The first minute, 0143, shows a pattern that I have seen many times: a sequence of heartbeats where every third beat is three times as strong as a normal beat, 12 of which can be seen below. I have begun to suspect that this may be a phenomenon that only occurs in male subjects. Note that the EEG channels flatline.
Moving on, two and a half hours later at 0408 there are two such beats right before the onset of a marathon REM session that lasted half an hour.
And peaked with eye movements like this at 0412:
Only to end again with some strained beats at 0450. No idea what to make of that spike on channel 2, it seems to pop up quite regularly.