Danko Georgiev earned his M.D. from Medical University of Varna, Bulgaria, graduating summa cum laude in 2004. He obtained a Ph.D. from Kanazawa University, Japan, in 2008 following his research in the area of neuronal differentiation. From 2009 to 2011 he was awarded JSPS Post Doctoral Fellowship by the Japan Society for the Promotion of Science. Currently he is a Post Doctoral Researcher at the Department of Psychiatry and Neurobiology, Kanazawa University. He is a member of the Japanese Society of Neuropsychopharmacology since 2007, member of the Japan Neuroscience Society since 2010, and a member of the Society for Neuroscience since 2010.
Remarks on the Number of Tubulin Dimers Per Neuron and Implications for Hameroff-Penrose Orch OR
Stuart Hameroff has wrongly estimated that a typical brain neuron has 107 tubulin dimers and wrongly attributed this result to Yu and Baas. In this letter we show that Hameroff’s estimate is based on misunderstanding of the results provided by Yu and Baas, who actually measured the total microtubule length in a single axonal projection with length of 56 μm in a differentiating in vitro stage 3 embryonic hippocampal neuron. In order to visualize how big Hameroff’s error is, we have reconstructed two of the studied by Yu and Baas embryonic hippocampal neurons with Neuromantic v1.6.3 and compared them with previously published reconstructions of adult hippocampal neurons. Correct calculations show that an adult differentiated pyramidal neuron in vivo has approximately 1.3×109 tubulin dimers incorporated in cytoskeletal microtubules. This estimate has profound implications for the Hameroff-Penrose Orch OR model, because it sets limitations on the number of quantum coherent neurons and implies that if 100% of the neuronal microtubules are quantum coherent for 25 ms then Hameroff-Penrose Orch OR conscious events should involve only 15 pyramidal neurons.
tubulin dimer; pyramidal neuron; embryonic neuron; Hameroff-Penrose; Orch OR