Larger nondeclarative than declarative deficits in learning and memory in human aging

Area of Science:

• Cognitive Psychology
• Neuroscience
• Human Aging Research

Background:

• Nondeclarative learning, measured by classical conditioning, is often assumed to be preserved in aging.
• Declarative learning, assessed via verbal recall, is known to decline with age.
• Previous research has not directly compared age-related changes in nondeclarative and declarative learning within the same individuals.

Purpose of the Study:

• To compare age-related differences in nondeclarative learning (eyeblink classical conditioning, EBCC) and declarative learning (California Verbal Learning Test, CVLT).
• To investigate the relationship between nondeclarative and declarative learning performance, controlling for age.
• To challenge the assumption that nondeclarative memory is more resilient to aging than declarative memory.

Main Methods:

• Eighty participants were assessed using eyeblink classical conditioning (EBCC) with 400-ms and 750-ms delay paradigms.
• Participants also completed the California Verbal Learning Test (CVLT) to measure declarative learning.
• Partial correlations were used to examine the relationship between EBCC and CVLT performance, adjusting for age.

Main Results:

• Significant age differences were found in nondeclarative EBCC, even in the 750-ms paradigm.
• Age differences in EBCC were comparable to those in the declarative CVLT task.
• No significant correlation was observed between nondeclarative EBCC and declarative CVLT performance after controlling for age.

Conclusions:

• Nondeclarative learning, as measured by EBCC, is susceptible to age-related decline.
• The findings contradict the hypothesis that nondeclarative memory is inherently more resistant to aging than declarative memory.
• Nondeclarative learning and memory may not represent a unitary system, exhibiting varied patterns of age-related change.