9 research outputs found
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Three-dimensional biomechanical model of benign paroxysmal positional vertigo
Benign Paroxysmal Positional Vertigo (BPPV) is a common disorder of the vestibular labyrinth of the inner ear. The clinical results point toward the possibility of loose basophilic particles (otoconia) free within the labyrinth resulting in the pathology of the condition. When there is a change in head position relative to gravity, the gravito-inertial forces acting on the debris result in the displacement of the fluid (endolymph) within the labyrinth and hence, an excitatory or inhibitory neural response. This is perceived as a false sense of angular head rotation and leads to inappropriate eye movements, dizziness and severe vertigo. The present study describes biomechanical modeling of the condition of BPPV. The particle(s) were modeled as spheres free to move in the membranous labyrinth lumen (canalithiasis) and/or adhered to the cupula (cupulolithiasis). For this, differential equations describing the gravito-inertial forces acting on particle(s) under the two conditions, and the viscous interactions with the endolymph were coupled together and solved within 3D labyrinthine geometry. Results are relevant to the origin, diagnosis and treatment of Benign Paroxysmal Positional Vertigo (BPPV)
Evidence of Piezoelectric Resonance in Isolated Outer Hair Cells
Our results demonstrate high-frequency electrical resonances in outer hair cells (OHCs) exhibiting features analogous to classical piezoelectric transducers. The fundamental (first) resonance frequency averaged f(n) ∼ 13 kHz (Q ∼ 1.7). Higher-order resonances were also observed. To obtain these results, OHCs were positioned in a custom microchamber and subjected to stimulating electric fields along the axis of the cell (1–100 kHz, 4–16 mV/80 μm). Electrodes embedded in the side walls of the microchamber were used in a voltage-divider configuration to estimate the electrical admittance of the top portion of the cell-loaded chamber (containing the electromotile lateral wall) relative to the lower portion (containing the basal plasma membrane). This ratio exhibited resonance-like electrical tuning. Resonance was also detected independently using a secondary 1-MHz radio-frequency interrogation signal applied transversely across the cell diameter. The radio-frequency interrogation revealed changes in the transverse electric impedance modulated by the axial stimulus. Modulation of the transverse electric impedance was particularly pronounced near the resonant frequencies. OHCs used in our study were isolated from the apical region of the guinea pig cochlea, a region that responds exclusively to low-frequency acoustic stimuli. In this sense, electrical resonances we observed in vitro were at least an order of magnitude higher (ultrasonic) than the best physiological frequency of the same OHCs under acoustic stimuli in vivo. These resonance data further support the piezoelectric theory of OHC function, and implicate piezoelectricity in the broad-band electromechanical behavior of OHCs underlying mammalian cochlear function
MRI Integrated with Computational Methods for Determining Internal Soft Tissue Loads as Related to Chronic Wounds
Excessive and prolonged internal soft tissue loads are one of the main factors responsible for the initiation of internal injuries that may, if ignored or untreated, escalate into chronic wounds. Since internal tissue loads cannot be measured in vivo, computational methods that incorporate the actual anatomy of the living body, are currently the best available resource for acquiring internal mechanical knowledge. In this chapter we discuss various methods that use computational modeling integrated with anatomical data, scanned by magnetic resonance imaging (MRI) in order to determine internal soft tissue loads. Specifically we will elaborate on linear and non-linear finite element (FE) methods and hyperelastic warping
Human-Robot Adaptive Control of Object-Oriented Action
International audienceThis chapter is concerned with how implicit, nonverbal cues support coordinated action between two partners. Recently, neuroscientists have started uncovering the brain mechanisms involved in how people make predictions about other people's behavioural goals and intentions through action observation. To date, however, only a small number of studies have addressed how the involvement of a task partner influences the planning and control of one's own purposeful action. Here, we review three studies of cooperative action between human and robot partners that address the nature of predictive and reactive motor control in cooperative action. We conclude with a model which achieves motor coordination by task partners each adjusting their actions on the basis of previous trial outcome