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Zusammenfassung:
The development of 1H Magnetic Resonance Spectroscopy (MRS) techniques has made it possible to detect different brain metabolites, including elevated lactate concentrations in vivo in humans. It is generally assumed that increased brain lactate is pathological and reflects a dysbalance between glycolysis and oxidative respiration. However, there is an alternative opinion, suggesting that elevated lactate concentration in the brain represents a normal response to neuronal activity. Visual stimulation is one of
the functional paradigms that can modify brain lactate levels. We performed 1H MRS (chemical shift imaging at TE of 35ms and 288 ms) with a Philips Achieva 3T MRI scanner in 19 healthy volunteers without any history of neurological or psychiatric disorders. MRS measurements have been performed before, during and after light stimulation. Using an optimized protocol, lactate was detected in three probands (15.8\%). In one case lactate emerged as a result of the stimulation, while two others showed lactate at baseline. One of the probands had a high lactate double peak in the absence of previous physical or
psychological strain; this finding was not reproduced in two follow-up 1H-MRS measurements. Our findings
demonstrate that detectable levels of lactate may be present in healthy brains, and show considerable
variability without any known pathology or exercise prior to the measurement. Thus, the interpretation of
elevated brain lactate levels in neurological and psychiatric disorders has to be done with caution.
