Developmentally impaired processing speed decreases more than normally with age

Area of Science:

• Neuroscience
• Cognitive Psychology
• Developmental Psychology

Background:

• Brain damage can lead to accelerated aging, possibly due to diminished neuronal capacity for compensatory plasticity.
• Psychosocial factors can complicate the understanding of neuronal explanations for age-related cognitive decline.
• Developmental dyslexia is associated with impaired processing speed of sequential temporal information.

Purpose of the Study:

• To investigate the age-dependent decline in processing speed in individuals with developmental dyslexia compared to fluent readers.
• To determine if cognitive deficits in dyslexia are exacerbated by aging and to explore the underlying neuronal mechanisms.

Main Methods:

• Compared processing speed in dyslexic and fluent readers aged 20-59 years across six tasks.
• Focused on psychosocially comparable groups to isolate neuronal effects.
• Analyzed the rate of processing speed decrement with age, particularly for periodic stimuli.

Main Results:

• Processing speed was significantly impaired in individuals with dyslexia.
• Processing speed decreased with increasing age in both groups.
• The rate of processing speed decrement was faster in dyslexic readers than in fluent readers, especially for periodic stimuli.
• Experiential factors like reading did not explain the exacerbated decline.

Conclusions:

• The findings support a neuronal explanation for the accelerated cognitive deterioration observed in older individuals with dyslexia.
• Reduced neuronal capacity to counteract age-related decline may be a key factor in dyslexia.
• Age-related processing speed deficits are more pronounced in dyslexia, highlighting specific neural vulnerabilities.