Zone Preference in the Visual Water Maze
June 26, 2025
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Barometers are invaluable devices used to measure atmospheric pressure. Atmospheric or air pressure is defined as the force applied onto a surface by the weight of air, pulled by gravity. Air pressure changes with distance below or above sea level. Note that air pressure and oxygen level decrease as altitude increases.
Interestingly, Evangelista Torricelli is credited as the inventor of the first barometer in the 17th century. It was Blaise Pascal, however, who proved that air pressure is a result of the vertical weight of the air in the atmosphere. The design of barometers has evolved significantly over the centuries. We should note that there are two main types of mechanical barometers: mercury and aneroid meters. Note that mercury was a common liquid used in the past as its density allows barometers to be of manageable dimensions. Aneroid or non-liquid barometers, on the other hand, are more durable and wildly used as portable devices. Apart from mechanical barometers, there are electronic barometers, and some miniature units can be installed on cell phones.
Measuring air pressure is vital. To provide an example, barometric pressure concerns mountain climbers and scuba divers as moving from high pressure to low pressure too quickly can cause decompression sickness. Measuring pressure is also essential during cabin pressurization and flying. Furthermore, fluctuations in air pressure can predict weather changes. Fast drops in pressure can indicate oncoming storms, while high pressure often results in calm weather. Changes in weather and barometric pressure, on the other hand, can affect people’s health and lead to joint pain, migraine, and other aches.
From predicting the weather to marine applications, barometers are invaluable scientific tools. Choosing a barometer, however, can be challenging. Prospective buyers should consider three major factors: requirements, specifications, and costs.
Requirements: Enhanced by the advancements in science and technology, prospective buyers can choose from a wide range of barometers. As stated above, there are mechanical and electronic meters, with mercury and aneroid models being the most popular mechanical units for sale. While mercury units utilize liquid, aneroid units use a system of springs, which make them safer and more portable (ideal for hikers and fishermen). Note that if one wants to record the history of the pressure fluctuations, it’s better to choose a barograph. Barographs are defined as aneroid barometers that record the changes in air pressure on chart paper.
Specifications: Accuracy and reliability are the main parameters to consider. Here we should note that most barometers today have decorative functions. In fact, the dials of both mercury and aneroid models can be of copper, decorative paper, or brass, while casings can be made of oak or mahogany. The design of barometers also varies; because of their shape, mercury barometers are often called stick barometers, while aneroid units have a round shape. When it comes to aneroid models, we should mention that they can be placed on a wall/stand or function as pocket units.
Total costs: Although the design of a unit is essential, users should search for accurate and reliable barometers. Usually, more costly units provide higher accuracy. Prospective buyers should consider barometers with clearly marked dials, small screws and knobs to facilitate calibration, and additional accessories (e.g., neck lanyards). Sets that include different devices (e.g., a barometer and a hydrometer in one) can be both reliable and elegant, but more costly.
Given the wide variety of units for sale, it’s no surprise that choosing a barometer can be a challenging task. Therefore, based on different parameters and user reviews, we provide a list of the best barometers for sale to help readers make an informed decision.
1. Ambient Weather WS-228TBH 9″ Brushed Aluminum Contemporary Barometer with Temperature and Humidity
Ambient Weather WS-228TBH 9″ Brushed Aluminum Contemporary Barometer with Temperature and Humidity is one of the most attractive barometers on the market. The unit is made of an aluminum bezel and a radiant blue dial. Note that it comes with a set screw for calibration and a hook for hanging (the unit allows for sea-level calibration of up to 3,000 feet). This measuring station has a reference needle to track changes in pressure, and also indicators for temperature (°F) and humidity (%). With a variety of features and beautiful design, this barometer is a great gift choice for both professionals and weather lovers.
2. Ambient Weather B1025C Antique Storm Glass – Wall Mount Liquid Barometer with Drip Cup
Ambient Weather B1025C Antique Storm Glass – Wall Mount Liquid Barometer with Drip Cup is a classic and attractive unit used to measure atmospheric pressure and predict stormy weather. This storm glass consists of a hand-blown glass container with a sealed body, half-filled with water (13 inches/30.5 cm long). With its attractive design, this measuring unit is a wonderful choice for anyone in love with science and aesthetics.
3. Learning Resources Weather Centre
Learning Resources Weather Centre is an affordable three-in-one unit ideal for learning environments. The set consists of a barometer used to measure air pressure, a hygrometer to detect moisture, and a thermometer to measure temperature (°C and °F). Note that these three devices can be removed and used separately (each 2.95 inches/7.5 cm). Furthermore, the unit comes with an activity guide and a case, which makes it great for beginners and young learners.
4. Downeaster Blue Dial Standard Barometer
Downeaster Blue Dial Standard Barometer is an elegant barometer. Note that the unit has a brass case that can be mounted on a wall or a stand. This product is ideal for detecting changes in air pressure and predicting storms. As explained above, increasing air pressure indicates fair weather, while decreasing pressure indicates stormy weather.
5. Weems and Plath Endurance II 105 Open Dial Barometer
Weems and Plath Endurance II 105 Open Dial Barometer is a great unit with a weather-resistant and protective coating. This barometer is not only durable but attractive, which makes it a great gift choice for anyone interested in tracking air pressure and weather changes. Note that the unit is calibrated for altitudes of up to 3,500 feet above sea level.
6. La Crosse Technology C85845 Color Wireless Forecast Station
La Crosse Technology C85845 Color Wireless Forecast Station is a great wireless set that measures air pressure and presents an animated color forecast. The unit also measures in/out temperature and humidity. Additionally, it has customizable alerts and includes a full calendar. Note that the unit is powered by five AA alkaline batteries. With its easy-to-read display with adjustable backlight, this wireless forecast station is a versatile and attractive unit.
7. Ambient Weather Fischer 6901-22 Instruments – Brass Dial Banjo Weather Station with Thermometer/Hygrometer/Barometer
Ambient Weather Fischer 6901-22 Instruments – Brass Dial Banjo Weather Station with Thermometer/Hygrometer/Barometer is a traditional decorative piece ideal for an elegant study, a library, or a trendy restaurant. This wooden-framed station can measure temperature (°C and °F), barometric pressure (mbar and inHg), and humidity (%), which makes it a great gift choice for collectors interested in science. Note that this barometer operates to 3,000 feet altitude.
Barometers are precise scientific instruments, and as such, they require proper care.
Barometers are invaluable scientific tools used to detect changes in air pressure. They are used in a variety of settings, including meteorology, flying, diving, fishing, and mountaineering. As explained above, changes in air pressure can help to predict the weather. Note that there are two main types of barometers: mercury and aneroid units.
That being said, because of the wide variety of barometers on the market, choosing a new instrument can be a daunting task. Prospective buyers should consider three major factors: requirements, specifications, and total costs. While most units designed for home use are decorative, accuracy is essential. When it comes to outdoor adventures and fishing, portable aneroid models are recommended. Additionally, users should ensure a unit is calibrated and handled with care, especially mercury barometers.
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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