Purpose: To investigate the electrophysiological correlates of human cognition and affective processing. Participants: Drug-resistant epilepsy patients undergoing epilepsy surgery cortical mapping with continuous electrocorticography (ECoG) with intracranial electrodes. Procedures (methods): Participants will perform computer-based cognitive and affective processing tasks during routine long-term monitoring. Intracranial EEG will be collected during the task
Oscillations in different frequency bands like theta, alpha, beta, gamma and high gamma are thought to underlie processing of cognitive and emotional information. For example, theta (3 - 7 Hz) and alpha (8 - 12 Hz) oscillations are known to underlie working memory as well as attentional processing. Theta oscillations are known to differentiate emotional and neutral stimuli while gamma oscillations (30 - 50 Hz) are known to underlie rapid integration of information. The fact that these oscillations are also disrupted in neuropsychiatric disorders underline the importance of these oscillations. A lot of our understanding of these oscillations come from non invasive methods in humans like electroencephalography (EEG), magnetoencephalography (MEG) and invasive methods in animal models. However, EEG and MEG measure oscillations that are generated by collective firing of large cortical patches thereby losing spatial resolution. Also activity from deeper structures like amygdala and hippocampus cannot be picked up in these modalities. Animal models often suffer from the poor translation of behavior from animals to humans and vice versa. Intracranial EEG or Electrocorticography (ECoG) helps overcome the drawbacks described above. Studies using ECoG have become widespread and have been helpful in elucidating the functional roles of different brain regions in cognition and emotion. The investigators aim to utilize these established procedures to study the role of oscillations recorded from different brain regions in cognition and emotion. Patients with medically refractory epilepsy undergo long-term invasive monitoring for surgical resection planning. Electrodes are implanted subdurally over seizure focus to identify seizure onset zone and patients are often in the epilepsy monitoring unit at the Neuroscience hospital for approximately a week. During this period, intracranial EEG is constantly acquired for clinical investigation. The investigators plan to recruit these patients while they undergo long-term monitoring to leverage the rare access to direct brain recordings and study the role of oscillations in cognitive and affective processing. Patients who provide informed consent to participate in the study will perform computer based cognitive and emotional processing tasks.
Study Type
Sternberg Task Items, which can be visually presented alphabets, shapes or numbers or sound tones presented through speakers, will be presented to the participant. The participant will need to maintain the presented items in their memory and indicate, when a single probe item is presented, whether the probe item was present in the immediately preceding list by pressing a key on the keyboard. N-Back Task Items are presented continuously sequentially and participants are instructed to indicate whether items are repeated n items before by pressing a key on the keyboard. The task is divided into blocks of 0,1,2,3 -back trials based on the 'n'. For example in the 2 - back task, the participant has to indicate if the item presented 2 items before matches the current item. Similar to the previous task, the items can be presented visually or auditorily.
Two abstract visual stimuli are presented on the screen and participant is asked to choose one. Unknown to the participant, each stimulus is associated with distinct probabilities of virtual reward such that one stimulus is associated with net gain while the other is associated with net loss. The participant's goal is to maximize the reward. Once the participant identifies the stimulus associated with net gain, the reward probabilities are reversed. This process is repeated 5 times.
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States
Intracranial EEG Spectra Power
Spectral analysis of electrophysiology data will be performed using multi-taper fft and wavelet transforms. The measures will be compared between different epochs within the tasks to determine what oscillations are modulated by the task. The correlation between the measures described above and the task performance will also be estimated.
Time frame: Intracranial EEG will be collected simultaneously when the participants perform the task. 1 Hour
Task Performance: Reaction Times
For all the tasks described above, the time from when the response is prompted and when the response is obtained is collected as reaction time. Reaction time is measured in milliseconds.
Time frame: 1 Hour
Intracranial EEG Functional Connectivity Analysis
Functional connectivity between the different electrodes will be measured using phase locking value and Granger causality.
Time frame: Intracranial EEG will be collected simultaneously when the participants perform the task. 1 Hour
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INTERVENTIONAL
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NA
Purpose
BASIC_SCIENCE
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Enrollment
4
On a given trial, participants will be presented with images of two faces side-by-side. The faces will either match in terms of emotion category (e.g., 2 anger faces) or not (e.g., an anger face and a fear face). Faces presented together will always be of the same gender but different identities. Participants will be asked to determine whether the two faces presented depict the same emotion category.