The History of Neuroscience 6: Reflexes and Learning

Abstract

A reflex is an involuntary physiological response evoked by external stimuli. Robert Whytt, though he believed in the spirit, identified the neural pathways that elicit some involuntary actions, including the pupillary light reflex. Bell and Magendie found the ventral and dorsal spinal roots responsible for separate motor and sensory functions. Marshall Hall elucidated the spinal and medullary control of complex reflex behaviors. Charles Sherrington explained in detail the integrative nature of the reflexes, including the importance of both excitation and inhibition. Reflexes became recognized as important factors in the mental process through the contributions of Ivan Sechenov. He highlighted that simple reflexes were the fundamental blocks that create more complex behaviors. Ivan Pavlov discovered the presence of the learned (conditional) reflexes as well as the inborn ones, which had a major impact on the development of psychology. He proposed that all learned behavior was a long chain of conditioned reflexes. Donald Hebb brilliantly described synapses as the key sites in creating learned behavior and memory, which involve large circuits of reflex activities.