NOTE: End date changed to 5/01/2022 per NSSC info (Ed., 11/30/20)

NOTE: End date changed to 12/31/2020 per NSSC info (Ed., 11/12/19)

Ed. NOTE (April 2016): Proposal modified from original NSCOR proposal, per Space Radiation Element; not an NSCOR project

These studies will be conducted in a rat model that is relatively unique in that the rats are exercised regularly, and are preselected for a high level of executive function performance (high cognitive reserved) prior to space radiation exposure. Such a model system more closely resembles the physical and cognitive reserve of astronauts, and addresses a key operational issue of whether space radiation exposure will impact previously imprinted cognitive skills.

Specifically, these studies will determine the impact that mission-relevant doses of space radiation (Z<15 single ion exposures, in addition to the multi-ion GCRSim) have on advanced executive functions, specifically Attentional Set Shifting (ATSET) and creative problem solving, or unconstrained cognitive flexibility (UCFlex).

This data can be used to address Risk of Adverse Cognitive or Behavioral Conditions and Psychiatric Disorders Bmed Gap 102 [previously central nervous system (CNS) Gap 2], and determine the likelihood of astronauts being able to successfully conduct neurocognitive (problem-solving) tasks. This study will also determine whether the incidence and/or severity of executive function impairments would be altered by exposure to another frequent flight stressor, insufficient sleep [Bmed-107 and Bmed-108, formerly CNS Gap 8]. A key component of these studies is an assessment of inter-individual susceptibility to develop deficits in these two cognitive processes following space radiation exposure (with or without the additional sleep stressor). Such data can be used (by others) to determine the best approach to develop a population Threshold Dose for dose risk estimations [Bmed-102 and Bmed-107, formerly CNS Gap 3]. [Ed. note October 2020: Human Research Program (HRP) gaps have changed with Integrated Research Plan Rev L such that gaps listed previously have been merged into newer gaps, as noted]

Initially, three hypotheses were tested by the studies covered by this grant.

1. Sleep perturbation reduces the ability of rats to perform executive functions, and will be especially pronounced in space radiation (SR)-irradiated rats.

2. Sleep perturbation alters the sensitivity of the brain to develop SR-induced cognitive impairment.

3. SR irradiation alters Delta and Theta wave activity (EEG), and that these SR-induced changes in EEG activity are the underlying cause of the impairment of executive function performance.

In 2019, we received supplemental funding (an HRP-IWS Graduate Fellowship) to develop the technical capability to simultaneously assess neural activity in multiple brain regions (neural network activity) of rats that are actively engaged in cognitive flexibility tasks, and how sleep fragmentation impacts neural network cohesiveness.

In 2020, we received further supplemental funding (an HRP-IWS Graduate Fellowship) to establish whether sleep fragmentation exacerbates SR-induced deficits in fine motor skills.

Due to ongoing restrictions imposed by the Governor of Virginia, only two staff members were allowed to work in the laboratories at EVMS. Thus, the amount of rats that could be processed in the sleep/attentional set shifting (ATSET) interaction study was significantly reduced (to just 2 rats/week). Three medical students at Eastern Virginial Medical School (EVMS) volunteered in the Britten lab after hours, allowing some studies on the impact that sleep perturbations had on fine motor skills and performance in a high cognitive task load (CTL) “ARMIT” test. The ARMIT task is designed to evaluate executive functioning, working memory, cognitive flexibility, and long-term memory in the face of interference (stress loading).

During this reporting period, we have demonstrated that sleep perturbation:

1. Reveals latent deficits in CDR-stage performance (ATSET) in rats exposed to 10 cGy of simulated Galactic Cosmic Radiation (GCR).

2. Leads to additional loss of string pulling (fine motor skills) performance over that observed in space radiation (10 cGy of GCR or He) exposed rats.

3. Leads to loss of performance in the C.1.3. high CTL stage of the ARMIT test (preliminary) by decreasing anterograde interference in radiation naive rats.

We have also acquired local field potential (LFP) readings (a direct measure of activity) from two brain regions as rats perform in low and high CTL tasks, and determined how LFP outputs are synchronized as the rats performs in the various tasks. Ongoing analyses are now correlating these observed changes in LFP signal output to specific events/responses in the various tasks.

Abstracts. 2021 NASA Human Research Program Investigators' Workshop, Virtual, February 1-4, 2021. , Feb-2021

NOTE: End date changed to 12/31/2020 per NSSC info (Ed., 11/12/19)

Ed. NOTE (April 2016): Proposal modified from original NSCOR proposal, per Space Radiation Element; not an NSCOR project

These studies will be conducted in a rat model that is relatively unique in that the rats are exercised regularly, and are preselected for a high level of executive function performance (high cognitive reserved) prior to space radiation exposure. Such a model system more closely resembles the physical and cognitive reserve of astronauts, and addresses a key operational issue of whether space radiation exposure will impact previously imprinted cognitive skills.

Specifically, these studies will determine the impact that mission-relevant doses of space radiation (Z<15 single ion exposures, in addition to the multi-ion GCRSim) have on advanced executive functions, specifically Attentional Set Shifting (ATSET) and creative problem solving (UCFlex).

This data can be used to address Risk of Adverse Cognitive or Behavioral Conditions and Psychiatric Disorders Bmed Gap 102 [previously central nervous system (CNS) Gap 2], and determine the likelihood of Astronauts being able to successfully conduct neurocognitive (problem-solving) tasks. This study will also determine whether the incidence and/or severity of executive function impairments would be altered by exposure to another frequent flight stressor, insufficient sleep [Bmed-107 and Bmed-108, formerly (CNS Gap 8)]. A key component of these studies is an assessment of inter-individual susceptibility to develop deficits in these two cognitive processes following space radiation exposure (with or without the additional sleep stressor). Such data can be used (by others) to determine the best approach to develop a population Threshold Dose for dose risk estimations [Bmed-102 and Bmed-107, formerly (CNS Gap 3)]. [Ed. note October 2020: Human Research Program (HRP) gaps have changed with Integrated Research Plan Rev L such that gaps listed previously have been merged into newer gaps, as noted]

Initially, three hypotheses were tested by the studies covered by this grant.

1. Sleep perturbation reduces the ability of rats to perform executive functions, and will be especially pronounced in space radiation (SR)-irradiated rats.

2. Sleep perturbation alters the sensitivity of the brain to develop SR-induced cognitive impairment.

3. SR irradiation alters Delta and Theta wave activity (EEG), and that these SR-induced changes in EEG activity are the underlying cause of the impairment of executive function performance.

In 2019, we received supplemental funding (an HRP-IWS Graduate Fellowship) to develop the technical capability to simultaneously assess neural activity in multiple brain regions (neural network activity) of rats that are actively engaged in cognitive flexibility tasks, and how sleep fragmentation impacts neural network cohesiveness.

In 2020, we received further supplemental funding (an HRP-IWS Graduate Fellowship) to establish whether sleep fragmentation exacerbates SR-induced deficits in fine motor skills.

Over the last two years, studies were conducted that determined whether SR-exposed male rats differ in their problem solving ability following sleep perturbation compared to non-irradiated rats subjected to the same sleep stress. Irradiated rats with apparently normal problem solving performance (in the attentional set shifting (ATSET) assay), and unirradiated rats, were thus subjected to sleep perturbation and reassessed for ATSET performance the following day. Sleep perturbation resulted in 10% of the sham rats performing badly in all stages of the ATSET test, with the exception of the IDS stage where 30% of the sham rats performed badly. In contrast, sleep perturbation resulted in 40-50% of the irradiated rats under-performing in the IDS, IDR, EDS, and EDR stages of the test, despite them previously having good performance when not sleep deprived. Importantly set shifting performance (IDS, IDR, EDS, and EDR stages) performance has rarely been shown to be impacted by SR. The same observations were made in male rats exposed to 5 cGy 600 MeV/n 28Si ions (Britten et al., 2020) and to 18 cGy of 252Cf-generated neutrons delivered over 6 months (Britten et al., 2019). This “unmasking” of latent ASTET deficit suggest that the true impact of SR on cognitive impairment (and possibly other processes) may not be fully evident in normally rested rats.

A worrying aspect of these studies is that sleep perturbation appears to have a bigger impact on ATSET performance in irradiated rats than in non-irradiated rats. This raises the possibility that irradiated individuals may have a generalized issue in task performance (even sensorimotor based tasks) under sub-optimal sleep conditions.

Over the last year our studies have evolved to expand the scope of investigation to include female rats and to assess whether sleep fragmentation would exacerbate any cognitive impairment induced by the simulated GCR beam. While some progress has been made in these areas, the COVID-related shutdown at Eastern Virginia Medical School (EVMS) drastically reduced the amount of data that could be generated from the batch of prescreened rats that were irradiated at NASA Space Radiation Laboratory (NSRL) in the Fall of 2019, while the COVID-related shutdown of Brookhaven National Laboratory (BNL)/NSRL in April 2020 prevented that cohort of prescreened (male and female) rats being irradiated.

The data we were able to generate does show that female rats are susceptible to SR-induced impairments in ATSET performance. This is in stark contrast to some mouse studies that suggest that GCR exposure did not impact Novel Object Recognition memory in female mice but that male mice had severely impaired performance. Our data does indicate that there are some stages within the ATSET test where males show bigger performance decrements than females, but there are others (specifically the Compound Discrimination stage) where 3-fold more females than males have severe performance decrements. The very limited data on the exacerbating impact of sleep perturbation on ATSET performance in GCR exposed rats suggests that qualitatively there is the same “unmasking” of latent deficits by sleep fragmentation as we have observed with other ions in males, and possibly in female rats. However, further data is needed before a definitive conclusion can be made on this matter. There were some major technological advances in our studies that are assessing the exacerbating impact of sleep fragmentation and/or SR on neural network cohesion while the rats are actively performing executive functions.

Six sham and 6 He-exposed rats were implanted with electrodes after returning from NSRL and local field potential (LFP) readings were obtained from 2 sham and 3 He-exposed rats while they performed in our newly developed Associative Recognition Memory Interference Touchscreen (ARM-IT) test. We have shown that it is possible (using a wireless back-pack transmitter) to get concurrent LFP recordings from nodes (Hpc, amygdala, mPFC) within the cortico-limbic (CLN) network in rats under cognitive loading, and to perform cross correlation analysis to assess functional connectivity between these nodes.

We also developed the technical capability to generate electronic time stamps from the touchscreen apparatus (when specific events occurred) and incorporate these as part of the LFP output signals. Using such time stamps it is now possible to accurately assess the functional connectivity between nodes when the rats are performing specific responses within the ARM-IT task. For example, this “electronic mind” can establish the LFP signature from 3 brain regions when the rat “notices” that the “target” is activated on the touchscreen and just prior to pressing the correct or incorrect “target.” These studies were curtailed when EVMS (and Norfolk State University-- who are responsible for the LFP data analysis) operations were shut down in April 2020 in response to the COVID pandemic.

Similarly, our proposed plans to assess the impact of sleep fragmentation on the incidence and severity of SR-induced impairment of fine motor skills were also suspended with the shutdown of operations at NSRL in April 2020.

Abstracts. 2020 NASA Human Research Program Investigators’ Workshop, Galveston, TX, January 27-30, 2020. , Jan-2020

Ed. NOTE (April 2016): Proposal modified from original NSCOR proposal, per Space Radiation Element; not an NSCOR project

We receive a Fellowship award to develop the technical capability of measuring neural network functionality (theta wave coherence) in real time as rats perform a cognitive task.

This study will establish the impact that SlpDep/SlpFrag has on the severity of HIIEF (CNS 8), and whether Hadron exposure will result in a diminished ability to restore SlpDep decrements in Executive Function (CNS Gap 8).

The proposed studies will thus generate data on the likelihood that GCR (galactic cosmic radiation) exposure will result in the impairment of neurocognitive (Executive Function) tasks that will be absolutely vital for the successful completion of a deep-space mission, under conditions that are more representative of the actual mission (when individuals are suffering from perturbed sleep).

Aim 1: Studies to determine the Impact of sleep-fragmentation on Attentional Set Shifting performance.

Aim 2: Studies to determine the Impact of sleep fragmentation occurring at pre- or post-HZE exposure on Attentional Set Shifting performance.

Aim 3: Studies to determine the Impact of HZE exposure on sleep related electroencephalogram (EEG), and sleep homeostasis.

This project will determine whether sleep perturbation alters the severity of the SR-induced impairment of problem solving performance. The SR ion primarily used in these studies was 600 MeV/n 28Si (400 MeV/n 4He ions have also been used but the data from those studies is too preliminary to report at present). This study will also determine the relative severity of the SR-induced and sleep-perturbation-induced decrements in problem solving ability.

Over the last year, studies were conducted that determined whether SR-irradiated rats differ in their problem solving ability following sleep perturbation compared to non-irradiated rats subjected to the same sleep stress. Irradiated rats with apparently normal problem solving performance (in the attentional set shifting (ATSET) assay), and unirradiated rats, were subjected to sleep perturbation and reassessed for ATSET performance the following day. Sleep perturbation resulted in 10% of the sham rats performing badly in all stages of the ATSET test, with the exception of the IDS stage where 30% of the sham rats performed badly. In contrast, sleep perturbation resulted in 40-50% of the irradiated rats under-performing in the IDS, IDR, EDS, and EDR stages of the test, despite them previously having good performance when not sleep deprived. Sleep perturbation appears to have a bigger impact on ATSET performance in irradiated rats than in unirradiated rats. Thus, the true impact of SR cognitive impairment may not be fully evident in normally rested rats.

Inadequate sleep leads to marked levels of inflammation within the brain. Such changes could change the response of the brain to SR irradiation. Another series of experiments were conducted to determine whether the frequency and/or severity of SR-induced cognitive impairment differs in rats that have been fully rested to prior irradiation, or have been subjected to sleep perturbation. With respect to ATSET performance, the only measureable impact of sleep perturbation prior to SR exposure was a decrease in the speed with which the irradiated rats completed IDS, a task regulated by the anterior and posterior cingulate cortex.

We also investigated the impact that prior sleep perturbation had on insightful (creative) problem solving as assessed by the Unconstrained Cognitive Flexibility (UCFlex) test. Exposure to 1, 5, and 10 cGy 600 MeV/n 28Si resulted in a significant reduction in the number of rats that could solve the UCFlex task, and increased the time it took the rats to solve the UCFlex task. In contrast, the UCFlex performance of the rats that were sleep perturbed prior to irradiation was indistinguishable from the shams. We observed a similar protection by prior sleep perturbation in rats exposed to 10 cGy 400 MeV/n 4He, although we have insufficient numbers to include in this report according to NASA guidelines. We plan to repeat both the Si and He studies in the next grant reporting period.

We are currently investigating whether the sleep perturbation has altered the composition of the proteome of the temporal lobe, perhaps invoking some free radical scavengers, or activating glial cells and astrocytes. The other possibility we are exploring is that the rats that have been sleep perturbed prior to irradiation, rapidly fall asleep after being irradiated, while the non-sleep perturbed rats remain awake and active in their cages for 12 hours. It is possible that the reduced EEG and metabolic activity within the temporal lobe of the rats that fall immediately asleep, may reduce the deleterious effects of the SR exposure.

The final aspect of our studies has been to determine whether SR-exposure impacts EEG activity (delta and theta wave activity), and the sleep homeostatic response. SR alters EEG of the brain, and we have discovered that the severity of these changes may be reduced in rats that are resilient to stress. Astronauts are selected to be highly stress resilience and thus may be less susceptible to SR effects than individuals that are more easily stressed.

As part of these studies we have now developed the technical ability to simultaneously measure activity within multiple brain regions in real-time as the rats perform in a cognitive task. Preliminary data suggest that SR alters the coordination of theta wave between different brain regions.

ICRR 2019 program. 2019 International Congress of Radiation Research, Manchester, UK, August 25-29, 2019. , Aug-2019

IWS program. 2019 NASA Human Research Program Investigators’ Workshop, Galveston, TX, January 22-25, 2019. , Jan-2019

This study will establish the impact that SlpDep/SlpFrag has on the severity of HIIEF (CNS 8), and whether Hadron exposure will result in a diminished ability to restore SlpDep decrements in Executive Function (CNS Gap 8).

The proposed studies will thus generate data on the likelihood that GCR (galactic cosmic radiation) exposure will result in the impairment of neurocognitive (Executive Function) tasks that will be absolutely vital for the successful completion of a deep-space mission, under conditions that are more representative of the actual mission (when individuals are suffering from perturbed sleep).

Aim 1: Studies to determine the Impact of sleep-fragmentation on Attentional Set Shifting performance.

Aim 2: Studies to determine the Impact of sleep fragmentation occurring at pre- or post-HZE exposure on Attentional Set Shifting performance.

Aim 3: Studies to determine the Impact of HZE exposure on sleep related electroencephalogram (EEG), and sleep homeostasis.

This project will determine whether sleep perturbation alters the severity of the GCR-induced impairment of problem solving performance. The GCR ion primarily used in these studies was 600 MeV/n 28Si (400 MeV/n 4He ions have also been used but the data from those studies is too preliminary to report at present). This study will also determine the relative severity of the GCR-induced and sleep-perturbation-induced decrements in problem solving ability.

Over the last year, studies were conducted that determined whether GCR-irradiated rats differ in their problem solving ability following sleep perturbation compared to non-irradiated rats subjected to the same sleep stress. Irradiated rats with apparently normal problem solving performance (in the attentional set shifting (ATSET) assay), and unirradiated rats, were subjected to sleep perturbation and reassessed for ATSET performance the following day. Sleep perturbation resulted in 10% of the sham rats performing badly in all stages of the ATSET test, with the exception of the IDS stage where 30% of the sham rats performed badly. In contrast, sleep perturbation resulted in 40-50% of the irradiated rats under-performing in the IDS, IDR, EDS, and EDR stages of the test, despite them previously having good performance when not sleep deprived. Sleep perturbation appears to have a bigger impact on ATSET performance in irradiated rats than in unirradiated rats. Thus, the true impact of GCR cognitive impairment may not be fully evident in normally rested rats.

Inadequate sleep leads to marked levels of inflammation within the brain. Such changes could change the response of the brain to GCR irradiation. Another series of experiments were conducted to determine whether the frequency and/or severity of GCR-induced cognitive impairment differs in rats that have been fully rested to prior irradiation, or have been subjected to sleep perturbation. With respect to ATSET performance, the only measureable impact of sleep perturbation prior to GCR exposure was a decrease in the speed with which the irradiated rats completed IDS, a task regulated by the anterior and posterior cingulate cortex.

We also investigated the impact that prior sleep perturbation had on insightful (creative) problem solving as assessed by the Unconstrained Cognitive Flexibility (UCFlex) test. Exposure to 1, 5, and 10 cGy 600 MeV/n 28Si resulted in a significant reduction in the number of rats that could solve the UCFlex task, and increased the time it took the rats to solve the UCFlex task. In contrast, the UCFlex performance of the rats that were sleep perturbed prior to irradiation was indistinguishable from the shams. We observed a similar protection by prior sleep perturbation in rats exposed to 10 cGy 400 MeV/n 4He, although we have insufficient numbers to include in this report according to NASA guidelines. We plan to repeat both the Si and He studies in the next grant reporting period.

We are currently investigating whether the sleep perturbation has altered the composition of the proteome of the temporal lobe, perhaps invoking some free radical scavengers, or activating glial cells and astrocytes. The other possibility we are exploring is that the rats that have been sleep perturbed prior to irradiation, rapidly fall asleep after being irradiated, while the non-sleep perturbed rats remain awake and active in their cages for 12 hours. It is possible that the reduced EEG and metabolic activity within the temporal lobe of the rats that fall immediately asleep, may reduce the deleterious effects of the GCR exposure. During the next reporting period we will establish whether keeping the sleep-perturbed rats awake after irradiation changes the UCFlex performance.

The final aspect of our studies will determine how GCR-exposure impacts EEG activity (delta and theta wave activity), and the sleep homeostatic response. The first batch of rats are scheduled to be irradiated in October 2017.

This study will establish the impact that SlpDep/SlpFrag has on the severity of HIIEF (CNS 8), and whether Hadron exposure will result in a diminished ability to restore SlpDep decrements in Executive Function (CNS Gap 8).

The proposed studies will thus generate data on the likelihood that GCR (galactic cosmic radiation) exposure will result in the impairment of neurocognitive (Executive Function) tasks that will be absolutely vital for the successful completion of a deep-space mission, under conditions that are more representative of the actual mission (when individuals are suffering from perturbed sleep).

Aim 1: Studies to determine the Impact of sleep-fragmentation on Attentional Set Shifting performance.

Aim 2: Studies to determine the Impact of sleep fragmentation occurring at pre- or post-HZE exposure on Attentional Set Shifting performance.

Aim 3: Studies to determine the Impact of HZE exposure on sleep related electroencephalogram (EEG), and sleep homeostasis.

NASA funds arrived at Eastern Virginia Medical School (EVMS) on April 8 2016. Upon receipt of funds, the documentation to hire the two research assistants was initiated. Two candidates were employed effective July 1 2016.

Final IACUC (Institutional Animal Care and Use Committee) approval to cover the work outlined in this proposal was awarded on April 4 2016 and forwarded to NASA on April 29 2016.

The Sleep Deprivation apparatus from Lafayette Instruments were ordered in June 2016 and arrive mid-August 2016.

On July 19 2016, 110 rats arrived at EVMS and began the pre-screening protocol. 80 of these rats are predicted to have sufficient Attentional Set Shifting performance to be shipped to Brookhaven National Laboratory (BNL) and irradiated (with and without sleep deprivation) between November 3 and Nov 9, 2106. We anticipate to have data from these rats by the end of Feb 2017.

We plan to prescreen a further 80 rats in Feb/March of 2017 and irradiate them at BNL April/May 2017.

This study will establish the impact that SlpDep/SlpFrag has on the severity of HIIEF (CNS 8), and whether Hadron exposure will result in a diminished ability to restore SlpDep decrements in Executive Function (CNS Gap 8).

The proposed studies will thus generate data on the likelihood that GCR (galactic cosmic radiation) exposure will result in the impairment of neurocognitive (Executive Function) tasks that will be absolutely vital for the successful completion of a deep-space mission, under conditions that are more representative of the actual mission (when individuals are suffering from perturbed sleep).

Aim 1: Studies to determine the Impact of sleep-fragmentation on Attentional Set Shifting performance.

Aim 2: Studies to determine the Impact of sleep fragmentation occurring at pre- or post-HZE exposure on Attentional Set Shifting performance.

Aim 3: Studies to determine the Impact of HZE exposure on sleep related electroencephalogram (EEG), and sleep homeostasis.

(Ed. note 4/7/2016: Proposal modified from original NSCOR solicitation proposal; not an NSCOR project)