Entropy concept in relation to brain waves and evoked potentials: critique of a physical approach

Basar's view that the larger the number of synchronized and coupled participating neural generators, i.e., the lower the entropy of the neural systems, the lower the responsiveness of the system, and vice versa, was reconsidered experimentally and theoretically, in the light of current knowledge about the relationship between EEG states and evoked potentials. It was found that the morphology as well as the magnitude of the somatosensory evoked potentials was the same during synchronized (low entropy) and desynchronized (high entropy) EEG states in normal human subjects. Baclofen caused an increase in the somatosensory evoked potentials without affecting the EEG in unanaesthetized dogs. In the less complicated and more limited systems such as the skeletal muscle and monosynaptic reflex paradigms, an inverse relationship was established between the entropy state and responsiveness. This relationship can be simply explained by the neurophysiological facts such as Na-inactivation process at the excitable membranes and the refractory states of the neural generators. These results are consistent with those from the literature; the evoked potentials are usually large when recorded during synchronized EEG states and vice versa. It is suggested that, at least, the well established neurophysiological facts should not be ignored in physical approaches to neural mechanisms, especially when it concerns highly complex systems such as the brain.