Modified Radial Y-Maze Detects Subtle Spatial Memory Loss in Mice

A modified Y-maze testing procedure developed by neuroscientists significantly enhances sensitivity for detecting subtle spatial recognition memory impairments in aging mice and rodent models of Alzheimer’s disease. While conventional spatial memory assessments often depend on prolonged training schedules, food restriction rewards, or aversive swimming conditions that introduce non-cognitive stress, standard two-trial Y-maze tasks rely on a rodent’s innate curiosity to explore novel environments. However, traditional three-arm Y-mazes suffer from rapid memory decay where animals forget previously visited arms within two hours, creating a floor effect that conceals early, mild cognitive deficits. The newly characterized configuration resolves this constraint by adapting an eight-arm radial maze apparatus into an open Y-formation, substantially raising cognitive demand and generating robust recognition memory that endures for at least 24 hours.

The physical structure of the apparatus was re-engineered to prevent simple egocentric turning strategies and force animals to navigate using distal spatial cues positioned around the testing room. In the classical configuration, three walled arms measuring 30 centimeters in length, 8 centimeters in width, and 15 centimeters in height meet at 120-degree angles without an independent central junction, allowing mice to simply alternate left-right choices. By contrast, the modified setup uses an elevated platform standing one meter above the floor, featuring a large central circular arena 32 centimeters in diameter and three open, wall-less arms measuring 62 centimeters in length and 12 centimeters in width. These arms are arranged in an asymmetrical Y-shape with angles of 90 degrees, 135 degrees, and 135 degrees, while the remaining five arms of the eight-arm radial frame remain sealed, requiring mice to traverse longer distances across the platform under dim illumination of 40 to 50 lux.

Establishing the behavioral protocol requires standardized handling to prevent exploratory inhibition caused by stress or environmental anxiety. Male C57BL/6J mice—including young adults at 4 months of age and aged mice at 22 months—were acclimatized to animal facility housing for at least two weeks and handled individually for three minutes daily over three to five consecutive days prior to evaluation. On experimental days, home cages were stationed in an adjacent ante-room for 30 minutes before testing began. To eliminate olfactory cues that could bias arm entries, maze surfaces were cleaned between runs using 30 percent ethanol, which was allowed to evaporate completely to prevent odor irritation. Baseline trials in separate cohorts of naive mice confirmed that animals distributed their exploration equally across the three open arms, spending approximately 33 percent of their time in each sector without innate spatial bias.

The testing regimen consists of an initial ten-minute training trial followed by a variable inter-trial interval and a subsequent choice test. During training, the mouse is placed on the central platform facing the closed arms with access permitted to only two open arms, allowing it to inspect and encode surrounding visuospatial landmarks. An entry is scored when the rodent places its forepaws and anterior half of its body into an arm, while exit is registered once the front body segment returns to the central arena. Successful encoding requires that the mouse actively visits both available arms. Researchers noted that memory strength could be parametrically enhanced by administering a second training session shortly after the first, which reinforced spatial representation before delay periods were introduced.

During the memory test phase, the previously blocked third arm is opened, and the animal is reintroduced to the central platform facing one of the familiar arms to assess its natural exploratory preference. Unlike classical Y-maze calculations that disregard the start arm and assess preference against a 50 percent chance baseline between two options, the modified paradigm evaluates discrimination across all three open arms, setting empirical chance performance at 33.3 percent while excluding time spent within the central circle. Total exploration duration and entry numbers in the training phase are recorded simultaneously to confirm equal information acquisition, while immobility within the central hub serves as an internal checkpoint to ensure pharmacological interventions or genetic manipulations do not cause non-specific motor or emotional disruptions.

Experimental trials in young 4-month-old control mice demonstrated that the modified paradigm preserves recognition performance across substantially extended intervals compared to the classical maze. When evaluated in the traditional walled apparatus, young mice exhibited memory retention after a 10-minute delay but decayed to chance performance at two and four hours, illustrating the rapid forgetting that hampers longitudinal assessment. Conversely, young cohorts in the modified radial setup displayed significant novelty preferences above chance level across delays of 10 minutes, 2 hours, 4 hours, 6 hours, and 24 hours. Repeating the initial exploratory training phase further increased discrimination indices measured at 24 hours, confirming that spatial memory formation in the open-arm design is both stable and delay-dependent.

The extended retention window enabled the modified maze to uncover age-related spatial memory loss that remained completely undetected in standard testing. When aged 22-month-old mice were tested alongside young controls in the classical Y-maze, both cohorts performed comparably well after a 10-minute delay, but young animals fell to chance levels after two hours, creating a floor effect that masked potential group differences. In the modified task, however, aged mice demonstrated intact novelty preference at the brief 10-minute interval, confirming preserved sensory faculties, intact locomotion, and normal exploratory motivation, yet displayed significant memory impairment when tested after a 4-hour delay, alongside an emerging deficit trend at two hours. Automated tracking confirmed that both age groups spent equivalent amounts of time exploring arms and navigating the central hub during training, ruling out sensorimotor decline as a confounding factor.

The modified paradigm proved equally decisive in evaluating an inducible mouse model of Alzheimer’s disease created via intrahippocampal infusions of amyloid-beta oligomers. Structural verification of the oligomer-rich solution was established through Western blot and dot blot assays utilizing the anti-oligomer A11 antibody and the 6E10 antibody targeting amyloid-beta residues 1 through 16. When tested in the classical Y-maze, mice infused with amyloid-beta oligomers exhibited no statistically significant difference in novelty exploration compared to vehicle-injected saline controls, yielding a non-significant result with a p-value of 0.36. In sharp contrast, identical pathological cohorts tested in the modified radial apparatus completely failed to discriminate the novel arm during the retrieval phase, while saline controls maintained robust novelty preference, establishing the modified design’s capacity to resolve amyloid-induced cognitive deterioration.

Previous neuropharmacological validations cited in the protocol confirmed that successful performance in this modified behavioral architecture is strictly dependent on hippocampal function. Selective temporary inactivation of the dorsal hippocampus via immediate post-training microinfusions of the sodium channel blocker lidocaine abolished novel arm recognition when probed four hours later, corroborating that memory consolidation in the modified Y-maze relies on intact hippocampal circuits. This biological dependency, coupled with the absence of wall boundaries that compels animals to attend to distal environmental cues, verifies that the protocol tests allocentric place learning rather than simplistic egocentric response habits.

Methodological safeguards and technical parameters must be preserved to guarantee data reliability and eliminate confounding variables during behavioral tracking. Video detection systems using specialized tracking software require balanced illumination and suitable visual contrast between the rodent’s coat and the maze floor, which can be optimized using contrasting floor inserts when tracking dark-coated C57BL/6J mice. In addition, because the assay hinges upon spontaneous novelty exploration, repeated testing within short timeframes must be avoided to prevent behavioral habituation, and any repeated measures require spacing over multiple days with rotated visual room cues. While the modified Y-maze provides a sensitive, low-stress platform for screening neurodegenerative therapies across delays up to 24 hours, researchers emphasized that it does not assess remote memory consolidation persisting over weeks, for which single-trial fear conditioning paradigms remain necessary.

Subject of Research: Spatial recognition memory testing in rodent models of aging and neurodegeneration

Article Title: A novel Y-maze paradigm with enhanced sensitivity to subtle spatial recognition memory impairments in mice

Article References: Hadzibegovic, S., Bontempi, B., & Nicole, O. (2025). A novel Y-maze paradigm with enhanced sensitivity to subtle spatial recognition memory impairments in mice. BMC Methods, 2(1), Article 22. https://doi.org/10.1186/s44330-025-00043-6

Image Credits: AI Generated

DOI: 10.1186/s44330-025-00043-6

Keywords: spatial recognition memory, Y-maze paradigm, radial arm maze, Alzheimer's disease, aging mouse models, allocentric spatial navigation, C57BL/6J mice, amyloid-beta oligomers, novelty exploration, cognitive decline, behavioral neuroscience, inter-trial interval, hippocampal memory, preclinical testing, video tracking, memory retention