Now showing 1 - 8 of 8
  • Publication
    Functional connectivity between ventral and dorsal frontoparietal networks underlies stimulus-driven and working memory-driven sources of visual distraction
    (Elsevier, 2014-01-01) ;
    We investigate the neural basis of two routes to visual distraction: salient stimuli capture attention in a bottom-up fashion and the reappearance of task-irrelevant items that are being actively maintained in working memory can lead to distraction via top-down, but automatic, guidance of attention. Bottom-up, stimulus-driven distraction has typically been associated with a ventral network incorporating the inferior frontal gyrus and temporoparietal junction. A dorsal network including the superior frontal gyrus, superior parietal cortex and intraparietal sulcus is known to underlie the voluntary, top-down control of attention. Here we show that the ventral attention network may be modulated in a top-down manner by task-irrelevant memory signals. Furthermore, we delineate how the biasing of attention by these bottom-up and top-down sources of visual distraction is modulated by changes in connectivity among critical nodes of ventral and dorsal frontoparietal regions. The findings further our understanding of the neural circuitry that mediates the control of human visual attention.
      692Scopus© Citations 15
  • Publication
    Neural repetition effects in the medial temporal lobe complex are modulated by previous encoding experience
    (Public Library of Science, 2012-07-19) ;
    It remains an intriguing question why the medial temporal lobe (MTL) can display either attenuation or enhancement of neural activity following repetition of previously studied items. To isolate the role of encoding experience itself, we assessed neural repetition effects in the absence of any ongoing task demand or intentional orientation to retrieve. Experiment 1 showed that the hippocampus and surrounding MTL regions displayed neural repetition suppression (RS) upon repetition of past items that were merely attended during an earlier study phase but this was not the case following re-occurrence of items that had been encoded into working memory (WM). In this latter case a trend toward neural repetition enhancement (RE) was observed, though this was highly variable across individuals. Interestingly, participants with a higher degree of neural RE in the MTL complex displayed higher memory sensitivity in a later, surprise recognition test. Experiment 2 showed that massive exposure at encoding effected a change in the neural architecture supporting incidental repetition effects, with regions of the posterior parietal and ventral-frontal cortex in addition to the hippocampus displaying neural RE, while no neural RS was observed. The nature of encoding experience therefore modulates the expression of neural repetition effects in the MTL and the neocortex in the absence of memory goals.
      258Scopus© Citations 8
  • Publication
    Interplay between affect and arousal in recognition memory
    (Public Library of Science, 2010-07-23) ; ;
    Background: Emotional states linked to arousal and mood are known to affect the efficiency of cognitive performance. However, the extent to which memory processes may be affected by arousal, mood or their interaction is poorly understood. Methodology/Principal Findings: Following a study phase of abstract shapes, we altered the emotional state of participants by means of exposure to music that varied in both mood and arousal dimensions, leading to four different emotional states: (i) positive mood-high arousal; (ii) positive mood-low arousal; (iii) negative mood-high arousal; (iv) negative mood-low arousal. Following the emotional induction, participants performed a memory recognition test. Critically, there was an interaction between mood and arousal on recognition performance. Memory was enhanced in the positive mood-high arousal and in the negative mood-low arousal states, relative to the other emotional conditions. Conclusions/Significance: Neither mood nor arousal alone but their interaction appears most critical to understanding the emotional enhancement of memory.
      316Scopus© Citations 25
  • Publication
    A Parieto-Medial Temporal Pathway for the Strategic Control over Working Memory Biases in Human Visual Attention
    (Society for Neroscience, 2012-12-05) ; ; ;
    The contents of working memory (WM) can both aid and disrupt the goal-directed allocation of visual attention. WM benefits attention when its contents overlap with goal-relevant stimulus features, but WM leads attention astray when its contents match features of currently irrelevant stimuli. Recent behavioral data have documented that WM biases of attention may be subject to strategic cognitive control processes whereby subjects are able to either enhance or inhibit the influence of WM contents on attention. However, the neural mechanisms supporting cognitive control over WM biases on attention are presently unknown. Here, we characterize these mechanisms by combining human functional magnetic resonance imaging with a task that independently manipulates the relationship between WM cues and attention targets during visual search (with WM contents matching either search targets or distracters), as well as the predictability of this relationship (100 vs 50% predictability) to assess participants' ability to strategically enhance or inhibit WM biases on attention when WM contents reliably matched targets or distracter stimuli, respectively. We show that cues signaling predictable (> unpredictable) WM-attention relations reliably enhanced search performance, and that this strategic modulation of the interplay between WM contents and visual attention was mediated by a neuroanatomical network involving the posterior parietal cortex, the posterior cingulate, and medial temporal lobe structures, with responses in the hippocampus proper correlating with behavioral measures of strategic control of WM biases. Thus, we delineate a novel parieto-medial temporal pathway implementing cognitive control over WM biases to optimize goal-directed selection.
      364Scopus© Citations 25
  • Publication
    Imaging the genetics of executive functions
    Recent advances in neuroimaging technologies have allowed ever more detailed studies of the human brain. The combination of neuroimaging techniques with genetics may provide a more sensitive measure of the influence of genetic variants on cognitive function than behavioural measures alone. Here we present a review of functional magnetic resonance imaging (fMRI) studies of genetic links to executive functions, focusing on sustained attention, working memory and response inhibition. In addition to studies in the normal population, we also address findings from three clinical populations: schizophrenia, ADHD and autism spectrum disorders. While the findings in the populations studied do not always converge, they all point to the usefulness of neuroimaging techniques such as fMRI as potential endophenotypes for parsing the genetic aetiology of executive function.
      514Scopus© Citations 52
  • Publication
    Noradrenergic genotype predicts lapses in sustained attention
    Sustained attention is modulated by the neurotransmitter noradrenaline. The balance of dopamine and noradrenaline in the cortex is controlled by the DBH gene. The principal variant in this gene is a C/T change at position −1021, and the T allele at this locus is hypothesised to result in a slower rate of dopamine to noradrenaline conversion than the C allele. Two hundred participants who were genotyped for the DBH C−1021T marker performed the Sustained Attention to Response Task (SART). DBH genotype was found to significantly predict performance; participants with more copies of the T allele made more errors of commission, indicative of lapses in sustained attention. A significant negative correlation was also observed for all participants between errors of commission and mean reaction time. The decrease in noradrenaline occasioned by the T allele may impair sustained attention by reducing participants’ ability to remain alert throughout the task and by increasing their susceptibility to distractors.
      827Scopus© Citations 67
  • Publication
    Distinct parietal sites mediate the influences of mood, arousal, and their interaction on human recognition memory
    The two dimensions of emotion, mood valence and arousal, have independent effects on recognition memory. At present, however, it is not clear how those effects are reflected in the human brain. Previous research in this area has generally dealt with memory for emotionally valenced or arousing stimuli but the manner in which interacting mood and arousal states modulate responses in memory substrates remains poorly understood. We investigated memory for emotionally neutral items while independently manipulating mood valence and arousal state by means of music exposure. There were four emotional conditions: positive mood/high arousal, positive mood/low arousal, negative mood/high arousal and negative mood/low arousal. We observed distinct effects of mood valence and arousal in parietal substrates of recognition memory. Positive mood increased activity in ventral posterior parietal cortex (PPC) and orbitofrontal cortex, while arousal condition modulated activity in dorsal PPC and the posterior cingulate. An interaction between valence and arousal was observed in left ventral PPC, notably in a distinct parietal area from the main effects, with a stronger effect of mood on recognition memory responses here under conditions of relative high vs. low arousal. We interpret the PPC activations in terms of the attention to memory hypothesis: increased arousal may lead to increased top-down control of memory, and hence dorsal PPC activation, while positive mood valence may result in increased activity in ventral PPC regions associated with bottom-up attention to memory. The findings indicate that distinct parietal sites mediate the influence of mood, arousal and their interplay during recognition memory. 
      557Scopus© Citations 11
  • Publication
    False Memories for Fake News During Ireland's Abortion Referendum
    The current study examined false memories in the week preceding the 2018 Irish abortion referendum. Participants (N = 3,140) viewed six news stories concerning campaign events-two fabricated and four authentic. Almost half of the sample reported a false memory for at least one fabricated event, with more than one third of participants reporting a specific memory of the event. "Yes" voters (those in favor of legalizing abortion) were more likely than "no" voters to "remember" a fabricated scandal regarding the campaign to vote "no," and "no" voters were more likely than "yes" voters to "remember" a fabricated scandal regarding the campaign to vote "yes." This difference was particularly strong for voters of low cognitive ability. A subsequent warning about possible misinformation slightly reduced rates of false memories but did not eliminate these effects. This study suggests that voters in a real-world political campaign are most susceptible to forming false memories for fake news that aligns with their beliefs, in particular if they have low cognitive ability.
    Scopus© Citations 81  554