The Strathclyde Brain Computer Interface (S-BCI) : the road to clinical translation

In this paper, we summarise the state of development of the Strathclyde Brain Computer Interface (S-BCI) and what has been so far achieved. We also briefly discuss our next steps for translation to spinal cord injured patients and the challenges we envisage in this process and how we plan to address some of them. Projections of the S-BCI project for the coming few years are also presented

Developing a computer aided design tool for inclusive design

The purpose of this study was to investigate age-related changes in the performance of a range of movement tasks for integration into a computer aided design (CAD) tool for use in inclusive design

Single-trial multiwavelet coherence in application to neurophysiological time series

A method of single-trial coherence analysis is presented, through the application of continuous muldwavelets. Multiwavelets allow the construction of spectra and bivariate statistics such as coherence within single trials. Spectral estimates are made consistent through optimal time-frequency localization and smoothing. The use of multiwavelets is considered along with an alternative single-trial method prevalent in the literature, with the focus being on statistical, interpretive and computational aspects. The multiwavelet approach is shown to possess many desirable properties, including optimal conditioning, statistical descriptions and computational efficiency. The methods. are then applied to bivariate surrogate and neurophysiological data for calibration and comparative study. Neurophysiological data were recorded intracellularly from two spinal motoneurones innervating the posterior,biceps muscle during fictive locomotion in the decerebrated cat

Reversed cortical over-activity during movement imagination following neurofeedback treatment for central neuropathic pain

Objective: One of the brain signatures of the central neuropathic pain (CNP) is the theta band over-activity of wider cortical structures, during imagination of movement. The objective of the study was to investigate whether this over-activity is reversible following the neurofeedback treatment of CNP. Methods: Five paraplegic patients with pain in their legs underwent from twenty to forty neurofeedback sessions that significantly reduced their pain. In order to assess their dynamic cortical activity they were asked to imagine movements of all limbs a week before the first and a week after the last neurofeedback session. Using time–frequency analysis we compared EEG activity during imagination of movement before and after the therapy and further compared it with EEG signals of ten paraplegic patients with no pain and a control group of ten able-bodied people. Results: Neurofeedback treatment resulted in reduced CNP and a wide spread reduction of cortical activity during imagination of movement. The reduction was significant in the alpha and beta band but was largest in the theta band. As a result cortical activity became similar to the activity of other two groups with no pain. Conclusions: Reduction of CNP is accompanied by reduced cortical over-activity during movement imagination. Significance: Understanding causes and consequences mechanism through which CNP affects cortical activity

EEG signatures of arm isometric exertions in preparation, planning and execution

The electroencephalographic (EEG) activity patterns in humans during motor behaviour provide insight into normal motor control processes and for diagnostic and rehabilitation applications. While the patterns preceding brisk voluntary movements, and especially movement execution, are well described, there are few EEG studies that address the cortical activation patterns seen in isometric exertions and their planning. In this paper, we report on time and time-frequency EEG signatures in experiments in normal subjects (n=8), using multichannel EEG during motor preparation, planning and execution of directional centre-out arm isometric exertions performed at the wrist in the horizontal plane, in response to instruction-delay visual cues. Our observations suggest that isometric force exertions are accompanied by transient and sustained event-related potentials (ERP) and event-related (de-)synchronisations (ERD/ERS), comparable to those of a movement task. Furthermore, the ERPs and ERD/ERS are also observed during preparation and planning of the isometric task. Comparison of ear-lobe-referenced and surface Laplacian ERPs indicates the contribution of superficial sources in supplementary and pre-motor (FCz), parietal (CPz) and primary motor cortical areas (C1 and FC1) to ERPs (primarily negative peaks in frontal and positive peaks in parietal areas), but contribution of deep sources to sustained time-domain potentials (negativity in planning and positivity in execution). Transient and sustained ERD patterns in μ and β frequency bands of ear-lobe-referenced and surface Laplacian EEG indicate the contribution of both superficial and deep sources to ERD/ERS. As no physical displacement happens during the task, we can infer that the underlying mechanisms of motor-related ERPs and ERD/ERS patterns do not only depend on change in limb coordinate or muscle-length-dependent ascending sensory information and are primary generated by motor preparation, direction-dependent planning and execution of isometric motor tasks. The results contribute to our understanding of the functions of different brain regions during voluntary motor tasks and their activity signatures in EEG can shed light on the relationships between large-scale recordings such as EEG and other recordings such as single unit activity and fMRI in this context

Some Observations on the Pattern of Labyrinth and Neck Reflexes and Their Interactions in Both Normal and Hemilabyrinthectomized Cats

In this study the pattern of labyrinth and neck reflexes were examined in both acute hemilabyrinthectomized cats, and cats allowed to recover from the lesion. In acute animals it was found that labyrinth reflexes in extensors and flexors ipsilateral to the side of the lesion appeared normal, while labyrinth reflexes contralateral to the lesion were reversed in comparison to normal. Neck reflexes were unaltered by hemilabyrinthectomy. Consequently, labyrinth and neck reflex interactions are altered giving rise to a new pattern of interaction which may account for some of the observed postural abnormalities seen with hemilabyrinthectomy. Furthermore, the observation that the normal labyrinth reflex is dependant on the integrity of the contralateral labyrinth supports electrophysiological evidence that these reflexes are mediated predominantly by crossed pathways. In chronic cats, allowed a minimum of 8 weeks recovery, the labyrinth and neck reflexes contralateral to the original lesion regain their normal form, while labyrinth and neck reflexes on the side of the lesion, although normal in the extensor are reversed in the flexor muscles. The flexors and extensors on the side of the original lesion display parallel activity changes during labyrinth and neck reflexes. It therefore appears that in the compensated animal there has been a re-organisation of labyrinth and neck reflexes. The normal pattern has been restored to the limb contralateral to the lesion (which in the acute showed reversed reflexes), but in the limb ipsilateral to the lesion labyrinth and neck reflex expression in flexor muscles has been reversed giving coactivation of flexors and extensors. Despite this the complete pattern of labyrinth and neck reflexes in the compensated animal can still be considered appropriate for providing effective postural stabilisation by regulating the overal stiffness of one limb, and by altering the distribution of tone in the other, as in the normal reciprocal fashion. In addition to the above studies experiments were performed on both normal and acute decerebrated cats which examined the interaction of labyrinth and neck reflex systems with elbow joint afferents. In these experiments head, neck and elbow position was used to condition both crossed extensor and ipsilateral flexion reflexes. The results indicate that head and neck position modulate reflex excitability in flexors and extensors in a manner consistant with observations on the direction of labyrinth and neck reflexes in these muscles, and that elbow position can effectively modulate these actions independently of changes in muscle length. Extensor reflex excitability was greatest in normal cats when the elbow was flexed and the head tilted side-down or the neck tilted side-up. Flexor excitability was greatest with the limb held in extension and the head tilted side-up or the neck side-down. In acute animals the labyrinth actions were altered in agreement with the description of labyrinth reflexes in these animals. The ability of joint afferents to modulate descending labyrinth and neck inputs to motoneurones is taken to indicate that limb position can effectively regulate the reflex output of the labyrinth and neck systems so as to generate reflexes that are appropriate for the position of the limb at any particular time. (Abstract shortened by ProQuest.)

Impaired transmission in the corticospinal tract and gait disability in spinal cord injured persons

Rehabilitation following spinal cord injury is likely to depend on recovery of corticospinal systems. Here we investigate whether transmission in the corticospinal tract may explain foot drop (inability to dorsiflex ankle) in persons with spinal cord lesion. The study was performed in 24 persons with incomplete spinal cord lesion (C1 to L1) and 15 healthy controls. Coherence in the 10- to 20-Hz frequency band between paired tibialis anterior muscle (TA) electromyographic recordings obtained in the swing phase of walking, which was taken as a measure of motor unit synchronization. It was significantly correlated with the degree of foot drop, as measured by toe elevation and ankle angle excursion in the first part of swing. Transcranial magnetic stimulation was used to elicit motor-evoked potentials (MEPs) in the TA. The amplitude of the MEPs at rest and their latency during contraction were correlated to the degree of foot drop. Spinal cord injured participants who exhibited a large foot drop had little or no MEP at rest in the TA muscle and had little or no coherence in the same muscle during walking. Gait speed was correlated to foot drop, and was the lowest in participants with no MEP at rest. The data confirm that transmission in the corticospinal tract is of importance for lifting the foot during the swing phase of human gait

Classical and controlled auditory mismatch responses to multiple physical deviances in anaesthetised and conscious mice

Human mismatch negativity (MMN) is modelled in rodents and other non-human species to examine its underlying neurological mechanisms, primarily described in terms of deviance-detection and adaptation. Using the mouse model, we aim to elucidate subtle dependencies between the mismatch response (MMR) and different physical properties of sound. Epidural field potentials were recorded from urethane anaesthetised and conscious mice during oddball and many-standards control paradigms with stimuli varying in duration, frequency, intensity, and inter-stimulus interval. Resulting auditory evoked potentials, classical MMR (oddball – standard), and controlled MMR (oddball – control) waveforms were analysed. Stimulus duration correlated with stimulus-off response peak latency, whereas frequency, intensity, and inter-stimulus interval correlated with stimulus-on N1 and P1 (conscious only) peak amplitudes. These relationships were instrumental in shaping classical MMR morphology in both anaesthetised and conscious animals, suggesting these waveforms reflect modification of normal auditory processing by different physical properties of sound. Controlled MMR waveforms appeared to exhibit habituation to auditory stimulation over time, which was equally observed in response to oddball and standard stimuli. These findings are inconsistent with the mechanisms thought to underlie human MMN, which currently do not address differences due to specific physical features of sound. Thus, no evidence was found to objectively support the deviance-detection or adaptation hypotheses of MMN in relation to anaesthetised or conscious mice. These findings highlight the potential risk of mischaracterising difference waveform components that are principally influenced by physical sensitivities and habituation of the auditory system

The mechanism of neurofeedback training for treatment of central neuropathic pain in paraplegia : a pilot study

Central neuropathic pain has a prevalence of 40% in patients with spinal cord injury. Electroencephalography (EEG) studies showed that this type of pain has identifiable signatures, that could potentially be targeted by a neuromodulation therapy. The aim of the study was to investigate the putative mechanism of neurofeedback training on central neuropathic pain and its underlying brain signatures in patients with chronic paraplegia. Patients’ EEG activity was modulated from the sensory-motor cortex, electrode location C3/Cz/C4/P4 in up to 40 training sessions Results. Six out of seven patients reported immediate reduction of pain during neurofeedback training. Best results were achieved with suppressing Ɵ and higher β (20–30 Hz) power and reinforcing α power at C4. Four patients reported clinically significant long-term reduction of pain (>30 %) which lasted at least a month beyond the therapy. EEG during neurofeedback revealed a wide spread modulation of power in all three frequency bands accompanied with changes in the coherence most notable in the beta band. The standardized low resolution electromagnetic tomography analysis of EEG before and after neurofeedback therapy showed the statistically significant reduction of power in beta frequency band in all tested patients. Areas with reduced power included the Dorsolateral Prefrontal Cortex, the Anterior Cingulate Cortex and the Insular Cortex. Neurofeedback training produces both immediate and longer term reduction of central neuropathic pain that is accompanied with a measurable short and long term modulation of cortical activity. Controlled trials are required to confirm the efficacy of this neurofeedback protocol on treatment of pain. The study is a registered UKCRN clinical trial Nr 9824

Alignments of Voids in the Cosmic Web

We investigate the shapes and mutual alignment of voids in the large scale matter distribution of a LCDM cosmology simulation. The voids are identified using the novel WVF void finder technique. The identified voids are quite nonspherical and slightly prolate, with axis ratios in the order of c:b:a approx. 0.5:0.7:1. Their orientations are strongly correlated with significant alignments spanning scales >30 Mpc/h. We also find an intimate link between the cosmic tidal field and the void orientations. Over a very wide range of scales we find a coherent and strong alignment of the voids with the tidal field computed from the smoothed density distribution. This orientation-tide alignment remains significant on scales exceeding twice the typical void size, which shows that the long range external field is responsible for the alignment of the voids. This confirms the view that the large scale tidal force field is the main agent for the large scale spatial organization of the Cosmic Web.Comment: 10 pages, 4 figures, submitted to MNRAS, for high resolution version, see http://www.astro.rug.nl/~weygaert/tim1publication/voidshape.pd