Single neurons in the dentate gyrus and CA1 of the hippocampus exhibit inverse patterns of encoding during trace fear conditioning. Journal   Behavioral neuroscience. Citation   Behav Neurosci. 119(1):164-79 Publication date   2005 Feb Authors   Gilmartin MR McEchron MD Investigators   Matthew McEchron Grant agencies   National Institute on Aging National Institute of Mental Health Grants   NIA AG19903 NIMH MH071095 MeSH headings   Avoidance Learning Dentate Gyrus Fear Hippocampus Neurons MeSH qualifiers   physiology Abstract   Trace fear conditioning is a hippocampus-dependent learning task that requires the association of an auditory conditioned stimulus (CS) and a shock unconditioned stimulus (US) that are separated by a 20-s trace interval. Single-neuron activity was recorded simultaneously from the dentate gyrus (DG) and CA1 of rats during unpaired pseudoconditioning and subsequent trace fear conditioning. Single neurons in DG showed a progressive increase in learning-related activity to the CS and US across trace fear conditioning. Single neurons in CA1 showed an early increase in responding to the CS, which developed into a decrease in firing later in trace conditioning. Correlation analyses showed that DG and CA1 units exhibit inverse patterns of responding to the CS during trace fear conditioning.