Fig. 1

A Schematic representing two possible types of neural responses that could occur to omissions of rhythmically presented stimuli. Vertical lines represent stimuli presented at 3 Hz (dark grey lines, upper plots), 4 Hz (light grey lines, lower plots), or omitted (red lines). Hypothetical responses to noise bursts are plotted in blue. Left: offset response, whose latency is locked (as marked by the grey horizontal line) to the preceding stimulus rather than to the omitted stimulus. Right: true omission response, whose latency should be locked (as marked by the grey horizontal line) to the omitted stimulus rather than to the preceding stimulus. When analysing response latencies relative to the omitted stimulus, true omission responses should show the same latency relative to the expected time of the omitted response for both 3 and 4 Hz, while offset responses should show a latency shift between 3 and 4 Hz (lower left plot, difference between solid red vertical line, showing expected 4 Hz offset, and dashed grey vertical line, showing expected 3 Hz offset; the difference is marked by the upper horizontal line). B Example stimulus waveforms for 2 Hz (upper plot), 3 Hz (middle plot), and 4 Hz (lower plot) sequences. Red dots denote omitted stimuli. Shaded area denotes the time segment for which raw local field potentials are plotted in C. C Example local field potentials from a representative electrode. Dashed vertical lines denote presented stimuli. Red dots denote omitted stimuli. D Examples of LFP responses averaged over either bursts or omissions, plotted for a representative channel for each rat. Solid lines: average stimulus-evoked responses; dashed lines: average omission responses; colours as above