The role of the odorant receptors in the formation of the sensory map

In the olfactory system, odorant receptors (ORs) expressed at the cell membrane of olfactory sensory neurons detect odorants and direct sensory axons toward precise target locations in the brain, reflected in the presence of olfactory sensory maps. This dual role of ORs is corroborated by their subcellular expression both in cilia, where they bind odorants, and at axon terminals, a location suitable for axon guidance cues. Here, we provide an overview and discuss previous work on the role of ORs in establishing the topographic organization of the olfactory system and recent findings on the mechanisms of activation and function of axonal ORs.

Adapting Polarized Projective Mapping to Investigate Fruitiness Aroma Perception of White Wines from Oregon

Fruitiness is a highly desirable aroma quality in white wines. This study aimed to investigate the fruitiness aroma perception of white wines using a rapid sensory method and to compare the sensory maps obtained from wine experts and trained consumers. A polarized projective mapping (PPM) method was adapted by using fruit standards as fixed poles. Twenty-one white wines were selected for this study. Ten wine experts and twelve trained consumers participated in the adapted PPM followed by ultra-flash profiling (UFP). While experts and trained consumers used different poles to characterize the Pinot Gris and Viogniers, both panels used the stone fruit pole for the Chardonnays. UFP revealed that the Pinot Gris and Viognier samples presented fruity and floral aromas and most Chardonnay wines presented non-fruity aromas. The white wines investigated presented a wide range of fruity aromas. The use of aroma standards instead of products as poles seems to be a reliable alternative to investigate fruitiness in white wines. This study helped us to understand the predominant aromas of varietal white wines from Oregon and emphasized the importance of adapting sensory methods to investigate fruitiness perception.

Registry of Compartmental Ephrin-B3 Guidance Patterns With Respect to Emerging Multimodal Midbrain Maps

Guidance errors and unrefined neural map configurations appear linked to certain neurodevelopmental conditions, including autism spectrum disorders. Deficits in specific multisensory tasks that require midbrain processing are highly predictive of cognitive and behavioral phenotypes associated with such syndromes. The lateral cortex of the inferior colliculus (LCIC) is a shell region of the mesencephalon that integrates converging information from multiple levels and modalities. Mature LCIC sensory maps are discretely-organized, mimicking its compartmental micro-organization. Intermittent modular domains receive patchy somatosensory connections, while inputs of auditory origin terminate in the encompassing extramodular matrix.Eph-ephrin signaling mechanisms instruct comparable topographic arrangements in a variety of other systems. Whether Eph-ephrin interactions also govern the assembly of LCIC multimodal maps remains unaddressed. Previously, we identified EphA4 and ephrin-B2 as key mediators, with overlapping expression patterns that align with emerging LCIC modules. Here, we implicate another member of this guidance family, ephrin-B3, and quantify its transient expression with respect to neurochemically-defined LCIC compartments. Multiple-labeling studies in GAD67-GFP knock-in mice reveal extramodular ephrin-B3 expression, complementary to that of EphA4 and ephrin-B2. This distinctive pattern sharpens over the early postnatal period (birth to P8), prior to ephrin-B3 downregulation once multimodal LCIC inputs are largely segregated (P12). Channel-specific sampling of LCIC ROIs show ephrin-B3 signal periodicities that are out-of-phase with glutamic acid decarboxylase (GAD;modular marker) signal fluctuations, and match calretinin (CR) waveforms (matrix marker). Taken together, the guidance mosaic registry with emerging LCIC compartments and its interfacing afferent streams suggest a prominent role for Eph-ephrins in ordering behaviorally significant multisensory midbrain networks.

Multivariate Analysis of Olfactory Profiles for 140 Perfumes as a Basis to Derive a Sensory Wheel for the Classification of Feminine Fragrances

In order to guide consumers in their purchase of a new fragrance, one approach is to visualize the spectrum of men’s or women’s fragrances on a two-dimensional plot. One of such sensory maps available is the Hexagon of Fragrance Families. It displays 91 women’s perfumes inside a polygon, so that each side accounts for a different olfactory class. In order to discuss this chart, odor profiles were obtained for these fragrances and additional feminine ones (140 in total, launched from 1912 to 1990). An olfactory dataset was arranged by coding numerically the descriptions obtained from Fragrantica and Osmoz websites, as well as from a perfume guide. By applying principal component analysis, a sensory map was obtained that properly reflected the similarities between odor descriptors. Such representation was equivalent to the map of feminine fragrances called Givaudan Analogies, comprised of five major categories. Based on the results, a modified version of the Hexagon based on 14 categories was proposed. The first principal component explained preference for daytime versus nighttime wear, and regression models were fitted in order to estimate such preferences according to the odor profiles. The second component basically discriminated floral versus chypre (mossy–woody) fragrances. Results provide a fundamental basis to develop standard sensory maps of women’s fragrances.

Scrambling the skin: Simulated Skin Re-Arrangement Using Apparent Motion

I.ABSTRACTAn age-old hypothesis proposes that object motion across the receptor surface organizes sensory maps (Lotze, 19th century). Skin patches learn their relative positions from the order in which they are stimulated during motion events. We test this idea by reversing the local motion within a 6-point apparent motion sequence along the forearm. In the ‘Scrambled’ sequence, two middle locations were touched in reversed order (1-2-4-3-5-6, followed by 6-5-3-4-2-1, in a continuous loop). This created a local acceleration, a double U-turn, within an otherwise constant-velocity motion, as if the physical location of skin patches 3 and 4 was surgically swapped. The control condition, ‘Orderly’, proceeded at constant velocity at inter-stimulus onset interval (ISOI) of 120 ms. In the test, our twenty participants reported motion direction between the two middle tactors, presented on their own at 75, 120 or 190-ms ISOI. Results show degraded motion discrimination following exposure to Scrambled pattern: for the 120-ms test stimulus, it was 0.31 d’ weaker than following Orderly conditioning (p = .007). This is the aftereffect we expected; its maximal expression would be a complete reversal in perceived motion direction between locations 3 and 4 for either motion direction. We propose that the somatosensory system was beginning to ‘correct’ reversed local motion to uncurl and remove the U-turns that always occurred on the same part of the receptor surface. Such de-correlation between accelerations and their location on the sensory surface is one possible mechanism for organization of sensory maps.

Body map proto-organization in newborn macaques

Topographic sensory maps are a prominent feature of the adult primate brain. Here, we asked whether topographic representations of the body are present at birth. Using functional MRI (fMRI), we find that the newborn somatomotor system, spanning frontoparietal cortex and subcortex, comprises multiple topographic representations of the body. The organization of these large-scale body maps was indistinguishable from those in older monkeys. Finer-scale differentiation of individual fingers increased over the first 2 y, suggesting that topographic representations are refined during early development. Last, we found that somatomotor representations were unchanged in 2 visually impaired monkeys who relied on touch for interacting with their environment, demonstrating that massive shifts in early sensory experience in an otherwise anatomically intact brain are insufficient for driving cross-modal plasticity. We propose that a topographic scaffolding is present at birth that both directs and constrains experience-driven modifications throughout somatosensory and motor systems.

Hand size underestimation grows during childhood

Cortical body size representations are distorted in the adult, from low-level motor and sensory maps to higher levels multisensory and cognitive representations. Little is known about how such representations are built and evolve during infancy and childhood. Here we investigated how hand size is represented in typically developing children aged 6 to 10. Participants were asked to estimate their hand size using two different sensory modalities (visual or haptic). We found a distortion (underestimation) already present in the youngest children. Crucially, such distortion increases with age and regardless of the sensory modality used to access the representation. Finally, underestimation is specific for the body as no bias was found for object estimation. This study suggests that the brain does not keep up with the natural body growth. However, since motor behavior nor perception were impaired, the distortion seems functional and/or compensated for, for proper interaction with the external environment.

Enrichment drives emergence of functional columns and improves sensory coding in the whisker map in L2/3 of mouse S1

Sensory maps in layer (L) 2/3 of rodent cortex lack precise functional column boundaries, and instead exhibit locally heterogeneous (salt-and-pepper) tuning superimposed on smooth global topography. Could this organization be a byproduct of impoverished experience in laboratory housing? We compared whisker map somatotopy in L2/3 and L4 excitatory cells of somatosensory (S1) cortex in normally housed vs. tactile-enriched mice, using GCaMP6s imaging. Normally housed mice had a dispersed, salt-and-pepper whisker map in L2/3, but L4 was more topographically precise. Enrichment (P21 to P46-71) sharpened whisker tuning and decreased, but did not abolish, local tuning heterogeneity. In L2/3, enrichment strengthened and sharpened whisker point representations, and created functional boundaries of tuning similarity and noise correlations at column edges. Thus, enrichment drives emergence of functional columnar topography in S1, and reduces local tuning heterogeneity. These changes predict better touch detection by neural populations within each column.

Embryonic Brain’s Spontaneous Activity Promote Synesthesia?

Antón-Bolaños et al. (2019) report a newly identified neural pathway mechanism, where the patterned spontaneous activity regulates the excitability of a neural network essential for the formation and maintenance of functional sensory maps in the brain. Findings from the study suggest that the patterned spontaneous activity prevalent during the embryonic development of the brain; at the early stages of innervation to the cortex, contributes to the formation of these sensory maps. Synesthesia is a neural phenomenon caused by the unusual links between sensory information, where synesthetic subjects demonstrate atypical functional and neural connectivity caused by the differences in cortical wiring during brain development. So, based on the findings from Antón-Bolaños et al. (2019), one can anticipate the role of spontaneous activity in promoting synesthetic condition. Thus, it will be interesting to study, if the intrinsic spontaneous activity influences the differential cortical wiring and the formation of sensory maps in synesthesia.

Body-map proto-organization in newborn macaques

ABSTRACTTopographic sensory maps are a prominent feature of the adult primate brain. Here, we asked whether topographic representations of the environment are fundamental to early development. Using fMRI, we find that the newborn somato-motor system, spanning frontoparietal cortex and subcortex, comprises multiple topographic body representations. The organization of these large-scale body maps was indistinguishable from those in adults and already exhibited features stereotypical of adult maps. Finer-scale differentiation of individual fingers increased over the first two years, suggesting that topographic representations are refined during early development. Last, we found that somato-motor representations were unchanged in two visually impaired monkeys who relied entirely on touch for interacting with their environment, demonstrating that massive shifts in early sensory experience in an otherwise anatomically intact brain are not sufficient for driving cross-modal plasticity. We propose that a topographic scaffolding is present at birth that both directs and constrains experience-driven modifications throughout sensory systems.