Tuesday March 20, 2018

Scientists Discover Link Between Hallucinations, Dopamine

The researchers found that elevated dopamine could make some patients rely more on expectations, which could then result in hallucinations

For the study, published in the journal Current Biology, researchers designed an experiment that induces an auditory illusion in both healthy participants and participants with schizophrenia. Pixabay

People with schizophrenia, who experience auditory hallucinations, tend to hear what they expect an exaggerated version of a perceptual distortion that is common among other people without hallucinations.

According to the researchers, those with hallucinations and other psychotic symptoms are known to have elevated dopamine — the main area of focus for available treatments for psychosis — but it was unclear how this could lead to hallucinations.

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“Our brain uses prior experiences to generate sensory expectations that help fill in the gaps when sounds or images are distorted or unclear,” said Guillermo Horga, Assistant Professor at Columbia University Medical Centre.

“In individuals with schizophrenia, this process appears to be altered, leading to extreme perceptual distortions, such as hearing voices that are not there,” Horga added.

The researchers found that elevated dopamine could make some patients rely more on expectations, which could then result in hallucinations. Pixabay

They examined how building up or breaking down sensory expectations can modify the strength of this illusion. They also measured dopamine release before and after administering a drug that stimulates the release of dopamine.

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Patients with hallucinations tended to perceive sounds in a way that was more similar to what they had been cued to expect, even when sensory expectations were less reliable and illusions weakened in healthy participants, the researcher said.

This tendency to inflexibly hear what was expected was worsened after giving a dopamine-releasing drug, and more pronounced in participants with elevated dopamine release, and more apparent in participants with a smaller dorsal anterior cingulate — a brain region is previously shown to track reliability of environmental cues).

“All people have some perceptual distortions, but these results suggest that excess dopamine can exacerbate our distorted perceptions,” said Horga. (IANS)

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Young Men More Vulnerable to Mental Illness Than Women

The researchers found that the incidence of first-episode psychosis is high among ethnic minorities and in areas with less owner-occupied housing

mental illness
For the study, the researchers estimated the incidence of first-episode psychosis in six countries -- England, France, Italy, the Netherlands, Spain, and Brazil. Pixabay

Young men are more likely to experience first-episode psychosis, defined as the first manifestation of one or more severe mental disorders including schizophrenia, bipolar affective disorder, and depression, compared to women of the same age group, says a new study.

The findings published in the journal JAMA Psychiatry also showed that ethnic minorities and people living in socioeconomically disadvantaged areas are also vulnerable to severe mental illness.

The study showed that the incidence of first-episode psychosis was higher among men aged 18 to 24 than among women in the same age group. Pixabay

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“The study confirmed that the incidence of first-episode psychosis varies considerably between major cities and rural areas. It also showed that environmental factors probably play a crucial role in this significant variation,” said one of the researchers Paulo Rossi Menezes, Professor at University of Sao Paulo Medical School (FM-USP) in Brazil.

“Until the end of the twentieth century, the etiology of psychotic disorders was believed to be mainly genetic, but the results of this study show that environmental factors are extremely important,” Menezes said.

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Menezes said this finding confirms fairly consistent data in the literature. Pixabay

He noted that the incidence of first-episode psychosis among young adult males is higher than among young adult females according to previous research, which also shows that as men approach 35, it tends to converge with the incidence among women.

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In women aged 45-54, it is slightly higher than among men in the same age group.

“We don’t know exactly why there are these differences in incidence between sexes and age groups, but they may be linked to the process of cerebral maturation: the brain matures between the ages of 20 and 25, and during this period, men seem to be more vulnerable to mental disorders than women,” Menezes said.

The researchers also found that the incidence of first-episode psychosis is high among ethnic minorities and in areas with less owner-occupied housing. (IANS)