[Electrographic registration of metabolic changes in the cerebral cortex evoked by sensory stimuli]

In chronic experiments on rabbits, sensory stimuli from platinum electrodes, located on pia mater in different parts of the cerebral cortex, may produce negative changes of the electrode potential or bioelectrochemical potential (BEChP) lasting from one to dozens of seconds with an amplitude from tenths of millivolts to several millivolts. Sometimes the amplitude of BEChP changes amounted to dozens of millivolts. When recorded from dura mater the changes were much smaller, and in the bone they could not be detected. The evoked BEChP changes appeared only against the background of high initial negative values of the electrode potential (2-3 mv and more) and when the electrodes were not polarized by the amplifier input. A low resistance at the amplifier input contributed to the appearance of evoked BEChP changes. The BEChP change is a complex phenomenon. On one hand, it involves a change of the electrode potential proper which proceeds from shifts in the redox systems (it is recorded both on platinum and golden electrodes) and from changes in the metabolites' content (to which platinum electrodes alone are selectively sensitive). On the other hand, the participation of polarographic processes is also probable. The BEChP changes differ by their latency and by their pattern from the shifts of the DC potential level; this possibly shows that the two kinds of nervous activity manifestaions are related to different aspects of brain tissue activity.