Dr. Grossi's Blog


Dr. Philip Grossi
Friday, 28 January 2011

ADHD is an illness that revolves around disturbances in attention, hyperactivity, and impulsiveness.  It comes in inattentive, hyperactive, and combined types.  I do not plan to discuss the criteria further here as they are readily available on many sites including two that the reader can access from the home page of this site by clicking on recommended links.

I would like to talk about how the pathology of the disorder is understood.  Irrelevant and extraneous signal inputs to the prefrontal cortex (PFC) are considered too strong to be ignored while at the same time the signal inputs from what should be attended to are too low to be noticed.  In children who have ADHD, dopamine (DA) and/or norepinephrine (NE) are thought to be low, which in turn causes deficient activity at the pyramidal neurons.  This results in high noise and low signals.  From a clinical standpoint, this produces hyperactivity, impulsivity, and inattention in children and mostly inattention in adults.

illustration to ADHD blogTreatment of these symptoms most often involves prescription of stimulants (amphetamine molecule or methylphenidate molecule) which theoretically should increase input signal strength by increasing NE activity and reducing  extraneous input signals by increasing DA actions. S. Vijayraghavan et.al. have shown that pyramidal neurons process information in an inverted U curve.  Therefore low signals can be augmented by NE and high extraneous input can be decreased by DA. 

What explains prominent inattention in adults that we see in the office?  Often these individuals are under enormous stress of various sorts including financial, marital, business, family, health, etc. In these individuals, it is hypothesized that the NE and DA levels in the PFC are too high and the inattention is again accounted for by the information processing by the pyramidal neurons in the PFC.  In this case, stimulants will probably make the situation worse or at best produce little effect.  In those cases of chronic stress the levels of DA and NE are lowered and in the event of co-morbid ADHD the risk of substance abuse and anxiety disorders is increased. These are subtle differences that the clinician must appreciate to achieve best results.