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bioRxiv · 10.1101/269696

The timing of hemodynamic changes reliably reflects spiking activity

Zaidi, A. D.·Birbaumer, N.·Fetz, E.·Logothetis, N.·SItaram, R.
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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 signals 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.

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Zaidi, A. D., Birbaumer, N., Fetz, E., Logothetis, N., SItaram, R.. 2018-02-22. The timing of hemodynamic changes reliably reflects spiking activity. https://doi.org/10.1101/269696

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