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Event-related brain potentials during an extended visual recognition memory task depict delayed development of
J H Karrer1, R Karrer, D Bloom
1University of Kansas Medical Center, Smith Mental Retardation and Human Development Research Center, Kansas City, MO, USA.
Insights
Infants with Down syndrome (DS) show delayed brain inhibitory processes, evidenced by altered event-related potentials (ERPs) and slower habituation to visual stimuli compared to neurotypical infants (nDS).
Area of Science:
- Neuroscience
- Developmental Psychology
- Genetics
Background:
- Cerebral inhibitory processes may be delayed in early development for individuals with Down syndrome (DS).
- Previous research using sensory-evoked potentials (EPs) and event-related brain potentials (ERPs) indicated altered stimulus habituation in infants with DS.
Purpose of the Study:
- To investigate if extended visual stimulus experience in 6-month-old infants with and without DS (nDS) reveals altered ERP and behavioral response decrements.
- To determine if infants with DS exhibit differences in habituation patterns compared to nDS infants.
Main Methods:
- Employed an 80/20% oddball paradigm with visual stimuli.
- Matched infants with DS and nDS by age and gender.
- Recorded and analyzed event-related brain potentials (ERPs), focusing on Nc and Pb components at frontal (Fz) and parietal (Pz) sites.
Main Results:
- Infants with DS showed significantly larger Nc areas/amplitudes and Nc2 areas, but smaller Pb peak amplitudes compared to nDS infants.
- Infants with DS exhibited significantly slower decrement of most ERP components with repetitive stimulation, with minimal decrement at Fz.
- Both groups responded to rare stimuli with larger Nc and Pb amplitudes, but no significant differences in visual attention were found.
Conclusions:
- The study supports the hypothesis of altered inhibitory processes in the brains of infants with DS.
- ERPs are valuable tools for studying atypical cognitive development in infancy, particularly in Down syndrome.
- Findings highlight differences in neural processing and habituation in infants with DS, even with controlled visual stimulation.
Abstract:
Development of cerebral inhibitory processes among individuals with Down syndrome (DS) may be delayed at an early age. In support of this hypothesis, sensory-evoked potentials (EPs) and event-related brain potentials (ERPs) have previously delineated altered habituation to stimuli among infants with DS. The purpose of the current study was to provide extended experience with visual stimuli among 6-month-old infants with and without DS (nDS) to determine if altered ERP and behavioral response decrements would be evident even after repeated presentations of stimuli. An 80/20% oddball paradigm was employed. Infants with DS and nDS were matched according to age and gender. Infants with DS demonstrated significantly larger Nc areas, Nc peak amplitudes, Nc2 areas and, inversely, significantly smaller peak Pb amplitudes when compared to infants nDS. Contrasts of the two study groups were most robust within ERP measures from frontal (Fz) and parietal (Pz) recording sites. Infants with DS also demonstrated a significantly slower decrement of most ERP components with repetitive stimulus experience. Most noteworthy was the observation of little or no decrement of ERP components at Fz among infants with DS. Both infants with DS and nDS demonstrated significantly larger Nc peak amplitudes, Nc areas, Nc2 areas, Pb peak amplitudes and NSW areas to rare stimuli. While significant probability and experiential trends were observed in visual fixation measures across both study groups, there were no significant differences of visual attention between infants with DS or nDS. These data demonstrate the value of ERPs within the study of atypical cognitive development during infancy and support the concept of altered inhibitory processes in the brain of infants with DS.