Effects of Sensory Flicker and Electrical Flicker Stimulation

Not Applicable

Completed

Interventions: Device: Customized version of DAVID device
Device: Blackrock CereStim

Brief Summary: The study will evaluate whether sensory flicker can modulate neural activity of deep brain regions in humans, and whether it can have relevant effects on behavior. Moreover, it will compare those effects to the gold-standard method of modulating brain circuits, direct electrical stimulation of the brain (the same mechanism as deep brain stimulation), using a powerful within-subjects design.

Detailed Description: Clinical trials have explored the modulation of brain circuits to treat several brain disorders, including Parkinson's Disease, Alzheimer's Disease (AD), depression, and Obsessive-Compulsive Disorder (OCD). However, current means to non-invasively modulate brain activity are limited.

The study will evaluate whether sensory flicker can modulate neural activity of deep brain regions in humans, and whether it can have relevant effects on behavior. Moreover, it will compare those effects to the gold-standard method of modulating brain circuits, direct electrical stimulation of the brain (the same mechanism as deep brain stimulation), using a powerful within-subjects design.

Recruitment & Eligibility

Inclusion Criteria

Adult (>18 years, regardless of gender, race or ethnicity).
To be implanted with intracranial depth or grid/strip electrodes for surgical evaluation.
Patient was not shown, during phase I seizure monitoring, to exhibit abnormal EEG activity in response to photic stimulation, and is not clinically suspected to be susceptible to photic-induced seizures.
Patient has no pre-existing diagnosis of autism.
Patient is not considered at risk for psychogenic nonepileptic seizures (PNES) triggered by sensory stimulation.
Fluent in English.
Able to understand an informed consent (comprehend potential risks and benefits).
Give written and verbal informed consent to all experiments patient would participate in.

Exclusion Criteria

Arm && Interventions

Group	Intervention	Description
Sensory Flicker Stimulation	Customized version of DAVID device	Participants will be exposed for about 10 to 60 minutes at a time, to a sequence of sensory flicker trials each lasting a few seconds to 5 minutes, while their eyes are open or closed. Each trial may include the following modalities and frequencies of flicker: * Modalities: auditory only, visual only, or audiovisual combined. * Frequencies: random, or anywhere from 3Hz to 200Hz. Additionally, subjects may be exposed to individual pulses of light and/or sound, i.e. around or less than 1 pulse /second, for up to 20 minutes at a time.
Electrical Flicker Stimulation	Blackrock CereStim	Participants will be exposed to direct electrical brain stimulation with low-amplitude current, at given flicker frequencies. Participants will be exposed to frequencies ranging from 5-100Hz, for up to 10 seconds at a time. Initially, frequencies of 5.5Hz and 40Hz will be tested. During brain stimulation sessions, bipolar electrical stimulation will be applied to one or more areas of the brain at a time either with or without associated memory tasks. Stimulation in the absence of any memory task will be applied to assess the subject's neurophysiological response to stimulation and to identify the optimal stimulation parameters for use during memory tasks. Stimulation during behavioral tasks will be applied in an attempt to affect the subject's memory.

Primary Outcome Measures

Name	Time	Method
Fold-change in Oscillatory Activity (Power Spectral Density) in Response to Exposure to Sensory Flicker: Comparing Mean Power Spectral Density at the Frequency of Flicker Being Presented Between Flicker and Baseline Periods	During experiment session (up to 2 hours) during hospital admission (up to 2 weeks)	The power spectral density of the LFP will be measured across stimulus frequencies and modalities of sensory flicker stimuli in visual areas, auditory areas, hippocampus, and prefrontal cortex. To evaluate the effects of sensory flicker on brain activity in various brain regions, researchers compared the average increase in oscillatory neural activity of given recorded brain regions during sensory stimulation, among the total number of recording locations that showed a significant response to sensory stimulation compared to baseline. In participants in whom a condition was repeated across multiple experimental sessions. If a location showed a significant response in multiple sessions, the data point that showed the highest level of response was kept. The average fold-change increase in oscillatory activity, 25th and 75th percentiles, within a region of interest is reported.

Secondary Outcome Measures

Name	Time	Method
Effect of Sensory Flicker on the Rate of Interictal Epileptiform Discharges (IEDs) Which Represent Pathological Activity Often Observed in Epilepsy	During experiment session (up to 2 hours) during hospital admission (up to 2 weeks)	The change of of the sensory flicker effect will be evaluated by the comparison of the whole-brain rate of IEDs between sensory flicker stimulation and baseline (no stimulation).