Ordering of retinotectal connections: a multivariate operational analysis.

Publisher Summary This chapter attempts to analyze the retinotectal system in a more empirical and open-ended fashion than that generally associated with past models. The traditional view of the problem is considered to be erroneous—that is, that no single simple explanation can account for all the observations because the task is to integrate a number of interactive processes into a comprehensive understanding. Such an integrative approach offers an alternative to the current wave of numerical modeling and thus skirts thorny theoretical issues that are associated with simulations of poorly described complex systems. Most hypotheses about how optic fibers form a retinotopic projection onto tectum have relied on a single dominant process to generate order. These processes largely fall into one of three categories. In the oldest category are those hypotheses that assume that individual retinal fibers or tectal cells are intrinsically identical with each other. In the latter, fibers were found to grow to abnormal tectal positions following removal of part of retina or tectum. The third category of explanation arose as an answer to the plasticity results. In particular, these hypotheses address the capacity of optic fibers to preserve retinotopography when a whole retina “compresses” onto a surgically formed half tectum or when a half retina expands across a whole tectum.