Spatiotemporal Coordination of Slow-Wave Ongoing Activity across Auditory Cortical Areas

Abstract

Natural acoustic stimuli contain slow temporal fluctuations, and the modulation of ongoing slow-wave activity by bottom-up and top-down factors plays essential roles in auditory cortical processing. However, the spatiotemporal pattern of intrinsic slow-wave activity across the auditory cortical modality is unknown. Using in vivo voltage-sensitive dye imaging in anesthetized guinea pigs, we measured spectral tuning to acoustic stimuli across several core and belt auditory cortical areas, and then recorded spontaneous activity across this defined network. We found that phase coherence in spontaneous slow-wave (delta-theta band) activity was highest between regions of core and belt areas that had similar frequency tuning, even if they were distant. Further, core and belt regions with high phase coherence were phase shifted. Interestingly, phase shifts observed during spontaneous activity paralleled latency differences for evoked activity. Our findings suggest that the circuits underlying this intrinsic source of slow-wave activity support coordinated changes in excitability between functionally matched but distributed regions of the auditory cortical network.

Dynamic cortical representations of perceptual filling-in for missing acoustic rhythm

“…Alpha-band related effects due to non-uniform attentional states should be investigated in future studies using rhythms whose first harmonics are not in the alpha band. Our data does not reject the possibility of spontaneous and temporally patterned cortical activity profiles influencing sensory processing, as in ongoing slow-wave activity that may interact with evoked signals as a temporally coordinated modulation of excitability across distributed cortical fields 52,53 .…”

Membrane potential dynamics of populations of cortical neurons during auditory streaming

“…The data from this study come from 12 male and female adult guinea pigs (Dunkin Hartley breed from Charles River Laboratories, Wilmington, MA). Experimental procedures for VSDI have been described previously (Farley and Noreña 2013). Immediately before surgery, each animal was checked for the presence of a bilateral pinnal reflex in response to sound.…”

“…All data are displayed as percent change in fluorescence over the baseline fluorescence value for each pixel (⌬F/F). Artifacts related to ECG and respiration were calculated using previously established methods (Farley and Noreña 2013;Lippert et al 2007). However, their effects on best-frequency measurements and streaming paradigm responses (following trial averaging) were negligible and so, were not treated.…”

“…For the measurement of best-frequency tuning, data acquisition comprised ϳ120 total s, during which the multitone stimulus (see above) was presented. Receptive fields were derived individually for each pixel by forward correlation, i.e., calculating the average response time locked to the onset of tone pips of each frequency (Farley and Noreña 2013;Valentine and Eggermont 2004). The best frequency of a pixel was then defined as the frequency eliciting the maximal response, across all frequencies and latencies.…”

“…Previous studies combining VSDI with whole-cell voltage recordings have established that when applied to the mammalian cortex in vivo, VSDI measures a population subthreshold membrane potential-related signal (as opposed to spiking activity) from neural elements within the superficial layers of the cortex (Peterson et al 2003). VSDI thus permits the measuring of subthreshold membrane potential-related activity at high spatial and temporal resolution across the auditory cortex (Farley and Noreña 2013).…”