This is a very cool post from a very cool blog (On the Human) - Jesse Prinz attempts to narrow down the types of qualia of which we can be conscious - and how that process might look inside the brain. I don't really agree with Prinz, but I always enjoy reading what other people think about the "hard problem" of consciousness.
There is much more - go read the whole post.by Jesse Prinz
City University of New York, Graduate Center1. Introduction: The Battle of the Bulge
In trying to develop a theory of how consciousness arises in the brain, it is important to begin with an account of which kinds of brain events can be conscious. Once we know which brain events are conscious, we can investigate what distinguishes them from those that are not. Pretty much everyone agrees that some activities in the brain are never conscious. For example, it would be hard to find researches who think there can be conscious events in the cerebellum. Most researchers nowadays also deny that there can be conscious events in subcortical structures, though there is an occasional plea for the thalamus (Baars) or the reticular formation (Damasio). But what about the neocortex? Is any activity in that folded carapace a candidate for conscious experience? Does each cortical neuron vie for the conscious spotlight, like the contestants on a televised talent show? (Recall Dennett on “cerebral celebrity.”)
To make progress on this question, we can ascend from brain to mind, and ask which of our psychological states can be conscious. Answers to this question range from boney to bulgy. At one extreme, there are those who say consciousness is limited to sensations; in the case of vision, that would mean we consciously experience sensory features such as shapes, colors, and motion, but nothing else. This is called conservatism (Bayne), exclusivism (Siewert), or restrictivism (Prinz). On the other extreme, there are those who say that cognitive states, such as concepts and thoughts, can be consciously experienced, and that such experiences cannot be reduced to associated sensory qualities; there is “cognitive phenomenology.” This is called liberalism, inclusivism, or expansionism. If defenders of these bulgy theories are right, we might expect to find neural correlates of consciousness in the most advanced parts of our brain.
In this discussion, I will battle the bulge. I will sketch a restrictive theory of consciousness and then consider arguments for and against cognitive phenomenology.
2. The Locus of Consciousness
Not only do I think consciousness is restricted to the senses; I think it arises at a relatively early level of sensory processing. Consider vision. According to mainstream models in neuroscience, vision is hierarchically organized. Let’s consider where in that hierarchy consciousness arises.
Low-level vision, associated with processes in primary visual cortex (V1) registers very local features, such as small edges and bits of color. Intermediate-level vision is distributed across a range of brain areas with names like V2 through V7. Neural activations in these areas integrate local features into coherent wholes, but, at the same time they preserve the componential structure of the stimulus. The intermediate level represents shapes as presented from particular vantage points, separated from a background, and located at some position in the visual field. High-level vision abstracts away from these features, and generates representations that are invariant across a range of different viewing positions. Such invariant representations facilitate object recognition; a rose seen from different angles in different light causes the same high-level response, allowing us to recognize it as the same. Following Ray Jackendoff, I think consciousness arises at the intermediate level. We experience the world as a collection of bounded objects from a particular point of view, not as disconnected, edged, or viewpoint invariant abstractions.
To drive home this point, consider some facts about low- and high-level vision. The contents of low-level vision don’t seem to match the contents of experience. For example, when two distinct colors are rapidly flickered, we experience one fused color, but low-level vision treat the flickered colors as distinct; fusion occurs at the intermediate level (Jiang et al., 2007; see also Gur and Snodderly, 1997). Likewise, the low level seems oblivious to readily perceived contours, which are registered in intermediate areas (Schira et al. 2004). There is also evidence that the suppression of blink responses doesn’t arise until intermediate-level V3; V1 activity cannot explain why blinks go unperceived (Bristow et al., 2005). High-level vision does better than low-level vision on these features, but suffers from other problems when considered as a candidate for consciousness. Many high-level neurons are largely indifferent to size, position, and orientation. High-level neurons can also be indifferent to handedness, meaning they fire the same way when an object is facing to the right or the left. In addition, high-level neurons often represent complex features, so activity in a single neuron might correspond to a face, even though faces are highly structured objects, with clearly visible parts. It would seem that the neural correlates of visual consciousness cannot be so sparsely coded: just as we can focus in on different parts of a face, we should be able to selectively enhance activity in neurons corresponding to the parts of a face, rather than having a single neuron correspond to the whole.
Such considerations lead me to think that, in vision, the only cells that correspond to what we experience are those at the intermediate-level. I think this is true in other senses as well. For example, when we listen to a sentence, the words and phrases bind together as coherent wholes (unlike low-level hearing), and we retain specific information such as accent, pitch, gender, and volume (unlike high-level hearing). Across the senses, the intermediate-level is the only level at which perception is conscious.
I now want to argue that all conscious experience can be fully explained by appeal to perceptual states at the intermediate-level, including conscious states that seem to be cognitive in nature. That makes me a restrictivist.
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