Introduction

This chapter starts with a brief history of single-unit recording, biased, I am afraid, toward recounting the parts I know best, namely, those that interested me or those I took part in. It stops well short of the present, except for a brief account of some studies on MT neurons in awake behaving monkeys that I believe point the way ahead. The quantitative statistical approach of signal detection theory should enable one to follow a single quantity, the signal-to-noise ratio, through all stages from the sensory stimulus itself, through single-neuron responses at all levels, to reports of perceptual experiences or other behavioral responses. But statistical arguments have pitfalls. First, the source or sources of limiting noise must be correctly identified; second, they are good for establishing limits to what is possible but not very good as a basis for direct models because we know so little about how the brain computes statistics. I think the implications of statistical measures are most easily understood in terms of rules stating when signal-to-noise ratios are conserved, how they can be increased, and when they decrease. Using the rules, statistical arguments can give much insight into the role of single units in sensory systems, for neurons are the only elements capable of collecting together the information relevant to a particular task, which in turn is the only way to obtain high signal-to-noise ratios.

I believe we need to open our eyes to the much more complex types of computation that, as cell biology is beginning to show, might be accomplished by single neurons, so I could not refrain from speculating about this at the end of the chapter. Finally, at the editor's instigation, I have recounted in an Appendix some of my personal experiences in the remarkable department, created by Lord Adrian, in which I had the extraordinary good fortune to grow up scientifically.

This, then, is a personal view. Please do not read this chapter in the hope of finding a complete historical account that leads to a balanced view of the role of single units in vision; desirable though that would be, it is not what the title proclaims and it is not what you will find.