Publications by authors named "Erik J Aarnoutse"

23 Publications

  • Page 1 of 1

Decoding four hand gestures with a single bipolar pair of electrocorticography electrodes.

J Neural Eng 2021 10 22;18(5). Epub 2021 Oct 22.

Department of Neurology and Neurosurgery, University Medical Center Utrecht Brain Center, Utrecht University, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.

Electrocorticography (ECoG) based brain-computer interfaces (BCIs) can be used to restore communication in individuals with locked-in syndrome. In motor-based BCIs, the number of degrees-of-freedom, and thus the speed of the BCI, directly depends on the number of classes that can be discriminated from the neural activity in the sensorimotor cortex. When considering minimally invasive BCI implants, the size of the subdural ECoG implant must be minimized without compromising the number of degrees-of-freedom.Here we investigated if four hand gestures could be decoded using a single ECoG strip of four consecutive electrodes spaced 1 cm apart and compared the performance between a unipolar and a bipolar montage. For that we collected data of seven individuals with intractable epilepsy implanted with ECoG grids, covering the hand region of the sensorimotor cortex. Based on the implanted grids, we generated virtual ECoG strips and compared the decoding accuracy between (a) a single unipolar electrode (Unipolar Electrode), (b) a combination of four unipolar electrodes (Unipolar Strip), (c) a single bipolar pair (Bipolar Pair) and (d) a combination of six bipolar pairs (Bipolar Strip).We show that four hand gestures can be equally well decoded using 'Unipolar Strips' (mean 67.4 ± 11.7%), 'Bipolar Strips' (mean 66.6 ± 12.1%) and 'Bipolar Pairs' (mean 67.6 ± 9.4%), while 'Unipolar Electrodes' (61.6 ± 5.9%) performed significantly worse compared to 'Unipolar Strips' and 'Bipolar Pairs'.We conclude that a single bipolar pair is a potential candidate for minimally invasive motor-based BCIs and encourage the use of ECoG as a robust and reliable BCI platform for multi-class movement decoding.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1741-2552/ac2c9fDOI Listing
October 2021

FMRI and intra-cranial electrocorticography recordings in the same human subjects reveals negative BOLD signal coupled with silenced neuronal activity.

Brain Struct Funct 2021 Aug 7. Epub 2021 Aug 7.

Department of Radiology, Center for Image Sciences, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.

Positive blood oxygenation level-dependent (BOLD) responses (PBR), as measured by functional Magnetic Resonance Imaging (fMRI), are the most utilized measurements to non-invasively map activity in the brain. Recent studies have consistently shown that BOLD responses are not exclusively positive. Negative BOLD responses (NBR) have been reported in response to specific sensory stimulations and tasks. However, the exact relationship between NBR and the underlying metabolic and neuronal demand is still under debate. In this study, we investigated the neurophysiological basis of negative BOLD using fMRI and intra-cranial electrophysiology (electrocorticography, ECoG) measurements from the same human participants. We show that, for those electrodes that responded to visual stimulation, PBR are correlated with high-frequency band (HFB) responses. Crucially, NBR were associated with an absence of HFB power responses and an unpredicted decrease in the alpha power responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00429-021-02342-4DOI Listing
August 2021

Brain-Computer Interfaces for Communication: Preferences of Individuals With Locked-in Syndrome.

Neurorehabil Neural Repair 2021 03 3;35(3):267-279. Epub 2021 Feb 3.

Leiden University, Netherlands.

Background: Brain-computer interfaces (BCIs) have been proposed as an assistive technology (AT) allowing people with locked-in syndrome (LIS) to use neural signals to communicate. To design a communication BCI (cBCI) that is fully accepted by the users, their opinion should be taken into consideration during the research and development process.

Objective: We assessed the preferences of prospective cBCI users regarding (1) the applications they would like to control with a cBCI, (2) the mental strategies they would prefer to use to control the cBCI, and (3) when during their clinical trajectory they would like to be informed about AT and cBCIs. Furthermore, we investigated if individuals diagnosed with progressive and sudden onset (SO) disorders differ in their opinion.

Methods: We interviewed 28 Dutch individuals with LIS during a 3-hour home visit using multiple-choice, ranking, and open questions. During the interview, participants were informed about BCIs and the possible mental strategies.

Results: Participants rated (in)direct forms of communication, computer use, and environmental control as the most desired cBCI applications. In addition, active cBCI control strategies were preferred over reactive strategies. Furthermore, individuals with progressive and SO disorders preferred to be informed about AT and cBCIs at the moment they would need it.

Conclusions: We show that individuals diagnosed with progressive and SO disorders preferred, in general, the same applications, mental strategies, and time of information. By collecting the opinion of a large sample of individuals with LIS, this study provides valuable information to stakeholders in cBCI and other AT development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1545968321989331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7934157PMC
March 2021

Dorsolateral prefrontal cortex-based control with an implanted brain-computer interface.

Sci Rep 2020 09 22;10(1):15448. Epub 2020 Sep 22.

UMC Utrecht Brain Center, Department of Neurology and Neurosurgery, University Medical Center, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands.

The objective of this study was to test the feasibility of using the dorsolateral prefrontal cortex as a signal source for brain-computer interface control in people with severe motor impairment. We implanted two individuals with locked-in syndrome with a chronic brain-computer interface designed to restore independent communication. The implanted system (Utrecht NeuroProsthesis) included electrode strips placed subdurally over the dorsolateral prefrontal cortex. In both participants, counting backwards activated the dorsolateral prefrontal cortex consistently over the course of 47 and 22 months, respectively. Moreover, both participants were able to use this signal to control a cursor in one dimension, with average accuracy scores of 78 ± 9% (standard deviation) and 71 ± 11% (chance level: 50%), respectively. Brain-computer interface control based on dorsolateral prefrontal cortex activity is feasible in people with locked-in syndrome and may become of relevance for those unable to use sensorimotor signals for control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-71774-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7508852PMC
September 2020

The resolution revolution: Comparing spikes and high frequency oscillations in high-density and standard intra-operative electrocorticography of the same patient.

Clin Neurophysiol 2020 05 2;131(5):1040-1043. Epub 2020 Mar 2.

Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, P.O. Box 85500, 3508 GA Utrecht, the Netherlands; Stichting Epilepsie Instellingen Nederland, Heemstede, P.O. Box 540, 2130 AM Hoofddorp, the Netherlands.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clinph.2020.02.006DOI Listing
May 2020

Sensorimotor ECoG Signal Features for BCI Control: A Comparison Between People With Locked-In Syndrome and Able-Bodied Controls.

Front Neurosci 2019 16;13:1058. Epub 2019 Oct 16.

UMC Utrecht Brain Center, Department of Neurology & Neurosurgery, University Medical Center Utrecht, Utrecht, Netherlands.

The sensorimotor cortex is a frequently targeted brain area for the development of Brain-Computer Interfaces (BCIs) for communication in people with severe paralysis and communication problems (locked-in syndrome; LIS). It is widely acknowledged that this area displays an increase in high-frequency band (HFB) power and a decrease in the power of the low frequency band (LFB) during movement of, for example, the hand. Upon termination of hand movement, activity in the LFB band typically shows a short increase (rebound). The ability to modulate the neural signal in the sensorimotor cortex by imagining or attempting to move is crucial for the implementation of sensorimotor BCI in people who are unable to execute movements. This may not always be self-evident, since the most common causes of LIS, amyotrophic lateral sclerosis (ALS) and brain stem stroke, are associated with significant damage to the brain, potentially affecting the generation of baseline neural activity in the sensorimotor cortex and the modulation thereof by imagined or attempted hand movement. In the Utrecht NeuroProsthesis (UNP) study, a participant with LIS caused by ALS and a participant with LIS due to brain stem stroke were implanted with a fully implantable BCI, including subdural electrocorticography (ECoG) electrodes over the sensorimotor area, with the purpose of achieving ECoG-BCI-based communication. We noted differences between these participants in the spectral power changes generated by attempted movement of the hand. To better understand the nature and origin of these differences, we compared the baseline spectral features and task-induced modulation of the neural signal of the LIS participants, with those of a group of able-bodied people with epilepsy who received a subchronic implant with ECoG electrodes for diagnostic purposes. Our data show that baseline LFB oscillatory components and changes generated in the LFB power of the sensorimotor cortex by (attempted) hand movement differ between participants, despite consistent HFB responses in this area. We conclude that the etiology of LIS may have significant effects on the LFB spectral components in the sensorimotor cortex, which is relevant for the development of communication-BCIs for this population.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnins.2019.01058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805728PMC
October 2019

Stability of a chronic implanted brain-computer interface in late-stage amyotrophic lateral sclerosis.

Clin Neurophysiol 2019 10 27;130(10):1798-1803. Epub 2019 Jul 27.

UMC Utrecht Brain Center, Department of Neurology & Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands. Electronic address:

Objective: We investigated the long-term functional stability and home use of a fully implanted electrocorticography (ECoG)-based brain-computer interface (BCI) for communication by an individual with late-stage Amyotrophic Lateral Sclerosis (ALS).

Methods: Data recorded from the cortical surface of the motor and prefrontal cortex with an implanted brain-computer interface device was evaluated for 36 months after implantation of the system in an individual with late-stage ALS. In addition, electrode impedance and BCI control accuracy were assessed. Key measures included frequency of use of the system for communication, user and system performance, and electrical signal characteristics.

Results: User performance was high consistently over the three years. Power in the high frequency band, used for the control signal, declined slowly in the motor cortex, but control over the signal remained unaffected by time. Impedance increased until month 5, and then remained constant. Frequency of home use increased steadily, indicating adoption of the system by the user.

Conclusions: The implanted brain-computer interface proves to be robust in an individual with late-stage ALS, given stable performance and control signal for over 36 months.

Significance: These findings are relevant for the future of implantable brain-computer interfaces along with other brain-sensing technologies, such as responsive neurostimulation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clinph.2019.07.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6880281PMC
October 2019

High-frequency band temporal dynamics in response to a grasp force task.

J Neural Eng 2019 08 6;16(5):056009. Epub 2019 Aug 6.

UMC Utrecht Brain Center, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.

Objective: Brain-computer interfaces (BCIs) are being developed to restore reach and grasping movements of paralyzed individuals. Recent studies have shown that the kinetics of grasping movement, such as grasp force, can be successfully decoded from electrocorticography (ECoG) signals, and that the high-frequency band (HFB) power changes provide discriminative information that contribute to an accurate decoding of grasp force profiles. However, as the models used in these studies contained simultaneous information from multiple spectral features over multiple areas in the brain, it remains unclear what parameters of movement and force are encoded by the HFB signals and how these are represented temporally and spatially in the SMC.

Approach: To investigate this, and to gain insight in the temporal dynamics of the HFB during grasping, we continuously modelled the ECoG HFB response recorded from nine individuals with epilepsy temporarily implanted with ECoG grids, who performed three different grasp force tasks.

Main Results: We show that a model based on the force onset and offset consistently provides a better fit to the HFB power responses when compared with a model based on the force magnitude, irrespective of electrode location.

Significance: Our results suggest that HFB power, although potentially useful for continuous decoding, is more closely related to the changes in movement. This finding may potentially contribute to the more natural decoding of grasping movement in neural prosthetics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1741-2552/ab3189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266674PMC
August 2019

Optimization of sampling rate and smoothing improves classification of high frequency power in electrocorticographic brain signals.

Biomed Phys Eng Express 2018 May;4

Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands.

Objective: High-frequency band (HFB) activity, measured using implanted sensors over the cortex, is increasingly considered as a feature for the study of brain function and the design of neural-implants, such as Brain-Computer Interfaces (BCIs). One common way of extracting these power signals is using a wavelet dictionary, which involves the selection of different temporal sampling and temporal smoothing parameters, such that the resulting HFB signal best represents the temporal features of the neuronal event of interest. Typically, the use of neuro-electrical signals for closed-loop BCI control requires a certain level of signal downsampling and smoothing in order to remove uncorrelated noise, optimize performance and provide fast feedback. However, a fixed setting of the sampling and smoothing parameters may lead to a suboptimal representation of the underlying neural responses and poor BCI control. This problem can be resolved with a systematic assessment of parameter settings.

Approach: With classification of HFB power responses as performance measure, different combinations of temporal sampling and temporal smoothing values were applied to data from sensory and motor tasks recorded with high-density and standard clinical electrocorticography (ECoG) grids in 12 epilepsy patients.

Main Results: The results suggest that HFB ECoG responses are best performed with high sampling and subsequent smoothing. For the paradigms used in this study, optimal temporal sampling ranged from 29 Hz to 50 Hz. Regarding optimal smoothing, values were similar between tasks (0.1-0.9 s), except for executed complex hand gestures, for which two optimal possible smoothing windows were found (0.4-0.6 s and 0.9-2.7 s).

Significance: The range of optimal values indicates that parameter optimization depends on the functional paradigm and may be subject-specific. Our results advocate a methodical assessment of parameter settings for optimal decodability of ECoG signals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/2057-1976/aac3acDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435154PMC
May 2018

Workshops of the Sixth International Brain-Computer Interface Meeting: brain-computer interfaces past, present, and future.

Brain Comput Interfaces (Abingdon) 2017 30;4(1-2):3-36. Epub 2017 Jan 30.

Brain Center Rudolf Magnus, Dept Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.

The Sixth International Brain-Computer Interface (BCI) Meeting was held 30 May-3 June 2016 at the Asilomar Conference Grounds, Pacific Grove, California, USA. The conference included 28 workshops covering topics in BCI and brain-machine interface research. Topics included BCI for specific populations or applications, advancing BCI research through use of specific signals or technological advances, and translational and commercial issues to bring both implanted and non-invasive BCIs to market. BCI research is growing and expanding in the breadth of its applications, the depth of knowledge it can produce, and the practical benefit it can provide both for those with physical impairments and the general public. Here we provide summaries of each workshop, illustrating the breadth and depth of BCI research and highlighting important issues and calls for action to support future research and development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/2326263X.2016.1275488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5693371PMC
January 2017

Estimated Prevalence of the Target Population for Brain-Computer Interface Neurotechnology in the Netherlands.

Neurorehabil Neural Repair 2017 Jul 22;31(7):677-685. Epub 2017 Jun 22.

1 Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands.

Background: People who suffer from paralysis have difficulties participating in society. Particularly burdensome is the locked-in syndrome (LIS). LIS patients are not able to move and speak but are cognitively healthy. They rely on assistive technology to interact with the world and may benefit from neurotechnological advances. Optimal research and design of such aids requires a well-defined target population. However, the LIS population is poorly characterized and the number of patients in this condition is unknown.

Objective: Here we estimated and described the LIS patient population in the Netherlands to define the target population for assistive (neuro)technology.

Methods: We asked physicians in the Netherlands if they had patients suffering from severe paralysis and communication problems in their files. Physicians responding affirmatively were asked to fill out a questionnaire on the patients' status.

Results: We sent out 9570 letters to general practitioners (GPs), who reported 83 patients. After first screening, the GPs of 46 patients received the questionnaire. Based on the responses, 26 patients were classified as having LIS. Extrapolation of these numbers resulted in a prevalence of 0.73 patients per 100 000 inhabitants. Notable results from the questionnaire were the percentage of patients with neuromuscular disease (>50%) and living at home (>70%).

Conclusions: We revealed an etiologically diverse group of LIS patients. The functioning and needs of these patients were, however, similar and many relied on assistive technology. By characterizing the LIS population, our study may contribute to optimal development of assistive (neuro)technology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1545968317714577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6396873PMC
July 2017

Fully Implanted Brain-Computer Interface in a Locked-In Patient with ALS.

N Engl J Med 2016 11 12;375(21):2060-2066. Epub 2016 Nov 12.

Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus (M.J.V., E.G.M.P., M.P.B., Z.V.F., P.G., S.L., M.A.V.D.B., P.C.V.R., E.J.A., N.F.R.), and the Department of Anesthesiology (T.H.O.), University Medical Center Utrecht, Utrecht, the Netherlands; the Neuropsychology Laboratory, Department of Psychology, European Medical School, Cluster of Excellence Hearing4all, University of Oldenburg, Oldenburg, Germany (M.G.B.); and Neuromodulation Core Technology, Medtronic, Minneapolis (T.D.).

Options for people with severe paralysis who have lost the ability to communicate orally are limited. We describe a method for communication in a patient with late-stage amyotrophic lateral sclerosis (ALS), involving a fully implanted brain-computer interface that consists of subdural electrodes placed over the motor cortex and a transmitter placed subcutaneously in the left side of the thorax. By attempting to move the hand on the side opposite the implanted electrodes, the patient accurately and independently controlled a computer typing program 28 weeks after electrode placement, at the equivalent of two letters per minute. The brain-computer interface offered autonomous communication that supplemented and at times supplanted the patient's eye-tracking device. (Funded by the Government of the Netherlands and the European Union; ClinicalTrials.gov number, NCT02224469 .).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1056/NEJMoa1608085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5326682PMC
November 2016

Decoding hand gestures from primary somatosensory cortex using high-density ECoG.

Neuroimage 2017 02 5;147:130-142. Epub 2016 Dec 5.

Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, the Netherlands. Electronic address:

Electrocorticography (ECoG) based Brain-Computer Interfaces (BCIs) have been proposed as a way to restore and replace motor function or communication in severely paralyzed people. To date, most motor-based BCIs have either focused on the sensorimotor cortex as a whole or on the primary motor cortex (M1) as a source of signals for this purpose. Still, target areas for BCI are not confined to M1, and more brain regions may provide suitable BCI control signals. A logical candidate is the primary somatosensory cortex (S1), which not only shares similar somatotopic organization to M1, but also has been suggested to have a role beyond sensory feedback during movement execution. Here, we investigated whether four complex hand gestures, taken from the American sign language alphabet, can be decoded exclusively from S1 using both spatial and temporal information. For decoding, we used the signal recorded from a small patch of cortex with subdural high-density (HD) grids in five patients with intractable epilepsy. Notably, we introduce a new method of trial alignment based on the increase of the electrophysiological response, which virtually eliminates the confounding effects of systematic and non-systematic temporal differences within and between gestures execution. Results show that S1 classification scores are high (76%), similar to those obtained from M1 (74%) and sensorimotor cortex as a whole (85%), and significantly above chance level (25%). We conclude that S1 offers characteristic spatiotemporal neuronal activation patterns that are discriminative between gestures, and that it is possible to decode gestures with high accuracy from a very small patch of cortex using subdurally implanted HD grids. The feasibility of decoding hand gestures using HD-ECoG grids encourages further investigation of implantable BCI systems for direct interaction between the brain and external devices with multiple degrees of freedom.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2016.12.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322832PMC
February 2017

Action preparation shapes processing in early visual cortex.

J Neurosci 2015 Apr;35(16):6472-80

Departments of Psychiatry.

Preparation for an action, such as grasping an object, is accompanied by an enhanced perception of the object's action-relevant features, such as orientation and size. Cortical feedback from motor planning areas to early visual areas may drive this enhanced perception. To examine whether action preparation modulates activity in early human visual cortex, subjects grasped or pointed to oriented objects while high-resolution fMRI data were acquired. Using multivoxel pattern analysis techniques, we could decode with >70% accuracy whether a grasping or pointing action was prepared from signals in visual cortex as early as V1. These signals in early visual cortex were observed even when actions were only prepared but not executed. Anterior parietal cortex, on the other hand, showed clearest modulation for actual movements. This demonstrates that preparation of actions, even without execution, modulates relevant neuronal populations in early visual areas.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.1358-14.2015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6605225PMC
April 2015

Spatiotemporal characteristics of electrocortical brain activity during mental calculation.

Hum Brain Mapp 2014 Dec 18;35(12):5903-20. Epub 2014 Jul 18.

Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, The Netherlands.

Mental calculation is a complex mental procedure involving a frontoparietal network of brain regions. Functional MRI (fMRI) studies have revealed interesting characteristics of these regions, but the precise function of some areas remains elusive. In the present study, we used electrocorticographic (ECoG) recordings to chronometrically assess the neuronal processes during mental arithmetic. A calculation task was performed during presurgical 3T fMRI scanning and subsequent ECoG monitoring. Mental calculation induced an increase in fMRI blood oxygen level dependent signal in prefrontal, parietal and lower temporo-occipital regions. The group-fMRI result was subsequently used to cluster the implanted electrodes into anatomically defined regions of interest (ROIs). We observed remarkable differences in high frequency power profiles between ROIs, some of which were closely associated with stimulus presentation and others with the response. Upon stimulus presentation, occipital areas were the first to respond, followed by parietal and frontal areas, and finally by motor areas. Notably, we demonstrate that the fMRI activation in the middle frontal gyrus/precentral gyrus is associated with two subfunctions during mental calculation. This finding reveals the significance of the temporal dynamics of neural ensembles within regions with an apparent uniform function. In conclusion, our results shed more light on the spatiotemporal aspects of brain activation during a mental calculation task, and demonstrate that the use of fMRI data to cluster ECoG electrodes is a useful approach for ECoG group analysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/hbm.22593DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6426240PMC
December 2014

Propagating neocortical gamma bursts are coordinated by traveling alpha waves.

J Neurosci 2013 Nov;33(48):18849-54

Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, 6525EN, Nijmegen, The Netherlands, Rudolf Magnus Institute, Utrecht University, 3584CX, Utrecht, The Netherlands, The Sheryl and Daniel R. Tishman Cognitive Neurophysiology Laboratory, Children's Evaluation and Rehabilitation Center, Department of Pediatrics and Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, and Department of Neurological Surgery, Weill Cornell Medical College, New York Presbyterian Hospital, New York, New York 10021.

Neocortical neuronal activity is characterized by complex spatiotemporal dynamics. Although slow oscillations have been shown to travel over space in terms of consistent phase advances, it is unknown how this phenomenon relates to neuronal activity in other frequency bands. We here present electrocorticographic data from three male and one female human subject and demonstrate that gamma power is phase locked to traveling alpha waves. Given that alpha activity has been proposed to coordinate neuronal processing reflected in the gamma band, we suggest that alpha waves are involved in coordinating neuronal processing in both space and time.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.2455-13.2013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262700PMC
November 2013

Cortical theta wanes for language.

Neuroimage 2014 Jan 24;85 Pt 2:738-48. Epub 2013 Jul 24.

Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Department of Neurology and Neurosurgery, Section Brain Function and Plasticity, Utrecht, The Netherlands; Department of Psychology, Stanford University, Stanford, USA.

The role of low frequency oscillations in language areas is not yet understood. Using ECoG in six human subjects, we studied whether different language regions show prominent power changes in a specific rhythm, in similar manner as the alpha rhythm shows the most prominent power changes in visual areas. Broca's area and temporal language areas were localized in individual subjects using fMRI. In these areas, the theta rhythm showed the most pronounced power changes and theta power decreased significantly during verb generation. To better understand the role of this language-related theta decrease, we then studied the interaction between low frequencies and local neuronal activity reflected in high frequencies. Amplitude-amplitude correlations showed that theta power correlated negatively with high frequency activity, specifically across verb generation trials. Phase-amplitude coupling showed that during control trials, high frequency power was coupled to theta phase, but this coupling decreased significantly during verb generation trials. These results suggest a dynamic interaction between the neuronal mechanisms underlying the theta rhythm and local neuronal activity in language areas. As visual areas show a pronounced alpha rhythm that may reflect pulsed inhibition, language regions show a pronounced theta rhythm with highly similar features.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuroimage.2013.07.029DOI Listing
January 2014

Mismatch between electrocortical stimulation and electrocorticography frequency mapping of language.

Brain Stimul 2013 Jul 29;6(4):524-31. Epub 2013 Jan 29.

Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, The Netherlands.

Background: Electrocortical Stimulation Mapping (ESM) is the gold standard for mapping eloquent cortex in neurosurgery. This technique, however, can cause seizures and requires good patient cooperation. Electrocorticography (ECoG) could replace ESM. Several studies have directly compared ESM and ECoG frequency mapping of language cortex, with mixed results. This may be due to ECoG mapping typically being limited to one or a few language tasks, potentially leading to underestimation of language representation.

Objective: To evaluate the influence of the language task on the match between ECoG and ESM, we mapped language function based on episodes of spontaneous conversation with ECoG, and compared this with ESM data in eight epilepsy patients. A verb generation and picture naming task were used as reference standard.

Methods: From the continuous ECoG and video registrations, periods of conversation were identified, distinguishing three conditions: speaking, listening and rest. A power-frequency analysis was done for each condition and the two language tasks. The match between ESM and ECoG frequency mapping was evaluated on the basis of sensitivity and specificity measures.

Results: ECoG activation during spontaneous conversation and language tasks was seen in and around classic language areas. Comparing the electrodes activated in each condition with those indicated as language positive by ESM revealed that there was high specificity but relatively low sensitivity.

Conclusion: The relatively poor match between ESM and ECoG mapping is not improved by using spontaneous language.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.brs.2013.01.001DOI Listing
July 2013

Dissociation between neuronal activity in sensorimotor cortex and hand movement revealed as a function of movement rate.

J Neurosci 2012 Jul;32(28):9736-44

Rudolf Magnus Institute of Neuroscience, Department of Neurology and Neurosurgery, Section of Brain Function and Plasticity, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.

It is often assumed that similar behavior is generated by the same brain activity. However, this does not take into account the brain state or recent behavioral history and movement initiation or continuation may not be similarly generated in the brain. To study whether similar movements are generated by the same brain activity, we measured neuronal population activity during repeated movements. Three human subjects performed a motor repetition task in which they moved their hand at four different rates (0.3, 0.5, 1, and 2 Hz). From high-resolution electrocorticography arrays implanted on motor and sensory cortex, high-frequency power (65-95 Hz) was extracted as a measure of neuronal population activity. During the two faster movement rates, high-frequency power was significantly suppressed, whereas movement parameters remained highly similar. This suppression was nonlinear: after the initial movement, neuronal population activity was reduced most strongly, and the data fit a model in which a fast decline rapidly converged to saturation. The amplitude of the beta-band suppression did not change with different rates. However, at the faster rates, beta power did not return to baseline between movements but remained suppressed. We take these findings to indicate that the extended beta suppression at the faster rates, which may suggest a release of inhibition in motor cortex, facilitates movement initiation. These results show that the relationship between behavior and neuronal activity is not consistent: recent movement influences the state of motor cortex and facilitates next movements by reducing the required level of neuronal activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.0357-12.2012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6622254PMC
July 2012

Error probability of intracranial brain computer interfaces under non-task elicited brain states.

Clin Neurophysiol 2012 Dec 12;123(12):2392-401. Epub 2012 Jun 12.

Department of Neurology and Neurosurgery, University Medical Center Utrecht, The Netherlands.

Objective: Intracranial brain computer interfaces (BCIs) can be connected to the user's cortex permanently. The interfaces response when fed with non-task elicited brain activity becomes important as design criterion: ideally intracranial BCIs should remain silent. We study their error probability in the form of false alarms.

Methods: Using electrocorticograms recorded during task and non-task brain states, we compute false alarms, investigate their origin and introduce strategies to reduce them, using signal detection theory, classifier cascading and adaptation concepts.

Results: We show that the incessant dynamics of the brain is prone to spontaneously produce signals, the spectral and topographical characteristics of which can resemble those associated with common control tasks, generating brain state classification errors.

Conclusions: In addition to hit and bit rates, response of BCIs to non-task brain states constitutes an important measure of BCI performance. Static classification cascading reduces considerably false positives during no-task brain states.

Significance: False alarms in intracranial BCIs are undesirable and could have dangerous consequences for the users. Designs which effectively incorporate the error correction strategies discussed in this paper, could be more successful when taken from the laboratory or acute care setting and used in the real world.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.clinph.2012.05.006DOI Listing
December 2012

Neurophysiologic correlates of fMRI in human motor cortex.

Hum Brain Mapp 2012 Jul 20;33(7):1689-99. Epub 2011 Jun 20.

Section Brain Function and Plasticity, Department of Neurology and Neurosurgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.

The neurophysiological underpinnings of functional magnetic resonance imaging (fMRI) are not well understood. To understand the relationship between the fMRI blood oxygen level dependent (BOLD) signal and neurophysiology across large areas of cortex, we compared task related BOLD change during simple finger movement to brain surface electric potentials measured on a similar spatial scale using electrocorticography (ECoG). We found that spectral power increases in high frequencies (65-95 Hz), which have been related to local neuronal activity, colocalized with spatially focal BOLD peaks on primary sensorimotor areas. Independent of high frequencies, decreases in low frequency rhythms (<30 Hz), thought to reflect an aspect of cortical-subcortical interaction, colocalized with weaker BOLD signal increase. A spatial regression analysis showed that there was a direct correlation between the amplitude of the task induced BOLD change on different areas of primary sensorimotor cortex and the amplitude of the high frequency change. Low frequency change explained an additional, different part of the spatial BOLD variance. Together, these spectral power changes explained a significant 36% of the spatial variance in the BOLD signal change (R(2) = 0.36). These results suggest that BOLD signal change is largely induced by two separate neurophysiological mechanisms, one being spatially focal neuronal processing and the other spatially distributed low frequency rhythms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/hbm.21314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6870225PMC
July 2012

Brain-computer interfacing based on cognitive control.

Ann Neurol 2010 Jun;67(6):809-16

Section of Brain Function and Plasticity, Department of Neurology and Neurosurgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, the Netherlands.

Objective: Brain-computer interfaces (BCIs) translate deliberate intentions and associated changes in brain activity into action, thereby offering patients with severe paralysis an alternative means of communication with and control over their environment. Such systems are not available yet, partly due to the high performance standard that is required. A major challenge in the development of implantable BCIs is to identify cortical regions and related functions that an individual can reliably and consciously manipulate. Research predominantly focuses on the sensorimotor cortex, which can be activated by imagining motor actions. However, because this region may not provide an optimal solution to all patients, other neuronal networks need to be examined. Therefore, we investigated whether the cognitive control network can be used for BCI purposes. We also determined the feasibility of using functional magnetic resonance imaging (fMRI) for noninvasive localization of the cognitive control network.

Methods: Three patients with intractable epilepsy, who were temporarily implanted with subdural grid electrodes for diagnostic purposes, attempted to gain BCI control using the electrocorticographic (ECoG) signal of the left dorsolateral prefrontal cortex (DLPFC).

Results: All subjects quickly gained accurate BCI control by modulation of gamma-power of the left DLPFC. Prelocalization of the relevant region was performed with fMRI and was confirmed using the ECoG signals obtained during mental calculation localizer tasks.

Interpretation: The results indicate that the cognitive control network is a suitable source of signals for BCI applications. They also demonstrate the feasibility of translating understanding about cognitive networks derived from functional neuroimaging into clinical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ana.21985DOI Listing
June 2010

A practical procedure for real-time functional mapping of eloquent cortex using electrocorticographic signals in humans.

Epilepsy Behav 2009 Jul 17;15(3):278-86. Epub 2009 Jun 17.

Brain-Computer Interface R&D Program, Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA.

Functional mapping of eloquent cortex is often necessary prior to invasive brain surgery, but current techniques that derive this mapping have important limitations. In this article, we demonstrate the first comprehensive evaluation of a rapid, robust, and practical mapping system that uses passive recordings of electrocorticographic signals. This mapping procedure is based on the BCI2000 and SIGFRIED technologies that we have been developing over the past several years. In our study, we evaluated 10 patients with epilepsy from four different institutions and compared the results of our procedure with the results derived using electrical cortical stimulation (ECS) mapping. The results show that our procedure derives a functional motor cortical map in only a few minutes. They also show a substantial concurrence with the results derived using ECS mapping. Specifically, compared with ECS maps, a next-neighbor evaluation showed no false negatives, and only 0.46 and 1.10% false positives for hand and tongue maps, respectively. In summary, we demonstrate the first comprehensive evaluation of a practical and robust mapping procedure that could become a new tool for planning of invasive brain surgeries.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.yebeh.2009.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2754703PMC
July 2009
-->