Transforming bottom-up topographic representations with top-down signals in the brain

There has been considerable success in allocating function to the different parts of the brain. We also know much about brain organisation in different regions of the brain and how different brain regions connect to one another. One of the most important next steps for modern neuroscience is to work out how different areas of the brain interact with one another. In particular we need to know how sensory regions communicate with association areas and vice versa. This article explores how top-down signals originating from association areas may be used to process and transform bottom-up representations originating from sensory areas of the brain. Simple models of networks containing topographically organised ensembles of neurons used to integrate and process information are described. The different models can be used to process information in a variety of different ways that could be used as the starting point for a variety of cognitive operations, in particular the extraction of abstract information from sensory representations.