Imaginary speech subjectively reduces the volume of the sound around a person

Experiment Results: The perceived loudness rating of the surround sound among the subjects who imagined a loud sound (red line), a quiet sound (blue) or did not imagine any sound (black)

There is much evidence that downstream information processing in the human brain (i.e., visual and audible “hallucinations”) changes the perception of various external stimuli. For example, it is much easier to hear the phone ring if you are expecting this call. Conversely, if you think about something, then you can not hear (not pay attention) to some external sounds.

Perhaps some cognitive distortions — for example, the illusion of frequency , also known as the Baader-Meinhof phenomenon — may be indirectly related to this interesting feature of the brain’s work - immediately after a person has learned about a new thing or idea, it seems to him begins to appear everywhere, or selective perception .

Scientists have found that these descending expected modulations can occur in a very specific way — similar internal representations can be induced by descending processes without physical stimulation . According to the hypothesis, these generated inside the view interact with the ascending sensory information (vision, hearing) - and thereby modulate the perception. Experts have not yet reached a consensus on how visual and sound images work. Numerous studies on neuroimaging have shown that the primary visual cortex is indeed actively involved in the formation of visual images (the so-called “hallucinations” or “dreams”), using memory and other areas. But the activity of the primary sound cortex in the process of downward sound modulations (sounding “voices”) has not yet been detected.

An international team of scientists from the USA and China contributed to this scientific work. They published an article in which they presented the results of testing a new hypothesis of descending sound images in the brain.

According to this hypothesis, the degree of abstractness of the attribute of perception can determine the level of neural processing and interaction between the upstream information and internal images. In other words, inconsistencies between the visual and auditory areas can be caused by an emphasis on different levels of attributes. For example, in the field of view, recent experiments by behavioral scientists have shown that visual images can affect all levels of perception, from high-level spatial configurations to low-level attributes — such as orientation in space and even muscle control and pupil contraction. But research in the auditory area, as a rule, were focused on the attributes of a higher level.

Specifically, in the course of the experiment, scientists manipulated the level of abstraction of the perceptual attribute in the sound field. First, it allows an electrophysiological study of whether a functionally early perceptual activation is observed without physiological stimulation. Secondly, it is possible to check this way if there is a modulation of the perception of basic sound attributes by reconstructing the early perceptual responses of perception. Simply put, using the methods of magnetic encephalography and electroencephalography, scientists checked how the perception of the loudness of external sounds changes depending on whether the person has mental images.

Experiments have confirmed the assumption that the appearance of a “voice” in the head - it can be reflections, memories, etc., almost any mental activity can be accompanied by a downward sound process - so, sound images in the head really distract a person from perceiving external sound stimuli. In particular, the perceived volume of surrounding sounds is reduced.

“That is, after the imagination of speech in your head, the real sounds that you hear will become softer - the higher the volume in the imagination, the softer will be the perception of surrounding sounds,” explains Tian Xing, associate professor of neural and cognitive sciences at New York University. Shanghai (China). “This is because images and perceptions activate the same auditory areas of the brain.” The previous images have already activated the auditory area, and when the same areas are necessary for the perception of real sounds, they react less actively. ”

A study of scientists clarifies the work of the sensory system of the brain and can help in the treatment of mental disorders that are accompanied by the most active sound hallucinations, such as schizophrenia.

The scientific article "Imaginary Speech Affects the Perceived Loudness of Sound" was published on February 19, 2018 in the journal Nature Human Behavior (doi: 10.1038 / s41562-018-0305-8, pdf ).