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Leuven, Belgium

Dreosti E.,University College London | Vendrell Llopis N.,NERF | Vendrell Llopis N.,Catholic University of Leuven | Carl M.,University College London | And 4 more authors.
Current Biology | Year: 2014

Left-right asymmetries are most likely a universal feature of bilaterian nervous systems and may serve to increase neural capacity by specializing equivalent structures on left and right sides for distinct roles [1]. However, little is known about how asymmetries are encoded within vertebrate neural circuits and how lateralization influences processing of information in the brain. Consequently, it remains unclear the extent to which lateralization of the nervous system is important for normal cognitive and other brain functions and whether defects in lateralization contribute to neurological deficits [2]. Here we show that sensory responses to light and odor are lateralized in larval zebrafish habenulae and that loss of brain asymmetry leads to concomitant loss of responsiveness to either visual or olfactory stimuli. We find that in wild-type zebrafish, most habenular neurons responding to light are present on the left, whereas neurons responding to odor are more frequent on the right. Manipulations that reverse the direction of brain asymmetry reverse the functional properties of habenular neurons, whereas manipulations that generate either double-left- or double-right-sided brains lead to loss of habenular responsiveness to either odor or light, respectively. Our results indicate that loss of brain lateralization has significant consequences upon sensory processing and circuit function. © 2014 The Authors. Source


Vendrell-Llopis N.,NERF | Vendrell-Llopis N.,Catholic University of Leuven | Yaksi E.,NERF | Yaksi E.,Catholic University of Leuven | Yaksi E.,Norwegian University of Science and Technology
Scientific Reports | Year: 2015

Evolutionary conserved brainstem circuits are the first relay for gustatory information in the vertebrate brain. While the brainstem circuits act as our life support system and they mediate vital taste related behaviors, the principles of gustatory computations in these circuits are poorly understood. By a combination of two-photon calcium imaging and quantitative animal behavior in juvenile zebrafish, we showed that taste categories are represented by dissimilar brainstem responses and generate different behaviors. We also showed that the concentration of sour and bitter tastes are encoded by different principles and with different levels of sensitivity. Moreover, we observed that the taste mixtures lead to synergistic and suppressive interactions. Our results suggest that these interactions in early brainstem circuits can result in non-linear computations, such as dynamic gain modulation and discrete representation of taste mixtures, which can be utilized for detecting food items at broad range of concentrations of tastes and rejecting inedible substances. Source


Jetti S.K.,NERF | Jetti S.K.,Catholic University of Leuven | Vendrell-Llopis N.,NERF | Vendrell-Llopis N.,Catholic University of Leuven | And 2 more authors.
Current Biology | Year: 2014

The medial habenula relays information from the sensory areas via the interpeduncular nucleus [1, 2] to the periaqueductal gray that regulates animal behavior under stress conditions [3]. Ablation of the dorsal habenula (dHb) in zebrafish, which is equivalent to the mammalian medial habenula, was shown to perturb experience-dependent fear [4, 5]. Therefore, understanding dHb function is important for understanding the neural basis of fear. In zebrafish, the dHb receives inputs from the mitral cells (MCs) of the olfactory bulb (OB) [6], and odors can trigger distinct behaviors (e.g., feeding, courtship, alarm) [7]. However, it is unclear how the dHb processes olfactory information and how these computations relate to behavior. In this study, we demonstrate that the odor responses in the dHb are asymmetric and spatially organized despite the unorganized OB inputs. Moreover, we show that the spontaneous dHb activity is not random but structured into functionally and spatially organized clusters of neurons, which reflects the favored states of the dHb network. These dHb clusters are also preserved during odor stimulation and govern olfactory responses. Finally, we show that functional dHb clusters overlap with genetically defined dHb neurons [4], which regulate experience-dependent fear. Thus, we propose that the dHb is composed of functionally, spatially, and genetically distinct microcircuits that regulate different behavioral programs. © 2014 Elsevier Ltd. Source

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