Announcing the first “Periodic Table for the Human Forebrain,” that proposes similar advantages to the dramatic influence that the Periodic Table of the Elements has enjoyed with respect to Chemistry and Physics. here the two variables defining forebrain evolution are the parameters of phylogenetic age and input specificity. The precise number of parameter levels has accurately been determined for both basic forebrain parameters. Sanides (1972) proposed that the human cortex evolved as a sequence of five concentric growth rings comprising a medio-lateral hemisphere gradient. Furthermore, the interoceptive, exteroceptive and proprioceptive input categories each project to its own four-part complex of cortical bands that define an antero-posterior hemisphere gradient. When the para-coronal variable of phylogenetic age is plotted as the ordinate and the para-sagittal parameter of input specificity charted as the abscissa in a Cartesian coordinate system, the resulting dual parameter grid is spatially oriented in a pattern analogous to the standard cortical representation. Each cortical area described by Brodmann and vonEconomo corresponds to schematically unique age/input parameter coordinates. Furthermore, each affiliated thalamic nucleus of specific age and input coordinates projects to that cortical area comprising identical pair-coordinate values, implying that the evolution of the thalamus and cortex are similarly defined in terms of the dual parameter grid. forebrain.org
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