Synthetic Heparan Sulfate Hydrogels Regulate Neurotrophic Factor Signaling and Neuronal Network Activity.

Three-dimensional (3D) synthetic heparan sulfate (HS) constructs possess promising attributes for neural tissue engineering applications. However, their sulfation-dependent ability to facilitate molecular recognition and cell signaling has not yet been investigated. We hypothesized that fully sulfated synthetic HS constructs (bearing compound 1) that are functionalized with neural adhesion peptides will enhance fibroblast growth factor-2 (FGF2) binding and complexation with FGF receptor-1 (FGFR1) to promote the proliferation and neuronal differentiation of human neural stem cells (hNSCs) when compared to constructs with unsulfated controls (bearing compound 2). We tested this hypothesis in vitro using 2D and 3D substrates consisting of different combinations of HS tetrasaccharides (compounds 3 and 4) and an engineered integrin-binding chimeric peptide (CP), which were assembled using strain-promoted alkyne-azide cycloaddition (SPAAC) chemistry. Results indicated that the adhesion of hNSCs increased significantly when cultured on 2D glass substrates functionalized with chimeric peptide. hNSCs encapsulated in 1-CP hydrogels and cultured in media containing the mitogen FGF2 exhibited significantly higher neuronal differentiation when compared to hNSCs in 2-CP hydrogels. These observations were corroborated by Western blot analysis, which indicated the enhanced binding and retention of both FGF2 and FGFR1 by 1 as well as downstream phosphorylation of extracellular signal-regulated kinases (ERK1/2) and enhanced proliferation of hNSCs. Lastly, calcium activity imaging revealed that both 1 and 2 hydrogels supported the neuronal growth and activity of pre-differentiated human prefrontal cortex neurons. Collectively, these results demonstrate that synthetic HS hydrogels can be tailored to regulate growth factor signaling and neuronal fate and activity.

Cortical Laminar Recording of Multi-unit Response to Distal Forelimb Electrical Stimulation in Rats.

Severe traumatic brain injury (sTBI) survivors experience permanent functional disabilities due to significant volume loss and the brain's poor capacity to regenerate. Chondroitin sulfate glycosaminoglycans (CS-GAGs) are key regulators of growth factor signaling and neural stem cell homeostasis in the brain. In this protocol, we describe how to perform recordings to quantify the neuroprotective and regenerative effect of implanted engineered CS-GAG hydrogel (eCS) on brain tissue. This experiment was performed in rats under three conditions: healthy without injury (Sham), controlled cortical impact (CCI) injury on the rostral forelimb area (RFA), and CCI-RFA with eCS implants. This protocol describes the procedure used to perform the craniotomy, the positioning of the cortical recording electrode, the positioning of the stimulation electrode (contralateral paw), and the recording procedure. In addition, a description of the exact electrical setup is provided. This protocol details the recordings in the brain of injured animals while preserving most of the uninjured tissue intact, with additional considerations for intralesional and laminar recordings of multi-unit response. Graphic abstract: Sensorimotor response to paw stimulation using cortical laminar recordings.

Engineered glycomaterial implants orchestrate large-scale functional repair of brain tissue chronically after severe traumatic brain injury.

Severe traumatic brain injury (sTBI) survivors experience permanent functional disabilities due to significant volume loss and the brain's poor capacity to regenerate. Chondroitin sulfate glycosaminoglycans (CS-GAGs) are key regulators of growth factor signaling and neural stem cell homeostasis in the brain. However, the efficacy of engineered CS (eCS) matrices in mediating structural and functional recovery chronically after sTBI has not been investigated. We report that neurotrophic factor functionalized acellular eCS matrices implanted into the rat M1 region acutely after sTBI significantly enhanced cellular repair and gross motor function recovery when compared to controls 20 weeks after sTBI. Animals subjected to M2 region injuries followed by eCS matrix implantations demonstrated the significant recovery of "reach-to-grasp" function. This was attributed to enhanced volumetric vascularization, activity-regulated cytoskeleton (Arc) protein expression, and perilesional sensorimotor connectivity. These findings indicate that eCS matrices implanted acutely after sTBI can support complex cellular, vascular, and neuronal circuit repair chronically after sTBI.

Neurostimulation and Reach-to-Grasp Function Recovery Following Acquired Brain Injury: Insight From Pre-clinical Rodent Models and Human Applications.

Reach-to-grasp is an evolutionarily conserved motor function that is adversely impacted following stroke and traumatic brain injury (TBI). Non-invasive brain stimulation (NIBS) methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, are promising tools that could enhance functional recovery of reach-to-grasp post-brain injury. Though the rodent literature provides a causal understanding of post-injury recovery mechanisms, it has had a limited impact on NIBS protocols in human research. The high degree of homology in reach-to-grasp circuitry between humans and rodents further implies that the application of NIBS to brain injury could be better informed by findings from pre-clinical rodent models and neurorehabilitation research. Here, we provide an overview of the advantages and limitations of using rodent models to advance our current understanding of human reach-to-grasp function, cortical circuitry, and reorganization. We propose that a cross-species comparison of reach-to-grasp recovery could provide a mechanistic framework for clinically efficacious NIBS treatments that could elicit better functional outcomes for patients.

The rostroventral part of the thalamic reticular nucleus modulates fear extinction.

The thalamus has been implicated in fear extinction, yet the role of the thalamic reticular nucleus (TRN) in this process remains unclear. Here, in mice, we show that the rostroventral part of the TRN (TRNrv) is critically involved in the extinction of tone-dependent fear memory. Optogenetic excitation of TRNrv neurons during extinction learning dramatically facilitated, whereas the inhibition disrupted, the fear extinction. Single unit recordings demonstrated that TRNrv neurons selectively respond to conditioned stimuli but not to neutral stimuli. TRNrv neurons suppressed the spiking activity of the medial part of the dorsal midline thalamus (dMTm), and a blockade of this inhibitory pathway disrupted fear extinction. Finally, we found that the suppression of dMTm projections to the central amygdala promotes fear extinction, and TRNrv neurons have direct connections to this pathway. Our results uncover a previously unknown function of the TRN and delineate the neural circuit for thalamic control of fear memory.

Chronic Electrical Stimulation Promotes the Excitability and Plasticity of ESC-derived Neurons following Glutamate-induced Inhibition In vitro.

Functional electrical stimulation (FES) is rapidly gaining traction as a therapeutic tool for mediating the repair and recovery of the injured central nervous system (CNS). However, the underlying mechanisms and impact of these stimulation paradigms at a molecular, cellular and network level remain largely unknown. In this study, we used embryonic stem cell (ESC)-derived neuron and glial co-cultures to investigate network maturation following acute administration of L-glutamate, which is a known mediator of excitotoxicity following CNS injury. We then modulated network maturation using chronic low frequency stimulation (LFS) and direct current stimulation (DCS) protocols. We demonstrated that L-glutamate impaired the rate of maturation of ESC-derived neurons and glia immediately and over a week following acute treatment. The administration of chronic LFS and DCS protocols individually following L-glutamate infusion significantly promoted the excitability of neurons as well as network synchrony, while the combination of LFS/DCS did not. qRT-PCR analysis revealed that LFS and DCS alone significantly up-regulated the expression of excitability and plasticity-related transcripts encoding N-methyl-D-aspartate (NMDA) receptor subunit (NR2A), brain-derived neurotrophic factor (BDNF) and Ras-related protein (RAB3A). In contrast, the simultaneous administration of LFS/DCS down-regulated BDNF and RAB3A expression. Our results demonstrate that LFS and DCS stimulation can modulate network maturation excitability and synchrony following the acute administration of an inhibitory dose of L-glutamate, and upregulate NR2A, BDNF and RAB3A gene expression. Our study also provides a novel framework for investigating the effects of electrical stimulation on neuronal responses and network formation and repair after traumatic brain injury.

Thalamic Spindles Promote Memory Formation during Sleep through Triple Phase-Locking of Cortical, Thalamic, and Hippocampal Rhythms.

While the interaction of the cardinal rhythms of non-rapid-eye-movement (NREM) sleep-the thalamo-cortical spindles, hippocampal ripples, and the cortical slow oscillations-is thought to be critical for memory consolidation during sleep, the role spindles play in this interaction is elusive. Combining optogenetics with a closed-loop stimulation approach in mice, we show here that only thalamic spindles induced in-phase with cortical slow oscillation up-states, but not out-of-phase-induced spindles, improve consolidation of hippocampus-dependent memory during sleep. Whereas optogenetically stimulated spindles were as efficient as spontaneous spindles in nesting hippocampal ripples within their excitable troughs, stimulation in-phase with the slow oscillation up-state increased spindle co-occurrence and frontal spindle-ripple co-occurrence, eventually resulting in increased triple coupling of slow oscillation-spindle-ripple events. In-phase optogenetic suppression of thalamic spindles impaired hippocampus-dependent memory. Our results suggest a causal role for thalamic sleep spindles in hippocampus-dependent memory consolidation, conveyed through triple coupling of slow oscillations, spindles, and ripples.

Arousal Rules: An Empirical Investigation into the Aesthetic Experience of Cross-Modal Perception with Emotional Visual Music.

Emotional visual music is a promising tool for the study of aesthetic perception in human psychology; however, the production of such stimuli and the mechanisms of auditory-visual emotion perception remain poorly understood. In Experiment 1, we suggested a literature-based, directive approach to emotional visual music design, and inspected the emotional meanings thereof using the self-rated psychometric and electroencephalographic (EEG) responses of the viewers. A two-dimensional (2D) approach to the assessment of emotion (the valence-arousal plane) with frontal alpha power asymmetry EEG (as a proposed index of valence) validated our visual music as an emotional stimulus. In Experiment 2, we used our synthetic stimuli to investigate possible underlying mechanisms of affective evaluation mechanisms in relation to audio and visual integration conditions between modalities (namely congruent, complementation, or incongruent combinations). In this experiment, we found that, when arousal information between auditory and visual modalities was contradictory [for example, active (+) on the audio channel but passive (-) on the video channel], the perceived emotion of cross-modal perception (visual music) followed the channel conveying the stronger arousal. Moreover, we found that an enhancement effect (heightened and compacted in subjects' emotional responses) in the aesthetic perception of visual music might occur when the two channels contained contradictory arousal information and positive congruency in valence and texture/control. To the best of our knowledge, this work is the first to propose a literature-based directive production of emotional visual music prototypes and the validations thereof for the study of cross-modally evoked aesthetic experiences in human subjects.

Dynamical nonstationarity of resting EEGs in patients with attention-deficit/hyperactivity disorder (AD/HD).

This study applied dynamical nonstationarity analysis (DNA) to the resting EEGs of patients with attention-deficit/hyperactivity disorder (AD/HD). We aimed to assess and characterize AD/HD using features based on the local and global duration of dynamical microstate. We hypothesized that AD/HD patients would have difficulties in maintaining stable cognitive states (e.g., attention deficit and impulsivity) and that they would thus exhibit EEGs with temporal dynamics distinct from normal controls, i.e., rapidly and frequently changing dynamics. To test this hypothesis, we recorded EEGs from 12 adolescent subjects with AD/HD and 11 age-matched healthy subjects in the resting state with eyes closed and eyes open. We found that AD/HD patients exhibited significantly faster changes in dynamics than controls in the right temporal region during the eyes closed condition, but slower changes in dynamics in the frontal region during the eyes open condition. AD/HD patients exhibited a disruption in the rate of change of dynamics in the frontotemporal region at rest, probably due to executive and attention processes. We suggest that the DNA using complementary local and global features based on the duration of dynamical microstates could be a useful tool for the clinical diagnosis of subjects with AD/HD.

Multiway array decomposition analysis of EEGs in Alzheimer's disease.

Methods for the extraction of features from physiological datasets are growing needs as clinical investigations of Alzheimer's disease (AD) in large and heterogeneous population increase. General tools allowing diagnostic regardless of recording sites, such as different hospitals, are essential and if combined to inexpensive non-invasive methods could critically improve mass screening of subjects with AD. In this study, we applied two state of the art multiway array decomposition (MAD) methods to extract unique features from electroencephalograms (EEGs) of AD patients obtained from multiple sites. In comparison to MAD, spectral-spatial average filter (SSFs) of control and AD subjects were used as well as a common blind source separation method, algorithm for multiple unknown signal extraction (AMUSE), and singular value decomposition (SVD) coupled to tensor unfolding. We trained a feed-forward multilayer perceptron (MLP) to validate and optimize AD classification from two independent databases. Using a third EEG dataset, we demonstrated that features extracted from MAD outperformed features obtained from SSFs AMUSE in terms of root mean squared error (RMSE) and reaching up to 100% of accuracy in test condition. We propose that MAD maybe a useful tool to extract features for AD diagnosis offering great generalization across multi-site databases and opening doors to the discovery of new characterization of the disease.