Table 1.

Spike rate variability

	Magnetic scan velocity (°/s)	Spike rate variability (Kruskal–Wallis statistic, p value)
		Intra-experimental runs	Experimental (segment number) vs control (overall data)
		All segment	1st segment	2nd segment	3rd segment	4th segment	5th segment	6th segment
Awake	12	0.07	0.19	0.13	0.36	0.32	0.41	0.21
	6	0.13	0.012	0.72	0.29	0.23	0.31	0.25
	3	0.03	0.9	0.9	0.9	0.58	0.58	0.05
Anesthetized (ketamine)	24	0.13	0.79	0.38	0.11	0.43	0.88	0.25
	12	0.03	0.11	0.72	0.4	0.4	0.29	0.17
	6	0.02	0.65	0.62	0.12	0.11	0.09	0.17

To assess the possible existence of small magnetic-dependent changes on spike rate the Kruskal–Wallis statistic was used. Each run (experimental or control) was divided in six equal duration segments and the Kruskal–Wallis statistic, with respect to the total number of spikes in each segment, was need to assess variability. Column 3 (Intra-experimental runs) measured variability, in experimental runs, by comparing the activity in each segment against all the others from the same experiment for three repetitions. As the p value is above 0.01 this indicates that all segments had essentially the same spike rate and same variability. In columns 4–9, we compared spike rate in each experimental segment against all the control segments, again no discernable effect is apparent. The variability was the same for awake or anesthetized animals and independent of magnetic scan velocity