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Cutaneous flexion reflex in human neonates: a quantitative study of threshold and stimulus-response characteristics
1Department of Anatomy and Developmental Biology, University College London, UK. k.andrews@ich.ucl.ac.uk
Insights
The cutaneous flexion reflex in infants reveals how their nervous systems process sensory information. This reflex is a valuable tool for understanding neonatal sensory development and the impact of tissue damage.
Area of Science:
- Neonatal neurophysiology
- Developmental neuroscience
- Spinal cord sensory processing
Background:
- The cutaneous flexion reflex is a key indicator of spinal sensory processing in neonates.
- Understanding this reflex aids in assessing neurological development and the impact of injury.
Purpose of the Study:
- To investigate spinal sensory processing in infants using the cutaneous flexion reflex.
- To examine the reflex's response to varying stimuli and its correlation with age and tissue damage.
Main Methods:
- Studied 68 infants (28-42 weeks postconceptional age) using mechanical and electrical foot stimuli.
- Recorded electromyography (EMG) responses from the biceps femoris muscle.
- Analyzed reflex latency, amplitude, and response to repeated stimuli.
Main Results:
- A direct correlation exists between mechanical stimulus intensity and reflex latency/amplitude.
- Flexion-reflex threshold increases with age but decreases with contralateral limb tissue damage.
- Response to repeated stimulation decreased with age, showing habituation and then response decrement.
Conclusions:
- The cutaneous flexion reflex is a viable method for studying neonatal sensory processing and the effects of tissue damage.
- Natural mechanical stimulation is more informative than electrical stimulation for this reflex.
Abstract:
The cutaneous flexion reflex has been used to study spinal sensory processing in 68 infants (37 female, 31 male) aged between 28 and 42 weeks postconceptional age (PCA). Mechanical and electrical stimuli were singularly and repeatedly applied to the foot, and single-surface EMG responses were recorded from the biceps femoris muscle. A clear correlation was demonstrated between the mechanical stimulus intensity and latency and the amplitude of the reflex. Mechanical threshold normally increased with age, but the flexion-reflex threshold was lowered by local limb-tissue damage in the contralateral limb. The incidence of response to repeated mechanical stimulation at 2.8 x threshold decreased significantly with increasing age. Repeated mechanical stimulation at 2.8 x threshold caused a build-up in the size of the response followed by a diminution. The flexion reflex can, therefore, be used to investigate sensory processing in the neonate, and the effects of tissue damage. The importance of using natural rather than electrical stimulation is highlighted.