Biology subjects

Mickelsen, S.

Publications and source records attributed to Mickelsen, S..

2 recordsLinked to original sources

bioRxiv2024

Quantification of thermal side effects during pulsed field ablation

Background and AimsPulsed field ablation (PFA) has been described as non-thermal, but abundant data exist in oncology applications, and growing data are emerging in cardiology, highlighting that thermal effects are in fact present with PFA. Our objective was to develop a reliable model of the thermal effects arising from PFA of myocardial and esophageal tissue over a range of typical peak voltage operating conditions. MethodsWe developed a three-dimensional computer model of the left atrium that can quantify the thermal effects from PFA applications. Energy was applied using a bipolar configuration, and far-field and symmetry boundaries were set as electrically insulating. The model utilizes a monophasic waveform with a pulse width of 100 s and gap between pulses of 1 s was applied for a total of 50 pulses in a single train, with variations to this easily implemented to accommodate various conditions. ResultsOver a range of peak voltage operating conditions (1 kV, 1.5 kV, and 2 kV), minimal temperature rise in the esophagus was seen with 1 kV pulses (corresponding to 215 J input), but with 1.5 kV and 2 kV peak voltages (corresponding to 570 J and 1.23 kJ), temperature elevations reaching 46.3{degrees}C and > 62 {degrees}C were seen, respectively. These elevations occurred after only a single pulse train of 50 pulses, implying that further elevations in temperature would be seen with subsequent applications. These findings concur with data published in other fields of medicine where pulsed field treatments are utilized. ConclusionsThermal effects from PFA occur and can be quantified with in-silico modeling. The model described here offers an efficient means of determining temperature effects from PFA over various operating conditions. Energy levels used clinically appear to have the potential to induce collateral thermal injury with repeated applications of pulsed field energy.

bioengineering↗

bioRxiv2020

The Neuroanatomy of Speech Processing: A Large-Scale Lesion Study

The neural basis of language has been studied for centuries, yet the networks critically involved in simply identifying or understanding a spoken word remain elusive. Several functional-anatomical models of critical neural substrates of receptive speech have been proposed, including (1) auditory-related regions in the left mid-posterior superior temporal lobe, (2) motor-related regions in the left frontal lobe (in normal and/or noisy conditions), the left anterior superior temporal lobe, or (4) bilateral mid-posterior superior temporal areas. One difficulty in comparing these models is that they often focus on different aspects of the sound-to-meaning pathway and are supported by different types of stimuli and tasks. Two auditory tasks that are typically used in separate studies--syllable discrimination and word comprehension--often yield different conclusions. We assessed syllable discrimination (words and nonwords) and word comprehension (clear speech and with a noise masker) in 158 individuals with focal brain damage: left (n=113) or right (n=19) hemisphere stroke, left (n=18) or right (n=8) anterior temporal lobectomy, and 26 neurologically-intact controls. Discrimination and comprehension tasks are doubly dissociable both behaviorally and neurologically. In support of a bilateral model, clear speech comprehension was near ceiling in 95% of left stroke cases and right temporal damage impaired syllable discrimination. Lesion-symptom mapping analyses for the syllable discrimination and noisy word comprehension tasks each implicated most of the left superior temporal gyrus (STG). Comprehension but not discrimination tasks also implicated the left pMTG, while discrimination but not comprehension tasks also implicated more dorsal sensorimotor regions in posterior perisylvian cortex.

neuroscience↗