Analysis of Multi-Directional Recycled Jute Fiber Composite Behavior Using Experimental, Numerical, and Analytical Methods

Composite materials are increasing in popularity as a material of choice in many engineering applications. Major industries using composites include automotive, construction, and sports equipment. Most of the knowledge, research, and technology that will help decrease the cost of composite materials have been aimed at developing synthetic fibers as the reinforcing constituent. This thesis characterizes jute fibers obtained as a byproduct from the coffee industry to determine if they can be viable in composite manufacturing. Experimental analysis, finite element analysis, and analytical modeling are used to characterize jute fiber based composites. Experimental analysis consists of jute fiber bundle tensile testing as well as tensile testing of multiple laminates. Finite element and analytical models were developed to simulate different composite characteristics and their influence on jute composites. Finite element models investigated the influences of fiber undulation, fiber damage, and matrix porosity. Results show that certain manufacturing precautions should be taken to minimize imperfections which have negative influences on the composite. Fiber damage has the largest influence when introduced near the top of the fiber wave and can cause normal stresses to increase 56%. Fiber undulation and matrix porosity also have noticeable influences on the composite

Enhancing studies of the connectome in autism using the autism brain imaging data exchange II

The second iteration of the Autism Brain Imaging Data Exchange (ABIDE II) aims to enhance the scope of brain connectomics research in Autism Spectrum Disorder (ASD). Consistent with the initial ABIDE effort (ABIDE I), that released 1112 datasets in 2012, this new multisite open-data resource is an aggregate of resting state functional magnetic resonance imaging (MRI) and corresponding structural MRI and phenotypic datasets. ABIDE II includes datasets from an additional 487 individuals with ASD and 557 controls previously collected across 16 international institutions. The combination of ABIDE I and ABIDE II provides investigators with 2156 unique cross-sectional datasets allowing selection of samples for discovery and/or replication. This sample size can also facilitate the identification of neurobiological subgroups, as well as preliminary examinations of sex differences in ASD. Additionally, ABIDE II includes a range of psychiatric variables to inform our understanding of the neural correlates of co-occurring psychopathology; 284 diffusion imaging datasets are also included. It is anticipated that these enhancements will contribute to unraveling key sources of ASD heterogeneity

Characteristics of the human mirror system Measurements of primary motor cortex activity using transcranial magnetic stimulation

During the past decade, neuroscience has increasingly focused on the rol e of the so-called mirror system in a variety of functions such as act ion recognition, action understanding, and imitation. Mirror neurons wer e initially discovered in the ventral premotor cortex of the macaque bra in and have the striking property to discharge not only when the monkey performs an action, but also when it merely observes a similar action pe rformed by another individual. To study the human mirror system at work during action perception, transcranial magnetic stimulation (TMS) has pr oven to be an excellent technique, as it can be used to obtain fast and focal measurements of cortical activity within the primary motor area (M 1) of subjects observing actions performed by others. In the present doc toral project, the TMS technique is extensively used to investigate whet her and how the mirror system is responsive to action observation. To do so, different parameters of perceived actions are manipulated to assess their relative importance in mediating resonant activity in the obser ver s motor system. When a voluntary action is generated, the brain must encode the directio n of the movement in space, specified in an external coordinate frame, a nd translate this directional information into a set of muscle activatio n patterns, specified in an intrinsic coordinate frame. From single cell recordings in monkeys, it was shown that M1 contains both direction-rel ated and muscle-related neurons to a nearly equal extent. However, it re mains largely unclear which of the two reference frames is used during t he process of observation-to-execution mapping. To address this question , our first study adopted a paradigm from which it was possible to disen tangle whether the observer s primary motor cortex is facilitated in acc ordance to either the observed movement direction or the observed muscle activation. Overall, data indicated that the mirror system, at least at the level of M1, reflects the muscular requirements of observed actions , rather than the directional features. Based on the findings of our first study (i.e., muscle specific activity modulations at the level of M1 during movement observation) and the not ion that observation-induced reactivation of motor areas may have a posi tive impact on recovery of motor functions after stroke, the second stud y aimed to identify the most effective observation settings that mediate muscle specific facilitation of the motor system during action observat ion. More specifically, we explored the effects of varying body configur ations between the observer and observed model on observation-induced ac tivity in M1. Overall, it was shown that activity within the mirror syst em may depend substantially upon the laterality of the observed hand (i. e., left or right) and the perspective from which the action is observed (i.e., first or third person perspective). More specifically, facilitat ion of the observer s M1 was shown to be particularly high when right ha nd actions were observed from a first person perspective, whereas, for l eft hand actions, the third person perspective was more efficient. On th e other hand, the degree of postural congruency between body parts of th e observer and observed model only mildly influenced the extent of M1 fa cilitation. Overall, the results of these first two studies indicated that M1 activi ty is strongly driven by a muscle-specific mapping between the observed movement and the observer s motor system. This raised the question wheth er the mirror system and, particularly M1, encodes also other parameters related to the muscular requirements of the observed movement, such as the produced force. This hypothesis was tested in the third and fourth s tudy of the project. Overall, data indicated that observation-induced ac tivity in M1 reflects the level of observed grip force when subjects obs erve the lifting of different object weights. Moreover, the encoding of grip force requirements in M1 appeared to be mediated by distinct visual cues of the observed lifting actions, such as the associated kinematica l profile as well as the muscle tension/pressure produced in the acting hand. Surprisingly, object-related information on object weight (and con sequently on exerted grip force) appeared to have only minor influences on the encoding of force within M1. Finally, the focus shifted slightly in the last study in which we invest igated how different types of sensory input drive the human mirror syste m. Although it has been shown that the mirror system responds to either action-specific vision or sound, it remains a topic of debate whether mi rror activity reflects multisensory convergence of vision and sound during action perception. To address this question, M1 activity w as measured while subjects perceived unimodal visual (V), unimodal audit ory (A), or multimodal (V + A) stimuli of a simple hand action. In short , data indicated that perception-induced activity in M1 increases substa ntially from the simultaneous presentation of visual and auditory input about a perceived action. As such, these data speak in favour of multimo dal audio-visual action representations in the human motor system. In summary, the present doctoral project provides novel insights on the process of observation-to-execution mapping within motor areas by measur ing observation-induced activity modulations at the level of the primary motor cortex. More specifically, our data support the hypothesis that M 1 may contribute to action observation, by representing the muscle-relat ed features of observed actions. The application of movement observation in motor rehabilitation is theor etically based on the finding that cortical motor circuits are activated in a similar way during movement observation as during execution. Incre asing our insights into the visual features that actually mediate activi ty modulations in the motor system during movement perception may theref ore help to identify the most effective conditions for stimulating the m otor system during action observation.status: publishe

Eye contact enhances interpersonal motor resonance: comparing video stimuli to a live two-person action context

Previous research has shown a link between eye contact and interpersonal motor resonance, indicating that the mirroring of observed movements is enhanced when accompanied with mutual eye contact between actor and observer. Here, we further explored the role of eye contact within a naturalistic two-person action context. Twenty-two participants observed simple hand movements combined with direct or averted gaze presented via a live model in a two-person setting or via video recordings, while transcranial magnetic stimulation was applied over the primary motor cortex (M1) to measure changes in M1 excitability. Skin conductance responses and gaze behavior were also measured to investigate the role of arousal and visual attention herein. Eye contact significantly enhanced excitability of the observer's M1 during movement observation within a two-person setting. Notably, participants with higher social responsiveness (Social Communication subscale of the Social Responsiveness Scale) displayed a more pronounced modulation of M1 excitability by eye gaze. Gaze-related modulations in M1 excitability were, however, not associated with differences in visual attention or autonomic arousal. In summary, the current study highlights the effectiveness and feasibility of adopting paradigms with high ecological validity for studying the modulation of mirror system processes by subtle social cues, such as eye gaze.status: publishe

Oxytocin-based pharmacotherapy for Autism Spectrum Disorders: Investigating the neural and behavioural effects of a promising intervention approach

Oral presentation during the Fourth Symposium of the Marguerite-Marie Delacroix Foundation : Multidisciplinary Research Grants.status: publishe

Granularity of the mirror neuron system: A complex endeavor Comment on "Grasping synergies: A motor-control approach to the mirror neuron mechanism" by A. D'Ausilio et al.

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Enhanced mirroring upon mutual gaze: Multimodal evidence from TMS-assessed corticospinal excitability and the EEG mu rhythm

Abstract Eye-to-eye contact is a salient cue for regulating everyday social interaction and communication. Previous research has demonstrated that direct eye contact between actor and observer specifically enhances the ‘mirroring’ of others’ actions in the observer, as measured by transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs; an index of motor cortex excitability during action observation). However, it remains unknown whether other markers of mirror system activation, such as suppression of the EEG mu rhythm (i.e. attenuation of neural oscillations in the 8-13 Hz frequency band over the sensorimotor strip), are also susceptible to perceived eye contact. In the current study, a multimodal approach was adopted to assess both TMS-induced MEPs and EEG mu suppression (in separate sessions), while 32 participants (20 men; mean age: 24;8 years) observed a simple hand movement in combination with direct or averted gaze from the live stimulus person. Both indices of mirror system functioning were significantly modulated by perceived eye gaze; showing a significant increase in MEP amplitude and a significant attenuation of the mu rhythm when movement observation was accompanied with direct compared to averted gaze. Importantly, while inter-individual differences in absolute MEP and mu suppression scores were not significantly related, a significant association was identified between gaze-related changes in MEP responses and mu suppression. As such, it appears that while the neurophysiological substrates underlying mu suppression and TMS-induced MEP responses differ, both are similarly affected by the modulatory impact of gaze-related cues. In sum, our results suggest that both EEG mu rhythm and TMS-induced MEPs are sensitive to the social relevance of the observed actions, and that a similar neural substrate may drive gaze-related changes in these distinct markers of mirror system functioning.status: Published onlin

Tracking transient changes in the neural frequency architecture: harmonic relationships between theta and alpha peaks facilitate cognitive performance

The synchronisation between neural oscillations at different frequencies has been proposed as a core mechanism for the coordination and integration of neural systems at different spatio-temporal scales. Since neural oscillations of different frequencies can only fully synchronize when their ‘peak’ frequencies form harmonic relationships (e.g. f2 = f1/2), the present study explored whether the transient occurrence of harmonic cross-frequency relationship between task-relevant rhythms underlies efficient cognitive processing. Continuous EEG recordings (51 human participants; 14 males) were obtained during an arithmetic task, rest and breath focus. In two separate experiments, we consistently show that the proportion of epochs displaying a 2:1 harmonic relationship between alpha (8—14 Hz) and theta (4—8 Hz) peak frequencies (i.e. alphapeak≈ 10.6 Hz; thetapeak ≈ 5.3 Hz), was significantly higher when cognitive demands increased. In addition, a higher incidence of 2:1 harmonic cross-frequency relationships was significantly associated with increased alpha:theta phase synchrony and improved arithmetic task performance, thereby underlining the functional relevance of this cross-frequency configuration. Notably, opposite dynamics were identified for a specific range of ‘non-harmonic’ alpha:theta cross-frequency relationships (i.e. alphapeak/thetapeak = 1.1-1.6) which showed a higher incidence during rest compared to the arithmetic task. The observation that alpha and theta rhythms shifted into ‘harmonic’ versus ‘non-harmonic’ cross-frequency relationships depending on (cognitive) task demands is in line with the notion that the neural frequency architecture entails optimal frequency arrangements to facilitate cross-frequency ‘coupling’ and ‘decoupling’.status: Published onlin

Influence of oxytocin on emotion recognition: A randomized placebo-controlled trial

The neuropeptide ‘oxytocin’ (OT) is known to play a pivotal role in a variety of complex social behaviors. It is hypothesized that OT promotes prosocial behavior by enhancing the processing of socially-relevant information from the environment, such as facial expressions and bodily kinematics. As these behaviors are known to be deficient in people with an Autism Spectrum Disorder (ASD), more research is needed to assess OT as a potential therapeutic approach. With the present study, we explored the extent by which OT can enhance the ‘reading’ of emotional body language as presented in impoverished biological motion point light displays (PLDs). To this end, we adopted a double-blind, randomized placebo-controlled design to assess single-dose effects of intranasal OT administration. Eighty-six neurotypical male participants performed a bodily emotion recognition task before and after a single-dose of intranasal OT. Two experiments were conducted to assess whether the novelty of the presented emotional states contributes to recognition performance, one with identical and the other with novel PLD stimuli pre- and post-OT administration. Single-dose effects of OT administration on emotion recognition were moderate, indicating enhanced recognition of emotional body language when novel emotional stimuli were presented post-OT administration. Yet when identical emotional stimuli were presented at baseline and post-OT administration, results indicated a general learning effect rather than specific enhancements related to the OT administration. Although the effects were moderate, they provide indications that OT might form a promising target for development of novel treatments for patient populations with particular social deficits such as ASD.status: publishe

Editorial: How Do Motivational States Influence Motor Resonance?

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