A Preconscious Neural Mechanism of Hypnotically Altered Colors: A Double Case Study

Abstract

Hypnotic suggestions may change the perceived color of objects. Given that chromatic stimulus information is processed rapidly and automatically by the visual system, how can hypnotic suggestions affect perceived colors in a seemingly immediate fashion? We studied the mechanisms of such color alterations by measuring electroencephalography in two highly suggestible participants as they perceived briefly presented visual shapes under posthypnotic color alternation suggestions such as “all the squares are blue”. One participant consistently reported seeing the suggested colors. Her reports correlated with enhanced evoked upper beta-band activity (22 Hz) 70–120 ms after stimulus in response to the shapes mentioned in the suggestion. This effect was not observed in a control condition where the participants merely tried to simulate the effects of the suggestion on behavior. The second participant neither reported color alterations nor showed the evoked beta activity, although her subjective experience and event-related potentials were changed by the suggestions. The results indicate a preconscious mechanism that first compares early visual input with a memory representation of the suggestion and consequently triggers the color alteration process in response to the objects specified by the suggestion. Conscious color experience is not purely the result of bottom-up processing but it can be modulated, at least in some individuals, by top-down factors such as hypnotic suggestions.

Synaesthesia-type associations and perceptual changes induced by hypnotic suggestion

“…Two participants from this group (>9 HGSHS:A score) responded to the negative visual hallucination item and were invited to participate in the experiment. An additional two, highly hypnotizable individuals were invited to participate based on previous experience of their responsiveness to visual hallucination suggestions 23 . All those who scored <4 in HGSHS:A scored 4 or less in SHSS:C. Four were invited to participate in the experiment, with preference for (higher) age, since HG included only one participant under 30 years.…”

“…Sociocognitive theories claim that this experience is not similar to synaesthesia and that conscious recognition of the target inducer (as a square) is first required, followed by cognitive effort to imagine it being red. In contrast, AST predicts that an automatic association emerges and that some highly hypnotizable individuals should even be able to perceive the inducer and concurrent simultaneously, just as some genuine synaesthetes 23 , 26 . Simultaneous synaesthetic experience should make naming the targeted symbol (square) “red” just as easy, requiring the same time and involving the same eye behaviour as naming a non-targeted symbol by its veridical colour.…”

“…According to the feedback model , synaesthesia-like experiences can be artificially created by training 22 or hypnosis 8 . In hypnosis research, one finds a comparable model 4 , 23 proposing that hypnotically induced colour alterations can occur if suggestions modulate the recurrent interactions 4 that generate the final conscious perception. Meanwhile, sociocognitive theories argue that all hypnotically induced visual experiences are the result of goal-directed mental imagery 24 and can equally well be experienced without hypnosis.…”

Hypnosis in palliative care: from clinical insights to the science of self-regulation

“…In other words, the content of a suggestion can lead individuals to achieve a variety of very precise hypnotic responses, as a function of the desired outcome. Empirical evidence demonstrates this precision across many sensory domains (56,70,71,135,136), cognitive processes (125,137), and ideomotor processing (115) These findings demonstrate that response precision is a core feature of hypnosis; suggestions can lead to great specificity (138).…”

The Effects of Hypnosis and Hypnotic Suggestions on the Mismatch Negativity in Highly Hypnotizable Subjects

“…In the visual modality, some findings obtained with highly hypnotizable subjects also suggest that by using hypnotic suggestions, it is possible to influence preconscious or highly automatized information processing such as color perception Koivisto, Kirjanen, Revonsuo, & Kallio, 2013), but possibly only with some of the most hypnotizable individuals (Kallio, Koivisto, & Kaakinen, 2017). Although the auditory and visual information processing systems are differently structured and located in the human brain, there may also be similarities in the effects of hypnotic suggestions between them.…”