Radical plasticity thesis

Untitled-3The radical plasticity thesis: How the brain learns to be conscious

Axel Cleeremans

Frontiers of Psychology (2011)


Summary and review of this article

Cleeremans starts by discussing the thermostat and by extension other simple automated equipment, which the philosopher, David Chalmers, suggested to be capable of being conscious because they processed information. Cleeremans argues that processing of information, such as levels of temperature, is just a fact about the thermostat. The device has no way of knowing that it is sensitive to temperature, in the way that humans have systems in their brain which tell them that they have such sensitivity. It is clear that thermostats have no such mechanisms for sensing internal states, but only switches etc. that respond to external conditions. Thus information processing often takes place without consciousness, both in the brain and in modern computer systems. This means that consciousness is something over and above computation. Cleeremans goes on to look at definitions of consciousness. He quotes Nagel (1974) saying ‘experience is what it feels like for a conscious organism to be that organism’. Organisms are implied to have systems for having feelings like this while stones do not. Along with such internal states, they experience the external world in the feel of such properties as redness or the depth of the visual field.

Cleeremans compares a human seeing a red patch and a camera taking a picture of the same red patch. The difference is that the camera has only one response, which is to record the particular shade of red. Beyond this single function, the redness does not do anything to the camera, or produce anything resembling an emotional response. This is because it does not have any additional mechanism to change its internal state, wheras human consciousness can experience a whole range of associations stored in memory that are related to that redness. The author further considers that knowledge of internal states, plus internal representations of external states and their related emotional values are what constitutes consciousness. This is an encouraging start on the road to a viable theory of consciousness as conscious emotional or evaluative processes are now demonstrated to be at the core of  human decision taking. What is interesting is that Cleeremans has the idea that consciousness involves some form of preference. While this might seem obvious to the lay observer, the idea of conscious preference can cause astonishment and indignation in modern consciousness circles.

Cleeremans further proposal that the brain learns to be conscious is more debatable. There are instances of conscious experience that may not involve learning. Some fears may be hard-wired. Laboratory rats that are 20 generations away from the wild are still afraid of the silhouette of a cat. There is also the problem of dementia where consciousness remains unimpaired despite the destruction of memory and learnt material.

That said, most conscious processing involves higher sensory processing or emotional/evaluative assessments, and both of these are seen to use the memory/learnt system. However, the system does appear somewhat circular as the emotional/evaluative areas interact with the dopamine system, which plays a large role in determining what gets learnt or remembered. A further problem is the lack of a change in the processing of either neuronal assemblies or individual neurons, by which these would go from unconscious processing to conscious processing. Learning looks to be necessary for most conscious experience, but the lack of a method for physically altering the neurons involved in consciousness suggests that it may not be sufficient.

Cleeremans would also like to find an experiencer to have the experience of redness, visual depth etc. This is again debatable. The subject or self has been the ‘get out of jail free card’ of much of modern consciousness studies. It is something that it quite easy to analyse, as being the narrative memory plus the distinction between body and environment, and from this to claim to have explained consciousness. Cleeremans does not go down this naive route, but there is nevertheless a tendency to avoid coming face-to-face with consciousness, by proposing that there has to be some kind of Cartesian entity to experience the consciousness rather than accepting that consciousness in parts of the brain is the end product: the buck stops here. Whereas there is now evidence for subjective processing in the brain, there is no evidence for an experiencing entity separate from the neurons involved in consciousness.

As in a lot of psychology or philosophy-based writing on consciousness, the material presented here is in non-scientific language, so instead of referring to relevant regions of the brain with known functions, we have to cope with vague or abstract terms such as ‘first order’, ‘second order’ or ‘higher order’. However, it is still possible to relate this material to actual science, with first order presumably referring to processing in the higher sensory cortex, while second order presumably refers to prefrontal processing in the evaluative areas of the orbitofrontal and anterior cingulate and the reasoning/planning/working memory areas of the dorsolateral prefotnal.

Cleeremans tries to co-opt the fashionable higher order (HOT) theories to support his own more interesting ideas. HOT basically suggests that if one thing thinks about or observes another it becomes conscious, This appears to make no sense in scientific terms. The modern world is full of devices that observe or communicate with one another, but as Cleeremans himself has pointed out, there is no reason to believe that such technologies have consciousness. The simple act of observing or even problem solving is just that without an additional mechanism to be aware of what is going on. Moreover the HOT theories do not make suggestions as to how communication between the two orders would lead to a physical change from unconscious to conscious state on the higher-order side.

In the case of the Cleeremans system, it is important that at least the higher-order side is conscious, but again there is no suggestion of how the act of one side observing the other would produce consciousness. However, it is demonstrated that the ‘value’ of representations that Cleeremans rightly attaches high importance to, arises in parts of the frontal brain regions. It is also likely that, as he argues, the connection between conscious emotion and what has been learnt from the environment explains why evolution selected for consciousness. He further advances the idea of specialisation as between the first order and the second order network. This seems to accord with neuroscientific research that shows the higher sensory cortex producing images while frontal areas evaluate them, or use them as the basis for reasoning or for making predictions. The author also notes the second order activation is not directly correlated to first order signal strength. This can be related to the level of activation in some frontal aresa correlating to subjective appreciation rather than the strength of the original signal.







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