In the human brain, there are intermediary molecules called neurotransmitters that mediate the transmission of various signals and directly affect important higher brain functions such as learning, memory, perception, cognition, attention and focus, hyperactivity, arousal, and suppression. These are the main ones; Acetylcholine, Glutamate, GABA, Glycine, Serotonin, Dopamine, Adrenaline, Norepinephrine. Each of them has different functions in the brain, and as a result, they directly affect important psychological and behavioral outcomes in humans, such as learning, memory, attention and focus, emotions, and the control of movements. The amounts of signaling molecules in the brain and their functional impairments directly result in dysfunctions of the functions represented and mediated by the signaling molecule.

It has been determined that in individuals with autism, there are decreases or increases in the levels of these signaling molecules in the brain, and that this situation is associated with the behavioral disorders observed in autism.

Based on this, balancing the amounts of relevant signaling molecules in the brain and maintaining that balance will undoubtedly contribute to the reduction, alleviation, and improvement of behavioral disorders seen in autism.

Most of these signaling molecules are synthesized by bacteria present in the gut microbiota.