly the caudate), and the
connection between these structures, which is called
the frontostriatal circuitry. More recently, the cerebellum
has also been found to play a role in ADHD.
If you are not a neurologist, that explanation probably
does not mean much, so here is a quick lesson in brain
anatomy and function. Your brain is made up of four
lobes: frontal, parietal, temporal, and occipital. By and
large, the frontal lobes control executive functioning
(e.g., planning, organizing, starting, persisting, shifting,
and inhibiting impulsive behaviors). The parietal
lobes control sensory functions and spatial skills (especially
the right parietal lobe). The temporal lobes control
language comprehension and memory, and the
occipital lobes control vision. The left frontal lobe has
the bigger effect on language-related executive functions,
and the right frontal lobe has more of an influence
on spatial executive function.
The striatum is made up of a number of structures
deep within the brain, the caudate being the most
active in ADHD. In healthy individuals, the striatum
is rich in dopamine. Some structures in the striatum
play a significant role in motor function. Parts of the
striatum are low in dopamine in such movement disorders
as Parkinson’s disease, leading to tremors and very
slow movements. Parts of the striatum have also been
found to be involved in tic disorders.
The frontostriatal circuitry forms the connection between
the frontal lobes and parts of the striatum. Brain cells
connect these structures, and the connection is maintained
by information passed between the cells via neurotransmitters.
Finally, the cerebellum is part of the hindbrain and has
been thought to primarily handle coordination. However,
recent studies suggest it plays an important role
in cognitive functions, such as language and attention,
as well as motor planning. Cerebellar striatal frontal
circuitry may also play a role in ADHD.
Where in the brain do neurotransmitters have their effects?
Neurotransmitters are chemicals in your brain that
pass along information from one cell to another. Neurotransmitters
act in the synapse, the space between
two brain cells (neurons). Neurotransmitters released
by presynaptic neurons act on receptors on postsynaptic
neurons. The amount of neurotransmitter
in the synaptic space and the sensitivity of the
postsynaptic cell receptors determine the neurotransmitter’s
effect on the postsynaptic brain cell.
There are many different neurotransmitters. Although
dopamine is probably the neurotransmitter that is
maximally involved in ADHD, norepinephrine and
serotonin probably play lesser roles. The relative balance
among these neurotransmitters may be as important
as their absolute amounts. Dopamine is the main
neurotransmitter in the striatum, while norepinephrine
is the main neurotransmitter in the frontal lobe.
Read More: Do children outgrow ADHD?
