This is not a comprehensive list, simply some articles I have found along the way.
“GABA, which is short for gamma-aminobutyric acid, is your primary inhibitory neurotransmitter. Its primary role is to calm the brain, slow things down and relax you. One of the ways that it assists in this process is by increasing alpha wave production. It is also vital in speech and language. GABA puts the pause or space between words when you speak. The brain uses it to support sensory integration. Without adequate GABA production, our conversations would consist of lots of run on sentences, slurred speech or loss of speech, and we would have trouble with comprehending language.”
“When GABA is low, glutamate is high and vice versa. So in order to increase gamma-aminobutyric acid it’s not simply a matter of bringing it up, you must also focus on reducing the excess glutamate. The goal is to achieve balance between the two. You might think of glutamate as the accelerator and GABA as the brakes. Both are equally important.” (http://www.holistichelp.net/blog/how-to-increase-gaba-and-balance-glutamate/)
“Acquired stuttering, on the other hand, can occur at all ages and can be caused by brain injury and by pharmacological agents. Theophylline-induced stuttering is form of acquired stuttering. It is a rare side effect of theophylline therapy, but it provides interesting clues to the pharmacological mechanisms involved in stuttering. Theophylline-induced stuttering may involve the disrupt the optimal balance between excitatory and inhibitory neurotransmission throughout the brain by inhibiting GABA receptors. The disruption of the optimal balance between excitatory and inhibitory neurotransmission can also cause dysfunction in white matter fiber tracts such as those that connect the Broca’s area to the motor cortex” http://www.ncbi.nlm.nih.gov/m/pubmed/15607558/
“Gaba is necessary for speech. Gaba creates the “gap” between words” (http://dramyyasko.com/wp-content/uploads/2010/06/17-A1-Excitotoxins.pdf)
“Rhythmic Movement Training in Autism- The rhythmic exercises stimulate many of the areas of the brain which are damaged in autism and improve their function. For optimal effect of RMT the gastrointestinal function need to be addressed. Otherwise toxins, peptides and allergens will cross the mucosa and be transported from the bowels and pass the blood brain barrier, causing continued brain damage by inflammatory and toxic reactions of the brain. It happens quite frequently that the child gets over stimulated by rhythmic exercises and reacts with restlessness and hyperactivity. Such reactions may occur also in children with ADD and ADHD. The cause of these reactions is probably an inability of the brainstem to filter stimulation from the tactile, vestibular and proprioceptive senses. Excessive stimulation reaches the brain and activates its GLUTAMATE RECEPTORS. Glutamate is the most widespread transmitter substance in the brain. If there is an inability to convert stimulating glutamate into inhibiting GABA the child will soon become restless and start wriggling and try to get away. Therefore a child with autism should be on a diet free from gluten, casein and preferably soy. This is especially important for children who do rhythmic exercises. Self stimulating Behavior – If the concentration of glutamate rises to toxic levels outside the neurons they start firing uncontrollably causing self stimulating behavior or stims. These are repetitive body movements that stimulate one or several senses in a regulated manner. They include- hand flapping, body spinning or rocking, mechanically lining up or spinning toys, repeating rote phrases, echolalia, i.e. mechanically repeating what others say
perseveration, (repetition of a particular response, such as a word, phrase, or gesture, despite the absence or cessation of a stimulus). Rhythmic exercises improve speech – Almost all children with autism or ASD have more or less obvious difficulties doing simple active rhythmic exercises. Such difficulties are also common in children with ADD, ADHD and late speech development and indicate a damage of the cerebellum. Such damage is especially common in autism and has been confirmed by many research studies. Damage of the cerebellum may prevent speech from developing since speech cannot develop if the speech areas of the left hemisphere don´t get sufficient stimulation from the cerebellum. By stimulating the cerebellum with rhythmic exercises speech development will be promoted. The Purkinje cells of the cerebellum use GABA as a transmitter substance and the rhythmic exercises will in the long run cause more GABA to be produced provided inflammation of the cerebellum and glutamate accumulation can be prevented by an appropriate diet. http://www.blombergrmt.com/autism-and-rhythmic-movement-training/
Gluten sensitivity and nutritional deficiencies causing symptoms of apraxia and autism. “A total of 187 children with verbal apraxia received vitamin E + polyunsaturated fatty acid supplementation. A celiac panel, fat-soluble vitamin test, and carnitine level were obtained in patients having blood analyzed.” “In all, 181 families (97%) reported dramaticimprovements in a number of areas including speech, imitation, coordination, eye contact, behavior, sensory issues, and development of pain sensation.” “Appropriate screening may identify a subgroup of children with a previously unrecognized syndrome of allergy, apraxia, and malabsorption who are responsive to nutritional interventions in addition to traditional speech and occupational therapy. Controlled trials in apraxia and autism spectrum disorders are warranted.” http://www.ncbi.nlm.nih.gov/pubmed/19623831