Small systems of neurons.
D000818:Animals; D001048:Aplysia / Q000502:physiology; D004553:Electric Conductivity; D005724:Ganglia / Q000502:physiology; D006185:Habituation, Psychophysiologic; D007858:Learning; D008568:Memory; D009474:Neurons / Q000502:physiology*; D013569:Synapses / Q000502:physiology