Speaker: Matthew Mitchell, 4th Year PhD Student at the Academic Unit of Neurology, School of Medicine, TCD

Abstract:

Addressing the pathophysiological role of altered sensorimotor integration in the neurodegenerative phenomena of movement disorders may help guide the development of more detailed disease prognosis. Sensorimotor integration may be examined non-invasively by recording neural activity with electroencephalography (EEG) while employing vibration-mediated proprioceptive stimulation (VPS) which attempts to modulate the cortical integration of proprioceptive information. In VPS, an oscillating probe (vibration) makes repeated small (<3mm) collisions with a tendon over the surface of the skin, evoking muscle spindle action potentials. The normal firing frequency of muscle spindle afferents in the flexor carpi radialis muscle can be elicited when the collision force, frequency, and amplitude of vibration is controlled giving rise to a stable percept that the whole hand is extending or supinating while it remains stationary. This percept is often referred to as the Kinaesthetic Illusion. Matthew will present his progress to date using this technique in his PhD and discuss some of the ongoing work to identify the spectral characteristics that occur during the course of VPS. 

Speaker: Dr Giovanni Di Liberto, Assistant Professor in Intelligent Systems, School of Computer Science and Statistics, Trinity College Dublin

Other affiliations: ADAPT Centre, Trinity College Institute of Neuroscience

Abstract:

Perception involves making sense of the world around us by processing a continuous flow of sensory information. In doing so, the human brain produces electrical activity that synchronises to particular properties of sensory inputs, a phenomenon referred to as neural tracking. The case of auditory perception is particularly remarkable. The discovery that neural signals reliably track the amplitude envelope of continuous sounds has led to new research directions, such as the study of auditory attention in immersive multi-talker scenarios. Here, I will present a series of studies investigating the neural tracking phenomenon when listening to speech and music, whereby both low-level acoustic properties and more abstract linguistic structures have to be processed. I will demonstrate methodologies for disentangling neural responses to stimulus properties at different levels of abstraction from a single electroencephalography recording. I will then describe recent developments where the resulting objective neural indices are used for probing auditory perception across various contexts, such as language learning and developmental research. 

Speaker: Vitoria Fahed, PhD Candidate in Biomedical Engineering at UCD

Other affiliations: Honorary Research Fellow at University of Cardiff

Abstract:

Huntington’s disease (HD) is a progressive neurodegenerative disease with a triad of motor, cognitive and psychiatric symptoms. It can be accurately diagnosed with a genetic test but there is no cure or treatment that stops the course of the disease. While the characteristics of motor symptoms of HD are well-documented in clinical evaluations, the associated underlying muscle and motor unit activity remain poorly understood. The aim of this study was to examine sEMG features in individuals with HD during wrist flexion-extension and forearm pronation-supination and a fine motor control task. Data were compared with sEMG data recorded from age- and sex-matched control participants in order to identify characteristics and changes in sEMG activity in HD. The results demonstrate the presence of reduced grip force, with evidence of reduced coordination, abnormalities in motor control and altered muscle activation in manifest HD.

Speaker: Kieran Mohr, postdoctoral researcher in Cognitive Neuroscience at UCD

Abstract:

Although spatial attention routinely boosts the amplitude of visual evoked potential (VEP) components such as the P1 and N1, its influence earlier in the visual processing pipeline, at the level of the C1 component, remains controversial. One possible reason for this is that C1 topography and magnitude varies across the visual field in a subject-specific manner, leading to low signal-to-noise ratios (SNR) in many studies. However, by using orthogonal m-sequence pulse streams to generate multifocal VEPs, the full visual field can be probed rapidly in parallel, allowing stimulus locations with high SNR to be chosen for each participant in advance of an experiment. Using this approach over a series of experiments, this study investigated two potential cognitive factors that may underpin the discrepant attention effects – feature similarity between target stimuli and stimuli used to probe the attention effects, and the nature of performance feedback. The results revealed a complex pattern in which attention boosted the C1, when taking all experiments together, but suppressed it under some circumstances. This pattern of results gave mixed support to the feature-similarity hypothesis but did not support the performance feedback hypothesis. However, the sequence of feedback regimes that participants encountered prompted them to adopt divergent, persistent attentional strategies with respect to the C1. Finally, the possible contributing factor of multiple cortical C1 generators producing overlapping signals on the scalp was suggested by the elimination of the C1 suppression effect when a current source density (CSD) transform was applied to attenuate signal overlap.

Speaker: Jérémy Liegey, PhD Student in Biomedical Engineering at UCD

Abstract:

Deep Brain Stimulation (DBS) and dopaminergic medication are well-established therapies for reducing the symptoms of Parkinson’s disease. The manner in which they influence muscle activation and motor unit firing patterns, however, are not well understood. The aim of this study is to use high density surface electromyography (HDsEMG) to directly examine the effects of DBS on motor unit recruitment and firing rate modulation. HDsEMG was recorded from the first dorsal interosseous in 12 participants with bilateral DBS during submaximal index finger abduction in 4 different conditions (On and Off medication and DBS stimulation On and Off). The HDsEMG signals were decomposed and motor unit firing properties compared across conditions.  Turning on DBS stimulation led to an increase in maximum voluntary force, reduced force variability and increased motoneuron firing rate during submaximal contractions. These results indicate that DBS influences the neural drive to muscle and motoneuron firing properties, altering firing rate and patterns.