Remote Measurements of the Visually Evoked Cortical Potential by Telephone Lines

Abstract

It is reported that trial transmission experiments of the visually evoked cortical potential through telephone lines both for local and long distance (about 450 km) connections demonstrated the feasibility of VECP transmission.

Our major concerns are how to transmit the synchronization pulse stably and without any adverse influence on the VECP.

The transmitted VECP waveforms (VECPs to flash stimuli and those to pattern reversal stimuli) are proved to be good duplicates of the original ones. The synchronization pulse of the stimuli is transmitted by combining it with the VECP using a mixing amplifier.

Several properties of a transmission link used in this study are examined. This system may be of use for data-exchanges between different laboratories, transmission to a large computer room and for remote diagnosis of diseases.

Studies of the visually evoked cortical potential (VECP) have depended strongly upon the aid of the kind of a computer which has only some fixed programmes including averaging. However, there will arise, in the near future, requirements for more sophisticated analysis methods than what a so-called ‘averager’ can do.

To extend the possibilities of VECP analysis, real time entry of VECP data to a larger computer is desirable.

Remote measurements of the electrocardiogram (Rahm et al., 1953) is nowadays widely put in practice, and those of the electroencephalogram are also becoming progressively utilized (Bickford et al., 1969). In 1965 Ray and others made demonstrative telemetry experiments of the auditory and visually evoked cortical potential.

As primary step for this purpose we made trial VECP transmissions by telephone lines using an inexpensive ready-made modem with some added simple circuitry.