Several papers in 2009 have explored the physiological consequences of Aβ oligomers in Alzheimer disease. In this study from Brad Hyman’s lab, a novel method enabling precise quantification of small structures was adopted to study the presence of Aβ oligomers in Alzheimer brains. The technique, based on immunofluorescence on ultrathin tissue sections, is called array tomography. The lab group found that oligomeric Aβ is deposited as a halo around senile plaques in the Alzheimer brain, but that virtually no oligomers could be found more distant than 50 μm from the plaques. In a second part of this work, transgenic mouse brains were analyzed. Here, micro-deposits of oligomeric Aβ were found to be associated with a subset of excitatory synapses. Interestingly, those synapses were considerably smaller than synapses not in contact with oligomeric Aβ. This work adds to our knowledge about both the relationship between plaques/oligomers and about the pathogenic role of Aβ oligomers in the affected brain.

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