Research
Measuring brain physiology in critical illness
Neurologic function changes over time, but much of our conventional assessment captures only brief snapshots. This becomes particularly important in the ICU, where sedation and impaired consciousness can make the clinical examination incomplete or difficult to interpret.
My research focuses on physiologic measurements that can help fill those gaps. I am particularly interested in combining continuous EEG with measurements of cerebral blood flow, oxygenation, and autoregulation to understand how electrical activity, perfusion, and metabolism change during acute brain injury.
The goal is not simply to collect more signals. It is to determine what those signals actually measure, how they relate to one another, and when they provide information that changes our understanding of a patient's neurologic state.
Research questions
Multimodal neuromonitoring
No single monitor provides a complete description of cerebral physiology. I am interested in combining measurements that reflect different aspects of brain function—particularly electrical activity, blood flow, oxygenation, and autoregulation—and determining when changes across those signals represent meaningful changes in the underlying physiology.
Quantitative EEG
Continuous EEG records electrical activity over time, but the resulting data are dense and influenced by many clinical factors. I am interested in how quantitative EEG measures summarize that activity, how they relate to cerebral blood flow, and what changes can be interpreted in critically ill patients.
Diffuse optical monitoring
Near-infrared spectroscopy and diffuse correlation spectroscopy provide complementary measurements of cerebral oxygenation and blood flow. My interest is in what those measurements represent physiologically and how they can be interpreted alongside EEG and other bedside data.
Acute brain injury
Brain injury after cardiac arrest and during ECMO evolves over time. I am interested in how changes in autoregulation, perfusion, and inflammation can be measured and how they relate to neurologic injury and recovery.
Methods
Methods and measurements
My background in physics, biomedical engineering, and medical imaging shapes how I approach these questions: by asking what each measurement represents, how it is produced, and how it can be compared with other observations.
- Continuous EEG
- Optical monitoring
- Neuroimaging
- Data analysis
Peer-reviewed work
Publications
Selected bibliography from the academic curriculum vitae.
- 2025Angulo SL*, Johnson TW*, Hutchinson L, et al.
Inflammation and neurological outcomes in cardiac arrest: narrative review of serum biomarkers.
J Intensive Care Med. · *Equal authorship - 2024Dar IA, Khan IR, Johnson TW, et al.
Wavelet- and time-domain cerebral autoregulation using diffuse correlation spectroscopy in ECMO patients.
PLoS ONE, 19(10) - 2024Khan IR, Dar IA, Johnson TW, et al.
qEEG–cortical blood flow correlations in ECMO patients with and without encephalopathy.
J Clin Neurophysiol, 41(7):597–605 - 2022Johnson TW, Dar I, Donohue KL, et al.
Cerebral blood flow hemispheric asymmetry in comatose ECMO patients.
Front Neurosci, 16:858404 - 2020Hashem M, Zhang Q, Wu Y, Johnson TW, Dunn JF.
Multimodal NIRS-MRI quantification of gray matter CMRO₂: hypothermia validation.
NeuroImage, 206:116315 - 2016Johnson TW, Wu Y, Nathoo N, Rogers JA, Yong VW, Dunn JF.
Gray matter hypoxia in EAE: a model of multiple sclerosis.
PLoS ONE, 11(12):e0167196 - 2013Robillard JM, Johnson TW, Hennessey C, Beatty BL, Illes J.
Health information about dementia on Twitter ("Aging 2.0").
PLoS ONE, 8(7) - 2013Robillard JM, Whiteley L, Johnson TW, et al.
Social media, information-seeking, and ethics in gene therapy.
J Med Internet Res, 15(3) - 2010Dougherty SM, Clark JS, Negueruela I, Johnson T, Chapman JM.
Radio emission from massive stars in Westerlund-1.
Astron Astrophys, 511:645–660
Book chapter
Diffuse optical monitoring
Johnson TW, Francoeur C, Ko T, Kirschen M, Khan IR. Diffuse Optical Imaging for Cerebral Oxygenation, Perfusion, and Metabolism Monitoring. In preparation.