Karleyton C. Evans
Harvard University
Internal medicinePathologyMagnetic resonance imagingPsychologyCerebral blood flowCardiologyNeuroscienceCerebral arteriesChemistryHypercapniapCO2Deep brain stimulationFunctional magnetic resonance imagingAir hungerBreathingAnesthesiaNuclear magnetic resonanceBrain mappingRespiratory systemAnxietyNeuroimagingMedicine
Publications 42
#1Suk-Tak Chan (Harvard University)H-Index: 21
#2Karleyton C. Evans (Harvard University)H-Index: 20
Last. Kenneth K. Kwong (Harvard University)H-Index: 70
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Background The origin of low frequency cerebral hemodynamic fluctuations (CHF) in the resting state remains unknown. Breath-by breath O2-CO2 exchange ratio (bER) has been reported to correlate with the cerebrovascular response to brief breath hold challenge at the frequency range of 0.008-0.03Hz in healthy adults. bER is defined as the ratio of the change in the partial pressure of oxygen (ΔPO2) to that of carbon dioxide (ΔPCO2) between end inspiration and end expiration. In this study, we aimed...
1 CitationsSource
#1Suk-Tak Chan (Harvard University)H-Index: 21
#2Karleyton C. Evans (Harvard University)H-Index: 20
Last. Kenneth K. Kwong (Harvard University)H-Index: 70
view all 9 authors...
BACKGROUND: Hypercapnia during breath holding is believed to be the dominant driver behind the modulation of cerebral blood flow (CBF). However, increasing evidence show that mild hypoxia and mild hypercapnia in breath hold (BH) could work synergistically to enhance CBF response. We hypothesized that breath-by-breath O2-CO2 exchange ratio (bER), defined as the ratio of the change in partial pressure of oxygen (DeltaPO2) to that of carbon dioxide (DeltaPCO2) between end inspiration and end expira...
7 CitationsSource
#1Karleyton C. EvansH-Index: 20
#2Tian-yue SongH-Index: 1
Last. Donald G. McLarenH-Index: 30
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#1Marta Bianciardi (Harvard University)H-Index: 25
#2Nicola Toschi (University of Rome Tor Vergata)H-Index: 37
Last. Lawrence L. Wald (Harvard University)H-Index: 83
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The influence of cardiac activity on the viscoelastic properties of intracranial tissue is one of the mechanisms through which brain–heart interactions take place, and is implicated in cerebrovascular disease. Cerebrovascular disease risk is not fully explained by current risk factors, including arterial compliance. Cerebrovascular compliance is currently estimated indirectly through Doppler sonography and magnetic resonance imaging (MRI) measures of blood velocity changes. In order to meet the ...
13 CitationsSource
#1Darin D. Dougherty (Harvard University)H-Index: 62
#2Tina Chou (Harvard University)H-Index: 5
Last. Thilo Deckersbach (Harvard University)H-Index: 67
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OBJECTIVE Deep brain stimulation (DBS) is a reversible, nonlesion-based treatment for patients with intractable obsessive-compulsive disorder (OCD). The first studies on DBS for OCD stimulating the ventral capsule/ventral striatum (VC/VS) yielded encouraging results for this neuroanatomical site's therapeutic efficacy. This investigation was conducted to better understand which regions of the cortico-striatal-thalamic-cortical network were acutely affected by VC/VS DBS for OCD. Furthermore, the ...
22 CitationsSource
#1Darin D. Dougherty (Harvard University)H-Index: 62
#2Ali R. Rezai (Cleveland Clinic)H-Index: 71
Last. Donald A. Malone (Cleveland Clinic)H-Index: 22
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Abstract Background Multiple open-label trials of deep brain stimulation (DBS) for treatment-resistant depression (TRD), including those targeting the ventral capsule/ventral striatum target, have shown encouraging response rates. However, no randomized controlled trials of DBS for TRD have been published. Methods Thirty patients with TRD participated in a sham-controlled trial of DBS at the ventral capsule/ventral striatum target for TRD. Patients were randomized to active versus sham DBS treat...
268 CitationsSource
#1Joan A. Camprodon (Harvard University)H-Index: 19
#2Navneet Kaur (Harvard University)H-Index: 4
Last. Darin D. Dougherty (Harvard University)H-Index: 62
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Background: Cognitive deficits are common across neuropsychiatric disorders, and a primary cause of functional disability. Nevertheless, clinicians have limited therapeutic options to facilitate cognitive enhancement, particularly of executive functions. We present results from a multicenter clinical trial of epidural cortical stimulation in patients with Major Depressive Disorder (MDD). The initial dose determination algorithm revealed acute dose-dependent facilitation of working memory functio...
1 CitationsSource
#1Louis Gagnon (MIT: Massachusetts Institute of Technology)H-Index: 24
#1Louis Gagnon (MIT: Massachusetts Institute of Technology)H-Index: 18
Last. David A. Boas (MIT: Massachusetts Institute of Technology)H-Index: 115
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The blood oxygenation level-dependent (BOLD) contrast is widely used in functional magnetic resonance imaging (fMRI) studies aimed at investigating neuronal activity. However, the BOLD signal reflects changes in blood volume and oxygenation rather than neuronal activity per se. Therefore, understanding the transformation of microscopic vascular behavior into macroscopic BOLD signals is at the foundation of physiologically informed noninvasive neuroimaging. Here, we use oxygen-sensitive two-photo...
137 CitationsSource
#1Suk-Tak ChanH-Index: 21
#2Karleyton C. Evans (Harvard University)H-Index: 20
Last. Kenneth K. KwongH-Index: 70
view all 5 authors...
AbstractPrimary objective: To use breath-hold functional magnetic resonance imaging (fMRI) to localize the brain regions with impaired cerebrovascular reactivity (CVR) in a female patient diagnosed with mild traumatic brain injury (mTBI). The extent of impaired CVR was evaluated 2 months after concussion. Follow-up scan was performed 1 year post-mTBI using the same breath-hold fMRI technique.Research design: Case report.Methods and procedures: fMRI blood oxygenation dependent level (BOLD) signal...
26 CitationsSource
#1Audrey P. FanH-Index: 19
#2Karleyton C. EvansH-Index: 20
Last. Elfar AdalsteinssonH-Index: 59
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1 Citations