Performing Behavioral Tasks in Subjects with Intracranial Electrodes

Summary

Patients implanted with intracranial electrodes provide a unique opportunity to record neurological data from multiple areas of the brain while the patient performs behavioral tasks. Here, we present a method of recording from implanted patients that can be reproducible at other institutions with access to this patient population.

Abstract

Patients having stereo-electroencephalography (SEEG) electrode, subdural grid or depth electrode implants have a multitude of electrodes implanted in different areas of their brain for the localization of their seizure focus and eloquent areas. After implantation, the patient must remain in the hospital until the pathological area of brain is found and possibly resected. During this time, these patients offer a unique opportunity to the research community because any number of behavioral paradigms can be performed to uncover the neural correlates that guide behavior. Here we present a method for recording brain activity from intracranial implants as subjects perform a behavioral task designed to assess decision-making and reward encoding. All electrophysiological data from the intracranial electrodes are recorded during the behavioral task, allowing for the examination of the many brain areas involved in a single function at time scales relevant to behavior. Moreover, and unlike animal studies, human patients can learn a wide variety of behavioral tasks quickly, allowing for the ability to perform more than one task in the same subject or for performing controls. Despite the many advantages of this technique for understanding human brain function, there are also methodological limitations that we discuss, including environmental factors, analgesic effects, time constraints and recordings from diseased tissue. This method may be easily implemented by any institution that performs intracranial assessments; providing the opportunity to directly examine human brain function during behavior.

Introduction

Epilepsy is one of the most common brain disorders, characterized by chronically recurrent seizures resulting from excessive electrical discharges from groups of neurons. Epilepsy affects about 50 million people worldwide and approximately 40% of all individuals with epilepsy have intractable seizures that cannot completely be controlled by medical therapy¹. Surgery may result in seizure free status if the brain areas responsible for the generation of seizures (the epileptogenic zone - EZ) are localized and surgically removed or disconnected. In order to define the anatomical location of the EZ and its proximity with possible cortical and subcortical eloque....

Protocol

All tasks were performed according to an approved protocol submitted to the Institutional Review Board (IRB) of the Cleveland Clinic Foundation. An informed consent process was conducted with each patient prior to all research activities. In this example, a subject that meets study criterion that has had stereo-electroencephalography (SEEG) electrodes implanted for seizure is chosen. The project was discussed with the subject and they have consented to participate.

1. Patient Enrollment

1. Evaluate patients with refractory epilepsy in consideration for intracranial electrode implantation. If the patient is a good candidate for the ....

Results

In these results we present the analysis of the SEEG data from the limbic system captured in one subject playing the War Task. We can demonstrate that various aspects of the War Task evoke significant gamma-band (40 - 150 Hz) modulation in the limbic system (Figure 1). As seen, in the visual cortex, the presentation of an object on the screen results in a fast latency (~200 msec) wide band response regardless of the task contingency. In addition, there appears to be differences in the duration of the res.......

Discussion

Here we have presented a method for performing intracranial electrophysiological studies in humans as they engage in a behavioral task. This methodology and its simple permutations are important for studying human movement and cognition. While there inherently exists advantages and disadvantages to any technique, recording from intracranial electrodes has advantages over other electrophysiological and imaging techniques. Two of the major advantages are the ability to collect high quality data with better control and desi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
InMotion ARM	Interactive Motion Technologies	InMotion Arm	http://interactive-motion.com/inmotion-arm-the-new-standard-of-care/ Equipment our lab used, can use other equipment to collect data
MATLAB	Mathworks Inc	MATLAB	http://www.mathworks.com/ Need version r2007b or higher to run Monkeylogic
Data Acquisition Toolbox	Mathworks Inc	Data Acquisition Toolbox	http://www.mathworks.com/products/daq/ Must have to run Monkeylogic
Image Processing Toolbox	Mathworks Inc	Image Processing Toolbox	http://www.mathworks.com/products/image/ Must have to run Monkeylogic
Monkeylogic	Wael Asaad and David Freedman	Monkeylogic	http://www.brown.edu/Research/monkeylogic/ Free download, must have MATLAB to run
Chronux	Medametrics, LLC	Data Processing Toolbox	http://www.chronux.org/
Brainstorm		MEG/EEG Analysis Application	http://neuroimage.usc.edu/brainstorm/
Laptop	Dell	Latitude E5530	http://www.dell.com/us/business/p/latitude-e5530/pd?ST=dell%20latitude%20e5530&dgc=ST&cid=263756&lid=4781504&acd=12309152537461010
NI Card	National Instruments	NI USB-6008	http://sine.ni.com/nips/cds/view/p/lang/en/nid/201986 12-Bit, 10 kS/sec Low-Cost Multifunction DAQ