University of Tokyo
Turing Test for Machine Consciousness and the Chaotic Spatiotemporal Fluctuation Hypothesis
Wednesday 30th of April 2014 at 12:00pm
Evans Room 560
I propose an experimental method to test various hypotheses on consciousness. Inspired by Sperry's observation that split-brain patients possess two independent streams of consciousness, the idea is to implement candidate neural mechanisms of visual consciousness onto an artificial cortical hemisphere and test whether subjective experience is evoked in the device's visual hemifield. In contrast to modern neurosynthetic devices, I show that mimicking interhemispheric connectivity assures that authentic and fine-grained subjective experience arises only when a stream of consciousness is generated within the device. It is valid under a widely believed assumption regarding interhemispheric connectivity and neuronal stimulus-invariance. (I will briefly explain my own evidence of human V1 not responding to changes in the contents of visual awareness )
If consciousness is actually generated within the device, we should be able to construct a case where two objects presented in the device's visual field are distinguishable by visual experience but not by what is communicated through the brain-machine interface. As strange as it may sound, and clearly violating the law of physics, this is likely to be happening in the intact brain, where unified subjective bilateral vision and its verbal report occur without the total interhemispheric exchange of conscious visual information.
Together, I present a hypothesis on the neural mechanism of consciousness, “The Chaotic Spatiotemporal Fluctuation Hypothesis” that passes the proposed test for visual qualia and also explains how physics that we know of today is violated. Here, neural activity is divided into two components, the time-averaged activity and the residual temporally fluctuating activity, where the former serves as the content of consciousness (neuronal population vector) and the latter as consciousness itself. The content is “read” into consciousness in the sense that, every local perturbation caused by change in the neuronal population vector creates a spatiotemporal wave in the fluctuation component that travels through out the system. Deterministic chaos assures that every local difference makes a difference to the whole of the dynamics, as in the butterfly effect, serving as a foundation for the holistic nature of consciousness. I will present data from simultaneous electrophysiology-fMRI recordings and human fMRI  that supports the existence of such large-scale causal fluctuation.
Here, the chaotic fluctuation cannot be decoded to trace back the original perturbation in the neuronal population vector, because initial states of all neurons are required with infinite precision to do so. Hence what is transmitted over the two hemispheres are not "information" in the normal sense. This illustrates the violation of physics by the metaphysical assumption, "chaotic spatiotemporal fluctuation is consciousness", where unification of bilateral vision and the solving of visual tasks (e.g. perfect symmetry detection) are achieved without exchanging the otherwise required Shannon information between the two hemispheres.
Finally, minimal and realistic versions of the proposed test for visual qualia can be conducted on laboratory animals to validate the hypothesis. It deals with two biological hemispheres, which we know already that it contains consciousness. We dissect interhemispheric connectivity and form instead an artificial one that is capable of filtering out the neural fluctuation component. A limited interhemispheric connectivity may be sufficient, which would drastically discount the technological challenge. If the subject is capable of conducting a bilateral stimuli matching task with the full artificial interhemispheric connectivity, but not when the fluctuation component is filtered out, it can be considered a strong supporting evidence of the hypothesis.
1.Watanabe, M., Cheng, K., Ueno, K., Asamizuya, T., Tanaka, K., Logothetis, N., Attention but not awareness modulates the BOLD signal in the human V1 during binocular suppression. Science, 2011. 334(6057): p. 829-31. 2.Watanabe, M., Bartels, A., Macke, J., Logothetis, N., Temporal jitter of the BOLD signal reveals a reliable initial dip and improved spatial resolution. Curr Biol, 2013. 23(21): p. 2146-50.
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