SignificanceAssessment of pain and its clinical diagnosis rely on subjective methods which become even more complicated under analgesic drug administrations.AimWe aim to propose a deep learning (DL)–based transfer learning (TL) methodology for objective classification of functional near-infrared spectroscopy (fNIRS)–derived cortical oxygenated hemoglobin responses to painful and non-painful stimuli presented under different timings post-analgesic and placebo drug administration.ApproachA publicly available fNIRS dataset obtained during painful/non-painful stimuli was used. Separate fNIRS scans were taken under the same protocol before drug (morphine and placebo) administration and at three different timings (30, 60, and 90 min) post-administration. Data from pre-drug fNIRS scans were utilized for constructing a base DL model. Knowledge generated from the pre-drug model was transferred to six distinct post-drug conditions by following a TL approach. The DeepSHAP method was utilized to unveil the contribution weights of nine regions of interest for each of the pre-drug and post-drug decoding models.ResultsAccuracy, sensitivity, specificity, and area under curve (AUC) metrics of the pre-drug model were above 90%, whereas each of the post-drug models demonstrated a performance above 90% for the same metrics. Post-placebo models had higher decoding accuracy than post-morphine models. Knowledge obtained from a pre-drug base model could be successfully utilized to build pain decoding models for six distinct brain states that were scanned at three different timings after either analgesic or placebo drug administration. The contribution of different cortical regions to classification performance varied across the post-drug models.ConclusionsThe proposed DL-based TL methodology may remove the necessity to build DL models for data collected at clinical or daily life conditions for which obtaining training data is not practical or building a new decoding model will have a computational cost. Unveiling the explanation power of different cortical regions may aid the design of more computationally efficient fNIRS-based brain–computer interface (BCI) system designs that target other application areas.
Intracranial pressure (ICP) is a critical biomarker measured invasively with the risk of complications. There is a need for non-invasive methods to estimate ICP. Diffuse correlation spectroscopy (DCS) allows the non-invasive measurement of pulsatile, microvascular cerebral blood flow which contains information about ICP. Recently, our proof-of-concept study used machine-learning to deduce ICP from DCS signals to estimate ICP resulting in excellent linearity and a reasonable accuracy (±4 mmHg). Here, we extend to a multi-center (three centers) data set of adults with acute brain injury (N=34). We will present the results from the complete data set as new data flows in.
Using functional near-infrared spectroscopy (fNIRS), modulation of hemodynamic responses by transcutaneous electrical nerve stimulation (TENS) during delivery of nociceptive stimulation was investigated in fibromyalgia (FM) patients and healthy controls for both hands. Two experiments were conducted: (1) median nerve stimulation with TENS and (2) painful stimulation using electronic von Frey filaments with TENS/placebo TENS. Mean ΔHbO2 brain activity was compared across groups and conditions using factorial ANOVA. Dominant (right) hand stimulation indicated significant interactions between group and condition in both hemispheres. Post hoc results revealed that FM patients showed an increased activation in “pain + TENS” condition compared to the “pain + placebo TENS” condition while the brain activity patterns for these conditions in controls were reversed. Left-hand stimulation resulted in similar TENS effects (reduced activation for “pain + TENS” than “pain + placebo TENS”) in both groups. TENS effects in FM patients might be manipulated by the stimulation side. While the nondominant hand was responsive to TENS treatment, the dominant hand was not. These results indicate that stimulation side might be an effective factor in FM treatment by using TENS. Future studies are needed to clarify the underlying mechanism for these findings.
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