Visualizing the cortical representation of whisker touch: voltage-sensitive dye imaging in freely moving mice

Carl Petersen
2006
Article

Voltage-sensitive dye imaging resolves the spatiotemporal dynamics of supragranular subthreshold cortical activity with millisecond temporal resolution and subcolumnar spatial resolution. We used a flexible fiber optic image bundle to visualize voltage-sensitive dye dynamics in the barrel cortex of freely moving mice while simultaneously filming whisker-related behavior to generate two movies matched frame-by-frame with a temporal resolution of up to 2 ms. Sensory responses evoked by passive whisker stimulation lasted longer and spread further across the barrel cortex in awake mice compared to anesthetized mice. Passively evoked sensory responses were large during behaviorally quiet periods and small during active whisking. However, as an exploring mouse approached an object while whisking, large-amplitude, propagating cortical sensory activity was evoked by active whisker-touch. These experiments demonstrate that fiber optics can be used to image cortical sensory activity with high resolution in freely moving animals. The results demonstrate differential processing of sensory input depending upon behavior.

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Carl Petersen
2006
Article

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https://infoscience.epfl.ch/record/114996?ln=fr

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The rodent whisker system is a preferred model for studying plasticity in the somatosensory cortex (barrel cortex). Contrarily, only a small amount of research has been conducted to characterize the stability of neuronal population activity in the barrel cortex. We used the mouse whisker system to address the neuronal basis of stable perception in the somatosensory cortex. Cortical representation of periodic whisker deflections was studied in populations of neurons in supragranular layers over extended time periods (up to 3 months) with long-term two-photon Ca2+ imaging in anesthetized mice. We found that inmost of the neurons (87%), Ca2+ responses increased sublinearly with increasing number of contralateral whisker deflections. The imaged population of neurons was activated in a stereotypic way over days and for different deflection rates (pulse frequencies). Thus, pulse frequencies are coded by response strength rather than by distinct neuronal sub-populations. A small population of highly responsive neurons (similar to 3%) was sufficient to decode the whisker stimulus. This conserved functional map, led by a small set of highly responsive neurons, might form the foundation of stable sensory percepts. (C) 2015 Elsevier Inc. All rights reserved.

Academic Press Inc Elsevier Science2015

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Facilitating sensory responses in developing mouse somatosensory barrel cortex

Carl Petersen, James Poulet

The sensory responses in the barrel cortex of mice aged postnatal day (P)7-P12 evoked by a single whisker deflection are smaller in amplitude and spread over a smaller area than those measured in P13-P21 mice. However, repetitive 10-Hz stimulation or paired pulse whisker stimulation in P7-P12 mice evoked facilitating sensory responses, contrasting with the depressing sensory responses observed in P13-P21 mice. This facilitation occurred during an interval ranging 300-1,000 ms after the first stimulus and was measured using whole cell recordings, voltage-sensitive dye imaging, and calcium-sensitive dye imaging. The facilitated responses were not only larger in amplitude but also propagated over a larger cortical area. The facilitation could be blocked by local application of pharmacological agents reducing cortical excitability. Local cortical microstimulation could substitute for the first whisker stimulus to produce a facilitated sensory response. The enhanced sensory responses evoked by repetitive sensory stimuli in P7-P12 mice may contribute to the activity-dependent specification of the developing cortical circuits. In addition, the facilitating sensory responses allow long integration times for sensory processing compatible with the slow behavior of mice during early postnatal development.

2007

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Differential impact of polysialyltransferase ST8SiaII and ST8iaIV knockout on social interaction and aggression

Reto Bisaz, Martina Fantin, Cristina Marquez Vega, Maria del Carmen Sandi Perez

Previous studies using neuronal cell adhesion molecule (NCAM) -/- knockout (KO) mice provided evidence for a role of NCAMs in social behaviors. However, polysialic acid (PSA), the most important post-translational modification of NCAM, was also absent in these mice, which makes it difficult to distinguish between the specific involvement of either PSA or NCAM in social interactions. To address this issue, we assessed two lines of mice deficient for one of the two sialyltransferase enzymes required for the polysialylation of NCAM, sialyltransferase-X (St8SiaII or STX) and polysialyltransferase (ST8SiaIV or PST), in a series of tests for social behaviors. Results showed that PST KO mice display a decreased motivation in social interaction. This deficit can be partly explained by olfactory deficits and was associated with a clear decrease in PSA-NCAM expression in all brain regions analyzed (amygdala, septum, bed nucleus of the stria terminalis and frontal cortices). STX KO mice displayed both a decreased social motivation and an increased aggressive behavior that cannot be explained by olfactory deficits. This finding might be related to the reduced anxiety-like behavior, increased locomotion and stress-induced corticosterone secretion observed in these mice. Moreover, STX KO mice showed mild increase of PSA-NCAM expression in the lateral septum and the orbitofrontal cortex. Altogether, these findings support a role for PSA-NCAM in the regulation of social behaviors ranging from a lack of social motivation to aggression. They also underscore STX KO mice as an interesting animal model that combines a behavioral profile of violence and hyperactivity with reduced anxiety-like behavior.

Wiley-Blackwell2010

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Vibrisse

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Image resolution

Image resolution is the level of detail an holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail. Image resolution can be meas