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Manifestation of ocular-muscle EMG contamination in human intracranial recordings

Kovach, Christopher K. and Tsuchiya, Naotsugu and Kawasaki, Hiroto and Oya, Hiroyuki and Howard, Mathew A., III and Adolphs, Ralph (2011) Manifestation of ocular-muscle EMG contamination in human intracranial recordings. NeuroImage, 54 (1). pp. 213-233. ISSN 1053-8119. PMCID PMC2975438.

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It is widely assumed that intracranial recordings from the brain are only minimally affected by contamination due to ocular-muscle electromyogram (oEMG). Here we show that this is not always the case. In intracranial recordings from five surgical epilepsy patients we observed that eye movements caused a transient biphasic potential at the onset of a saccade, resembling the saccadic spike potential commonly seen in scalp EEG, accompanied by an increase in broadband power between 20 and 200 Hz. Using concurrently recorded eye movements and high-density intracranial EEG (iEEG) we developed a detailed overview of the spatial distribution and temporal characteristics of the saccade-related oculomotor signal within recordings from ventral, medial and lateral temporal cortex. The occurrence of the saccadic spike was not explained solely by reference contact location, and was observed near the temporal pole for small (< 2 deg) amplitude saccades and over a broad area for larger saccades. We further examined the influence of saccade-related oEMG contamination on measurements of spectral power and interchannel coherence. Contamination manifested in both spectral power and coherence measurements, in particular, over the anterior half of the ventral and medial temporal lobe. Next, we compared methods for removing the contaminating signal and found that nearest-neighbor bipolar re-referencing and ICA filtering were effective for suppressing oEMG at locations far from the orbits, but tended to leave some residual contamination at the temporal pole. Finally, we show that genuine cortical broadband gamma responses observed in averaged data from ventral temporal cortex can bear a striking similarity in time course and band-width to oEMG contamination recorded at more anterior locations. We conclude that eye movement-related contamination should be ruled out when reporting high gamma responses in human intracranial recordings, especially those obtained near anterior and medial temporal lobe.

Item Type:Article
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URLURL TypeDescription CentralArticle
Adolphs, Ralph0000-0002-8053-9692
Additional Information:© 2010 Elsevier Inc. Received 18 February 2010, Revised 27 July 2010, Accepted 3 August 2010, Available online 6 August 2010. Olivier David, David Rudrauf, Rick Jenison, two anonymous reviewers. Supported by: NIH Grant R03 MH070497-01A2, NIH Grant R01 D, and Japan Society for the Promotion of Science.
Funding AgencyGrant Number
NIHR03 MH070497-01A2
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:Intracranial EEG; ECoG; Saccadic spike; EMG; Gamma band; Eye movement; Eye muscle
Issue or Number:1
PubMed Central ID:PMC2975438
Record Number:CaltechAUTHORS:20170208-093633217
Persistent URL:
Official Citation:Christopher K. Kovach, Naotsugu Tsuchiya, Hiroto Kawasaki, Hiroyuki Oya, Mathew A. Howard III, Ralph Adolphs, Manifestation of ocular-muscle EMG contamination in human intracranial recordings, NeuroImage, Volume 54, Issue 1, 1 January 2011, Pages 213-233, ISSN 1053-8119, (//
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74150
Deposited By: Tony Diaz
Deposited On:08 Feb 2017 18:05
Last Modified:03 Oct 2019 16:35

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