Figure 19

The effect of filtering on the overall shape of audA-waves and visA-waves.

A: Subject = Mn. Monaural right ear stimulation at 40 S/s. Abscissa, ms; ordinate V. The sequence-length was 3 sec, of which only the first 1500 ms are shown. Run time = 100 min (1 hr, 40 min).

Dotted lines = Data passband filtered 1–120 Hz.

Solid lines = The same data filtered 5–120 Hz. (Note that this is the only recording shown in this paper that shows data with the highpass filter down to 1 Hz.) The effect of the filter (solid line) is to create a monotonic descent of the peak heights, which appears as a damped sinusoid, but that the brain's response (dotted line) actually has an increased positive peak just before 200 ms, and an increased negative valley at about 375 ms. The waves after about 475 ms have a magnitude within the noise level of the rest of the sweep (1000–3000 ms – not shown). Note also the filtered waveform (solid line) is more regular than the 1–120 Hz data (dotted line).

B: Subject = Cg. Flash stimuli, left visual hemifield, 30 S/s. Same data as Fig. 12.

Dotted Lines = Data passband filtered 5–120 Hz.

Solid Line = The same data as the Dotted Line, but passband filtered 8–50 Hz. The differences due to the narrower passband are small – some are indicated by arrows.