Lorenza S. Colzato

Symbolic Control of Visual Attention

The present study reports four pairs of experiments that examined the role of nonpredictive (i.e., task-irrelevant) symbolic stimuli on attentional orienting. The experiments involved a simple detection task, an inhibition of return (IOR) task, and choice decision tasks both with and without attentional bias. Each pair of experiments included one experiment in which nonpredictive arrows were presented at the central fixation location and another experiment in which non-predictive direction words (e.g., “up,” “down,” “left,” “right”) were presented. The nonpredictive symbolic stimuli affected responses in all experiments, with the words producing greater effects in the detection task and the arrows producing greater effects in the IOR and choice decision tasks. Overall, the present findings indicate that there is a strong connection between the overlearned representations of the meaning of communicative symbols and the reflexive orienting of visual attention.

How Does Bilingualism Improve Executive Control? A Comparison of Active and Reactive Inhibition Mechanisms

It has been claimed that bilingualism enhances inhibitory control, but the available evidence is equivocal. The authors evaluated several possible versions of the inhibition hypothesis by comparing monolinguals and bilinguals with regard to stop signal performance, inhibition of return, and the attentional blink. These three phenomena, it can be argued, tap into different aspects of inhibition. Monolinguals and bilinguals did not differ in stop signal reaction time and thus were comparable in terms of active-inhibitory efficiency. However, bilinguals showed no facilitation from spatial cues, showed a strong inhibition of return effect, and exhibited a more pronounced attentional blink. These results suggest that bilinguals do not differ from monolinguals in terms of active inhibition but have acquired a better ability to maintain action goals and to use them to bias goal-related information. Under some circumstances, this ability may indirectly lead to more pronounced reactive inhibition of irrelevant information.

A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood

BACKGROUND Recent insights into the role of the human microbiota in cognitive and affective functioning have led to the hypothesis that probiotic supplementation may act as an adjuvant strategy to ameliorate or prevent depression. OBJECTIVE Heightened cognitive reactivity to normal, transient changes in sad mood is an established marker of vulnerability to depression and is considered an important target for interventions. The present study aimed to test if a multispecies probiotic containing Bifidobacterium bifidum W23, Bifidobacterium lactis W52, Lactobacillus acidophilus W37, Lactobacillus brevis W63, Lactobacillus casei W56, Lactobacillus salivarius W24, and Lactococcus lactis (W19 and W58) may reduce cognitive reactivity in non-depressed individuals. DESIGN In a triple-blind, placebo-controlled, randomized, pre- and post-intervention assessment design, 20 healthy participants without current mood disorder received a 4-week probiotic food-supplement intervention with the multispecies probiotics, while 20 control participants received an inert placebo for the same period. In the pre- and post-intervention assessment, cognitive reactivity to sad mood was assessed using the revised Leiden index of depression sensitivity scale. RESULTS Compared to participants who received the placebo intervention, participants who received the 4-week multispecies probiotics intervention showed a significantly reduced overall cognitive reactivity to sad mood, which was largely accounted for by reduced rumination and aggressive thoughts. CONCLUSION These results provide the first evidence that the intake of probiotics may help reduce negative thoughts associated with sad mood. Probiotics supplementation warrants further research as a potential preventive strategy for depression.

How Social Are Task Representations

The classical Simon effect shows that actions are carried out faster if they spatially correspond to the stimulus signaling them. Recent studies revealed that this is the case even when the two actions are carried out by different people; this finding has been taken to imply that task representations are socially shared. In work described here, we found that the “interactive” Simon effect occurs only if actor and coactor are involved in a positive relationship (induced by a friendly-acting, cooperative confederate), but not if they are involved in a negative relationship (induced by an intimidating, competitive confederate). This result suggests that agents can represent self-generated and other-generated actions separately, but tend to relate or integrate these representations if the personal relationship between self and other has a positive valence.

DOOM'd to Switch: Superior Cognitive Flexibility in Players of First Person Shooter Games.

The interest in the influence of videogame experience on our daily life is constantly growing. “First Person Shooter” (FPS) games require players to develop a flexible mindset to rapidly react to fast moving visual and auditory stimuli, and to switch back and forth between different subtasks. This study investigated whether and to which degree experience with such videogames generalizes to other cognitive-control tasks. Video-game players (VGPs) and individuals with little to no videogame experience (NVGPs) performed on a task switching paradigm that provides a relatively well-established diagnostic measure of cognitive flexibility. As predicted, VGPs showed smaller switching costs (i.e., greater cognitive flexibility) than NVGPs. Our findings support the idea that playing FPS games promotes cognitive flexibility.

Impaired inhibitory control in recreational cocaine users

Chronic use of cocaine is associated with impairment in response inhibition but it is an open question whether and to which degree findings from chronic users generalize to the upcoming type of recreational users. This study compared the ability to inhibit and execute behavioral responses in adult recreational users and in a cocaine-free-matched sample controlled for age, race, gender distribution, level of intelligence, and alcohol consumption. Response inhibition and response execution were measured by a stop-signal paradigm. Results show that users and non users are comparable in terms of response execution but users need significantly more time to inhibit responses to stop-signals than non users. Interestingly, the magnitude of the inhibitory deficit was positively correlated with the individuals lifetime cocaine exposure suggesting that the magnitude of the impairment is proportional to the degree of cocaine consumed.

Visual attention and the temporal dynamics of feature integration

Two experiments studied the emergence of bindings between stimulus features (object files) and between stimulus and response features (event files) over time. Choice responses (R2) were signalled by the shape of a stimulus (S2) that followed another stimulus (S1) of the same or different shape, location, and colour. S1 did not require a response (Experiment 1) or trigger a precued simple response (R1) that was or was not repeated by R2 (Experiment 2). Results demonstrate that the mere cooccurrence of stimulus features, and of stimuli and responses, is sufficient to bind their codes. Bindings emerge quickly and remain intact for at least four seconds. Which features are considered depends on their task‐relevance; hence, integration reflects the current attentional set. There was no consistent trend toward higher order interactions as a function of time or of the amount of attention devoted to S1, suggesting that features are not integrated into a single, global superstructure, but enter independent local bindings presumably subserving different functions.

Meditate to create: the impact of focused-attention and open-monitoring training on convergent and divergent thinking.

The practice of meditation has seen a tremendous increase in the western world since the 60s. Scientific interest in meditation has also significantly grown in the past years; however, so far, it has neglected the idea that different type of meditations may drive specific cognitive-control states. In this study we investigate the possible impact of meditation based on focused-attention (FA) and meditation based on open-monitoring (OM) on creativity tasks tapping into convergent and divergent thinking. We show that FA meditation and OM meditation exert specific effect on creativity. First, OM meditation induces a control state that promotes divergent thinking, a style of thinking that allows many new ideas of being generated. Second, FA meditation does not sustain convergent thinking, the process of generating one possible solution to a particular problem. We suggest that the enhancement of positive mood induced by meditating has boosted the effect in the first case and counteracted in the second case.

GENETIC MARKERS OF STRIATAL DOPAMINE PREDICT INDIVIDUAL DIFFERENCES IN DYSFUNCTIONAL, BUT NOT FUNCTIONAL IMPULSIVITY

Various psychiatric disorders are characterized by elevated levels of impulsivity. Although extensive evidence supports a specific role of striatal, but not frontal dopamine (DA) in human impulsivity, recent studies on genetic variability have raised some doubts on such a role. Importantly, impulsivity consists of two dissociable components that previous studies have failed to separate: functional and dysfunctional impulsivity. We compared participants with a genetic predisposition to have relatively high striatal DA levels (DAT1 9-repeat carriers, DRD2 C957T T/T homozygotes, and DRD4 7-repeat carriers) with participants with other genetic predispositions. We predicted that the first group would show high scores of dysfunctional, but not functional, self-reported impulsivity and greater difficulty in inhibiting a behavioral response to a stop-signal, a behavioral measure of impulsivity. In a sample of 130 healthy adults, we studied the relation between DAT1, DRD4, and C957T polymorphism at the DRD2 gene (polymorphisms related to striatal DA) and catechol-Omethyltransferase (COMT) Val158Met (a polymorphism related to frontal DA) on self-reported dysfunctional and functional impulsivity, assessed by the Dickman impulsivity inventory (DII), and the efficiency of inhibitory control, assessed by the stop-signal paradigm. DRD2 C957T T/T homozygotes and DRD4 7-repeat carriers indeed had significantly higher scores on self-reported dysfunctional, but not functional, impulsivity. T/T homozygotes were also less efficient in inhibiting prepotent responses. Our findings support the claim that dopaminergic variation affects dysfunctional impulsivity. This is in line with the notion that the over-supply of striatal DA might weaken inhibitory pathways, thereby enhancing the activation of, and the competition between responses.

The flexible mind is associated with the catechol-O-methyltransferase (COMT) Val(158)Met polymorphism: Evidence for a role of dopamine in the control of task-switching

Genetic variability related to the catechol-O-methyltransferase (COMT) gene (Val158Met polymorphism) has received increasing attention as a possible modulator of cognitive control functions. Recent evidence suggests that the Val158Met genotype may differentially affect cognitive stability and flexibility, in such a way that Val/Val homozygous individuals (who possess low prefrontal dopamine levels) may show more pronounced cognitive flexibility than Met/-carriers (who possess high prefrontal dopamine levels). To test this, healthy humans (n=87), genotyped for the Val158Met polymorphism at the COMT gene, performed a task-switching paradigm, which provides a relatively diagnostic index of cognitive flexibility. As predicted, Met/-carriers showed larger switching costs (i.e., less cognitive flexibility), F(1,85)=4.28, p<0.05, than Val/Val homozygous individuals. Our findings support the idea that low prefrontal dopamine levels promote cognitive flexibility.