Translational aspects of acquiring complex auditory behavioral paradigm highlighting learning dynamics in rats

In humans, the auditory three-class oddball paradigm probes neural markers of target detection among rare distractors and frequent standard stimuli, critically involving the thalamic centromedian-parafascicular (CM-Pf) complex. Rodents are widely used in translational research but differ from humans in auditory perception and learning. We tested whether rats can be trained with human-relevant stimuli and effects on CM-Pf event-related potentials (ERPs). Male Sprague Dawley rats (n = 11) were trained to respond to a rare target tone (5 kHz, high-tone subgroup, or 1.5 kHz, low-tone subgroup) while ignoring a rare distractor (1.5 or 5 kHz) and a frequent standard tone (3 kHz). During behavioral testing, ERPs were recorded using stereotaxically implanted electrodes in the CM-Pf. During training, reaction times to target tones were initially randomly distributed, but became increasingly locked to stimulus onset as accuracy improved (p < 0.01). In contrast, false responses to sequentially introduced standard and distractor tones were initially stimulus-locked, but later became sparse and randomly distributed (p < 0.05) as rats learned to ignore these tones. CM-Pf ERP amplitudes were highest for target tones (p < 0.01), while standard and distractor tones did not differ, indicating neglect of both stimulus types (p = 0.15). Training with 1.5 or 5 kHz target tones produced no major behavioral or neural differences. These findings support the use of rats as a translational model for auditory discrimination and deviance processing using human-relevant tone frequencies, while highlighting the need to consider learning dynamics involved when comparing rats and humans.