Conference Agenda

After death experiences (ADEs), in which individuals perceive the presence of a deceased loved one, are reported by 30-60% of the global population.  Despite their prevalence, ADEs remain understudied in experimental research. To better understand the mechanisms of ADEs we leveraged methods and procedures that can experimentally induce felt presences, under controlled experimental settings. This mixed-methods study investigates these experiences by: using a robotic system to induce presence hallucinations through sensorimotor stimulation; collecting neuropsychological data; and conducting semi-structured interviews about the ADEs and induced presences (i.e., Blanke et al., 2014; Bernasconi et al., 2021). Critically, our approach enables the integration of subjective experiences with behavioral data.  In a pilot study (N=11), we found that bereaved individuals (diverse in upbringing and beliefs) who interacted with the deceased's physical body were numerically less likely to report ADEs compared to those who did not. Additionally, bereaved participants were numerically more likely to report experimentally induced presence hallucinations using the robotic system (i.e. Blanke et al., 2014), compared to non-bereaved controls. Notably, one participant reported an ADE during the robotic manipulation, suggesting that such specific ADEs can be experimentally induced alongside presence hallucinations that are not identified as deceased. We propose that ADEs can best be understood by examining evolutionary, interpersonal/social, and sensorimotor factors. These findings advance our understanding of consciousness and grief. Further research is ongoing to strengthen these initial findings and explore the neural and psychological dimensions of experimentally-induced ADEs.

Jhana meditation is an advanced absorptive practice in Theravāda Buddhism, characterized by deep concentration, sensory attenuation, and bliss. Unlike other states of consciousness, Jhana exhibits high arousal with minimal mental content. While traditionally cultivated for insight, its neurophysiological mechanisms remain underexplored, with previous research limited to single-case reports and poorly controlled studies.

To address these limitations, we conducted a controlled 32-channel EEG within-subject study with N = 10 expert meditators (7 female, 3 male; mean age = 61.3, SD = 12.1) from the Pa-Auk Sayadaw lineage, a tradition known for its precise approach to Jhana practice. Each participant was recorded across four days during a 10-day silent retreat, practicing both Jhana and mindfulness of breathing (control).

In line with our pre-registered hypothesis, Jhana meditation was associated with significantly higher cortical entropy (Lempel-Ziv complexity: β = 0.085, p < 0.001; sample entropy: β = 0.186, p < 0.001; spectral entropy: β = 0.067, p < 0.001), indicating greater neural complexity and flexibility. Further analyses revealed increased scale-free dynamics and self-organized criticality, including avalanche criticality (χ² test: p = 0.0043), long-range temporal correlations (DFA 30–45 Hz: p = 0.0005), and a steeper aperiodic spectral slope (FOOOF: p = 0.0095). Furthermore, entropy levels correlated positively with self-reported depth of the Jhana state (p=0.0161) and cognitive flexibility as measured by a divergent thinking task (p = 0.0271). These findings suggest that Jhana meditation enhances critical-like and self-organizing dynamics in brain activity, offering new insights into meditation-induced shifts in brain dynamics.

Altered states of consciousness inducing substances like ketamine are known to have long-lasting pro-hedonic effects and modify neuronal information integration. However, the exact relationship between these effects remains elusive. In this placebo-controlled crossover fMRI study (N=32), we investigated whether i) peak hedonic experiences in response to music require increased information integration, as they emerge from dynamic affective and physiological processes, ii) ketamine’s [0.5mg/kg] subacute pro-hedonic effects are driven by its impact on the brain’s information integration during rest, and iii) this modulation of ongoing baseline processes influences the relationship between information integration and subjective experiences during music listening. Using an established measure of neuronal information integration (ΦWMS), we show that stronger hedonic experiences indeed significantly induced local increases in information integration, spatially linked to norepinephrine transporter density. Furthermore, ketamine massively decreased information integration during rest, which in turn affected stimulus perception. More specifically, the same level of neuronal integration for a given stimulus resulted in a substantially heightened subjective phenomenological experience depending on ketamine’s reduction of baseline integration. Thus, we propose that, much like a candle shining brighter in a dark room, ketamine’s drastic reduction in baseline integration (darkening the room) amplifies the link between stimulus-driven integration (candle light) and phenomenological experience, ultimately intensifying the subjective experience (a brighter perceived light). These findings demonstrate that 1) information integration plays a crucial role in the phenomenology of hedonic experiences and 2) ketamine may facilitate its lasting subacute hedonic effects by modulating neuronal information integration in the brain.

Psychedelics dramatically alter our conscious perception, however, the underlying neural mechanisms are unclear. An increasing number of human studies have been studying how psychedelics affect the brain using non-invasive methods, but the effects on single neurons in the primate brain are unknown. Here, we present an investigation into the neural mechanisms of how psychedelics shape perception through ultra-high-throughput recordings of hundreds of single neurons in the visual cortex of a non-human primate.

We performed neural recordings from multiple nodes of the visual hierarchy in face patches in inferotemporal cortex using novel NHP Neuropixels probes under psilocybin and DOI. We paired these recordings with electrical microstimulation of either at a lower-level or higher-level node. Together, these experiments allow us to dissect the effects of psychedelics on bottom-up processing of visual input versus top-down feedback, which is believed to reflect the brain’s internal model and expectations about the world.

Preliminary results suggest that psychedelics increase neural activity, in particular in long waveform, putative pyramidal cells, as well as in layer 1, the pre-dominant input layer of top-down feedback from higher-level cortex. On the other hand, neural response variability is strongly reduced. Connected areas that are strongly coupled in the sober state become decoupled under psychedelics. Effects of feedback, induced by microstimulation, are strongly reduced by psychedelics. Taken together, psychedelics may provide a useful turn knob for altering the balance between feedforward and feedback signaling in the brain, offering a possible explanation for their promising therapeutic effects for a variety of mental disorders.