This EEG study (n=13) finds that DMT elicited similar brain activation (cortical travelling waves) as visual stimulation does. This provides extra proof for the REBUS-model of psychedelics.
“Psychedelic drugs are potent modulators of conscious states and therefore powerful tools for investigating their neurobiology. N,N, Dimethyltryptamine (DMT) can rapidly induce an extremely immersive state of consciousness characterized by vivid and elaborate visual imagery. Here, we investigated the electrophysiological correlates of the DMT induced altered state from a pool of participants receiving DMT and (separately) placebo (saline) while instructed to keep their eyes closed. Consistent with our hypotheses, results revealed a spatio-temporal pattern of cortical activation (i.e., travelling waves) similar to that elicited by visual stimulation. Moreover, the typical top-down alpha-band rhythms of closed-eyes rest were significantly decreased, while the bottom-up forward wave was significantly increased. These results support a recent model proposing that psychedelics reduce the ‘precision-weighting of priors’, thus altering the balance of top-down versus bottom-up information passing. The robust hypothesis-confirming nature of these findings imply the discovery of an important mechanistic principle underpinning psychedelic-induced altered states.”
This study builds further on earlier brain-imaging (EEG) studies and uses the same data (participants) as Timmermann et al (2019) which studied the brain under DMT influence. The current study particularly looks at ‘travelling wave’ (forward, top-down) “fronts of rhythmic activity which propagate across regions in the cortical visual hierarchy.“
This paper fits with/finds more support for the ‘Relaxed Beliefs Under Psychedelics’ (REBUS) model proposed by co-author of this paper Carhart-Harris and Friston (2019).
“These are the first EEG data on the effects of DMT on human resting state brain activity. In line with prior hypothesis, clear evidence was found of a shift in cortical travelling waves away from the normal basal predominance of backward waves and towards the predominance of forward waves – remarkably similar to what has been observed during eyes-open visual stimulation. Moreover, the increases in forward waves correlated positively with both the general intensity of DMT’s subjective effects, as well as its more specific effects on eyes-closed visual imagery. These findings have specific and broad implications: for the brain mechanisms underlying the DMT/psychedelic state as well as conscious visual perception more broadly.”