Elizabeth A. Olson

White matter integrity predicts delay discounting behavior in 9-to 23-year-olds: A diffusion tensor imaging study

Healthy participants (n = 79), ages 9–23, completed a delay discounting task assessing the extent to which the value of a monetary reward declines as the delay to its receipt increases. Diffusion tensor imaging (DTI) was used to evaluate how individual differences in delay discounting relate to variation in fractional anisotropy (FA) and mean diffusivity (MD) within whole-brain white matter using voxel-based regressions. Given that rapid prefrontal lobe development is occurring during this age range and that functional imaging studies have implicated the prefrontal cortex in discounting behavior, we hypothesized that differences in FA and MD would be associated with alterations in the discounting rate. The analyses revealed a number of clusters where less impulsive performance on the delay discounting task was associated with higher FA and lower MD. The clusters were located primarily in bilateral frontal and temporal lobes and were localized within white matter tracts, including portions of the inferior and superior longitudinal fasciculi, anterior thalamic radiation, uncinate fasciculus, inferior fronto-occipital fasciculus, corticospinal tract, and splenium of the corpus callosum. FA increased and MD decreased with age in the majority of these regions. Some, but not all, of the discounting/DTI associations remained significant after controlling for age. Findings are discussed in terms of both developmental and age-independent effects of white matter organization on discounting behavior.

Tower of london performance in healthy adolescents: The development of planning skills and associations with self-reported inattention and impulsivity

Studies have investigated planning skill development using the Tower of London (TOL). Reports conflict regarding maturational trajectories and associations with IQ, other executive functions, and impulsivity. A convenience sample of 9- to 20-year-olds completed the TOL and other measures. TOL accuracy improved until ages 15–17. Digit span backwards (DSB), response inhibition, and IQ were correlated with TOL performance. DSB contributed to TOL accuracy above and beyond age and IQ. Inhibitory control and DSB both contributed to the modulation of planning times across problems. Self-reported inattention and hyperactivity were associated with low performance. Task approaches reflecting planning and psychometric issues are discussed.

Physical Exercise Habits Correlate with Gray Matter Volume of the Hippocampus in Healthy Adult Humans

Physical activity facilitates neurogenesis of dentate cells in the rodent hippocampus, a brain region critical for memory formation and spatial representation. Recent findings in humans also suggest that aerobic exercise can lead to increased hippocampal volume and enhanced cognitive functioning in children and elderly adults. However, the association between physical activity and hippocampal volume during the period from early adulthood through middle age has not been effectively explored. Here, we correlated the number of minutes of self-reported exercise per week with gray matter volume of the hippocampus using voxel-based morphometry (VBM) in 61 healthy adults ranging from 18 to 45 years of age. After controlling for age, gender, and total brain volume, total minutes of weekly exercise correlated significantly with volume of the right hippocampus. Findings highlight the relationship between regular physical exercise and brain structure during early to middle adulthood.

Microstructure of frontoparietal connections predicts individual resistance to sleep deprivation

Sleep deprivation (SD) can degrade cognitive functioning, but growing evidence suggests that there are large individual differences in the vulnerability to this effect. Some evidence suggests that baseline differences in the responsiveness of a fronto-parietal attention system that is activated during working memory (WM) tasks may be associated with the ability to sustain vigilance during sleep deprivation. However, the neurocircuitry underlying this network remains virtually unexplored. In this study, we employed diffusion tensor imaging (DTI) to investigate the association between the microstructure of the axonal pathway connecting the frontal and parietal regions--i.e., the superior longitudinal fasciculus (SLF)--and individual resistance to SD. Thirty healthy participants (15 males) aged 20-43 years underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) at rested wakefulness prior to a 28-hour period of SD. Task-related fronto-parietal fMRI activation clusters during a Sternberg WM Task were localized and used as seed regions for probabilistic fiber tractography. DTI metrics, including fractional anisotropy, mean diffusivity, axial and radial diffusivity were measured in the SLF. The psychomotor vigilance test (PVT) was used to evaluate resistance to SD. We found that activation in the left inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) positively correlated with resistance. Higher fractional anisotropy of the left SLF comprising the primary axons connecting IPL and DLPFC was also associated with better resistance. These findings suggest that individual differences in resistance to SD are associated with the functional responsiveness of a fronto-parietal attention system and the microstructural properties of the axonal interconnections.

Evidence for a unimodal somatosensory attention system

Extinction is generally viewed as a disorder of selective attention for spatial locations. Recent physiologic, behavioral and lesion studies view spatial locations as a complex construct in which multiple modalities and motor systems are integrated. Accordingly, cross-modal and sensory-motor conditions often modify extinction. In a patient with tactile extinction, we tested the hypothesis that attentional deficits can also be confined to a specific sensory modality. Using objectively and subjectively balanced tactile stimuli and signal detection analysis, we found that our patients contralesional tactile discrimination was not modulated by proprioceptive or visual input or by movement. By contrast, increasing the salience of the contralesional tactile stimuli did improve her contralesional tactile discrimination, consistent with our hypothesis that she suffered from a modality-specific attentional deficit. Additionally, she did not have any evidence of visual extinction, again bolstering our claim that her extinction was confined to touch. These data suggest that in addition to polymodal and sensory-motor attentional systems, spatial attention also operates on specific sensations. We also advocate the use of signal detection analysis, a method that has been surprisingly neglected in extinction research.

Sleep difficulties are associated with increased symptoms of psychopathology

Abstract Sleep problems often co-occur with psychopathological conditions and affective dysregulation. Individuals with mood disorders have significantly higher rates of sleep disturbances than healthy individuals, and among those with mood disorders, sleep problems are associated with lower rates of remission and response to treatment. Sleep disruption may itself be a risk factor for various forms of psychopathology, as experimental sleep deprivation has been found to lead to increased affective, cognitive, and somatic symptoms within healthy volunteers. However, little is known about the relationship between recurring sleep complaints in a naturalistic environment and symptoms of psychopathology among healthy individuals. In the present study, 49 healthy adults (21 males and 28 females) reported sleep quality and completed the Personality Assessment Inventory, a standardized self-report assessment of symptoms of psychopathology. Consistent with prior published findings during total sleep deprivation, individuals endorsing self-reported naturally occurring sleep problems showed higher scores on scales measuring somatic complaints, anxiety, and depression. Furthermore, the reported frequency of sleep disturbance was closely linked with the severity of self-reported symptoms. While causal directionality cannot be inferred, these findings support the notion that sleep and emotional functioning are closely linked.

Physical exercise and brain responses to images of high-calorie food.

Physical exercise has many health benefits, including improved cardiovascular fitness, lean muscle development, increased metabolism, and weight loss, as well as positive effects on brain functioning and cognition. Recent evidence suggests that regular physical exercise may also affect the responsiveness of reward regions of the brain to food stimuli. We examined whether the total number of minutes of self-reported weekly physical exercise was related to the responsiveness of appetite and food reward-related brain regions to visual presentations of high-calorie and low-calorie food images during functional MRI. Second, we examined whether such responses would correlate with self-reported food preferences. While undergoing scanning, 37 healthy adults (22 men) viewed images of high-calorie and low-calorie foods and provided desirability ratings for each food image. The correlation between exercise minutes per week and brain responses to the primary condition contrast (high-calorie>low-calorie) was evaluated within the amygdala, insula, and medial orbitofrontal cortex, brain regions previously implicated in responses to food images. Higher levels of exercise were significantly correlated with lower responsiveness within the medial orbitofrontal cortex and left insula to high-calorie foods. Furthermore, activation of these regions was positively correlated with preference ratings for high-calorie foods, particularly those with a savory flavor. These findings suggest that physical exercise may be associated with reduced activation in food-responsive reward regions, which are in turn associated with reduced preferences for unhealthy high-calorie foods. Physical exercise may confer secondary health benefits beyond its primary effects on cardiovascular fitness and energy expenditure.

Internet‐based cognitive behavior therapy for major depressive disorder: A randomized controlled trial

Prior research has shown that the Sadness Program, a technician‐assisted Internet‐based cognitive behavioral therapy (iCBT) intervention developed in Australia, is effective for treating major depressive disorder (MDD). The current study aimed to expand this work by adapting the protocol for an American population and testing the Sadness Program with an attention control group.

Daytime Sleepiness Is Associated With Reduced Integration of Temporally Distant Outcomes on the Iowa Gambling Task

Sleep deprivation is associated with performance decrements on some measures of executive functioning. For instance, sleep deprivation results in altered decision making on the Iowa Gambling Task. However, it is unclear which component processes of the task may be driving the effect. In this study, Iowa Gambling task performance was decomposed using the Expectancy-Valence model. Recent sleep debt and greater daytime sleepiness were associated with higher scores on the updating parameter, which reflects the extent to which recent experiences are emphasized over remote ones. Findings suggest that the effects of insufficient sleep on IGT performance are due to shortening of the time horizon over which decisions are integrated. These findings may have clinical implications in that individuals with sleep problems may not integrate more temporally distant information when making decisions.

Dorsal Anterior Cingulate Thickness Is Related to Alexithymia in Childhood Trauma-Related PTSD

Alexithymia, or “no words for feelings”, is highly prevalent in samples with childhood maltreatment and posttraumatic stress disorder (PTSD). The dorsal anterior cingulate cortex (dACC) has been identified as a key region involved in alexithymia, early life trauma, and PTSD. Functional alterations in the dACC also have been associated with alexithymia in PTSD. This study examined whether dACC morphology is a neural correlate of alexithymia in child maltreatment-related PTSD. Sixteen adults with PTSD and a history of childhood sexual abuse, physical abuse, or exposure to domestic violence, and 24 healthy controls (HC) completed the Toronto Alexithymia Scale 20 (TAS–20) and underwent magnetic resonance imaging. Cortical thickness of the dACC was measured using FreeSurfer, and values were correlated with TAS–20 scores, controlling for sex and age, in both groups. Average TAS–20 score was significantly higher in the PTSD than the HC group. TAS–20 scores were significantly positively associated with dACC thickness only in the PTSD group. This association was strongest in the left hemisphere and for TAS–20 subscales that assess difficulty identifying and describing feelings. We found that increasing dACC gray matter thickness is a neural correlate of greater alexithymia in the context of PTSD with childhood maltreatment. While findings are correlational, they motivate further inquiry into the relationships between childhood adversity, emotional awareness and expression, and dACC morphologic development in trauma-related psychopathology.