Abstract
1. The intraretinal action potentials (EIRG's) were recorded with superfine electrodes (less than 1μ) located at different depths in the retina. Actual depths of the electrode within the retina were carefully controlled by means of a combination of the methods of 1) confirming the electrode tip to be just on the retinal surface at the start of each experiment, 2) correcting errors in the micrometer readings due to the mechanical resistance of the retinal tissue to the penetrating electrode, and 3) measuring the thickness of the retina.
2. Alternate micro-and even illuminations of the retina provided another method of the control. By a weak microillumination of the retinal region where the electrode was situated, action potentials were detectable only when the electrode was within the retina. This was found useful as a measure of depth, particularly when the electrode was inserted from the receptor side of the retina, the thickness of which could not be measured.
3. The EIRG's due to microillumination or the focal potential were almost purely negative everywhere within the retina, being most active in the bipolar layer. Their nature was discussed in connection with the origin of the ERG.
4. Recordings of the EIRG's due to even illumination upon the whole retina confirmed the previous result (21) obtained by means of bigger microelectrodes.
5. After the removal of the focal potential changes by strychnine, the configurations of the EIRG's were much alike and similar to the normal ERG, but their amplitudes depended upon the depths. The changes in the amplitudes of a-, b-, and d-wave in them went nearly in parallel, and were most distinct during the electrode excursion within the bipolar layer, implicating a main origin of all the fast components of the ERG in this layer. Some contribution of other retinal layers to the ERG was thought probable, but the isolation was not successful with the present method.
6. The result was favored by a supplemental experiment with the use of a “pencil electrode”, which was originally designed for simultaneous recording of intra-and extracellular action potentials.
