Name: recording horizontal saccade performances accurately in neurological patients using electro-oculogram
Uploaded: 2018-03-13T12:30:00
Description: Watch this Scientific Journal Video about Recording Horizontal Saccade Performances Accurately in Neurological Patients Using Electro-oculogram at JoVE.com

Dr. Terao was supported by a Research Project Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan [16K09709,16H01497]. YU was supported by a Research Project Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan [No.25293206, No. 22390181, 15H05881, 16H05322]; by grants from the Research Committee on the Best rTMS Treatment of Parkinson's Disease From the Ministry of Health and Welfare of Japan; and by the Research Committee on Dystonia of the Ministry of Health and Welfare of Japan.

All experimental procedures in this study were approved and conducted according to the guidelines of the institution&#39;s human research ethics committee after obtaining informed consent.
1. Prepare the Subject and the Room for Recoding
<ol>
	<li>Perform recording in a room with low ambient illumination, to allow sufficient light adaptation.</li>
	<li>Have subjects sit in front of a black, concave dome-shaped screen measuring 90-cm in diameter that contains light-emitting diodes (LEDs) embe...

<ol>
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-A saccade study on pathophysiology.</a> Clin Neurophysiol. 127 (2), 1491-1502 (2016).</li><li>Terao, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distinguishing+spinocerebellar+ataxia+with+pure+cerebellar+manifestation+from+multiple+system+atrophy+(MSA-C)+through+saccade+profiles.">Distinguishing spinocerebellar ataxia with pure cerebellar manifestation from multiple system atrophy (MSA-C) through saccade profiles.</a> Clin Neurophysiol. 128 (1), 31-43 (2016).</li><li>Kato, M., Hikosaka, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Saccade+related+responses+of+external+pallidal+neurons+in+monkey.">Saccade related responses of external pallidal neurons in monkey.</a> Neurosci Res. , 218 (1992).</li><li>Hikosaka, O., Fukuda, H., Kato, M., Uetake, K., Nomura, Y., Segawa, M., Segawa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deficits+in+saccadic+eye+movements+in+hereditary+progressive+dystonia+with+marked+diurnal+fluctuation.">Deficits in saccadic eye movements in hereditary progressive dystonia with marked diurnal fluctuation.</a> Hereditary Progressive Dystonia With Marked Diurnal Fluctuation. , 159-177 (1993).</li><li>Fukuda, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+saccade+recording+system+in+humans:+simultaneous+measurment+of+electro-oculography+and+video-oculography.">Development of saccade recording system in humans: simultaneous measurment of electro-oculography and video-oculography.</a> 38th Annual Meeting of Japanese Society of Clinical Neurophysiology. , (2008).</li><li>Constable, P. A., Bach, M., Frishman, L. J., Jeffrey, B. G., Robson, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=International+Society+for+Clinical+Electrophysiology+of+Vision.+ISCEV+Standard+for+clinical+electro-oculography+(2017+update).">International Society for Clinical Electrophysiology of Vision. ISCEV Standard for clinical electro-oculography (2017 update).</a> Doc Ophthalmol. 134 (1), 134 (2017).</li><li>Behrens, F., Weiss, L. 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Although nowadays, the prevailing method for recording saccades has become the VOG, the present study showed that EOG can achieve an accuracy almost comparable to that of VOG if properly implemented (Figure 2). The present EOG method has been shown to achieve a good correlation with VOG when recording horizontal saccades and has been successfully used in many previous studies by the same group12,13,14</su...

There are three major ways to record eye movements, the conventional EOG, the VOG recorded by the video-based eye tracking system, and the scleral search coil (SSC) method. Among them, EOG has been frequently used for recording eye movements in patients since the 1970s because of its simplicity. Widely applicable to the clinical population, this method has been extensively utilized for the diagnosis of neurological patients and has provided useful information about the pathophysiology underlying the disorders1,2,3,4,5. In addition, it is still the only technique that can be feasibly used for recording eye movements during sleep (rapid eye movement during REM sleep and other forms of eye movements).
Since the eyeball is positively charged in its anterior aspect including the cornea relative to its posterior aspect, there is a voltage difference between the anterior and posterior aspects of the eyes termed the corneo-retinal potential. Due to the presence of this potential, the right electrode will become more positive than the left when the subjects turns their gaze toward the right, and become negative when they turn their gaze to the left. Since the voltage difference between the left and right electrodes correlates significantly with the rotation angle of the eyeballs for horizontal saccades, it can be used to measure horizontal eye movements. However, this correlation does not hold for the vertical direction, although vertical EOG still can be used to measure eye movements6. On the other hand, some studies mainly use vertical EOG for monitoring blinks.
Recently, however, VOG has largely taken the place of EOG due to its higher spatial accuracy reaching up to 0.25 - 0.5 degrees, and has now become the standard method for saccade recording in the clinical setting. Meanwhile, EOG has come to be considered rather outdated, since its spatial accuracy, at most 0.5 degrees, is inferior to that of VOG.
However, VOG also has its own drawbacks if used in the clinical setting. There are cases in which VOG is not feasible; for example, eye tracking becomes inaccurate in subjects with a narrow eye cleft such as when the greater area of the cornea is occluded by the eyelids. In patients with cataract lenses, aberrant reflection of the infrared light hampers reliable recording of the gaze direction. Furthermore, EOG can offer advantages for some people for whom their movement disorder makes VOG recording difficult. In addition, the VOG system is more expensive compared to the setup of EOG, which often makes the former unavailable in ordinary medical facilities.
On the other hand, the SSC method is regarded as the gold standard for measuring eye movements. Compared with VOG and EOG, this method provides the highest spatial accuracy, down to 0.1 degrees, and is especially useful when the recording involves high-frequency head motion6. However, this method is potentially invasive, i.e., painful and very irritating to the eyes, and allows recording for only a brief period, approximately under 30 min or shorter7,8,9,10. This short duration makes it a method unsuitable for extensive clinical application, although it has been used successfully in some specialized facilities11.
Based on previous studies recording more than 250 neurological patients and 480 normal subjects by the same group12,13,14,15,16,17,18,19, the present study shows that EOG can be accurate enough to serve as a standard technique of eye movement recording, and widely applicable to the clinical population, while circumventing various drawbacks of VOG and SSC. The present article describes a stable EOG recording method, using an electrode with a wide fringe to allow wide and stable contact with the skin, similar to that of an EEG electrode attached securely on the scalp by collodion for recording a long time period. The impedance of the electrode goes down and the recording becomes stable with time, thereby effectively reducing the artifacts from facial muscles and electroencephalography. This method is compared with simultaneously recorded VOG. When properly prepared and implemented, EOG is as good as VOG in terms of accuracy for recording saccades in neurological patients, and EOG may even be more amenable to saccade recording in normal subjects.

<table border="0" cellpadding="0" cellspacing="0" style="width:927px;" width="926">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Electrode</td>
			<td style="width:276px;">Nihon-Kohden (Tokyo, Japan)</td>
			<td style="width:119px;">NS111-115</td>
			<td style="width:235px;">cup electrode</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Electrode paste</td>
			<td style="width:276px;">Nihon-Kohden (Tokyo, Japan)</td>
			<td style="width:119px;">Gelaid Z-101BA</td>
			<td>gel electrode paste to fill in the cup electrode</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Adhesive tape&#160;</td>
			<td style="width:276px;">Nihon-Kohden (Tokyo, Japan)</td>
			<td style="width:119px;">H261</td>
			<td>double-stick tape for fixating the electrode</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">DC-amplifier</td>
			<td style="width:276px;">Nihon-Kohden (Tokyo, Japan)</td>
			<td style="width:119px;">AN-601G</td>
			<td>amplifier for EOG</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">video-based eye tracking system</td>
			<td style="width:276px;">SR research (Mississauga, Ontario, Canada)</td>
			<td style="width:119px;">Eyelink II</td>
			<td>eye tracking system for recording VOG</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:297px;">Filter</td>
			<td style="width:276px;">NF corporation</td>
			<td style="width:119px;">MS-521</td>
			<td>filter for the EOG signal</td>
		</tr>
	</tbody>
</table>

recording horizontal saccade performances accurately in neurological patients using electro-oculogram

Electro-oculogram (EOG) has been widely used for clinical eye movement recording, especially horizontal saccades, although the video-oculography (VOG) has largely taken the place of it nowadays due to its higher spatial accuracy. However, there are situations in which EOG has clear advantages over VOG, e.g., subjects with narrow eye clefts or having cataract lenses, and patients with movement disorders. The present article shows that if properly implemented, EOG can achieve an accuracy almost as good as VOG with substantial stability for recording, while circumventing problems associated with VOG recording. The present paper describes a practical method for recording horizontal saccades using oculomotor paradigms with high accuracy and stability by EOG in neurological patients. The necessary measures are to use an Ag-AgCl electrode with a wide plastic fringe capable of reducing noise, and to wait for sufficient light adaptation to occur. This waiting period also helps to lower the impedance between the electrodes and the skin, thereby ensuring stable signal recorded as time goes by. Furthermore, re-calibration is performed as needed during the task performance. Using this method, the experimenter can avoid drifts of signals, as well as contamination of artifacts or noise from the electromyogram and electroencephalogram, and can collect sufficient data for clinical evaluation of saccades. Thus when implemented, EOG can still be a method of high practicability that can be widely applied to neurological patients, but may be effective also for studies in normal subjects.

Figure 2&#160;shows representative simultaneous records of EOG and VOG in a normal subject. 8 trials of VGS are superimposed for EOG (gray curves) and VOG (red curves; Figure 2A). Calibrated by the present method, EOG and VOG data are known to be linear over a range of 5-30 degrees, and the spatial accuracy of the data is 0.5 degrees.
The records obtain...

Watch this Scientific Journal Video about Recording Horizontal Saccade Performances Accurately in Neurological Patients Using Electro-oculogram at JoVE.com

Recording Horizontal Saccade Performances Accurately in Neurological Patients Using Electro-oculogram

The article describes a practical method for recording horizontal eye movements with high accuracy by electro-oculogram in neurological patients, using a cup Ag-AgCl electrode with a wide plastic fringe. Stable measurement requires proper selection and fixation of electrodes, taking sufficient time for light adaptation to occur, and re-calibration as needed.

Electro-oculogram (EOG) has been widely used for clinical eye movement recording, especially horizontal saccades, although the video-oculography (VOG) has ...

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