Instrumentation, working hypotheses, and clinical aspects of neurostimulation

The paper describes instrumentation developed in our laboratory for the therapy of neurological disorders, including (a) hybrid stimulator for chronic use which retains constant current characteristics, providing a low resistance path during the quiescent phase between pulses to minimize the postpulse charge; (b) brain radio stimulators, crystal controlled, with digital logic section and an optoelectric sensor for telemetry of the intensity used; (c) external stimoceiver for experimental and clinical use, combining multichannel stimulator and EEG telemetric instrument; (d) transdermal stimoceivers, totally implantable for two-way communication with the brain through the intact skin; and (e) implantable microprocessor for detection of EEG signals which are used to trigger contingent brain stimulation. Our working hypotheses for chronic brain stimulation include (a) electrical modification of the functional set point of specific cerebral areas; (b) feedback-controlled stimulation; and (c) establishment of artificial neuronal links with the aide of the computer. The paper concludes with a discussion of the indications for therapeutic use of brain stimulation and criteria for patient selection.