High levels of impulsivity have adverse effects on performance in cognitive tasks, particularLy in those tasks that require high attention investment. Furthermore, both animal and human research has indicated that reduced brain serotonin (5-HT) function is associated with increases in impulsive behaviour or decreased inhibition ability, but the effects of 5-HT challenge have not yet been investigated in subjects vulnerable to impulsivity.
The present study aimed to investigate whether subjects with high trait impulsivity perform worse than low impulsive subjects in a task switching paradigm in which they have to rapidly shift their attention between two response rules, and to investigate the influence of a 5-HT enhancing diet. Healthy subjects with high ( n = 19) and low (n = 18) trait impulsivity scores participated in a double-blind placebo-controlled study. All subjects performed the attention switch task in the morning following breakfast containing either tryptophan-rich alpha-lactalbumin (4.8 g/100 g TRP) or placebo protein (1.4 g/100 g TRP).
Whereas there were no baseline differences between high and low impulsive subjects in task switching abilities, high impulsive subjects made significantly more switch errors and responded slower after dietary 5-HT stimulation, whereas no dietary effects were found on task switching performance in low-impulsive subjects. The deterioration in task switching performance induced by the 5-HT enhancing diet in high impulsive subjects was suggested to be established by general arousal/attention-reducing effects of 5-HT, which might have a larger impact in high impulsive subjects due to either different brain circuitry involved in task switching in this group or lower baseline arousal levels.
Allport D.A. , Wylie G. (2000) Task-switching, stimulus-response bindings, and negative priming. In Monsell S , Driver J S (eds), Attention and Performance XVIIIL Control of Cognitive Processes. MIT Press, Cambridge, MA , pp. 35—70
2.
Asberg M. , Traskman L. , Thoren P (1976) 5-HIAA in the cerebrospinal fluid. A biochemical suicide predictor? Arch Gen Psychiatry33(10): 1193—1197
3.
Bekker E.M. , Overtoom CC , Kenemnas J.L. , Kooij J.J. , De Noord I. , Buitelaar J.K. , Verbaten M.N. (2005) Stopping and changing in adults with ADHD . Psychol Med35: 807—816
4.
Barratt E.S. (1965) Factor analysis of some psychometric measures of impulsiveness and anxiety . Psychol Rep16: 547—554
5.
Booij L. , Merens W. , Markus C R. , Van der Does A J W. (2006) Diet rich in alpha-lactalbumin improves memory in unmedicated recovered depressed patients and matched controls . J of Psychopharm20: 526—535
Cepeda N.J. , Kramer A.F. , Gonzalez-de-Sather Jcm (2001) Changes in executive control across the life span: examination of task-switching performance . Dev Psychol37: 715—730
8.
Cherek D.R. , Lane S.D. (2000) Fenfluramine effects on impulsivity in a sample of adults with and without history of conduct disorder . Psychopharmacology152: 149—156
9.
Clark L. , Roiser J.P. , Rubinsztein D.C. , Sahakian B.J. , Robbins T.W. (2005) Stop signal response inhibition is not modulated by tryptophan depletion or the serotonin transporter polymorphism in healthy volunteers: implications for the 5-HT theory of impulsivity . Psychopharmacology182: 570—578
10.
Cools R. , Blackwell A. , Clark L. , Menzies L. , Cox S. , Robbins T.W. (2005) Tryptophan depletion disrupts the motivation of goal directed behaviour as a function of trait impulsivity . Neuropsychopharmacology30: 1362—1373
11.
Crean J. , Richards J B. , de Wit H. (2002) Effect of Trp depletion on impulsive behaviour in men with or without a family history of alcoholism . Behav Brain Res136: 349—357
12.
Curzon G. (1985) Effects of food intake on brain transmitter amine precursors and amine synthesis. In Sandler M , Silverstone T (eds), Psychopharmacology and Food. Oxford University Press, Oxford , pp. 59—70
13.
Depue R.A. , Spoont M.R. (1986) conceptualizing a serotonin trait . A behavioral dimension of constraint Ann-N-Y-Acad-Sci487: 47—62
14.
Dickman SJ (1993) Impulsivity and information processing. In McCown W , Shure M , Johnson J (eds), The Impulsive Client: Theory, Research and Treatment. American Psychological Association, Washington, DC , pp. 151—180
15.
Evenden J. (1999) Impulsivity: a discussion of clinical and experimental findings . J Psychopharmacol13: 180—192
16.
Eysenck H.J. , Eysenck M.W. (1985) Personallity and Individual Differences. Plenum Press, New York
17.
Fadda F. (2000) Trp-free diets: a physiological tool to study brain 5-HT function . News Physiol Science15: 260—360
18.
Fernstrom J.D. (1990) Aromatic amino acids and momoamine synthesis in the central nervous system: influence of the diet . J Nutr Biochem1: 508—517
19.
Fessler D.M. (2002) Pseudoparadoxical impulsivity in restrictive anorexia nervosa: a consequence of the logic of scarcity . Int J Eating Disorders31: 376—388
20.
Hatcher P.D. , Brown V.J. , Tait D.S. , Bate S. , Overend P. , Hagan J.J. , Jones D.N. (2005) 50HT6 receptor antagonist improve performance in an attentional set shifting task in rats . PsychopharmacolBerlin181: 253—259
21.
Heine W. , Radke M. , Wutzke K.D. , Peters E. , Kundt G. (1996) Alpha-lactalbumin-enriched low-protein infant formulas: a comparison to breast milk feeding . Acta Paediatr85: 1024—1028
22.
Horn N.R. , Dolan M. , Elliott R. , Deakin J.F. , Woodruff P.W. (2003) Response inhibition and impulsivity: an fMRI study . Neuropsychologia41: 1959—1966
23.
Jonkman L M. , Kemner C. , Verbaten M N. , van Engeland H. , Kenemans J L. , Camfferman G. , Buitelaar J K. , Koelega H S. (1999) Perceptual and response interference in children with attention-deficit hyperactivity disorder, and the effects of methylphenidate . Psychophysiology36: 419—429
24.
Kramer A.F. , Hahn S. , Gopher D. (1999) Task coordination and aging: explorations of executive control processes in the task switching paradigm . Acta Psychol101: 339—378
25.
LeMarquand D G. , Benkelfat C. , Pihl R O. , Palmour R M. , Young S N (1999) Behavioral disinhibition induced by tryptophan depletion in nonalcoholic young men with multigenerational family histories of paternal alcoholism . Am J Psychiatry156: 1771—1779
26.
Lijffijt M. , Bekker E.M. , Quik E.H. , Bakker J. , Kenemans J.L. , Verbaten M.N. (2004) Differences between low and high trait impulsivity are not associated with differences in inhibitory control . J Attention Disorders8: 25—32
27.
Linnoila M. , Virkkunen M. , Scheinin M. , Nuutila A. , Rimon R. , Goodwin F.K. (1983) Low cerebrow spinal fluid 5-hydroxyindoleacetic acid concentration differentiates impulsive from nonimpulsive voilent behavior . Life Sci33: 2609—2614
28.
Markus C R. , Olivier B. , Panhuysen G E M. , Van der Gugten J. , Alles M S. , Tuiten A. , Westenberg Hgm , Fekkes D. , Koppeschaar H F. , De Haan E. (2000) The bovine protein Alphalactalbumine increases the plasma ratio of tryotophan to the other large neutral amino acids, and in vulnerable subjects raises brain 5-HT activity, reduces cortisol concentration, and improves mood under stress . Am J Clin Nutr71: 1536—1544
29.
Markus C.R. , Olivier B. , E H F de Haan (2002) Whey protein rich in alpha-lactalbumin increases the plasma Trp/LNAA ratio, and improves cognitive performance in stress-vulnerable subjects . Am J Clin Nutr75: 1051—1056
30.
Markus C.R. , Jonkman L.M. , Lammers J. , Deutz M. , Messer M. , Rigtering N. (2005) Evening intake of alpha-lactalbumin increases plasma tryptophan availability and improves morning alertness and brain measures of attention . Am J Clin Nutr81: 1026—1033
31.
Mayr U. , Keele S. (2000) Changing internal constraints on action: The role of backward inhibitionJ Exp Psychol: Gen129: 4—26
32.
McCown W G. (1993) The Impulsive Client: Theory, Research and Treatment . In McCown WG, Johnson JL, Shure MB (eds), American Psychological Association, Washington DC
33.
Merens W. , Booij L. , Markus C R. , Zitman F. , van der Does A J W. (2005) The effects of a diet enriched with alpha-lactalbumin on mood, stress and cognitive functions in recovered depressed patients . Br J Nutr94: 415—422
34.
Monsell S. (2003) Task switching .Trends Cogn Sci7: 134—140
35.
Murphy F.C. , Smith K.A. , Cowen P.J. , Robbins T.W. , Sahakian B.J. (2002) The effects of tryptophan depletion on cognitive and affective processing in healthy volunteers . Psychopharmacology (Berl) 163: 42—53
36.
Nigg J T. , Butler K M. , Huang-Pollock C L. , Henderson J M. (2002) Inhibitory processes in adults with persistent childhood onset ADHD . J Consult Clin Psychol70: 153—157
37.
Orosco M. , Rouch C. Beslot F , Feurte S. , Regnault A. , Dauge V. (2004) Alpha-lactalbumin-enriched diets enhance serotonin release and induce anxiolytic and rewarding effects in the rat . Behav Brain Res148: 1—10
38.
Patton J.H. , Stanford M.S. , Barratt E.S. (1995) Factor structure of the Barratt Impulsiveness Scale . J Clin Psychol51: 768—774
39.
Quist J.F. , Kennedy J.L. (2001) Genetics of childhood disorders: XXIII ADHD, Part 7: The serotonin system. K Am Acad ChildAdolesc Psychiatry20: 253—256
40.
Revelle W. , Humphreys M.S. , Simon L. , Gilliand K. (1980) The interactive effect of Personality, time of day, and caffeine: a test of the arousal mode . J Exp Psychol: Gen109: 1—31
41.
Rubia K. , Lee F. , Cleare A.J. , Tunstall N. , Fu C.H. , Bramner M. , McGuire P. (2005) Tryptophan depletion reduces right inferior prefrontal activation during response inhibition in fact, event-related fMRI . Psychopharmacology179: 791—803
42.
Schuch S. , Koch I. ( 2003) The role of response selection for inhibition of task sets in task shifting . J Exp Psychol: Hum Percept Perf29: 92—105
43.
Soubrie P. (1986) Reconciling the role of central serotonin neurons in human and animal behavior . Behav Brain Sci9: 319—364
44.
Spivak B. , Vered Y. , Yoran-Hegesh R. , Averbuch E. , Mester R. , Graf E. , Weizman A. (1999) Circulatory levels of catecholamines, serotonin and lipids in attention deficit hyperactivity disorder . Acta Psychiatr Scand99: 300—304
45.
Spoont MR (1992) Modulatory role of serotonin in neural information processing: implications for human psychophatology . Psychol Bull112: 330—350
46.
Walderhaug E. , Lunde H. , Nordvik J.E. , Landro N.I. , Refsum H. , Magnusson A. (2002) Lowering of 5-HT by rapid Trp depletion increases impuliveness in normal individuals . Psychopharmacology164: 385—391
47.
Winstanley C.A. , Dalley J.W. , Theobald D.E. , Robbins T.W. (2004) Fractionating impulsivity: contrasting effects of central 5-HT depletion on different measures of impulsive behavior . Neuropsychopharmacology29: 1331—1343
48.
Winstanley C.A. , Theobald D E H , Dalley J.W. , Cardinal R.N. , Robbins T.W. (2006) Double dissociation between serotonergic and dopaminergic mosulation of medial prefrontal and orbitofrontal cortex during a test of impulsive choice . Cereb Cortex16: 106—114
49.
Zametkin A.J. , Rapoport J.L. (1987) Neurobiology of attention deficit disorder with hyperactivity: where have we come in 50 years?J Am Acad Child Adolesc Psychiatry26: 676—686
