Variance at the postsynaptic density (PSD) has the potential to account for various differences in human mental characteristics. Hahn et al (here) examined the prefrontal cortex (BA 9) of 12 human brains after death with mean postmortem intervals of 9.6 hours and mean freezing times at – 80°C of 10.2 +/- 1.9 years. They then isolated fractions of the PSDs and visualized them with electron microscopy.
The authors noted that the neuronal ultrastructures were surprisingly well-maintained. Here is a EM image of synaptic membrane fractions, with arrows on right indicating filamentous crossbridges:
Given that these brains were not frozen immediately following death like other animal brains usually are, the sound structure of their PSDs is interesting.
Also of note is that, in their PSD fractions, various protein concentrations (i.e. receptor tyrosine kinase erbB-4; NMDA receptor’s 1 + 2; DLG5/PSD95) are relatively constant between subjects, as shown by western blotting:
This suggests consistency in PSD samples between individuals postmortem. Moreover, it suggests that neither the postmortem intervals of between 3 – 24 hrs nor the fractionation procedure disturbs protein-protein interactions.
Hahn CG, et al. 2009 The Post-Synaptic Density of Human Postmortem Brain Tissues: An Experimental Study Paradigm for Neuropsychiatric Illnesses. doi: 10.1371/journal.pone.0005251