Adaptation of spatio-temporal convergent properties in central vestibular neurons in monkeys

Abstract

The spatio‐temporal convergent (STC) response occurs in central vestibular cells when dynamic and static inputs are activated. The functional significance of STC behavior is not fully understood. Whether STC is a property of some specific central vestibular neurons, or whether it is a response that can be induced in any neuron at some frequencies is unknown. It is also unknown how the change in orientation of otolith polarization vector (orientation adaptation) affects STC behavior. A new complex model, that includes inputs with regular and irregular discharges from both canal and otolith afferents, was applied to experimental data to determine how many convergent inputs are sufficient to explain the STC behavior as a function of frequency and orientation adaptation. The canal–otolith and otolith‐only neurons were recorded in the vestibular nuclei of three monkeys. About 42% (11/26 canal–otolith and 3/7 otolith‐only) neurons showed typical STC responses at least at one frequency before orientation adaptation. After orientation adaptation in side‐down head position for 2 h, some canal–otolith and otolith‐only neurons altered their STC responses. Thus, STC is a property of weights of the regular and irregular vestibular afferent inputs to central vestibular neurons which appear and/or disappear based on stimulus frequency and orientation adaptation. This indicates that STC properties are more common for central vestibular neurons than previously assumed. While gravity‐dependent adaptation is also critically dependent on stimulus frequency and orientation adaptation, we propose that STC behavior is also linked to the neural network responsible for localized contextual learning during gravity‐dependent adaptation.

Treatment of Gravitational Pulling Sensation in Patients With Mal de Debarquement Syndrome (MdDS): A Model-Based Approach

“…We recently demonstrated that cross-coupling from horizontal to vertical and roll components of VOR were also coded by canal-otolith convergent VO neurons ( Yakushin et al, 2017 ). Polarization vectors of VO neurons are flexible and tend to align their orientation with gravity ( Eron et al, 2008a , 2018 ), even when animals were in complete darkness without any specific training stimulus. This is distinct from polarization vectors coded by Eye-Head-Velocity (EHV) and Position-Vestibular-Pause (PVP) neurons that project to oculomotor neurons and therefore are part of the direct VOR pathway ( Kolesnikova et al, 2011 ).…”