Biology subjects

Koun, E.

Publications and source records attributed to Koun, E..

3 recordsLinked to original sources

bioRxiv2020

Atomoxetine modulates the contribution of high- and low-level signals during free viewing of natural images in rhesus monkeys

Visuo-spatial attentional orienting is fundamental to selectively process behaviorally relevant information, depending on both low-level visual attributes of stimuli in the environment and higher-level factors, such as goals, expectations and prior knowledge. Growing evidence suggests an impact of the locus-coeruleus-norepinephrine (LC-NE) system in attentional orienting that depends on task-context. Nonetheless, most of previous studies used visual displays encompassing a target and various distractors, often preceded by cues to orient the attentional focus. This emphasizes the contribution of goal-driven processes, at the expense of other factors related to the stimulus content. Here, we aimed to determine the impact of NE on attentional orienting in more naturalistic conditions, using complex images and without any explicit task manipulation. We tested the effects of atomoxetine (ATX) injections, a NE reuptake inhibitor, on four monkeys during free viewing of images belonging to three categories: landscapes, monkey faces and scrambled images. Analyses of the gaze exploration patterns revealed, first, that the monkeys spent more time on each fixation under ATX compared to the control condition, regardless of the image content. Second, we found that, depending on the image content, ATX modulated the impact of low-level visual salience on attentional orienting. This effect correlated with the effect of ATX on the number and duration of fixations. Taken together, our results demonstrate that ATX adjusts the contribution of salience on attentional orienting depending on the image content, indicative of its role in balancing the role of stimulus-driven and top-down control during free viewing of complex stimuli.

neuroscience↗

bioRxiv2020

Patterns of multisensory facilitation distinguish peripersonal from reaching space

Peripersonal space (PPS) is a multisensory representation of the space near body parts facilitating interactions with the close environment. Studies on non-human and human primates converge in showing that PPS is a body-part-centred representation that guides actions. Because of these characteristics, growing confusion conflates peripersonal and arm-reaching space (ARS), that is the space ones arm can reach. Despite neuroanatomical evidence favors their distinction, no study has contrasted directly their respective extent and behavioral features. Here, in five experiments (N=140) we found that PPS differs from ARS, as evidenced both by participants spatial and temporal performance and its modeling. We mapped PPS and ARS using both their respective gold standard tasks and a novel multisensory facilitation paradigm. Results show that 1) PPS is smaller than ARS; 2) multivariate analyses of spatial patterns of multisensory facilitation predict participants hand locations within ARS; 3) the multisensory facilitation map shifts isomorphically following hand positions, revealing hand-centred coding of PPS, therefore pointing to a functional similarity to the receptive fields of monkeys multisensory neurons. A control experiment further corroborated these results and additionally ruled out the orienting of attention as driving mechanism for the increased multisensory facilitation near the hand. In sharp contrast, ARS mapping results in a larger spatial extent, with undistinguishable patterns across hand positions, cross-validating the conclusion that PPS and ARS are distinct spatial representations. These findings urge for a refinement of theoretical models of PPS, which is relevant to constructs as diverse as self-representation, social interpersonal distance, and motor control.

neuroscience↗

bioRxiv2020

SPHERE: A novel approach to 3D and active sound localization

In everyday life, localizing a sound source in free-field entails more than the sole extraction of monaural and binaural auditory cues to define its location in the three-dimensions (azimuth, elevation and distance). In spatial hearing, we also take into account all the available visual information (e.g., cues to sound position, cues to the structure of the environment), and we resolve perceptual ambiguities through active listening behavior, exploring the auditory environment with head or/and body movements. Here we introduce a novel approach to sound localization in 3D named SPHERE (European patent n{degrees} WO2017203028A1), which exploits a commercially available Virtual Reality Head-mounted display system with real-time kinematic tracking to combine all of these elements (controlled positioning of a real sound source and recording of participants responses in 3D, controlled visual stimulations and active listening behavior). We prove that SPHERE allows accurate sampling of the 3D spatial hearing abilities of normal hearing adults, and it allowed detecting and quantifying the contribution of active listening. Specifically, comparing static vs. free head-motion during sound emission we found an improvement of sound localization accuracy and precisions. By combining visual virtual reality, real-time kinematic tracking and real-sound delivery we have achieved a novel approach to the study of spatial hearing, with the potentials to capture real-life behaviors in laboratory conditions. Furthermore, our new approach also paves the way for clinical and industrial applications that will leverage the full potentials of active listening and multisensory stimulation intrinsic to the SPHERE approach for the purpose rehabilitation and product assessment.

neuroscience↗