About

Roy Hoshi Hamilton, MD, MS, FAAN, FANA, is a Professor of Neurology at the University of Pennsylvania and serves as the Director of the Laboratory for Cognition and Neural Stimulation at the same institution. He is also the Director of the Brain Stimulation, Translation, Innovation, and Modulation (brainSTIM) Center. His research focuses on the characteristics and limits of functional neuroplasticity in the adult human brain, investigating how the brain reorganizes itself in response to injury and exploring ways to enhance this reorganization to accelerate rehabilitation through noninvasive electrical or magnetic brain stimulation. Additionally, Hamilton studies the use of noninvasive brain stimulation to elucidate and improve mechanisms of cognition in healthy individuals, considering the biological, social, and ethical implications of neural enhancement. Clinically, he principally treats patients suffering from dementia and evaluates and manages patients with cognitive deficits following stroke. He is deeply involved in issues related to diversity in medicine, inclusion, and health equity, holding roles such as Assistant Dean for Diversity and Inclusion at the Perelman School of Medicine and Vice Chair for Diversity and Inclusion in the Department of Neurology at the University of Pennsylvania.

Research topics

• Medicine
• Psychiatry
• Political Science
• Environmental health
• Internal medicine
• Gerontology
• Family medicine
• Demography
• Pathology
• Intensive care medicine

Selected publications

• Noninvasive Brain Stimulation in Translational Cognitive Neuroscience—Applications in Aphasia and Beyond

  Neurology · 2026-01-30

  articleOpen access1st authorCorresponding

  Noninvasive brain stimulation (NIBS) has emerged as a transformative tool in both cognitive neuroscience research and the treatment of a growing range of neuropsychiatric conditions. This commentary, based on the 2025 H. Houston Merritt Lecture, explores how NIBS can be applied within a translational cognitive neuroscience framework that bridges theoretical models of cognitive function with targeted neural interventions. Drawing on over 15 years of research, the major focus of this piece is on the use of transcranial magnetic stimulation (TMS) to characterize and enhance language function in persons with aphasia (PWA). A significant body of work has examined the role of the right hemisphere, particularly the right pars triangularis, which may exert a maladaptive influence within reorganized language networks in many PWA. Inhibitory TMS targeting this region has been shown to produce both transient and sustained improvements in language performance. Key predictors of response to TMS include the characteristics of participants' language deficits and genetic differences that influence neuroplasticity. Network neuroscience approaches can also enhance predictive accuracy by revealing how individual variations in brain structure influence stimulation outcomes. While TMS remains the most extensively studied NIBS modality, transcranial electrical stimulation is gaining momentum, with promising results in both poststroke and primary progressive aphasia. Emerging modalities such as focused ultrasound and transcranial temporal interference stimulation are also on the rise as tools for enhancing brain performance. However, the expanding use of NIBS also raises ethical considerations that must be addressed to ensure its equitable and responsible deployment. Ultimately, NIBS represents a powerful convergence of neuroscience and technology, offering renewed hope for restoring cognitive function in individuals affected by neurologic disease.

  PublisherOA PDFDOI

• Advancing Brain Stimulation to First-Line Psychiatric Therapy: Wearable Disposable Electrotherapy

  American Journal of Psychiatry · 2026-03-04

  article
  PublisherDOI

• Upregulating action semantics with neuromodulation and gesture observation to facilitate verb retrieval in aphasia

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-04-10

  articleOpen accessSenior author

  Although many individuals with chronic aphasia respond to language therapy, there remains a need for adjunctive interventions that can enhance treatment response. Approaches targeting multiple modalities, such as gesture cueing, and neuromodulation techniques, such as transcranial magnetic stimulation, have shown promise for supporting language recovery. The present pilot study investigated whether enhancing activation of the action semantic network could facilitate verb production in individuals with chronic aphasia. Participants were recruited as a convenience sample and completed a within-subject design in which all individuals received each condition. Two non-linguistic methods of activating the action semantic network were evaluated: (1) pantomimed gesture cues to prime action concepts and (2) intermittent theta-burst stimulation to the left posterior middle temporal gyrus (pMTG), an intact action-semantic network node in our participants. We examined individual and combined effects of gesture priming and stimulation to test whether a combined approach would yield additive or interactive benefits. Using a Bayesian generalized linear mixed-effects model, we observed a moderate interaction between gesture priming and stimulation site. Contrary to predictions, combining gesture priming with pMTG stimulation did not produce additional benefits over either intervention alone. Instead, pMTG stimulation attenuated the priming advantage observed under vertex stimulation, and gesture priming attenuated the advantage observed with pMTG stimulation alone. Posterior estimates provided substantial preliminary evidence for this interaction in our pilot sample size. These findings suggest that combined activation of the action semantic network through gesture and neuromodulation approaches may not benefit verb retrieval above and beyond each approach alone.

  PublisherOA PDFDOI

• Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines (2017-2025: An update) - endorsed by the European Society for Brain Stimulation (ESBS) and by the International Federation for Clinical Neurophysiology (IFCN).

  UNC Libraries · 2026-04-10

  articleOpen access

  This guideline summarizes updated safety data (2017-2025) and provides expert recommendations on the use of low intensity transcranial electrical stimulation (tES) in humans. tES encompasses several techniques including transcranial direct current stimulation (tDCS), oscillatory transcranial direct current stimulation (otDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS), transcranial temporal interference stimulation (tTIS), and their combinations or variations. Across over 300,000 sessions involving healthy individuals, patients with neuropsychiatric conditions, and other clinical populations, no tES-related serious adverse events (AEs) have been reported. Moderate AEs are rare and limited to a small range of specific applications. Mild AEs are common and include transient symptoms such as localized sensations (e.g., tingling or burning), headaches, and fatigue. Similar mild AEs are also reported by individuals receiving placebo stimulation. The frequency, magnitude, and type of AEs are comparable across healthy, clinical, and vulnerable groups, including children, elderly, or pregnant women. Combined interventions (e.g., co-application with EEG, TMS, or neuroimaging) have not shown increased safety risks. Safety is well-established for both bipolar and multichannel tES when applied up to 4 mA and up to 60 min per day. Higher intensities and longer stimulation durations may also be safe. Nevertheless, the number of studies using intensities above 4 mA or stimulating longer than 60 min is low. Home-based use of treatments is growing rapidly, leveraging remote supervision to provide patients with greater access and enable repeated, sustained dosing paradigms. We recommend using screening and AE questionnaires in future controlled studies, in particular when planning to extend the stimulation parameters applied. We discuss recent regulatory and ethical issues.

  PublisherDOI

• Predicting Post-Stroke Aphasia Speech Performance from Multimodal Data with Explainable Machine Learning

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-05

  articleOpen accessSenior authorCorresponding

  Aphasia, an acquired language deficit, is the most common post-stroke focal cognitive impairment, and roughly 60% cases become chronic (duration >6 months). Aphasia therapies could be optimized if clinicians could make personalized predictions of how individual persons with aphasia (PWA) would be likely to perform on particular language tasks. However, current approaches relying on imaging, lesion volume, patient demographics, and clinical scores achieve less than 50% accuracy in predicting performance in PWA. Research algorithms using complex imaging and fMRI can make binary predictions about the presence or absence of aphasia but do not give more clinically relevant information. We aim to predict word-by-word speech accuracy in PWA to better enable personalized speech therapies. To be clinically informative, machine learning models developed for this purpose should use clinically available inputs, explain key features behind a prediction, and generalize to new PWA and previously unseen words. This study combines multimodal input features from clinical testing scores and structural MRI neuroimaging with a novel data source: word-by-word linguistic difficulty. We computed metrics of cognitive burden, such as semantic selection and recall demands, and articulatory burden, such as word length in phonemes and syllables, using naturalistic corpora containing over a billion words of English text. Retrospective training, ten-fold cross validation and 500-run bootstrapping of different machine learning models with various combinations of input features was conducted using 4620 trials. A simplified version of the best model using widely available inputs was deployed clinically through a web app, and prospective generalization was tested on 570 trials with unseen words and different naming tasks in new PWA. We found the best performances with random forest classifiers using linguistic difficulty combined with either clinical information (AUROC ± SEM = 0.87 ± 0.07), or all together with structural imaging connectivity (0.90 ± 0.04). Classifiers using multimodal inputs significantly outperformed others employing single inputs (range 0.66-0.85, p<0.05). Extracting feature importances from the best model showed that Western Aphasia Battery scores, semantic demands, number of phonemes, and syllables were predictive of PWA speech accuracy. Structural integrity in peri-lesional brain regions predicted better language performance whereas higher connectivity of select contralateral homotopes contributed to prediction of worse speech. Without the inclusion of MRI data, lesion volume was a key predictor of PWA speech as well. A simplified, clinically ready, explainable model (publicly available as AphasiaLENS web application) predicted PWA accuracy for any user-entered word, not restricted to a standardized battery. Its prospective generalization performance was not significantly different from the best model using full inputs (AUROC ranges 0.81-0.89, p>0.05 ). Thus, our research can help inform individualized treatment planning for PWA, while also suggesting research targets through better understanding of brain-behavior relationships.

  PublisherOA PDFDOI

• Report Approval for Transcranial Electrical Stimulation (RATES): expert recommendation based on a Delphi consensus study

  Nature Protocols · 2025-10-03 · 10 citations

  reviewOpen access
  PublisherOA PDFDOI

• Advancing Disability Equity in Neurology

  Neurology · 2025-07-02 · 3 citations

  article
  PublisherDOI

• Tuning the Brain for Language: Exploring tACS as a Language Enhancement Tool (P6-4.006)

  Neurology · 2025-04-07

  article

  To determine the efficacy of a noninvasive neuromodulation technique, called transcranial alternating current stimulation (tACS), in facilitating language abilities.

  PublisherDOI

• Lesion-Induced Changes to the Network Controllability of the Right Pars Triangularis in Aphasia

  Neurobiology of Language · 2025-01-01 · 1 citations

  articleOpen access

  Left hemisphere stroke causes functional changes to the language network and may shift aspects of language processing to right hemisphere homotopes of perisylvian language regions. The result of right hemisphere recruitment is unclear. Studies suggest the right pars triangularis (rPTr) engagement in language processing corresponds to higher dysfunction. As a result, the region is a site for inhibitory neuromodulation, with evidence that inhibiting the region improves language function in persons with aphasia (PWA). However, studies have also found no relationship between rPTr functional activity and language performance in PWA. The mixed evidence regarding the rPTr suggests additional work is needed to understand the role of the region in PWA. We propose that the white matter connections that support communication between regions may be an important mediator. Thus, we sought to investigate if left hemisphere stroke leads to changes in the structural topological properties of the region. We used measures from network control theory (NCT) to compare the theoretical capacity of the rPTr to integrate communication across brain modules (i.e., boundary controllability [BC]) in the brain, in 60 PWA and 62 controls. We also examined whether BC corresponded to different aspects of language processing (i.e., semantic and phonological) in PWA. We found that PWA had a higher BC in the rPTr relative to controls. Higher BC was associated with fewer phonological errors in a picture naming task. These findings suggest that left hemisphere stroke causes shifts in the structural role of right hemisphere regions that relate to language processing in PWA.

  PublisherOA PDFDOI

• Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines (2017–2025: An update) – endorsed by the European Society for Brain Stimulation (ESBS) and by the International Federation for Clinical Neurophysiology (IFCN)

  Clinical Neurophysiology · 2025-11-23 · 14 citations

  articleOpen access
  PublisherOA PDFDOI

Recent grants

• Treating primary progressive aphasia and elucidating neurodegeneration in the language network using transcranial direct current stimulation

  NIH · $3.7M · 2019–2025

• NIH Grant R01DC012780

  NIH · $1.8M · 2019

• NIH Grant K01NS060995

  NIH · $802k · 2014

Frequent coauthors

• Rodney Leacock

  University of Rochester

  267 shared

• Erika Marulanda-Londoño

  University of Miami

  242 shared

• Nimish Mohile

  University of Rochester Medical Center

  162 shared

• Andrew R. Spector

  146 shared

• Cumara B. O’Carroll

  Mayo Clinic in Arizona

  146 shared

• Charles Flippen

  University of Rochester

  146 shared

• Reena Thomas

  Stanford University

  146 shared

• Richard Young

  Whitehead Institute for Biomedical Research

  121 shared

Labs

• Laboratory for Cognition and Neural StimulationPI

Awards & honors

• FAAN (Fellow of the American Academy of Neurology)
• FANA (Fellow of the American Neurological Association)