title: Temporal alignment of electrocorticographic recordings for upper limb movement.
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.
authors: Department of Electrical and Computer Engineering, University of Toronto Toronto, ON, Canada ; Institute of Biomaterials and Biomedical Engineering, University of Toronto Toronto, ON, Canada.
authors: Omid
authors: O
authors: Talakoub
authors: Institute of Biomaterials and Biomedical Engineering, University of Toronto Toronto, ON, Canada ; Rehabilitation Engineering Laboratory, Toronto Rehabilitation Institute, University Health Network Toronto, ON, Canada.
authors: Milos R
authors: MR
authors: Popovic
authors: Division of Functional Neurosurgery of Institute of Psychiatry, Department of Neurology, University of Sao Paulo Medical School Sao Paulo, Brazil.
authors: Jessie
authors: J
authors: Navaro
authors: Division of Functional Neurosurgery of Institute of Psychiatry, Department of Neurology, University of Sao Paulo Medical School Sao Paulo, Brazil ; Division of Neurosurgery, Toronto Western Hospital, University of Toronto Toronto, ON, Canada.
authors: Clement
authors: C
authors: Hamani
authors: Division of Functional Neurosurgery of Institute of Psychiatry, Department of Neurology, University of Sao Paulo Medical School Sao Paulo, Brazil.
authors: Erich T
authors: ET
authors: Fonoff
authors: Department of Electrical and Computer Engineering, University of Toronto Toronto, ON, Canada ; Institute of Biomaterials and Biomedical Engineering, University of Toronto Toronto, ON, Canada.
authors: Willy
authors: W
authors: Wong
keywords: ECoG; arm movement; dynamic time warping; electrocorticography; kinematics; movement classification
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