Bhutada, A. | Search bioRxiv

bioRxiv2021

Preferential associations of soil fungal taxa under mixed compositions of eastern American tree species

Soil fungi are vital to forest ecosystem functions, in part through their role mediating tree responses to environmental factors, as well as directly through effects on resource cycling. While the distribution of these key taxa may vary with a suite of abiotic and biotic factors, the relative role of host species identity on soil fungal community composition and function remains unresolved. In this study, we used a combination of amplicon sequencing and enzymatic assays to assess soil fungal composition and associated function under three tree species, Quercus rubra, Betula nigra, and Acer rubrum, planted individually and in all combinations in a greenhouse, with added fungal inoculum collected below mature field trees. Across treatments, fungal communities were dominated by the phylum Ascomycota, followed by Basidiomycota and Mortierellomycota. Nonetheless, fungal communities differed between each of the solo planted treatments, suggesting at least some taxa may associate preferentially with these tree species. Additionally, fungal community composition under mixed sapling treatments broadly differed from solo saplings. The data also suggests that there were larger enzymatic activities in the solo treatments as compared with all mixed treatments. This difference may be due to the greater relative abundance of saprobic taxa found in the solo treatments. This study provides evidence of the importance of tree identity on soil microbial communities and functional changes to forest soils.

ecology↗

bioRxiv2021

Temporal specificity of abnormal neural oscillations during phonatory events in Laryngeal Dystonia

Laryngeal Dystonia is a debilitating disorder of voicing in which the laryngeal muscles are intermittently in spasm resulting in involuntary interruptions during speech. The central pathophysiology of laryngeal dystonia, underlying computational impairments in vocal motor control, remains poorly understood. Although prior imaging studies have found aberrant activity in the central nervous system during phonation in patients with laryngeal dystonia, it is not known at what timepoints during phonation these abnormalities emerge and what function may be impaired. To investigate this question, we recruited 22 adductor laryngeal dystonia patients (15 female, age range = 28.83-72.46 years) and 18 controls (8 female, age range = 27.40-71.34 years). We leveraged the fine temporal resolution of magnetoencephalography to monitor neural activity around glottal movement onset, subsequent voice onset and after the onset of pitch feedback perturbations. We examined event-related beta-band (12-30 Hz) and high-gamma band (65-150 Hz) neural oscillations. Prior to glottal movement onset, we observed abnormal frontoparietal motor preparatory activity. After glottal movement onset, we observed abnormal activity in somatosensory cortex persisting through voice onset. Prior to voice onset and continuing after, we also observed abnormal activity in the auditory cortex and the cerebellum. After pitch feedback perturbation onset, we observed no differences between controls and patients in their behavioural responses to the perturbation. But in patients, we did find abnormal activity in brain regions thought to be involved in the auditory feedback control of vocal pitch (premotor, motor, somatosensory and auditory cortices). Our study results confirm the abnormal processing of somatosensory feedback that has been seen in other studies. However, there were several remarkable findings in our study. First, patients have impaired vocal motor activity even before glottal movement onset, suggesting abnormal movement preparation. These results are significant because: (i) they occur before movement onset, abnormalities in patients cannot be ascribed to deficits in vocal performance, and (ii) they show that neural abnormalities in laryngeal dystonia are more than just abnormal responses to sensory feedback during phonation as has been hypothesised in some previous studies. Second, abnormal auditory cortical activity in patients begins even before voice onset, suggesting abnormalities in setting up auditory predictions before the arrival of auditory feedback at voice onset. Generally, activation abnormalities identified in key brain regions within the speech motor network around various phonation events not only provide temporal specificity to neuroimaging phenotypes in laryngeal dystonia but also may serve as potential therapeutic targets for neuromodulation.

neuroscience↗