The Olfactory System Revealed: Non-Invasive Mapping by using Constrained Spherical Deconvolution Tractography in Healthy Humans

Abstract

Although the olfactory sense has always been considered with less interest than the visual, auditive or somatic senses, it does plays a major role in our ordinary life, with important implication in dangerous situations or in social and emotional behaviors. Traditional Diffusion Tensor signal model and related tractography have been used in the past years to reconstruct the cranial nerves, including the olfactory nerve (ON). However, no supplementary information with regard to the pathways of the olfactory network have been provided. Here, by using the more advanced Constrained Spherical Deconvolution (CSD) diffusion model, we show for the first time in vivo and non-invasively that, in healthy humans, the olfactory system has a widely distributed anatomical network to several cortical regions as well as to many subcortical structures. Although the present study focuses on an healthy sample size, a similar approach could be applied in the near future to gain important insights with regard to the early involvement of olfaction in several neurodegenerative disorders.

Structural connectivity‐based topography of the human globus pallidus: Implications for therapeutic targeting in movement disorders

“…More recently, we used constrained spherical deconvolution (CSD)‐based tractography, a diffusion MRI‐based technique allowing in vivo reconstruction of connectivity patterns between nervous structures, to study the human analogues of the above‐mentioned direct cortico‐ and dento‐pallidal projections . These connections, likely paralleled by analogue cortico‐ and dento‐nigral pathways, may exert a converging influence of cerebral and neocerebellar cortex on the basal ganglia output nuclei.…”

“…13,14 This scenario has been widely expanded since anatomical studies using retrograde virus tracing demonstrated bidirectional subcortical connections between cerebellum and basal ganglia. 15,16 More recently, we used constrained spherical deconvolution (CSD)-based tractography, a diffusion MRI-based technique allowing in vivo reconstruction of connectivity patterns between nervous structures, [17][18][19][20][21] to study the human analogues of the above-mentioned direct cortico- 22 and dento-pallidal projections. 23 These connections, likely paralleled by analogue cortico- 24 and dento-nigral 23,25 pathways, may exert a converging influence of cerebral and neocerebellar cortex on the basal ganglia output nuclei.…”

Rhinocerebral mucormycosis with dissemination to pontine area in a diabetic patient: Treatment and management

“…In a recent review about 929 cases of zygomycosis, survival was 3% (8 of 241 patients) for cases that were not treated, 61% (324 of 532) for cases treated with amphotericin B deoxycholate, 57% (51 of 90) for cases treated with surgery alone, and 70% (328 of 470) for cases treated with antifungal therapy and surgery …”

Functional connectome analyses reveal a highly optimized human olfactory network

“…The largely subcortical composition of the olfactory system, with many loci at the air-tissue interface, has presented a serious challenge to olfactory network identification, especially for unguided, whole-brain rs-fMRI connectivity analysis. However, important insights into the olfactory network have been gained by targeting olfactory regions of interest (ROIs) (Plailly et al, 2008;Krusemark and Li, 2012;Krusemark et al, 2013;Sunwoo et al, 2015;Kollndorfer et al, 2015;Novak et al, 2015;Karunanayaka et al, 2017;Milardi et al, 2017;Fjaeldstad et al, 2017;Cecchetto et al, 2019), especially in combination with network-science analysis (Meunier et al, 2014;Royet et al, 2011;Ripp et al, 2018;Zhou et al, 2019). The olfactory ROIs are fairly reliably identified, but inconsistencies in network composition and connections also abound in this literature (Fjaeldstad et al, 2017;Cecchetto et al, 2019).…”