Nature Reviews Neuroscience 9, 78. February 2008

A single action potential in a single neuron can induce a behavioral response.

Conventional wisdom holds that the brain analyses patterns of activity in multiple cortical neurons in order to interpret incoming stimuli; however, the question of how many neurons must be active in order to generate a perception has remained unresolved. Two new studies indicate that the neural code that underlies sensory perceptions might be sparser than previously estimated and that activity in single neurons can contribute significantly to behavioural responses.