Dan Petrescu
PhD Chemistry
BLUE Fellow
Interpreting consciousness through parallels with X-ray crystallography
BLUE Fellow


Guilherme is a PhD student doing research on Theoretical Cosmology, who is mostly interested these days  in Philosophy of Cosmology, Philosophy of the Early Universe and Philosophy of Time. He is originally from Brazil, but moved to Montreal in 2014, and, sadly/excitingly, will be moving away this year to start his first postdoc in Stockholm. He was driven to BLUE because he enjoys interdisciplinary research, and has his own ideas waiting for a space and opportunity to be explored. Dan is a PhD candidate in Chemistry, studying light-matter interactions at the nanoscale with the aim of fabricating materials with exotic optical properties. BLUE appealed to him because it legitimizes side-interests in their own right, and encourages the McGill community to be creative, open-minded, and daring in the pursuit of non-academic endeavors.

Consciousness East and West: A More Complete Approach

"Consciousness is like space." Thus goes one appealing metaphor developed in the East that attempts to broaden the framework of thought around one of the most pressing mysteries of existence: the subjective experience.

Everything that exists inhabits space and is impermanent. Some entities inhabiting space are more fleeting than others, but all are ever-changing, eventually decaying away. Even space itself has potentially emerged from nothing, according to some modern theories in Physics, and might one day no longer be. Moreover, we only observe spatial relations, but never space itself, such that space seems to be just an abstract construct, an extrapolation of the physical world.

Similarly, everything that exists inhabits consciousness and is impermanent. Emotions and thoughts are fleeting, and even seemingly lasting entities such as our sense of self are subject to change. Finally, assuming a materialist perspective, consciousness itself decays away as we die.

Over the last century, Science has developed a powerful technique to investigate material structures that inhabit space: X-ray crystallography. It is our hope that our understanding of this technique may, through analogy, help us better understand consciousness. Briefly, this method of probing spatial relationships relies on the diffraction of high-energy photons (the source) on a crystal (the sample). Once the photons diffract on the sample, they carry forward information about the crystal's three-dimensional structure onto a detector (the screen) in the form of diffraction spots. This procedure is repeated for different orientations of the sample, effectively yielding a series of 2D diffraction patterns that correspond to different 3D orientations of the sample. This collection of 2D patterns carry encoded information about the 3D structure of the sample, which can be mathematically retrieved through an operation known as a Fourier transform. Hence, a virtual representation of the physical 3D structure can be reconstituted via software. We believe that something similar may be taking place in our brains, where a virtual reconstruction of reality occurs through the neuronal circuit equivalent of a Fourier transform. To carry out the analogy further, we need to map the elements introduced above onto elements associated with the conscious phenomenon. We start by assigning the diffraction spots on the screen to the neuronal firings occurring in the brain, implying that the screen itself must be the analog of the brain after a given interaction with world. This leads us to assign the sample as the world, representing everything that is either internal or external to our own bodies. What does the source map onto then? Well, it can be mapped onto the brain state before a given interaction with the world, since that is what defines how the world will be perceived.

Thus, we start with a given brain state that interacts with the world, which produces a new brain state, which then interacts with the world once again, and so on. Notice one fundamental difference between the two pictures of this analogy: in X-ray diffraction, there is a specific directionality with a beginning and an end, while in consciousness, a loop needs to be introduced into the analogy.

Can we also map the 2D patterns on the screen onto something that happens in the brain? We choose to rely on electroencephalography (EEG) waves to complete this analogy. Much like diffraction patterns can be thought of as a collection of diffraction spots, EEG waves can be thought of as collective neuronal firings.

EEG waves are divided in seven groups and are loosely associated with conscious phenomena:

(0.5 - 3 Hz) and  (4 - 7 Hz)—dreamless sleep

(8 - 12 Hz)—drowsiness

(7.5 - 12.5 Hz) and Sensory Motor Rhythm (SMR) (12.5 - 15.5 Hz)—movement

(16 - 31 Hz)—active concentration

(32 - 100 Hz)—unity of conscious perception and REM sleep (in particular, lucid dreaming)

Although more than one type of wave is present in the brain at any given moment, some of them will dominate, and will therefore define a characteristic timescale in the brain—a timescale that can be correlated with our subjective perceptual experience, following a materialist account of consciousness.

Finally, the mapping is completed by assigning the virtual 3D structure of the sample onto the virtual conscious experience. Notice that we lack the analog of the Fourier transform, which would explain how the physical elements in the brain and their objective physical processes produce a subjective experience. This is just another formulation of the hard problem of consciousness, to which we may never have a direct answer.

Let us consider the perception of the flow of time as a short case study, and see whether applying this EEG model of consciousness can support findings where EEG waves are correlated with conscious states. We know that a higher density of high frequency waves can be accommodated in a given period of time, when compared with lower frequency waves. Attentional blink studies support the existence of a unit of conscious time, that dictates what comes into awareness. In light of this, would it be possible that our perception of the flow of time depends on the density of waves? In other words, does the dominant frequency of brain waves dictate our perceptual experiences, like the perception of the passage of time? People exhibiting dominant _-waves are typically in states of deep anesthesia or dreamless sleep and have very little to no awareness of the passage of time. As their dominant EEG waves increase in frequency from _ to _, _, and finally _, subjects tend to report feeling increasingly aware of the passage of time, moving from states of dreaming sleep to lucid dreaming, drowsiness, and finally to the waking state. EEG research has shown that the brain waves of long-time mindfulness meditators shift to higher frequencies while meditators report feeling more aware, supporting the intuitive subjective experience that awareness can become heightened beyond the waking state at rest. In that sense, one moves ever-closer to becoming both physically and spiritually "awakened".

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