A short review on behavioural assessment methods in rodents

The rodent behavioural examination techniques are used to assess various psychological, neurological models and neurotoxicity studies. Therefore, it is of interest to document the various behavioural assessment methods used in rodent model to study the motor, sensory, cognitive functions and emotional behaviour.


Background:
Over the past decade, there has been a steady increase in the study of laboratory animal behavior.This field has placed a growing emphasis on various commonly used species, recognizing the significance of animals' motor, cognitive, and social activities.[1] Despite being kept in captivity for extended periods, laboratory animals retain their instinctual behaviors and characteristics that evolved in their wild ancestors.It is essential to test their natural active behaviors, such as exploration, inquisitiveness, and digging, aggression, rearing, and climbing, while considering well-defined circadian rhythms.[2] Behavior assessment is a scientific approach that relies on the ability of human observers to integrate observed details of behavior, posture, and context to summarize animals' behavioral patterns.[3] Observers use descriptors like "relaxed," "anxious/tense," "frustrated," or "content" to evaluate and assess animals' emotional states.The use of feasible indicators to evaluate animals' emotional states is strongly recommended in behavioral assessments.[4] Behaviors can be measured in terms of interval (also known as latency), frequency, and duration.Interval measures the time it takes for a specific behavior to occur.It can be measured in seconds, minutes, or hours.Frequency refers to the number of times a behavior occurs during an observation period and is usually measured per minute, per hour, or per day.Duration measures how long a behavior lasts and can be measured in seconds, minutes, or hours.[5] Rodent models are essential for studying brain disorders, including neurodevelopmental, neuropsychiatric, and neurodegenerative diseases.They help increase our understanding of underlying pathology and serve as preclinical models for testing potential treatments.[6] Behavioral outcomes are among the most significant measures in these studies.Unfortunately, reports from different laboratories often yield conflicting results, and findings from rodent models are not consistently replicated in human trials [7].There are several wellestablished tests available to assess various behavioural readouts.However, subtle aspects such as housing conditions, testing conditions, and the sex and strain of animals can influence the measurements.[8] Therefore, it is important to consider these factors during behavioral testing to ensure the reliability and reproducibility of results.Zhang et al. in 2017 used a chronic migraine rat model to evaluate depression and anxiety behavior using a panel of tests.[9] The group that received inflammatory soup infusion showed a decrease in sucrose preference, locomotor and rearing behaviors, inner zone distance percent, open-arm entry percent, and serotonin & dopamine levels in the prefrontal brain.
[10] Weight, inner zone time percentage, or open-arm time percentage weren't different between the two groups.Therefore, it is of interest to document the various behavioural assessment methods used in rodent model to study the motor, sensory, cognitive functions and emotional behaviour.cognitive and behavioral in rodent models of brain aging, dementia and various behavioral paradigms, such as the Y maze, Morris water maze, Barnes maze, and more, were discussed.These paradigms are used to test spatial memory, recognition memory, semantic memory, spatial memory, and emotional memory [11].

Tests to assess the motor function and coordination:
Table 1 presents various behavioral tests for evaluating motor function and coordination.Tests include the staircase, beam walking, rotarod, open field, cylinder, foot-fault, pole, and elevated body swing tests for muscle strength.Evaluation of fine motor coordination and balance involved tests like staircase, rotarod, cylinder, grid walk, and beam walking.Tests such as forelimb placing identified forelimb function and deficits, while the wire hanging test evaluated locomotor abnormalities and behavioral deficits [12].The climbing test assessed motor impairments, and the grid stepping evaluated sensorimotor deficits.Grip strength was measured to assess skeletal muscle function, and skilled limb use evaluated voluntary motor control.Reaching tests and the acoustic startle response assessed motor and cognitive performance.Operant tasks were used for cognitive performance evaluation [13].Tests like the rotarod, triple horizontal bar, static rods, and parallel bar evaluated muscle coordination and strength [14].Foot fault assessed motor functions, and the pole test evaluated movement disorders [9].Neuromuscular weakness was assessed through grip strength, swimming tests measured endurance, and gait analysis identified ataxic and paretic gait.Various methods were applied for assessing motor coordination, balance, and rigidity [15].

Table 1 :
List of various behavioural tests to assess the motor function and coordination

Table 2
List of specific methods in testing sensory function of rodents.

Table 3 :
List of various methods in testing cognitive (learning and memory) functions of rodents

Table 4
List of various methods in assessing emotional state of rodents.
arm maze, and modified elevated plus-maze for spatial learning and memory.Passive avoidance and the three-panel runway maze assessed avoidance learning and working memory [18].The Y-maze test evaluated active working short-term memory, while the object recognition test assessed various memory types [16].Barnes maze, eight-arm radial maze, and swimming pool spatial tasks were used for memory acquisition assessment [13].T-maze and operant chamber tests assessed short-term memory and learned performance [14].Radial arm water maze and Y-maze spontaneous alternation task evaluated spatial working memory [11].Novel object recognition and fear conditioning assessed associative and working memory [19].Olfactory memory and learning were measured through odor preference conditioning [

14]. Test to assess emotional state:
Table 4 provides methods for assessing the emotional state of rodents, including anxiety and depression symptoms.Tests for anxiety-like behavior encompassed open field, novelty suppressed feeding, and raised plus maze tests.The light/dark box test evaluated anxiety-related behavior [20].Elevated zero maze and marble burying tests were employed for anxiety-related behaviors, and the hole-board test measured anxiety, stress and emotion.Tests to assess emotion and depression included the forced swim test, sucrose preference, and tail suspension test [7].Coated and splash tests evaluated depression-like behavior.Upraised plus maze and forced swim tests assessed depression [21].Tests such as the star maze and hole-board maze were used to measure emotional state [15].Novelty-suppressed feeding and forced swim tests were employed for depression assessment [7].Behavioural assessment is a critical parameter in neurotoxicity studies, drug development, and neurological and psychological model screening.A wide range of tests are available for assessing motor, sensory, cognitive, and emotional states in rodents.The choice of tests should align with the study's nature and be carried out with adherence to ethical animal handling practices.To minimize bias during analysis, video recordings of behavioral sessions are recommended.