%0 Journal Article %J J Neural Eng %D 2008 %T Two-dimensional movement control using electrocorticographic signals in humans. %A Gerwin Schalk %A Miller, K.J. %A Nicholas R Anderson %A Adam J Wilson %A Smyth, Matt %A Ojemann, J G %A Moran, D %A Jonathan Wolpaw %A Leuthardt, E C %K Adolescent %K Adult %K Brain Mapping %K Data Interpretation, Statistical %K Drug Resistance %K Electrocardiography %K Electrodes, Implanted %K Electroencephalography %K Epilepsy %K Female %K Humans %K Male %K Movement %K User-Computer Interface %X

We show here that a brain-computer interface (BCI) using electrocorticographic activity (ECoG) and imagined or overt motor tasks enables humans to control a computer cursor in two dimensions. Over a brief training period of 12-36 min, each of five human subjects acquired substantial control of particular ECoG features recorded from several locations over the same hemisphere, and achieved average success rates of 53-73% in a two-dimensional four-target center-out task in which chance accuracy was 25%. Our results support the expectation that ECoG-based BCIs can combine high performance with technical and clinical practicality, and also indicate promising directions for further research.

%B J Neural Eng %V 5 %P 75-84 %8 03/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/18310813 %N 1 %R 10.1088/1741-2560/5/1/008 %0 Journal Article %J Stroke %D 2008 %T Unique cortical physiology associated with ipsilateral hand movements and neuroprosthetic implications. %A Wisneski, Kimberly %A Nicholas R Anderson %A Gerwin Schalk %A Smyth, Matt %A Moran, D %A Leuthardt, E C %K Adolescent %K Adult %K Artificial Limbs %K Bionics %K Brain Mapping %K Child %K Dominance, Cerebral %K Electroencephalography %K Female %K Hand %K Humans %K Male %K Middle Aged %K Motor Cortex %K Movement %K Paresis %K Prosthesis Design %K Psychomotor Performance %K Stroke %K User-Computer Interface %K Volition %X

BACKGROUND AND PURPOSE: 

Brain computer interfaces (BCIs) offer little direct benefit to patients with hemispheric stroke because current platforms rely on signals derived from the contralateral motor cortex (the same region injured by the stroke). For BCIs to assist hemiparetic patients, the implant must use unaffected cortex ipsilateral to the affected limb. This requires the identification of distinct electrophysiological features from the motor cortex associated with ipsilateral hand movements.

METHODS: 

In this study we studied 6 patients undergoing temporary placement of intracranial electrode arrays. Electrocorticographic (ECoG) signals were recorded while the subjects engaged in specific ipsilateral or contralateral hand motor tasks. Spectral changes were identified with regards to frequency, location, and timing.

RESULTS: 

Ipsilateral hand movements were associated with electrophysiological changes that occur in lower frequency spectra, at distinct anatomic locations, and earlier than changes associated with contralateral hand movements. In a subset of 3 patients, features specific to ipsilateral and contralateral hand movements were used to control a cursor on a screen in real time. In ipsilateral derived control this was optimal with lower frequency spectra.

CONCLUSIONS: 

There are distinctive cortical electrophysiological features associated with ipsilateral movements which can be used for device control. These findings have implications for patients with hemispheric stroke because they offer a potential methodology for which a single hemisphere can be used to enhance the function of a stroke induced hemiparesis.

%B Stroke %V 39 %P 3351-9 %8 12/2008 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/18927456 %N 12 %R 10.1161/STROKEAHA.108.518175 %0 Journal Article %J J Neural Eng %D 2007 %T Decoding two-dimensional movement trajectories using electrocorticographic signals in humans. %A Gerwin Schalk %A Kubánek, J %A Miller, John W %A Nicholas R Anderson %A Leuthardt, E C %A Ojemann, J G %A Limbrick, D %A Moran, D %A Lester A Gerhardt %A Jonathan Wolpaw %K Adult %K Algorithms %K Arm %K Brain Mapping %K Cerebral Cortex %K Electroencephalography %K Evoked Potentials, Motor %K Female %K Humans %K Male %K Movement %X

Signals from the brain could provide a non-muscular communication and control system, a brain-computer interface (BCI), for people who are severely paralyzed. A common BCI research strategy begins by decoding kinematic parameters from brain signals recorded during actual arm movement. It has been assumed that these parameters can be derived accurately only from signals recorded by intracortical microelectrodes, but the long-term stability of such electrodes is uncertain. The present study disproves this widespread assumption by showing in humans that kinematic parameters can also be decoded from signals recorded by subdural electrodes on the cortical surface (ECoG) with an accuracy comparable to that achieved in monkey studies using intracortical microelectrodes. A new ECoG feature labeled the local motor potential (LMP) provided the most information about movement. Furthermore, features displayed cosine tuning that has previously been described only for signals recorded within the brain. These results suggest that ECoG could be a more stable and less invasive alternative to intracortical electrodes for BCI systems, and could also prove useful in studies of motor function.

%B J Neural Eng %V 4 %P 264-75 %8 09/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17873429 %N 3 %R 10.1088/1741-2560/4/3/012 %0 Journal Article %J Neurosurgery %D 2007 %T Electrocorticographic Frequency Alteration Mapping: A Clinical Technique for Mapping the Motor Cortex. %A Leuthardt, E C %A Miller, John W %A Nicholas R Anderson %A Gerwin Schalk %A Dowling, Joshua %A Miller, John W %A Moran, D %A Ojemann, J G %K Adult %K Biological Clocks %K Brain Mapping %K Electric Stimulation %K Electrodes, Implanted %K Electroencephalography %K Female %K Hand %K Humans %K Male %K Middle Aged %K Motor Cortex %K Oscillometry %K Signal Processing, Computer-Assisted %K Tongue %X

OBJECTIVE: 

Electrocortical stimulation (ECS) has been well established for delineating the eloquent cortex. However, ECS is still coarse and inefficient in delineating regions of the functional cortex and can be hampered by after-discharges. Given these constraints, an adjunct approach to defining the motor cortex is the use of electrocorticographic signal changes associated with active regions of the cortex. The broad range of frequency oscillations are categorized into two main groups with respect to the sensorimotor cortex: low and high frequency bands. The low frequency bands tend to show a power reduction with cortical activation, whereas the high frequency bands show power increases. These power changes associated with the activated cortex could potentially provide a powerful tool in delineating areas of the motor cortex. We explore electrocorticographic signal alterations as they occur with activated regions of the motor cortex, as well as its potential in clinical brain mapping applications.

METHODS: 

We evaluated seven patients who underwent invasive monitoring for seizure localization. Each patient had extraoperative ECS mapping to identify the motor cortex. All patients also performed overt hand and tongue motor tasks to identify associated frequency power changes in regard to location and degree of concordance with ECS results that localized either hand or tongue motor function.

RESULTS: 

The low frequency bands had a high sensitivity (88.9-100%) and a lower specificity (79.0-82.6%) for identifying electrodes with either hand or tongue ECS motor responses. The high frequency bands had a lower sensitivity (72.7-88.9%) and a higher specificity (92.4-94.9%) in correlation with the same respective ECS positive electrodes.

CONCLUSION: 

The concordance between stimulation and spectral power changes demonstrate the possible utility of electrocorticographic frequency alteration mapping as an adjunct method to improve the efficiency and resolution of identifying the motor cortex.

%B Neurosurgery %V 60 %P 260-70; discussion 270-1 %8 04/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17415162 %N 4 Suppl 2 %R 10.1227/01.NEU.0000255413.70807.6E %0 Journal Article %J J Neurosci %D 2007 %T Spectral Changes in Cortical Surface Potentials During Motor Movement. %A Miller, John W %A Leuthardt, E C %A Gerwin Schalk %A Rao, Rajesh P N %A Nicholas R Anderson %A Moran, D %A Miller, John W %A Ojemann, J G %K Adult %K Brain Mapping %K Female %K Humans %K Male %K Middle Aged %K Motor Cortex %K Movement %X

In the first large study of its kind, we quantified changes in electrocorticographic signals associated with motor movement across 22 subjects with subdural electrode arrays placed for identification of seizure foci. Patients underwent a 5-7 d monitoring period with array placement, before seizure focus resection, and during this time they participated in the study. An interval-based motor-repetition task produced consistent and quantifiable spectral shifts that were mapped on a Talairach-standardized template cortex. Maps were created independently for a high-frequency band (HFB) (76-100 Hz) and a low-frequency band (LFB) (8-32 Hz) for several different movement modalities in each subject. The power in relevant electrodes consistently decreased in the LFB with movement, whereas the power in the HFB consistently increased. In addition, the HFB changes were more focal than the LFB changes. Sites of power changes corresponded to stereotactic locations in sensorimotor cortex and to the results of individual clinical electrical cortical mapping. Sensorimotor representation was found to be somatotopic, localized in stereotactic space to rolandic cortex, and typically followed the classic homunculus with limited extrarolandic representation.

%B J Neurosci %V 27 %P 2424-32 %8 02/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17329441 %N 9 %R 10.1523/JNEUROSCI.3886-06.2007 %0 Journal Article %J J Neural Eng %D 2004 %T A brain-computer interface using electrocorticographic signals in humans. %A Leuthardt, E C %A Gerwin Schalk %A Jonathan Wolpaw %A Ojemann, J G %A Moran, D %K Adult %K Brain %K Communication Aids for Disabled %K Computer Peripherals %K Diagnosis, Computer-Assisted %K Electrodes, Implanted %K Electroencephalography %K Evoked Potentials %K Female %K Humans %K Imagination %K Male %K Movement Disorders %K User-Computer Interface %X

Brain-computer interfaces (BCIs) enable users to control devices with electroencephalographic (EEG) activity from the scalp or with single-neuron activity from within the brain. Both methods have disadvantages: EEG has limited resolution and requires extensive training, while single-neuron recording entails significant clinical risks and has limited stability. We demonstrate here for the first time that electrocorticographic (ECoG) activity recorded from the surface of the brain can enable users to control a one-dimensional computer cursor rapidly and accurately. We first identified ECoG signals that were associated with different types of motor and speech imagery. Over brief training periods of 3-24 min, four patients then used these signals to master closed-loop control and to achieve success rates of 74-100% in a one-dimensional binary task. In additional open-loop experiments, we found that ECoG signals at frequencies up to 180 Hz encoded substantial information about the direction of two-dimensional joystick movements. Our results suggest that an ECoG-based BCI could provide for people with severe motor disabilities a non-muscular communication and control option that is more powerful than EEG-based BCIs and is potentially more stable and less traumatic than BCIs that use electrodes penetrating the brain.

%B J Neural Eng %V 1 %P 63-71 %8 06/2004 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/15876624 %N 2 %R 10.1088/1741-2560/1/2/001