How do the sounds in dreams arise, do they have anything to do with hallucinations?

Marketa Juristova

Do you know the popular mental argument about whether sound exists when no one can hear it? What if a tree falls in the forest and no one is around? So does sound even exist without another device to detect and "read" it? The basis of sound is a vibration that stirs the environment and this acts on the eardrum, we then perceive this vibration as sound.

In a previous article I wrote that, "If the particles vibrate regularly, a perception of a tone of a certain pitch is created in the ear and thus we actually perceive, hear a melody. The pitch of each tone is determined by the frequency of this vibration. Even people who are deaf can perceive music thanks to the frequency, because they absorb it with their whole body."

So, we know the technicalities of sound perception, but the problem arises when we realize that we can hear sounds even without vibrations in the environment. I'm talking about everyone's unquestionable experience of dreams. In dreams, we quite normally perceive sound. Psychiatrists know of another phenomenon where no known environmental stimulus is present, auditory hallucinations in various psychiatric illnesses.

Dreams and psychotic hallucinations have something in common. They both contain sensations that seem real but are probably triggered by our brains. But there are differences. While dreams are known to be highly visual, psychotic hallucinations are primarily auditory. They generally involve sounds that are not real. And this difference is a significant reason why "the idea of dreaming as a model of psychosis has remained speculative and controversial," as Roar Fosse of Vestre Viken Hospital Trust, Norway and Frank Larøi of the Norwegian Centre of Excellence for Research on Mental Disorders. at the University of Oslo, write. However, very little research has been done so far on the perception of sounds in dreams, the pair of researchers say . And now they have data suggesting that in fact auditory perceptions are common. If so, the link between psychotic experiences and dreams may be stronger than recently thought.

Researchers have found that sounds in dreams occur frequently and are present in 80% to 100% of each participant's dreams. Most often, the sounds consisted of other people talking. (There were even five instances described as speech in a foreign language that the dreamer did not understand.) But there were also 122 instances where the dreamer heard speech, and 59 instances of other types of sounds, such as glass breaking, gun shots, walking, or a radio playing. Given that dream reports only include experiences from the last minutes of sleep before waking, and that dreaming normally takes place during REM sleep as well as light NREM sleep, the available evidence suggests that normal, healthy people typically experience internally generated auditory sensations several times each night.

This research suggests that there are some parallels between the normal sleep-wake cycle and theories about how psychotic hallucinations arise. When someone falls asleep and moves through the early sleep stages into REM sleep, there is a general decrease in reflexive, controlled thinking and a gradual increase in internally generated sensations. Theories of psychotic hallucinations suggest that impairments in higher-order "top-down" areas (typically in the prefrontal cortex) allow for more internally generated, sensory-like hallucinatory experiences. Evidence has also been found suggesting similarities in the neurophysiological underpinnings of both dreams and psychotic hallucinations. For example, both conditions are associated with similar changes in dopamine functioning and patterns of connectivity between specific cortical regions.

The above research is interesting, but it does not answer the question of where this internal auditory perception- sound hallucination- comes from. Dr. Albert Powers of the Connecticut Mental Health Center decided to try to answer this question. While most researchers have previously focused on brain abnormalities that occur in people suffering from schizophrenia and severe psychosis, Powers and his colleagues have turned their attention to milder cases in a new study.

Normally, when the brain receives sensory information such as sound, it actively works to fill in the information to make sense of what it hears - its location, volume and other details.

"The brain is actually a predictive machine. It constantly scans the environment and relies on prior knowledge to fill in the gaps in what we perceive. Because our expectations are usually accurate, the system generally works well. For example, we are able to hear the sound of running water or the whisper of a friend talking across the room and then react in an instant." Anissa Abi-Dargham, a psychiatrist at Stony Brook University School of Medicine

One theory posits that hallucinations arise when the brain relies too heavily on these expectations and fills in the details even when actual auditory input does not exist. Culture and religion may also play a role in interpreting what individuals perceive. To test the idea that hallucinations are the result of the brain's over-expectation, Powers and a colleague at Yale University, psychologist Philip Corlett, decided to study a diverse group of people who regularly reported hearing voices (including those diagnosed with psychosis) along with clairvoyants who had not been diagnosed with any psychiatric illness.

The team visited a local psychic organization in Connecticut and began screening individuals using forensic psychiatric techniques to ensure that people were not simply pretending to have auditory hallucinations. Almost immediately, the two noticed that the psychics' descriptions of hearing voices bore a striking resemblance to the experiences of their patients diagnosed with psychosis. "They sounded the same in terms of how loud the voices were, how often they occurred, where they heard them in space (inside or outside the head ), and the length and complexity of what the voices were saying," Powers says.

The researchers devised a series of experiments to introduce new beliefs about sensory information. The team presented this new information to psychics, patients diagnosed with psychosis, and others in a control group who had not previously heard voices. They paired a visual stimulus of a checkerboard on a computer screen with a short 1-kilohertz tone that repeatedly presented light and sound until participants learned to associate the two. They then measured how much people relied on this prior sensory knowledge when they were shown the visual stimulus without sound. Initially, at least some members of all groups heard the sound even when it was not there. But the researchers found that both clairvoyants and people who were prone to psychosis were more likely to hear a tone when none was presented than those who did not hear voices. The two voice-hearing groups were also much more confident in their assertion that the sound had occurred. Powers and Corlett took these reports to mean that these groups had developed extremely strong beliefs that visual stimuli were associated with tones. Their earlier belief that tone was always accompanied by sound fueled their auditory hallucinations.

But when the researchers conducted further toneless tests, the clairvoyants and a group of healthy adults who could not hear voices were able to revise their beliefs about the connection, or lack thereof, between the chessboard and the tone. But those in the study who were diagnosed with a psychotic illness were unable to detect that the tone was no longer present. "The results match up pretty well with what we see clinically on a daily basis here at Connecticut Mental Health Center. It's really hard for people with psychotic illness to let go of their beliefs, even when everyone around them agrees that what they're hearing isn't really happening." Notes Corlett.

The findings from this research, which have been published in the journal Science, provide insight into the common neural mechanisms that can drive auditory hallucinations, as well as what can attenuate these experiences in some people. Researchers may be able to use these findings to begin developing new therapies, whether drugs or brain stimulation (transcranial magnetic stimulation), that target the areas most affected in patients with schizophrenia and other disorders. While it may be a while before such therapies are ready for clinical use, Powers and Corlett still hope to learn a lot about how the brain works by looking at the biggest difference between psychosis patients and healthy people: specifically, how changing beliefs can affect perception. They liken this phenomenon to the placebo effect, where people who believe a pill will work automatically have their symptoms alleviated.

Very useful research from my point of view, because the phenomenon of sound in dreams (or hallucinations) is hardly mapped at all, but it is still an open question how the brain complements the content of the dream characters' messages. Where is the source? And where does the voice come from that comes from the surrounding space in lucid dreams, for example? Personally, I was most struck by the information that "space is the idea of love" ( see my book published in 2021 "The White Book of Lucid Dreams"). Here it cannot be a conditioning reflex (I see something -suppose a sound). We must wait for some better explanation, or maybe it will remain a mystery to us.