Cross-task and cross-manipulation stability in shifting the decision criterion.

In recognition memory experiments participants must discriminate between old and new items, a judgment influenced by response bias. Research has shown substantial individual differences in the extent to which people will strategically adjust their response bias to diagnostic cues such as the prior probability of an old item. Despite this significant between subject variability, shifts in bias have been found to be relatively predictive within individuals across memory tests. Experiment 1 sought to determine whether this predictability extends beyond memory. Results revealed that the amount a subject shifted response bias in a recognition memory task was significantly predictive of shifting in a visual perception task, suggesting that shifting can generalise outside of a specific testing domain. Experiment 2 sought to determine how predictive shifting would be across two manipulations well known to induce shifts in bias: a probability manipulation and a response payoff manipulation. A modest positive relationship between these two methods was observed, suggesting that shifting behaviour is relatively predictive across different manipulations of shifting. Overall, results from both experiments suggest that response bias shifting, like response bias setting, is a relatively stable behaviour within individuals despite changes in test domain and test manipulation.

Age-dependent changes in task-based modular organization of the human brain.

As humans age, cognition and behavior change significantly, along with associated brain function and organization. Aging has been shown to decrease variability in functional magnetic resonance imaging (fMRI) signals, and to affect the modular organization of human brain function. In this work, we use complex network analysis to investigate the dynamic community structure of large-scale brain function, asking how evolving communities interact with known brain systems, and how the dynamics of communities and brain systems are affected by age. We analyze dynamic networks derived from fMRI scans of 104 human subjects performing a word memory task, and determine the time-evolving modular structure of these networks by maximizing the multislice modularity, thereby identifying distinct communities, or sets of brain regions with strong intra-set functional coherence. To understand how community structure changes over time, we examine the number of communities as well as the flexibility, or the likelihood that brain regions will switch between communities. We find a significant positive correlation between age and both these measures: younger subjects tend to have less fragmented and more coherent communities, and their brain regions tend to change communities less often during the memory task. We characterize the relationship of community structure to known brain systems by the recruitment coefficient, or the probability of a brain region being grouped in the same community as other regions in the same system. We find that regions associated with cingulo-opercular, somatosensory, ventral attention, and subcortical circuits have a significantly higher recruitment coefficient in younger subjects. This indicates that the within-system functional coherence of these specific systems during the memory task declines with age. Such a correspondence does not exist for other systems (e.g. visual and default mode), whose recruitment coefficients remain relatively uniform across ages. These results confirm that the dynamics of functional community structure vary with age, and demonstrate methods for investigating how aging differentially impacts the functional organization of different brain systems.

Sensorimotor gating deficits in adults with autism.

BACKGROUND: Prepulse inhibition (PPI) is an operational measure of sensorimotor gating and is impaired in a family of neuropsychiatric disorders characterized by abnormalities of inhibitory function. Adults with autistic disorder (AD) exhibit clinical features of inhibitory deficits, such as restrictive and repetitive behaviors, that may be explained by deficits in sensorimotor gating. METHODS: Acoustic startle reactivity, habituation, and PPI (30-, 60-, 120-msec interstimulus intervals) were assessed in 14 adult men diagnosed with AD and 16 typically developing normal comparison (NC) participants. All participants were administered measures of intelligence and frontal-executive functioning. RESULTS: Adults with AD exhibited significantly less PPI in the 60-msec condition than NC participants, which was correlated with increased ratings of restricted and repetitive behaviors. The groups did not differ on measures of startle amplitude or overall habituation. There was, however, a significant group-by-block habituation effect. Furthermore, PPI was not related to intelligence but was moderately associated with performance on a measure of frontal-executive functioning. CONCLUSIONS: Adults with AD have sensorimotor gating deficits similar to other neurodevelopmental disorders, implicating a failure of normal inhibitory regulation of sensory, motor, and attentional mechanisms. Thus, PPI deficits may be indirectly linked to one of the hallmark features of AD.

A comparison of motor delays in young children: autism spectrum disorder, developmental delay, and developmental concerns.

This study assessed motor delay in young children 21-41 months of age with autism spectrum disorder (ASD), and compared motor scores in children with ASD to those of children without ASD. Fifty-six children (42 boys, 14 girls) were in three groups: children with ASD, children with developmental delay (DD), and children with developmental concerns without motor delay. Descriptive analysis showed all children with ASD had delays in gross motor skills, fine motor skills, or both. Children with ASD and children with DD showed significant impairments in motor development compared to children who had developmental concerns without motor delay. Motor scores of young children with ASD did not differ significantly on motor skill measures when compared to young children with DD.

P3a from visual stimuli: task difficulty effects.

The P3a event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (target, standard, distracter) in which participants responded only to the target. Discrimination task difficulty between the target and the standard was manipulated by varying the size of the standard stimulus circle relative to a constant target stimulus circle across three conditions (easy, medium, hard). A large checkerboard pattern was employed for the distracter stimulus across all tasks. Error rate and response time increased with increases in task difficulty, so that the task difficulty manipulation was successful. Distracter P3a amplitude increased and target P3b decreased somewhat with increases in task difficulty. The findings suggest that increased perceptual discrimination difficulty between the target and standard stimuli increases P3a amplitude. Theoretical implications are discussed.

Examining the relationship between executive functions and restricted, repetitive symptoms of Autistic Disorder.

The executive function theory was utilized to examine the relationship between cognitive process and the restricted, repetitive symptoms of Autistic Disorder (AD). Seventeen adults with AD were compared to 17 nonautistic controls on a new executive function battery (Delis-Kaplin Executive Function Scales). Restricted, repetitive symptoms were measured by a variety of instruments (i.e., the Autism Diagnostic Observation Schedule, Autism Diagnostic Interview-Revised, Gilliam Autism Rating Scale, and the Aberrant Behavior Checklist). The study replicated the executive function profile that has been reported in adults with AD. In addition to the replication findings, the study found several executive processes (i.e., cognitive flexibility, working memory, and response inhibition) were highly related to the restrictive, repetitive symptoms of AD; whereas, other executive process (i.e., planning and fluency) were not found to be significantly correlated with restricted, repetitive symptoms. Similarly, we found an executive function model consisting of relative strengths and deficits was the best predictor of restricted, repetitive symptoms of autism. The implications for the executive function theory and how the theory predicts core symptoms of autism are discussed.

One dataset, many conclusions: BOLD variability's complicated relationships with age and motion artifacts.

In recent years, the variability of the blood-oxygen level dependent (BOLD) signal has received attention as an informative measure in its own right. At the same time, there has been growing concern regarding the impact of motion in fMRI, particularly in the domain of resting state studies. Here, we demonstrate that, not only does motion (among other confounds) exert an influence on the results of a BOLD variability analysis of task-related fMRI data-but, that the exact method used to deal with this influence has at least as large an effect as the motion itself. This sensitivity to relatively minor methodological changes is particularly concerning as studies begin to take on a more applied bent, and the risk of mischaracterizing the relationship between BOLD variability and various individual difference variables (for instance, disease progression) acquires real-world relevance.

Latent relationships of fluid, visual, and simultaneous cognitive tasks.

Horn's 1989 fluid intelligence and Luria's 1966 simultaneous processing have been represented in various cognitive assessment batteries. Although related, these concepts are purported to measure distinct cognitive functions; fluid intelligence refers to deductive reasoning whereas simultaneous processing refers to understanding complex relationships among gestalts. The current study explored the factor structure of known fluid and simultaneous tests along with visually complex new tests. A total of 56 children in Grades 1 through 5 were administered tests from the Kaufman Assessment Battery for Children, Elliott's Differential Abilities Scales, and two experimental tasks. Findings suggest that (1) the two experimental subtests were psychometrically viable, (2) when analyzed as a two-factor structure, fluid and visual processing components were pronounced, and (3) when analyzed as a single-factor structure, simultaneous processing emerged. These findings indicate simultaneous processing may be a blend of fluid and visual components.

Levels of gross and fine motor development in young children with autism spectrum disorder.

The purpose of this study was to compare levels of gross motor (GM) and fine motor (FM) development in young children with autism spectrum disorder (ASD), and to compare their levels of GM and FM development with children with developmental delay (DD) without ASD. Thirty-eight children (ASD group: n = 19; DD group: n = 19) between 21 and 41 months of age were assessed using the Peabody Developmental Motor Scales, Second Edition (PDMS-2). Using PDMS-2 classifications as well as differences between standard scores, each child was placed in one of three motor profiles based on the child's relative levels of GM and FM skills (GM = FM,GM>FM, and GM

Concurrent validity of the Bayley Scales of Infant Development II Motor Scale and the Peabody Developmental Motor Scales-2 in children with developmental delays.

PURPOSE: The purpose of this study was to explore concurrent validity of the age equivalent and standard scores of the Bayley Scales of Infant Development II (BSID II) Motor Scale and the Peabody Developmental Motor Scales-2 (PDMS-2), including correlations and clinical agreement between the scores of the two tests. METHODS: One hundred ten children aged three to 41 months who were referred to an early childhood evaluation program because of concerns about their development were administered both the BSID II Motor Scale and the PDMS-2 as part of their developmental evaluations. RESULTS: The correlation coefficients were high to very high for age-equivalent scores, and the Locomotion Subscale had the closest agreement with the BSID II Motor Scale age equivalent. The correlation coefficients were moderate to high for standard scores, and there was only slight agreement between the tests for standard score categories. More than 75% of the 70 children in this study whose scores on the BSID II supported eligibility for services based on scores at least two SD below the mean of the test would not have qualified for services if the PDMS-2 standard scores alone were used to assess their eligibility. Approximately half the children who showed appropriate total motor performance on the PDMS-2 were classified as delayed on the BSID II Motor Scale. CONCLUSIONS: The study supports concurrent validity of the tests only for certain subscale age-equivalent scores, particularly the BSID II Motor Scale with the PDMS-2 Locomotion Subscale. The current findings suggest that the standard scores show poor agreement and have low concurrent validity. There are marked differences in the standard scores of the two tests that may affect a child's eligibility for services in some states, and therapists should be cautious when making clinical decisions based solely on standard scores of one test.