@misc{ZaidiBFLS2018_2,
  title = {{The timing of hemodynamic changes reliably reflects spiking activity}},
  abstract = {{Functional neuroimaging is a powerful non-invasive tool for studying brain function, using changes in blood oxygenation as a proxy for underlying neuronal activity. The neuroimaging signal correlates with both spiking, and various bands of the local field potential (LFP), making the inability to discriminate between them a serious limitation for interpreting hemodynamic changes. Here, we record activity from the striate cortex in two anesthetized monkeys (Macaca mulatta), using simultaneous functional near-infrared spectroscopy (fNIRS) and intra-cortical electrophysiology. We find that low-frequency LFPs correlate with hemodynamic signal\textquotesingles peak amplitude, whereas spiking correlates with its peak-time and initial-dip. We also find spiking to be more spatially localized than low-frequency LFPs. Our results suggest that differences in spread of spiking and low-frequency LFPs across cortical surface influence different parameters of the hemodynamic response. Together, these results demonstrate that the hemodynamic response-amplitude is a poor correlate of spiking activity. Instead, we demonstrate that the timing of the initial-dip and the hemodynamic response are much more reliable correlates of spiking, reflecting bursts in spike-rate and total spike-counts respectively.}},
  year = {2018},
  slug = {zaidibfls2018_2},
  author = {Zaidi, AD and Birbaumer, N and Fetz, E and Logothetis, NK and Sitaram, R}
}