Zone Preference in the Visual Water Maze
June 26, 2025
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The National Institutes of Health (NIH) awards the grants through 24 grant-awarding institutes and centers for biomedical and public health research. Early-career academic scientists are most likely to be interested in research project grants, fellowships, and career development awards. As a young scientist doing research directly related to human health, you need to know your way around the NIH grants and funding programs that provide intramural and extramural support of $31 billion in research annually. NIH programs help prepare individuals for careers in biomedical, behavioral, social, and clinical research in times when the research in the past few decades has escalated beyond reach, as per the Tuft Center for the study of Drug Development (Collier, 2009).
The NIH grant awards are divided into four major categories; Research Grants (R series), Research Training and Fellowships (T & F series), Career Development Awards (K series), and Program Project/Center Grants (P series), besides various other programs with various requirements. In 1998, 24,100 grant applications were received, and 7,500 were funded, making it a total of $1.9 billion. By 2005, the number of applications was increased to 43,000, of which 9,600 were funded, making it a total of $3.4 billion. In 2015, 52,000 applications were received, and 9,500 were funded with a total of $4.3 billion. Additionally, NIH received 2097 new proposals in 2010, of which only 355 managed to receive funding. (McGovern, 2012).
This article takes you through the complete application procedure for the R01 grant with a comprehensive subject introduction and process guidance every step of the way.
Among numerous NIH grants and funding programs, R-series provides funding support for biomedical research projects. There are many categories in R-series grant funding, such as R01, R03, and R21 programs. These mechanisms provide different grant support to a specific type of project. An R01 is the most common and oldest funding mechanism for health research and development projects undertaken by one or more named investigator(s) in an area of specific interest and competence. The funding mechanism of R01 is the common source of NIH funding for independent investigators that can help establish your research career. You can request up to $250,000 per year in direct costs through the modular budget format in 5 years funding provision.
In 2016, 26,187 applications were submitted to NIH for R01 grants. 17.3% were funded, making it a total of $2.2 billion. $460,000 was the average annual budget for the year.
The following guidance is intended to assist you in the process of developing a strong application that stands a chance of better reviewer evaluation on the grounds of science and merit of your proposal. Reviewing archives of successful applications can help you extraordinarily, particularly if they share the grant mechanism, design, or area. (Karina et al., 2007)
Peer Reviewers Expectation
Understanding your application review criteria can help you build a good application. During the peer review process, there is a panel of non-federal scientists who review your application through multidimensional standards.
The following segments explain the principles reviewers employ to evaluate applications.
Overall Impact
In consideration of the resulting review criteria, reviewers provide an overall impact score based on their assessment of the project probability for compelling influence on the research field(s) involved.
Scored Review Criteria
Reviewers consider the following measures to determine the scientific and technical merit of your proposal and score accordingly.
Research Resources
Sufficient demonstration of the high quality of PD/PI, the co-investigators, available expertise, resources, applicant institution, and its support of the project is the key to navigate the peer review process successfully. Applicants should be very clear about their inventory of appropriate resources, laboratory space, and equipment to carry out the research.
Cover Letters
This is your only opportunity to have any say on the reviewer panel subject. Give names of any reviewers that should not be on board on the grounds of a possible conflict of interest or area of research. Reviewers are not allowed any access to your assignment request and cover letter.
Be very specific about the assignment request in your cover letter or the assignment request form. Follow guide instructions to determine your request options as well as information selection appropriate to go in the cover letter. Reviewers with proficiency in your field will immediately recognize the potential for your research.
Budget Development
This step takes the most deliberate contemplation and time in the application writing process.
Understand the various mechanisms to determine what is the necessary budget type required to be submitted with your application (stated in your FOA) in cooperation with your institution’s central grants bureau and department administrator.
For additional information, visit The Comprehensive Budget Guide provided by NIH.
Research Plan
The research plan defines your proposed research by listing its significance and conduct process. Be conscious of your audience divide throughout the procedure that only a small number of reviewers will be acquainted with your field techniques, and the majority of them will probably have no idea. To you, every member of the reviewer panel is equally important because each reviewer will get one vote.
The assigned reviewers advocate you in managing the review panel discussion of your application, which makes it imperative for you to win them over in order to succeed in peer review. Write and develop your application in a readily grasping manner that self-explains the proposed gist to the primary reviewer. Appeal to the reviewers and funding ICs in a language that enhances the importance of your anticipated project.
Once you have planned and researched, now it’s time to write. A well-written application is fundamental to success.
Be realistic. Don’t overestimate and propose work that can’t be practically done during the project period. Make sure your personnel has suitable scientific proficiency and training. Make sure your proposed budget is reasonable and justified.
Reviewers are habituated to looking for information in the exact sections of the application form. Start with a framework subsequent to the suggested body of the application. The perceptual dynamics of the application should be straightforward to follow.
Start with a clear subject sentence for each paragraph, along with one main idea. Strive for excellent readability key. A reviewer often reads 10-15 thorough applications in a single setting, so the best chance at success for your application is easy-to-read and well-written.
Make a case that instantly captures the reviewers’ attention to why NIH should finance your research. Include sufficient background information to allow a reader with a clear understanding of your proposed work. Support your idea with expert collaborators to assist the project further.
You have possibly been working on the same words and paragraphs repeatedly, allow fresh eyes to go through your content, and check punctuation, and content flow. Rectify each typographical, grammatical and spelling error or untidy formatting. A disorganized application may lead reviewers to the conclusion of similar disorganized research.
Make yourself familiar with format requirements, such as font and spacing before submitting your application and brand sections as directed. Prior to submission, take a good look at the entire grant application one last time. Keep in mind; that you want a convincing proposal that is formatted according to the guidelines, error-free and straightforward.
Note: NIH Systems automatically add headers, footers, time stamping, tracking number, FOA number, and page numbers upon submission. Therefore, do not include any of them.
At this stage, your application should have achieved the following:
Submission Process Overview
Grants.gov performs some basic application checks after you submit your application to detect a justifiable problem that can have your application rejected with a “Rejected with Errors” status. If it happens, you must check eRA Commons for the status of your application. eRA provides a list of errors and warnings that you must address and resubmit. If no problem is found on a basic check, Grants.gov directs your application to agency recovery for eRA to pick up your error-free application. eRA then generates an associated document of all your submissions to post an application image for 2 business days in eRA Commons Status for you to view. The viewing window allows you to check your assembled application and inform the eRA service desk of any missing attachment or text.
Submit & Track
It is advised to submit your application at least 2 days before the due date in order to have enough time for application tracking and error correction to view your application image by the due date.
In behavioral neuroscience, the Open Field Test (OFT) remains one of the most widely used assays to evaluate rodent models of affect, cognition, and motivation. It provides a non-invasive framework for examining how animals respond to novelty, stress, and pharmacological or environmental manipulations. Among the test’s core metrics, the percentage of time spent in the center zone offers a uniquely normalized and sensitive measure of an animal’s emotional reactivity and willingness to engage with a potentially risky environment.
This metric is calculated as the proportion of time spent in the central area of the arena—typically the inner 25%—relative to the entire session duration. By normalizing this value, researchers gain a behaviorally informative variable that is resilient to fluctuations in session length or overall movement levels. This makes it especially valuable in comparative analyses, longitudinal monitoring, and cross-model validation.
Unlike raw center duration, which can be affected by trial design inconsistencies, the percentage-based measure enables clearer comparisons across animals, treatments, and conditions. It plays a key role in identifying trait anxiety, avoidance behavior, risk-taking tendencies, and environmental adaptation, making it indispensable in both basic and translational research contexts.
Whereas simple center duration provides absolute time, the percentage-based metric introduces greater interpretability and reproducibility, especially when comparing different animal models, treatment conditions, or experimental setups. It is particularly effective for quantifying avoidance behaviors, risk assessment strategies, and trait anxiety profiles in both acute and longitudinal designs.
This metric reflects the relative amount of time an animal chooses to spend in the open, exposed portion of the arena—typically defined as the inner 25% of a square or circular enclosure. Because rodents innately prefer the periphery (thigmotaxis), time in the center is inversely associated with anxiety-like behavior. As such, this percentage is considered a sensitive, normalized index of:
Critically, because this metric is normalized by session duration, it accommodates variability in activity levels or testing conditions. This makes it especially suitable for comparing across individuals, treatment groups, or timepoints in longitudinal studies.
A high percentage of center time indicates reduced anxiety, increased novelty-seeking, or pharmacological modulation (e.g., anxiolysis). Conversely, a low percentage suggests emotional inhibition, behavioral avoidance, or contextual hypervigilance. reduced anxiety, increased novelty-seeking, or pharmacological modulation (e.g., anxiolysis). Conversely, a low percentage suggests emotional inhibition, behavioral avoidance, or contextual hypervigilance.
The percentage of center time is one of the most direct, unconditioned readouts of anxiety-like behavior in rodents. It is frequently reduced in models of PTSD, chronic stress, or early-life adversity, where animals exhibit persistent avoidance of the center due to heightened emotional reactivity. This metric can also distinguish between acute anxiety responses and enduring trait anxiety, especially in longitudinal or developmental studies. Its normalized nature makes it ideal for comparing across cohorts with variable locomotor profiles, helping researchers detect true affective changes rather than activity-based confounds.
Rodents that spend more time in the center zone typically exhibit broader and more flexible exploration strategies. This behavior reflects not only reduced anxiety but also cognitive engagement and environmental curiosity. High center percentage is associated with robust spatial learning, attentional scanning, and memory encoding functions, supported by coordinated activation in the prefrontal cortex, hippocampus, and basal forebrain. In contrast, reduced center engagement may signal spatial rigidity, attentional narrowing, or cognitive withdrawal, particularly in models of neurodegeneration or aging.
The open field test remains one of the most widely accepted platforms for testing anxiolytic and psychotropic drugs. The percentage of center time reliably increases following administration of anxiolytic agents such as benzodiazepines, SSRIs, and GABA-A receptor agonists. This metric serves as a sensitive and reproducible endpoint in preclinical dose-finding studies, mechanistic pharmacology, and compound screening pipelines. It also aids in differentiating true anxiolytic effects from sedation or motor suppression by integrating with other behavioral parameters like distance traveled and entry count (Prut & Belzung, 2003).
Sex-based differences in emotional regulation often manifest in open field behavior, with female rodents generally exhibiting higher variability in center zone metrics due to hormonal cycling. For example, estrogen has been shown to facilitate exploratory behavior and increase center occupancy, while progesterone and stress-induced corticosterone often reduce it. Studies involving gonadectomy, hormone replacement, or sex-specific genetic knockouts use this metric to quantify the impact of endocrine factors on anxiety and exploratory behavior. As such, it remains a vital tool for dissecting sex-dependent neurobehavioral dynamics.
The percentage of center time is one of the most direct, unconditioned readouts of anxiety-like behavior in rodents. It is frequently reduced in models of PTSD, chronic stress, or early-life adversity. Because it is normalized, this metric is especially helpful for distinguishing between genuine avoidance and low general activity.
Environmental Control: Uniformity in environmental conditions is essential. Lighting should be evenly diffused to avoid shadow bias, and noise should be minimized to prevent stress-induced variability. The arena must be cleaned between trials using odor-neutral solutions to eliminate scent trails or pheromone cues that may affect zone preference. Any variation in these conditions can introduce systematic bias in center zone behavior. Use consistent definitions of the center zone (commonly 25% of total area) to allow valid comparisons. Software-based segmentation enhances spatial precision.
Evaluating how center time evolves across the duration of a session—divided into early, middle, and late thirds—provides insight into behavioral transitions and adaptive responses. Animals may begin by avoiding the center, only to gradually increase center time as they habituate to the environment. Conversely, persistently low center time across the session can signal prolonged anxiety, fear generalization, or a trait-like avoidance phenotype.
To validate the significance of center time percentage, it should be examined alongside results from other anxiety-related tests such as the Elevated Plus Maze, Light-Dark Box, or Novelty Suppressed Feeding. Concordance across paradigms supports the reliability of center time as a trait marker, while discordance may indicate task-specific reactivity or behavioral dissociation.
When paired with high-resolution scoring of behavioral events such as rearing, grooming, defecation, or immobility, center time offers a richer view of the animal’s internal state. For example, an animal that spends substantial time in the center while grooming may be coping with mild stress, while another that remains immobile in the periphery may be experiencing more severe anxiety. Microstructure analysis aids in decoding the complexity behind spatial behavior.
Animals naturally vary in their exploratory style. By analyzing percentage of center time across subjects, researchers can identify behavioral subgroups—such as consistently bold individuals who frequently explore the center versus cautious animals that remain along the periphery. These classifications can be used to examine predictors of drug response, resilience to stress, or vulnerability to neuropsychiatric disorders.
In studies with large cohorts or multiple behavioral variables, machine learning techniques such as hierarchical clustering or principal component analysis can incorporate center time percentage to discover novel phenotypic groupings. These data-driven approaches help uncover latent dimensions of behavior that may not be visible through univariate analyses alone.
Total locomotion helps contextualize center time. Low percentage values in animals with minimal movement may reflect sedation or fatigue, while similar values in high-mobility subjects suggest deliberate avoidance. This metric helps distinguish emotional versus motor causes of low center engagement.
This measure indicates how often the animal initiates exploration of the center zone. When combined with percentage of time, it differentiates between frequent but brief visits (indicative of anxiety or impulsivity) versus fewer but sustained center engagements (suggesting comfort and behavioral confidence).
The delay before the first center entry reflects initial threat appraisal. Longer latencies may be associated with heightened fear or low motivation, while shorter latencies are typically linked to exploratory drive or low anxiety.
Time spent hugging the walls offers a spatial counterbalance to center metrics. High thigmotaxis and low center time jointly support an interpretation of strong avoidance behavior. This inverse relationship helps triangulate affective and motivational states.
By expressing center zone activity as a proportion of total trial time, researchers gain a metric that is resistant to session variability and more readily comparable across time, treatment, and model conditions. This normalized measure enhances reproducibility and statistical power, particularly in multi-cohort or cross-laboratory designs.
For experimental designs aimed at assessing anxiety, exploratory strategy, or affective state, the percentage of time spent in the center offers one of the most robust and interpretable measures available in the Open Field Test.
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