From: olivercranglejr@gmail.com   
      
   Ultrasound tracks odor representation in the brain   
      
      
       
   Jul 14, 2014   
      
   On these images, the cerebral activation detected by ultrasound imaging is   
   shown in red. During odor presentation, specific areas are activated in the   
   olfactory bulb but not in the piriform cortex. © Mickael Tanter / Hirac   
   Gurden[Sur ces images, l'   
   activation cérébrale détectée par imagerie ultrasonore est visualisée en   
   rouge. A la présentation d'une odeur donnée, des territoires spécifiques sont   
   sollicités dans le bulbe olfactif mais pas dans le cortex piriforme. © Michaël   
   Tanter / Hirac Gurden][   
   Sur ces images, l'activation cérébrale détectée par imagerie ultrasonore est   
   visualisée en rouge. A la présentation d'une odeur donnée, des territoires   
   spécifiques sont sollicités dans le bulbe olfactif mais pas dans le cortex   
   piriforme. Credit: Michaël    
   Tanter / Hirac Gurden   
   A new ultrasound imaging technique has provided the first ever in vivo   
   visualization of activity in the piriform cortex of rats during odor   
   perception.. This deep-seated brain structure plays an important role in   
   olfaction, and was inaccessible to    
   functional imaging until now. This work also sheds new light on the still   
   poorly known functioning of the olfactory system, and notably how information   
   is processed in the brain. This study is the result of a collaboration between   
   the team led by Mickael    
   Tanter at the Institut Langevin (CNRS/INSERM/ESPCI ParisTech/UPMC/Université   
   Paris Diderot) and that led by Hirac Gurden in the Laboratoire Imagerie et   
   Modélisation en Neurobiologie et Cancérologie (CNRS/Université P   
   ris-Sud/Université Paris Diderot).    
   Their findings are published in NeuroImage dated July 15, 2014.   
   How can the perception of the senses help represent the external environment?   
   How, for example, does the brain process food- or perfume-related olfactory   
   data? Although the organization of the olfactory system is well known - it is   
   similar in organisms    
   ranging from insects to mammals - its functioning remains unclear. To answer   
   these questions, the scientists focused on the two brain structures that act   
   as major olfactory relays: the olfactory bulb and the piriform cortex. In the   
   rat, the olfactory    
   bulb is located between the eyes, just behind the nasal bone. The piriform   
   cortex, meanwhile, is deep-seated in the brain of rodents, which made it   
   impossible to obtain any functional images in a living animal until now.   
   Yet the neurofunctional ultrasound imaging technique developed by Mickael   
   Tanter's team, called fUS (functional Ultrasound), allows the monitoring of   
   neuronal activity in the piriform cortex. It is based on the transmission of   
   ultrasonic plane waves into    
   the brain tissue. After data processing, the echoes returned by the structures   
   crossed by these waves can provide images with unequalled spatial and temporal   
   resolution: 80 micrometers and a few tens of milliseconds. The contrast on   
   these images is due    
   to variations in the brain's blood flow. Indeed, the activity of nerve cells   
   requires an input of energy: it is therefore coupled to an influx of blood   
   into the zone concerned. By recording volume variations in the blood vessels   
   irrigating the different    
   brain structures, it is therefore possible to determine the location of   
   activated neurons.   
      
   Several imaging techniques, such as MRI, are already based on the link between   
   blood volume and neuronal activity. But fUS offers advantages in terms of   
   cost, ease of use and resolution. Furthermore, it provides easier access to   
   the deepest structures    
   that are often located several centimeters beneath the cranium.   
      
   The recordings performed by Hirac Gurden's team using this technique made it   
   possible to observe the spatial distribution of activity within the olfactory   
   bulb. When an odor was perceived, blood volume increased in clearly defined   
   areas: each odor thus    
   corresponded to a specific pattern of activated neurons. In addition to these   
   findings, and for the first time, the images revealed an absence of spatial   
   distribution in the piriform cortex. At this level, two different odors   
   triggered the same    
   activation throughout the region.   
      
   The cellular mechanisms responsible for the disappearance of a spatial   
   signature are not yet clearly defined, but these findings lead to the   
   formulation of several hypotheses. The piriform cortex could be a structure   
   that serves not only to process    
   olfactory stimuli but rather to integrate and memorize different types of   
   data. By making abstraction of the strict odor-induced patterns, it would be   
   possible to make associations and achieve a global concept. For example, based   
   on the perception of the    
   hundreds of odorant molecules found in coffee, the piriform cortex would be   
   able to recognize a single odor, that of coffee.   
      
   This work opens new perspectives for both imaging and neurobiology. The   
   researchers will now be focusing on the effects of learning on cortical   
   activity in order to elucidate its role and the specificities of the olfactory   
   system.   
      
       
   More information: "Functional ultrasound imaging reveals different odor-evoked   
   patterns of vascular activity in the main olfactory bulb and the anterior   
   piriform cortex." B.F. Osmanski, C. Martin, G. Montaldo, P. Lanièce, F. Pain,   
   M. Tanter, H.. Gurden.    
   NeuroImage 2014. 95C:176-184. DOI : dx.doi.org/10.1016/j.neuroimage.2014.03.054   
      
   Provided by CNRS   
      
   Explore further   
      
      
   Map of brain connections provides insight into olfactory system   
      
   May 16th, 2014   
      
       
       
       
      
      
   http://m.medicalxpress.com/news/2014-07-ultrasound-tracks-odor-r   
   presentation-brain.html   
      
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