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The event-related potential N270 component is known to be an electrophysiological marker of the supramodal conflict processing. However little is know about the factors that may modulate its amplitude. In particular, among all studies that have investigated the N270, little or no control of the conflict strength and of the load in working memory have been done leaving a lack in the understanding of this component. We designed a spatial audiovisual conflict task with simultaneous target and cross-modal distractor to evaluate the N270 sensitivity to the conflict strength (i.e., visual target with auditory distractor or auditory target with visual distractor) and the load in working memory (goal task maintenance with frequent change in the target modality). In a first session, participants had to focus on one modality for the target position to be considered (left-hand or right-hand) while the distractor could be at the same side (compatible) or at opposite side (incompatible). In a second session, we used the same set of stimuli as in the first session with an additional distinct auditory signal that clued the participants to frequently switch between the auditory and the visual targets. We found that (1) reaction times and N270 amplitudes for conflicting situations were larger within the auditory target condition compared to the visual one, (2) the increase in target maintenance effort led to equivalent increase of both reaction times and N270 amplitudes within all conditions and (3) the right dorsolateral prefrontal cortex current density was higher for both conflicting and active maintenance of the target situations. These results provide new evidence that the N270 component is an electrophysiological marker of the supramodal conflict processing that is sensitive to the conflict strength and that conflict processing and active maintenance of the task goal are two functions of a common executive attention system. [ABSTRACT FROM AUTHOR]

Abstract: Ascending serotonergic projections from the raphe nuclei to frontal brain areas and the dense distribution of receptor and transporter sites in prefrontal and sensory regions support the idea that serotonin exerts influence on cognitive functioning. Indeed, growing evidence suggests serotonin to be an important factor in learning and memory; however, its precise role in executive processes particularly in voluntary attention is less clear. Event-related EEG studies showed the N1 potential to predict top-down attention allocation and implicated the auditory N1 in central serotonergic activity. Dipole analyses and single-trial coupling of EEG and fMRI revealed N1 sources in the primary auditory cortex and in the anterior cingulate. In the present study, amplitude variation of the event-related N1 potential was investigated on 72 healthy subjects while performing an auditory novelty oddball paradigm to tap top-down and bottom-up attention allocation. Possible serotonergic effects on voluntary attention were analyzed using allele variants of a functional polymorphism (5-HTTLPR) of the gene encoding the serotonin transporter, a key regulator of serotonergic neurotransmission. Because mental effort has been related to top-down attention and N1 modulation, a measure of stable individual differences in cognitive effort was included. The main result was a strong interaction of 5-HTTLPR and cognitive effort on target N1 amplitude. Greater target-related attention allocation was evident in those carriers of the 5-HTTLPR s-allele who described themselves as being more engaged in effortful processing. We suggest that the observed interaction mirrors the interplay between effort-mediated top-down attention by the ACC and serotonergic adjustment on attentional systems. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to establish the relationship between the hemodynamic response of prefrontal cortex (PFC) and individual differences in cognitive control, as measured by a color-word interference task. Twenty-five healthy volunteers were observed through functional near infrared spectroscopy (fNIRS) while performing a modified Stroop paradigm. Mean concentration levels of oxygenated hemoglobin (oxy-Hb) were correlated with behavioral performance in the conflict task. Those with shorter reaction times had higher levels of oxy-Hb concentration in superior dorsolateral PFC. Our results are the first to show a positive correlation between behavioral performance and oxy-Hb levels in superior dorsolateral PFC in a cognitive conflict task. These results suggest that the availability of oxygen in the superior PFC, possibly linked to an increase in metabolism, may be related to attention level and effectiveness of cognitive control. [Copyright &y& Elsevier]

• We found no evidence of executive attention impairment in tinnitus participants. • Tinnitus participants and healthy controls performed comparably well on the Attention Network Test. • The result might reflect the performance of a high-functioning tinnitus sample. Subjective, chronic tinnitus is a condition that is common in most populations. Whereas many individuals tend to habituate to tinnitus over time, for some their attention seems pathologically drawn towards the sensation. For this subgroup of individuals with severe tinnitus, dysfunctional executive attention has been suggested to be implicated in the failure to habituate. However, since most previous studies have used attention tests with low validity and specificity in this assessment, there is a need for further corroborating studies. In the present study, the Attention Network Test was used to compare mainly the efficiency of executive attention between a group of individuals with chronic tinnitus (TG; n = 33) and a healthy control group (CG; n = 37). The results showed that individuals with chronic tinnitus, compared to the CG, did not present with a specific impairment in executive control of attention, nor in any of the other two attention domains. These findings are discussed in relation to the sampling characteristics in this study, which might have led to the sample being more homogenous and high functioning than samples in tinnitus studies generally. Overall, this study suggests that tinnitus and executive control of attention impairment might not be directly related, and that the latter might not necessarily be associated with the maintenance of the condition. [ABSTRACT FROM AUTHOR]