Age group differences in learning-related activity reflect task stage, not learning stage

Area of Science:

• Neuroscience
• Cognitive Aging
• Neuroimaging

Background:

• Healthy aging is associated with declines in implicit associative learning (IAL).
• Previous functional magnetic resonance imaging (fMRI) studies linked IAL deficits in older adults to different brain activity patterns compared to younger adults.
• These prior findings may be confounded by differences in task performance stages between age groups.

Purpose of the Study:

• To investigate age-related differences in the neural mechanisms of IAL.
• To disentangle the effects of task stage from learning stage on brain activity during IAL.
• To clarify whether observed age differences in IAL reflect performance timing or genuine learning capacity.

Main Methods:

• Acquired fMRI data from 28 younger (mean age 20.8 years) and 22 older (mean age 73.6 years) healthy adults.
• Participants completed the Triplets Learning Task, learning associations between cue and target locations with high (HF) or low (LF) frequency.
• Analyzed brain activity, matching participants by task stage and then by learning stage to compare neural substrates of IAL across age groups.

Main Results:

• When matched for task stage, older adults exhibited poorer learning and greater IAL-related activity in the hippocampus (early stage) and globus pallidus (late stage) compared to younger adults.
• However, when matched for learning stage, no significant differences in learning performance or IAL-related brain activity were found between the age groups.
• This suggests that older adults engage similar brain regions as younger adults when learning associations, but their learning emerges later.

Conclusions:

• Observed age-related differences in neural activity during IAL tasks may be attributed to differences in task stage progression, not fundamental learning deficits.
• Older adults demonstrate comparable neural engagement to younger adults for IAL when learning onset is considered.
• These findings challenge previous interpretations of age-related IAL deficits and highlight the importance of considering learning progression in neuroimaging studies of aging.