Programmable synthetic hallucinations : towards a boundless mixed reality

Abstract

Programmable Synthetic Hallucinations describe the utilization of the bio-physiological mechanics of hallucination generated in the human brain to display virtual information directly in the visual field. Science fiction films, television shows, and video games have trained audiences to think of holograms as luminous volumetric images that float registered in the viewer's 3D space and require no special glasses or optics to see or interact with them. The ability of users to interact with a floating aerial lightfield without the use of face-worn binocular optics is a difficult challenge and one in which a hallucinatory experience offers a solution. While we do not have the ability to activate individual neurons to recreate an neuro-electrical pattern indiscernible from the perception of reality, this dissertation shows that creating phosphenes within the visual field via the magnetic stimulation of neurons in the visual cortex is a viable first step.

By electrically stimulating the cells in the hypercolumns of V1, one can induce the perception of a pixel of light within the visual field of a user. These magnetophosphenes are visual perceptions described as luminous shapes, which can be created by time-varying magnetic fields. These change the membrane potential and trigger an action potential directly in neurons of the visual cortex. Previous TMS studies have shown evocation of phosphenes in a binary manner, with subjects reporting the presence or absence of a phosphene but not targeted to a specific location. However, to date, no information or example has been found indicating the use of cortical phosphenes, induced magnetically or otherwise, in performance or public display. Presently, commercial transcranial magnetic stimulators can only be focused to an area approaching one square centimeter, a single output channel, and require manual placement of the coil apparatus.

Novel coil designs became a central focus of this research. Further work increased the number of output channels, embedding them in a wearable apparatus with a multichannel array of induction coils. Clinical trials were undertaken at MIT's Clinical Research Center. We were able to evoke visual phenomena in 11 out of 16 test subjects in a known, targeted location. The induced magnetophosphenes were noted above the noise floor of naturally occurring retinal phosphenes and were statistically verified to be a result of the system being tested.