attention deficit hyperactivity disorder (ADHD)

Cell dysfunction adds to brain clutter

MCGILL (CAN) — The malfunction of a filter neuron inhibits the brain from sifting through information and separating the unimportant from the relevant.

The findings could be highly significant for identifying the causes and improving the diagnoses and treatments of a wide range of mental disorders including ADHD and schizophrenia.

The study is published in the journal Neuron.

It has been assumed that people with diseases like ADHD, Tourette  syndrome, obsessive compulsive disorder, and schizophrenia suffer from anomalies in the brain’s prefrontal cortex.

Damage to this brain region is often associated with failure to focus on relevant things, loss of inhibitions, impulsivity, and various kinds of inappropriate behavior.

But exactly what makes the prefrontal cortex so essential to these aspects of behavior has remained elusive, hampering attempts to develop tools for diagnosing and treating these patients.

Julio Martinez-Trujillo, professor of physiology at McGill University, believes the key to the brain clutter and impulsivity shown by individuals with dysfunctional prefrontal cortices lies in a malfunction of a specific type of brain cell.

He has identified neurons in the dorsolateral sub-region of the primate prefrontal cortex that selectively filter out important from unimportant visual information.

“Contrary to common beliefs, the brain has a limited processing capacity. It can only effectively process about one percent of the visual information that it takes in,” Martinez-Trujilo says. “This means that the neurons responsible for perceiving objects and programming actions must constantly compete with one another to access the important information.

“What we found when we looked at the behavior of the neurons in the prefrontal cortex, was that an animal’s ability to successfully accomplish a single action in the presence of visual clutter, was dictated by how well these units suppressed distracting information.”

The research was funded by the Canada Research Chair program, Canadian Institutes of Health Research, EJLB Foundation, and Natural Sciences and Engineering Research Council of Canada.

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