Tracking Changes in Frontal Lobe Hemodynamic Response in Individual Adults With Developmental Language Disorder Following HD tDCS Enhanced Phonological Working Memory Training: An fNIRS Feasibility Study

Abstract

Background: Current research suggests a neurobiological marker of developmental language disorder (DLD) in adolescents and young adults may be an atypical neural profile coupled with behavioral performance that overlaps with that of normal controls. Although many imaging techniques are not suitable for the study of speech and language processing in DLD populations, fNIRS may be a viable option. In this study we asked if fNIRS can be used to identify atypical cortical activation patterns in individual adults with DLD and track potential changes in cortical activation patterns following a phonological working memory training protocol enhanced with anodal HD tDCS stimulation to the presupplementary motor area (preSMA). Objective/Hypothesis: The purpose of this study was two-fold: (1) to determine if fNIRS can be used to identify atypical hemodynamic responses in individual young adults with DLD during active spoken word processing and, (2) to determine if fNIRS can detect changes in hemodynamic response in these same adults with DLD following anodal HD tDCS enhanced phonological working memory training. Methods: Two adult subjects with DLD (female, age 25) completed a total of two sessions of fNIRs working memory task prior to and following one session of a non-word repetition task paired with anodal HD tDCS (1.0 mA tDCS; 20 min) to the preSMA. Standardized z -scores of behavioral measures (accuracy and reaction time) and changes in hemodynamic response during an n-back working memory task for the two participants with DLD was compared to that of a normative sample of 21 age- and gender- matched normal controls (ages 18 to 25) prior to and following phonological working memory training. Results: Individual standardized z -scores for each participant with DLD indicated that prior to training, hemoglobin response in the prefrontal lobe for both participants was markedly different from each other and normal controls. Following training, standard scores showed that the hemodynamic response for both participants moved within normal limits for ROIs. Conclusion: These findings highlight the feasibility of fNIRS to establish individual differences in the link between behavior and neural patterns in single subjects with DLD, as well as track individual differences in changes in brain activity following working memory training.

Neural patterns elicited by lexical processing in adolescents with specific language impairment: support for the procedural deficit hypothesis?

“…First, the findings from this study are based on group data and grand-average waveforms. Brown and colleagues [ 32 ] and Berglund-Barraza and colleagues [ 69 ] have both argued that group data obscures important differences in brain function in SLI. It is possible that examining the data at the group level in this study also obscured important individual differences in the pattern of cortical response on the part of the adolescents with SLI.…”

Long-term effects of repeated multitarget high-definition transcranial direct current stimulation combined with cognitive training on response inhibition gains

“…It cannot be excluded that parts of the motor area were stimulated as well, but fortunately this brain cortex has not been shown to be involved in the response inhibition process, which did not impact the interpretation of the findings in this study. Furthermore, there may be some confusions arising from the anode placement of pre-SMA because some previous studies placed the central anode at Fz to stimulate pre-SMA ( Berglund-Barraza et al, 2020 ; Chiang et al, 2021 ). This is because there may be some ambiguity in what people are calling “pre-SMA.” We see that some places call Area 8 pre-SMA and others call the anterior Area 6 pre-SMA.…”

Functional near‐infrared spectroscopy measures of neural activity in children with and without developmental language disorder during a working memory task

“…Berglund‐Barraza et al. ( 2020 ) used fNIRS and high‐definition transcranial direct current stimulation (tDCS) to investigate individual differences in WM training in two adults with DLD. Although this was a case study, their findings demonstrate that fNIRS could track individual differences in neural activity in the prefrontal cortex.…”

“…Although fNIRS research on DLD is sparse, fNIRS has been successfully used to study neural changes in children cognitive flexibility in preschoolers (Quiñones‐Camacho et al., 2019 ), mathematical cognition in primary school children (Skau et al., 2022 ), and WM and executive control in clinical populations such as Down syndrome (Xu et al., 2020 ), autism spectrum disorder (Zhang & Roeyers, 2019 ), ADHD (Gu et al., 2017 ), and patients with cochlear implants (Sherafati et al., 2022 ). In addition, fNIRS has been used to examine WM in adults (Baker et al., 2018 ; Berglund‐Barraza et al., 2019 ; Fishburn et al., 2014 ; Meidenbauer et al., 2021 ). fNIRS appears to be a viable tool for investigating neural activity in children with DLD as they perform an auditory WM memory task.…”

“…Berglund-Barraza et al, 2020).Fu and colleagues (2016) found higher oxygenated and deoxygenated hemoglobin in TD children in the bilateral perisylvian areas, specifically, right inferior frontal gyrus, left inferior posterior parietal junction, and left temporal and parietal junction, as they performed a sentence-processing task. Berglund-Barraza et al (2020) used fNIRS and high-definition transcranial direct current stimulation (tDCS) to investigate individual differences in WM training in two adults with DLD.…”