Exploring Cortical Attentional System by Using fMRI during a Continuous Perfomance Test

Functional magnetic resonance imaging (fMRI) was performed in eight healthy subjects to identify the localization, magnitude, and volume extent of activation in brain regions that are involved in blood oxygen level-dependent (BOLD) response during the performance of Conners' Continuous Performance Test (CPT). An extensive brain network was activated during the task including frontal, temporal, and occipital cortical areas and left cerebellum. The more activated cluster in terms of volume extent and magnitude was located in the right anterior cingulate cortex (ACC). Analyzing the dynamic trend of the activation in the identified areas during the entire duration of the sustained attention test, we found a progressive decreasing of BOLD response probably due to a habituation effect without any deterioration of the performances. The observed brain network is consistent with existing models of visual object processing and attentional control and may serve as a basis for fMRI studies in clinical populations with neuropsychological deficits in Conners' CPT performance

Large-scale intrinsic functional connectivity and attention in schizophrenia

It has been well-established that sustained attention and executive functioning are core deficits in schizophrenia (SZ). Growing evidence suggests that such attentional impairments may reflect disruptions in dominant intrinsic networks (INs). Functional network connectivity (FNC), described as the dependency between multiple INs, has revealed dysfunction among key INs in people with SZ. The objective of the current study was to test the hypothesis that SCZ would exhibit less specialized cognitive processing and therefore decreased FNC between dominant INs, and that any disruptions in FNC would predict neuropsychological profiles of attention. Methods: Thirty-five patients with SZ and thirty-three healthy controls (HC) were recruited for this study. Five minutes of eyes-closed resting-state fMRI (3T Trio scanner) was obtained for each participant. Resting-state scans were decomposed into 75 components using a group ICA suite (GIFT), and the FNC between all pair-wise components were obtained for each subject using the FNC toolbox. Participants were assessed using the Conners CPT II and the Wisconsin-card sorting task (WCST). Results: As expected, patients performed worse than HC on both tests of attention, and exhibited decreased FNC between default-mode subcomponents, a \u27salience\u27 (anterior cingulate and bilateral insulae) IN and basal ganglia IN; also, patients displayed increased FNC between a subcomponent of the DMN (anterior cingulate and bilateral middle frontal gyrus) and a frontal pole IN. Regression analyses showed that the aberrant FNC between specific component pairs predicted hit reaction time and clinical index scores on the CPT II and perseveration errors on the WCST. Conclusions: The current study highlights the importance of examining the organization of large-scale FNC between dominant INs to investigate attentional dysfunction in SZ. These results particularly highlight the importance of differentiating the subcomponents of the DMN in discriminating between HC and SZ. Future work should continue to address the role of these particular INs as they relate to cognitive ability and clinical symptoms in SZ, with the aim of establishing treatment interventions to improve, or \u27normalize\u27 the abnormal intrinsic functional connectivity observed in SZ

The Effect of Motor Imagery on Spinal Motor Neuron Excitability and Its Clinical Use in Physical Therapy

We investigated the influence of the imagined muscle contraction strengths on spinal motor neuron excitability in healthy volunteers. F‐wave was used for assessing spinal motor excitability. The F‐waves during motor imagery (MI) under 10, 30, 50, 70, and 100% maximal voluntary contractions (MVCs) were compared. Furthermore, we investigated changes of the F‐waves during motor imagery for 5 min. Motor imagery under 10, 30, 50, 70, and 100% maximal voluntary contractions can increase spinal motor neuron excitability. However, the imagined muscle contraction strengths were not involved in changes of spinal motor neuron excitability. Additionally, spinal motor neuron excitability after 5 min from onset of motor imagery returned to the rest level. Thus, in clinical use of motor imagery, slightly imagined muscle contraction strength is enough for facilitating spinal motor neuron excitability. Also, duration of motor imagery needs to be considered

Identification of neurobiological mechanisms associated with attention deficits in adults post traumatic brain injury

Traumatic Brain Injury (TBI) is one of the major public health concerns with approximately 70 million new cases occurring worldwide per year. It is often caused by a forceful bump, blow, or jolt to the head, resulting in brain tissue damage and normal brain functions disruption. All grades of TBI, ranging from mild to severe, can cause wide-ranging and long-term effects on affected individuals, resulting in physical impairments, and neurocognitive consequences that permanently affect their abilities to perform daily activities. Attention deficits are the most common persisting neurocognitive consequences following TBI, which significantly contribute to poor academic and social functioning, and life-long learning difficulties of affected individuals. However, attention deficits have been evaluated and treated based on symptom endorsements from subjective observations, with few therapeutic interventions successfully translated to the clinic. The consensus regarding appropriate evaluation and treatment of TBI induced attention deficits in this cohort is rather limited due to the lack of investigations of the neurobiological substrates associated with this syndrome. The overall aim of this dissertation research is to systematically investigate the neurobiological mechanisms associated with attention deficits in adults post TBI by utilizing multiple powerful neuroimaging techniques including the functional near-infrared spectroscopy (fNIRS) and multimodal magnetic resonance imaging (MRI), with an ultimate goal of translating hypothesis-driven neurobiological correlates into the quantitatively measurable biomarkers for diagnosis of TBI-induced attention deficits and development of more refined long-term treatment and intervention strategies. This dissertation research is conducted through three specific projects. Project 1 focuses on the investigation of brain functional patterns including the regional cortical brain activation and between-regional pairwise functional connectivity responding to visual sustained attention processing in individuals with and without TBI, by utilizing the fNIRS technique. Project 2 continues the examination of brain functional patterns by assessing the whole brain network topological properties responding to visual sustained attention processing in a larger sample of individuals with and without TBI, by utilizing the functional MRI technique and a graph theoretic approach. Project 3, on the other hand, investigates the brain structural characteristics based on the same sample involved in Project 2, by utilizing the structural MRI and diffusion tensor imaging techniques. For all these three projects, the differences of these brain imaging measures are compared between the groups of TBI and control. Correlation analyses are further conducted between those brain imaging measures which shows significant between-group differences and attention-related behaviors. In addition, Project 3 additionally investigates gender-specific patterns of the altered brain structural properties in TBI patients, relative to controls. The outcome of this novel and valuable dissertation research may shed light on the neural mechanisms of attention deficits in adults post TBI, and may suggest the neurobiological targets for treatment of this severe and common condition. It may also provide important neural foundation for future research to develop effective rehabilitation strategies to improve attention processing in adults post TBI

Neurofunctional Abnormalities during Sustained Attention in Severe Childhood Abuse

<div><p>Childhood maltreatment is associated with adverse affective and cognitive consequences including impaired emotion processing, inhibition and attention. However, the majority of functional magnetic resonance imaging (fMRI) studies in childhood maltreatment have examined emotion processing, while very few studies have tested the neurofunctional substrates of cognitive functions and none of attention. This study investigated the association between severe childhood abuse and fMRI brain activation during a parametric sustained attention task with a progressively increasing load of sustained attention in 21 medication-naïve, drug-free young people with a history of childhood abuse controlling for psychiatric comorbidities by including 19 psychiatric controls matched for psychiatric diagnoses, and 27 healthy controls. Behaviorally, the participants exposed to childhood abuse showed increased omission errors in the task which correlated positively trend-wise with the duration of their abuse. Neurofunctionally, the participants with a history of childhood abuse, but not the psychiatric controls, displayed significantly reduced activation relative to the healthy controls during the most challenging attention condition only in typical attention regions including left inferior and dorsolateral prefrontal cortex, insula and temporal areas. We therefore show for the first time that severe childhood abuse is associated with neurofunctional abnormalities in key ventral frontal-temporal sustained attention regions. The findings represent a first step towards the delineation of abuse-related neurofunctional abnormalities in sustained attention, which may help in the development of effective treatments for victims of childhood abuse.</p></div

Dietary Long-Chain Omega-3 Fatty Acids Are Related to Impulse Control and Anterior Cingulate Function in Adolescents

Impulse control, an emergent function modulated by the prefrontal cortex (PFC), helps to dampen risky behaviors during adolescence. Influences on PFC maturation during this period may contribute to variations in impulse control. Availability of omega-3 fatty acids, an essential dietary nutrient integral to neuronal structure and function, may be one such influence. This study examined whether intake of energy-adjusted long-chain omega-3 fatty acids [eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)] was related to variation in impulse control and PFC activity during performance of an inhibitory task in adolescents (n = 87; 51.7% female, mean age 13.3 ± 1.1 years) enrolled in a longitudinal neuroimaging study. Intake of DHA + EPA was assessed using a food frequency questionnaire and adjusted for total energy intake. Inhibitory control was assessed using caregiver rating scale (BRIEF Inhibit subscale) and task performance (false alarm rate) on a Go/No-Go task performed during functional MRI. Reported intake of long-chain omega-3 was positively associated with caregiver ratings of adolescent ability to control impulses (p = 0.017) and there was a trend for an association between intake and task-based impulse control (p = 0.072). Furthermore, a regression of BOLD response within PFC during successful impulse control (Correct No-Go versus Incorrect No-Go) with energy-adjusted DHA + EPA intake revealed that adolescents reporting lower intakes display greater activation in the dorsal anterior cingulate, potentially suggestive of a possible lag in cortical development. The present results suggest that dietary omega-3 fatty acids are related to development of both impulse control and function of the dorsal anterior cingulate gyrus in normative adolescent development. Insufficiency of dietary omega-3 fatty acids during this developmental period may be a factor which hinders development of behavioral control