Neuron Soma Size in the Left and Right Hippocampus of a Genius

Abstract

NEURON SOMA SIZE IN THE LEFT AND RIGHT HIPPOCAMPUS OF A GENIUS D.W. Zaidel* Dept Psychology, UCLA, Los Angeles, CA, USA Underlying brain features of a genius are not understood. It is not known if there is a smooth continuum between a genius and the thousands of the brightest minds alive today. The few postmortem studies of brains of remarkable mathematicians or physicists typically emphasized the neocortex. In the present study, the hippocampus of Albert Einstein (AE) was investigated postmortem. The importance of the hippocampus is established for long-term, explicit, implicit, and episodic memory, and establishment of semantic associations. A single microscope slide (Nissl-stained stained in Harvey[Image]s lab not long after AE[Image]s death at age 76 years) was available for the left and right sides. Soma size of pyramidal neurons in coronal sections of AE[Image]s left and right hippocampi were photographed, then digitized and systematically measured on a computer in hippocampal subfields CA1, CA2, CA3, CA4, and subiculum. An atypical left-right asymmetry emerged in AE, with soma size being consistently and significantly larger in the left than in the right side in all homologous subfields except for CA2, whereas in 10 ordinary adults, aged 22 to 84 years, there was minimal and inconsistent soma size asymmetry in direction (left vs right) or extent. However, the soma size variability revealed similarities in both AE and the ordinary adults, particularly in hippocampal subfields CA1 and CA2, bilaterally. The direction of the cell size asymmetry in AE[Image]s hippocampi could simply reflect age-related changes in combination with unusual neuronal connectivity of prenatal or experiential origin. This is difficult to ascertain, and the relationship between the hippocampal status at the time of his death and its role in his genius in his most creative years is a matter for debate.