Effects of a structured 20-session slow-cortical-potential-based neurofeedback program on attentional performance in children and adolescents with attention-deficit hyperactivity disorder: retrospective analysis of an open-label pilot-approach and 6-month follow-up

Figures & data

Table 1 Characteristics of the study sample

Characteristics	pre-training sample (N=24)	Post-training sample (N=22)	Follow-up sample (N=13)
Age (years; months) (range)	11.47±3.02 (7–17)	11.27±2.82 (7–17)	11.78±2.82 (8–18)
Gender (boys; girls)	18; 6 (75%; 25%)	16; 6 (72.73%; 27.27%)	9; 4 (69.20%; 30.78%)
DSM-4 subtype
Combined type	21	19	12
Inattentive type	3	3	1
Drug naïve	14	12	6
Comorbidities
CD	9	7	5
Depression	1
Developmental disorder of scholastic skills	5	3	3
Language disorder (unspecified)	1	1	1
Obesity	1	1
PTSD	1

Notes: The number, age, gender and diagnosis of the participants at the three time points of assessment (before NF training = pre; after the 20th session = post; 6 months after the last training session = follow-up) and the number of drug-naïve trainees and the participants’ comorbidities are given.

Abbreviations: CD, conduct disorder; DSM, Diagnostic and Statistical Manual of Mental Disorders; NF, neurofeedback; PTSD, posttraumatic stress disorder.

Figure 1 Training regime.

Note: An overview of the training regime and assessment points is shown.

Figure 2 Participant’s monitor during feedback and transfer trials (images provided with kind permission by NeuroConn, Ilmenau, Germany).

Notes: The screenshots of the participant’s monitor during feedback period I (on the left with feedback, on the right during transfer trials) are shown. On the upper graphics, the feedback monitor shows the screenshots during a negativity trial (blue arrow pointing upward), the bottom black line indicates the baseline and the upper blue line marks the cutoff line. The goal is to move the stimulus (fish) above the upper line. A positivity trial is shown on the two lower graphics (red arrow is pointing downward).

Table 2 Training protocol

Session	Algorithm	Trials	FB−	FB+	TR−	TR+	Ratio (negative/positive)	Transfer rate (%)
Phase I
1–6	SCP_6 min	32	16	16	0	0	50/50	0
7–10	SCP_32_8	40	16	16	4	4	50/50	20
Phase II
11	SCP_32_8	40	16	16	4	4	50/50	20
12–15	SCP_40_20_20	40	10	10	10	10	50/50	50
16–20	SCP_50_30_20	50	18	12	12	8	60/40	40

Notes: The training protocols for each session and training phases I (five sessions per week, 2 weeks duration) and II (two sessions per week, 5 weeks duration) are shown. The number of trials, number of trials with negative FB (FB−), positive FB (FB+), negative TRs (TR−), positive TRs (TR+), the ratio of negative and positive trials (ratio [negative/positive]) and the percentage of the number of transfer trials, are given.

Abbreviations: FB, feedback; SCP, slow cortical potential; TR, transfer trial.

Figure 3 Percentage of correctly regulated negativation and positivation feedback (A) and transfer (B) trials per session.

Notes: The mean percentage of correctly regulated trials per session of all participants is shown. Negativation trials are demonstrated in blue, positivation trials in red. 95% Confidence intervals are displayed as error bars. The dashed line signifies the change of training regime between phase I (daily sessions) and phase II (sessions twice a week).

Table 3 Attentional performance before and after NF training

Parameter	N (T0)	N (T1)	Mean score (T0)	Mean score (T1)	SD (T0)	SD (T1)	df	t/z score	P-value	P′-value	Effect sizes
Divided Attention	23	22
RT auditive	23	22	799.67	713.38	164.17	106.70	20	3.71	0.0014	0.0084	0.62
RT visual	23	22	1,058.05	1,045.76	204.31	216.33	20	0.29	0.77	0.54	0.13
SD auditive	23	22	249.10	176.62	136.76	77.48	20	2.85	0.010	0.050	0.60
SD visual	23	22	354.90	326.52	147.05	136.67	20	1.07	0.30	1.19	0.26
Errors	23	22	2.76	2.29	4.15	3.23	20	0.85	0.41	1.22	0.13
Misses	23	22	5.67	5.24	3.89	4.39	20	0.72	0.48	0.96	0.09
Alertness	23	22
RT	23	22	316.38	346.86	71.66	100.90	20	−2.65	0.015	0.061	0.35
SD	23	22	75.90	97.52	43.11	66.04	20	−1.69	0.11	0.21	0.39
Misses	23	22	0.62	0.62	1.16	1.56	20	0	1	1	0
Phasic alertness	23	22	0.04	0.10	0.11	0.14	20	−2.27	0.034	0.102	0.46
SSvis	23	22
Number of trials	23	22	56.00	61.22	11.52	11.33	17	−2.21	0.041	0.124	0.46
RT mean	23	22	1,084.04	1,072.12	317.17	294.87	20	0.17	0.87	0.78	0.039
SD mean	23	22	620.83	582.11	259.54	248.48	17	0.65	0.52	1.05	0.15
Errors	23	22	22.33	17.24	12.63	11.54	20	2.44	0.024	0.096	0.42
SAdots	22	22
Correct responses, mean RT	22	22	1,378.74	1,251.95	585.29	558.10	19	3.91	0.00095	0.0028	0.22
SD mean	22	22	3.07	3.01	1.46	1.47	19	0.29	0.77	0.78	0.043
Incorrect responses (N)	22	22	50.65	47.45	28.47	30.73	19	0.55	0.59	1.18	0.108

Notes: The mean scores of the TAP subtests “Divided Attention” and “Alertness” and the results of the “SSvis” and “SAdots” subtests of the ANTs at two time points of assessment (pre-training [T0], post-training [T1]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: ANTs, Amsterdam Neuropsychological Tests; NF, neurofeedback; SAdots, Sustained Attention Dots; SSvis, Shifting Attentional Set; SD, standard deviation; TAP, Test for Attentional Performance; RT, reaction time; SD, standard deviation.

Table 4 Attentional performance after NF training and at follow-up

Parameter	N (T1)	N (T2)	Mean score (T1)	Mean score (T2)	SD (T1)	SD (T2)	df	t/z-score	P-value	P′-value	Effect sizes
Divided Attention	22	14
RT auditive	22	14	753.08	690.62	118.79	97.65	12	1.90	0.081	0.41	0.57
RT visual	22	14	1,116.15	1,041.15	212.86	204.12	12	1.24	0.24	0.47	0.36
SD auditive	22	14	207.31	1,67.77	99.25	61.90	12	1.66	0.12	0.37	0.48
SD visual	22	14	363.15	330.62	135.28	165.41	12	0.72	0.48	0.48	0.22
Errors	22	14	2.85	1.69	3.67	1.89	12	1.702	0.11	0.46	0.395
Misses	22	14	5.92	4.00	4.39	3.21	12	2.35	0.037	0.22	0.5001
Alertness	22	14
RT	22	14	372.31	309.31	103.62	58.17	12	2.42	0.033	0.132	0.75
SD	22	14	106.31	74.00	66.24	32.50	12	1.75	0.11	0.21	0.62
Misses	22	14	0.85	0.00	1.95	0.00	12	1.56	0.14	0.14	0.61
Phasic alertness	22	14	0.10	0.042	0.14	0.105	12	2.21	0.048	0.144	0.47
SSvis	22	13
Number of trials	22	13	60.90	69.00	12.57	7.77	9	−2.82	0.020	0.040	0.77
RT mean	22	13	1,133.37	930.63	335.69	253.10	12	3.54	0.004	0.012	0.68
SD mean	22	13	539.53	439.60	197.17	157.84	9	1.801	0.11	0.11	0.56
Errors	22	13	17.62	9.30	11.44	7.48	12	3.68	0.003	0.012	0.86
SAdots	22	13
Correct responses, mean RT	22	13	1,384.82	1,238.54	586.79	515.31	12	3.197	0.008	0.0240	0.26
SD mean	22	13	3.29	3.12	1.14	1.57	12	0.55	0.59	0.59	0.13
Incorrect responses (N)	22	13	53.00	48.54	30.59	36.75	12	0.76	0.46	0.92	0.13

Notes: The mean scores of the TAP subtests “Divided Attention” and “Alertness” and the results of the “SSvis” and “SAdots” subtests of the ANTs at two time points of assessment (post-training [T1], 6-month follow-up [T2]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: ANTs, Amsterdam Neuropsychological Tests; NF, neurofeedback; SAdots, Sustained Attention Dots; SSvis, Shifting Attentional Set; SD, standard deviation; TAP, Test for Attentional Performance; RT, reaction time; SD, standard deviation.

Table 5 Attentional performance before NF training and at follow-up

Parameter	N (T0)	N (T2)	Mean score (T0)	Mean score (T2)	SD (T0)	SD (T2)	df	t/z-score	P-value	P′-value	Effect sizes
Divided Attention	23	14
RT auditive	23	14	817.62	674.69	161.23	105.98	12	4.10	0.001	0.01	1.05
RT visual	23	14	1,013.31	982.62	150.41	217.18	12	0.78	0.45	0.54	0.16
SD auditive	23	14	293.62	162.69	144.96	65.04	12	4.02	0.00	0.01	1.17
SD visual	23	14	336.23	290.85	141.51	146.41	12	1.06	0.31	0.62	0.32
Errors	23	14	3.62	1.54	4.91	1.94	12	2.02	0.07	0.20	0.556
Misses	23	14	6.00	3.77	3.87	3.24	12	2.12	0.055	0.22	0.6244
Alertness	23	14
RT	23	14	330.23	298.54	85.14	62.23	12	1.89	0.083	0.330	0.43
SD	23	14	77.77	69.46	47.19	33.87	12	0.93	0.37	0.74	0.20
Misses	23	14	0.62	0.00	1.19	0.00	12	1.86	0.09	1.00	0.73
Phasic alertness	23	14	0.04	0.04	0.13	0.10	12	0.16	0.874	2.621	0.03
SSvis	23	13
Number of trials	23	13	59.00	68.78	11.63	8.21	8	−2.21	0.027	0.082	0.97
RT mean	23	13	1,066.46	928.89	312.81	264.27	11	1.83	0.094	0.188	0.48
SD mean	23	13	539.58	442.94	201.16	167.04	8	1.78	0.11	0.11	0.52
Errors	23	13	21.58	9.33	11.85	7.81	11	3.56	0.004	0.018	1.22
SAdots	22	13
Correct responses, mean RT	22	13	1,516.69	1,237.94	638.16	538.22	11	4.376	0.001	0.0033	0.47
SD mean	22	13	3.29	2.99	1.51	1.57	11	1.91	0.08	0.17	0.19
Incorrect responses (N)	22	13	54.92	48.00	31.55	38.33	11	0.95	0.36	0.36	0.20

Notes: The mean scores of the TAP subtests “Divided Attention” and “Alertness” and the results of the “SSvis” and “SAdots” subtests of the ANTs at two time points of assessment (pre-training [T0], 6-month follow-up [T2]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: ANTs, Amsterdam Neuropsychological Tests; NF, neurofeedback; SAdots, Sustained Attention Dots; SSvis, Shifting Attentional Set; SD, standard deviation; TAP, Test for Attentional Performance; RT, reaction time; SD, standard deviation.

Figure 4 Mean auditive reaction time of the Divided Attention task before and after NF training.

Notes: The mean auditive reaction times (msec) at the pre- (T0) and post-training (T1) assessment points are shown. Data are represented as mean ± SD. Asterisk symbol indicate the significance (P′). **P′≤0.01.
Abbreviations: NF, neurofeedback; SD, standard deviation.

Figure 5 Mean SD of the auditive reaction time of the Divided Attention task before and after NF training.

Notes: The mean SDs (msec) of the mean auditive reaction times at the pre-(T0) and post-training (T1) assessment points are shown. Data are represented as mean ± SD. Asterisk symbol indicate the significance (P′). *P′≤0.05.
Abbreviations: NF, neurofeedback; SD, standard deviation.

Figure 6 Number of errors in the SSvis task before and after NF training.

Notes: The number of errors at the pre-training (T0) and post-training (T1) assessment points is shown. Data are represented as mean ± SD.
Abbreviations: NF, neurofeedback; SSvis, Shifting Attentional Set; SD, standard deviation.

Figure 7 Number of errors in the SSvis task after NF training and at the 6-month follow-up.

Notes: The number of errors at the pre-training (T0) and post-training (T1) assessment points is shown. Data are represented as mean ± SD. Asterisk symbol indicate the significance (P′). *P′≤0.05.
Abbreviations: NF, neurofeedback; SSvis, Shifting Attentional Set; SD, standard deviation.

Figure 8 Mean reaction time of the SAdots task before and after NF training.

Notes: The mean reaction times (msec) at the pre- (T0) and post-training (T1) assessment points are shown. Data are represented as mean ± SD. Asterisk symbols indicate the significance (P′). **P′≤0.01.
Abbreviations: NF, neurofeedback; SAdots, Sustained Attention Dots; SD, standard deviation.

Figure 9 Mean reaction time of the SAdots task after NF training and at the 6-month follow-up.

Notes: The mean reaction times (msec) at the post-training (T1) and follow-up (T2) assessment points are shown. Data are represented as mean ± SD. Asterisk symbols indicate the significance (P′). *P′≤0.05.
Abbreviations: NF, neurofeedback; SAdots, Sustained Attention Dots; SD, standard deviation.

Table 6 Symptom ratings before and after NF training

Parameter	N (T0)	N (T1)	Mean score (T0)	Mean score (T1)	SD (T0)	SD (T1)	df	t-score	P-value	P′-value	Effect sizes
Parent ratings
FBB-HKS (DSM-4)	20	18
Inattention	20	18	1.59	1.45	0.67	0.66	16	0.98	0.34	1.02	0.22
CBCL/4–18	22	20
Attention problems	22	20	65.58	64.11	9.75	8.83	18	0.94	0.36	0.72	0.16
Teacher ratings
FBB-HKS (DSM-4)
Inattention	17	14	1.80	1.68	0.70	0.69	10	0.86	0.41	0.41	0.17

Notes: The mean scores of the FBB-HKS symptom ratings/checklist, severity scores for inattention and the CBCL/4–18 at the two time points of assessment (pre-training [T0] and post [T1]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: CBCL/4–18, Child Behavior Checklist/4–18; DSM, Diagnostic and Statistical Manual of Mental Disorders; NF, neurofeedback; SD, standard deviation; FBB-HKS, Fremdbeurteilungsbogen für Hyperkinetische Störungen.

Table 7 Symptom ratings after NF training and at the 6-month follow-up

Parameter	N (T1)	N (T2)	Mean score (T1)	Mean score (T2)	SD (T1)	SD (T2)	df	t-score	P-value	P′-value	Effect sizes
Parent ratings
FBB-HKS (DSM-4)	18	14
Inattention	18	14	1.40	1.64	0.70	0.63	11	−1.28	0.23	0.68	0.37
CBCL/4–18	20	14
Attention problems	20	14	65.43	63.00	8.74	7.83	13	1.32	0.21	0.21	0.29
Teacher ratings
FBB-HKS (DSM-4)
Inattention	14	9	1.60	1.25	0.71	0.72	7	1.32	0.23	0.46	0.49

Notes: The mean scores of the FBB-HKS symptom ratings/checklist, severity scores for inattention and the CBCL/4–18 at the two time points of assessment (post [T1] and follow-up [T2]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: CBCL/4–18, Child Behavior Checklist/4–18; DSM, Diagnostic and Statistical Manual of Mental Disorders; NF, neurofeedback; SD, standard deviation; FBB-HKS, Fremdbeurteilungsbogen für Hyperkinetische Störungen.

Table 8 Symptom ratings before NF training and at the 6-month follow-up

Parameter	N (T0)	N (T2)	Mean score (T0)	Mean score (T2)	SD (T0)	SD (T2)	df	t-score	P-value	P′-value	Effect sizes
Parent ratings
FBB-HKS (DSM-4)	20	14
Inattention	20	14	1.71	1.62	0.57	0.61	12	0.49	0.63	0.63	0.95
CBCL/4–18	22	14
Attention problems	22	14	66.64	63.00	10.05	7.83	13	2.08	0.06	0.12	0.40
Teacher ratings
FBB-HKS (DSM-4)
Inattention	17	9	1.97	1.21	0.91	0.76	6	2.57	0.04	0.13	0.90

Notes: The mean scores of the FBB-HKS symptom ratings/checklist, severity scores for inattention and the CBCL/4–18 at the two time points of assessment (pre-training [T0] and follow-up [T2]) are given. df = degrees of freedom, P = significance (two-tailed), P′ = significance (two-tailed) after α-adjustment, d = estimated effect size (Cohen’s d), normal distribution according to Shapiro–Wilk and Kolmogorov–Smirnov tests.

Abbreviations: CBCL/4–18, Child Behavior Checklist/4–18; DSM, Diagnostic and Statistical Manual of Mental Disorders; NF, neurofeedback; SD, standard deviation; FBB-HKS, Fremdbeurteilungsbogen für Hyperkinetische Störungen.

Table 9 Regulation during feedback trials

Session	N	Feedback negativation		Feedback positivation
		Mean % of correctly regulated trials	SD	Mean % of correctly regulated trials	SD
Session 1	23	16.46	13.51	19.70	16.88
Session 2	24	14.83	11.62	22.86	16.48
Session 3	24	15.90	14.16	17.75	11.43
Session 4	24	17.71	15.41	22.13	13.39
Session 5	24	16.75	12.47	19.74	12.65
Session 6	24	22.33	16.47	22.82	14.50
Session 7	24	20.38	15.60	23.39	17.10
Session 8	24	18.72	16.24	23.39	19.33
Session 9	23	22.67	16.42	22.93	21.59
Session 10	24	25.99	21.40	18.42	10.17
Session 11	24	15.52	13.99	28.60	20.67
Session 12	24	23.76	23.00	24.03	21.18
Session 13	24	17.67	17.49	25.81	22.38
Session 14	23	21.11	19.71	23.03	26.14
Session 15	23	21.71	14.77	26.42	23.67
Session 16	23	26.64	18.62	21.67	24.30
Session 17	23	23.27	20.26	32.05	24.60
Session 18	22	22.39	19.89	23.17	20.83
Session 19	21	17.40	12.63	25.86	22.97
Session 20	21	24.29	20.53	25.50	21.97

Note: The mean percentage (%) of correctly regulated feedback trials for positivation and negativation is given.

Abbreviation: SD, standard deviation.

Table 10 Regulation during transfer trials

Session	N	Transfer negativation		Transfer positivation
		Mean % of correctly regulated trials	SD	Mean % of correctly regulated trials	SD
Session 1	23
Session 2	24
Session 3	24
Session 4	24
Session 5	24
Session 6	24
Session 7	24	18.25	17.94	24.60	21.01
Session 8	24	20.25	16.40	19.26	17.20
Session 9	23	24.38	20.67	22.10	20.63
Session 10	24	20.94	19.77	18.74	13.51
Session 11	24	15.80	16.67	28.19	14.69
Session 12	24	16.86	20.51	20.60	17.11
Session 13	24	18.03	17.60	23.85	17.81
Session 14	23	21.42	17.57	18.36	20.52
Session 15	23	24.12	15.82	22.96	16.54
Session 16	23	24.09	16.15	18.83	15.20
Session 17	23	24.49	22.51	26.67	17.35
Session 18	22	21.36	16.39	23.80	24.11
Session 19	21	17.46	11.19	19.27	16.36
Session 20	21	23.36	16.34	21.05	16.98

Note: The mean percentage (%) of correctly regulated transfer feedback trials for positivation and negativation is given.

Abbreviation: SD, standard deviation.