Perception of Urgency and Spatialization of Auditory Alarms

Presented at the 13th International Conference on Auditory Display (ICAD2007) June 26-29, 2007 in Montréal, Canada.Alarms can be spatialized in new human-machine interfaces. This includes the perception of distance at different points in space. The aim of this work was to study the interferences between the perception of distance and the perception of urgency. Two experiments used common stimuli. These were sounds recorded on a dummy head from a white noise emitted from 8 directions in the azimuth plane and at 3 distances, inside a closed, empty room. The sounds were then loudness equalized. Experiment 1 consisted of presenting the sounds in pairs to the listeners, who had to designate the sound which was perceived as the most urgent. The results show that, for the same distance, the level of urgency is greater when the virtual source is at $\pm$90$\,^{\circ}$. They also show two types of responses concerning the links between the perception of distance and urgency. Certain listeners perceive near sounds as the most urgent, while others perceive distant sounds as the most urgent. Experiment 2 is a control experiment to check that perception of distance is preserved for these loudness equalized sounds

Differential Impact of Brain Network Efficiency on Poststroke Motor and Attentional Deficits

Background:Most studies on stroke have been designed to examine one deficit in isolation; yet, survivors often have multiple deficits in different domains. While the mechanisms underlying multiple-domain deficits remain poorly understood, network-theoretical methods may open new avenues of understanding. Methods:Fifty subacute stroke patients (7 +/- 3days poststroke) underwent diffusion-weighted magnetic resonance imaging and a battery of clinical tests of motor and cognitive functions. We defined indices of impairment in strength, dexterity, and attention. We also computed imaging-based probabilistic tractography and whole-brain connectomes. To efficiently integrate inputs from different sources, brain networks rely on a rich-club of a few hub nodes. Lesions harm efficiency, particularly when they target the rich-club. Overlaying individual lesion masks onto the tractograms enabled us to split the connectomes into their affected and unaffected parts and associate them to impairment. Results:We computed efficiency of the unaffected connectome and found it was more strongly correlated to impairment in strength, dexterity, and attention than efficiency of the total connectome. The magnitude of the correlation between efficiency and impairment followed the order attention>dexterity approximate to strength (strength: |r|=.03, P=0.02, dexterity: |r|=.30, P=0.05, attention: |r|=.55, P<0.001). Network weights associated with the rich-club were more strongly correlated to efficiency than non-rich-club weights. Conclusions:Attentional impairment is more sensitive to disruption of coordinated networks between brain regions than motor impairment, which is sensitive to disruption of localized networks. Providing more accurate reflections of actually functioning parts of the network enables the incorporation of information about the impact of brain lesions on connectomics contributing to a better understanding of underlying stroke mechanisms.MIPLA

Type II spiral ganglion afferent neurons drive medial olivocochlear reflex suppression of the cochlear amplifier

The dynamic adjustment of hearing sensitivity and frequency selectivity is mediated by the medial olivocochlear efferent reflex, which suppresses the gain of the ‘cochlear amplifier' in each ear. Such efferent feedback is important for promoting discrimination of sounds in background noise, sound localization and protecting the cochleae from acoustic overstimulation. However, the sensory driver for the olivocochlear reflex is unknown. Here, we resolve this longstanding question using a mouse model null for the gene encoding the type III intermediate filament peripherin (Prph). Prph((−/−)) mice lacked type II spiral ganglion neuron innervation of the outer hair cells, whereas innervation of the inner hair cells by type I spiral ganglion neurons was normal. Compared with Prph((+/+)) controls, both contralateral and ipsilateral olivocochlear efferent-mediated suppression of the cochlear amplifier were absent in Prph((−/−)) mice, demonstrating that outer hair cells and their type II afferents constitute the sensory drive for the olivocochlear efferent reflex