Decoding neural responses to temporal cues for sound localization

The activity of sensory neural populations carries information about the environment. This may be extracted from neural activity using different strategies. In the auditory brainstem, a recent theory proposes that sound location in the horizontal plane is decoded from the relative summed activity of two populations in each hemisphere, whereas earlier theories hypothesized that the location was decoded from the identity of the most active cells. We tested the performance of various decoders of neural responses in increasingly complex acoustical situations, including spectrum variations, noise, and sound diffraction. We demonstrate that there is insufficient information in the pooled activity of each hemisphere to estimate sound direction in a reliable way consistent with behavior, whereas robust estimates can be obtained from neural activity by taking into account the heterogeneous tuning of cells. These estimates can still be obtained when only contralateral neural responses are used, consistently with unilateral lesion studies. DOI: http://dx.doi.org/10.7554/eLife.01312.001

The scale of sense : spatial extent and multimodal urban design

This paper is derived from the work of the UK AHRC/EPSRC 'Designing for the 21st Century' research project Multimodal Representation of Urban Space. This research group seeks to establish a new form of notation for urban design which pays attention to our entire sensory experience of place. This paper addresses one of the most important aspects of this endeavour: scale. Scale is of course a familiar abstraction to all architects and urban designers, allowing for representations tailored to different levels of detail and allowing drawings to be translated into build structures. Scale is also a factor in human experience: the spatial extent of each of our senses is different. Many forms of architectonic representation are founded upon the extension of the visual modality, and designs are accordingly tuned towards this sense. We can all speak from our own experience, however, that urban environments are a feast for all the senses. The visceral quality of walking down a wide tree-lined boulevard differs greatly from the subterranean crowds of the subway, or the meandering pause invited by the city square. Similarly, our experience of hearing and listening is more than just a passive observation by virtue of our own power of voice and the feedback created by our percussive movements across a surface or through a medium. Taste and smell are also excited by the urban environment, the social importance of food preparation and the associations between smell and public health are issues of sensory experience. The tactile experience of space, felt with the entire body as well as our more sensitive hands, allowing for direct manipulation and interactions as well as sensations of mass, heat, proximity and texture. Our project team shall present a series of tools for designers which explore the variety of sensory modalities and their associated scales. This suite of notations and analytical frameworks turn our attention to the sensory experience of places, and offers a method and pattern book for more holistic multi-sensory and multi-modal urban design

Neuro-electronic technology in medicine and beyond

This dissertation looks at the technology and social issues involved with interfacing electronics directly to the human nervous system, in particular the methods for both reading and stimulating nerves. The development and use of cochlea implants is discussed, and is compared with recent developments in artificial vision. The final sections consider a future for non-medicinal applications of neuro-electronic technology. Social attitudes towards use for both medicinal and non-medicinal purposes are discussed, and the viability of use in the latter case assessed

Individual differences in auditory brainstem response wave characteristics : relations to different aspects of peripheral hearing loss

Little is known about how outer hair cell loss interacts with noise-induced and age-related auditory nerve degradation (i.e., cochlear synaptopathy) to affect auditory brainstem response (ABR) wave characteristics. Given that listeners with impaired audiograms likely suffer from mixtures of these hearing deficits and that ABR amplitudes have successfully been used to isolate synaptopathy in listeners with normal audiograms, an improved understanding of how different hearing pathologies affect the ABR source generators will improve their sensitivity in hearing diagnostics. We employed a functional model for human ABRs in which different combinations of hearing deficits were simulated and show that highfrequency cochlear gain loss steepens the slope of the ABRWave-V latency versus intensity and amplitude versus intensity curves. We propose that grouping listeners according to a ratio of these slope metrics (i.e., the ABR growth ratio) might offer a way to factor out the outer hair cell loss deficit and maximally relate individual differences for constant ratios to other peripheral hearing deficits such as cochlear synaptopathy. We compared the model predictions to recorded click-ABRs from 30 participants with normal or high-frequency sloping audiograms and confirm the predicted relationship between the ABR latency growth curve and audiogram slope. Experimental ABR amplitude growth showed large individual differences and was compared with the Wave-I amplitude, Wave-V/I ratio, or the interwaveI-W latency in the same listeners. The model simulations along with the ABR recordings suggest that a hearing loss profile depicting the ABR growth ratio versus the Wave-I amplitude or Wave-V/I ratio might be able to differentiate outer hair cell deficits from cochlear synaptopathy in listeners with mixed pathologies

Children with unilateral aural atresia

The effects of FM system fitted into the normal hearing ear (NHE) or a cartilage conduction hearing aid (CCHA) fitted into the affected ear (AE) on the speech recognition ability in noise were examined in children with unilateral congenital aural atresia (UCAA). In children with bilateral normal hearing (BNH), speech recognition score (SRS) was significantly decreased in the noisy environment of -5 dB signal-to-noise ratio (SNR), compared with those in quiet. In children with UCAA, SRS was significantly decreased in noisy environments of 0 and -5 dB SNR, compared with those in quiet. In noisy environments of 0 and -5 dB SNR, SRS in children with UCAA was significantly decreased, compared those in children with BNH. In the noisy environment of -5 dB SNR, SRS in UCAA children aided by FM system fitted into NHE was significantly better than those in unaided children in the same group. In the noisy environment of 0 dB SNR, SRS in UCAA children aided by CCHA into AE tended to be higher than those in unaided children in the same group. FM system and CCHA can be recommended as an audiological management for the improvement of speech recognition in children with UCHL in classrooms

Understanding cochlear implants: a guide for parents and educators

This paper discusses the development of a guidebook for parents and teachers of children with cochlear implants