Figure 1

Scheme of the set-up employed (A). A small magnet, surgically implanted on the mouse skull surface, produces an electrical signal of greater amplitude than background noise when the mouse displays an HTR. The signal is amplified and transduced by a data acquisition system. Trace of raw data showing an HTR event (B, upper panel) and spectrogram corresponding to the HTR event (B, lower panel). Note the 80–100 Hz component characteristic of HTR. Scheme of the signal processing and detection system (C). Amplified magnetometer signal band-pass filtered between 70–110 Hz (C, upper panel), transformation to absolute values (C, mid panel), and double local maxima processing for detection of individual HTR events (C, lower panel). An individual HTR event is registered (inverted closed blue triangle) when the peak prominence (vertical orange line) exceeds the amplitude threshold (dotted black line) and meets the requirement of width (horizontal yellow line) and separation from adjacent peaks (not shown). See also Fig. S1.