The neurophysiology of decision making: rate differences and log likelihood ratios
With little sophistication, the spike rates from sensory neurons can be used to approximate useful statistics for decision making. In the context of deciding between two sensory hypotheses, a simple difference in spike rate between sensory neurons with opposite selectivity is proportional to the log likelihood ratio in favor of one sensory interpretation over another. I will describe neural recording and stimulation experiments from the alert monkey that demonstrate that the brain uses such a difference to make decisions about the direction of motion in a 2-alternative direction discrimination task. The accumulation of this difference to threshold explains the speed and accuracy of simple decisions. I will attempt to address the question of how general is the approximation to log likelihood ratio and what this might mean for neural coding in general.