The brain chemical associated with reward also seems to distort our perceptions.
By Jack Barton
Did you know you’ve probably hallucinated in the past week? Multiple times, most likely. You don’t need to be concerned; these episodes are a relatively common experience for healthy people.
You might have heard your name being called in an empty street, or sworn your phone beeped at you, only to find no notifications. These “low-level” hallucinations occur for around 10-15 percent of people, and they can help us uncover how hallucinations are formed in health and illness.
A team of researchers from Columbia University, led by psychiatrist Clifford Cassidy, took full advantage of these hallucinatory experiences, and described their work in a recent paper for Current Biology.
One potential culprit is the brain chemical dopamine. Dopamine has been shown to be involved in numerous brain functions, including reward, motivation, and pleasure, broadly speaking. And scientists have long suspected its role in unusual experiences like hallucinations.
In the 1950s, researchers stumbledupon a new class of drugs that provided relief for those suffering from schizophrenia. These drugs were known as antipsychotics and, as the name suggests, they reduced symptoms like hallucinations and delusions — primarily by reducing the levels of dopamine in the brain. This led clinicians and scientists to argue that dopamine was linked to the experiences of psychotic symptoms, and a concerted research effort ensued, seeking to solve the puzzle of why excess dopamine might produce hallucinations.
Although it was later shown that increasing dopamine could produce hallucinations, establishing a consistent link between them, it has not been clear why. This is where the latest series of studies by Cassidy and his colleagues comes in.
In their first study, they were able to produce hallucinatory experiences within the lab — a difficult thing to achieve convincingly. Hallucinations are by definition subjective, personal to whoever experiences them. Yet the team had to find a way to study hallucinations under controlled conditions in order to make scientific claims.