RESUMO
OBJECTIVE: During hypnosis, significant changes in the BOLD signal associated with the anterior default mode network (DMN) and prefrontal attentional systems have been reported as evidence of dissociation defined since Charcot. However, it remains uncertain whether these changes are mainly attributable to the hypnotic state per se or to the target suggestions used to verify subject's state during neuroimaging studies. The aim of the present study is to evidence the brain in hypnosis, contrasting the common resting state versus neutral hypnosis (hypnosis in the absence of target suggestions). METHODS: Twenty-four healthy right-handed volunteers (age 28.3 y.o., 12 females) rated moderate hypnotic responsiveness underwent resting state fMRI at 3.0 T in two sessions, once in neutral hypnosis and the other in the common resting state. Each subject's functional data were analyzed for low-frequency BOLD signal correlations seed-to-voxel for the whole brain in the first-level analysis, and seed-to-voxel in a second-level analysis to estimate group results using seeds for five resting state networks: the default mode (DMN), the central executive (CEN), the salience (SaN), the dorso-lateral attention (DAN), and the sensorimotor (SMN) networks. RESULTS: In general, all network maps of the hypnotic condition presented higher connectivity than those of the resting condition. However, only contrasts for the DAN, SaN, and SMN were statistically significant, including correlated out-of-the-network regions. CONCLUSION: Parietal and occipital regions displayed increased connectivity across networks, implying dissociation from the frontal cortices. This is the first fMRI intrinsic study of hypnosis without target suggestion.
Assuntos
Hipnose , Imageamento por Ressonância Magnética , Feminino , Humanos , Adulto , Imageamento por Ressonância Magnética/métodos , Mapeamento Encefálico/métodos , Encéfalo/diagnóstico por imagem , Hipnóticos e SedativosRESUMO
The present experiment was designed to test if sustained attention directed to the spontaneous sensations of the right or left thumb in the absence of any external stimuli is able to activate corresponding somatosensory brain areas. After verifying in 34 healthy volunteers that external touch stimuli to either thumb effectively activate brain contralateral somatosensory areas, and after subtracting attention mechanisms employed in both touch and spontaneous-sensation conditions, fMRI evidence was obtained that the primary somatosensory cortex (specifically left BA 3a/3b) becomes active when an individual is required to attend to the spontaneous sensations of either thumb in the absence of external stimuli. In addition, the left superior parietal cortex, anterior cingulate gyrus, insula, motor and premotor cortex, left dorsolateral prefrontal cortex, Broca's area, and occipital cortices were activated. Moreover, attention to spontaneous-sensations revealed an increased connectivity between BA 3a/3b, superior frontal gyrus (BA 9) and anterior cingulate cortex (BA 32), probably allowing top-down activations of primary somatosensory cortex. We conclude that specific primary somatosensory areas in conjunction with other left parieto-frontal areas are involved in processing proprioceptive and interoceptive bodily information that underlies own body-representations and that these networks and cognitive functions can be modulated by top-down attentional processes.