Cardiorespiratory rhythm-contingent trace eyeblink conditioning in elderly adults

Learning outcome is modified by the degree to which the subject responds and pays attention to specific stimuli. Our recent research suggests that presenting stimuli in contingency with a specific phase of the cardiorespiratory rhythm might expedite learning. Specifically, expiration-diastole (EXP-DIA) is beneficial for learning trace eyeblink conditioning (TEBC) compared to inspiration-systole (INS-SYS) in healthy young adults. The aim of this study was to investigate whether the same holds true in healthy elderly adults (n = 50, aged >70 years). Participants were instructed to watch a silent nature film while TEBC trials were presented either at INS-SYS or EXP-DIA (separate groups). Learned responses were determined as eyeblinks occurring after the tone-conditioned stimulus (CS), immediately preceding the airpuff-unconditioned stimulus (US). Participants were classified as learners if they made at least five conditioned responses (CRs). Brain responses to the stimuli were measured using electroencephalogram (EEG). Memory for the film and awareness of the CS-US contingency were evaluated with questionnaires. As a result, participants showed robust brain responses to the CS, acquired CRs, and reported awareness of the CS-US relationship to a variable degree. There was no difference between the INS-SYS and EXP-DIA groups in any of the above. However, when only participants who learned were considered, those trained at EXP-DIA (n=11) made more CRs than those trained at INS-SYS (n=13). Thus, learned performance could be facilitated in those elderly who learned. However, training at a specific phase of cardiorespiratory rhythm did not increase the proportion of participants who learned.