Human beings are over 99% genetically identical. It seems striking therefore, that 1% of this genetic difference accounts for the large extent of individual variations seen in human behaviour and brain function. One promising alternative source of individual differences is the resident bacteria in the gastrointestinal tract,which is 40-90% distinct between different individuals. Bacteria in the human gut outnumber human cells, and account for nearly 10 times as much DNA as that from human cells. Some gut bacteria have been shown to produce Gamma Amino Butyric Acid (GABA) and serotonin (5-HT), molecules that function as neurotransmitters in the human brain. However, it is not known whether their production in the gut has any impact on behavioural and brain function. This project focuses on GABA, a neurotransmitter that often serves as the 'brakes' in the communication between neurons.
The overall objective of the project is to test if GABA produced by bacteria in the gut can influence brain levels of GABA or behaviours that depend on GABA. If the project finds evidence to support this possibility it can open up a new frontier of research on how diet can influence brain functioning. At a more fundamental level, it can point to processes outside the brain through which brain levels of GABA are maintained.