Startle evoked movement is delayed in older adults: implications for brainstem processing in the elderly

Area of Science:

• Neuroscience
• Motor Control
• Aging Research

Background:

• The brainstem is crucial for whole-body motor control.
• Age-related deficits in brainstem function may explain movement impairments in older adults.
• The startle reflex's startReact phenomenon offers a noninvasive method to study brainstem function and motor planning.

Purpose of the Study:

• To investigate age-related differences in the neural processing of movement using the startReact response.
• To evaluate potential deficits in startReact hand extension movements in older adults.
• To determine if the startReact response is delayed in older adults compared to young adults.

Main Methods:

• Electromyography (EMG) recorded sternocleidomastoid (SCM) for startle detection and extensor digitorum communis (EDC) for movement onset.
• Participants (young and older adults) prepared for hand extension and were exposed to a startling auditory stimulus.
• Trials were categorized based on the presence (SCM+) or absence (SCM-) of a startle response.

Main Results:

• The startReact response was found to be intact but delayed in older adults.
• StartReact (SCM+) onset latencies were faster than non-startle (SCM-) trials in both age groups.
• Older adults showed significantly slower SCM+ onset latencies compared to young adults (mean difference of 8 msec).

Conclusions:

• The startReact hand extension movement is preserved but slowed with age.
• The observed age-related delay suggests central processing alterations within the brainstem.
• These findings highlight the brainstem's role in age-related motor control changes.