Neuroanatomy of ADHD

To understand ADHD and the spectrum of how it manifests in different individuals, it’s good to go back to the organ central to it, the brain. The frontal cortex which is essentially where your forehead is, governs what is called the executive functions that is deficient in people with ADHD. But the networks down the pathway are also affected in ADHD and each pathway will result in different manifestations.

Pre-Fontal Cortex (yellow)

Multiple neuroimaging meta analyses have proven that other areas are involved in executive functions such as the corpus callosum, basal ganglia, caudate nucleus and globus pallidus. These regions are typically rich with dopamine receptor and that explains why ADHD is neurobiologically explained by a lack of dopamine or lack of sensitivity of dopamine receptors. Which in turns explains why stimulants work like miracles.

The portion that controls emotions are also known as the cingulate gyrus which is situated in the inner parts if you were to imagine where your right and left cerebellar cortices meet.

The chaos ADHD cannot regulate

The frontal cortex is the last part of the brain to fully develop and attains full maturation at late adolescence, which by WHO definition is around 19 years of age. The dorsal and medial portion controls motor and attention while the ventral and lateral parts deal with emotions.

1. Attention

• Top down
  • Goal oriented attention
  • Meaning the stimulus starts at the frontal cortex and travels down to the basal ganglia, sensory cortex at various areas of the cerebrum and also to the cerebellum.
  • Meaning you think of something and the thought acts as a stimulus to activate the relevant EFs
  • example–> Stimulus: I need to study for this exam then the brain activates the motor and sensory areas needed to accomplish the task
• Bottom Up
  • stimulus driven attention
  • the stimulus is perceived from external source and activates relevant Efs
  • Example–> Stimulus: Playing video games. Images and sounds trigger the sensory cortex and sends signals to the temporal and parietal lobes which coordinate bottom down attention

Bottom Up Attention

Both pathway are independent and only top down attention is affected in ADHD as the stimulus originates in the frontal cortex

So now you can understand why we can play video games for hours and not be able to sit for 5 mins to study? Wink!

2. Behavior Regulation

• In charge of inhibiting inappropriate motor behavior by way of the motor/premotor cortex, basal ganglia and cerebellum
• Shows up as motor restlessness
  
  

3. Emotional regulation

• Inhibits impulsive aggressiveness and emotional dysregulation through activation of the limbic system(hippocampus, amygdala, brainstem
• Manifests as oppositional behavior and exaggerated emotional responses inappropriate to situation

That’s basically a simplified version of the neuroanatomy detailing the pathophysiology of ADHD. Now you see that the common understanding or what people think ADHD is doesn’t even begin to describe the disorder. That’s why people find it hard to accept there even is such a thing as ADHD. Oh, just shut up, go drink coffee and focus like the rest of us!