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Todd Parrish

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13 papers
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13

YNIMG Journal 2022 Journal Article

Modulation of brain networks during MR-compatible transcranial direct current stimulation

  • Amber M. Leaver
  • Sara Gonzalez
  • Megha Vasavada
  • Antoni Kubicki
  • Mayank Jog
  • Danny J.J. Wang
  • Roger P. Woods
  • Randall Espinoza

Transcranial direct current stimulation (tDCS) can influence performance on behavioral tasks and improve symptoms of brain conditions. Yet, it remains unclear precisely how tDCS affects brain function and connectivity. Here, we measured changes in functional connectivity (FC) metrics in blood-oxygenation-level-dependent (BOLD) fMRI data acquired during MR-compatible tDCS in a whole-brain analysis with corrections for false discovery rate. Volunteers (n = 64) received active tDCS, sham tDCS, and rest (no stimulation), using one of three previously established electrode tDCS montages targeting left dorsolateral prefrontal cortex (DLPFC, n = 37), lateral temporoparietal area (LTA, n = 16), or superior temporal cortex (STC, n = 11). In brain networks where simulated E field was highest in each montage, connectivity with remote nodes decreased during active tDCS. During active DLPFC-tDCS, connectivity decreased between a fronto-parietal network and subgenual ACC, while during LTA-tDCS connectivity decreased between an auditory-somatomotor network and frontal operculum. Active DLPFC-tDCS was also associated with increased connectivity within an orbitofrontal network overlapping subgenual ACC. Irrespective of montage, FC metrics increased in sensorimotor and attention regions during both active and sham tDCS, which may reflect the cognitive-perceptual demands of tDCS. Taken together, these results indicate that tDCS may have both intended and unintended effects on ongoing brain activity, stressing the importance of including sham, stimulation-absent, and active comparators in basic science and clinical trials of tDCS.

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YNIMG Journal 2016 Journal Article

The Northwestern University Neuroimaging Data Archive (NUNDA)

  • Kathryn Alpert
  • Alexandr Kogan
  • Todd Parrish
  • Daniel Marcus
  • Lei Wang

The Northwestern University Neuroimaging Data Archive (NUNDA), an XNAT-powered data archiving system, aims to facilitate secure data storage; centralized data management; automated, standardized data processing; and simple, intuitive data sharing. NUNDA is a federated data archive, wherein individual project owners regulate access to their data. NUNDA supports multiple methods of data import, enabling data collection in a central repository. Data in NUNDA are available by project to any authorized user, allowing coordinated data management and review across sites. With NUNDA pipelines, users capitalize on existing procedures or standardize custom routines for consistent, automated data processing. NUNDA can be integrated with other research databases to simplify data exploration and discovery. And data on NUNDA can be confidently shared for secure collaboration.

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YNIMG Journal 2013 Journal Article

Neuroimaging in aphasia treatment research: Consensus and practical guidelines for data analysis

  • Marcus Meinzer
  • Pélagie M. Beeson
  • Stefano Cappa
  • Jenny Crinion
  • Swathi Kiran
  • Dorothee Saur
  • Todd Parrish
  • Bruce Crosson

Functional magnetic resonance imaging is the most widely used imaging technique to study treatment-induced recovery in post-stroke aphasia. The longitudinal design of such studies adds to the challenges researchers face when studying patient populations with brain damage in cross-sectional settings. The present review focuses on issues specifically relevant to neuroimaging data analysis in aphasia treatment research identified in discussions among international researchers at the Neuroimaging in Aphasia Treatment Research Workshop held at Northwestern University (Evanston, Illinois, USA). In particular, we aim to provide the reader with a critical review of unique problems related to the pre-processing, statistical modeling and interpretation of such data sets. Despite the fact that data analysis procedures critically depend on specific design features of a given study, we aim to discuss and communicate a basic set of practical guidelines that should be applicable to a wide range of studies and useful as a reference for researchers pursuing this line of research.

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YNIMG Journal 2010 Journal Article

Identification of critical areas for motor function recovery in chronic stroke subjects using voxel-based lesion symptom mapping

  • Ryan Lo
  • Darren Gitelman
  • Robert Levy
  • Justin Hulvershorn
  • Todd Parrish

Introduction Previous stroke studies using fMRI or lesion characterization methods to study the preservation of motor performance have been limited in defining anatomical structure critical for functional performance. This study attempts to overcome this limitation by using voxel-based lesion symptom mapping (VLSM) to identify specific anatomical regions required for preservation of motor function. Methods Forty-one moderate to moderately severe stroke subjects (upper extremity Fugl-Meyer between 28 and 50, Arm Motor Ability Test >35) were imaged with a 1 mm isotropic T1-weighted volumetric sequence, and their motor performance was assessed. The T1 volume images were normalized to a symmetric template using SPM5 and oriented so the lesion appeared in the left hemisphere. The lesioned areas were manually segmented on the normalized T1 image. All 3D lesion maps were entered into the VLSM analysis. Areas showing significant correlations with functional performance measures were identified using the false discovery rate corrected at p≤0. 05. Results The areas most correlated with a decrease in motor performance were at the junction of the corona radiata leading into the corticospinal tract. The Arm Motor Ability Test scores produced the most significant results, while the other measures showed similar anatomical patterns. Conclusion The use of lesion symptom mapping in conjunction with behavioral measures produced anatomically specific results demonstrating that the area leading from the corticospinal tract to cortical motor areas is critical for maintaining hand motor performance after a stroke. This area may represent the joining of parallel redundant tracts that, when damaged, limit recovery potential.

Details DOI
v2026.09.13