Previous studies show that the right hemisphere is involved in time processing, and that damage to the right hemisphere is associated with a tendency to perceive time intervals as shorter than they are, and to reproduce time intervals as longer than they are. Whether time processing deficits following right hemisphere damage are related and what is their neurocognitive basis is unclear. In this study, right brain damaged (RBD) patients, left brain damaged (LBD) patients, and healthy controls underwent a time bisection task and a time reproduction task involving time intervals varying between each other by milliseconds (short durations) or seconds (long durations). The results show that in the time bisection task RBD patients underestimated time intervals compared to LBD patients and healthy controls, while they reproduced time intervals as longer than they are. Time underestimation and over-reproduction in RBD patients applied to short but not long time intervals, and were correlated. Voxel-based lesion-symptom mapping (VLSM) showed that time underestimation was associated with lesions to a right cortico-subcortical network involving the insula and inferior frontal gyrus. A small portion of this network was also associated with time over-reproduction. Our findings are consistent with a slowdown of an ‘internal clock’ timing mechanism following right brain damage, which likely underlies both the underestimation and the over-reproduction of time intervals, and their (overlapping) neural bases.

Visuospatial neglect is a frequent and disabling disorder, mostly after stroke, that presents in impaired awareness to stimuli on one side of space. Neglect causes disability and functional dependence, even long after the injury. Improving measurements of the core attentional deficit might hold the key for better understanding of the condition and development of treatment. We present a rapid, pupillometry-based method that assesses automatic biases in (covert) attention, without requiring behavioral responses. We exploit the phenomenon that pupil light responses scale with the degree of covert attention to stimuli, and thereby reveal what draws (no) attention. Participants with left-sided neglect after right-sided lesions following stroke (n = 5), participants with hemianopia/quadrantanopia following stroke (n = 11), and controls (n = 22) were presented with two vertical bars, one of which was white and one of which was black, while fixating the center. We varied which brightness was left and right, respectively across trials. In line with the hypotheses, participants with neglect demonstrated biased pupil light responses to the brightness on the right side. Participants with hemianopia showed similar biases to intact parts of the visual field, whilst controls exhibited no bias. Together, this demonstrates that the pupil light response can reveal not only visual, but also attentional deficits. Strikingly, our pupillometry-based bias estimates were not in agreement with neuropsychological paper-and-pencil assessments conducted on the same day, but were with those administered in an earlier phase post-stroke. Potentially, we pick up on persistent biases in the covert attentional system that participants increasingly compensate for in classical neuropsychological tasks and everyday life. The here proposed method may not only find clinical application, but also advance theory and aid the development of successful restoration therapies by introducing a precise, longitudinally valid, and objective measurement that might not be affected by compensation.

Lemon fragrance is known for its stimulating properties, but its mechanisms of action are not well known yet. This study aimed to examine the effect of lemon essential oil inhalation on healthy participants’ alertness level and their neural correlates using magnetic resonance imaging (MRI). Twenty-one healthy men underwent functional MRI scans in different conditions: a resting state condition, a condition where they were exposed to passive lemon smelling (alternating exposure to lemon and breathing fresh air), and a control condition without lemon fragrance diffusion –the order of the last two conditions being randomized. Alertness levels were assessed immediately after each condition using the Karolinska Sleepiness Scale. Voxel-wise whole-brain global functional connectivity and graph theory analyses were computed to investigate brain functional connectivity and network topology alterations. After lemon fragrance inhalation, we observed a higher level of alertness as compared to resting state –but not compared to control condition. During lemon fragrance inhalation, we found increased global functional connectivity in the thalamus, paralleled by decreased global connectivity in several cortical regions such as precuneus, postcentral and precentral gyrus, lateral occipital cortex and paracingulate gyrus. Graph theory analysis revealed increased network integration in cortical regions typically involved in olfaction and emotion processing such as olfactory bulb, hypothalamus and thalamus, while decreased network segregation in several regions of the posterior part of the brain during olfaction as compared to resting state. The present findings suggest that lemon essential oil inhalation could increase the level of alertness.

Aphasia is a language disorder that often involves speech comprehension impairments affecting communication. In face-to-face settings, speech is accompanied by mouth and facial movements, but little is known about the extent to which they benefit aphasic comprehension. This study investigated the benefit of visual information accompanying speech for word comprehension in people with aphasia (PWA) and the neuroanatomic substrates of any benefit. Thirty-six PWA and 13 neurotypical matched control participants performed a picture-word verification task in which they indicated whether a picture of an animate/inanimate object matched a subsequent word produced by an actress in a video. Stimuli were either audiovisual (with visible mouth and facial movements) or auditory-only (still picture of a silhouette) with audio being clear (unedited) or degraded (6-band noise-vocoding). We found that visual speech information was more beneficial for neurotypical participants than PWA, and more beneficial for both groups when speech was degraded. A multivariate lesion-symptom mapping analysis for the degraded speech condition showed that lesions to superior temporal gyrus, underlying insula, primary and secondary somatosensory cortices, and inferior frontal gyrus were associated with reduced benefit of audiovisual compared to auditory-only speech, suggesting that the integrity of these fronto-temporo-parietal regions may facilitate cross-modal mapping. These findings provide initial insights into our understanding of the impact of audiovisual information on comprehension in aphasia and the brain regions mediating any benefit.

IntroductionAttention Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with many functional impairments thought to be underpinned by difficulties in executive function domains such as working memory. The superior longitudinal fasciculus (SLF) plays an integral role in the development of working memory in neurotypical children. Neuroimaging research suggests reduced white matter organization of the SLF may contribute to working memory difficulties commonly seen in ADHD. This study aimed to examine the relationship between white matter organization of the SLF and working memory in children with ADHD. MethodsWe examined the association of tract volume and apparent fibre density (AFD) of the SLF with working memory in children with ADHD (n = 64) and controls (n = 58) aged 9–11years. Children completed a computerized spatial n-back task and underwent diffusion magnetic resonance imaging (dMRI). Constrained spherical deconvolution-based tractography was used to construct the three branches of the SLF bilaterally and examine volume and AFD of the SLF. ResultsRegression analyses revealed children with ADHD exhibited poorer working memory, and lower volume and AFD of the left SLF-II compared to healthy controls. There was also an association between reaction time and variability (RT and RT-V) and the left SLF-II. Further analyses revealed volume of the left SLF-II mediated the relationship between ADHD and working memory performance (RT and RT-V). DiscussionThese findings add to the current body of ADHD literature, revealing the potential role of frontoparietal white matter in working memory difficulties in ADHD.

The functional organization and related anatomy of executive functions are still largely unknown and were examined in the present study using a verbal fluency task. The objective of this study was to determine the cognitive architecture of a fluency task and related voxelwise anatomy in the GRECogVASC cohort and fMRI based meta-analytical data.First, we proposed a model of verbal fluency in which two control processes, lexico-semantic strategic search process and attention process, interact with semantic and lexico-phonological output processes. This model was assessed by testing 404 patients and 775 controls for semantic and letter fluency, naming, and processing speed (Trail Making test part A). Regression (R2 = .276 and .3, P = .0001, both) and structural equation modeling (CFI: .88, RMSEA: .2, SRMR: .1) analyses supported this model.Second, voxelwise lesion-symptom mapping and disconnectome analyses demonstrated fluency to be associated with left lesions of the pars opercularis, lenticular nucleus, insula, temporopolar region, and a large number of tracts. In addition, a single dissociation showed specific association of letter fluency with the pars triangularis of F3. Disconnectome mapping showed the additional role of disconnection of left frontal gyri and thalamus. By contrast, these analyses did not identify voxels specifically associated with lexico-phonological search processes.Third, meta-analytic fMRI data (based on 72 studies) strikingly matched all structures identified by the lesion approach.These results support our modeling of the functional architecture of verbal fluency based on two control processes (strategic search and attention) operating on semantic and lexico-phonologic output processes. Multivariate analysis supports the prominent role of the temporopolar area (BA 38) in semantic fluency and the F3 triangularis area (BA 45) in letter fluency. Finally, the lack of voxels specifically dedicated to strategic search processes could be due to a distributed organization of executive functions warranting further studies.