Analysis of Electrocorticographic Signals
Condition: Epilepsy
MeSH terms: Epilepsy
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      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.)

      2. 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.
    

Intervention name(s): working memory and attention
Intervention type(s): Behavioral
Intervention description(s): working memory and attention tasks
Intervention model: Single Group Assignment
Intervention model description: basic science
Masking: None (Open Label)
Primary purpose: Basic Science