The brain is an exceedingly complex organism. So complex, in fact, that despite centuries of Scientists and Philosophers devoting their lives to studying it, we still do not fully understand how it develops, functions, or degenerates. We do know, however, that all behavior, voluntary or involuntary, functional or dysfunctional manifests from activity across the complex networks of the brain. We also live in a time of amazing advances in neurotechnology. We have tools to visualize the structure and function of the brain through magnetic resonance imaging (MRI), functional MRI (fMRI), electroencephalography (EEG), and other tools. And we have pharmacological, behavioral, and device-based interventions that have been shown to lead to long-term effects on brain network functioning. So, if all behavior comes from brain functioning and we have a means to measure and manipulate brain functioning, then why have we not “cured” all behavioral disorders?
When I started studying Clinical Neuroscience 20 years ago, I thought for sure by now we would have discovered the “cause” of neuropsychiatric disorders such as Autism, Depression, Anxiety, post-traumatic stress disorder, etc. and be well on our way to targeted treatments, if not cures. And as a side note, as a postdoctoral fellow I very humbly set as my personal goal to lead this mission and when I did accomplish this clearly attainable goal, I was sure to win the Nobel Prize! I soon realized, however, that if the answers were clear and simple, the incredibly smart people who have been working on this problem for hundreds, if not thousands of years would have already figured it out! So, should I give up? Certainly not. But where should I start? Where I started was by reading the literature. Reading broadly and deeply. Understanding what we know, what we think may be right, and what we absolutely have no idea about. What I have learned so far (20 years after beginning this journey) is that despite the complexity, the brain is set up in a highly specified manner: Behavior manifests out of brain networks, brain networks grow from individual neurons (cells) which contain specific molecules (neurotransmitters). And the green grass grows all around all around and the green grass grows all around!
Diagnosticians in the area of Psychiatric and Behavioral Disorders (those that specialize in defining disorders based on a set of observable behaviors) have grouped sets of behavioral disorders that tend to present together in a given individual into specified disorders. However, the brain is not responding the way it does, or setting up networks the way it does, based on a Doctor declaring that the person has Autism or ADHD or Depression…, it is simply responding to stimuli (environmental, sensory, pharmacological, etc.) based on its current network structure and state-dependent functioning. Both the network structure and state is constantly being updated and adjusted (through changes at molecular, cellular, and large-scale network levels) based on previous stimuli (individual experiences). This is known as brain plasticity, a capacity the brain has throughout life.
Thus, the cause” or “ best treatment” for Autism or any other Psychiatric or Behavioral Disorder does not have a simple answer. Regarding “cause,” do we want to know what the primary cause is (ie. What leads someone to develop the defined disorder) or do we want to know what causative mechanism is underlying current behaviors? The question of what leads someone to develop the defined disorder is important in terms of understanding genetic risk factors and for early identification, but is less important when it comes to treatment due to the brain plasticity discussed above. The current state of the brain is likely a combination of both the original causative mechanism (which could have occurred years earlier, and potentially prenatally), environmental stimuli and experiences that the individual has had since that causative mechanism, and the consequential plastic changes the brain has undergone in response to those causative mechanisms and environmental stimuli and experience. So, if the question is what is currently underlying the current behaviors, then we must understand the current structure and state-dependent functioning of the individual’s brain networks. Additionally, we need to assess if we want to know this information at a molecular level (to see if a certain drug or neurotransmitter may be an effective treatment) or at a network level (to see if perhaps Transcranial Magnetic Stimulation or other device-based treatments may be effective) or at a cognitive-behavioral level (to see what behavioral intervention may be effective). Finally, we must first understand what behavior(s) we are trying to improve (so called “negative symptoms”) or reduce in severity (so called “positive symptoms”). Accepting the complexity of the brain and the wide variety of symptoms that define specific disorders, it is highly unlikely that we will find a singular treatment for “Autism” or “Depression” but rather treatments for specific common behaviors associated with these disorders. The brain does not know its diagnosis!