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1. Neurocognitive mechanisms of co‐occurring math difficulties in dyslexia: Differences in executive function and visuospatial processing

   https://doi.org/10.1111/desc.13443  

   Marks, Rebecca A. ; Pollack, Courtney ; Meisler, Steven L. ; D'Mello, Anila M. ; Centanni, Tracy M. ; Romeo, Rachel R. ; Wade, Karolina ; Matejko, Anna A. ; Ansari, Daniel ; Gabrieli, John D. E. ; et al ( September 2023 , Developmental Science)

   Children with dyslexia frequently also struggle with math. However, studies of reading disability (RD) rarely assess math skill, and the neurocognitive mechanisms underlying co‐occurring reading and math disability (RD+MD) are not clear. The current study aimed to identify behavioral and neurocognitive factors associated with co‐occurring MD among 86 children with RD. Within this sample, 43% had co‐occurring RD+MD and 22% demonstrated a possible vulnerability in math, while 35% had no math difficulties (RD‐Only). We investigated whether RD‐Only and RD+MD students differed behaviorally in their phonological awareness, reading skills, or executive functions, as well as in the brain mechanisms underlying word reading and visuospatial working memory using functional magnetic resonance imaging (fMRI). The RD+MD group did not differ from RD‐Only on behavioral or brain measures of phonological awareness related to speech or print. However, the RD+MD group demonstrated significantly worse working memory and processing speed performance than the RD‐Only group. The RD+MD group also exhibited reduced brain activations for visuospatial working memory relative to RD‐Only. Exploratory brain‐behavior correlations along a broad spectrum of math ability revealed that stronger math skills were associated with greater activation in bilateral visual cortex. These converging neuro‐behavioral findings suggest that poor executive functions in general, including differences in visuospatial working memory, are specifically associated with co‐occurring MD in the context of RD.

   Children with reading disabilities (RD) frequently have a co‐occurring math disability (MD), but the mechanisms behind this high comorbidity are not well understood.

   We examined differences in phonological awareness, reading skills, and executive function between children with RD only versus co‐occurring RD+MD using behavioral and fMRI measures.

   Children with RD only versus RD+MD did not differ in their phonological processing, either behaviorally or in the brain.

   RD+MD was associated with additional behavioral difficulties in working memory, and reduced visual cortex activation during a visuospatial working memory task.

    

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2. Classifying Patients with pFC Lesions from Healthy Controls Using Directed Information Based Effective Brain Connectivity Measured from the Encoding Phase of Working Memory Task

   https://doi.org/10.1109/ISBI53787.2023.10230817  

   Balaji, Sai Sanjay ; Parhi, Keshab K. ( April 2023 , Proc. of 2023 IEEE 20th International Symposium on Biomedical Imaging (ISBI))

   This paper describes a group-level analysis of 14 subjects with prefrontal cortex (pFC) lesions and 20 healthy controls performing multiple lateralized visuospatial working memory (WM) trials. Using effective brain connectivity measures inferred from directed information (DI) during memory encoding, we first show that DI features can correctly classify 18 control subjects and 11 subjects with pFC lesions, providing an overall accuracy of 85.3%. Second, we show that differential DI, the change in DI during the encoding phase from pretrial, can successfully overcome inter-subject variability and correctly identify the class of all 34 subjects (100% accuracy). These accuracy results are based on two-thirds majority thresholding among all trials. Finally, we use Welch’s t-test to identify the crucial differences in the two classes’ sub-networks responsible for memory encoding. While the inflow of information to the prefrontal region is significant among subjects with pFC lesions, the outflow from the prefrontal to the frontal and central regions is diminished compared to the control subjects. We further identify specific neural pathways that are exclusively activated for each group during the encoding phase. 

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3. Cholinergic neuromodulation of prefrontal attractor dynamics controls performance in spatial working memory

   https://doi.org/10.1523/JNEUROSCI.1225-23.2024  

   Mahrach, Alexandre ; Bestue, David ; Qi, Xue-Lian ; Constantinidis, Christos ; Compte, Albert ( April 2024 , The Journal of Neuroscience)

   The behavioral and neural effects of the endogenous release of acetylcholine following stimulation of the Nucleus Basalis of Meynert (NB) have been recently examined in two male monkeys (Qi et al. 2021). Counterintuitively, NB stimulation enhanced behavioral performance while broadening neural tuning in the prefrontal cortex (PFC). The mechanism by which a weaker mnemonic neural code could lead to better performance remains unclear. Here, we show that increased neural excitability in a simple continuous bump attractor model can induce broader neural tuning and decrease bump diffusion, provided neural rates are saturated. Increased memory precision in the model overrides memory accuracy, improving overall task performance. Moreover, we show that bump attractor dynamics can account for the nonuniform impact of neuromodulation on distractibility, depending on distractor distance from the target. Finally, we delve into the conditions under which bump attractor tuning and diffusion balance in biologically plausible heterogeneous network models. In these discrete bump attractor networks, we show that reducing spatial correlations or enhancing excitatory transmission can improve memory precision. Altogether, we provide a mechanistic understanding of how cholinergic neuromodulation controls spatial working memory through perturbed attractor dynamics in PFC.

   Significance statementAcetylcholine has been thought to improve cognitive performance by sharpening neuronal tuning in prefrontal cortex. Recent work has shown that electrical stimulation of the cholinergic forebrain in awake-behaving monkeys induces a reduction in prefrontal neural tuning under stimulation conditions that improve performance. To reconcile these divergent observations, we provide network simulations showing that these derive consistently from specific conditions in prefrontal attractor dynamics: firing rate saturation leads to increased storage precision and reduced neural tuning upon cholinergic activation via an increase in neural excitability, a reduction in neural correlations, and an increase in excitatory transmission. Our study integrates previously reported data into a consistent mechanistic view of how acetylcholine controls spatial working memory via attractor network dynamics in prefrontal cortex.

    

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4. Neurocognition of New Ideas During Engineering Design

   https://doi.org/10.1115/DETC2023-117127  

   Walker, Emma ; Shealy, Tripp ; Gero, John ( August 2023 , ASME 2023 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference)

   The research presented in this paper investigated the changes that occur in the prefrontal cortex (PFC) when new ideas are introduced during engineering design. Undergraduate and graduate engineering students (n = 25) were outfitted with a functional near-infrared spectroscopy (fNIRS) headband. Students were asked to design a personal entertainment system while thinking aloud. New ideas were timestamped with the fNIRS data across 48 channels grouped into eight regions within the PFC. The data were preprocessed using temporal derivative distribution repair motion correction, finite impulse response bandpass filter, and the modified beer-lambert law to convert optical density into hemoglobin concentration. Baseline neurocognitive activation and physiological noise were removed. The study found a significant decrease in oxygenated hemoglobin in the left dorsolateral prefrontal cortex and a subregion of the left ventrolateral prefrontal cortex when new ideas were introduced during design. This finding begins to provide a neurocognitive signature of what a new idea looks like as it arises in the brain. This could be used to develop tools and techniques to inhibit this brain region or use this insight to predict when designers will experience a new idea based on their neural activation.

    

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5. Post‐training stimulation of the right dorsolateral prefrontal cortex impairs working memory training performance

   https://doi.org/10.1002/jnr.24784  

   Au, Jacky ; Katz, Benjamin ; Moon, Austin ; Talati, Sheebani ; Abagis, Tessa R. ; Jonides, John ; Jaeggi, Susanne M. ( January 2021 , Journal of Neuroscience Research)

   Research investigating transcranial direct current stimulation (tDCS) to enhance cognitive training augments both our understanding of its long‐term effects on cognitive plasticity as well as potential applications to strengthen cognitive interventions. Previous work has demonstrated enhancement of working memory training while applying concurrent tDCS to the dorsolateral prefrontal cortex (DLPFC). However, the optimal stimulation parameters are still unknown. For example, the timing of tDCS delivery has been shown to be an influential variable that can interact with task learning. In the present study, we used tDCS to target the right DLPFC while participants trained on a visuospatial working memory task. We sought to compare the relative efficacy of online stimulation delivered during training to offline stimulation delivered either immediately before or afterwards. We were unable to replicate previously demonstrated benefits of online stimulation; however, we did find evidence that offline stimulation delivered after training can actually be detrimental to training performance relative to sham. We interpret our results in light of evidence suggesting a role of the right DLPFC in promoting memory interference, and conclude that while tDCS may be a promising tool to influence the results of cognitive training, more research and an abundance of caution are needed before fully endorsing its use for cognitive enhancement. This work suggests that effects can vary substantially in magnitude and direction between studies, and may be heavily dependent on a variety of intervention protocol parameters such as the timing and location of stimulation delivery, about which our understanding is still nascent.

    

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