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Completed

NCT Number: NCT03785028

Analysis of Electrocorticographic Signals

The objectives of this research are to understand how the brain can keep information in mind ("working memory"), and use this information to guide behavior. The two experiments that fall under this study will collect brain signals from epilepsy patients who are having surgery as part of their treatment. More specifically, these signals will be studied from the time while the patient is performing two cognitive tasks.The endpoints are publication of the results from each of the proposed experiments in peer-reviewed journals.

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Key information

Conditions

Epilepsy Brain Diseases Central Nervous System Diseases Nervous System Diseases

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Wisconsin

Madison, Wisconsin, 53705, United States

About this study

There are 2 separate experiments proposed, both of which use repeated-measures designs.

1: Electrocorticography (ECoG) study of visual working memory. Each trial from the behavioral task will start by presenting subjects with two visual images, one each from two of these three categories: faces, words, and outdoor scenes. They will then be cued as to which one they'll be tested on with a recognition probe, and after the first probe the cuing-probing process is repeated. Patients selected for this study will have depth electrodes implanted in the left medial temporal lobe and/or grids covering left occipital, temporal, and/or parietal cortex, and suitability of a patient's data for the final dataset will require that a minimum of one stimulus category can be decoded from them. (The precise minimum number of trials required cannot be calculated a priori, because this requires knowing the signal-to-noise ratio in a dataset, a property that is highly variable in electrocorticography data.)

  • Electrocorticography of spatial selective attention. Each trial from the behavioral task will start by presenting subjects with a white "+" on a screen, with each arm pointing to a potential target location. During each 92-trial block of trials, only two 180-degree opposing locations will ever be cued, with one arm of the "+" turning yellow and the opposing one turning blue, to indicate with 75% validity the location at which an oriented Gabor patch will appear (5 degrees from fixation; cue color mapping counterbalanced), requiring a speeded "R/L" tilt judgment. Orthogonal to cue-color configuration, half of the trials in each block will begin with presentation of an "x" that will rotate by 45 degrees with an unpredictable lag (.5 sec +/- .3). On these trials, the cue-to-target interval (i.e., from rotation to "+" to color-cue onset) will be 750 msec. On trials that begin with the onset of a "+", cue-to-target interval will vary unpredictably between 650, 750, and 850 msec. Decomposition of alpha-band oscillations (brain waves cycling at roughly 10 times per second) into components associated with each location will be derived by filtering the whole-scalp signal with weights from the inverted encoding model trained to encode the four critical locations.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Participants with implanted electrode arrays who are willing to participate and able to cooperate and follow research instructions will be recruited.
  • Must be able to read
  • Must be able to name objects
  • Must be able to articulate thoughts with spoken language

Exclusion criteria

  • post-operative pain requiring narcotics
  • repeated seizures clouding consciousness
  • IQ of 85 and below
  • post-operative subdural bleeding
  • cerebral pathology affecting the cortical regions from which recordings are made
  • women who are pregnant, or who think they may be pregnant

Treatment and study plan

working memory and attention

Behavioral

working memory and attention tasks

Primary outcomes

  1. Qualitative Measure: Prioritization Cue-related Changes in the Neural Representation of Stimuli Reported as Binary for Prioritized and Unprioritized Item Decodability

    Time frame: Twenty minutes

    This experiment will use a machine learning analysis -- multivariate pattern classification -- to "decode" the brain signals measured by the electrocorticography electrodes. That is, the analysis will determine if the face/word/scene that is being remembered is being represented by these particular brain signals). The primary outcome will be to assess what happens to the neural representation of, say, a face, when the patient is probed that the other stimulus presented on that trial will be tested first - i.e., the analysis will assess the decodability of the two items as a function of their priority for upcoming task demands. Reported here is the categorical performance of Support Vector Machines (SVMs) trained using a 10-fold cross-validation procedure to decode the prioritized and unprioritized memory items (faces, scenes, or words).

  2. Qualitative Measure: Working Memory Delay Period Phase-amplitude Coupling Reported as Direction (Increase/Decrease) for Region and Stimulus Type

    Time frame: Twenty minutes

    Phase-amplitude coupling (PAC) refers to the synchrony between low frequency oscillations and bursts of high-frequency signal, which is interpreted as a proxy for neuronal firing. The primary outcome measure is whether the level of phase-amplitude coupling associated with a stimulus will change (increase, decrease, change to different frequencies) after that stimulus is prioritized or deprioritized by the cue. Reported here is the direction of PAC between low theta oscillations (6 Hz) and high-gamma bursts (>140 Hz) in binary terms according to whether the PAC increased or decreased for the three stimulus types (faces, scenes, or words) in electrode signals analyzed in different brain regions.

  3. Experiment 3.b. Covert Spatial Attention-related Changes in Phase-amplitude Coupling

    Time frame: Twenty minutes

    Phase-amplitude coupling refers to the synchrony between low frequency oscillations and bursts of high-frequency signal, which is interpreted as a proxy for neuronal firing. The primary outcome measure is whether the level of phase-amplitude coupling in tissue representing a region of space that is irrelevant for an entire block of trials will change in a manner that mirrors the dynamic changes expected for each trial's uncued location, or whether it will be insensitive to shifts of attention that are, by definition, never relevant for that tissue over the course of that block of trials.

Sponsors and collaborators

Lead sponsor

University of Wisconsin, Madison

Other

Collaborators

  • National Institute of Mental Health (NIMH)

Registry information

Important dates

Study start
2019
Primary completion
2021
Study completion
2021
First posted
Dec 24, 2018
Registry last updated
May 1, 2024

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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