Publications by authors named "Angad S Gogia"

10 Publications

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Neuromodulation in Beta-Band Power Between Movement Execution and Inhibition in the Human Hippocampus.

Neuromodulation 2021 Jul 5. Epub 2021 Jul 5.

Department of Neurological Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, USA.

Introduction: The hippocampus is thought to be involved in movement, but its precise role in movement execution and inhibition has not been well studied. Previous work with direct neural recordings has found beta-band (13-30 Hz) modulation in both movement execution and inhibition throughout the motor system, but the role of beta-band modulation in the hippocampus during movement inhibition is not well understood. Here, we perform a Go/No-Go reaching task in ten patients with medically refractory epilepsy to study human hippocampal beta-power changes during movement.

Materials And Methods: Ten epilepsy patients (5 female; ages 21-46) were implanted with intracranial depth electrodes for seizure monitoring and localization. Local field potentials were sampled at 2000 Hz during a Go/No-Go movement task. Comparison of beta-band power between Go and No-Go conditions was conducted using Wilcoxon signed-rank hypothesis testing for each patient. Sub-analyses were conducted to assess differences in the anterior vs. posterior contacts, ipsilateral vs. contralateral contacts, and male vs. female beta power values.

Results: Eight out of ten patients showed significant beta-power decreases during the Go movement response (p < 0.05) compared to baseline. Eight out of ten patients also showed significant beta power increases in the No-Go condition, occurring in the absence of movement. No significant differences were noted between ipsilateral vs. contralateral contacts, nor in anterior vs. posterior hippocampal contacts. Female participants had a higher task success rate than males and had significantly greater beta-power increases in the No-Go condition (p < 0.001).

Conclusion: These findings indicate that increases in hippocampal beta power are associated with movement inhibition. To the best of our knowledge, this study is the first to report this phenomenon in the human hippocampus. The beta band may represent a state-change signal involved in motor processing. Future focus on the beta band in understanding human motor and impulse control will be vital.
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http://dx.doi.org/10.1111/ner.13486DOI Listing
July 2021

Hippocampal and Orbitofrontal Theta Band Coherence Diminishes During Conflict Resolution.

World Neurosurg 2021 Apr 16. Epub 2021 Apr 16.

Department of Neurological Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles, California, USA; USC Neurorestoration Center, Keck School of Medicine of USC, University of Southern California, Los Angeles, California, USA; Department of Biology and Biological Engineering, California Institute of Technology, Pasadena, California, USA.

Objective: Coherence between the hippocampus and other brain structures has been shown with the theta frequency (3-8 Hz). Cortical decreases in theta coherence are believed to reflect response accuracy efficiency. However, the role of theta coherence during conflict resolution is poorly understood in noncortical areas. In this study, coherence between the hippocampus and orbitofrontal cortex (OFC) was measured during a conflict resolution task. Although both brain areas have been previously implicated in the Stroop task, their interactions are not well understood.

Methods: Nine patients were implanted with stereotactic electroencephalography contacts in the hippocampus and OFC. Local field potential data were sampled throughout discrete phases of a Stroop task. Coherence was calculated for hippocampal and OFC contact pairs, and coherence spectrograms were constructed for congruent and incongruent conditions. Coherence changes during cue processing were identified using a nonparametric cluster-permutation t test. Group analysis was conducted to compare overall theta coherence changes among conditions.

Results: In 6 of 9 patients, decreased theta coherence was observed only during the incongruent condition (P < 0.05). Congruent theta coherence did not change from baseline. Group analysis showed lower theta coherence for the incongruent condition compared with the congruent condition (P < 0.05).

Conclusions: Theta coherence between the hippocampus and OFC decreased during conflict. This finding supports existing theories that theta coherence desynchronization contributes to improved response accuracy and processing efficiency during conflict resolution. The underlying theta coherence observed between the hippocampus and OFC during conflict may be distinct from its previously observed role in memory.
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http://dx.doi.org/10.1016/j.wneu.2021.04.023DOI Listing
April 2021

Beta-band modulation in the human hippocampus during a conflict response task.

J Neural Eng 2020 Oct 15. Epub 2020 Oct 15.

Neuroresotoration Center and Department of Neurosurgery and Neurology, University of Southern California, Los Angeles, California, UNITED STATES.

Objective Identify the role of beta-band (13-30 Hz) power modulation in the human hippocampus during conflict processing. Approach We investigated changes in the spectral power of the beta band (13-30 Hz) as measured by depth electrode leads in the hippocampus during a modified Stroop task in six patients with medically-refractory epilepsy. Previous work done with direct electrophysiological recordings in humans has shown hippocampal theta-band (3-8 Hz) modulation during conflict processing. Local field potentials (LFP) sampled at 2k Hz were used for analysis and a non-parametric cluster-permutation t-test was used to identify the time period and frequency ranges of significant power change during cue processing (i.e. post-stimulus, pre-response). Main Results In five of the six patients, we observe a statistically significant increase in hippocampal beta-band power during successful conflict processing in the incongruent trial condition (cluster-based correction for multiple comparisons, p < 0.05). There was no significant beta-band power change observed during the cue processing period of the congruent condition in the hippocampus of these patients. Significance The beta-power changes during conflict processing represented here are consistent with previous studies suggesting that the hippocampus plays a role in conflict processing, but it is the first time that the beta band has been shown to be involved in humans with direct electrophysiological evidence. We propose that beta-band modulation plays a role in successful conflict detection and automatic response inhibition in the human hippocampus as studied during a conflict response task.
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http://dx.doi.org/10.1088/1741-2552/abc1b8DOI Listing
October 2020

Gamma-band modulation in the human amygdala during reaching movements.

Neurosurg Focus 2020 07;49(1):E4

Departments of1Neurological Surgery and.

Objective: Motor brain-computer interface (BCI) represents a new frontier in neurological surgery that could provide significant benefits for patients living with motor deficits. Both the primary motor cortex and posterior parietal cortex have successfully been used as a neural source for human motor BCI, leading to interest in exploring other brain areas involved in motor control. The amygdala is one area that has been shown to have functional connectivity to the motor system; however, its role in movement execution is not well studied. Gamma oscillations (30-200 Hz) are known to be prokinetic in the human cortex, but their role is poorly understood in subcortical structures. Here, the authors use direct electrophysiological recordings and the classic "center-out" direct-reach experiment to study amygdaloid gamma-band modulation in 8 patients with medically refractory epilepsy.

Methods: The study population consisted of 8 epilepsy patients (2 men; age range 21-62 years) who underwent implantation of micro-macro depth electrodes for seizure localization and EEG monitoring. Data from the macro contacts sampled at 2000 Hz were used for analysis. The classic center-out direct-reach experiment was used, which consists of an intertrial interval phase, a fixation phase, and a response phase. The authors assessed the statistical significance of neural modulation by inspecting for nonoverlapping areas in the 95% confidence intervals of spectral power for the response and fixation phases.

Results: In 5 of the 8 patients, power spectral analysis showed a statistically significant increase in power within regions of the gamma band during the response phase compared with the fixation phase. In these 5 patients, the 95% bootstrapped confidence intervals of trial-averaged power in contiguous frequencies of the gamma band during the response phase were above, and did not overlap with, the confidence intervals of trial-averaged power during the fixation phase.

Conclusions: To the authors' knowledge, this is the first time that direct neural recordings have been used to show gamma-band modulation in the human amygdala during the execution of voluntary movement. This work indicates that gamma-band modulation in the amygdala could be a contributing source of neural signals for use in a motor BCI system.
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http://dx.doi.org/10.3171/2020.4.FOCUS20179DOI Listing
July 2020

Beta-band power modulation in the human hippocampus during a reaching task.

J Neural Eng 2020 06 12;17(3):036022. Epub 2020 Jun 12.

Department of Neurological Surgery, Keck School of Medicine of USC, University of Southern California, Los Angeles, CA, United States of America.

Objective: Characterize the role of the beta-band (13-30 Hz) in the human hippocampus during the execution of voluntary movement.

Approach: We recorded electrophysiological activity in human hippocampus during a reach task using stereotactic electroencephalography (SEEG). SEEG has previously been utilized to study the theta band (3-8 Hz) in conflict processing and spatial navigation, but most studies of hippocampal activity during movement have used noninvasive measures such as fMRI. We analyzed modulation in the beta band (13-30 Hz), which is known to play a prominent role throughout the motor system including the cerebral cortex and basal ganglia. We conducted the classic 'center-out' direct-reach experiment with nine patients undergoing surgical treatment for medically refractory epilepsy.

Main Results: In seven of the nine patients, power spectral analysis showed a statistically significant decrease in power within the beta band (13-30 Hz) during the response phase, compared to the fixation phase, of the center-out direct-reach task using the Wilcoxon signed-rank hypothesis test (p < 0.05).

Significance: This finding is consistent with previous literature suggesting that the hippocampus may be involved in the execution of movement, and it is the first time that changes in beta-band power have been demonstrated in the hippocampus using human electrophysiology. Our findings suggest that beta-band modulation in the human hippocampus may play a role in the execution of voluntary movement.
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http://dx.doi.org/10.1088/1741-2552/ab937fDOI Listing
June 2020

A Phantom Study of the Spatial Precision and Accuracy of Stereotactic Localization Using Computed Tomography Imaging with the Leksell Stereotactic System.

World Neurosurg 2020 07 13;139:e297-e307. Epub 2020 Apr 13.

Department of Neurological Surgery, Keck School of Medicine of USC, Los Angeles, California, USA.

Background: Stereotactic localization of neurosurgical targets traditionally relies on computed tomography (CT), which is considered the optimal imaging modality for geometric accuracy. However, in-depth investigations that characterize the precision and accuracy of CT images are lacking. We used a CT phantom to examine interscanner precision and interprotocol accuracy in coordinate localization.

Methods: A polymethylacrylate phantom was scanned with Toshiba Aquilion 64 and GE Healthcare LightSpeed 16 CT scanners, using both helical and incremental single-slice (SS) image acquisition protocols. The X, Y, and Z coordinates of 94 points across 6 surfaces of the phantom were physically measured. The CT scan-derived coordinates were compared with the phantom coordinates and with each other to determine accuracy and precision, respectively.

Results: Using the SS imaging protocol, the mean (SD) interscanner disparity in localization was 0.93 (0.39) mm, given by the average Euclidean distance between the coordinates of the 2 scanners. This discrepancy significantly varied by axis and surface, with the greatest discrepancy in the Z-axis of 0.30 mm (95% confidence interval, 0.25-0.35; P = 0.05) and on the superior surface of 1.30 mm (95% confidence interval, 1.15-1.45; P = 0.05). SS acquisition was significantly more accurate than the helical protocol.

Conclusions: We found evidence of clinically relevant inconsistency between 2 CT scanners used for stereotactic localization. SS image acquisition was superior to helical scanning with respect to localization accuracy. Interscanner consistency cannot be assumed. Institutions would benefit from identifying the errors inherent in their CT scanners.
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http://dx.doi.org/10.1016/j.wneu.2020.03.204DOI Listing
July 2020

Mapping of primary somatosensory cortex of the hand area using a high-density electrocorticography grid for closed-loop brain computer interface.

J Neural Eng 2020 Mar 4. Epub 2020 Mar 4.

University of Southern California, Los Angeles, California, UNITED STATES.

The ideal modality for generating sensation in sensorimotor brain computer interfaces (BCI) has not been determined. Here we report the feasibility of using a high-density "mini"-electrocorticography (mECoG) grid in a somatosensory BCI system. Thirteen subjects with intractable epilepsy underwent standard clinical implantation of subdural electrodes for the purpose of seizure localization. An additional high-density mECoG grid was placed (Adtech, 8 by 8, 1.2-mm exposed, 3-mm center-to-center spacing) over the hand area of primary somatosensory cortex. Following implantation, cortical mapping was performed with stimulation parameters of frequency: 50 Hz, pulse-width: 250 µs, pulse duration: 4 s, polarity: alternating, and current that ranged from 0.5 mA to 12 mA at the discretion of the epileptologist. Location of the evoked sensory percepts was recorded along with a description of the sensation. The hand was partitioned into 48 distinct boxes. A box was included if sensation was felt anywhere within the box. The percentage of the hand covered was 63.9% (± 34.4%) (mean ± s.d.). Mean redundancy, measured as electrode pairs stimulating the same box, was 1.9 (± 2.2) electrodes per box; and mean resolution, measured as boxes included per electrode pair stimulation, was 11.4 (± 13.7) boxes with 8.1 (± 10.7) boxes in the digits and 3.4 (± 6.0) boxes in the palm. Functional utility of the system was assessed by quantifying usable percepts. Under the strictest classification, "dermatomally exclusive" percepts, the mean was 2.8 usable percepts per grid. Allowing "perceptually unique" percepts at the same anatomical location, the mean was 5.5 usable percepts per grid. Compared to the small area of coverage and redundancy of a microelectrode system, or the poor resolution of a standard ECoG grid, a mECoG is likely the best modality for a somatosensory BCI system with good coverage of the hand and minimal redundancy.
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http://dx.doi.org/10.1088/1741-2552/ab7c8eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7483626PMC
March 2020

Dual responsive neurostimulation implants for epilepsy.

J Neurosurg 2019 Jan 25:1-7. Epub 2019 Jan 25.

Departments of1Neurosurgery and.

Closed-loop brain-responsive neurostimulation via the RNS System is a treatment option for adults with medically refractory focal epilepsy. Using a novel technique, 2 RNS Systems (2 neurostimulators and 4 leads) were successfully implanted in a single patient with bilateral parietal epileptogenic zones. In patients with multiple epileptogenic zones, this technique allows for additional treatment options. Implantation can be done successfully, without telemetry interference, using proper surgical planning and neurostimulator positioning.Trajectories for the depth leads were planned using neuronavigation with CT and MR imaging. Stereotactic frames were used for coordinate targeting. Each neurostimulator was positioned with maximal spacing to avoid telemetry interference while minimizing patient discomfort. A separate J-shaped incision was used for each neurostimulator to allow for compartmentalization in case of infection. In order to minimize surgical time and risk of infection, the neurostimulators were implanted in 2 separate surgeries, approximately 3 weeks apart.The neurostimulators and leads were successfully implanted without adverse surgical outcomes. The patient recovered uneventfully, and the early therapy settings over several months resulted in preliminary decreases in aura and seizure frequency. Stimulation by one of the neurostimulators did not result in stimulation artifacts detected by the contralateral neurostimulator.
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http://dx.doi.org/10.3171/2018.8.JNS181362DOI Listing
January 2019

Long-Term Tumor Control Rates Following Gamma Knife Radiosurgery for Acoustic Neuroma.

World Neurosurg 2019 Feb 15;122:366-371. Epub 2018 Nov 15.

Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.

Background: Acoustic neuromas (ANs) are benign intracranial tumors that arise from myelin-forming Schwann cells surrounding the vestibular branch of the vestibulocochlear nerve (cranial nerve VIII). Treatment options for AN include observation, radiosurgery, and microsurgical resection. Gamma Knife radiosurgery (GKRS) for AN has well-documented short-term safety and efficacy for carefully selected patients. Recent innovations in GKRS technology may improve long-term outcomes. The aim of this study was to report long-term tumor control and complication rates after GKRS for sporadic AN.

Methods: A retrospective review was performed of patients with sporadic ANs at Keck Hospital of USC who underwent GKRS from 1995 to 2015 with a minimum follow-up of 12 months.

Results: Median age at treatment was 63.7 years (range, 19.4-84.2 years). Median follow-up time was 69 months. Median tumor diameter was 17.5 mm (range, 5.0-29.0 mm), and median treatment volume was 2.41 cm (range, 0.09-12.8 cm). Median prescribed dose was 12.50 Gy. Tumor control was achieved in 51 (98.1%) patients over the follow-up period (12-192 months). One patient experienced tumor progression at 22 months after GKRS, requiring surgical intervention, which ultimately resulted in remission. Complications included hearing loss (17.3%), worsened balance/ataxia (7.7%), and hydrocephalus (1.92%).

Conclusions: Patients undergoing GKRS for sporadic ANs had high rates of tumor control over a median follow-up time of >5 years. Improvements in radiosurgery treatment planning were seen in the most recent cohort of patients. GKRS is a safe and effective modality for treating sporadic ANs in selected patients.
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http://dx.doi.org/10.1016/j.wneu.2018.11.009DOI Listing
February 2019

Utilizing Light-field Imaging Technology in Neurosurgery.

Cureus 2018 Apr 10;10(4):e2459. Epub 2018 Apr 10.

Department of Neurosurgery, University of Southern California, Los Angeles, USA.

Traditional still cameras can only focus on a single plane for each image while rendering everything outside of that plane out of focus. However, new light-field imaging technology makes it possible to adjust the focus plane after an image has already been captured. This technology allows the viewer to interactively explore an image with objects and anatomy at varying depths and clearly focus on any feature of interest by selecting that location during post-capture viewing. These images with adjustable focus can serve as valuable educational tools for neurosurgical residents. We explore the utility of light-field cameras and review their strengths and limitations compared to other conventional types of imaging. The strength of light-field images is the adjustable focus, as opposed to the fixed-focus of traditional photography and video. A light-field image also is interactive by nature, as it requires the viewer to select the plane of focus and helps with visualizing the three-dimensional anatomy of an image. Limitations include the relatively low resolution of light-field images compared to traditional photography and video. Although light-field imaging is still in its infancy, there are several potential uses for the technology to complement traditional still photography and videography in neurosurgical education.
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http://dx.doi.org/10.7759/cureus.2459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5991932PMC
April 2018
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