Reading and writing the neural code

In this Perspective, the author examines how reading and writing the neural code may be linked. He reviews evidence defining the nature of neural coding of sensory input and asks how these constraints, particularly precise timing, might be critical for approaches that seek to ‘write the neural code’ through the artificial control of microcircuits to activate downstream structures. It has been more than 20 years since Bialek and colleagues published a landmark paper asking a seemingly innocuous question: what can we extract about the outside world from the spiking activity of sensory neurons? Can we read the neural code? Although this seemingly simple question has helped us shed light on the neural code, we still do not understand the anatomical and neurophysiological constraints that enable these codes to propagate across synapses and form the basis for computations that we need to interact with our environment. The sensitivity of neuronal activity to the timing of synaptic inputs naturally suggests that synchrony determines the form of the neural code, and, in turn, regulation of synchrony is a critical element in 'writing' the neural code through the artificial control of microcircuits to activate downstream structures. In this way, reading and writing the neural code are inextricably linked.