Brain Mapping Using a Graphene Electrode Array

Summary

We present a graphene array-based brain mapping procedure to reduce the invasiveness and improve spatiotemporal resolution. Graphene array-based surface electrodes exhibit long-term biocompatibility, mechanical flexibility, and suitability for brain mapping in a convoluted brain. This protocol allows for constructing multiple forms of sensory maps simultaneously and sequentially.

Abstract

Cortical maps represent the spatial organization of location-dependent neural responses to sensorimotor stimuli in the cerebral cortex, enabling the prediction of physiologically relevant behaviors. Various methods, such as penetrating electrodes, electroencephalography, positron emission tomography, magnetoencephalography, and functional magnetic resonance imaging, have been used to obtain cortical maps. However, these methods are limited by poor spatiotemporal resolution, low signal-to-noise ratio (SNR), high costs, and non-biocompatibility or cause physical damage to the brain. This study proposes a graphene array-based somatosensory mapping method as a feature of electrocorticography that offers superior biocompatibility, high spatiotemporal resolution, desirable SNR, and minimized tissue damage, overcoming the drawbacks of previous methods. This study demonstrated the feasibility of a graphene electrode array for somatosensory mapping in rats. The presented protocol can be applied not only to the somatosensory cortex but also to other cortices such as the auditory, visual, and motor cortex, providing advanced technology for clinical implementation.

Introduction

A cortical map is a set of local patches representing response properties to sensorimotor stimuli in the cerebral cortex. They are a spatial formation of neural networks and enable prediction for perception and cognition. Therefore, cortical maps are useful in evaluating neural responses to external stimuli and processing sensorimotor information^1,2,3,4. Invasive and noninvasive methods are available for cortical mapping. One of the most common invasive methods involves the use of intracortical (or penetrating) electrodes for mapping

Protocol

All animal-handling procedures were approved by the Institutional Animal Care and Use Committee of the Incheon National University (INU-ANIM-2017-08).

1. Animal preparation for surgery

NOTE: Use Sprague Dawley Rat (8-10 weeks old) without the sex bias for this experiment.

1. Anesthetize the rat with 90 mg/kg ketamine and 10 mg/kg xylazine cocktail intraperitoneally. To maintain the desired depth of anesthesia throughout the surgery, provide.......

Discussion

The presented protocol provides an in-depth, step-by-step process that explains how to access and map the somatosensory responses of rats using a graphene electrode array. The protocol-acquired data are SEPs that provide somatosensory information that is synaptically linked to each body part.

Several aspects of this protocol should be considered. When extracting cerebrospinal fluid to prevent brain edema and mitigate inflammation, it is crucial for the experimenter not to damage the brainstem .......

Materials

Name	Company	Catalog Number	Comments
1mL syringe	KOREAVACCINE CORPORATION		injecting the drug for anesthesia
3mL syringe	KOREAVACCINE CORPORATION		injecting the drug for anesthesia
Bone rongeur	Fine Science Tools	16220-14	remove the skull
connector	Gbrain		Connect graphene electrode to headstage
drill	FALCON tool		grind the skull
drill bits	Osstem implant		grind the skull
Graefe iris forceps slightly curved serrated	vubu	vudu-02-73010	remove the tissue from the skull or hold wiper
graphene multielectrode array	Gbrain		records signals from neuron
isoflurane	Hana Pharm Corporation		sacrifce the subject
ketamine	yuhan corporation		used for anesthesia
lidocaine(2%)	Daihan pharmaceutical		local anesthetic
Matlab R2021b	Mathworks		Data analysis Software
mosquito hemostats	Fine Science Tools	91309-12	fasten the scalp
ointment	Alcon		prevent eye from drying out
povidone	Green Pharmaceutical corporation		disinfect the incision area
RHS 32ch Stim/Record headstage	intan technologies	M4032	connect connector to interface cable and contain intan RHS stim/amplifier chip
RHS 6-ft (1.8m) Stim SPI interface cable	intan technologies	M3206	connect graphene electrode to headstage
RHS Stim/Recording controller software	intan technologies		Data Acquisition Software
RHS stimulation/ Recording controller	intan technologies	M4200
saline	JW Pharmaceutical
scalpel	Hammacher	HSB 805-03
stereotaxic instrument	stoelting		fasten the subject
sterile Hypodermic Needle	KOREAVACCINE CORPORATION		remove the dura mater
Steven Iris Tissue Forceps	KASCO	50-2026	remove the dura mater
surgical blade no.11	FEATHER		inscise the scalp
surgical sicssors	Fine Science Tools	14090-09	inscise the scalp and remove the dura mater
wooden stick			whisker stimulation
xylazine	Bayer Korea		used for anesthesia