GABA: A critical player for regulating synaptic plasticity and adult neurogenesis

During aging, the decrease of cognitive ability is believed to be the cause of age related neuronal damage and reduced proliferation and differentiation of adult-born neural precursor cells. To modulate the synaptic plasticity and adult neurogenesis, it is of immense importance to enhance the potential of resident neural stem cells of hippocampus and sub ventricular zone (SVZ). The necessity to restore brain functions is enormous in the neurodegenerative disease like Alzheimer, Parkinson diseases, stress induced cognitive dysfunction, depression and age-associated and HIV-associated dementia. As a pioneer transmitter, Gamma Amino Butaric Acid (GABA) influences the activity dependent adult neurogenesis and excites immature neurons in adult hippocampus. GABA holds the key for making adult immature neuron to mature functional neuron hence plays critical role in adult neurogenesis.This review aims to discuss about the spatio-temporal expression of various subunit of GABA-A receptor and how these subunits intimately modulates the synaptic plasticity. During developmental period GABAergic neurons mature at early stages and regulate overall neural activity much before the activity of glutamate. Not only during development but also during adult neurogenesis GABA plays a significant role in neurite outgrowth and establishing well network.

Bioceramic Material Stimulation Affects Perceptual Consciousness: A Study Combining Descriptive Observation and Functional MRI Connectivity Analysis

There is still no clear explanation of the process of perceptual consciousness that connects our body with brain. Innovation on the technology of bioceramic has now advanced towards clinical applications, including rehabilitation of brain infarction, therapies of insomnia and migraine. To demonstrate how ‘resonant energy transfer through the bioceramic material with tempo sound and visible light spectrum’ (bioceramic material stimulation, BMS) non-invasively affects perceptual consciousness, we investigated the responses of participants to BMS on perceptual consciousness by questionnaire of subjective descriptions and analyzed resting state fMRI during BMS. There were 61.3% participants who were categorized as positive group with various types of perceptual consciousness. By setting a threshold value at ‘p<0.001’, enhanced connections of ‘parahippocampal gyrus to cerebellar lobule V’ and ‘angular gyrus to precuneus’ were found. However, decreased connection of ‘caudate nucleus to cerebellar lobule VIIb’ was found. We conclude that the most affected brain functions by BMS including somatosensory, audio-visual perception and social cognition. The analysis of functional connectivity during BMS may help us gain more knowledge of consciousness and related division of neuroscience in humans.

Opto-electrical bimodal recording of neural activity in awake head-restrained mice

Electrical and optical monitoring of neural activity is major approaches for studying brain functions. Each has its own set of advantages and disadvantages, such as the ability to determine cell types and temporal resolution. Although opto-electrical bimodal recording is beneficial by enabling us to exploit the strength of both approaches, it has not been widely used. In this study, we devised three methods of bimodal recording from a deep brain structure in awake head-fixed mice by chronically implanting a gradient-index (GRIN) lens and electrodes. First, we attached four stainless steel electrodes to the side of a GRIN lens and implanted them in a mouse expressing GCaMP6f in astrocytes. We simultaneously recorded local field potential (LFP) and GCaMP6f signal in astrocytes in the hippocampal CA1 area. Second, implanting a silicon probe electrode mounted on a custom-made microdrive within the focal volume of a GRIN lens, we performed bimodal recording in the CA1 area. We monitored LFP and fluorescent changes of GCaMP6s-expressing neurons in the CA1. Third, we designed a 3D-printed scaffold to serve as a microdrive for a silicon probe and a holder for a GRIN lens. This scaffold simplifies the implantation process and makes it easier to place the lens and probe accurately. Using this method, we recorded single unit activity and LFP electrically and GCaMP6f signals of single neurons optically. Thus, we show that these opto-electrical bimodal recording methods using a GRIN lens and electrodes are viable approaches in awake head-fixed mice.

Mobile Phone Radiation Deflects Brain Energy Homeostasis and Prompts Human Food Ingestion

Obesity and mobile phone usage have simultaneously spread worldwide. Radio frequency-modulated electromagnetic fields (RF-EMFs) emitted by mobile phones are largely absorbed by the head of the user, influence cerebral glucose metabolism, and modulate neuronal excitability. Body weight adjustment, in turn, is one of the main brain functions as food intake behavior and appetite perception underlie hypothalamic regulation. Against this background, we questioned if mobile phone radiation and food intake may be related. In a single-blind, sham-controlled, randomized crossover comparison, 15 normal-weight young men (23.47 ± 0.68 years) were exposed to 25 min of RF-EMFs emitted by two different mobile phone types vs. sham radiation under fasting conditions. Spontaneous food intake was assessed by an ad libitum standard buffet test and cerebral energy homeostasis was monitored by 31phosphorus-magnetic resonance spectroscopy measurements. Exposure to both mobile phones strikingly increased overall caloric intake by 22–27% compared with the sham condition. Differential analyses of macronutrient ingestion revealed that higher calorie consumption was mainly due to enhanced carbohydrate intake. Measurements of the cerebral energy content, i.e., adenosine triphosphate and phosphocreatine ratios to inorganic phosphate, displayed an increase upon mobile phone radiation. Our results identify RF-EMFs as a potential contributing factor to overeating, which underlies the obesity epidemic. Beyond that, the observed RF-EMFs-induced alterations of the brain energy homeostasis may put our data into a broader context because a balanced brain energy homeostasis is of fundamental importance for all brain functions. Potential disturbances by electromagnetic fields may therefore exert some generalized neurobiological effects, which are not yet foreseeable.

No Alteration Between Intrinsic Connectivity Networks by a Pilot Study on Localized Exposure to the Fourth-Generation Wireless Communication Signals

Neurophysiological effect of human exposure to radiofrequency signals has attracted considerable attention, which was claimed to have an association with a series of clinical symptoms. A few investigations have been conducted on alteration of brain functions, yet no known research focused on intrinsic connectivity networks, an attribute that may relate to some behavioral functions. To investigate the exposure effect on functional connectivity between intrinsic connectivity networks, we conducted experiments with seventeen participants experiencing localized head exposure to real and sham time-division long-term evolution signal for 30 min. The resting-state functional magnetic resonance imaging data were collected before and after exposure, respectively. Group-level independent component analysis was used to decompose networks of interest. Three states were clustered, which can reflect different cognitive conditions. Dynamic connectivity as well as conventional connectivity between networks per state were computed and followed by paired sample t-tests. Results showed that there was no statistical difference in static or dynamic functional network connectivity in both real and sham exposure conditions, and pointed out that the impact of short-term electromagnetic exposure was undetected at the ICNs level. The specific brain parcellations and metrics used in the study may lead to different results on brain modulation.

Mental workLoad Accumulation Effect of Mobile Phone Distraction in L2 Autopilot Mode

As self-driving vehicles become more common, there is a need for precise measurement and definition of when and in what ways a driver can use a mobile phone in autonomous driving mode, for how long it can be used, the complexity of the call content, and the accumulated psychological load. This study uses a 2 (driving mode) * 2 (call content complexity) * 6 (driving phase) three-factor mixed experimental design to investigate the effect of these factors on the driver's psychological load by measuring the driver's performance on peripheral visual detection tasks, pupil diameter, and EEG components in various brain regions in the alpha band. The results showed that drivers' mental load levels converge between manual and automatic driving modes as the duration of driving increases, regardless of the level of complexity of the mobile phone conversation. This suggests that mobile phone conversations can also disrupt the driver's cognitive resource balance in automatic driving mode, as it increases mental load while also impairing the normal functioning of brain functions such as cognitive control, problem solving, and judgment, thereby compromising driving safety.

Astrocytes as Key Regulators of Brain Energy Metabolism: New Therapeutic Perspectives

Astrocytes play key roles in the regulation of brain energy metabolism, which has a major impact on brain functions, including memory, neuroprotection, resistance to oxidative stress and homeostatic tone. Energy demands of the brain are very large, as they continuously account for 20–25% of the whole body’s energy consumption. Energy supply of the brain is tightly linked to neuronal activity, providing the origin of the signals detected by the widely used functional brain imaging techniques such as functional magnetic resonance imaging and positron emission tomography. In particular, neuroenergetic coupling is regulated by astrocytes through glutamate uptake that triggers astrocytic aerobic glycolysis and leads to glucose uptake and lactate release, a mechanism known as the Astrocyte Neuron Lactate Shuttle. Other neurotransmitters such as noradrenaline and Vasoactive Intestinal Peptide mobilize glycogen, the reserve for glucose exclusively localized in astrocytes, also resulting in lactate release. Lactate is then transferred to neurons where it is used, after conversion to pyruvate, as a rapid energy substrate, and also as a signal that modulates neuronal excitability, homeostasis, and the expression of survival and plasticity genes. Importantly, glycolysis in astrocytes and more generally cerebral glucose metabolism progressively deteriorate in aging and age-associated neurodegenerative diseases such as Alzheimer’s disease. This decreased glycolysis actually represents a common feature of several neurological pathologies. Here, we review the critical role of astrocytes in the regulation of brain energy metabolism, and how dysregulation of astrocyte-mediated metabolic pathways is involved in brain hypometabolism. Further, we summarize recent efforts at preclinical and clinical stages to target brain hypometabolism for the development of new therapeutic interventions in age-related neurodegenerative diseases.

It’s about time: Linking dynamical systems with human neuroimaging to understand the brain

Most human neuroscience research to date has focused on statistical approaches that describe stationary patterns of localized neural activity or blood flow. While these patterns are often interpreted in light of dynamic, information-processing concepts, the static, local and inferential nature of the statistical approach makes it challenging to directly link neuroimaging results to plausible underlying neural mechanisms. Here, we argue that dynamical systems theory provides the crucial mechanistic framework for characterizing both the brain’s time-varying quality and its partial stability in the face of perturbations, and hence, that this perspective can have a profound impact on the interpretation of human neuroimaging results and their relationship with behavior. After briefly reviewing some key terminology, we identify three key ways in which neuroimaging analyses can embrace a dynamical systems perspective: by shifting from a local to a more global perspective; by focusing on dynamics instead of static snapshots of neural activity; and by embracing modeling approaches that map neural dynamics using “forward” models. Through this approach, we envisage ample opportunities for neuroimaging researchers to enrich their understanding of the dynamic neural mechanisms that support a wide array of brain functions, both in health and in the setting of psychopathology.

Focal neural perturbations reshape low-dimensional trajectories of brain activity supporting cognitive performance

The emergence of distributed patterns of neural activity supporting brain functions and behavior can be understood by study of the brain’s low-dimensional topology. Functional neuroimaging demonstrates that brain activity linked to adaptive behavior is constrained to low-dimensional manifolds. In human participants, we tested whether these low-dimensional constraints preserve working memory performance following local neuronal perturbations. We combined multi-session functional magnetic resonance imaging, non-invasive transcranial magnetic stimulation (TMS), and methods translated from the fields of complex systems and computational biology to assess the functional link between changes in local neural activity and the reshaping of task-related low dimensional trajectories of brain activity. We show that specific reconfigurations of low-dimensional trajectories of brain activity sustain effective working memory performance following TMS manipulation of local activity on, but not off, the space traversed by these trajectories. We highlight an association between the multi-scale changes in brain activity underpinning cognitive function.

Intraoperative hand strength as an indicator of consciousness during awake craniotomy: a prospective, observational study

Awake craniotomy enables mapping and monitoring of brain functions. For successful procedures, rapid awakening and the precise evaluation of consciousness are required. A prospective, observational study conducted to test whether intraoperative hand strength could be a sensitive indicator of consciousness during the awake phase of awake craniotomy. Twenty-three patients who underwent awake craniotomy were included. Subtle changes of the level of consciousness were assessed by the Japan Coma Scale (JCS). The associations of hand strength on the unaffected side with the predicted plasma concentration (Cp) of propofol, the bispectral index (BIS), and the JCS were analyzed. Hand strength relative to the preoperative maximum hand strength on the unaffected side showed significant correlations with the Cp of propofol (ρ = − 0.219, p = 0.007), the BIS (ρ = 0.259, p = 0.002), and the JCS (τ = − 0.508, p = 0.001). Receiver operating characteristic curve analysis for discriminating JCS 0–1 and JCS ≥ 2 demonstrated that the area under the curve was 0.76 for hand strength, 0.78 for Cp of propofol, and 0.66 for BIS. With a cutoff value of 75% for hand strength, the sensitivity was 0.76, and the specificity was 0.67. These data demonstrated that hand strength is a useful indicator for assessing the intraoperative level of consciousness during awake craniotomy.