YSM Issue 90.4

neuroscience
NEWS
NOW YOU HEAR ME, NOW YOU DON’T
Testing susceptibility of people to hearing voices
►BY SUNNIE LU
PHOTOGRAPHY BY YASMIN ALAMDEEN
►Dr. Powers and Dr. Corlett took MRI scans of people
performing auditory tasks to understand auditory hallucinations.
You hear footsteps coming down the hallway and voices chanting,
“We’re coming.” A shadowy figure suddenly appears in the
corner of your room, while a girl dressed up as a rat looms over
your bed. Although these scenarios sound like they come from
horror movies, they actually are real examples of hypnagogic hallucinations,
which occur during the onset of sleep. Both having
these experiences, Yale psychiatrist and neuroscientist Albert
Powers and Yale neuroscientist Philip Corlett fascinated with
auditory hallucinations. Their research, featured in Science, suggests
that people who hear voices are more likely to experience
induced hallucinations in a lab.
It may seem concerning that both Powers and Corlett have
experienced hallucinations while falling asleep, but these hallucinations
are usually symptomatic of a neurological condition,
not a psychiatric illness. However, people without a psychiatric
condition can hear voices too. The two scientists wanted to figure
out what produces auditory hallucinations and why some
voice-hearing experiences are benign and others require medical
attention.
To explore these questions, they sought out four groups of
test subjects: both psychotic and nonpsychotic voice-hearers
and non-voice-hearers. After identifying potential subjects, the
researchers separated the psychotic and nonpsychotic people
using a questionnaire developed by forensic psychologists to
distinguish between people who were actually experiencing hallucinations
and those who only claimed to do so.
After screening their subjects for hallucinations, Powers and
Corlett induced auditory hallucinations in their subjects to identify
whether psychotic people were more likely than non-psychotic
people to hear conditioned sounds. Using a technique
originally developed at Yale during the 1890s, the subjects were
stimulated with a checkerboard image and a one-second long
sound simultaneously and repeatedly, while getting their brains
imaged by MRIs. This conditioned the subjects to associate the
image with the tone. As the scientists changed the intensity of
tone, sometimes turning it off, the subjects pressed a button when
they thought they heard the tone, while changing the length of
time they pressed the button to show their level of confidence.
Many reported hearing a tone when only the checkerboard
image appeared but no tone played. This inconsistency occurred
more often with the two voice-hearing groups—the people with
schizophrenia and self-identified clairaudient psychics. Both
groups were almost five times more likely to report that they
heard a nonexistent tone than the non-voice-hearing groups.
Furthermore, the two non-voice-hearing groups were 28 percent
more confident that they had heard the tone when no tone
played. These results support a possible explanation for hallucinations.
“The brain makes models for what the outside world is
like,” said Corlett, noting that these models sometimes don’t always
match reality. This study suggests that people hallucinate
when their expectations overweigh what their senses tell them.
Powers and Corlett further understood auditory hallucinations
through analyzing the MRI scans collected: the parts of the
brain that were responsive to the tone were active when people
reported conditioned hallucinations, producing MRI scans of
brains that looked like those of people actually hearing the tone.
The images also revealed that both hallucinating and non-hallucinating
people with psychosis exhibit abnormal brain activity in
regions that monitor internal representations of reality. These results
contribute to the idea that hallucinations stem from internal
representations overruling actual sensory data.
This study was able to distinguish not only between those who
hallucinate and those who don’t, but also between psychotic and
non-psychotic people. “The sooner you catch psychosis and the
sooner you intervene, the better the general outcomes are,” said
Powers. According to Powers, most people with the symptoms
associated with increased chances of psychosis don’t even develop
psychosis. The question then is, who should receive treatment?
This new research may help to answer that key question
by providing the basis for tests to diagnose patients who require
psychiatric treatment early.
“There is no one-size-fits-all anti-psychotic, so there should be
different treatments for different people,” Corlett said. Although
this sort of precision medicine has not existed in psychiatry so
far, Corlett hopes that this study, along with future research, will
lead to more personalized psychiatric treatments, which he believes
would be more effective in helping people suffering with
mental health issues.
www.yalescientific.org
October 2017
Yale Scientific Magazine
9