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Temporal alignment of electrocorticographic recordings for upper limb movement.

Talakoub O, Popovic MR, Navaro J, Hamani C, Fonoff ET, Wong W - Front Neurosci (2015)

Bottom Line: In this study, arm speed was used to align neural activity.Four subjects had electrocorticographic (ECoG) electrodes implanted over their primary motor cortex and were asked to perform reaching and retrieving tasks using the upper limb contralateral to the site of electrode implantation.The arm speeds were aligned using a non-linear transformation of the temporal axes resulting in average spectrograms with superior visualization of movement-related neural activity when compared to averaging without alignment.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Toronto Toronto, ON, Canada ; Institute of Biomaterials and Biomedical Engineering, University of Toronto Toronto, ON, Canada.

ABSTRACT
The detection of movement-related components of the brain activity is useful in the design of brain-machine interfaces. A common approach is to classify the brain activity into a number of templates or states. To find these templates, the neural responses are averaged over each movement task. For averaging to be effective, one must assume that the neural components occur at identical times over repeated trials. However, complex arm movements such as reaching and grasping are prone to cross-trial variability due to the way movements are performed. Typically initiation time, duration of movement and movement speed are variable even as a subject tries to reproduce the same task identically across trials. Therefore, movement-related neural activity will tend to occur at different times across the trials. Due to this mismatch, the averaging of neural activity will not bring into salience movement-related components. To address this problem, we present a method of alignment that accounts for the variabilities in the way the movements are conducted. In this study, arm speed was used to align neural activity. Four subjects had electrocorticographic (ECoG) electrodes implanted over their primary motor cortex and were asked to perform reaching and retrieving tasks using the upper limb contralateral to the site of electrode implantation. The arm speeds were aligned using a non-linear transformation of the temporal axes resulting in average spectrograms with superior visualization of movement-related neural activity when compared to averaging without alignment.

No MeSH data available.


Related in: MedlinePlus

Location of implanted ECoG contacts with respect to head representation. Contacts of the first strip of electrodes are labeled 0–3 from distal to proximal and contacts of the second strip are similarly indexed 4–7. Primary motor cortex is colored in velvet and the primary sensory cortex is colored in amber. The area associated with the hand representation is marked in green.
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Figure 1: Location of implanted ECoG contacts with respect to head representation. Contacts of the first strip of electrodes are labeled 0–3 from distal to proximal and contacts of the second strip are similarly indexed 4–7. Primary motor cortex is colored in velvet and the primary sensory cortex is colored in amber. The area associated with the hand representation is marked in green.

Mentions: The participants were implanted with two quadripolar epidural electrodes Lamitrode 3240 (St. Jude Medical Inc., U.S.A.). Each strip consists of a single row of four platinum discs that were 4 mm in diameter and had center-to-center distance of 10 mm. The electrodes were embedded in a silicon membrane. All participants were implanted with two electrode strips. The electrode strips were placed over the premotor, primary motor, and sensory cortices associated with the upper extremity representations. The first strip was placed on the cortices such that the second contact (electrode #1) was over the primary motor cortex. The location of the electrode was confirmed using electrical stimulation and by observing muscle contractions of the contralateral upper limb. Stimulation parameters were: (i) pulse frequency 50 Hz, (ii) pulse duration 100 μs, (iii) monopolar pulses, and (iv) pulse amplitude 3–10 μA. Electrode contacts were numbered 0–3 from distal to proximal. Specifically, stimulation of contact #1 implanted over the motor cortex induced finger or wrist movements. Electrode contacts of the second strip were numbered 4–7 from distal to proximal. The second strip was placed dorsal to the first such that contact #5 (the second contact of the second strip) was positioned over the primary motor cortex and dorsal to contact #1. Figure 1 shows exemplary illustration of the location of implanted electrodes with respect to the head and the cortical area associated with the upper limb.


Temporal alignment of electrocorticographic recordings for upper limb movement.

Talakoub O, Popovic MR, Navaro J, Hamani C, Fonoff ET, Wong W - Front Neurosci (2015)

Location of implanted ECoG contacts with respect to head representation. Contacts of the first strip of electrodes are labeled 0–3 from distal to proximal and contacts of the second strip are similarly indexed 4–7. Primary motor cortex is colored in velvet and the primary sensory cortex is colored in amber. The area associated with the hand representation is marked in green.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4292555&req=5

Figure 1: Location of implanted ECoG contacts with respect to head representation. Contacts of the first strip of electrodes are labeled 0–3 from distal to proximal and contacts of the second strip are similarly indexed 4–7. Primary motor cortex is colored in velvet and the primary sensory cortex is colored in amber. The area associated with the hand representation is marked in green.
Mentions: The participants were implanted with two quadripolar epidural electrodes Lamitrode 3240 (St. Jude Medical Inc., U.S.A.). Each strip consists of a single row of four platinum discs that were 4 mm in diameter and had center-to-center distance of 10 mm. The electrodes were embedded in a silicon membrane. All participants were implanted with two electrode strips. The electrode strips were placed over the premotor, primary motor, and sensory cortices associated with the upper extremity representations. The first strip was placed on the cortices such that the second contact (electrode #1) was over the primary motor cortex. The location of the electrode was confirmed using electrical stimulation and by observing muscle contractions of the contralateral upper limb. Stimulation parameters were: (i) pulse frequency 50 Hz, (ii) pulse duration 100 μs, (iii) monopolar pulses, and (iv) pulse amplitude 3–10 μA. Electrode contacts were numbered 0–3 from distal to proximal. Specifically, stimulation of contact #1 implanted over the motor cortex induced finger or wrist movements. Electrode contacts of the second strip were numbered 4–7 from distal to proximal. The second strip was placed dorsal to the first such that contact #5 (the second contact of the second strip) was positioned over the primary motor cortex and dorsal to contact #1. Figure 1 shows exemplary illustration of the location of implanted electrodes with respect to the head and the cortical area associated with the upper limb.

Bottom Line: In this study, arm speed was used to align neural activity.Four subjects had electrocorticographic (ECoG) electrodes implanted over their primary motor cortex and were asked to perform reaching and retrieving tasks using the upper limb contralateral to the site of electrode implantation.The arm speeds were aligned using a non-linear transformation of the temporal axes resulting in average spectrograms with superior visualization of movement-related neural activity when compared to averaging without alignment.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, University of Toronto Toronto, ON, Canada ; Institute of Biomaterials and Biomedical Engineering, University of Toronto Toronto, ON, Canada.

ABSTRACT
The detection of movement-related components of the brain activity is useful in the design of brain-machine interfaces. A common approach is to classify the brain activity into a number of templates or states. To find these templates, the neural responses are averaged over each movement task. For averaging to be effective, one must assume that the neural components occur at identical times over repeated trials. However, complex arm movements such as reaching and grasping are prone to cross-trial variability due to the way movements are performed. Typically initiation time, duration of movement and movement speed are variable even as a subject tries to reproduce the same task identically across trials. Therefore, movement-related neural activity will tend to occur at different times across the trials. Due to this mismatch, the averaging of neural activity will not bring into salience movement-related components. To address this problem, we present a method of alignment that accounts for the variabilities in the way the movements are conducted. In this study, arm speed was used to align neural activity. Four subjects had electrocorticographic (ECoG) electrodes implanted over their primary motor cortex and were asked to perform reaching and retrieving tasks using the upper limb contralateral to the site of electrode implantation. The arm speeds were aligned using a non-linear transformation of the temporal axes resulting in average spectrograms with superior visualization of movement-related neural activity when compared to averaging without alignment.

No MeSH data available.


Related in: MedlinePlus