World Health Day: ADD a result of dysfunction in gene that helps different brain regions communicate

NEW YORK: Impaired brain coordination can lead to attention deficit disorders, including schizophrenia, bipolar disorder and major depression, a study has found.

People with attention deficits have difficulty focusing and often display compulsive behaviour.

The study suggests these symptoms could be due to dysfunction in a gene - ErbB4 - that helps different brain regions communicate.

The gene is a known risk factor for psychiatric disorders, and is required to maintain healthy neurotransmitter levels in the brain.

In a study published in the journal Neuron, researchers from Case Western Reserve University in the US showed mice lacking ErbB4 activity in specific brain regions performed poorly on timed attention tasks.

The mice struggled to pay attention and remember visual cues associated with food.

Neuroscientists describe the kind of thought-driven attention required for the tasks as "top-down attention".

Top-down attention is goal-oriented, and related to focus. People who lack efficient top-down attention are at a higher risk for attention deficit hyperactivity disorder (ADHD).

"The results reveal a mechanism for top-down attention, which could go wrong in attention disorders," said Lin Mei from Case Western Reserve University.

The study found that when a protein (neuregulin-1) attaches to the ErbB4 receptor, it triggers a chain reaction that ultimately determines neurotransmitter levels in the prefrontal cortex and hippocampus.

Without ErbB4, neurotransmitter levels go awry. The researchers discovered mice lacking ErbB4 have low levels of a particular neurotransmitter - GABA, or gamma-aminobutyric acid - in their brain.

Low GABA levels can lead to impaired top-down attention in the prefrontal cortex, and impairs how the prefrontal cortex can efficiently coordinate with the hippocampus.

The researchers concluded that ErbB4 helps link the two brain regions to maintain attention.