Significance: Major depressive disorder (MDD) affects over 40 million U.S. adults in their lifetime. Transcranial photobiomodulation (t-PBM) has been shown to be effective in treating MDD, but the current treatment dosage does not account for head and brain anatomical changes due to aging. Aim: We study effective t-PBM dosage and its variations across age groups using state-of-the-art Monte Carlo simulations and age-dependent brain atlases ranging between 5 and 85 years of age. Approach: Age-dependent brain models are derived from 18 MRI brain atlases. Two extracranial source positions, F3-F4 and Fp1-Fpz-Fp2 in the EEG 10-20 system, are simulated at five selected wavelengths and energy depositions at two MDD-relevant cortical regions-dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC)-are quantified. Results: An overall decrease of energy deposition was found with increasing age. A strong negative correlation between the thickness of extracerebral tissues (ECT) and energy deposition was observed, suggesting that increasing ECT thickness over age is primarily responsible for reduced energy delivery. The F3-F4 position appears to be more efficient in reaching dlPFC compared to treating vmPFC via the Fp1-Fpz-Fp2 position. Conclusions: Quantitative simulations revealed age-dependent light delivery across the lifespan of human brains, suggesting the need for personalized and age-adaptive t-PBM treatment planning.
We compared previously carbon/salt/adhesive (CSA) electrodes with Ag/AgCl electrodes for surface electromyography (sEMG) signals collection. We found no differences in amplitude, but CSA electrodes exhibited a significantly better response to noise and motion artifacts. However, the carbon component may not be needed, and the salt/adhesive (SA) mixture might be as good as CSA for such a task. Either CSA or SA mixtures have the potential to provide the unique advantages of having longer (theoretically infinite) shelf life and potentially lower cost, compared to the gold standard Ag/AgCl hydrogel electrodes. In order to determine if carbon contribution is necessary for effective sEMG measuring capabilities the mixture, the functionality of SA electrodes utilizing different levels of salt concentration were compared to the capabilities of CSA electrodes. The levels consisted of 10%, 15%, and 25% salt concentration. Six subjects have been recruited so far to collect simultaneous recordings of sEMG signals using CSA and SA electrodes, side-by-side on triceps brachii, tibial anterior muscles, biceps brachii and quadriceps femoris. For all three levels of salt concentration in the SA electrodes, high correlation was found to the CSA electrodes on the estimated linear envelopes, RMS envelope and power spectrum density. Furthermore, no significant differences in amplitude, compared to CSA electrodes, were found for the three concentrations. Based on signal-to-noise and signal-to-motion measures on the preliminary data set, it seems like adding carbon to the mixture improves the response to motion, but impairs the noise corruption of the sEMG signals.
We performed 3-D Monte Carlo simulations to investigate the light dosage of transcranial photobiomodulation (t-PBM) across lifespan. An overall decrease in energy deposition was found as a result of increasing thicknesses of the extra-cerebral tissues.
Significance: Major depressive disorder (MDD) affects over 40 million US adults in their lifetimes. Transcranial photobiomodulation (t-PBM) has been shown to be effective in treating MDD, but the current treatment dosage does not account for anatomical head and brain changes due to aging.
Aim:We study effective t-PBM dosage and its variations across age groups using state-of-the-art Monte Caxrlo (MC) simulations and age-dependent brain atlases ranging between 5 to 85 years of age.Approach: Age-dependent brain models are derived from 18 MRI brain atlases. Two extracranial source positions, F3-F4 and Fp1-Fpz-Fp2 in the EEG 10-20 system, are simulated at five selected wavelengths and energy depositions at two MDD-relevant cortical regions -dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC) -are quantified.Results: An overall decrease of energy deposition was found with increasing age. A strong negative correlation between the thickness of extra-cerebral tissues (ECT) and energy deposition, suggesting that increasing ECT thickness over age is primarily responsible for reduced energy delivery. The F3-F4 position appears to be more efficient in reaching dlPFC compared to treating vmPFC via the Fp1-Fpz-Fp2 position.Conclusion: Quantitative simulations revealed age-dependent light delivery across the lifespan of human brains, suggesting the needs for personalized and age-adaptive t-PBM treatment planning.
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