Hypnotic suggestions can prompt conscious hallucinations

Hypnotic suggestions can prompt conscious hallucinations

Researchers have discovered that "hypnotic suggestions" - instructions that encourage a response from those under hypnosis - may trigger automatic cues, such as for how we perceive color.

Researchers from Finland and Sweden conducted two studies revealing the brain's oscillatory (repetitive variation) activity using EEGs in two participants under hypnosis.

In the first study published in the journal PLOS One, researchers measured the response of two female patients as they were briefly shown a series of three shapes - squares, triangles or circles - in either red or blue.

The participants, who were proven to enter in and out of hypnosis with a one-word cue, were given a suggestion under hypnosis that certain shapes were always the same color. They told the participants "all squares are always red."

The participants were then required to carry out the test when in a "stimulus block" (fully out of the hypnotic state).

'High-frequency brain activity' recorded

Results of the study showed that participant number one reported experiencing a change in color immediately after a suggested shape appeared on the screen - for example, seeing a red square when in reality it was blue.

During this experience, the researchers discovered that the brain had high-frequency activity a tenth of a second after the appearance of the shape, which only appeared in response to the shapes suggested.

The second participant did not experience a change in color following suggested shapes but instead reported a "peculiar feeling" as she saw one. The participant told the researchers: "Sometimes I saw a shape that was red but my brain told me it had a different color."

The researchers explained that the enhanced oscillatory brain activity is proposed to reflect comparison of input to memory representations automatically. They added that in this case, the hypnotic suggestion that "all squares are red" triggered a memory trace that was activated automatically as a square was shown on the screen.

The study authors said that for participant one, this process must have been strong enough to eliminate the real color of the square, and that the matching of the colors "must have occurred pre-consciously" due to the immediacy and effect of the color change.

In a separate study, published in the journal International Journal of Clinical and Experimental Hypnosis, participant one's responses to behavioral data were examined. This included response times and accuracy of color recognition.

The results of this study supported the previous results, as a hypnotic suggestion affected the participant's color perception of targeted objects prior to consciousness of them. Additionally, the participant could not change her color perception of these objects again without being given hypnotic suggestions.

'Memory trace' can be created under hypnosis

The study authors said that these results reveal that under hypnosis, it is possible to create the experience of hallucinations.

A memory trace can be created under hypnosis, which can influence a preconscious stage of visual processing a tenth of a second after the appearance of a visual target, the researchers said.

They added:

The effects of the suggestions must rely on brain structures and functional connections that are available in normal brain."

"Therefore our study suggests also that normal conscious color experience is not purely the result of bottom-up processing but top-down factors can have a modulatory effect on it."

They concluded that these findings may play important roles in psychology and neuroscience, particularly when studying memory, consciousness and visual perception.

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