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An Operant-based Touchscreen Morph Discrimination Task Does Not Detect Age-related Mnemonic Similarity Deficits in
Aleyna Ross1,2, Carly N Logan1, John J Thompson1
1Evelyn F. McKnight Brain Institute, Center for Cognitive Aging and Memory, Department of Neuroscience, University of Florida, Gainesville, FL 32611, United States.
Biorxiv : the Preprint Server for Biology
|May 18, 2026
Summary
A new touchscreen task for rats shows sensitivity to stimulus similarity but does not detect age-related memory deficits, unlike older 3D object tasks. This highlights the importance of task design in cognitive aging research.
Area of Science:
- Neuroscience
- Cognitive Science
- Animal Models
Background:
- The Mnemonic Similarity Task (MST) is a sensitive measure of age-related cognitive decline in humans.
- Rodent adaptations of the MST using 3D objects reveal memory deficits in aged animals.
- Translational research requires assays that align with human testing and allow for automation.
Purpose of the Study:
- To develop and validate a touchscreen-based rat analog of the MST using 2D image stimuli.
- To assess age-related differences in mnemonic discrimination using a morphed Object-Cued Spatial Choice (OCSC) task.
- To investigate perirhinal cortical activity during mnemonic discrimination in young and aged rats.
Main Methods:
- Young and aged Fischer 344 × Brown Norway hybrid rats were trained on a touchscreen-based OCSC task with 2D image stimuli.
- Stimulus similarity was parametrically varied using morphed images to manipulate discrimination difficulty.
- Perirhinal cortex activity was measured using Arc gene expression following task performance.
Main Results:
- Both young and aged rats successfully acquired the touchscreen OCSC task.
- Task performance declined systematically with increasing stimulus similarity, indicating sensitivity to discrimination difficulty.
- No significant age-related impairment in mnemonic discrimination was observed, contrary to expectations.
- Arc expression in the perirhinal cortex correlated with behavioral accuracy but did not differ between age groups or overlap conditions.
Conclusions:
- The touchscreen morph OCSC task is sensitive to stimulus similarity but does not replicate age-related mnemonic discrimination deficits seen in 3D object-based MST paradigms.
- The findings underscore the critical role of ethological relevance and task design in the translational validity of cognitive assays for aging research.
- Further research may be needed to optimize rodent models for detecting subtle age-related mnemonic impairments.
