FIGURE 5.

Natural menopause is associated with a selective loss of complex and strong synaptic connections in the monkey hippocampus. A: schematic diagrams illustrating shifts in the types of synaptic connections in the monkey dentate gyrus with aging and menopause. Aging results in an increase in nonsynaptic boutons (NSB) and a decrease in multiple-synaptic boutons (MSB). While menopause does not result in changes in the proportions of NSBs or MSBs, it is associated with a selective decrease in MSBs forming one or more perforated synapses, a type of connection that possesses strong synaptic strength and the ability to simultaneously activate multiple postsynaptic neurons. Arrows indicate potential shifts in bouton subtypes with aging and menopause. Blue, axonal bouton; red, postsynaptic density; yellow, dendritic spine. B: a diagram illustrating the relationships between types of synaptic connections in the monkey dentate gyrus and recognition memory performance. Recognition memory scores positively correlate with the incidence of MSBs forming one or more perforated synapses and inversely correlate with NSB frequency. Serial sections from the monkey dentate gyrus were reconstructed using the free software developed by Dr Kristen Harris and her laboratory. Reconstruct, version 1.1.0.0; http://synapses.clm.utexas.edu. Diagrams and 3-dimensional reconstructions were made based on findings from Hara et al. (69).