Strength of prefrontal activation predicts intensity of suggestion-induced pain.

Suggestion, a powerful factor in everyday social interaction, is most effective during hypnosis. Subjective evaluations and brain-imaging findings converge to propose that hypnotic suggestion strongly modulates sensory processing. To reveal the brain regions that mediate such a modulation, we analyzed data from a functional-magnetic-resonance-imaging study on hypnotic-suggestion-induced pain on 14 suggestible subjects. Activation strengths in the right dorsolateral prefrontal cortex (DLPFC) during initiation of suggestion for pain correlated positively with the subjective intensity of the subsequent suggestion-induced pain, as well as with the strengths of the maximum pain-related activation in the in the secondary somatosensory (SII) cortex. Furthermore, activation of the insula and the anterior cingulate cortex predicted the pain-related SII activation. The right DLPFC, as an area important for executive functions, likely contributes to functional modulation in the modality-specific target areas of given suggestions.

Brain correlates of subjective reality of physically and psychologically induced pain.

Meaningful behavior requires successful differentiation of events surfacing from one's mind from those arising from the external world. Such judgements may be especially demanding during pain because of the strong contribution from psychological factors to this experience. It is unknown how the subjective reality of pain (SRP) is constructed in the human brain, and neuronal mechanisms of the subjective reality are poorly understood in general. To address these questions, 14 suggestion-prone healthy subjects rated reality of pain that was induced either by laser pulses to the skin or by hypnotic suggestion during functional MRI. Both pain states were associated with activation of the brain's pain circuitry. During laser stimulation, the sensory parts of this circuitry were activated more strongly, and their activation strengths correlated positively with the SRP. During suggestion-induced pain, the reality estimates were lower and correlated positively with activation strengths in the rostral and perigenual anterior cingulate cortex and in the pericingulate regions of the medial prefrontal cortex; a similar trend was evident during laser-induced pain. These findings support the view that information about sensory-discriminative characteristics of pain contributes to the SRP. Differences in such information between physically and psychologically induced pain, however, could be quantitative rather than qualitative and therefore insufficient for judging the reality of pain without knowledge about the source of this information. The medial prefrontal cortex is a likely area to contribute to such source monitoring.

Different brain activation patterns during production of animals versus artefacts: a PET activation study on category-specific processing.

To study neural correlates of category-specific processing, we measured relative cerebral blood flow changes by PET (oxygen-15) in young healthy subjects while they produced exemplars of animals or artefacts to written subcategory prompts. In comparison to a baseline (word reading), production of animal names elicited increased rCBF in the right inferior temporal region. This fits to recent lesion data on semantic impairment with animals, as well as imaging data on object recognition and semantic retrieval. In our study, it may represent an involvement of visual imagery in generation of animal names. In contrast, production of artefact names elicited increased rCBF in frontoparietal regions previously related to attention and mental effort.