Göran Söderlund

Stimulus-dependent dopamine release in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is related to an attenuated and dysfunctional dopamine system. Normally, a high extracellular dopamine level yields a tonic dopaminergic input that down-regulates stimuli-evoked phasic dopamine responses through autoreceptors. Abnormally low tonic extracellular dopamine in ADHD up-regulates the autoreceptors so that stimuli-evoked phasic dopamine is boosted. The authors propose that these boosted phasic responses yield hypersensitivity to environmental stimuli in ADHD. Stimuli evoking moderate brain arousal lead to well-functioning performance, whereas either too little or too much stimuli attenuate cognitive performance. Strong, salient stimuli may easily disrupt attention, whereas an environment with impoverished stimuli causes low arousal, which is typically compensated for by hyperactivity. Stochastic resonance is the phenomenon that makes a moderate noise facilitate stimulus discrimination and cognitive performance. Computational modeling shows that more noise is required for stochastic resonance to occur in dopamine-deprived neural systems in ADHD. This prediction is supported by empirical data.

The effects of background white noise on memory performance in inattentive school children

BackgroundNoise is typically conceived of as being detrimental for cognitive performance; however, a recent computational model based on the concepts of stochastic resonance and dopamine related internal noise postulates that a moderate amount of auditive noise benefit individuals in hypodopaminergic states. On the basis of this model we predicted that inattentive children would be enhanced by adding background white noise while attentive childrens performance would deteriorate.MethodsFifty-one secondary school pupils carried out an episodic verbal free recall test in two noise conditions. In the high noise condition, verb-noun sentences were presented during auditory background noise (white noise, 78 dB), and in the low noise condition sentences were presented without noise.ResultsExposure to background noise improved performance for inattentive children and worsened performance for attentive children and eliminated episodic memory differences between attentive and inattentive school children.ConclusionsConsistent with the model, our data show that cognitive performance can be moderated by external background white noise stimulation in a non-clinical group of inattentive participants. This finding needs replicating in a larger sample using more noise levels but if replicated has great practical applications by offering a non-invasive way to improve school results in children with attentional problems.

Different effects of adding white noise on cognitive performance of sub-, normal and super-attentive school children

Objectives Noise often has detrimental effects on performance. However, because of the phenomenon of stochastic resonance (SR), auditory white noise (WN) can alter the “signal to noise” ratio and improve performance. The Moderate Brain Arousal (MBA) model postulates different levels of internal “neural noise” in individuals with different attentional capacities. This in turn determines the particular WN level most beneficial in each individual case–with one level of WN facilitating poor attenders but hindering super-attentive children. The objective of the present study is to find out if added WN affects cognitive performance differently in children that differ in attention ability. Methods Participants were teacher-rated super- (N = 25); normal- (N = 29) and sub-attentive (N = 36) children (aged 8 to 10 years). Two non-executive function (EF) tasks (a verbal episodic recall task and a delayed verbal recognition task) and two EF tasks (a visuo-spatial working memory test and a Go-NoGo task) were performed under three WN levels. The non-WN condition was only used to control for potential differences in background noise in the group testing situations. Results There were different effects of WN on performance in the three groups-adding moderate WN worsened the performance of super-attentive children for both task types and improved EF performance in sub-attentive children. The normal-attentive children’s performance was unaffected by WN exposure. The shift from moderate to high levels of WN had little further effect on performance in any group. Significance The predicted differential effect of WN on performance was confirmed. However, the failure to find evidence for an inverted U function challenges current theories. Alternative explanations are discussed. We propose that WN therapy should be further investigated as a possible non-pharmacological treatment for inattention.

Distractor or Noise? The Influence of Different Sounds on Cognitive Performance in Inattentive and Attentive Children

It is a well known and certified fact that noise under most circumstances interfere with cognitive processing of various kinds, e.g. vigilance (e.g. Broadbent, 1951), arithmetic’s (Broadbent, 1958), and response speed (Broadbent, 1957). This effect is assumed to be due to the competition of attentional resources between the target and the distracting stimuli. This finding is often replicated and found valid among different tasks and participant populations (Belleville, Rouleau, Van der Linden, & Collette, 2003; Boman, 2004; Klatte, Meis, Sukowski, & Schick, 2007; Rouleau & Belleville, 1996). Most research since Broadbent’s days has dealt with the negative effects of noise and different kinds of auditory distraction. In line with this earlier research has demonstrated that inattentive persons, such as children with ADHD (attention deficit /hyperactivity disorder) are even more susceptible to distraction as compared with their attentive peers. This has been shown in numerous of studies (e.g. Corbett & Stanczak, 1999; Geffner, Lucker, & Koch, 1996; Rickman, 2001).

Erratum: Noise benefit in prepulse inhibition of the acoustic startle reflex

Fig. 4 a ASR to a single pulse expressed as digital units (mean±SEM) at different acoustic background noises in 6-OHDA-lesioned Sprague– Dawley rats. Responses are compared with intact Sprague–Dawley rats. Two-way ANOVA did not indicate a significant effect of 6-OHDA lesioning F(1, 100)=2.157, p=0.1575, but significant effect of noise F(5, 100)=27.3 and interaction lesion×noise F(5, 100)=2.546, p=0.0326. Significant differences in Bonferroni-corrected post hoc t tests indicated by a single asterisk p<0.05. b PPI of the startle response expressed as percent (mean±SEM) of startle response. Two-wayANOVA indicated a main effect of background noise level, F(5, 100)=75.34, p<0.0001, but not of lesion treatment F(1, 100)=0.7398, p=0.3999 or interaction lesion×noise F(5, 100)=2.035, p=0.0801 The online version of the original article can be found at http://dx.doi. org/10.1007/s00213-010-2074-6.