As a species, our perceptions of reality can be somewhat fluid, with some people picking up impulses that other people won't experience at all. Consider the case of a schizophrenic patient who hears voices – are they just overly sensitive? Keep in mind that people with no history of psychotic illness also report hearing voices.
There are many factors that contribute to auditory hallucination and we’re going to discuss what happens when you’re hearing voices in your head.
According to a report published in the journal eLife, Professor Thomas Whitford (a scientist at the UNSW School of Psychology) conducted a study to establish the mechanism of brain chatter and the processes that cause us to respond in certain ways to inner speech.
In their study, the team at UNSW selected 42 individuals to measure the extent to which imagined sounds caused a clash with brain activity created by real sounds – and they used electroencephalography for the experiment.
According to this study, the ability to imagine a sound caused a reduction in mental activity when a person finally heard that sound. In this way, our thoughts are able to change the way our brain perceives certain sounds and the impact of these sounds is lessened when we anticipate them.
Existing research into this phenomenon suggests that when a person prepares to speak, the brain generates a copy of these instructions and transmits this information to the mouth and vocal response. By anticipating these sounds that we create deliberately, the brain is able to discriminate between sounds produced by us and other less predictable sounds that come from our environment.
This copy of information in the brain allows us to dampen the brains response to self-generated sounds, allocating fewer resources to these vocalizations. Researchers are expected to use this information to determine the way in which schizophrenic people respond to these sounds and the manner in which their brains process sound, both external and self-vocalized.
In a different experiment, Philip Corlett, assistant professor of psychiatry at Yale wanted to understand more about why some people hear voices. According to Corlett, hallucinations may be caused by a disturbance in our expectations about our immediate environment and the information received by our senses.
To investigate this phenomenon, a team at Yale employed a technique produced in the 1890s to measure sound hallucination. In the experiment, four distinct groups of individuals were presented with a tone and light at the same time while undergoing brain scans.
The volunteers were then asked to detect the tone, at which point many of the subjects reported hearing a sound when only the light was presented. This effect was more pronounced in the group with individuals who had reported hearing voices in the past.
Individuals with a psychotic illness had a more difficult time accepting that they didn’t really hear a sound and in fact showed altered brain activity particularly in sections associated with psychosis. This research is expected to provide material for understanding the correlation between our assumptions and mental responses to auditory and visual hallucinations.
Ultimately, researchers are working to identify people who are experiencing these kinds of hallucinations and to provide treatment and solutions if these people are perceived to be heading toward psychosis.
Learn more about this topic:
- Schizophrenia's Hallucinated Voices Drown Out Real Ones
- How to Use Daydreaming to Your Advantage
- How the Brain Can Hear Voices That Don't Exist