Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

Summary

We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

Abstract

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable because of the plunger-spring-barrel structural facet and mechanical strengths resulting from metal materials. The whole process for acquiring the VEP responses in vivo from a mouse consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing. This paper presents representative measurements of VEP responses from multiple mice with a submicro-voltage signal resolution and sub-hundred millisecond temporal resolution. Although the proposed method is safer and more convenient compared to other previously reported animal EEG acquiring methods, there are remaining issues including how to enhance the signal-to-noise ratio and how to apply this technique with freely moving animals. The proposed method utilizes easily available resources and shows a repetitive VEP response with a satisfactory signal quality. Therefore, this method could be utilized for longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

Introduction

As the number of patients with senile degenerative brain diseases such as dementia, Alzheimer's, Parkinsonian syndromes, and stroke have increased with an aging population and an increasing life expectancy, the long-term societal burden of these diseases has also increased^1,2,3. In addition, most neurodevelopmental diseases, such as Schizophrenia and autism, are accompanied by cognitive and behavioral disorders which affect a patient's whole life^2,3,4. For this reason, resear....

Protocol

Animal care and handling followed the institutional guideline of the Gwangju Institute of Science and Technology (GIST).

NOTE: The procedure for acquiring the VEP signal from a mouse in vivo consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing.

1. Sensor Assembly

1. Prepare sixteen pins for one non-invasive electrode.
   NOTE: Each pin-type electrode consists of three parts: a probe head plunger, an internal spring, and a barrel as shown in Figure 1a. The length of each pin is 13 mm, and the adjustab....

Results

We calculated the ensemble average of VEP responses from eleven mice as shown in Figure 2. This result shows the VEP responses obtained through this experiment from the pre-stimulation period (-300 ms) to the post-stimulation period (600 ms), as the stimulation is given at time 0 s. It is noticeable that the signal fluctuates only for a while (less than 300 ms) after the stimulation, while the signal steadily stabilizes over time during the post-stimulation p.......

Discussion

We firstly focused on the design of the sensor, prioritizing practicality by minimizing complex surgical procedures. The deformable EEG sensor is comprised of sixteen pins: fourteen for recording, one for ground, and the last one for reference electrodes. Each electrode has the plunger-spring-barrel structure, which applies deformability onto the electrode's contact surface, so they facilitate uniform and stable signal acquisition from the curved and tender mouse's scalp. Considering the welfare of the animals, we tried .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Ketamine 50 Inj. (Vial)	Yuhan	-	Ketamine HCl 57.68 mg
Zoletil 50 Inj.	Virbac	-	Tiletamina 125 mg/ Zolazepam 125 mg
Rompun 2% Inj.	BAYER	-	Xylazine hydrochloride 23.32mg/mL
Hycell solution 2%	Samil	-	Hydroxypropylmethylcellulose 20 mg
Puralube Vet Ointment 3.5 mg	Pharmaderm	-
Saline solution Inj.	JW Pharmaceutical	-	NaCl 9 g/1000 mL
Veet Hair Removal Cream – Legs & Body - Sensitive Skin	Reckitt Benckiser	-	depilatory
Skins - Surgical Skin Marker	Surgmed	S-3000	STERILE - Multi-Tip Fine Marker with ruler and label set
Stainless Steel Micro Spatulas	HEATHROW SCIENTIFIC	HS15907	One Round Flat End, 2L x 5/16W"
cotton swap
Stereotaxic, Desktop Digi Single	RWD Life Science	68025
Mouse Adapter	RWD Life Science	68010
Ear Bar for Mouse Non-Rupture	RWD Life Science	68306
Mitsar-EEG 202-24	MITSAR		amplifier
EEGStudio EEG acquisition software	MITSAR
White flash stimulator	MITSAR	MITSAR Flash stimulator
BCI2000 software	Schalk lab
g.USBamp	g.tec	0216
g.Power-g.USBamp	g.tec	0247
441 style straight body Touch Proof connector	PlasticsOne	441000PSW080001	441 - 000 PSW 80" (BLACK)
Standard probe	LEENO	SK100CSW	http://www.globalinterpark.com/detail/detail?prdNo=2114277241&dispNo=001851006012
Precision engraving machine tools	TINYROBO	TinyCNC-6060C
Heat shirink	3M	FP301