Abstract

The brain is not silent. Even in the absence of stimuli are the neurons activated every now and then in what is called "spontaneous" or "background activity" which provides a noisy background to the operation of the brain. This work shows how this noise can be utilized in the cognitive process. That is, rather than being treated as a nuisance, noise is given a functional role in the brain´s activity. More than this, the role noise is given is a very essential one. In fact, the models presented in this work would not function without it. The utilization of spontaneous activity is demonstrated in two ways. First, it is shown how this activity can enable new knowledge to be assimilated by the system. This ability is described using a framework of generalised evolution that permits cognition to be considered as an evolutionary process occurring within the life-time of the individual. In this evolutionary view of cognition, the spontaneous activity provides the mechanism of variation. This mechanism of variation is very simple in its nature. Yet, its effects are able to follow the growth of an ever more complex cognitive apparatus as it evolves in the individual mind. The second demonstration of the utilization of noise is a novel model of how the brain is able to detect visual motion. The utilization of spontaneous activity significantly reduces the complexity of the model compared to traditional approaches. The model presented here makes the basic assumption that motion that are present in the current scene was already detected in the previous scene. That is, all that the model needs to do is to update the previous detection to fit the current scene. To account for the initial detection of a movement, spontaneous activity is utilized. Any motion in the visual scene is assimilated by the process if it harmonises with this background activity. Thus, the operation of the system is dependent on the presence of noise. Just like the case of knowledge acquisition mentioned above, noise is used to assimilate new structures into the system