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Extracting Attempted Hand Movements from EEGs in People with Complete Hand Paralysis Following Stroke.

Muralidharan A, Chae J, Taylor DM - Front Neurosci (2011)

Bottom Line: To reduce inappropriate triggering of a movement-assist device during rest, the classification threshold could be adjusted to require more certainty about one's intent to move before triggering a device.Additionally, a device could be set to activate only after multiple time samples in a row were classified as finger-extension events.These options resulted in some sessions with no false triggers while the person was resting, but moderate-to-high true trigger rates during attempted-movements.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Case Western Reserve University Cleveland, OH, USA.

ABSTRACT
This study examines the feasibility of using electroencephalograms (EEGs) to rapidly detect the intent to open one's hand in individuals with complete hand paralysis following a subcortical ischemic stroke. If detectable, this motor-planning activity could be used in real time to trigger a motorized hand exoskeleton or an electrical stimulation device that opens/closes the hand. While EEG-triggered movement-assist devices could restore function, they may also promote recovery by reinforcing the use of remaining cortical circuits. EEGs were recorded while participants were cued to either relax or attempt to extend their fingers. Linear-discriminant analysis was used to detect onset of finger-extension from the EEGs in a leave-one-trial-out cross-validation process. In each testing trial, the classifier was applied in pseudo-real-time starting from an initial hand-relaxed phase, through movement planning, and into the initial attempted-finger-extension phase (finger-extension phase estimated from typical time-to-movement-onset measured in the unaffected hand). The classifiers detected attempted-finger-extension at a significantly higher rate during both motor-planning and early attempted execution compared to rest. To reduce inappropriate triggering of a movement-assist device during rest, the classification threshold could be adjusted to require more certainty about one's intent to move before triggering a device. Additionally, a device could be set to activate only after multiple time samples in a row were classified as finger-extension events. These options resulted in some sessions with no false triggers while the person was resting, but moderate-to-high true trigger rates during attempted-movements.

No MeSH data available.


Related in: MedlinePlus

Fraction of trials with a false trigger in the rest epoch (X axis) vs. a true trigger in the motor-planning epoch (Y axis) when different numbers of consecutive-time samples must be classified as finger-extension before a hypothetical device would be activated (2 = blue, 3 = green, 4 = red, and 5 = pink). Original classification thresholds were set to achieve the false-positive rates indicated at the bottom of the figure. In the top row, the duration of the motor-planning phase was calculated using the median time-to-movement-onset calculated from the unaffected hand (no extension). In the bottom row, the assumed motor-planning phase was extended by 600 ms. Solid diagonal line in each plot indicates the ratio of the mean true-and false-positive rates calculated without regard to consecutive triggers.
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Figure 4: Fraction of trials with a false trigger in the rest epoch (X axis) vs. a true trigger in the motor-planning epoch (Y axis) when different numbers of consecutive-time samples must be classified as finger-extension before a hypothetical device would be activated (2 = blue, 3 = green, 4 = red, and 5 = pink). Original classification thresholds were set to achieve the false-positive rates indicated at the bottom of the figure. In the top row, the duration of the motor-planning phase was calculated using the median time-to-movement-onset calculated from the unaffected hand (no extension). In the bottom row, the assumed motor-planning phase was extended by 600 ms. Solid diagonal line in each plot indicates the ratio of the mean true-and false-positive rates calculated without regard to consecutive triggers.

Mentions: Figure 4 shows the effects of applying an additional requirement of detecting multiple consecutive finger-extension classification events before triggering a hypothetical movement-assist device. The X coordinate indicates the fraction of trials that had a false trigger during the relaxed epoch. The Y coordinate indicates the fraction of trials that had a true trigger during the motor-planning epoch. Color indicates the number of consecutive-events needed to trigger a device (2 = blue, 3 = green, 4 = red, and 5 = pink). Each data point within each color represents performance in a different session. Perfect performance would be in the upper left corner of each plot. Nearly all sessions and testing conditions had more trials with true triggers than false triggers.


Extracting Attempted Hand Movements from EEGs in People with Complete Hand Paralysis Following Stroke.

Muralidharan A, Chae J, Taylor DM - Front Neurosci (2011)

Fraction of trials with a false trigger in the rest epoch (X axis) vs. a true trigger in the motor-planning epoch (Y axis) when different numbers of consecutive-time samples must be classified as finger-extension before a hypothetical device would be activated (2 = blue, 3 = green, 4 = red, and 5 = pink). Original classification thresholds were set to achieve the false-positive rates indicated at the bottom of the figure. In the top row, the duration of the motor-planning phase was calculated using the median time-to-movement-onset calculated from the unaffected hand (no extension). In the bottom row, the assumed motor-planning phase was extended by 600 ms. Solid diagonal line in each plot indicates the ratio of the mean true-and false-positive rates calculated without regard to consecutive triggers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3066795&req=5

Figure 4: Fraction of trials with a false trigger in the rest epoch (X axis) vs. a true trigger in the motor-planning epoch (Y axis) when different numbers of consecutive-time samples must be classified as finger-extension before a hypothetical device would be activated (2 = blue, 3 = green, 4 = red, and 5 = pink). Original classification thresholds were set to achieve the false-positive rates indicated at the bottom of the figure. In the top row, the duration of the motor-planning phase was calculated using the median time-to-movement-onset calculated from the unaffected hand (no extension). In the bottom row, the assumed motor-planning phase was extended by 600 ms. Solid diagonal line in each plot indicates the ratio of the mean true-and false-positive rates calculated without regard to consecutive triggers.
Mentions: Figure 4 shows the effects of applying an additional requirement of detecting multiple consecutive finger-extension classification events before triggering a hypothetical movement-assist device. The X coordinate indicates the fraction of trials that had a false trigger during the relaxed epoch. The Y coordinate indicates the fraction of trials that had a true trigger during the motor-planning epoch. Color indicates the number of consecutive-events needed to trigger a device (2 = blue, 3 = green, 4 = red, and 5 = pink). Each data point within each color represents performance in a different session. Perfect performance would be in the upper left corner of each plot. Nearly all sessions and testing conditions had more trials with true triggers than false triggers.

Bottom Line: To reduce inappropriate triggering of a movement-assist device during rest, the classification threshold could be adjusted to require more certainty about one's intent to move before triggering a device.Additionally, a device could be set to activate only after multiple time samples in a row were classified as finger-extension events.These options resulted in some sessions with no false triggers while the person was resting, but moderate-to-high true trigger rates during attempted-movements.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Case Western Reserve University Cleveland, OH, USA.

ABSTRACT
This study examines the feasibility of using electroencephalograms (EEGs) to rapidly detect the intent to open one's hand in individuals with complete hand paralysis following a subcortical ischemic stroke. If detectable, this motor-planning activity could be used in real time to trigger a motorized hand exoskeleton or an electrical stimulation device that opens/closes the hand. While EEG-triggered movement-assist devices could restore function, they may also promote recovery by reinforcing the use of remaining cortical circuits. EEGs were recorded while participants were cued to either relax or attempt to extend their fingers. Linear-discriminant analysis was used to detect onset of finger-extension from the EEGs in a leave-one-trial-out cross-validation process. In each testing trial, the classifier was applied in pseudo-real-time starting from an initial hand-relaxed phase, through movement planning, and into the initial attempted-finger-extension phase (finger-extension phase estimated from typical time-to-movement-onset measured in the unaffected hand). The classifiers detected attempted-finger-extension at a significantly higher rate during both motor-planning and early attempted execution compared to rest. To reduce inappropriate triggering of a movement-assist device during rest, the classification threshold could be adjusted to require more certainty about one's intent to move before triggering a device. Additionally, a device could be set to activate only after multiple time samples in a row were classified as finger-extension events. These options resulted in some sessions with no false triggers while the person was resting, but moderate-to-high true trigger rates during attempted-movements.

No MeSH data available.


Related in: MedlinePlus