Hearing loss and intellectual outcome in children treated for embryonal brain tumors: Implications for young children treated with radiation sparing approaches.

PURPOSE: We investigate the impact of severe sensorineural hearing loss (SNHL) and for the first time evaluate the effect of unilateral versus bilateral SNHL on intellectual outcome in a cohort of children with embryonal brain tumors treated with and without radiation. METHODS: Data were from 94 childhood survivors of posterior fossa (PF) embryonal brain tumors who were treated with either: (1) chemotherapy alone (n = 16, 7.11 [3.41] years, 11M/5F), (2) standard-dose craniospinal irradiation (CSI) and/or large boost volumes (n = 44, 13.05 [3.26] years, 29M/15F), or (3) reduced-dose CSI with a boost restricted to the tumor bed (n = 34, 11.07 [3.80] years, 19M/15F). We compared intellectual outcome between children who: (1) did and did not develop SNHL and (2) developed unilateral versus bilateral SNHL. A Chang grade of ≥2b that required the use of a hearing aid was considered severe SNHL. Comparisons were made overall and within each treatment group separately. RESULTS: Patients who developed SNHL had lower full scale IQ (p = 0.007), verbal comprehension (p = 0.003), and working memory (p = 0.02) than patients without SNHL. No differences were observed between patients who had unilateral versus bilateral SNHL (all p > 0.05). Patients treated with chemotherapy alone who developed SNHL had lower mean working memory (p = 0.03) than patients who did not develop SNHL. Among patients treated with CSI, no IQ indices differed between those with and without SNHL (all p > 0.05). CONCLUSIONS: Children treated for embryonal brain tumors who develop severe SNHL have lower intellectual outcome than patients with preserved hearing: this association is especially profound in young children treated with radiation sparing approaches. We also demonstrate that intellectual outcome is similarly impaired in patients who develop unilateral versus bilateral SNHL. These findings suggest that early intervention to preserve hearing is critical.

Photobiomodulation Enhances Memory Processing in Older Adults with Mild Cognitive Impairment: A Functional Near-Infrared Spectroscopy Study.

BACKGROUND: Recent studies of photobiomodulation (PBM) in patients with cognitive or psychological disorders (including traumatic brain injury, stroke, and dementia) have yielded some encouraging results. OBJECTIVE: In this study, we aimed to investigate the effect of a single stimulation on memory in older adults with mild cognitive impairment (MCI). METHODS: After PBM, hemodynamic changes, as a measure of functional brain activity, were evaluated using functional near-infrared spectroscopy (fNIRS). Eighteen subjects who met the criteria of MCI were randomly assigned to control and experimental groups. A single real or sham PBM session was administered to the forehead of each patient in the experimental and control groups, respectively. All subjects performed a visual memory span test before and after the stimulation, and their hemodynamic responses during the tasks were measured using fNIRS. RESULTS: The results showed that among the MCI subjects, only those who received PBM, but not those who received the sham stimulation, demonstrated significant improvement in the visual memory performance and a reduction in the hemodynamic response during the tasks. CONCLUSION: These findings suggest that PBM may reduce the cognitive efforts needed to complete tasks that require high memory loads, and thus improve the cognitive performance of individuals with MCI.

Neurobehavioral effects of acute low-dose whole-body irradiation.

Radiation exposure has multiple effects on the brain, behavior and cognitive functions. It has been reported that high-dose (>20 Gy) radiation-induced behavior and cognitive aberration partly associated with severe tissue destruction. Low-dose (<3 Gy) exposure can occur in radiological disasters and cerebral endovascular treatment. However, only a few reports analyzed behavior and cognitive functions after low-dose irradiation. This study was undertaken to assess the relationship between brain neurochemistry and behavioral disruption in irradiated mice. The irradiated mice (0.5 Gy, 1 Gy and 3 Gy) were tested for alteration in their normal behavior over 10 days. A serotonin (5-HT), Dopamine, gamma-Aminobutyric acid (GABA) and cortisol analysis was carried out in blood, hippocampus, amygdala and whole brain tissue. There was a significant decline in the exploratory activity of mice exposed to 3 Gy and 1 Gy radiation in an open field test. We observed a significant short-term memory loss in 3 Gy and 1 Gy irradiated mice in Y-Maze. Mice exposed to 1 Gy and 3 Gy radiation exhibited increased anxiety in an elevated plus maze (EPM). The increased anxiety and memory loss patterns were also seen in 0.5 Gy irradiated mice, but the results were not statistically significant. In this study we observed that neurotransmitters are significantly altered after irradiation, but the neuronal cells in the hippocampus were not significantly affected. This study suggests that the low-dose radiation-induced cognitive impairment may be associated with the neurochemical in low-dose irradiation and unlike the high-dose scenario might not be directly related to the morphological changes in the brain.

Blue light exposure enhances neural efficiency of the task positive network during a cognitive interference task.

Exposure to light, particularly blue-wavelength light, has been shown to acutely increase brain activation, alertness, and some elementary aspects of cognitive performance such as working memory and emotional anticipation. Whether blue light exposure can have effects on brain activation and performance during more complex cognitive control tasks up to 30 min after light cessation is unknown. In a sample of 32 healthy adults, we examined the effects of a 30 min exposure to either blue (n = 16) or amber control (n = 16) light on subsequent brain activation and performance during the Multi-Source Interference Task (MSIT) measured a half-hour after light exposure. Performance on the MSIT did not differ between the blue and amber conditions. However, brain activation within the task positive network (TPN) to the interference condition was significantly lower in the blue relative to the amber condition, while no group differences were observed for suppression of the default mode network (DMN). These findings suggest that, compared to control, a single exposure to blue light was associated with enhanced neural efficiency, as demonstrated by reduced TPN activation to achieve the same level of performance. Blue light may be an effective method for optimizing neurocognitive performance under some conditions.

Investigating the impact of mobile range electromagnetic radiation on the medial prefrontal cortex of the rat during working memory.

Research has been focused on the effects of radiofrequency electromagnetic radiation (RF-EMR) emitted from a mobile phone on general health, especially the nervous system. The purpose of this study was to investigate the impact of RF-EMR on the brain mechanism of rats by recording local field potentials (LFPs) signals during working memory (WM) task. Subjects were exposed to 900 MHz from a dipole antenna daily for three hours. Exposure was applied, first on a short term base (1 week) and then on a long term base (4 weeks). Behavioral parameters were measured weekly while rats performed T-maze tasks in two types of normal and delayed. LFPs signals were simultaneously recorded by implanted microelectrode arrays on the medial prefrontal cortex (mPFC) of rats. Results showed a significant increase (*p < 0.05) in the task completion time of exposed rats which vanished shortly after the end of short term RF-EMR exposure. Before exposure, during correctly performed delayed tasks, an increase (peak) in power changes of theta band (4-12 Hz) was observed. But during correctly performed normal tasks, an increase appeared only by applying RF-EMR exposure. The similarity in power changes pattern of theta band in both types of tasks was observed after long term exposure. Classification accuracy of LFPs in truly done normal and delayed tasks was compared in pre and post-exposure states. Initial classification accuracy was 84.2 % which decreased significantly (*P < 0.05) after exposure. These observations indicated that RF-EMR may cause unusual brain functioning which is temporary at least for short term exposure.

Effect of electromagnetic radiation on redox status, acetylcholine esterase activity and cellular damage contributing to the diminution of the brain working memory in rats.

Behavioral impairments are the most pragmatic outcome of long-term mobile uses but the underlying causes are still poorly understood. Therefore, the Aim of the present study to determine the possible mechanism of mobile induced behavioral alterations by observing redox status, cholinesterase activity, cellular, genotoxic damage and cognitive alterations in rat hippocampus. This study was carried out on 24 male Wistar rats, randomly divided into four groups (n = 6 in each group): group I consisted of sham-exposed (control) rats, group II-IV consisted of rats exposed to microwave radiation (900 MHz) at different time duration 1 h, 2 h, and 4 h respectively for 90 days. After 90 days of exposure, rats were assessing learning ability by using T-Maze. A significantly increased level of malondialdehyde (MDA) with concomitantly depleted levels of superoxide dismutase (SOD), catalase (CAT) and redox enzymes (GSH, GPX, GR, GST, G-6PDH) indicated an exposure of mobile emitted EMR induced oxidative stress by the depleted redox status of brain cells. The depletion in the acetylcholinesterase (AChE) level reveals altered neurotransmission in brain cells. Resultant cellular degeneration was also observed in the radiation-exposed hippocampus. Conclusively, the present study revealed that microwave radiation induces oxidative stress, depleted redox status, and causes DNA damage with the subsequent reduction in working memory in a time-dependent manner. This study provides insight over the associative reciprocity between redox status, cellular degeneration and reduced cholinergic activity, which presumably leads to the behavioral alterations following mobile emitted electromagnetic radiation.

Single session high definition transcranial direct current stimulation to the cerebellum does not impact higher cognitive function.

The prefrontal cortex is central to higher order cognitive function. However, the cerebellum, generally thought to be involved in motor control and learning, has also been implicated in higher order cognition. Recent work using transcranial direct current stimulation (tDCS) provides some support for right cerebellar involvement in higher order cognition, though the results are mixed, and often contradictory. Here, we used cathodal high definition tDCS (HD-tDCS) over the right cerebellum to assess the impact of HD-tDCS on modulating cognitive performance. We predicted that stimulation would result in performance decreases, which would suggest that optimal cerebellar function is necessary for cognitive performance, much like the prefrontal cortex. That is, it is not simply a structure that lends support to complete difficult tasks. While the expected cognitive behavioral effects were present, we did not find effects of stimulation. This has broad implications for cerebellar tDCS research, particularly for those who are interested in using HD-tDCS as a way of examining cerebellar function. Further implications, limitations, and future directions are discussed with particular emphasis on why null findings might be critical in developing a clear picture of the effects of tDCS on the cerebellum.

Corticostriatal stimulation compensates for medial frontal inactivation during interval timing.

Prefrontal dysfunction is a common feature of brain diseases such as schizophrenia and contributes to deficits in executive functions, including working memory, attention, flexibility, inhibitory control, and timing of behaviors. Currently, few interventions improve prefrontal function. Here, we tested whether stimulating the axons of prefrontal neurons in the striatum could compensate for deficits in temporal processing related to prefrontal dysfunction. We used an interval-timing task that requires working memory for temporal rules and attention to the passage of time. Our previous work showed that inactivation of the medial frontal cortex (MFC) impairs interval timing and attenuates ramping activity, a key form of temporal processing in the dorsomedial striatum (DMS). We found that 20-Hz optogenetic stimulation of MFC axon terminals increased curvature of time-response histograms and improved interval-timing behavior. Furthermore, optogenetic stimulation of terminals modulated time-related ramping of medium spiny neurons in the striatum. These data suggest that corticostriatal stimulation can compensate for deficits caused by MFC inactivation and they imply that frontostriatal projections are sufficient for controlling responses in time.

EVALUATING SHORT-TERM EXPOSURE TO WI-FI SIGNALS ON STUDENTS' REACTION TIME, SHORT-TERM MEMORY AND REASONING ABILITY.

This study investigated the effect of short-term exposure to Wi-Fi signals on the cognitive functions of the mind. After obtaining permission from the local Ethics Committee of Shiraz University of Medical Sciences and approval by the Iranian Registry of Clinical Trials (IRCT2017041233398N1), 45 male and female students from Shiraz University of Medical Sciences volunteered to participate in this study. They were exposed to Wi-Fi signals in two sham and exposure sessions, each for 2 hours. After completion, they took part in reaction time, short-term memory, and reasoning ability tests. After scoring, the data were analysed by SPSS software. In addition, the electric field strength and power density were calculated. The results showed no statistically significant differences between the mean scores of reaction time, short-term memory, and reasoning ability in sham and exposure. Also, the obtained values from the electric field strength and power density (E = 4.1 Vm-1, P = 0.446 Wm-2) were lower than that of threshold values by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Our results can greatly reduce concerns regarding the effects of short-term exposure to Wi-Fi waves on cognitive functions.

Improved neuropsychological outcomes following proton therapy relative to X-ray therapy for pediatric brain tumor patients.

BACKGROUND: Survivors of pediatric brain tumors are at risk for impaired development in multiple neuropsychological domains. The purpose of this study was to compare neuropsychological outcomes of pediatric brain tumor patients who underwent X-ray radiotherapy (XRT) versus proton radiotherapy (PRT). METHODS: Pediatric patients who underwent either XRT or PRT and received posttreatment age-appropriate neuropsychological evaluation-including measures of intelligence (IQ), attention, memory, visuographic skills, academic skills, and parent-reported adaptive functioning-were identified. Multivariate analyses were performed to assess differences in neuropsychological outcomes and included tests for interaction between treatment cohort and follow-up time. RESULTS: Between 1998 and 2017, 125 patients with tumors located in the supratentorial (17.6%), midline (28.8%), or posterior fossa (53.6%) compartments received radiation and had posttreatment neuropsychological evaluation. Median age at treatment was 7.4 years. The PRT patient cohort had higher estimated SES and shorter median time from radiotherapy completion to last neuropsychological evaluation (6.7 vs 2.6 y, P < 0.001). On multivariable analysis, PRT was associated with higher full-scale IQ (ß = 10.6, P = 0.048) and processing speed (ß = 14.4, P = 0.007) relative to XRT, with trend toward higher verbal IQ (ß = 9.9, P = 0.06) and general adaptive functioning (ß = 11.4, P = 0.07). Planned sensitivity analyses truncating follow-up interval in the XRT cohort re-demonstrated higher verbal IQ (P = 0.01) and IQ (P = 0.04) following PRT, with trend toward improved processing speed (P = 0.09). CONCLUSIONS: PRT is associated with favorable outcomes for intelligence and processing speed. Combined with other strategies for treatment de-intensification, PRT may further reduce neuropsychological morbidity of brain tumor treatment.

Prospective, longitudinal comparison of neurocognitive change in pediatric brain tumor patients treated with proton radiotherapy versus surgery only.

BACKGROUND: Proton radiotherapy (PRT) reduces the volume of normal tissue receiving radiation dose, which may lead to better neurocognitive outcomes. We examined change in neurocognitive scores over time in pediatric brain tumor patients treated with proton craniospinal irradiation (CSI), proton focal RT, or surgery only. METHODS: Patients received annual neurocognitive evaluations for up to 6 years. We examined Full Scale IQ (FSIQ), Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), and Processing Speed Index (PSI) scores. General linear mixed models examined change in scores over time by treatment group, adjusting for significant covariates. RESULTS: Scores from 93 patients treated between 2012 and 2017 (22 proton CSI, 31 proton focal, and 40 surgery only) were examined. Treatment groups were similar on gender (51.6% male), age at treatment (median = 9.7 y), and length of follow-up (median = 2.9 y). The surgery only group had proportionately more gliomas (P < 0.001), and the proton CSI group had more infratentorial tumors (P = 0.001) and higher total RT dose (P = 0.004). The proton focal and surgery only groups exhibited stable neurocognitive scores over time across all indexes (all P > 0.05). In the proton CSI group, WMI, PSI, and FSIQ scores declined significantly (P = 0.036, 0.004, and 0.017, respectively), while VCI and PRI scores were stable (all P > 0.05). CONCLUSIONS: Focal PRT was associated with stable neurocognitive functioning into survivorship. Outcomes were similar whether patients received focal PRT or no radiotherapy, even in neurocognitive domains known to be particularly radiosensitive. Proton CSI emerged as a neurocognitive risk factor, consistent with photon outcomes research.

Region-specific reduction of parvalbumin neurons and behavioral changes in adult mice following single exposure to cranial irradiation.

PURPOSE: Ionizing irradiation has several long-term effects including progressive cognitive impairment. Cognitive deterioration generally appears to be caused by abnormalities in the hippocampal dentate gyrus, with abnormal function of parvalbumin-expressing interneurons (PV neurons) in the cerebral cortex. PV neurons are vulnerable to oxidative stress, which can be caused by ionizing irradiation. We speculated that selective impairment of specific brain regions due to ionizing irradiation may alter the degree of cognitive impairment. METHODS: We irradiated mature mouse brains with 20 Gy-ionizing irradiation. Subsequently, we analyzed behavioral abnormalities and changes in the number of PV neurons. RESULTS: PV neuron density was significantly lower in some cortical regions of irradiated mice than in control mice. Within 1 week of irradiation, both body weight and temperature of irradiated mice decreased. In the forced swim test, irradiated mice spent significantly less time immobile than did control mice. However, irradiated mice did not display any abnormalities in the elevated plus maze test, Y-maze test, tail suspension test, and social interaction test between 3 to 6 days after irradiation. CONCLUSIONS: These results suggest that high-dose irradiation is less likely to cause brain dysfunction in the subacute phase. Moreover, the vulnerability of PV neurons appears to be brain-region specific.

Improving working memory and pain inhibition in older persons using transcranial direct current stimulation.

The aim of the present study was to examine whether transcranial Direct Current Stimulation (tDCS) could enhance working memory and pain inhibition in older persons. Fifteen volunteers (7 women, 8 men; mean ± SD: 64 ± 4.4 y.o.) participated in two tDCS sessions during which an n-back task was performed with two levels of working memory load, while painful stimulation was delivered at the ankle. The experiment included five within-subject counterbalanced conditions (pain alone and 0-back or 2-back with or without pain) performed twice during each session. Compared with the pre-tDCS baseline, anodal tDCS decreased response times and improved pain inhibition by working memory in the 2-back condition (p < 0.01), but not in the 0-back or pain alone conditions, while sham tDCS produced no effect (all p > 0.3). These results indicate that working memory and pain inhibition can be improved by tDCS in older persons.

Zinc Chloride Exposure Inhibits Brain Acetylcholine Levels, Produces Neurotoxic Signatures, and Diminishes Memory and Motor Activities in Adult Zebrafish.

In this study, we evaluated the acute (24, 48, 72, and 96 h) and chronic (21 days) adverse effects induced by low doses (0.1, 0.5, 1, and 1.5 mg/L) of zinc chloride (ZnCl2) exposure in adult zebrafish by using behavioral endpoints like three-dimensional (3D) locomotion, passive avoidance, aggression, circadian rhythm, and predator avoidance tests. Also, brain tissues were dissected and subjected to analysis of multiple parameters related to oxidative stress, antioxidant responses, superoxide dismutase (SOD), neurotoxicity, and neurotransmitters. The results showed that ZnCl2-exposed fishes displayed decreased locomotor behavior and impaired short-term memory, which caused an Alzheimer's Disease (AD)-like syndrome. In addition, low concentrations of ZnCl2 induced amyloid beta (amyloid ß) and phosphorylated Tau (p-Tau) protein levels in brains. In addition, significant induction in oxidative stress indices (reactive oxygen species (ROS) and malondialdehyde (MDA)), reduction in antioxidant defense system (glutathione (GSH), GSH peroxidase (GSH-Px) and SOD) and changes in neurotransmitters were observed at low concentrations of ZnCl2. Neurotoxic effects of ZnCl2 were observed with significant inhibition of acetylcholine (ACh) activity when the exposure dose was higher than 1 ppm. Furthermore, we found that zinc, metallothionein (MT), and cortisol levels in brain were elevated compared to the control group. A significantly negative correlation was observed between memory and acetylcholinesterase (AChE) activity. In summary, these findings revealed that exposure to ZnCl2 affected the behavior profile of zebrafish, and induced neurotoxicity which may be associated with damaged brain areas related to memory. Moreover, our ZnCl2-induced zebrafish model may have potential for AD-associated research in the future.

Continuous theta-burst stimulation over the dorsolateral prefrontal cortex inhibits improvement on a working memory task.

Theta-burst stimulation (TBS) over the dorsolateral prefrontal cortex (DLPFC) may be more effective for modulating cortical excitability compared to standard repetitive transcranial magnetic stimulation. However, the impact of intermittent (iTBS) and continuous TBS (cTBS) on working memory (WM) is poorly studied. The aim of our study was to compare the effects of iTBS and cTBS on WM over the left and right DLPFC. iTBS, cTBS or sham stimulation was administered over the right and left hemisphere of fifty-one healthy human subjects. WM was assessed before and after TBS using the 1-back, 2-back, and 3-back tasks. We found classical practice effects in the iTBS and the sham group: WM performance improved following stimulation as measured by the discriminability index. However, this effect could not be observed in the cTBS group. We did not find any hemisphere-dependent effects, suggesting that the practice effect is not lateralized, and TBS affects WM performance in a comparable manner if administered either over the left or the right hemisphere. We propose that our findings represent a useful addition to the literature of TBS-induced effects on WM. Moreover, these results indicate the possibility of clarifying processes underlying WM performance changes by using non-invasive brain stimulation.

TMS Over the Cerebellum Interferes with Short-term Memory of Visual Sequences.

Growing evidence suggests that the cerebellum is not only involved in motor functions, but it significantly contributes to sensory and cognitive processing as well. In particular, it has been hypothesized that the cerebellum identifies recurrent serial events and recognizes their violations. Here we used transcranial magnetic stimulation (TMS) to shed light on the role of the cerebellum in short-term memory of visual sequences. In two experiments, we found that TMS over the right cerebellar hemisphere impaired participants' ability to recognize the correct order of appearance of geometrical stimuli varying in shape and/or size. In turn, cerebellar TMS did not affect recognition of highly familiar short sequences of letters or numbers. Overall, our data suggest that the cerebellum is involved in memorizing the order in which (concatenated) stimuli appear, this process being important for sequence learning.

Single transcranial direct current stimulation in schizophrenia: Randomized, cross-over study of neurocognition, social cognition, ERPs, and side effects.

Over the last decades, the treatment of schizophrenia has shifted fundamentally from a focus on symptom reduction to a focus on recovery and improving aspects of functioning. In this study, we examined the effect of transcranial direct current stimulation (tDCS) on social cognitive and nonsocial neurocognitive functions, as well as on electroencephalogram (EEG) measures, in individuals with schizophrenia. Thirty-seven individuals with schizophrenia were administered one of three different tDCS conditions (cathodal, anodal, and sham) per visit over the course of three visits, with approximately one week between each visit. Order of conditions was randomized and counterbalanced across subjects. For the active conditions, the electrode was placed over the left dorsolateral prefrontal cortex with the reference electrode over right supraorbital cortex. Current intensity was 2 mA and was maintained for two 20-minute sessions, with a one hour break between the sessions. Assessments were conducted immediately following each session, in a counterbalanced order of administration. No systematic effects were found across the social and nonsocial cognitive domains, and no significant effects were detected on event-related potentials (ERPs). The very small effect sizes, further validated by post-hoc power analyses (large Critical Ns), demonstrated that these findings were not due to lack of statistical power. Except for mild local discomfort, no significant side effects were reported. Findings demonstrate the safety and ease of administration of this procedure, but suggest that a single dose of tDCS over these areas does not yield a therapeutic effect on cognition in schizophrenia. TRIAL REGISTRATION: ClinicalTrials.gov NCT02539797.

Improved cognitive morning performance in healthy older adults following blue-enriched light exposure on the previous evening.

OBJECTIVES: Exposure to light can have acute alerting and circadian phase-shifting effects. This study investigated the effects of evening exposure to blue-enriched polychromatic white (BEL) vs. polychromatic white light (WL) on sleep inertia dissipation the following morning in older adults. METHODS: Ten healthy older adults (average age = 63.3 yrs; 6F) participated in a 13-day study comprising three baseline days, an initial circadian phase assessment, four days with 2-h evening light exposures, a post light exposure circadian phase assessment and three recovery days. Participants were randomized to either BEL or WL of the same irradiance for the four evening light exposures. On the next mornings at 2, 12, 22 and 32 min after each wake time, the participants completed a 90-s digit-symbol substitution test (DSST) to assess working memory, and objective alertness was assessed using a wake EEG recording. DSST and power density from the wake EEG recordings were compared between the two groups. RESULTS: DSST performance improved with time awake (p < 0.0001) and across study days in both light exposure groups (p < 0.0001). There was no main effect of group, although we observed a significant day x group interaction (p = 0.0004), whereby participants exposed to BEL performed significantly better on the first two mornings after light exposures than participants in WL (post-hoc, p < 0.05). On those days, the BEL group showed higher EEG activity in some of the frequency bins in the sigma and beta range (p < 0.05) on the wake EEG. CONCLUSION: Exposure to blue-enriched white light in the evening significantly improved DSST performance the following morning when compared to polychromatic white light. This was associated with a higher level of objective alertness on the wake EEG, but not with changes in sleep or circadian timing.

Effects of 1H + 16O Charged Particle Irradiation on Short-Term Memory and Hippocampal Physiology in a Murine Model.

Radiation from galactic cosmic rays (GCR) poses a significant health risk for deep-space flight crews. GCR are unique in their extremely high-energy particles. With current spacecraft shielding technology, some of the predominant particles astronauts would be exposed to are 1H + 16O. Radiation has been shown to cause cognitive deficits in mice. The hippocampus plays a key role in memory and cognitive tasks; it receives information from the cortex, undergoes dendritic-dependent processing and then relays information back to the cortex. In this study, we investigated the effects of combined 1H + 16O irradiation on cognition and dendritic structures in the hippocampus of adult male mice three months postirradiation. Six-month-old male C57BL/6 mice were irradiated first with 1H (0.5 Gy, 150 MeV/n) and 1 h later with 16O (0.1 Gy, 600 MeV/n) at the NASA Space Radiation Laboratory (Upton, NY). Three months after irradiation, animals were tested for hippocampus-dependent cognitive performance using the Y-maze. Upon sacrifice, molecular and morphological assessments were performed on hippocampal tissues. During Y-maze testing, the irradiated mice failed to distinguish the novel arm, spending approximately the same amount of time in all three arms during the retention trial relative to sham-treated controls. Irradiated animals also showed changes in expression of glutamate receptor subunits and synaptic density-associated proteins. 1H + 16O radiation compromised dendritic morphology in the cornu ammonis 1 and dentate gyrus within the hippocampus. These data indicate cognitive injuries due to 1H + 16O at three months postirradiation.

Evoked bioelectrical brain activity following exposure to ionizing radiation. / VYKLYKANA BIOELEKTRYChNA AKTYVNIST' GOLOVNOGO MOZKU PISLIa VPLYVU IONIZUIuChOÏ RADIATsIÏ.

The article provides an overview of modern physiological evidence to support the hypothesis on cortico limbic sys tem dysfunction due to the hippocampal neurogenesis impairment as a basis of the brain interhemispheric asym metry and neurocognitive deficit after radiation exposure. The importance of the research of both evoked poten tials and fields as a highly sensitive and informative method is emphasized.Particular attention is paid to cerebral sensor systems dysfunction as a typical effect of ionizing radiation. Changes in functioning of the central parts of sensory analyzers of different modalities as well as the violation of brain integrative information processes under the influence of small doses of ionizing radiation can be critical when determining the radiation risks of space flight. The possible long term prospects for manned flights into space, including to Mars, given the effects identified are discussed. Potential risks to the central nervous system during space travel comprise cognitive functions impairment, including the volume of short term memory short ening, impaired motor functions, behavioral changes that could affect human performance and health. The remote risks for CNS are considered to be the following possible neuropsychiatric disorders: accelerated brain aging, Alzheimer's disease and other types of dementia. The new radiocerebral dose dependent effect, when applied cog nitive auditory evoked potentials P300 technique with a possible threshold dose of 0.05 Gy, manifesting in a form of disruption of information processing in the Wernicke's area is under discussion. In order to identify neurophys iological biological markers of ionizing radiation further international researches with adequate dosimetry support are necessary.