VARIATIONS IN LEARNING REFLECT INDIVIDUAL-DIFFERENCES IN SENSORY FUNCTION AND SYNAPTIC INTEGRATION

With the invertebrate Hermissenda as subjects, variability in acquisit ion of a learned association between light and rotation was correlated with the magnitude of the unconditioned responses elicited by these s timuli. Moreover, learning was facilitated by increasing stimulus inte nsity. In the isolated nervous system, pairings of light and mechanica l stimulation of the animal's vestibular hair cells resulted in an inc rease in the excitability of B photoreceptors (an in vitro index of le arning) that was strongly correlated with the strength of the synaptic interaction between the hair cells and the photoreceptors and weakly correlated with the magnitude of the light response in the photorecept ors. Because these in vitro results are not attributable to motor or m otivational variables, they suggest that the efficacy of synaptic inte gration between sensory systems and sensory transduction is the primar y determinant of the variability in learning.