ORCID Profile
0000-0002-5281-8221
Current Organisation
Monash University
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Sensory Systems | Artificial Intelligence and Image Processing not elsewhere classified | Central Nervous System | Neurosciences not elsewhere classified | Biomedical Engineering not elsewhere classified | Biomedical Engineering | Neurosciences
Expanding Knowledge in the Information and Computing Sciences | Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in Psychology and Cognitive Sciences |
Publisher: Cold Spring Harbor Laboratory
Date: 16-10-2018
DOI: 10.1101/437970
Abstract: Coherent neuronal dynamics play an important role in complex cognitive functions. Optogenetic stimulation promises to provide new ways to test the functional significance of coherent neural activity. However, the mechanisms by which optogenetic stimulation drives coherent dynamics remain unclear, especially in the non-human primate brain. Here, we perform computational modeling and experiments to study the mechanisms of optogenetic-stimulation-driven coherent neuronal dynamics in non-human primates. Neural responses arise from stimulation-evoked temporal windows of excitatory and inhibitory activity. The temporal properties of the E-I windows generate coherent neuronal dynamics at varied frequencies and depend on optogenetic stimulation parameters. Experimental results agree with parameter dependent predictions from the computational models. These results demonstrate that responses to optogenetic stimulation are governed by local circuit properties that alter the timing of E-I activity. Transient imbalances in excitatory and inhibitory activity may provide a general mechanism for generating coherent neuronal dynamics.
Publisher: Elsevier BV
Date: 07-2021
Publisher: IOP Publishing
Date: 06-2022
Abstract: Objective. Intracortical visual prostheses are being developed to restore sight in people who are blind. The resolution of artificial vision is dictated by the location, proximity and number of electrodes implanted in the brain. However, increasing electrode count and proximity is traded off against tissue damage. Hence, new stimulation methods are needed that can improve the resolution of artificial vision without increasing the number of electrodes. We investigated whether a technique known as current steering can improve the resolution of artificial vision provided by intracortical prostheses without increasing the number of physical electrodes in the brain. Approach. We explored how the locus of neuronal activation could be steered when low litude microstimulation was applied simultaneously to two intracortical electrodes. A 64-channel, four-shank electrode array was implanted into the visual cortex of rats ( n = 7). The distribution of charge ranged from single-electrode stimulation (100%:0%) to an equal distribution between the two electrodes (50%:50%), thereby steering the current between the physical electrodes. The stimulating electrode separation varied between 300 and 500 μ m. The peak of the evoked activity was defined as the ‘virtual electrode’ location. Main results. Current steering systematically shifted the virtual electrode on average between the stimulating electrodes as the distribution of charge was moved from one stimulating electrode to another. This effect was unclear in single trials due to the limited s ling of neurons. A model that scales the cortical response to each physical electrode when stimulated in isolation predicts the evoked virtual electrode response. Virtual electrodes were found to elicit a neural response as effectively and predictably as physical electrodes within cortical tissue on average. Significance. Current steering could be used to increase the resolution of intracortical electrode arrays without altering the number of physical electrodes which will reduce neural tissue damage, power consumption and potential heat dispersion issues.
Publisher: IEEE
Date: 08-2012
Publisher: IOP Publishing
Date: 20-05-2009
DOI: 10.1088/1741-2560/6/3/035006
Abstract: Restoring vision to the blind by way of medical device technology has been an objective of several research teams for a number of years. It is known that spots of light-phosphenes-can be elicited by way of electrical stimulation of surviving retinal neurons. Beyond this our understanding of prosthetic vision remains rudimentary. We have designed and manufactured an integrated circuit neurostimulator with substantial versatility, able to provide focussed, simultaneous stimulation using current sources and sinks, steering the current to the intended site of stimulation. The ASIC utilizes high-voltage CMOS transistors in key circuits, to manage voltage compliance issues (due to an unknown or changing electrode/tissue interface impedance) given the relatively high stimulation thresholds necessary to elicit physiological excitation of retinal neurons. In addition, a unique multiplexing system comprised of electrodes arranged in a hexagonal mosaic is used, wherein each electrode can be addressed to be a stimulating electrode and all adjacent electrodes serve as the return path. This allows for simultaneous stimulation to be delivered while appropriately managing cross-talk between the stimulating electrodes. Test results indicate highly linear current sources and sinks (differential nonlinearity error of 0.13 least significant bits -2.6 microA), with the ASIC clearly able to provide focussed stimulation using electrodes immersed in a saline solution.
Publisher: IEEE
Date: 2005
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-07-2017
Abstract: Simultaneous stimulation of multiple retinal electrodes in normally sighted animals shows promise in improving the resolution of retinal prostheses. However, the effects of simultaneous stimulation on degenerate retinae remain unknown. Therefore, we investigated the characteristics of cortical responses to multielectrode stimulation of the degenerate retina. Four adult cats were bilaterally implanted with retinal electrode arrays in the suprachoroidal space after unilateral adenosine triphosphate (ATP)-induced retinal photoreceptor degeneration. Functional and structural changes were characterized by using electroretinogram a-wave litude and optical coherence tomography. Multiunit activity was recorded from both hemispheres of the visual cortex. Responses to single- and multielectrode stimulation of the ATP-injected and fellow control eyes were characterized and compared. The retinae of ATP-injected eyes displayed structural and functional changes consistent with mid- to late-stage photoreceptor degeneration and remodeling. Responses to multielectrode stimulation of the ATP-injected eyes exhibited shortened latencies, lower saturated spike counts, and higher thresholds, compared to stimulation of the fellow control eyes. Electrical receptive field sizes were significantly larger in the ATP-injected eye than in the control eye, and positively correlated with the extent of degeneration. Significant differences exist between cortical responses to stimulation of healthy and degenerate retinae. Our results highlight the importance of using a retinal degeneration model when evaluating the efficacy of novel stimulation paradigms.
Publisher: IOP Publishing
Date: 08-2023
Abstract: Objective. We developed a realistic simulation paradigm for cortical prosthetic vision and investigated whether we can improve visual performance using a novel clustering algorithm. Approach. Cortical visual prostheses have been developed to restore sight by stimulating the visual cortex. To investigate the visual experience, previous studies have used uniform phosphene maps, which may not accurately capture generated phosphene map distributions of implant recipients. The current simulation paradigm was based on the Human Connectome Project retinotopy dataset and the placement of implants on the cortices from magnetic resonance imaging scans. Five unique retinotopic maps were derived using this method. To improve performance on these retinotopic maps, we enabled head scanning and a density-based clustering algorithm was then used to relocate centroids of visual stimuli. The impact of these improvements on visual detection performance was tested. Using spatially evenly distributed maps as a control, we recruited ten subjects and evaluated their performance across five sessions on the Berkeley Rudimentary Visual Acuity test and the object recognition task. Main results. Performance on control maps is significantly better than on retinotopic maps in both tasks. Both head scanning and the clustering algorithm showed the potential of improving visual ability across multiple sessions in the object recognition task. Significance. The current paradigm is the first that simulates the experience of cortical prosthetic vision based on brain scans and implant placement, which captures the spatial distribution of phosphenes more realistically. Utilisation of evenly distributed maps may overestimate the performance that visual prosthetics can restore. This simulation paradigm could be used in clinical practice when making plans for where best to implant cortical visual prostheses.
Publisher: IEEE
Date: 05-2008
Publisher: AMPCo
Date: 05-2017
DOI: 10.5694/MJA16.01011
Abstract: The brain-computer interface (BCI) is an exciting advance in neuroscience and engineering. In a motor BCI, electrical recordings from the motor cortex of paralysed humans are decoded by a computer and used to drive robotic arms or to restore movement in a paralysed hand by stimulating the muscles in the forearm. Simultaneously integrating a BCI with the sensory cortex will further enhance dexterity and fine control. BCIs are also being developed to: provide ambulation for paraplegic patients through controlling robotic exoskeletons restore vision in people with acquired blindness detect and control epileptic seizures and improve control of movement disorders and memory enhancement. High-fidelity connectivity with small groups of neurons requires microelectrode placement in the cerebral cortex. Electrodes placed on the cortical surface are less invasive but produce inferior fidelity. Scalp surface recording using electroencephalography is much less precise. BCI technology is still in an early phase of development and awaits further technical improvements and larger multicentre clinical trials before wider clinical application and impact on the care of people with disabilities. There are also many ethical challenges to explore as this technology evolves.
Publisher: IEEE
Date: 08-2006
Publisher: IEEE
Date: 08-2006
Publisher: Springer Science and Business Media LLC
Date: 22-10-2018
DOI: 10.1038/S41598-018-33839-4
Abstract: Invasive Brain-Computer Interfaces (BCIs) require surgeries with high health-risks. The risk-to-benefit ratio of the procedure could potentially be improved by pre-surgically identifying the ideal locations for mental strategy classification. We recorded high-spatiotemporal resolution blood-oxygenation-level-dependent (BOLD) signals using functional MRI at 7 Tesla in eleven healthy participants during two motor imagery tasks. BCI diagnostic task isolated the intent to imagine movements, while BCI simulation task simulated the neural states that may be yielded in a real-life BCI-operation scenario. Imagination of movements were classified from the BOLD signals in sub-regions of activation within a single or multiple dorsal motor network regions. Then, the participant’s decoding performance during the BCI simulation task was predicted from the BCI diagnostic task. The results revealed that drawing information from multiple regions compared to a single region increased the classification accuracy of imagined movements. Importantly, systematic unimodal and multimodal classification revealed the ideal combination of regions that yielded the best classification accuracy at the in idual-level. Lastly, a given participant’s decoding performance achieved during the BCI simulation task could be predicted from the BCI diagnostic task. These results show the feasibility of 7T-fMRI with unimodal and multimodal classification being utilized for identifying ideal sites for mental strategy classification.
Publisher: IOP Publishing
Date: 10-09-2019
Abstract: Behavior is encoded across multiple scales of brain activity, from binary neuronal spikes to continuous fields including local field potentials (LFP). Multiscale models need to describe both the encoding of behavior and the conditional dependencies in simultaneously recorded spike and field signals, which form a high-dimensional multiscale network. However, learning spike-field dependencies in high-dimensional recordings is challenging due to the prohibitively large number of spike-field signal pairs, which makes standard learning techniques subject to overfitting. We present a sparse model-based estimation algorithm to learn these multiscale network dependencies. We develop a multiscale encoding model consisting of a point process model of binary spikes for each neuron whose firing rate is a function of the LFP network features and behavioral states. Doing so, spike-field dependencies constitute the model parameters to be learned. We resolve the parameter learning challenge by forming a constrained optimization problem to maximize the likelihood with an L1 penalty term that eases the detection of significant spike-LFP dependencies. We then apply the Akaike information criterion (AIC) to force a sparse number of nonzero dependency parameters in the model. We validate the algorithm using simulations and spike-field data from two non-human primates (NHP) in a 3D motor task with motor cortical recordings and a pro-saccade visual task with prefrontal recordings. We find that by identifying a model with a sparse set of dependency parameters, the algorithm improves spike prediction compared with models without dependencies. Further, the algorithm identifies significantly fewer dependency parameters compared with standard methods while improving their spike prediction likely due to detecting fewer spurious dependencies. Also, spike prediction on any electrode improves by including LFP features from all electrodes compared with using only those on the same electrode. Finally, unlike standard methods, the algorithm uncovers patterns of spike-field network dependencies as a function of distance, brain region, and frequency band. This algorithm can help study functional dependencies in high-dimensional spike-field networks and leads to more accurate multiscale encoding models.
Publisher: Springer Science and Business Media LLC
Date: 03-12-2018
DOI: 10.1038/S41551-018-0321-Z
Abstract: Direct electrical stimulation of the brain can alleviate symptoms associated with Parkinson's disease, depression, epilepsy and other neurological disorders. However, access to the brain requires invasive procedures, such as the removal of a portion of the skull or the drilling of a burr hole. Also, electrode implantation into tissue can cause inflammatory tissue responses and brain trauma, and lead to device failure. Here, we report the development and application of a chronically implanted platinum electrode array mounted on a nitinol endovascular stent for the localized stimulation of cortical tissue from within a blood vessel. Following percutaneous angiographic implantation of the device in sheep, we observed stimulation-induced responses of the facial muscles and limbs of the animals, similar to those evoked by electrodes implanted via invasive surgery. Proximity of the electrode to the motor cortex, yet not its orientation, was integral to achieving reliable responses from discrete neuronal populations. The minimally invasive endovascular surgical approach offered by the stent-mounted electrode array might enable safe and efficacious stimulation of focal regions in the brain.
Publisher: IOP Publishing
Date: 30-03-2016
DOI: 10.1088/1741-2560/13/3/036003
Abstract: Different frequency bands of the local field potential (LFP) have been shown to reflect neuronal activity occurring at varying cortical scales. As such, recordings of the LFP may offer a novel way to test the efficacy of neural prostheses and allow improvement of stimulation strategies via neural feedback. Here we use LFP measurements from visual cortex to characterize neural responses to electrical stimulation of the retina. We aim to show that the LFP is a viable signal that contains sufficient information to optimize the performance of sensory neural prostheses. Clinically relevant electrode arrays were implanted in the suprachoroidal space of one eye in four felines. LFPs were simultaneously recorded in response to stimulation of in idual electrodes using penetrating microelectrode arrays from the visual cortex. The frequency response of each electrode was extracted using multi-taper spectral analysis and the uniqueness of the responses was determined via a linear decoder. We found that cortical LFPs are reliably modulated by electrical stimulation of the retina and that the responses are spatially localized. We further characterized the spectral distribution of responses, with maximum information being contained in the low and high gamma bands. Finally, we found that LFP responses are unique to a large range of stimulus parameters (∼40) with a maximum conveyable information rate of 6.1 bits. These results show that the LFP can be used to validate responses to electrical stimulation of the retina and we provide the first steps towards using these responses to provide more efficacious stimulation strategies.
Publisher: IEEE
Date: 08-2007
Publisher: Springer Science and Business Media LLC
Date: 08-02-2016
DOI: 10.1038/NBT.3428
Abstract: High-fidelity intracranial electrode arrays for recording and stimulating brain activity have facilitated major advances in the treatment of neurological conditions over the past decade. Traditional arrays require direct implantation into the brain via open craniotomy, which can lead to inflammatory tissue responses, necessitating development of minimally invasive approaches that avoid brain trauma. Here we demonstrate the feasibility of chronically recording brain activity from within a vein using a passive stent-electrode recording array (stentrode). We achieved implantation into a superficial cortical vein overlying the motor cortex via catheter angiography and demonstrate neural recordings in freely moving sheep for up to 190 d. Spectral content and bandwidth of vascular electrocorticography were comparable to those of recordings from epidural surface arrays. Venous internal lumen patency was maintained for the duration of implantation. Stentrodes may have wide ranging applications as a neural interface for treatment of a range of neurological conditions.
Publisher: Wiley
Date: 15-01-2010
DOI: 10.1002/9780471740360.EBS0080
Abstract: “Artificial vision” or “prosthetic vision,” in the therapeutic sense, refers to the restoration of some degree of visual perception to the profoundly blind. In nearly all instances, such therapeutic devices are based on electrically exciting the remaining functional neural tissue within the visual pathway, which replaces the intrinsic signals that can no longer be effectively elicited because of the underlying pathology or trauma. The therapeutic device for restoring vision is generally called a “vision prosthesis.” Although a variety of approaches for a vision prosthesis design are available, a typical system usually would constitute a light sensing component (e.g., a video camera) to replace the photosensitive elements related to light transduction, an image processing unit to replace the signal processing in the visual system bypassed by the prosthesis, electronic circuitry to generate electrical stimulus waveforms to elicit perceptions of light artificially, and stimulating electrodes placed in close proximity to the target neural tissue to deliver the electric charge. Furthermore, the implanted portion of the system has to be encapsulated properly to ensure longevity and biocompatibility. At the time of writing, no commercially available product was available to provide artificial vision. However, several major research groups are working toward developing such a therapeutic device. Simple prototypes have been tested successfully in acute and chronic animal trials and more recently in small‐scale human trials. Psychophysical studies show that, despite the limited functionality of these prototypes, the recipients can successfully execute some simple visually guided tasks.
Publisher: Springer New York
Date: 2014
Publisher: IOP Publishing
Date: 18-06-2020
Publisher: Wiley
Date: 05-12-2017
Publisher: IEEE
Date: 04-2011
Publisher: Society for Neuroscience
Date: 14-12-2011
DOI: 10.1523/JNEUROSCI.4165-11.2011
Abstract: The successful development of motor neuroprosthetic devices hinges on the ability to accurately and reliably decode signals from the brain. Motor neuroprostheses are widely investigated in behaving non-human primates, but technical constraints have limited progress in optimizing performance. In particular, the organization of movement-related neuronal activity across cortical layers remains poorly understood due, in part, to the widespread use of fixed-geometry multielectrode arrays. In this study, we use chronically implanted multielectrode arrays with in idually movable electrodes to examine how the encoding of movement goals depends on cortical depth. In a series of recordings spanning several months, we varied the depth of each electrode in the prearcuate gyrus of frontal cortex in two monkeys as they performed memory-guided eye movements. We decode eye movement goals from local field potentials (LFPs) and multiunit spiking activity recorded across a range of depths up to 3 mm from the cortical surface. We show that both LFP and multiunit signals yield the highest decoding performance at superficial sites, within 0.5 mm of the cortical surface, while performance degrades substantially at sites deeper than 1 mm. We also analyze performance by varying bandpass filtering characteristics and simulating changes in microelectrode array channel count and density. The results indicate that the performance of LFP-based neuroprostheses strongly depends on recording configuration and that recording depth is a critical parameter limiting system performance.
Publisher: IEEE
Date: 08-2012
Publisher: IEEE
Date: 04-2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2007
Publisher: IEEE
Date: 07-2017
Publisher: IEEE
Date: 08-2008
Publisher: IOP Publishing
Date: 06-2023
Abstract: Objective. Blindness affects approximately 40 million people worldwide and has inspired the development of cortical visual prostheses for restoring sight. Cortical visual prostheses electrically stimulate neurons of the visual cortex to artificially evoke visual percepts. Of the 6 layers of the visual cortex, layer 4 contains neurons that are likely to evoke a visual percept. Intracortical prostheses therefore aim to target layer 4 however, this can be difficult due to cortical curvature, inter-subject cortical variability, blindness-induced anatomical changes in cortex, and electrode placement variations. We investigated the feasibility of using current steering to stimulate specific cortical layers between electrodes in the laminar column. Approach. We explored whether the multiunit neural activity peak can be manipulated between two simultaneously stimulating electrodes in different layers of the cortical column. A 64-channel, 4-shank electrode array was implanted into the visual cortex of Sprague–Dawley rats ( n = 7) orthogonal to the cortical surface. A remote return electrode was positioned over the frontal cortex in the same hemisphere. Charge was supplied to two stimulating electrodes along a single shank. Differing ratios of charge (100:0, 75:25, 50:50) and separation distances (300–500 μ m) were tested. Results. Current steering across the cortical layers did not result in a consistent shift of the neural activity peak. Both single-electrode and dual-electrode stimulation induced activity throughout the cortical column. This contrasts observations that current steering evoked a controllable peak of neural activity between electrodes implanted at similar cortical depths. However, dual-electrode stimulation across the layers did reduce the stimulation threshold at each site compared to single-electrode stimulation. Significance. Multi-electrode stimulation is not suitable for targeted activation of layers using current steering. However, it can be used to reduce activation thresholds at adjacent electrodes within a given cortical layer. This may be applied to reduce the stimulation side effects of neural prostheses, such as seizures.
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.NEUROIMAGE.2017.03.002
Abstract: Recent developments in accelerated imaging methods allow faster acquisition of high spatial resolution images. This could improve the applications of functional magnetic resonance imaging at 7 Tesla (7T-fMRI), such as neurosurgical planning and Brain Computer Interfaces (BCIs). However, increasing the spatial and temporal resolution will both lead to signal-to-noise ratio (SNR) losses due to decreased net magnetization per voxel and T
Publisher: IEEE
Date: 07-2013
Publisher: IEEE
Date: 08-2011
Publisher: IOP Publishing
Date: 19-02-2019
Abstract: Implantable neural stimulating and recording devices have the potential to restore capabilities such as vision or motor control to disabled patients, improving quality of life. Implants with a large number of stimulating electrodes typically utilize implanted batteries and/or subcutaneous wiring to deal with their high-power consumption and high data throughput needed to address all electrodes with low latency. The use of batteries places severe limitations on the implant's size, usable duty cycle, device longevity while subcutaneous wiring increases the risk of infection and mechanical damage due to device movement. To overcome these limitations, we have designed and implemented a system that supports up to 473 implanted stimulating microelectrodes, all wirelessly powered and in idually controlled by micropower application specific integrated circuits (ASICs). Each ASIC controls 43 electrodes and draws 3.18 mW of power when stimulating through 24 channels. We measured the linearity of the digital-to-analog convertors (DACs) to be 0.21 LSB (integrated non-linearity) and the variability in timing of stimulation pulses across ASICs to be 172 ns. This work demonstrates the feasibility of a new low power ASIC designed to be implanted in the visual cortex of humans. The fully implantable device will greatly reduce the risks of infection and damage due to mechanical issues.
Publisher: IOP Publishing
Date: 04-06-2021
Abstract: Objective . Stimulus-elicited changes in electroencephalography (EEG) recordings can be represented using Fourier magnitude and phase features (Makeig et al (2004 Trends Cogn. Sci. 8 204–10)). The present study aimed to quantify how much information about hearing responses are contained in the magnitude, quantified by event-related spectral perturbations (ERSPs) and the phase, quantified by inter-trial coherence (ITC). By testing if one feature contained more information and whether this information was mutually exclusive to the features, we aimed to relate specific EEG magnitude and phase features to hearing perception. Approach. EEG responses were recorded from 20 adults who were presented with acoustic stimuli, and 20 adult cochlear implant users with electrical stimuli. Both groups were presented with short, 50 ms stimuli at varying intensity levels relative to their hearing thresholds. Extracted ERSP and ITC features were inputs for a linear discriminant analysis classifier (Wong et al (2016 J. Neural. Eng. 13 036003)). The classifier then predicted whether the EEG signal contained information about the sound stimuli based on the input features. Classifier decoding accuracy was quantified with the mutual information measure (Cottaris and Elfar (2009 J. Neural. Eng. 6 026007), Hawellek et al (2016 Proc. Natl Acad. Sci. 113 13492–7)), and compared across the two feature sets, and to when both feature sets were combined. Main results . We found that classifiers using either ITC or ERSP feature sets were both able to decode hearing perception, but ITC-feature classifiers were able to decode responses to a lower but still audible stimulation intensity, making ITC more useful than ERSP for hearing threshold estimation. We also found that combining the information from both feature sets did not improve decoding significantly, implying that ERSP brain dynamics has a limited contribution to the EEG response, possibly due to the stimuli used in this study. Significance. We successfully related hearing perception to an EEG measure, which does not require behavioral feedback from the listener an objective measure is important in both neuroscience research and clinical audiology.
Publisher: IEEE
Date: 08-2007
Publisher: IEEE
Date: 2005
Publisher: Springer New York
Date: 2015
Publisher: IOP Publishing
Date: 20-08-2018
Publisher: Wiley
Date: 08-03-2018
DOI: 10.1002/HBM.24029
Publisher: Springer Science and Business Media LLC
Date: 27-11-2018
DOI: 10.1038/S41598-018-36257-8
Abstract: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Publisher: Elsevier BV
Date: 05-2009
DOI: 10.1016/J.VISRES.2009.02.018
Abstract: This paper presents the results of the first investigations into the use of bipolar electrical stimulation of the retina with a suprachoroidal vision prosthesis, and the effects of different electrode configurations on localization of responses on the primary visual cortex. Cats were implanted with electrodes in the suprachoroidal space, and electrically evoked potentials were recorded on the visual cortex. Responses were elicited to bipolar and monopolar stimuli, with each stimulating electrode coupled with either six-return electrodes, two-return electrodes, or a single-return electrode. The average charge threshold to elicit a response with bipolar stimulation and six-return electrodes was 76.47+/-8.76 nC. Bipolar stimulation using six-return electrodes evoked responses half the magnitude of those elicited with a single or two-return electrodes. Monopolar stimulation evoked a greater magnitude, and area of cortical activation than bipolar stimulation. This study showed that suprachoroidal, bipolar stimulation can elicit localized activity in the primary visual cortex, with the extent of localization and magnitude of response dependent on the electrode configuration.
Publisher: IOP Publishing
Date: 02-2023
Abstract: Objective. Hearing is an important sensory function that plays a key role in how children learn to speak and develop language skills. Although previous neuroimaging studies have established that much of brain network maturation happens in early childhood, our understanding of the developmental trajectory of language areas is still very limited. We hypothesized that typical development trajectory of language areas in early childhood could be established by analyzing the changes of functional connectivity in normal hearing infants at different ages using functional near-infrared spectroscopy. Approach. Resting-state data were recorded from two bilateral temporal and prefrontal regions associated with language processing by measuring the relative changes of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) concentrations. Connectivity was calculated using magnitude-squared coherence of channel pairs located in (a) inter-hemispheric homologous and (b) intra-hemispheric brain regions to assess connectivity between homologous regions across hemispheres and two regions of interest in the same hemisphere, respectively. Main results. A linear regression model fitted to the age vs coherence of inter-hemispheric homologous test group revealed a significant coefficient of determination for both HbO ( R 2 = 0.216, p = 0.0169) and HbR ( R 2 = 0.206, p = 0.0198). A significant coefficient of determination was also found for intra-hemispheric test group for HbO ( R 2 = 0.237, p = 0.0117) but not for HbR ( R 2 = 0.111, p = 0.0956). Significance. The findings from HbO data suggest that both inter-hemispheric homologous and intra-hemispheric connectivity between primary language regions significantly strengthen with age in the first year of life. Mapping out the developmental trajectory of primary language areas of normal hearing infants as measured by functional connectivity could potentially allow us to better understand the altered connectivity and its effects on language delays in infants with hearing impairments.
Publisher: IEEE
Date: 08-2006
Publisher: Springer Science and Business Media LLC
Date: 30-05-2018
DOI: 10.1038/S41598-018-26457-7
Abstract: Recent work has demonstrated the feasibility of minimally-invasive implantation of electrodes into a cortical blood vessel. However, the effect of the dura and blood vessel on recording signal quality is not understood and may be a critical factor impacting implementation of a closed-loop endovascular neuromodulation system. The present work compares the performance and recording signal quality of a minimally-invasive endovascular neural interface with conventional subdural and epidural interfaces. We compared bandwidth, signal-to-noise ratio, and spatial resolution of recorded cortical signals using subdural, epidural and endovascular arrays four weeks after implantation in sheep. We show that the quality of the signals (bandwidth and signal-to-noise ratio) of the endovascular neural interface is not significantly different from conventional neural sensors. However, the spatial resolution depends on the array location and the frequency of recording. We also show that there is a direct correlation between the signal-noise-ratio and classification accuracy, and that decoding accuracy is comparable between electrode arrays. These results support the consideration for use of an endovascular neural interface in a clinical trial of a novel closed-loop neuromodulation technology.
Publisher: Society for Neuroscience
Date: 22-06-2011
Publisher: Elsevier BV
Date: 04-2015
Publisher: Springer Science and Business Media LLC
Date: 11-01-2016
DOI: 10.1038/NN.4210
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.HEARES.2018.09.006
Abstract: Cortical auditory evoked potential (CAEP) thresholds have been shown to correlate well with behaviourally determined hearing thresholds. Growth functions of CAEPs show promise as an alternative to single level detection for objective hearing threshold estimation however, the accuracy and clinical relevance of this method is not well examined. In this study, we used temporal and spectral CAEP features to generate feature growth functions. Spectral features may be more robust than traditional peak-picking methods where CAEP morphology is variable, such as in children or hearing device users. Behavioural hearing thresholds were obtained and CAEPs were recorded in response to a 1 kHz puretone from twenty adults with no hearing loss. Four features, peak-to-peak litude, root-mean-square, peak spectral power and peak phase-locking value (PLV) were extracted from the CAEPs. Functions relating each feature with stimulus level were used to calculate objective hearing threshold estimates. We assessed the performance of each feature by calculating the difference between the objective estimate and the behaviourally-determined threshold. We compared the accuracy of the estimates using each feature and found that the peak PLV feature performed best, with a mean threshold error of 2.7 dB and standard deviation of 5.9 dB from behavioural threshold across subjects. We also examined the relation between recording time, data quality and threshold estimate errors, and found that on average for a single threshold, 12.7 minutes of recording was needed for a 95% confidence that the threshold estimate was within 20 dB of the behavioural threshold using the peak-to-peak litude feature, while 14 minutes is needed for the peak PLV feature. These results show that the PLV of CAEPs can be used to find a clinically relevant hearing threshold estimate. Its potential stability in differing morphology may be an advantage in testing infants or cochlear implant users.
Start Date: 11-2021
End Date: 12-2024
Amount: $492,586.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2020
End Date: 12-2023
Amount: $425,000.00
Funder: Australian Research Council
View Funded Activity