Abstracts

Rationale: Cortical stimulation is playing an increasing role in clinical neuroscience in the treatment of epilepsy, stroke and other neurological conditions. The neuromodulatory effects of cortical stimulation include both excitation and inhibition, the balance of which varies with the stimulation parameters. As a result, cortical stimulation also influences cerebral metabolic, including cerebral blood flow (CBF), cerebral blood volume (CBV), and tissue oxygen (TO), which may also vary depending on the stimulation parameters. However, the effects of direct bipolar cortical stimulation at various parameters on cerebral metabolic changes are not well understood.Methods: In this study, we investigate the effects of stimulation frequency and duration on the neuronal activity using voltage sensitive dye imaging and cerebral metabolic response using intrinsic optical imaging, laser doppler flowmetry and optical sensitive. Results: Single bipolar spike with the amplitude of 4 mA and width of 100 s can induce robust neuronal activity but no significant change in CBF, CBV, or TO. Double spikes stimulation at 1-250Hz cannot induce metabolic changes although neuronal activity can be recorded with VSD. Two second stimulation of >=5 Hz can induce increase in CBF, CBV and TO. The amplitude and duration of metabolic changes increased with the increase of the frequency. Maximal reached when the stimulation frequency was >100Hz. When the stimulation frequency is <=10 Hz, the duration of the hemodynamic change increased as the increase of stimulation. When the stimulation frequency is >=50 Hz, the neuronal response cannot follow each spike and the hemodynamic changes cannot follow prolonged stimulation. Conclusions: These results demonstrate that the frequency of stimulation is important in determining the amplitude and duration of the cerebral metabolic responses and that the relationship between frequency and metabolic response is not linear.