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Changes in visual evoked potentials on acute induction to high altitude.
S B Singh1, L Thakur, J P Anand
1Defence Institute of Physiology & Alllied Sciences (DIPAS), Delhi, India. syp_011@yahoo.com
The Indian Journal of Medical Research
|December 14, 2004
Summary
High altitude exposure, particularly at 4300m, significantly increases the latency of the N1 wave in visual evoked potentials (VEPs). This change, observed in both eyes, suggests potential synaptic delays or altered neuronal processing due to hypobaric hypoxia.
Area of Science:
- Neuroscience
- Altitude Physiology
- Sensory Systems
Background:
- High altitude exposure induces hypobaric hypoxia, affecting central nervous system (CNS) functions.
- Hypoxia is known to impact sensory systems, including visual and auditory pathways.
Purpose of the Study:
- To investigate the effects of hypobaric hypoxia on visual evoked potentials (VEPs).
- To assess changes in VEPs at two high-altitude levels: 3200 m and 4300 m.
Main Methods:
- VEPs were recorded from 30 volunteers at sea level (SL), 3200 m (HA I), 4300 m (HA II), and upon return to sea level (RSL).
- Absolute latencies and amplitudes of positive and negative VEP waves were analyzed.
Main Results:
- No significant alterations in N1, P1, and N2 wave latencies were observed at 3200 m.
- A statistically significant increase in N1 wave latency was found at 4300 m compared to SL and 3200 m (P < 0.01).
- A slight increase in P1 wave latency was noted at 4300 m in both eyes.
Conclusions:
- Hypobaric hypoxia at 4300 m increases N1 wave latency within physiological limits.
- The observed increase in N1 wave latency may be attributed to synaptic delay or altered neuronal processing at high altitudes.