This book presents results of current research conducted in the I. Beritashvili Center of Experimental Biomedicine (former I. Beritashvili Institute of Physiology, Tbilisi, Georgia) and is devoted to the experimental investigation of systemic, cellular and molecular mechanisms of physiological functions and their disorders in pathology. More precisely, the results of the following studies are described and discussed: The new, original theory of the fourth main state of an organism’s vitality; memory impairments following excitotoxic lesions; biologically positive behavioral indices of the transition state, caused by informational stress and their pharmacological regulation; functioning of mechanisms responsible for perception constancy; peculiarities of EEG characteristics in individuals with attention deficit hyperactivity disorder; neuroanatomy and neurochemistry of the basic mechanisms for neocortical and hippocampal arousal; changes in learning ability and induction of aggressive behavior caused by manganese loading and ionising radiation; hippocampal activity during learning in different behavioral paradigms; molecular mechanism of PARP-1 action; significance of the diencephalic GABAergic neurons in normal and pathological activity of the brain; cellular mechanisms of antinociceptive tolerance; thermal stability of model globular protein; kinetic features of transport ATPases; antiseizure drugs and EEG in epileptic patients; effect of depakin on EEG epileptiform elements; how six domains form one enzyme; therapeutic potential of extracellular ubiquitin; effect of toluene chronic exposure on hippocampal structure; and the mechanisms of local hyperthermia caused by morphological changes in cerebral tissue.