It’s a raster plot. A plot of cell firing. With time on the x-axis, and cells (grouped into columns, roughly) on the y-axis.
In particular this is a raster plot for the cell firings of a network that @complyue has coded up, which captures all the sequences of letters in a corpus of text (the Brown Corpus in this case.)
He then drives the network by spiking cells in a prompt sequence, and sees how the activation spreads across synapses representing observed sequences of letters in the Brown Corpus.
To start interpreting it, look first at the extreme left. The very first cells to fire will be exactly those of the driving “prompt”.
If you’re talking about the last chart he posted in this thread, you can see on the extreme top left some spikes for “x”. Then, lower down, a bit later, spikes for “d”, “e”, “f”, “c”, “a”, “f”, and “e”, in sequence. That’s what he’s chosen to use to drive, or “prompt” the network, as a test. The other cell firings are the way those initial prompt spikes spread, and then repeated, or oscillated as activation circulated around the sequences of letters observed in the Brown Corpus.
We want to tune the network so that sequences of letters which tend to share beginning and end points in the observed sequences of the Brown, will synchronize, and give us nice vertical lines we can use to identify words, and later phrases.