Pub. date: 2010 | Online Pub. Date: December 16, 2009 | DOI: 10.4135/9781412972000 | Print ISBN: 9781412940818 | Online ISBN: 9781412972000| Publisher:SAGE Publications, Inc.About this encyclopedia
Vincent Di Lollo
The brain's pattern of connectivity involves two-way pathways: feedforward pathways and feedback pathways. For instance, if area A sends signals to area B (feedforward pathway), then area B almost invariably sends signals back to area A (feedback pathway). This entry focuses on the structural and functional aspects of the feedback pathways. The brain's architecture reveals a modular structure, with each module performing a specialized function. In the visual system, signals travel rapidly from the retina along feedforward pathways to the input region of the visual cortex, known as the primary visual cortex . Signals are then processed in separate modules, each optimally tuned to a different stimulus attribute such as orientation, color, and motion. The feedforward pathways are matched by corresponding feedback pathways back to the primary visual cortex. This pattern of two-way pathways is ubiquitous in the brain. As well as being ubiquitous, feedback pathways are massive. For example, ...