Volatile anesthetics like isoflurane may cause unconsciousness by binding to microtubules (MTs) inside neurons and dampening their quantum optical effects. In male rats injected with the MT-stabilizing drug epothilone B (epoB), loss of righting reflex under 4% isoflurane took an average of 69 seconds longer than in rats given a placebo. The difference was statistically significant with a large effect size (Cohen's d = 1.9) and could not be explained by tolerance from repeated anesthetic exposure. This supports the idea that consciousness arises from quantum physical states in neural microtubules, as proposed in the orchestrated objective reduction (Orch OR) theory.
Recent experimental evidence indicates that inhalational anesthetics target intraneuronal microtubules, supporting the hypothesis that consciousness arises from a collective quantum state of microtubules, as predicted by the Orchestrated Objective Reduction theory. Evidence also shows functionally relevant quantum effects in microtubules at room temperature and a macroscopic quantum entangled state in the living human brain correlated with conscious state and working memory. The quantum model makes panprotopsychism a viable solution to the hard problem by solving the binding problem, but raises an epiphenomenalism problem. The author proposes the quantum approach can solve this, and the Orch OR theory accounts for nonalgorithmic understanding and the psychological arrow of time.
Stabilizing brain microtubules can make animals resistant to anesthesia. Mice given a single dose of a microtubule-stabilizing drug showed a 29-second delay in losing consciousness under isoflurane the next day. This significant within-subject effect, with a Cohen's d of 0.8, suggests that anesthetic binding to microtubules contributes to unconsciousness. This supports theories proposing consciousness arises from quantum states within these neural structures, and hints at potential sex differences in anesthetic mechanisms.
Active inference, a framework for modeling how sentient agents optimize behavior and learning, requires probabilistic computations including a path integral over future trajectories. Classical biophysical neural models like Hodgkin-Huxley neurons are unlikely to perform these computations quickly enough in realistic contexts. The path integral underlying active inference is mathematically equivalent to quantum dynamics, suggesting a quantum model provides a natural mechanistic implementation. This first of two companion papers argues that classical neurons are insufficient for temporally deep active inference, while a quantum model offers a biologically plausible alternative. The second paper reviews evidence supporting the Orch OR quantum theory of consciousness in microtubules, explaining discrete perceptual inference cycles.
Classical neural models for conscious active inference lack biological plausibility because they cannot explain the discrete, non-overlapping cycles of perceptual inference observed in the brain. The Orchestrated Objective Reduction (Orch OR) theory of consciousness, which treats consciousness as a collective quantum property of microtubules inside neurons, naturally accounts for these cycles. Evidence for this quantum model includes room-temperature quantum effects in microtubules, microtubule resonances that control neuron firing, volatile anesthetics causing unconsciousness by targeting microtubules, and direct biophysical evidence of a macroscopic entangled state in the living human brain. Microtubules thus provide a biologically specific substrate for implementing conscious active inference.