PSYCHOLOGICAL DIFFERENCES ASSOCIATED WITH INDIVIDUAL DIFFERENCES IN THE PHYSICAL PROPERTIES OF THALAMOCORTICAL OSCILLATORS
AbstractEEG findings and the related results of neurophysiological studies are used to demonstratehow the physical properties of thalamocortical neurons cause oscillatory electrical activityand EEG frequency response curves. These data confirm that thalamocortical circuits behavelike other simple oscillators and that this behaviour can be explained by the same laws ofphysics that cause oscillatory activity in other material systems. One consequence of thisadvance in the development of theory is that it has been possible to carry out the firstsystematic and physically meaningful analysis of human individual differences inthalamocortical EEG activity, and to describe the results in terms of parameters that areused to describe the dynamic character of other oscillating systems. One parameter, theâ€˜damping ratioâ€™, indicates the rate at which an oscillator loses energy. This determines theduration of oscillatory activity following a transient disturbance and also determines thesharpness of the resonance peak in an oscillatorâ€™s frequency response curve. A secondparameter, â€˜natural frequencyâ€™, indicates the rate at which energy is transferred betweensystem elements. This determines the frequency of free oscillation as well as the frequency ofresonance when an oscillator is â€˜drivenâ€™ at different frequencies. These two parametersprovide a comprehensive description of the dynamic character of thalamocortical oscillatorcircuits, considered in aggregate, and they do so in a way that shows how this depends onâ€˜capacitanceâ€™, â€˜inductanceâ€™ and â€˜resistanceâ€™ effects caused by glutamatergic excitatoryneurons and GABAergic inhibitory neurons. The profound psychological significance ofindividual differences in thalamocortical damping ratios and natural frequencies isillustrated by reference to data which demonstrate that these parameters are related in astrong, systematic, and theoretically meaningful fashion to temperament differences and toall the major and generally accepted dimensions of personality and intelligence.