The Impact of Mortality Salience on Mind Wandering During Reading: A Cognitive Test of Terror Management Theory

The effects of mind wandering on normal reading have been explored recently in studies using self-paced reading (Schooler, Reichle, & Halpern, 2004) and eye tracking (Reichle, Reineberg, & Schooler, 2009). These studies demonstrate our propensity to lapse into episodes of mindless reading, but shed little light on its causality. Furthermore, behavioral studies suggest that reminders of death (mortality salience) evoke an evolutionary defense mechanism capable of embracing distractions to eliminate thoughts of death (Pysczynski, Greenberg, & Solomon, 1999). Thirty participants were primed with either reminders of their own death or reminders of a painful experience. Participants then read a neutral passage while self-reporting episodes of mind wandering and while responding to probes inquiring the status of their level of awareness. It was predicted that participants primed to be mortality salient would be caught by probes and mind wander less frequently due to increased engagement in the text in order to distract themselves from notions of their mortal vulnerability. The results partially confirm these predictions: All participants engaged in mind wandering to a comparable extent. Mortality salience-primed individuals self-reported far fewer instances of mind wandering than individuals who received a control (pain) prime, suggesting that reminders of death affect the ability to realize that mind wandering is happening

Context-specific activations are a hallmark of the neural basis of individual differences in general executive function

Common executive functioning (cEF) is a domain-general factor that captures shared variance in performance across diverse executive function tasks. To investigate the neural mechanisms of individual differences in cEF (e.g., goal maintenance, biasing), we conducted the largest fMRI study of multiple executive tasks to date (N = 546). Group average activation during response inhibition (antisaccade task), working memory updating (keep track task), and mental set shifting (number–letter switch task) overlapped in classic cognitive control regions. However, there were no areas across tasks that were consistently correlated with individual differences in cEF ability. Although similar brain areas are recruited when completing different executive function tasks, activation levels of those areas are not consistently associated with better performance. This pattern is inconsistent with a simple model in which higher cEF is associated with greater or less activation of a set of control regions across different task contexts; however, it is potentially consistent with a model in which individual differences in cEF primarily depend on activation of domain-specific targets of executive function. Brain features that explain commonalities in executive function performance across tasks remain to be discovered

The Relationship Between Resting State Network Connectivity and Individual Differences in Executive Functions

The brain is organized into a number of large networks based on shared function, for example, high-level cognitive functions (frontoparietal network), attentional capabilities (dorsal and ventral attention networks), and internal mentation (default network). The correlations of these networks during resting-state fMRI scans varies across individuals and is an indicator of individual differences in ability. Prior work shows higher cognitive functioning (as measured by working memory and attention tasks) is associated with stronger negative correlations between frontoparietal/attention and default networks, suggesting that increased ability may depend upon the diverging activation of networks with contrasting function. However, these prior studies lack specificity with regard to the higher-level cognitive functions involved, particularly with regards to separable components of executive function (EF). Here we decompose EF into three factors from the unity/diversity model of EFs: Common EF, Shifting-specific EF, and Updating-specific EF, measuring each via factor scores derived from a battery of behavioral tasks completed by 250 adult participants (age 28) at the time of a resting-state scan. We found the hypothesized segregated pattern only for Shifting-specific EF. Specifically, after accounting for one’s general EF ability (Common EF), individuals better able to fluidly switch between task sets have a stronger negative correlation between the ventral attention network and the default network. We also report non-predicted novel findings in that individuals with higher Shifting-specific abilities exhibited more positive connectivity between frontoparietal and visual networks, while those individuals with higher Common EF exhibited increased connectivity between sensory and default networks. Overall, these results reveal a new degree of specificity with regard to connectivity/EF relationships

Whole-cortex mapping of common genetic influences on depression and a social deficits dimension

Social processes are associated with depression, particularly understanding and responding to others, deficits in which can manifest as callousness/unemotionality (CU). Thus, CU may reflect some of the genetic risk to depression. Further, this vulnerability likely reflects the neurological substrates of depression, presenting biomarkers to capture genetic vulnerability of depression severity. However, heritability varies within brain regions, so a high-resolution genetic perspective is needed. We developed a toolbox that maps genetic and environmental associations between brain and behavior at high resolution. We used this toolbox to estimate brain areas that are genetically associated with both depressive symptoms and CU in a sample of 258 same-sex twin pairs from the Colorado Longitudinal Twin Study (LTS). We then overlapped the two maps to generate coordinates that allow for tests of downstream effects of genes influencing our clusters. Genetic variance influencing cortical thickness in the right dorsal lateral prefrontal cortex (DLFPC) sulci and gyri, ventral posterior cingulate cortex (PCC), pre-somatic motor cortex (PreSMA), medial precuneus, left occipital-temporal junction (OTJ), parietal-temporal junction (PTJ), ventral somatosensory cortex (vSMA), and medial and lateral precuneus were genetically associated with both depression and CU. Split-half replication found support for both DLPFC clusters. Meta-analytic term search identified "theory of mind", "inhibit", and "pain" as likely functions. Gene and transcript mapping/enrichment analyses implicated calcium channels. CU reflects genetic vulnerability to depression that likely involves executive and social functioning in a distributed process across the cortex. This approach works to unify neuroimaging, neuroinformatics, and genetics to discover pathways to psychiatric vulnerability.</p

Context-specific activations are a hallmark of the neural basis of individual differences in general executive function

Common executive functioning (cEF) is a domain-general factor that captures shared variance in performance across diverse executive function tasks. To investigate the neural mechanisms of individual differences in cEF (e.g., goal maintenance, biasing), we conducted the largest fMRI study of multiple executive tasks to date (N = 546). Group average activation during response inhibition (antisaccade task), working memory updating (keep track task), and mental set shifting (number&ndash;letter switch task) overlapped in classic cognitive control regions. However, there were no areas across tasks that were consistently correlated with individual differences in cEF ability. Although similar brain areas are recruited when completing different executive function tasks, activation levels of those areas are not consistently associated with better performance. This pattern is inconsistent with a simple model in which higher cEF is associated with greater or less activation of a set of control regions across different task contexts; however, it is potentially consistent with a model in which individual differences in cEF primarily depend on activation of domain-specific targets of executive function. Brain features that explain commonalities in executive function performance across tasks remain to be discovered.</p

Adjustments in Torque Steadiness During Fatiguing Contractions Are Inversely Correlated With IQ in Persons With Multiple Sclerosis

Fatigue is one of the most debilitating symptoms of multiple sclerosis (MS), and the underlying mechanisms are poorly understood. When exposed to a physical or cognitive challenge, individuals with MS tend to exhibit greater declines in task performance (performance fatigability) and increased levels of self-reported fatigue (perceived fatigability), but these effects may be attenuated by greater intellectual capacity. The purpose of our study was to examine the influence of intelligence on fatigability in persons with MS. We hypothesized that greater intellectual capacity confers some protection against heightened levels of fatigue and fatigability associated with MS. Twelve adults with relapsing-remitting MS were compared with 12 control (CO) subjects who were matched for age, sex, and premorbid intellectual capacity. Performance fatigability was measured as the decline in maximal voluntary contraction (MVC) torque after 60 isometric contractions (10 s contraction at 25% MVC, 5 s rest) performed with the knee extensor muscles. Perceived fatigability was assessed with the modified fatigue impact scale (MFIS) questionnaire (trait fatigability) and the Borg rating of perceived exertion (RPE, state fatigability). Persons with MS reported greater MFIS scores (MS: 43 ± 14; CO: 11 ± 8, P ≤ 0.001). Initial MVC torque for the knee extensors did not differ between the groups (MS: 112 ± 38 N⋅m; CO: 107 ± 44 N⋅m) and the decline (performance fatigability) was similar for both groups (MS: -16 ± 19 N⋅m; CO: -13 ± 16 N⋅m). RPE increased during the fatiguing contraction for both groups (P &lt; 0.001) but was significantly greater in magnitude (main effect for group, P = 0.03) and increased more for the MS group (group × time interaction, P = 0.05). Torque steadiness declined during the fatiguing contractions (main effect for time, P = 0.05) and was less steady for the MS group (main effect for group, P = 0.02). Performance and full-4 IQ was correlated with the decline in torque steadiness for the MS group (r = -0.63, P &lt; 0.05; r = -0.64, P &lt; 0.05). Intellectual capacity was not associated with fatigability in persons with MS but was associated with adjustments in muscle activation during the fatiguing contractions

On the Neural Basis of Individual Differences in Executive Function: a Series of Studies of the Resting Brain

Executive functions (EFs) are a thoroughly characterized set of high-level cognitive abilities that contribute to a person\u27s ability to pursue, maintain, and modify goals. A popular theoretical model of EFs - the unity and diversity model - describes the variety of laboratory tasks used to measure EF as having shared components (unity) and components specific to subsets of tasks (diversity). A fundamental question in the field of cognitive neuroscience is what brain characteristics underlie the wide array of high-level cognitive skills and abilities, like the unity and diversity aspects of EF, that vary across the population but are stable within an individual. The development of methodologies such as functional magnetic resonance imaging (fMRI) has contributed to a surge in interest in this fundamental question. Resting-state fMRI, in particular, characterizes the stable oscillatory behavior of the blood oxygen level dependent signal when individuals are not directed overtly to perform a particular task. As such, resting-state fMRI is a non-invasive and minimally-demanding protocol offering the potential to make predictions about individual differences in cognitive functioning. We present results from several resting-state analyses of two large data sets (n = 91 and 251). Participants in each sample were scanned without being overtly directed toward a particular mental task set and administered a battery of EF tasks that measured three EF constructs from the unity and diversity model - the general ability to maintain goals and task sets (common EF), abilities related to fluidly shifting between task sets (shifting-specific EF), and the ability to add to or delete from the contents of working memory (updating-specific EF). The resting-state analyses used here quantify the dynamics of the resting brain at two complementary spatial scales - at the level of networks and individual regions. Taking the results of these network and regional connectivity analyses together, we provide a new perspective on the neural bases of EFs that complements our understanding of the mechanisms of cognitive control (as assessed using the computational modeling approach) and the areas implicated in online cognitive control (as assessed by the brain mapping approach via fMRI studies of demanding versus non-demanding conditions). First, individual differences in common EF were associated with the intensity of the frontoparietal network at rest and connectivity among networks of regions implicated in high level cognition (both task-positive and task-negative networks). Because common EF captures variance in a wide array of cognitive tasks, these features perhaps underlie the unity of the neural basis of EFs. The diversity aspects from the unity and diversity model of EF are also associated with variation in separable neural substrates as assessed by resting-state connectivity. Individual differences in shifting-specific EF were associated with a more spatially distributed set of resting-state connectivity measures than task-based neuroimaging studies may lead one to believe, for example, the spatial extent of a network of regions implicated in top-down biasing and the diversity of connections in sensorimotor cortex. Individual differences in updating-specific EF are not supported by variation in resting-state networks in the way common EF and shifting-specific EF are but rather by variation in a limited set of graph theoretic properties of individual regions. Some results for updating-specific EF are novel, such as a less integrated frontal pole being associated with higher updating-specific EF ability, while others are in agreement with findings from the computation modeling literature which suggests updating depends upon connectivity of dorsolateral prefrontal cortex. Our work builds upon those findings by showing that not only do the mechanisms of working memory updating depend upon a certain type of connectivity, but variation in the degree t

Individual Differences in Resting-­‐state Functional MRI are Relevant to the Unity and Diversity of Executive Function

Resting-state functional MRI (rs-fMRI) is thought to reflect the intrinsic functional organization of the brain. Studies of group differences in measures of rs-MRI are pervasive throughout the field of cognitive neuroscience and clinical neuropsychology, but the relationship between the resting state of the brain and individual differences in performance on psychological tasks in a normal population remains poorly understood. Moreover, the limited available research fails to adequately relate individual differences in the resting brain to theoretically motivated constructs that are thought to relate to underlying processes responsible for humans\u27 ability to regulate thoughts and actions (i.e. - executive functions). Ninety-one college-aged participants completed a six-minute resting state fMRI scan and a battery of tasks measuring important aspects of executive function (see Miyake \u26 Friedman, 2012): inhibition of a prepotent response (antisaccade task), task set shifting (category switching task), and working memory updating (keep-track task). Using Independent Components Analysis (ICA), we identified several networks of regions (Intrinsic Connectivity Networks, ICNs) with temporally correlated time courses. We found that 1. individuals who activated subsystems of the default network to a greater degree had higher common executive function and working memory updating and 2. individuals who activated right and left frontoparietal control network to a greater degree had higher task set shifting and working memory updating, respectively. Additional predictors of working memory updating were the degree to which individuals\u27 left frontoparietal control ICN was negatively correlated with a subset of regions from the default mode ICN and also the degree to which individuals\u27 right frontoparietal control ICN was positively correlated with a different subset of regions from the default mode ICN. Finally, we employed a recent methodology (Dual Regression) to explore areas associated with an ICN that covary with individual differences in executive function. Dual regression revealed that covariance of four regions along with ICNs predicted EF: increased presence of right anterior prefrontal cortex in the dmPFC subsystem of the default network predicted higher common EF, increased presence of left lateral parietal region in the right frontoparietal control network predicted higher task set shifting, and increased presence of left middle frontal gyrus and postero-medial prefrontal cortex in the left frontoparietal control network predicted higher working memory updating. The results of the current study have important implications for our understanding of executive function processes and individual differences in the brain at rest. In particular, we discuss how underlying brain processes responsible for executive function performance likely sculpt the intrinsic functional organization of the brain over time and to a different degree based on skill

Eye movements during mindless reading

Mindless reading occurs when the eyes continue moving across the page even though the mind is thinking about something unrelated to the text. Despite how commonly it occurs, very little is known about mindless reading. The present experiment examined eye movements during mindless reading. Comparisons of fixation-duration measures collected during intervals of normal reading and intervals of mindless reading indicate that fixations during the latter were longer and less affected by lexical and linguistic variables than fixations during the former. Also, eye movements immediately preceding self-caught mind wandering were especially erratic. These results suggest that the cognitive processes that guide eye movements during normal reading are not engaged during mindless reading. We discuss the implications of these findings for theories of eye movement control in reading, for the distinction between experiential awareness and meta-awareness, and for reading comprehension

The Relationship Between Resting State Network Connectivity and Individual Differences in Executive Functions

The brain is organized into a number of large networks based on shared function, for example, high-level cognitive functions (frontoparietal network), attentional capabilities (dorsal and ventral attention networks), and internal mentation (default network). The correlations of these networks during resting-state fMRI scans varies across individuals and is an indicator of individual differences in ability. Prior work shows higher cognitive functioning (as measured by working memory and attention tasks) is associated with stronger negative correlations between frontoparietal/attention and default networks, suggesting that increased ability may depend upon the diverging activation of networks with contrasting function. However, these prior studies lack specificity with regard to the higher-level cognitive functions involved, particularly with regards to separable components of executive function (EF). Here we decompose EF into three factors from the unity/diversity model of EFs: Common EF, Shifting-specific EF, and Updating-specific EF, measuring each via factor scores derived from a battery of behavioral tasks completed by 250 adult participants (age 28) at the time of a resting-state scan. We found the hypothesized segregated pattern only for Shifting-specific EF. Specifically, after accounting for one’s general EF ability (Common EF), individuals better able to fluidly switch between task sets have a stronger negative correlation between the ventral attention network and the default network. We also report non-predicted novel findings in that individuals with higher Shifting-specific abilities exhibited more positive connectivity between frontoparietal and visual networks, while those individuals with higher Common EF exhibited increased connectivity between sensory and default networks. Overall, these results reveal a new degree of specificity with regard to connectivity/EF relationships.</p