Table 1.

Amplitudes of mid-latency auditory gating difference wave, P50 gating ratio, sweeps included in the EPs and tobacco consumption in schizophrenia spectrum patients (stratified by their negative symptom score) and healthy controls

	CON	SCH	SCH low	SCHhigh
Onset
μV
Fz	0.40**	-1.30	-0.68	-1.98
	1.41	1.68	1.42	1.77
Cz	1.13**	-0.37	0.32	-1.14
	1.35	1.14	1.91	2.24
Pz	0.62	-0.12	0.88*	-1.25
	1.50	2.13	1.26	2.41
Fp1	-0.32*	-1.27	-0.59	-2.03
	1.30	1.28	0.81	1.31
Fp2	-0.35*	-1.37	-0.59*	-2.24
	1.30	1.44	0.87	1.49
C3'	0.33	-0.17	0.33	-0.74
	0.90	1.68	1.32	1.94
C4'	0.57	-0.01	0.46	-0.53
	0.99	1.29	1.21	1.25
Peak
μV
Fz	1.31**	-0.06	0.85*	-1.08
	1.64	1.71	0.91	1.87
Cz	1.90*	0.44	1.21	-0.42
	1.64	1.58	1.95	2.56
Pz	0.65	-0.30	0.56*	-1.28
	1.31	1.71	1.19	2.29
Fp1	0.13	-0.41	0.58**	-1.52
	1.26	1.58	1.04	1.35
Fp2	0.20	-0.40	0.77**	-1.71
	1.38	1.82	1.27	1.43
C3'	0.76	0.11	0.44	-0.26
	1.04	1.26	1.17	1.34
C4'	0.95	0.22	0.76	-0.39
	0.82	1.59	1.26	1.78
Other Group Variables
St. P50rat	0.40	0.35	0.35	0.35
	0.30	0.22	0.21	0.25
S1Epochs	98**	77	83	71
	12	23	18	28
S2Epochs	101**	85	94	76
	12	23	16	26
Tobacco	34	75	108	38
	47	73	66	63

Mean amplitudes in μV (standard deviation). *) p < 0.05; **) p < 0.01 (post-hoc pairwise comparisons, Bonferroni corrected) when in (CON) denoting probability of significant difference between healthy controls (CON, N = 24) and all the schizophrenia spectrum patients (SCH, N = 17), when in (SCHlow) denoting probability of significant difference between patients having a negative symptom score (sum of five global SANS (not including global attention) items) ranging 0–7 (SCHlow, N = 9) and the patients having scores ranging 8–12 (SCHhigh, N = 8). The P50 ratio (S2/S1 amplitude) following traditional 10–50 Hz digital filtering has previously been reported [5], where it is compared to two other types of digital filtering. Number of included sweeps in the EP in both stimuli (S1 and S2) differs between healthy comparisons subjects and patients, but not within the patient sample.