Roger Sperry's Chemoaffinity Hypothesis Presupposes That Each Neuron Carries a Unique

Essay

Roger Sperry's chemoaffinity hypothesis presupposes that each neuron carries a unique 'ID tag' that allows it to make the appropriate connections. We estimate that the human brain is composed of about 10¹¹ neurons making 10¹⁴ synaptic connections, yet the human genome only contains about 20,000 protein-coding genes. Given that there are not enough genes to identify even a small fraction of these neurons, what strategies have evolved in order to achieve the enormous degree of wiring specificity required for normal nervous system function??