Stepping through the door
Picture the calm surface of a bathtub full of water. Now take a baseball sized rock and drop it into the tub and watch the unfolding orchestra of undulating waves play out. If you observe closely you’ll note a first series of waves emanating outward and hit the edges of the tub creating new waves that then bounce back across the surface. This action repeats itself on and on until a wildly complex interplay of undulating waves produces a chaotic mass of movement. This instant where wave upon wave dance together is an important image because it reflects what might actually happen in our own brains.
The crucial point is that it is just this type of complex undulating interplay between neurons and brain centers that seem to lift sensory stimuli to the level of awareness and beyond. In essence, it seems that the path to consciousness is not really a path, but more a simultaneous chorus of neuronal interactions where the sum total of these effects- given enough time- provide the crucial stepping stone to awareness.
In the brain, if a stimulus input is strong enough to “awaken” a certain threshold of neurons they can, for example, fire synchronously creating oscillating waves of stimuli that eventually creates the pattern necessary for awareness. These firing rates (Hz) can vary widely and it seems only a narrow range of neuronal activity favors the appearance of consciousness.
Generally speaking neuronal firing rates range from 1 Hz to 250Hz. Lower ranges between 1-2 Hz (delta waves) reflect deep sleep, 4-8Hz (theta) drowsiness, 8-12 Hz (alpha) relaxed awareness, and 18-30 Hz diffuse attentive awareness. On top of these general oscillating patterns, the brain also exhibits smaller areas of intense activity that average 40 Hz and are called gamma rate oscillations- these are associated mostly with “consciousness”.
More intense the firing involves more brain modules and reflects a “fuller” experience- but up to a point. It seems that gamma rate oscillations provide just the right level of neuronal firing in order to reach that critical threshold- much like finding the right combination for the Stargate (need to watch the movie if you haven’t!).
Francis crick and Christof Koch believed that this gamma oscillation represented consciousness “per se” but over the years numerous studies of the 40Hz= consciousness theory have revealed a deeper and more profound connection.
Rita Carter notes “40 Hz activity marks information processing that has the potential of becoming conscious, providing it is “doubled up” or re-represented at a higher level. So, for example, an island of 40Hz firing in the sensory cortex is the first level representation of a sensory event which will be one of the “contents” of consciousness if- and only if- it triggers further 40 Hz activity in a part of the brain which produces higher-order or “whole” perceptions and/or concepts.”
In other words, as previously mentioned, it is the “dancing” interaction between the lower and higher regions of the brain that seems to give rise to consciousness- it is not a bottom to top sequence. Carter adds “Conscious perception, then, is not of these first-order representations. Yet nor does it seem to be just of the higher-order re-representations that follow. The “knowing of knowing” requires both the higher order representation and the lower order representation to be present in the brain at the same time, or at least close enough in time for them to merge.”
Of note she states that time is a part crucial of this process “Whereas a simple image becomes conscious in about 200 milliseconds, complex images take almost half a second to emerge.” Additionally there is a correlation between the complexity of consciousness and where in the brain it might emerge. According to Carter “You would also expect to see a parallel between the level of complexity of a “piece” of consciousness, and its place in the construction chain. And you do. Roughly, the more complex the perception, the further forward in the brain the neural activity relating to it extends.”
This time dependant process tied to all the described interplay implies that the “mind” is not one region or entity. This solidifies the fact that the workings of the mind obey laws of nature- like anything else. It plays out a temporally dependant to and fro feedback sequence of neuronal oscillations that eventually trip into consciousness.
One might ask, so what? Well, for one thing, if true (as observations indicate) it pretty much makes dualist mind/body theories untenable. If that weren’t enough, it also strikes at the heart of some of the “quantum consciousness” hubris as well. There are no detectable “non local” - no instantaneous- connections between minds. There is an incredibly complex symphony of activity that does occur, but it all happens inside your own skull.
These discoveries don’t make the phenomenon of consciousness any less sublime and beautiful. On the contrary, the truth is more beautiful than anything we could ever make up.
Ref:
Carter, R. Exploring Consciousness. Univ of
No comments:
Post a Comment