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Friday, January 18, 2013

Are Vision and Consciousness Intimately Related?

Are Vision and Consciousness Intimately Related?
In my article on brain waves and consciousness I looked at some research associating gamma wave activity with consciousness. This is, however, a controversial area in that other researchers have found that such gamma activity is also correlated with eye movements known as saccades: these are the small eye movements that the brain edits out so that we do not perceive the world as a blur as we switch focus. So, are brain gamma waves merely a byproduct of saccadic movements or are they correlated with consciousness or, potentially, both?

You can follow the relevant articles and the subsequent discussions at 
Neuron. The situation is summed up as follows:"In summary, Tallon-Baudry suggests that there are two separate responses: one related to microsaccades and the other to neural gamma oscillations. These two responses seem, however, to occur at the same latency (200-300 ms), the same distribution (occipito-parietal with nose reference), the same frequency spectrum (peak at 30-40 Hz with a broadband tail) and could be affected by the same cognitive manipulations (e.g. familiarity enhances both). While we [Yuval-Greenberg at al.] cannot exclude such coincidence, [...] our paper implies that studying the contribution of a neural component to [the gamma-band] requires at least the explicit consideration of small saccades and control of their effects. In our hands, this control seems to abolish the transient [gamma-band] signal. " The microsaccades theory is that the eyes - more specifically the eye muscles - act as dipoles which create an electromagnetic field as they oscillate around the gamma frequency range. 

What I actually wanted to say here was on a more personal basis; an experience that leads me to think that perhaps both theories are right. In my 
brain-crash article I describe my experience of regaining consciousness after a syncope. In my attempt to render the experience in meaningful words I explained that the state of unitary consciousness was devoid of any inputs: I could not feel, or hear, or smell, or taste, nor was there any thinking such as our internal chatter or images. However, you will note that there was some kind of visual ground state. The above research articles then made me think: what would it mean not to see? It is simple enough to think of not hearing anything or not feeling anything, but what would it feel like to not seeanything? Seeing darkness is not the same as seeing nothing. Seeing some interference pattern generated by an absence of signals is also not the same as seeing nothing. There is a state in which we see nothing: sleeping. But that is also a state of unconsciousness.

Based on little more than my own experience I just wanted to throw the question open: is vision intimately related to consciousness? Do the eyes somehow switch on consciousness? Even REM sleep can be thought of as closer to being conscious than unconscious and is itself associated with eye movements. 

My guess is that similar research on blind people may yield some answers. Do blind people still have microsaccades? Is there a difference in brain waves between people who are blind but still have eyes compared to those who have lost one or more eyes through accidents or tumors? Any references appreciated.

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