Spontaneous Infra-slow Brain Activity Has Unique Spatiotemporal Dynamics and Laminar Structure

Abstract

Summary Systems-level organization in spontaneous infra-slow (<0.1Hz) brain activity, measured using blood oxygen signals in fMRI and optical imaging, has become a major theme in the study of neural function in both humans and animal models. Yet the neurophysiological basis of infra-slow activity (ISA) remains unresolved. In particular, is ISA a distinct physiological process, or is it a low frequency analogue of faster neural activity? Here, using whole-cortex calcium/hemoglobin imaging in mice, we show that ISA in each of these modalities travels through the cortex along stereotypical spatio-temporal trajectories that are state-dependent (wake versus anesthesia) and distinct from trajectories in delta (1–4Hz) activity. Moreover, mouse laminar electrophysiology reveals that ISA travels through specific cortical layers and is organized into unique cross-laminar temporal dynamics that are different from higher frequency local field potential activity. These findings suggest that ISA is a distinct neurophysiological process that is reflected in fMRI blood oxygen signals.

Brain states govern the spatio-temporal dynamics of resting state functional connectivity

“…The occurrence of these events, down-up transitions, or slow waves, are not occurring in a regular, oscillation-like manner, but depend on the overall physiological state of the animal, such as the depth of anesthesia 5 . Although, there is abundant evidence on the relevance of infra-slow electrical brain activity for resting state connectivity 34,65,66 , there has been no direct neural evidence so far linking brain states to changes in network configuration.…”

“…The concept of brain states as defined by the local and global features of network dynamics by no means entails, that different behavioral states as e.g. anesthetized condition or natural sleep would be identical, however, defining features of the slow wave state, such as bimodality, can be identified in a plethora of different conditions 19,24,34,35 as the fundamental difference between fast and slow timescale cortical dynamics is likely regulated by distinct mechanisms at the single neuron level 36 .…”

Measurement of ultra‐fast signal progression related to face processing by 7T fMRI

“…In addition, a recent fMRI study has revealed differences in the cortical layer involving the propagation of slow spontaneous activities. This suggests a similar asymmetry, as the spontaneous activity may occur in fast signal processing if the fast stimuli‐driven signal processing is based on the signal processing mechanism in the resting state (Mitra et al, ). The existence of this kind of asymmetry is further supported by an asymmetry seen in white matter structure, in which the volume of the right inferior longitudinal fasciculus was observed to be larger than that of the left ILF (Latini et al, ), supporting our inference of asymmetry in the IHTT.…”

Seizure susceptibility and infraslow modulatory activity in the intracranial electroencephalogram

“…The same study also reports that the phase of infraslow fluctuations is coupled to the amplitude of delta band activity, suggesting a hierarchical organization in which infraslow activity exerts a modulatory influence on higher frequency activity. 3 Interestingly, it has been reported that these infraslow oscillations, which seem to be present widely across cortex, may also modulate general cortical excitability and affect the frequency of interictal epileptic discharges. 4 Subsequent work has also shown that infraslow changes may have some utility in lateralizing, and in some cases, localizing seizure activity.…”