Negative BOLD closely follows neuronal suppression in superior colliculus

Abstract

The underlying sources of negative BOLD responses (NBRs) are still debated. Here, we show rat superior colliculus (SC) NBRs associated with visual stimulation at short inter-stimulus intervals (ISIs) along with decreases in power of local field potentials and multi-unit activity signals measured in this region. This hints to neuronal suppression, possibly due to impossibility of complete excitability recovery upon short ISIs, associated with NBRs. Moreover, both NBRs and electrophysiological power time profiles reveal one peak after stimulus started and another when it ceased, highlighting the SC nature of detecting "brightness changes" when individual flashes are no longer perceivable.