Biology subjects

Flanagin, V. L.

Publications and source records attributed to Flanagin, V. L..

4 recordsLinked to original sources

bioRxiv2024

Neural representation of direct-to-reverberant energy ratio in recorded and simulated binaural room auralizations

In complex acoustic environments, sound localization involves the integration of numerous interrelated auditory and cognitive cues, making it challenging to understand their relationship to brain activity. Here, we use virtual acoustics to probe the brains response to auditory distance cues in a realistic environment. We developed a system to record the actual MRI environment, simulated the same room with different degrees of accuracy, then presented sounds at one of two locations in the room. We implemented a novel auditory fMRI sequence to record brain activity. Despite only minor differences in acoustics between the auralizations, it was possible to decode all three rooms from brain activity. A systematic analysis revealed that the direct-to-reverberant energy ratio (DRR) drove brain activity differences between auralizations, centered on the posterior auditory cortex (AC). The results provide strong evidence that the posterior AC processes DRR for spatial auditory perception. Impact statementA novel fMRI sequence and recording technique are combined with virtual acoustics and multi-variate analyses to decode room simulations from brain activity during distance perception and identify the auditory factors that drive the pattern of activity in the brain.

neuroscience↗

bioRxiv2022

Persistent horizontal and vertical, MR-induced nystagmus in resting state Human Connectome Project data

ObjectiveStrong magnetic fields from magnetic resonance (MR) scanners induce a Lorentz force that contributes to vertigo and persistent nystagmus. Prior studies have reported a predominantly horizontal direction for healthy subjects in a 7 Tesla (T) MR scanner, with slow phase velocity (SPV) dependent on head orientation. Less is known about vestibular signal behavior for subjects in a weaker, 3T magnetic field, the standard strength used in the Human Connectome Project (HCP). The purpose of this study is to characterize the form and magnitude of nystagmus induced at 3T. MethodsForty-two subjects were studied after being introduced head-first, supine into a Siemens Prisma 3T scanner. Eye movements were recorded in four separate acquisitions over 20 minutes. A biometric eye model was fit to the recordings to derive rotational eye position and then SPV. An anatomical template of the semi-circular canals was fit to the T2 anatomical image from each subject, and used to derive the angle of the B0 magnetic field with respect to the vestibular apparatus. ResultsRecordings from 37 subjects yielded valid measures of eye movements. The population-mean SPV {+/-} SD for the horizontal component was -1.38 {+/-} 1.27 deg/sec, and vertical component was -0.93 {+/-} 1.44 deg/sec, corresponding to drift movement in the rightward and downward direction. Although there was substantial inter-subject variability, persistent nystagmus was present in half of subjects with no significant adaptation over the 20 minute scanning period. The amplitude of vertical drift was correlated with the roll angle of the vestibular system, with a non-zero vertical SPV present at a 0 degree roll. InterpretationNon-habituating vestibular signals of varying amplitude are present in resting state data collected at 3T.

neuroscience↗

bioRxiv2020

Distributed coding of stimulus magnitude across the rodent prefrontal cortex

As we interact with the external world, we judge magnitudes from sensory information. The estimation of magnitudes has been characterized in primates, yet it is largely unexplored in non-primate species. Here, we show that gerbils that solve a time-interval reproduction task display primate-like magnitude estimation characteristics, most prominently a systematic overestimation of small stimuli and an underestimation of large stimuli, often referred to as regression effect. We investigated the underlying neural mechanisms by recording from medial prefrontal cortex and show that the majority of neurons respond either during the measurement or the reproduction of a time-interval. Cells that are active during both phases display distinct response patterns. We categorize the neural responses into multiple types and demonstrate that only populations with mixed responses can encode the bias of the regression effect. These results reveal the organizing neural principles of magnitude estimation a process important to higher cognitive functions.

neuroscience↗

bioRxiv2018

Who gets lost and why: A representative cross-sectional survey on sociodemographic and vestibular determinants of wayfinding strategies

When we think of our family and friends, we probably know someone who is good at finding their way and someone else that easily get lost. We still know little about the biological and environmental factors that influence our navigational ability. Here, we investigated the frequency and sociodemographic determinants of wayfinding and their association with vestibular function in a representative cross-sectional sample (N = 783) of the adult German-speaking population. Wayfinding was assessed using the Wayfinding Strategy Scale, a self-report scale that produces two scores for each participant representing to what degree they rely on route-based or orientation (map-based) strategies. We were interested in the following research questions: (1) the frequency and determinants of wayfinding strategies in a population-based representative sample, (2) the relationship between vestibular function and strategy choice and (3) how sociodemographic factors influence general wayfinding ability as measured using a combined score from both strategy scores. Our linear regression models showed that being male, having a higher education, higher age and lower regional urbanization increased orientation strategy scores. Vertigo/dizziness reduced the scores of both the orientation and the route strategies. Using a novel approach, we grouped participants by their combined strategy scores in a multinomial regression model, to see whether individuals prefer one strategy over the other. The majority of individuals reported using either both or no strategy, instead of preferring one strategy over the other. Young age and reduced vestibular function were indicative of using no strategy. In summary, wayfinding ability depends on both biological and environmental factors; all sociodemographic factors except income. Over a third of the population, predominantly under the age of 35, does not successfully use either strategy. This represents a change in our wayfinding skills, which may result from the technological advances in navigational aids over the last few decades.

neuroscience↗