Characteristics of the functioning of the hippocampal formation in waking and paradoxical sleep

Analysis of published data identifying different neurotransmitter concentrations in the brain in paradoxical sleep and waking and data on the influences of neurotransmitters on the efficiency of the synaptic inputs to hippocampal neurons led to the conclusion that increases in the acetylcholine, cortisol, and dopamine concentrations during paradoxical sleep, with simultaneous reductions in serotonin and noradrenaline levels, may lead synergistically to a significant depression of transmission efficiency in polysynaptic pathways running through the hippocampus (i.e., the perforant path to neurons of the dentate gyrus, the pathway from the dentate gyrus to field CA3, from field CA3 to field CA1, and from field CA1 to the subiculum) but also to potentiation of the efficiency of the perforant path to pyramidal neurons of fields CA1 and CA3 and increases in the efficiency of associative connections between neurons in field CA3. This pattern of changes in the functioning of the hippocampal formation circuit may underlie differences in remembering and extracting information from memory in paradoxical sleep as compared with waking.