1. Introduction
There are various models in the pathology of Attention Deficit/Hyperactivity Disorder (ADHD). The current models suggest abnormal reward sensitivity as a causal factor. In overall, the predictions of these models in children with ADHD include the following: (a) Relatively strong preferences for smaller sooner rewards compared to larger later rewards, (b) Decreased release of dopamine from corpus striatum while to reward cues. Studies have shown activity of Reticular Activating System (RAS) in brain stem is lower in these patients. Locus coeruleus is the source of norepinephrine in RAS. It keep cortex active but when the activity of RAS is reduced consequently by deficiency in excretion of norepinephrine, the cortex activity (especially the activity of frontal lobe) is reduced which leads to reduced attention and increased impulsivity. Voluntary activation of dopaminergic regions of the brain by neurofeedback and motivational manipulation leads to endogenous dopamine control in these structures, resulting in successful regulation or inhibitory control and reduced impulsivity. This study aims to compare the effects of two methods of motivational manipulation and neurofeedback on reward sensitivity, delay discounting, and impulsivity in children with ADHD.  
2. Materials and Methods 
This is an experimental study with a pre-test/post-test/follow-up design using a control group. The study population consisted of all children aged 7-12 years with ADHD in Tehran, Iran. A convenience sampling method was used for sampling. Sample size was determined 90 based on the study purpose and method (in experimental studies, the sample size should be at least 30 people in each group). 
Neurofeedback and motivational manipulation were performed in the two intervention groups at 12 sessions each for 45 minutes. Balloon Analogue Risk Task and Chocolate Delay Discounting task were used to collect data in pre-test, post-test and follow-up phases. The collected data were analyzed using MANCOVA in SPSS v.23 software.
3. Results
After controlling the effects of pre-test scores on post-test scores, the difference between the groups in the post-test phase was statistically significant in terms of impulsivity and delay discounting (P<0.01) and reward sensitivity (P <0.05). The neurofeedback method (Mean=4.66) had a greater effect on reward sensitivity than motivational manipulation method (Mean=2.31) compared to the control group, which was significant (P<0.01). The effect of motivational manipulation (Mean=2.31) was not significant in comparison with the control group (Table 1). 


4. Discussion
Voluntary activation of dopaminergic regions of the brain by neurofeedback and motivational manipulation leads to endogenous dopamine control in these regions, resulting in successful regulation or inhibitory control and reduced cravings, which reduces impulsivity and reward sensitivity. Substantia Nigra/Ventral Tegmental area is activated by using pleasurable stimulus. Therefore, presenting pleasurable stimulus during neurofeedback and motivational manipulation can be a strategy for endogenous dopamine regulation. Neurofeedback is a reward system that teach the brain how to function more optimally. Hence, the brain is able to create new neural pathways (neuroplasticity), and neurofeedback therapy attempts to reconstruct these pathways. 

Ethical Considerations
Compliance with ethical guidelines
After stating the objectives of the research for the participants, their consent to participate in the research was obtained and they were assured about the confidentiality of information and the authority to participate in the research. At the end of the study, in order to comply with ethical considerations, the control group also intervened (Code: IR.USWR.REC.1399.023).

Funding
The present article was extracted from a research project approved by the Pediatric Neurological Rehabilitation Research Center located at the University of Social Welfare and Rehabilitation Sciences and was sponsored by the University of Social Welfare and Rehabilitation Sciences. (Grant No: 50779). 

Authors contributions
Main investigator, designed the study, collected the data, performed analysis and wrote the first draft: Alireza Karimpour Vazifehkhorani; Supervision: Siyamak Tahmasebi. Read and approved the final revision of the manuscript: Siyamak Tahmasebi Garmtani, Alireza karimpour Vazifehkhorani. 

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
University of Tehran of Social Welfare and Rehabilitation Sciences as the sponsor of this study and all participants who participated in this study are thanked and appreciated.


References

1. Sagvolden T, Johansen EB, Aase H, Russell VA. A dynamic developmental theory of attention-deficit/hyperactivity disorder (ADHD) predominantly hyperactive/impulsive and combined subtypes. Behavioral and Brain Sciences. 2005; 28(3):397-418. [DOI:10.1017/S0140525X05000075] [PMID]
2. Tripp G, Wickens JR. Research review: Dopamine transfer deficit: A neurobiological theory of altered reinforcement mechanisms in ADHD. Journal of child Psychology and Psychiatry. 2008; 49(7):691-704. [DOI:10.1111/j.1469-7610.2007.01851.x] [PMID]
3. Sonuga‐Barke E, Taylor E, Heptinstall E. Hyperactivity and delay aversion-II. The effect of self versus externally imposed stimulus presentation periods on memory. Journal of Child Psychology and Psychiatry. 1992; 33(2):399-409. [DOI:10.1111/j.1469-7610.1992.tb00875.x] [PMID]
4. Gondré-Lewis MC, Bassey R, Blum KJN, Reviews B. Pre-clinical models of reward deficiency syndrome: A behavioral octopus. Neuroscience & Biobehavioral Reviews. 2020; 115:164-88. [DOI:10.1016/j.neubiorev.2020.04.021] [PMID] [PMCID]
5. Sama AA. Attention-Deficit Hyperactivity Disorder (ADHD) in Children: A Move towards Developmental Perspectives. International Journal of Research and Analytical Reviews. 2020; 7(1):928-38. https://www.ijrar.org/papers/IJRAR2001839.pdf
6. Sonuga‐Barke EJ, Williams E, Hall M, Saxton T. Hyperactivity and delay aversion III: The effect on cognitive style of imposing delay after errors. Journal of Child Psychology and Psychiatry. 1996; 37(2):189-94. [DOI:10.1111/j.1469-7610.1996.tb01390.x] [PMID]
7. Miller M, Hinshaw SP. Does childhood executive function predict adolescent functional outcomes in girls with ADHD? Journal of Abnormal Child Psychology. 2010; 38(3):315-26. [DOI:10.1007/s10802-009-9369-2] [PMID] [PMCID]
8. Yu X, Sonuga-Barke E. Childhood ADHD and delayed reinforcement: A direct comparison of performance on hypothetical and real-time delay tasks. Journal of Attention Disorders. 2020; 24(5):810-8. [DOI:10.1177/1087054716661231] [PMID]
9. Aston-Jones G, Rajkowski J, Cohen J. Locus coeruleus and regulation of behavioral flexibility and attention. Progress in Brain Research. 2000; 126:165-82. [DOI:10.1016/S0079-6123(00)26013-5][PMID]
10. Martella D, Aldunate N, Fuentes LJ, Sánchez-Pérez NJFip. Arousal and executive alterations in attention deficit hyperactivity disorder (ADHD). Frontiers in Psychology. 2020; 11:1991. [DOI:10.3389/fpsyg.2020.01991] [PMID] [PMCID]
11. Baumeister S, Wolf I, Hohmann S, Holz N, Boecker-Schlier R, Banaschewski T, et al. The impact of successful learning of self-regulation on reward processing in children with ADHD using fMRI. Attention Deficit and Hyperactivity Disorders. 2019;11(1):31-45. [DOI:10.1007/s12402-018-0269-6] [PMID]
12. Blum K, Badgaiyan RD. Offering a putative “dopamine homeostatic” solution to overcome the perils of reward deficiency syndrome (RDS) epidemic: Emergence of “precision behavioral management (PBM)”. Journal of Addiction Science. 2020; 6(2):32-3. [DOI:10.17756/jas.2020-046]
13. Mahmood Aliloo M, Hashemi Nosratabad T, Karimpour Vazifehkhorani AJIJoP, Psychology C. [The role of impulsivity, sensitivity to reward and anhedonia in distinction people with symptoms of borderline personality disorder from ordinary people (Persian)]. Iranian Journal of Psychiatry and Clinical Psychology. 2018; 24(2):136-47. [DOI:10.32598/ijpcp.24.2.136]
14. Chelazzi L, Perlato A, Santandrea E, Della Libera C. Rewards teach visual selective attention. Vision Research. 2013; 85:58-72. [DOI:10.1016/j.visres.2012.12.005] [PMID]
15. Soltaninejad Z, Nejati V, Ekhtiari H. Effect of anodal and cathodal transcranial direct current stimulation on DLPFC on modulation of inhibitory control in ADHD. Journal of Attention Disorders. 2019: 23(4):325-32. [DOI:10.1177/1087054715618792] [PMID]
16. Hynes TJ, Ferland JM, Feng TL, Adams WK, Silveira MM, Tremblay M, et al. Chemogenetic inhibition of dopaminergic projections to the nucleus accumbens has sexually dimorphic effects in the rat gambling task. Behavioral Neuroscience. 2020; 134(4):309-22. [DOI:10.1037/bne0000372] [PMID]
17. Wilson VB, Mitchell SH, Musser ED, Schmitt CF, Nigg JT. Delay discounting of reward in ADHD: Application in young children. Journal of Child Psychology and Psychiatry2011; 52(3):256-64. [DOI:10.1111/j.1469-7610.2010.02347.x] [PMID] [PMCID]
18. Arns M, Heinrich H, Strehl U. Evaluation of neurofeedback in ADHD: The long and winding road. Biological Psychology. 2014; 95:108-15. [DOI:10.1016/j.biopsycho.2013.11.013] [PMID]
19. Zuberer A, Brandeis D, Drechsler R. Are treatment effects of neurofeedback training in children with ADHD related to the successful regulation of brain activity? A review on the learning of regulation of brain activity and a contribution to the discussion on specificity. Frontiers in Human Neuroscience. 2015; 9:135. [DOI:10.3389/fnhum.2015.00135] [PMID] [PMCID]
20. Greer SM, Trujillo AJ, Glover GH, Knutson BJN. Control of nucleus accumbens activity with neurofeedback. Neuroimage. 2014; 96:237-44. [DOI:10.1016/j.neuroimage.2014.03.073] [PMID] [PMCID]
21. Quevedo K, Liu G, Teoh JY, Ghosh S, Zeffiro T, Ahrweiler N, et al. Neurofeedback and neuroplasticity of visual self-processing in depressed and healthy adolescents: A preliminary study. Developmental Cognitive Neuroscience. 2019; 40:100707. [DOI:10.1016/j.dcn.2019.100707] [PMID] [PMCID]
22. Sulzer J, Sitaram R, Blefari ML, Kollias S, Birbaumer N, Stephan KE, et al. Neurofeedback-mediated self-regulation of the dopaminergic midbrain. Neuroimage. 2013; 83:817-25. [DOI:10.1016/j.neuroimage.2013.05.115] [PMID]
23. Slusarek M, Velling S, Bunk D, Eggers C. Motivational effects on inhibitory control in children with ADHD. Journal of the American Academy of Child & Adolescent Psychiatry. 2001; 40(3):355-63. [DOI:10.1097/00004583-200103000-00016] [PMID]
24. Ihssen N, Sokunbi MO, Lawrence AD, Lawrence NS, Linden DEJ. Neurofeedback of visual food cue reactivity: A potential avenue to alter incentive sensitization and craving. Brain Imaging and Behavior. 2017;11(3):915-24. [DOI:10.1007/s11682-016-9558-x] [PMID] [PMCID]
25. Bakhshayesh AR, Hänsch S, Wyschkon A, Rezai MJ, Esser G. Neurofeedback in ADHD: A single-blind randomized controlled trial. European Child & Adolescent Psychiatry. 2011; 20(9):481-91. [DOI:10.1007/s00787-011-0208-y] [PMID]
26. Weber LA, Ethofer T, Ehlis A-C. Predictors of neurofeedback training outcome: A systematic review. Neuroimage Clinical. 2020; 27:102301. [DOI:10.1016/j.nicl.2020.102301] [PMID] [PMCID]
27. Nazari Ma, Gol Mohammadnezhad G, Pourali Z, Asadol’lah Pour A. [Motivational manipulation effect on sensitivity and response bias on risky as compared with conservative people: A signal detection theory based analysis (Persian)]. Journal of Modern Psychological Researches. 2013; 8(31):175-200. https://psychologyj.tabrizu.ac.ir/article_4291.html?lang=en
28. Breakwell GM, Hammond S, Fife-Schaw C, Smith JA. Research methods in psychology. New York: Sage Publications, Inc; 2006. https://psycnet.apa.org/record/2006-10335-000
29. Borm GF, Fransen J, Lemmens WA. A simple sample size formula for analysis of covariance in randomized clinical trials. Journal of Clinical Epidemiology. 2007; 60(12):1234-8. [DOI:10.1016/j.jclinepi.2007.02.006] [PMID]
30. Pitzianti MB, Spiridigliozzi S, Bartolucci E, Esposito S, Pasini A. New insights on the effects of methylphenidate in attention deficit hyperactivity disorder. Frontiers in Psychiatry. 2020; 11:531092. [DOI:10.3389/fpsyt.2020.531092] [PMID] [PMCID]
31. Carucci S, Balia C, Gagliano A, Lampis A, Buitelaar JK, Danckaerts M, et al. Long term methylphenidate exposure and growth in children and adolescents with ADHD. A systematic review and meta-analysis. Neuroscience & Biobehavioral Review. 2020; 120:509-25. [DOI:10.1016/j.neubiorev.2020.09.031] [PMID]
32. Lejuez CW, Read JP, Kahler CW, Richards JB, Ramsey SE, Stuart GL, et al. Evaluation of a behavioral measure of risk taking: The Balloon Analogue Risk Task (BART). Journal of Experimental Psychology Applied. 2002; 8(2):75-84. [DOI:10.1037/1076-898X.8.2.75] [PMID]
33. Reuben E, Sapienza P, Zingales L. Time discounting for primary and monetary rewards. Economics Letters. 2010; 106(2):125-7. [DOI:10.1016/j.econlet.2009.10.020]
34. Hasslinger J, D’Agostini Souto M, Folkesson Hellstadius L, Bölte S. Neurofeedback in ADHD: A qualitative study of strategy use in slow cortical potential training. Plos One. 2020; 15(6):e0233343. [DOI:10.1371/journal.pone.0233343] [PMID] [PMCID]
35. Tamir M, Robinson MD, Clore GL. The epistemic benefits of trait-consistent mood states: An analysis of extraversion and mood. Journal of Personality and Social Psychology. 2002; 83(3):663-77. [DOI:10.1037/0022-3514.83.3.663] [PMID]
36. Sherman DK, Mann T, Updegraff JA. Approach/avoidance motivation, message framing, and health behavior: Understanding the congruency effect. Motivation and Emotion. 2006; 30(2):164-8. [DOI:10.1007/s11031-006-9001-5] [PMID] [PMCID]
37. Kacelnik A, Bateson M. Risk-sensitivity: Crossroads for theories of decision-making. Trends in Cognitive Sciences. 1997; 1(8):304-9. [DOI:10.1016/S1364-6613(97)01093-0][PMID]
38. Nigg JT, Karalunas SL, Gustafsson HC, Bhatt P, Ryabinin P, Mooney MA, et al. Evaluating chronic emotional dysregulation and irritability in relation to ADHD and depression genetic risk in children with ADHD. Journal of Child Psychology and Psychiatry. 2020; 61(2):205-14. [DOI:10.1111/jcpp.13132] [PMID] [PMCID]
39. Demaree HA, DeDonno MA, Burns KJ, Everhart DE. You bet: How personality differences affect risk-taking preferences. Personality and Individual Differences. 2008; 44(7):1484-94. [DOI:10.1016/j.paid.2008.01.005]
40. Kahneman D, Tversky A. Choices, values, and frames. Handbook of the fundamentals of financial decision making: Part I. Singapore: World Scientific; 2013. p. 269-78. [DOI:10.1142/9789814417358_0016]