Consciousness feels whole. That is to say that the various sensory experiences that our brains process in parallel feel like one coherent thing, our own individual consciousness. However, the electrical activity generated by different sensory experiences are largely segregated to different parts of the brain and it is possible to turn them off selectively. For instance, form and motion are represented by different parts of the visual cortex. By using a technique such as TCMS, it would be possible to eliminate sensations of motion in an image while retaining static vision. This would no doubt be a very strange state to be in. There are also many pathologies, induced by head injury or otherwise, that produce abnormal combinations of sensory data and qualities of consciousness in general (Dr. Oliver Sacks has written extensively on this topic).
On the other hand, different cortical sensory areas are highly connected to each other; this is at least partly why our sensations feel so unitary. This means that simply hearing something move or feeling the touch (ref. 1) of something moving can produce measurable responses in the parts of the visual cortex most sensitive to movement. Some recent research has gone farther than this, since, as the authors of this work (ref. 2) point out: it is no surprise that the feeling of something moving can elicit such a reaction because merely imagining motion can have the same effect. These experiments demonstrate that a highly specialized area of the visual cortex called MST is sensitive to "vibrotacticle" stimuli: those incongruent with motion.
Because consciousness is often thought of as an emergent property of our massively interconnected system of neurons, understanding interactions between parts of the brain at many different scales (from single neurons to large collections or areas as in this case) is integral to understanding how this efflorescence works. The work highlighted here is one step in that direction.
References
- Hagen MC, Franzen O, McGlone F, Essick G, Dancer C, Pardo JV (2002) Tactile motion activates the human middle temporal/V5 (MT/V5) complex. Eur. J. Neurosci. 16:957–964.
- Beauchamp MS, Yasar NE, Kishan N, Ro T. (2007) Human MST but not MT responds to tactile stimulation. J. Neurosci. 27(31):8261-8267
1 comment:
James,
This strikes me as exactly the kind of thing I find so exciting to have someone like you explain to me because you do it with such clarity and simplicity and so elegantly. Love this.
Mama
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