Flanker interference at both stimulus and response levels decreases with age

When trying to identify the colour of a target, people's performance is impaired by nearby distractors of different colours. It is controversial whether these interference effects originate from competing stimuli, competing responses or from both simultaneously. These interference effects may also differ depending on a person's age. Comparisons between studies show mixed results, while differences in experimental design and data analysis complicate the interpretation. In our study, we manipulated the relative proportions of congruent and incongruent trials with respect to both stimuli and responses. Considering this aspect, we asked whether people resolve stimulus and response interference differently at different ages. 92 children (6-14 years), 25 young adults (20-43 years) and 33 older adults (60-84 years) performed a coloured version of the Eriksen flanker task. Since reaction times and errors were correlated, inverse efficiency scores were used to address speed-accuracy trade-offs between groups. Absolute interference effects were used to measure relationships with age. The results showed first, unexpectedly, that response interference was comparable between stimulus- and response-balanced conditions. Second, performance at all ages was significantly influenced both by competing stimuli and responses. Most importantly, the size of interference effects decreased with age. These findings cast some doubt on the conclusions of previous studies, and raise further questions about how cognitive control is best measured across the lifespan.</p

CIGARETTE SMOKING HAS NO PRO-COGNITIVE EFFECT IN SUBJECTS WITH OBSESSIVE-COMPULSIVE DISORDER: A PRELIMINARY STUDY

Background: The prevalence of cigarette smoking in patients with different psychiatric disorders is higher than that in the general population, which is partly explained by the pro-cognitive effect of smoking on cognitive functions. In subjects with obsessive-compulsive disorder (OCD), the prevalence of smokers is lower than that in other psychiatric disorders. We hypothesized that cigarette smoking does not provide benefits and even worsen cognitive performance in OCD. Subjects and methods: We compared different executive function subdomains in 20 smoking and 20 non-smoking inpatients with OCD. At the beginning of hospitalization, we assessed visuo-spatial working memory, planning and set-shifting abilities (Cambridge Neuropsychological Test Automated Battery), smoking habits (standardized personal interviews), and the severity of obsessivecompulsive symptoms (Dimensional Yale-Brown Obsessive-Compulsive Scale). Results: The performance of smokers and non-smokers did not differ significantly in any cognitive subdomain. The smoking duration was significantly associated with poorer visuo-spatial working memory performance (P=0.001). Conclusions: Our results showed that cigarette smoking did not provide cognitive enhancement across various executive function subdomains in subjects with OCD. The lack of beneficial cognitive effects of smoking may make these subjects less prone to smoking and may partially explain the lower rate of smokers in OCD compared with other psychiatric conditions

Hand posture, but not vision of the hand, affects tactile spatial resolution in the grating orientation discrimination task

The grating orientation discrimination task (GOT) is a sensitive and reliable measure of tactile spatial resolution, or acuity. We used the GOT in three experiments to investigate the effects of hand posture and hand visibility on spatial acuity. Participant sex and experimental design were also manipulated. Healthy adult participants received brief touches to their index fingertips of grated, domed objects. Their task was to decide whether the gratings ran 'along' or 'across' their finger. Measures of the smallest grating width for which participants could reliably discriminate between orientations were recorded as threshold. Experiment 1 evaluated the effect of two- versus one-interval discrimination, hand used and participant sex. Experiments 2 and 3 evaluated the effects of hand visibility (visible or covered) and hand posture (in front or to the side). Females were better than males; the two-interval task resulted in lower thresholds than the one-interval task; and left and right hand thresholds were not significantly different. Most importantly, while hand visibility did not have a significant effect on the task, thresholds were affected by hand posture—worse when the hand was oriented to the side of the body than in front. These results replicate previously reported effects of sex (or finger size), but failed to replicate the so-called ‘visual enhancement of touch’ (VET) effect. We also report a meta-analysis of 27 VET studies, finding a significant effect of ‘non-informative’ vision on tactile perception. Our novel finding is that hand posture affects tactile acuity

STIMULUS AND RESPONSE INTERFERENCE: BEHAVIOUR AND NEUROPHYSIOLOGY OF THE FLANKER EFFECT

Constantly, we are influenced by irrelevant information which is fundamental to ignore to result in effective behaviours. In this research project, we used a colour version of the Flanker task to study interference control - the ability to overcome the influence of irrelevant stimuli and competing responses. In Chapter 1, we will present the dual process model used to understand cognitive processes involved in conflict situations. In the Flanker task, the indirect route (controlled) drives the activation of the correct response, whereas the direct route (automatic) activates the incorrect response triggered by flankers. The brain needs to resolve the conflict between the two competing responses before choosing the appropriate one, resulting in slower and less accurate performance. Some previous studies showed that interference effects may differ depending on a person’s age, however the literature is still controversial. In our behavioural experiment, presented in Chapter 2, we investigated the lifespan development of stimulus and response interference in children, and in young and older adults. We found that performance at all ages was significantly influenced by competing stimuli and responses. Most importantly, the size of interference effects decreased with age. In the literature, electromyographic (EMG) studies have underlined the importance to investigate, across time, motor processes in both hands. In our experiment (Chapter 3), we used dynamometers and EMG to investigate the motor processes in both responding (chosen) and non-responding (unchosen) hands, continuously across time. As expected, we found activation of the chosen hand. This activation was preceded (~150 ms) by a deactivation of the unchosen hand. These hand motor processes did not differ between the flanker interference conditions. In the next experiment (Chapter 4), we used transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to investigate corticospinal excitability related to chosen and unchosen hands. We were interested in motor processes occurring before the reaction time (RT). In the chosen hand, motor-evoked potential (MEP) amplitudes started increasing 156 ms before the RT. This process did not differ across flanker interference conditions. In the unchosen hand, MEP amplitude was not different from baseline. We therefore partially replicated the findings of the EMG experiment. In our last experiment (Chapter 5), we used TMS over the supplementary motor area (SMA) to study the timing and the role of this brain area in preparation of hand motor responses. Surprisingly, we did not find any effects of TMS on the preparation process of responses. We were cautious in interpreting these results considering the exploratory nature. Taking these findings together, we hypothesise a constructive process between hands rather than a response competition as hypothesised in the dual process model. However, further studies are required aimed to explore the functional and temporal aspects of the motor mechanisms

STIMULUS AND RESPONSE INTERFERENCE: BEHAVIOUR AND NEUROPHYSIOLOGY OF THE FLANKER EFFECT

Constantly, we are influenced by irrelevant information which is fundamental to ignore to result in effective behaviours. In this research project, we used a colour version of the Flanker task to study interference control - the ability to overcome the influence of irrelevant stimuli and competing responses. In Chapter 1, we will present the dual process model used to understand cognitive processes involved in conflict situations. In the Flanker task, the indirect route (controlled) drives the activation of the correct response, whereas the direct route (automatic) activates the incorrect response triggered by flankers. The brain needs to resolve the conflict between the two competing responses before choosing the appropriate one, resulting in slower and less accurate performance. Some previous studies showed that interference effects may differ depending on a person’s age, however the literature is still controversial. In our behavioural experiment, presented in Chapter 2, we investigated the lifespan development of stimulus and response interference in children, and in young and older adults. We found that performance at all ages was significantly influenced by competing stimuli and responses. Most importantly, the size of interference effects decreased with age. In the literature, electromyographic (EMG) studies have underlined the importance to investigate, across time, motor processes in both hands. In our experiment (Chapter 3), we used dynamometers and EMG to investigate the motor processes in both responding (chosen) and non-responding (unchosen) hands, continuously across time. As expected, we found activation of the chosen hand. This activation was preceded (~150 ms) by a deactivation of the unchosen hand. These hand motor processes did not differ between the flanker interference conditions. In the next experiment (Chapter 4), we used transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to investigate corticospinal excitability related to chosen and unchosen hands. We were interested in motor processes occurring before the reaction time (RT). In the chosen hand, motor-evoked potential (MEP) amplitudes started increasing 156 ms before the RT. This process did not differ across flanker interference conditions. In the unchosen hand, MEP amplitude was not different from baseline. We therefore partially replicated the findings of the EMG experiment. In our last experiment (Chapter 5), we used TMS over the supplementary motor area (SMA) to study the timing and the role of this brain area in preparation of hand motor responses. Surprisingly, we did not find any effects of TMS on the preparation process of responses. We were cautious in interpreting these results considering the exploratory nature. Taking these findings together, we hypothesise a constructive process between hands rather than a response competition as hypothesised in the dual process model. However, further studies are required aimed to explore the functional and temporal aspects of the motor mechanisms

Flanker interference across the lifespan

The project is aimed to understand how stimulus, response and general interference effects differ across three age groups, from 6-14, 20-43, and 60-84 years