Biology subjects

Mahmud, M.

Publications and source records attributed to Mahmud, M..

2 recordsLinked to original sources

bioRxiv2024

Vestibular prepulse inhibition of the human blink reflex

ObjectiveAuditory and somatosensory prepulses are commonly used to assess prepulse inhibition (PPI). The effect of a vestibular prepulse upon blink reflex (BR) excitability has not been hitherto assessed. MethodsTwenty-two healthy subjects and two patients with bilateral peripheral vestibular failure took part in the study. Whole body yaw rotation in the dark provided a vestibular inertial prepulse. BR was electrically evoked after the end of the rotation. The area-under-the-curve (area) of the BR responses (R1, R2, and R2c) was recorded and analysed. ResultsA vestibular prepulse inhibited the R2 (p < 0.001) and R2c area (p < 0.05). Increasing the angular acceleration did not increase the R2/R2c inhibition (p>0.05). Voluntary suppression of the vestibular-ocular reflex did not affect the magnitude of inhibition (p>0.05). Patients with peripheral vestibular failure did not show any inhibition. ConclusionsOur data support a vestibular-gating mechanism in humans. SignificanceThe main brainstem nucleus mediating PPI - the pedunculopontine nucleus (PPN) - is heavily vestibular responsive, which is consistent with our findings of a vestibular-mediated PPI. Our technique may be used to interrogate the fidelity of brain circuits mediating vestibular-related PPN functions. Given the PPNs importance in human postural control, our technique may also provide a neurophysiological biomarker of balance. HighlightsO_LIThis is the first report of a vestibular prepulse inhibition of the blink reflex. C_LIO_LIA vestibular prepulse inhibits the R2/R2c area in healthy subjects but not in patients with bilateral peripheral vestibular failure. C_LIO_LIVestibular PPI is a potential neurophysiological marker of vestibular-motor integration at the brainstem level. C_LI

neuroscience↗

bioRxiv2019

Intercontinental genomic parallelism in multiple adaptive radiations

Parallelism, the evolution of similar traits in populations diversifying in similar conditions, provides good evidence of adaptation by natural selection. Many studies of parallelism have focused on comparisons of strongly different ecotypes or sharply contrasting environments, defined a priori, which could upwardly bias the apparent prevalence of parallelism. Here, we estimated genomic parallelism associated with individual components of environmental and phenotypic variation at an intercontinental scale across four adaptive radiations of the three-spined stickleback (Gasterosteus aculeatus), by associating genome-wide allele frequencies with continuous distributions of environmental and phenotypic variation. We found that genomic parallelism was well predicted by parallelism of phenotype-environment associations, suggesting that a quantitative characterization of phenotypes and environments can provide a good prediction of expected genomic parallelism. Further, we examined the explanatory power of genetic, phenotypic, and environmental similarity in predicting parallelism. We found that parallelism tended to be greater for geographically proximate, genetically similar radiations, highlighting the significant contingency of standing variation in the early stages of adaptive radiations, before new mutations accumulate. However, we also demonstrate that distance within multivariate environmental space predicts parallelism, after correction for genetic distance. This study thus demonstrates the relative influences of environment, phenotype and genetic contingency on repeatable signatures of adaptation in the genome.

evolutionary biology↗