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Accueil du site > Equipes de recherche > Equipe CMO (N.Ravel, N.Buonviso) > Annuaire > Pages personnelles > Philippe LITAUDON


par Philippe Litaudon - 18 mars 2013


  • Litaudon P, Bouillot C, Zimmer L, Costes N, Ravel N. Activity in the rat olfactory cortex is correlated with behavioral response to odor: a microPET study. Brain Structure & Function. 222(1):577-586.
    Résumé : How olfactory cortical areas interpret odor maps evoked in the olfactory bulb and translate odor information into behavioral responses is still largely unknown. Indeed, rat olfactory cortices encompass an extensive network located in the ventral part of the brain, thus complicating the use of invasive functional methods. In vivo imaging techniques that were previously developed for brain activation studies in humans have been adapted for use in rodents and facilitate the non-invasive mapping of the whole brain. In this study, we report an initial series of experiments designed to demonstrate that microPET is a powerful tool to investigate the neural processes underlying odor-induced behavioral response in a large-scale olfactory neuronal network. After the intravenous injection of [18F]Fluorodeoxyglucose ([18F]FDG), awake rats were placed in a ventilated Plexiglas cage for 50 min, where odorants were delivered every 3 min for a 10-s duration in a random order. Individual behavioral responses to odor were classified into categories ranging from 1 (head movements associated with a short sniffing period in response to a few stimulations) to 4 (a strong reaction, including rearing, exploring and sustained sniffing activity, to several stimulations). After [18F]FDG uptake, rats were anesthetized to perform a PET scan. This experimental session was repeated 2 weeks later using the same animals without odor stimulation to assess the baseline level of activation in each individual. Two voxel-based statistical analyses (SPM 8) were performed: (1) a two-sample paired t test analysis contrasting baseline versus odor scan and (2) a correlation analysis between voxel FDG activity and behavioral score. As expected, the contrast analysis between baseline and odor session revealed activations in various olfactory cortical areas. Significant increases in glucose metabolism were also observed in other sensory cortical areas involved in whisker movement and in several modules of the cerebellum involved in motor and sensory function. Correlation analysis provided new insight into these results. [18F]FDG uptake was correlated with behavioral response in a large part of the anterior piriform cortex and in some lobules of the cerebellum, in agreement with the previous data showing that both piriform cortex and cerebellar activity in humans can be driven by sniffing activity, which was closely related to the high behavioral scores observed in our experiment. The present data demonstrate that microPET imaging offers an original perspective for rat behavioral neuroimaging.
    Mots-clés : Animals, Brain, Fluorodeoxyglucose F18, Male, MicroPET, Odorants, Olfaction, Olfactory Cortex, Olfactory Perception, Piriform cortex, Positron-Emission Tomography, Rats, Rats, Wistar, Sniffing, [18F]Fluorodeoxyglucose.

  • Martinez D, Clement M, Messaoudi B, Gervasoni D, Litaudon P, Buonviso N. Adaptive quantization of local field potentials for wireless implants in freely moving animals: an open-source neural recording device. Journal of Neural Engineering. 2017.
    Résumé : OBJECTIVE: Modern neuroscience research asks for electrophysiological recording of local field potentials (LFPs) in moving animals. Wireless transmission has the advantage of removing the wires between the animal and the recording equipment but is hampered by the large amount of data to be sent at a relatively high rate. APPROACH: To reduce transmission bandwidth, we propose an encoder/decoder scheme based on adaptive non-uniform quantization. Our algorithm uses the current transmitted codeword to adapt the quantization intervals to changing statistics in LFP signals. It is thus backward adaptive and does not require sending side information. The computational complexity is low and similar at the encoder and decoder side. These features allow for real-time signal recovery and facilitate hardware implementation with low-cost commercial microcontrollers. MAIN RESULTS: As proof-of-concept, we developed an open-source Neural Recording Device called NeRD. The NeRD prototype digitally transmits 8 channels encoded at 10 kHz with 2 bits per sample. It occupies a volume of 2 × 2 × 2 cm3 and weighs 8 grams with a small battery allowing for 2 hours 40 min of autonomy. The power dissipation is 59.4 mW for a communication range of 8 m and transmission losses below 0.1%. The small weight and low power consumption offers the possibility to mount the entire device on the head of rodents without resorting to separate head-stage and battery backpack. The NeRD prototype is validated in recording LFPs in freely moving rats at 2 bits per sample while maintaining an acceptable signal-to-noise ratio (>30 dB) over a range of noisy channels. SIGNIFICANCE: Adaptive quantization in neural implants allows for lower transmission bandwidths while retaining high signal fidelity and preserving fundamental frequencies in LFPs.
    Mots-clés : Local field potential, Neural implants, Neural telemetry, Neurophysiology, Neurotechnology, Wireless transmission.