What happens in the brain of meditators when perception changes but not the stimulus?

Abstract

During the observation of an ambiguous figure our perception alternates between mutually exclusive interpretations, although the stimulus itself remains unchanged. The rate of these endogenous reversals has been discussed as reflecting basic aspects of endogenous brain dynamics. Recent evidence indicates that extensive meditation practice evokes long-term functional and anatomic changes in the brain, also affecting the endogenous brain dynamics. As one of several consequences the rate of perceptual reversals during ambiguous figure perception decreases. In the present study we compared EEG-correlates of endogenous reversals of ambiguous figures between meditators and non-meditating controls in order to better understand timing and brain locations of this altered endogenous brain dynamics. A well-established EEG paradigm was used to measure the neural processes underlying endogenous perceptual reversals of ambiguous figures with high temporal precision. We compared reversal-related ERPs between experienced meditators and non-meditating controls. For both groups we found highly similar chains of reversal-related ERPs, starting early in visual areas, therewith replicating previous findings from the literature. Meditators, however, showed an additional frontal ERP signature already 160 ms after stimulus onset (Frontal Negativity). We interpret the additional, meditation-specific ERP results as evidence that extensive meditation practice provides control of frontal brain areas over early sensory processing steps. This may allow meditators to overcome phylogenetically evolved perceptual and attentional processing automatisms.

Novel method to measure temporal windows based on eye movements during viewing of the Necker cube

“…a dissociation between eye movements and perceptual awareness [12]. Regarding studies on bistable stimuli, our results are consistent with those reported by Brascamp et al (2015) [5], or [36] who showed in fMRI or EEG evidence of alternations that occur faster than the behavioral responses. As suggested by these authors sensory alternations may occur without reaching consciousness.…”

Neural correlates of nonjudgmental perception induced through meditation

“…A similar conclusion was reached in another recent study of perceptual bistability in the LTMs, where authors observed the presence of a frontal component of the event-related potential exclusively in the LTMs (and not in the CTL) group. 46 They interpreted the extra frontal processing in the LTMs as reflecting extra higher order/metacognitive processing that comes from being in a relatively defused state from the sensory stimulus, which is similar to our interpretation. Furthermore, their frontal component may have a functional link to the positive correlation between change in mixed percepts and gamma synchrony we observed over right frontal-parietal channels in our exploratory analysis as well.…”

Time consciousness: the missing link in theories of consciousness

“…The orthodox view in the cognitive neurosciences is that time consciousness extends over a duration between a few hundred milliseconds and a few seconds over what is otherwise called the “experienced moment” or “subjective present” ( Pöppel 1997 ; Wittmann 2011 ; Kent 2019 ). Experimental findings discussed in the above reviews indicate that the perception of external events is automatically segmented into units with a duration of a few seconds such as when listening to sequences of beats, when viewing ambiguous figures, or when viewing distorted naturalistic visual sequences ( Nakajima et al 1980 ; Fairhall et al 2014 ; Wang et al 2016 ; Kornmeier et al 2019 ). These special stimulations are supposed to be limit cases of general processing mechanisms which temporally structure all of our perception and action ( Pöppel 1997 ).…”