Faculty Bibliography

Connecting neuronal activity to perception requires tools that can probe neural codes at cellular and circuit levels, paired with sensitive behavioral measures. In this chapter, we present an overview of current methods for connecting neural codes to perception using precision optogenetics and psychophysical measurements of synthetically induced percepts. We also highlight new methodologies for validating precise control of optical and behavioral manipulations. Finally, we provide a perspective on upcoming developments that are poised to advance the field.
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Modern optical neuroimaging approaches are expanding the ability to elucidate complex brain function. Diverse imaging contrasts enable direct observation of neural activity with functional sensors along with the induced hemodynamic responses. To date, decoupling the complex interplay of neurovascular coupling and dynamical physiological states has remained challenging when employing single-modality functional neuroimaging readings. A hybrid fluorescence optoacoustic tomography platform combined with a custom data processing pipeline based on statistical parametric mapping is devised, attaining the first noninvasive observation of simultaneous calcium and hemodynamic activation patterns using optical contrasts. Correlated changes in the oxy- and deoxygenated hemoglobin, total hemoglobin, oxygen saturation, and rapid GCaMP6f fluorescence signals are observed in response to peripheral sensory stimulation. While the concurrent epifluorescence serves to corroborate and complement the functional optoacoustic observations, the latter further aids in decoupling the rapid calcium responses from the slowly varying background in the fluorescence recordings mediated by hemodynamic changes. The hybrid imaging platform expands the capabilities of conventional neuroimaging methods to provide more comprehensive functional readings for studying neurovascular and neurometabolic coupling mechanisms and related diseases.

[Figure: see text].

Ultrasound can be delivered transcranially to ablate brain tissue, open the blood-brain barrier, or affect neural activity. Transcranial focused ultrasound in small rodents is typically done with low-frequency single-element transducers, which results in unspecific targeting and impedes the concurrent use of fast neuroimaging methods. In this article, we devised a wide-angle spherical array bidirectional interface for high-resolution parallelized optoacoustic imaging and transcranial ultrasound (POTUS) delivery in the same target regions. The system operates between 3 and 9 MHz, allowing to generate and steer focal spots with widths down to [Formula: see text] across a field of view covering the entire mouse brain, while the same array is used to capture high-resolution 3-D optoacoustic data in real time. We showcase the system's versatile beam-forming capacities as well as volumetric optoacoustic imaging capabilities and discuss its potential to noninvasively monitor brain activity and various effects of ultrasound emission.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Animals are capable of detecting odorants in a single sniff, at extremely low concentrations. This ability is crucial for survival, yet it is unknown how the olfactory system supports detection at the perceptual limit. In the mouse olfactory bulb, inhalation of different odors leads to changes in the set of neurons activated, as well as when neurons are activated relative to each other (synchrony), and the onset of inhalation (latency). A key question is which features of stimulus evoked activity (e.g. rate, synchrony, or latency) are used to guide detection behavior? Here, we probed the sensitivity of mice to perturbations across each stimulus dimension using holographic two-photon (2P) optogenetic stimulation of olfactory bulb neurons, with cellular and single action potential resolution and millisecond precision. We found that mice can detect single action potentials evoked synchronously across <20 olfactory bulb neurons. Mice exhibited this sensitivity for artificial ensembles of mitral cells, as well as mixed ensembles of mitral and granule cells. Further, we discovered that detection depends strongly on the synchrony of activation across neurons, with detectability falling to near-chance levels with an imposed stimulus spread 3 30 ms, while detection performance was minimally perturbed by changes in the latency of activation relative to inhalation. These results reveal that mice are acutely attuned to single neurons and action potentials in olfactory circuits, and that synchrony across neurons may be a critical feature supporting the perceptibility of sparse ensemble activity signals