Tryptophan depletion and behavioral disinhibition in male adolescents with aggressive, disruptive behavior

LeMarquand, David; Benkelfat, Chawki; Tremblay, R.E.; Pihl, R. O.; Young, Simon N.; Palmour, Roberta M.

doi:10.1016/0006-3223(96)84068-6

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“…The results of the two studies that investigated the effect of ATD on response inhibition were inconclusive [60,61]. Because the majority of behavioral studies did not show effects of ATD on response inhibition [37][38][39][40][41], ATD seems unlikely to impair cognitive flexibility by impairing response inhibition. The effect of ATD on performance monitoring (error followed by negative feedback) was examined in Evers et al [61].…”

Section: Discussion the Effect Of Atd On Cognitive Flexibilitymentioning

confidence: 99%

“…Behavioral studies showed that ATD does not affect response inhibition in healthy volunteers without a genetic vulnerability that is known to interact with ATD, such as a family history of depression or alcoholism [38][39][40][41]. Although ATD does not seem to affect response inhibition, Walderhaug et al [42] showed that ATD increased an Fig.…”

Section: Effects Of Atd On Flexible Behaviormentioning

confidence: 99%

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Serotonin and Cognitive Flexibility: Neuroimaging Studies into the Effect of Acute Tryptophan Depletion in Healthy Volunteers

Evers

Veen²,

Fekkes³

et al. 2007

CMC

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Abstract:Cognitive flexibility is the ability to adjust behavior to changes in the environment or task conditions. Previous research suggested that serotonin (5-HT) is involved in cognitive flexibility. Disturbed 5-HT functioning in animals, psychiatric patients and healthy volunteers leads to more rigid behavior. A well recognized method to manipulate levels of brain 5-HT is acute tryptophan depletion (ATD). This method induces a transient and reversible lowering of plasma tryptophan that has been shown to result in decreased brain 5-HT. Only recently has ATD research been combined with functional Magnetic Resonance Imaging (fMRI). In this review, we discuss recent investigations into the effect of ATD on the Blood Oxygen Level Dependent (BOLD) response during tasks that require cognitive flexibility, in healthy volunteers.Functional MRI studies have shown that ATD changes brain activation during tasks that require cognitive flexibility. It is hypothesized that ATD changes the processing of negative feedback, rather than impairing response inhibition, impairing the response to an error or the loss of cognitive control during response interference. Although the results of these studies are intriguing, they are sometimes contradictory. This could be the result of the different paradigms that have been used. Importantly, these studies strongly suggest that future multidisciplinary research should evaluate the mechanisms underlying individual differences and control for variables that have been shown to interact with the effect of ATD on cognitive flexibility and the related brain activation.Keywords: Serotonin, acute tryptophan depletion, cognitive flexibility, functional neuroimaging.Cognitive flexibility refers to the ability to switch between behavioral strategies, when changes in the environment lead to alterations in the outcome of actions. Previous research suggests that serotonin (5-HT) is involved in cognitive flexibility. Animal research showed that low 5-HT leads to inflexible behavior during reversal learning and response inhibition [1][2][3][4]. Furthermore, psychiatric disorders that show abnormal 5-HT functioning, such as major depression and obsessive compulsive disorder (OCD), are associated with rigid behavior [5][6][7]. Acute tryptophan depletion (ATD) is a well-established method to temporarily lower central 5-HT. Some studies have shown that ATD impairs cognitive flexibility in healthy volunteers [8][9][10][11].Although previous research suggests that 5-HT is important for cognitive flexibility, it is largely unknown how disturbed 5-HT levels change brain activation during tasks that require flexible behavior. Neuroimaging techniques such as functional Magnetic Resonance Imaging (fMRI) and positron emission tomography (PET) are used to investigate which brain areas are activated during task performance. These techniques will enable us to gain more insight into the effect of disturbed 5-HT functioning on brain activation associated with task performance. Thus far only a small number of studies h...

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