Dysfunctional gene linked to ADHD, schizophrenia identified

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New York: Dysfunction in a gene that can lead to attention deficit hyperactivity disorder (ADHD) schizophrenia, bipolar disorder and depression has been identified.

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

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

ErbB4 is also a risk factor for psychiatric disorders and is required to maintain healthy neurotransmitter levels in the brain.

"And since ErbB4 is a risk factor for schizophrenia, bipolar disorder, and major depression, the results provide insights into mechanisms of these disorders," said Lin Mei, Professor Case Western Reserve University School of Medicine in Cleveland. 

In the findings, published in the journal Neuron, researchers 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 ADHD. 

The study is the first to connect ErbB4 to top-down attention.

"The results reveal a mechanism for top-down attention, which could go wrong in attention disorders," Mei said. 

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 results showed that mice lacking ErbB4 have low levels of a particular neurotransmitter GABA, or gamma-aminobutyric acid, in the brain. 

This further led to impaired top-down attention in the prefrontal cortex and impairs how the prefrontal cortex can efficiently coordinate with the hippocampus, a region that supports memory and attention.