Determination of vertical motions in the upper thermosphere at midlatitudes from high time resolution Doppler shift measurements of the [OI>3P-1D transition emission at night show that there exist oscillations with ~40 min periodicity and large magnitude (ca. 50 m/s). The behavior of these oscillations is ascribed to the passage of gravity waves through that region of the atmosphere. The results also show that individual (high time resolution) zenith measurements of the neutral thermosphere emissions can not be used as (zero) reference winds with any degree of certainty.