Perception and neural coding of harmonic fusion in ferrets

The cortical neural correlates for the perception of harmonic sounds have remained a puzzle despite intense study over several decades. This study approached the problem from the point of view of the spectral fusion evoked by such sounds. Experiment 1 tested whether ferrets automatically fuse harmonic complex tones. In baseline sessions, three ferrets were trained to detect a pure tone terminating a sequence of inharmonic complex tones. After the ferrets reached proficiency in the baseline task, a small fraction of the inharmonic complex tones were replaced with harmonic tones. Two out of three ferrets confused the harmonic complex tones with the pure tones and responded as if detecting the pure tone at twice the false-alarm rate, indicating that ferrets can automatically fuse the partials of a harmonic complex. Experiment 2 sought correlates of harmonic fusion in single units of ferret primary auditory cortex (AI), by contrasting responses to harmonic complex tones with those to inharmonic complex tones. The effects of spectrotemporal filtering were accounted for by using the measured spectrotemporal receptive field to predict responses and by seeking correlates of harmonic fusion in the predictability of the responses. Ten percent of units exhibited some correlates of harmonic fusion, which is consistent with previous findings that no special processing for harmonic stimuli occurs in AI

Fast and Slow Effects of Medial Olivocochlear Efferent Activity in Humans

Background: The medial olivocochlear (MOC) pathway modulates basilar membrane motion and auditory nerve activity on both a fast (10–100 ms) and a slow (10–100 s) time scale in guinea pigs. The slow MOC modulation of cochlear activity is postulated to aide in protection against acoustic trauma. However in humans, the existence and functional roles of slow MOC effects remain unexplored. Methodology/Principal Findings: By employing contralateral noise at moderate to high levels (68 and 83 dB SPL) as an MOC reflex elicitor, and spontaneous otoacoustic emissions (SOAEs) as a non-invasive probe of the cochlea, we demonstrated MOC modulation of human cochlear output both on a fast and a slow time scale, analogous to the fast and slow MOC efferent effects observed on basilar membrane vibration and auditory nerve activity in guinea pigs. The magnitude of slow effects was minimal compared with that of fast effects. Consistent with basilar membrane and auditory nerve activity data, SOAE level was reduced by both fast and slow MOC effects, whereas SOAE frequency was elevated by fast and reduced by slow MOC effects. The magnitudes of fast and slow effects on SOAE level were positively correlated. Conclusions/Significance: Contralateral noise up to 83 dB SPL elicited minimal yet significant changes in both SOAE leve

Signal Transmission in the Auditory System

Contains table of contents for Section 3 and reports on four research projects.National Institutes of Health Grant R01 DC00194National Institutes of Health Grant P01 DC00119National Science Foundation Grant IBN 96-04642W.M. Keck Foundation Career Development ProfessorshipNational Institutes of Health Grant R01 DC00238Thomas and Gerd Perkins Award ProfessorshipAlfred P Sloan Foundation Instrumentation GrantJohn F. and Virginia B. Taplin Award in Health Sciences and TechnologyNational Institutes of Health/National Institute of Deafness and Other Communication DisordersNational Institutes of Health/National Institute of Deafness and Other Communication Disorders Grant PO1 DC0011

Systems-Level Modeling of Cancer-Fibroblast Interaction

Cancer cells interact with surrounding stromal fibroblasts during tumorigenesis, but the complex molecular rules that govern these interactions remain poorly understood thus hindering the development of therapeutic strategies to target cancer stroma. We have taken a mathematical approach to begin defining these rules by performing the first large-scale quantitative analysis of fibroblast effects on cancer cell proliferation across more than four hundred heterotypic cell line pairings. Systems-level modeling of this complex dataset using singular value decomposition revealed that normal tissue fibroblasts variably express at least two functionally distinct activities, one which reflects transcriptional programs associated with activated mesenchymal cells, that act either coordinately or at cross-purposes to modulate cancer cell proliferation. These findings suggest that quantitative approaches may prove useful for identifying organizational principles that govern complex heterotypic cell-cell interactions in cancer and other contexts

Signal Transmission in the Auditory System

Contains table of contents for Section 3, an introduction and reports on five research projects.National Institutes of Health Grant R01-DC-00194National Institutes of Health Grant P01-DC-00119Charles S. Draper Laboratory Contract DL-H-496015National Institutes of Health Grant R01 DC00238National Institutes of Health Grant R01-DC02258National Institutes of Health Grant T32-DC00038National Institutes of Health Grant RO1 DC00235National Institutes of Health Grant P01-DC00361National Institutes of Health Contract N01-DC-6-210

Signal Transmission in the Auditory System

Contains table of contents for Section 3, an introduction and reports on seven research projects.National Institutes of Health Grant P01-DC-00119National Institutes of Health Grant R01-DC-00194National Institutes of Health Grant R01 DC00238National Institutes of Health Grant R01-DC02258National Institutes of Health Grant T32-DC00038National Institutes of Health Grant P01-DC00361National Institutes of Health Grant 2RO1 DC00235National Institutes of Health Contract N01-DC2240

Hearing technology and cognition,”

Purpose: To summarize existing data on the interactions of cognitive function and hearing technology in older adults. Method: A narrative review was used to summarize previous data for the short-term interactions of cognition and hearing technology on measured outcomes. For long-term outcomes, typically for 3-24 months of hearing aid use, a computerized database search was conducted. Results: There is accumulating evidence that cognitive function can impact outcomes following immediate or shortterm use of hearing aids and that hearing aids can impact immediate cognitive function. There is limited evidence regarding the long-term impact of hearing aids on cognition, and the most rigorous studies in this area have not observed a positive effect. Conclusions: Although interactions have been observed between cognition and use of hearing aids for measures obtained following immediate or short-term usage of hearing technology, limited evidence is available following long-term usage, and that evidence that is available does not support an effect of hearing aids on cognitive function. More research is needed, however, including rigorous studies of older adults following longer periods of hearing aid usage