The cholinergic system is a good candidate for the role of determining the relative weight given in cortical information processing to new sensory information versus prior knowledge. We discuss the physiological data supporting this, and suggest that this Bayesian perspective can easily be reconciled with the dynamical framework proposed by Behrendt & Young.

Brains are information processing systems whose operational principles ultimately cannot be understood without resource to information theory. We suggest that understanding how external signals are represented in the brain is a necessary step towards employing further engineering tools to understand the information processing performed by brain circuits during behaviour.

The standard dogmatism ignores the fact that neural coding is extremely flexible, and the degree of “coarseness” versus “locality” of representation in real brains can be different under different task conditions. The real question that should be asked is: What is the operating point of neural coding under natural behavioural conditions? Several sources of evidence suggest that under natural conditions some degree of distribution of coding pervades the nervous system.