Poster Session 04 Program Schedule
02/15/2024
12:00 pm - 01:15 pm
Room: Shubert Complex (Posters 1-60)
Poster Session 04: Neuroimaging | Neurostimulation/Neuromodulation | Teleneuropsychology/Technology
Final Abstract #16
The Neural Effects of Ultra-High Frequency Intracranial Electrical Stimulation
Mark Bowren, University of Iowa, Iowa City, United States
Hiroyuki Oya, University of Iowa, Iowa City, United States
Christopher Petkov, University of Iowa, Iowa City, United States
Matthew Howard, University of Iowa, Iowa City, United States
Category: Neurostimulation/Neuromodulation
Keyword 1: neurostimulation
Keyword 2: connectomics
Keyword 3: neuromodulation
Objective:
Traditionally, lesion-deficit inference in neuropsychology has elucidated brain-behavior relationships with data collected from patients with naturally occurring brain lesions (e.g., due to stroke). However, this approach to lesion-deficit inference is limited by a lack of experimental control over the location and timing of the lesion. By contrast, transient “virtual lesions” induced by direct electrical stimulation of the brain afford a high degree of spatiotemporal control. In particular, stimulation at ultra-high frequencies (1-2 kHz) has been shown to block the propagation of action potentials in animal models and human spinal cord research. However, the effects of ultra-high frequency stimulation (uHFS) on cerebral neural function remain largely unknown. We explored the effects of uHFS on neural function as measured by the fMRI BOLD signal. We hypothesized that 100 Hz stimulation would induce neural activation, whereas uHFS would cause neural deactivation.
Participants and Methods:
3 patients with intractable epilepsy undergoing seizure monitoring with intracranial electroencephalography (iEEG) depth electrodes participated in electrical stimulation-fMRI (es-fMRI) experiments, which involves direct stimulation of neural tissue and recording of ensuing BOLD signal while participants are at rest in an MRI scanner. Specifically, a pulse train at either 100 Hz or 2 kHz (uHFS) was delivered to the brain during 100-millisecond windows (the “stimulation windows”). 10 stimulation windows were equally interspersed across 30-second time blocks (the “stimulation blocks”). BOLD signal was measured between stimulation windows, and during 33-second rest blocks in which no stimulation was applied. Stimulation and rest blocks were alternated until 10 blocks of each type were completed. MRI preprocessing was performed using the fMRIPrep pipeline, and BOLD signal for the stimulation and rest blocks were compared using FSL’s FEAT pipeline (cluster significance threshold p < 0.05). Positive BOLD changes refer to higher BOLD signal during the stimulation blocks relative to rest; negative BOLD refers to the opposite pattern. Across participants, we acquired data to compare the effects of 100 Hz stimulation and uHFS at the same stimulation site 5 times. Stimulation sites included the right ventromedial prefrontal cortex, the right pregenual anterior cingulate cortex, the right mid-cingulate cortex, and the right posterior insula.
Results:
For all runs with 100 Hz stimulation, we found statistically significant positive BOLD changes in the immediate anatomical vicinity of the stimulation site; positive and/or negative BOLD changes distal to stimulation site were also observed and their anatomical patterns varied across stimulation sites. For the uHFS, we found no evidence of BOLD changes at or near the stimulation site; the positive and negative BOLD changes distal to the stimulation site occurred in a different pattern relative to the 100 Hz results.
Conclusions:
100 Hz stimulation is associated with increased neural activity at and surrounding the site of brain stimulation, whereas uHFS is associated with an absence of changes in neural activity at the stimulation site. The two stimulation frequencies also demonstrated differential patterns of neural activity in anatomical locations distal to the stimulation site. Our findings provide evidence for differential neural effects of 100 Hz and uHFS. Future work will be necessary to understand whether uHFS can be used to transiently deactivate neural tissue for lesion-deficit inference.
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