Current steering and electrode spanning with partial tripolar stimulation mode in cochlear implants

Cochlear implants (CIs) partially restore hearing sensation to profoundly deaf people by electrically stimulating the surviving auditory neurons. However, CI users perform poorly in challenging listening tasks such as speech recognition in noise and Cochlear implants (CIs) partially restore hearing sensation to profoundly deaf people by electrically stimulating the surviving auditory neurons. However, CI users perform poorly in challenging listening tasks such as speech recognition in noise and music perception, possibly due to the small number of implanted electrodes and the large current spread of electric stimulation. Although current spread may be reduced using partial tripolar (pTP) stimulation mode, the number of electrodes may not be sufficient to preserve fine spectral details. Here, we propose to introduce current steering and electrode spanning to pTP mode to create additional spectral channels for CI users. Loudness and pitch perception with steered and spanned pTP modes were simulated using a computational model of CI stimulation and were tested in CI users. The excitation pattern of each stimulation mode was also measured at the physical (i.e., intra-cochlear electrical potential distribution), neural (i.e., spatial profile of evoked compound action potential), and perceptual levels (i.e., psychophysical forward masking pattern). Consistent with the model predictions, pitch-ranking results verified the feasibility and efficacy of the proposed stimulation modes in eliciting distinctive pitches for CI users. Pitch increased when the centroid of excitation pattern was shifted basally. When the centroid of excitation pattern did not move, higher pitches were perceived for narrower excitation patterns. These results suggest that in pTP-mode CI processing strategies, current steering and electrode spanning may provide additional spectral channels for better coding of spectral fine structures and for handling the cochlear dead region and defective electrode contact

Explaining the PENTA model: a reply to Arvaniti and Ladd

This paper presents an overview of the Parallel Encoding and Target Approximation (PENTA) model of speech prosody, in response to an extensive critique by Arvaniti & Ladd (2009). PENTA is a framework for conceptually and computationally linking communicative meanings to fine-grained prosodic details, based on an articulatory-functional view of speech. Target Approximation simulates the articulatory realisation of underlying pitch targets – the prosodic primitives in the framework. Parallel Encoding provides an operational scheme that enables simultaneous encoding of multiple communicative functions. We also outline how PENTA can be computationally tested with a set of software tools. With the help of one of the tools, we offer a PENTA-based hypothetical account of the Greek intonational patterns reported by Arvaniti & Ladd, showing how it is possible to predict the prosodic shapes of an utterance based on the lexical and postlexical meanings it conveys

Investigating Fine Temporal Dynamics of Prosodic and Lexical Accommodation

Conversational interaction is a dynamic activity in which participants engage in the construction of meaning and in establishing and maintaining social relationships. Lexical and prosodic accommodation have been observed in many studies as contributing importantly to these dimensions of social interaction. However, while previous works have considered accommodation mechanisms at global levels (for whole conversations, halves and thirds of conversations), this work investigates their evolution through repeated analysis at time intervals of increasing granularity to analyze the dynamics of alignment in a spoken language corpus. Results show that the levels of both prosodic and lexical accommodation fluctuate several times over the course of a conversation