Isolated Brain

a brain (or head) that is completely separated from the body but can nevertheless (for some time) maintain vital activities, given conditions approximating the natural physiological state.

As early as the 1920’s, S.S. Briukhonenko designed the autojector, the first artificial circulatory apparatus in the world. A completely isolated dog’s head, hooked up to this apparatus, maintained life activity for several hours. The American surgeon R. White was the first to succeed in isolating the head of a monkey, whose blood supply was provided either by a special apparatus or from another, donor, monkey. The experiment was conducted under conditions of deep hypothermia, with the use of complex physiological and biochemical methods of monitoring the state of the isolated head. Evidence of the preservation of the life activity of the isolated head for several days was provided by the character of the biopotentials of the isolated head, the metabolic state, and the appearance on the electroencephalogram (EEG) of specific convulsive discharges after the introduction into the blood nourishing the head of substances that produce epileptic convulsions.

The isolated brain is important as an experimental model, suitable for studying certain problems of the physiology, biochemistry, and pathology of the central nervous system, including the mechanisms of brain activity, the relationships of the cortex and subcortex, and the nature of bioelectric activity. The specimens are obtained by severing the brain stem at certain levels, at the same time preserving blood circulation and certain neural connections (F. Bremer, 1937). One specimen (cerveau isolé) is obtained by severing the brain stem between the superior and inferior colliculi of the quadrigeminum. Only the first three pairs of cranial nerves (olfactory, visual, and oculomotor) retain their connection with the brain. Slow waves, typical of drowsiness and sleep, are recorded on the EEG. If the cut is made at the spinobulbar level, a specimen (encéphale isolé) is obtained whose EEG shows activity characteristic of wakefulness. The “behavior” of the head conforms te- the data of the EEG.