Test-retest reliability of evoked heat stimulation bold functional magnetic resonance imaging

To date, the blood oxygenated-level dependent (BOLD) functional magnetic resonance imaging (fMRI) technique has enabled an objective and deeper understanding of pain processing mechanisms embedded within the human central nervous system (CNS). In order to further comprehend the benefits and limitations of BOLD fMRI in the context of pain as well as the corresponding subjective pain ratings, we evaluated the univariate response, test-retest reliability and confidence intervals (CIs) at the 95% level of both data types collected during evoked stimulation of 40°C (non-noxious), 44°C (mildly noxious) and a subject-specific temperature eliciting a 7/10 pain rating. The test-retest reliability between two scanning sessions was determined by calculating group-level interclass correlation coefficients and at the single-subject level. Across the three stimuli, we initially observed a graded response of increasing magnitude for both visual analogue scale (VAS) pain ratings and fMRI data. Test-retest reliability was observed to be highest for VAS pain ratings obtained during the 7/10 pain stimulation (intraclass correlation coefficient (ICC) = 0.938), while ICC values of pain fMRI data for a distribution of CNS structures ranged from 0.5 to 0.859 (p < 0.05). Importantly, the upper and lower CI bounds reported herein could be utilized in subsequent trials involving healthy volunteers to hypothesize the magnitude of effect required to overcome inherent variability of either VAS pain ratings or BOLD responses evoked during innocuous or noxious thermal stimulation

A Perspective on Human Movement Variability With Applications in Infancy Motor Development

Movement variability is considered essential to typical motor development. However, multiple theoretical perspectives and measurement tools have limited interpretation of the importance of movement variability in biological systems. The complementary use of linear and nonlinear measures have recently allowed for the evaluation of not only the magnitude of variability but also the temporal structure of variability. As a result, the theoretical model of optimal movement variability was introduced. The model suggests that the development of healthy and highly adaptable systems relies on the achievement of an optimal state of variability. Alternatively, abnormal development may be characterized by a narrow range of behaviors, some of which may be rigid, inflexible, and highly predictable or, on the contrary, random, unfocused, and unpredictable. In the present review, this theoretical model is described as it relates to motor development in infancy and specifically the development of sitting posture

Reliability and Precision of Hip Proprioception Methods in Healthy Individuals

The underlying risk factors for female anterior cruciate ligament (ACL) injuries are likely multifactorial. Poor neuromuscular and biomechanical control of the lower limb appears to be a primary contributor to the female ACL injury mechanism. Neuromuscular and biomechanical characteristics of the hip may significantly contribute to lower extremity function, since hip position and motion has been found to influence knee position and loads. Afferent proprioceptive signals from mechanoreceptors in the ACL play a vital role in dynamic joint stability of the knee. The same principle is valid for maintaining dynamic stability of the hip, however there has been limited research examining proprioception of the hip. Prior to investigating the contribution of hip proprioception to knee injuries, the reliability and precision of the desired hip proprioception methods must be established. The goal of this study was to establish the intersession and intrasession reliability and precision of threshold to detect passive motion, force sense and active joint position sense tests of the hip in healthy individuals. The results of this study indicate that a reliable and precise method of measuring hip threshold to detect passive motion (TTDPM) has been established. Further investigation is warranted to develop reliable and precise measurement methods for force sense (FS) and active joint position sense (JPS) measurements of the hip

Multimodal imaging of human brain activity: rational, biophysical aspects and modes of integration

Until relatively recently the vast majority of imaging and electrophysiological studies of human brain activity have relied on single-modality measurements usually correlated with readily observable or experimentally modified behavioural or brain state patterns. Multi-modal imaging is the concept of bringing together observations or measurements from different instruments. We discuss the aims of multi-modal imaging and the ways in which it can be accomplished using representative applications. Given the importance of haemodynamic and electrophysiological signals in current multi-modal imaging applications, we also review some of the basic physiology relevant to understanding their relationship

A multimodal investigation in eye movements

While functional magnetic resonance imaging (fMRI) has identified which regions of interest (ROIs) are functionally active during a vergence movement (inward or outward eye rotation), task-modulated coactivation between ROIs is less understood. This study tests the following hypotheses: (1) significant task-modulated coactivation would be observed between the frontal eye fields (FEFs), the posterior parietal cortex (PPC), and the cerebellar vermis (CV); (2) significantly more functional activity and task-modulated coactivation would be observed in binocularly normal controls (BNCs) compared with convergence insufficiency (CI) subjects; and (3) after vergence training, the functional activity and task-modulated coactivation would increase in CIs compared with their baseline measurements. A block design of sustained fixation versus vergence eye movements stimulates activity in the FEFs, PPC, and CV. fMRI data from four CI subjects before and after vergence training are compared with seven BNCs. Functional activity is assessed using the blood oxygenation level dependent (BOLD) percent signal change. Task-modulated coactivation is assessed using an ROI-based task modulated coactivation analysis that reveals significant correlation between ROIs

Repeatability of Corticospinal and Spinal Measures during Lengthening and Shortening Contractions in the Human Tibialis Anterior Muscle

Elements of the human central nervous system (CNS) constantly oscillate. In addition, there are also methodological factors and changes in muscle mechanics during dynamic muscle contractions that threaten the stability and consistency of transcranial magnetic stimulation (TMS) and perpherial nerve stimulation (PNS) measures

Assessing the long-term sequelae of mild traumatic brain injury

A mild traumatic brain injury (mTBI), also known as a concussion, is defined as an injury that results in an alteration of consciousness or mental status. Previous studies have shown mTBI populations experience a number of chronic (\u3e 1 year) symptoms, such as sleep disturbances (e.g., sleep stage alterations), mood alterations (e.g., depressive symptoms), and cognitive alterations (e.g., poor concentration). The three chapters of this dissertation sought to explore these long-term sequelae and the possible interrelations between them. In the first experiment, sleep-dependent memory consolidation of neutral stimuli was probed in a chronic mTBI sample and a control, uninjured sample. I hypothesized memory consolidation would be reduced in the mTBI sample. However, sleep-dependent consolidation was found to be intact in the mTBI sample, despite differences in sleep architecture between groups. Given that risk for mood disorders is elevated following mTBI, in the second experiment, sleep-dependent memory consolidation of emotional images was assessed in groups that were similar to those assessed in Study 1, with the hypothesis that mTBI participants would have reduced consolidation. The mTBI group had reduced sleep-dependent memory consolidation (i.e., memory considation that occurred over a sleep period) but enhanced wake-dependent consolidation (i.e., memory consolidation that occurred over a wake period) of emotional (but not neutral) images. The mTBI group also unexpectedly exhibited a lack of emotion habituation (i.e., emotion desensitization). The third experiment attempted to replicate the latter (unexpected) finding (i.e., reductions in habituation in the mTBI group) while also probing physiological measures of emotion (e.g., heart rate deceleration), which provide an objective measure of emotion. I theorized that reduced habituation might increase the risk for mood disturbances in this population. I was not able to replicate findings of the second experiment, and, on the contrary, found mTBI participants had enhanced emotion habituation In the three experiments, we failed to find expected cognitive and emotional processing deficits in the mTBI samples. In future work, recruiting alternative subsamples of mTBI individuals (e.g., those with Post-concussive syndrome or those with 3 or more mTBIs) could provide insight into which individuals experience negative outcomes in the chronic stages of mTBI

High-density diffuse optical tomography for imaging human brain function

This review describes the unique opportunities and challenges for noninvasive optical mapping of human brain function. Diffuse optical methods offer safe, portable, and radiation free alternatives to traditional technologies like positron emission tomography or functional magnetic resonance imaging (fMRI). Recent developments in high-density diffuse optical tomography (HD-DOT) have demonstrated capabilities for mapping human cortical brain function over an extended field of view with image quality approaching that of fMRI. In this review, we cover fundamental principles of the diffusion of near infrared light in biological tissue. We discuss the challenges involved in the HD-DOT system design and implementation that must be overcome to acquire the signal-to-noise necessary to measure and locate brain function at the depth of the cortex. We discuss strategies for validation of the sensitivity, specificity, and reliability of HD-DOT acquired maps of cortical brain function. We then provide a brief overview of some clinical applications of HD-DOT. Though diffuse optical measurements of neurophysiology have existed for several decades, tremendous opportunity remains to advance optical imaging of brain function to address a crucial niche in basic and clinical neuroscience: that of bedside and minimally constrained high fidelity imaging of brain function