Functional and Structural Optical Brain Imaging

Eunice Kennedy Shriver National Institute Of Child Health & Human Development

Investigators

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Abstract

Functional near infrared spectroscopy (fNIRS) is used to study brain activity in 2 areas:1) developmental trajectories of cognitive abilities in children and 2) validity of fNIRS using cognitive tasks previously evaluated using fMRI. Under the developmental studies, we have continued the collaboration with Dr.Thurm (NIMH) and Dr. Fox (UMD), on the mirror neuron network (MNN) in infants. MNN is associated with the development of sophisticated social behaviors that emerge in typical human infants. We have finished data collection in adult pilot subjects (N=40) who underwent a motor observation and execution paradigm while their brain activity measured through EEG/fNIRS simultaneously. MNN activation has already been associated with Mu suppression using EEG. By using EEG (with high temporal resolution) in conjunction with fNIRS will provide a more precise spatial resolution of neural activity based on hemodynamic activation to investigate the MNN. We conducted a review on the current fNIRS literature examining the action-observation network. The purpose of the review was to assess and critique the methodological and analytic approaches that have been used to study the action-observation network in healthy adults using fNIRS. we have also examined the feasibility of fNIRS for the study of MNS (also referred to action-observation network- AON) in a subsample of 30 subjects. Overall, our results indicated that the parietal regions, including bilateral superior parietal lobule (SPL), bilateral inferior parietal lobule (IPL), right supra-marginal region (SMG) and right angular gyrus (AG) are candidate regions of the human AON. Moreover, we demonstrated that the paradigm is sensitive to differences in subclinical levels of autistic traits, which can be used in future studies with clinical populations who present deficits in action understanding and action representation, namely autism spectrum disorders (ASD). This work has been published in Plos One journal in August 2021(Miguel et al., 2021). Additional analysis is being conducted using a connectivity approach. Results from this approach was published in the journal of Brain Science (Nguyen et al., 2021).. Our results showed that during the action execution, while a participant was performing an action with the right hand several region-to-region connections within the left hemisphere were related (connections within the left precentral, left postcentral, left inferior parietal and be-tween the left supramarginal and left angular regions). Furthermore, to fully characterize the MNN network using concurrent signals (EEG and fNIRS) we are conducting multimodal multiset data-fusion analysis with the goal of benefitting from each neuroimaging modalities strength, i.e. good temporal resolution of EEG and more focal resolution of fNIRS. We applied structured sparse multiset CCA (ssmCCA) model to our integrated dataset which resulted in finding similar activity patterns during action execution/observation across regions of interest indicating higher brain activity in regions in the left hemisphere (paracentral region, precentral region, and parietal inferior and superior regions) while subjects were executing a motor action. This is the first report that fused distinct brain metrics (hemodynamic response function and electrical activity) to characterize the MNN in the human brain and pinpoints left inferior parietal region is the dominant activated brain area in both action execution and action observation. For the observation condition also higher brain activity was also found in left regions of the brain, namely the postcentral, paracentral, precentral, and parietal superior and inferior regions. This work has been published in Scientific Reports journal (Dashtestani et al., 2022). After investigating brain activity patterns during action execution and action observation, we incorporate imagination condition in relation to action execution and action observation. Since we had implemented action imagination into our paradigm, this condition has also been analyzed using our established ssmCCA method. The importance of adding such condition lies in the belief that motor cognitive abilities depending on and achieved by the mechanism of mental rehearsal and re-enactment of action execution. Here, we also found left parietal inferior region is the main contributing area across imagination condition. Other brain regions activating during motor imagery task were located at the left hemisphere and were similar to the brain regions in both execution and observation conditions while their activity levels differ across each condition. Although there is not extensive literature on action imagination, the result of our work was in line with other studies. Our findings back up the idea that action observation or action imagination excites the same sensory-motor cortical network which supports execution of that same action. One plausible reason for such similarities between brain activities across those three conditions has been attributed to internal practice of an action. These results have been extensively discussed in a manuscript that we have prepared and planned to submit for publication by October 2022. We have continued the collaboration with Dr. Andrea Gropman at Childrens National Medical Center examining developmental deficits in children with Urea Cycle Disorders (UCD), especifically Ornithine transcarbamylase deficiency (OTCD) characterized by presence of hyperammonia (HA). Using fNIRS we examined the hemodynamics of PFC in OTCD population and fraternal twin with and without OTCD. Results revealed a distinction in left PFC activation between controls and patients with OTCD, where controls showed higher task related activation increase while performing the Stroop task. Subjects with OTCD also exhibited bilateral increase in PFC activation. We quantified the hemodynamic variations in total-hemoglobin, while twins performed the N-Back Working Memory task. Our preliminary results showed that the sibling with OTCD had higher variations in a very low frequency band (<0.03 Hz, related to mechanism of cerebral autoregulation) compared to the control sibling, possibly due to effect of HA. Functional connectivity (FC) analysis also revealed lower interhemispheric FC in an OTCD sibling as the task load increased. Next study involves simultaneous collection fNIRS of the prefrontal cortex and high frequency heart rate variability (HF-HRV); as derived from EKG to examine the connection between prefrontal activation and parasympathetic nervous system activity (as measured HF-HRV) during a behavioral flexibility task (the go/no-go task). The relationship between these measures has been previously described by the neurovisceral integration model; however, no study to date had examined these measures simultaneously. These data were collected in 38 healthy adult controls at rest and during the go/no-go task.. Results indicated that at rest, HF-HRV was negatively related to prefrontal activation, consistent with previous studies that had collected HF-HRV and brain activity during separate resting state sessions. These results support the tenets of the neurovisceral integration model and the utility of fNIRS in future studies examining the model and its relation to cognitive functions. The second performed a secondary data analysis on the go/no-go task used in the above study to examine prefrontal connectivity during a simple go/no-go task and an emotional go/no-go task. Findings show that stronger connectivity was associated with better performance on the simple task in both males and females; however, stronger connectivity was only associated with better performance on the emotional go/no-go in males. These findings show functional differences during emotional behavior inhibition in males compared to females.