Auditory Neuroscience

Atoh1 expression and function during auditory hair cell regeneration in post-hatch chickens

by Rebecca Lewis

Loss of hair cells in humans leads to irreversible hearing deficits, since auditory hair cells are not replaced. In... more Loss of hair cells in humans leads to irreversible hearing deficits, since auditory hair cells are not replaced. In contrast, hair cells are regenerated in the auditory epithelium of mature birds after damage by non-sensory supporting cells that transdifferentiate into hair cells by mitotic and/or non-mitotic mechanisms. Factors controlling these processes are poorly understood. The basic helix-loop-helix transcription factor ATOH1 is both necessary and sufficient for developmental hair cell differentiation, but it is unclear if it plays the same role in the mitotic and non-mitotic pathways in hair cell regeneration. We examined Atoh1 expression and function during hair cell regeneration in chickens. Atoh1 transcripts were increased in many supporting cells in the damaged auditory epithelium shortly after ototoxin administration and later became restricted to differentiating hair cells. Fate-mapping in vitro using an Atoh1 enhancer reporter demonstrated that only 56% of the supporting cells that spontaneously upregulate Atoh1 enhancer activity after damage acquired the hair cell fate. Inhibition of notch signaling using a gamma secretase antagonist stimulated an increase in Atoh1 reporter activity and induced a higher proportion of supporting cells with Atoh1 activity (73%) to differentiate as hair cells. Forced overexpression of Atoh1 in supporting cells triggered 66% of them to acquire the hair cell fate and nearly tripled their likelihood of cell cycle entry. These findings demonstrate that Atoh1 is broadly upregulated in supporting cells after damage, but a substantial proportion of supporting cells with Atoh1 activation fails to acquire hair cell features, in part due to gamma secretase-dependent activities.

dyslexia theoretical background

by okan karka

When children learn to read and write, they need to learn to transform the squiggles that we call letters intomore When children learn to read and write, they need to learn to transform the squiggles that we call letters into
sounds. The process involved in recognizing visual shapes and symbols and processing this information to
eventually understand the meaning behind the writing is extremely complex

Responsiveness to repeated speech stimuli persists in left but not right auditory cortex

by Peter Soros

Auditory temporal processing in healthy aging: a magnetoencephalographic study

by Peter Soros

BMC Neurosci. 2009 Apr 7;10:34.
Auditory temporal processing in healthy aging: a magnetoencephalographic study.
Sörös P, Teismann IK, Manemann E, Lütkenhöner B.

BACKGROUND:
Impaired speech perception is one of the major sequelae of aging. In addition to peripheral hearing... more BACKGROUND:
Impaired speech perception is one of the major sequelae of aging. In addition to peripheral hearing loss, central deficits of auditory processing are supposed to contribute to the deterioration of speech perception in older individuals. To test the hypothesis that auditory temporal processing is compromised in aging, auditory evoked magnetic fields were recorded during stimulation with sequences of 4 rapidly recurring speech sounds in 28 healthy individuals aged 20 - 78 years.

RESULTS:
The decrement of the N1m amplitude during rapid auditory stimulation was not significantly different between older and younger adults. The amplitudes of the middle-latency P1m wave and of the long-latency N1m, however, were significantly larger in older than in younger participants.

CONCLUSION:
The results of the present study do not provide evidence for the hypothesis that auditory temporal processing, as measured by the decrement (short-term habituation) of the major auditory evoked component, the N1m wave, is impaired in aging. The differences between these magnetoencephalographic findings and previously published behavioral data might be explained by differences in the experimental setting between the present study and previous behavioral studies, in terms of speech rate, attention, and masking noise. Significantly larger amplitudes of the P1m and N1m waves suggest that the cortical processing of individual sounds differs between younger and older individuals. This result adds to the growing evidence that brain functions, such as sensory processing, motor control and cognitive processing, can change during healthy aging, presumably due to experience-dependent neuroplastic mechanisms.

Gamma band pitch reponses in human auditory cortex measured with magnetoencephalography

by Sundeep Teki

Sedley W, Teki S, Kumar S, Overath T, Barnes GR, Griffiths TD (2011). Gamma band pitch reponses in human auditory cortex measured with magnetoencephalography. NeuroImage.

We have previously used direct electrode recordings in two human subjects to identify neural correlates of the... more We have previously used direct electrode recordings in two human subjects to identify neural correlates of the perception of pitch (Griffiths, Kumar, Sedley et al., Direct recordings of pitch responses from human auditory cortex, Curr. Biol. 22 (2010), pp. 1128-1132). The present study was carried out to assess virtual-electrode measures of pitch perception based on non-invasive magnetoencephalography (MEG). We recorded pitch responses in 13 healthy volunteers using a passive listening paradigm and the same pitch-evoking stimuli (regular interval noise; RIN) as in the previous study. Source activity was reconstructed using a beamformer approach, which was used to place virtual electrodes in auditory cortex. Time-frequency decomposition of these data revealed oscillatory responses to pitch in the gamma frequency band to occur, in Heschl's gyrus, from 60Hz upwards. Direct comparison of these pitch responses to the previous depth electrode recordings shows a striking congruence in terms of spectrotemporal profile and anatomical distribution. These findings provide further support that auditory high gamma oscillations occur in association with RIN pitch stimuli, and validate the use of MEG to assess neural correlates of normal and abnormal pitch perception.

Voice Cells in the Primate Temporal Lobe

by Catherine Perrodin

Communication signals are important for social interactions and survival and are thought to receive specialized... more Communication signals are important for social interactions and survival and are thought to receive specialized processing in the visual and auditory systems. Whereas the neural processing of faces by face clusters and face cells has been repeatedly studied, less is known about the neural representation of voice content. Recent functional magnetic resonance imaging (fMRI) studies have localized voice-preferring regions in the primate temporal lobe, but the hemodynamic response cannot directly assess neurophysiological properties. We investigated the responses of neurons in an fMRI-identified voice cluster in awake monkeys, and here we provide the first systematic evidence for voice cells. Voice cells were identified, in analogy to face cells, as neurons responding at least 2-fold stronger to conspecific voices than to nonvoice sounds or heterospecific voices. Importantly, whereas face clusters are thought to contain high proportions of face cells responding broadly to many faces, we found that voice clusters contain moderate proportions of voice cells. Furthermore, individual voice cells exhibit high stimulus selectivity. The results reveal the neurophysiological bases for fMRI-defined voice clusters in the primate brain and highlight potential differences in how the auditory and visual systems generate selective representations of communication signals.

Brain bases for auditory stimulus-driven figure-ground segregation

by Sundeep Teki

Auditory figure-ground segregation, listeners' ability to selectively hear out a sound of interest from a background... more Auditory figure-ground segregation, listeners' ability to selectively hear out a sound of interest from a background of competing sounds, is a fundamental aspect of scene analysis. In contrast to the disordered acoustic environment we experience during everyday listening, most studies of auditory segregation have used relatively simple, temporally regular signals. We developed a new figure-ground stimulus that incorporates stochastic variation of the figure and background that captures the rich spectrotemporal complexity of natural acoustic scenes. Figure and background signals overlap in spectrotemporal space, but vary in the statistics of fluctuation, such that the only way to extract the figure is by integrating the patterns over time and frequency. Our behavioral results demonstrate that human listeners are remarkably sensitive to the appearance of such figures. In a functional magnetic resonance imaging experiment, aimed at investigating preattentive, stimulus-driven, auditory segregation mechanisms, naive subjects listened to these stimuli while performing an irrelevant task. Results demonstrate significant activations in the intraparietal sulcus (IPS) and the superior temporal sulcus related to bottom-up, stimulus-driven figure-ground decomposition. We did not observe any significant activation in the primary auditory cortex. Our results support a role for automatic, bottom-up mechanisms in the IPS in mediating stimulus-driven, auditory figure-ground segregation, which is consistent with accumulating evidence implicating the IPS in structuring sensory input and perceptual organization.

Syntax processing by auditory cortical neurons in the FM–FM area of the mustached bat Pteronotus parnellii

by Jagmeet Kanwal

Compression of auditory space during rapid head turns

by johahn leung

Auditory temporal processing in healthy aging: a

by Peter Soros

BMC Neuroscience 2009;10:34

Background: Impaired speech perception is one of the major sequelae of aging. In addition to  peripheral hearing... more Background: Impaired speech perception is one of the major sequelae of aging. In addition to  peripheral hearing loss, central deficits of auditory processing are supposed to contribute to the  deterioration of speech perception in older individuals. To test the hypothesis that auditory  temporal processing is compromised in aging, auditory evoked magnetic fields were recorded  during stimulation with sequences of 4 rapidly recurring speech sounds in 28 healthy individuals  aged 20 – 78 years. 

Results: The decrement of the N1m amplitude during rapid auditory stimulation was not  significantly different between older and younger adults. The amplitudes of the middle-latency P1m  wave and of the long-latency N1m, however, were significantly larger in older than in younger  participants. 

Conclusion: The results of the present study do not provide evidence for the hypothesis that  auditory temporal processing, as measured by the decrement (short-term habituation) of the major  auditory evoked component, the N1m wave, is impaired in aging. The differences between these  magnetoencephalographic findings and previously published behavioral data might be explained by  differences in the experimental setting between the present study and previous behavioral studies,  in terms of speech rate, attention, and masking noise. Significantly larger amplitudes of the P1m and  N1m waves suggest that the cortical processing of individual sounds differs between younger and  older individuals. This result adds to the growing evidence that brain functions, such as sensory  processing, motor control and cognitive processing, can change during healthy aging, presumably  due to experience-dependent neuroplastic mechanisms. 

The neurochemical basis of human cortical auditory processing: Combining proton magnetic resonance spectroscopy and magnetoencephalography.

by Peter Soros

Sörös P, Michael N, Tollkötter M, Pfleiderer B. BMC Biology 2006;4:25.

BACKGROUND: A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate... more BACKGROUND: A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic stimuli. We tested the hypothesis that: (i) the amplitude of the N1m response and (ii) its decrement during rapid stimulation are associated with the cortical neurochemistry as determined by proton magnetic resonance spectroscopy. RESULTS: Our results demonstrated a significant association between the concentrations of N-acetylaspartate, a marker of neuronal integrity, and the amplitudes of individual N1m responses. In addition, the concentrations of choline-containing compounds, representing the functional integrity of membranes, were significantly associated with N1m amplitudes. No significant association was found between the concentrations of the glutamate/glutamine pool and the amplitudes of the first N1m. No significant associations were seen between the decrement of the N1m (the relative amplitude of the second N1m peak) and the concentrations of N-acetylaspartate, choline-containing compounds, or the glutamate/glutamine pool. However, there was a trend for higher glutamate/glutamine concentrations in individuals with higher relative N1m amplitude. CONCLUSION: These results suggest that neuronal and membrane functions are important for rapid auditory processing. This investigation provides a first link between the electrophysiology, as recorded by magnetoencephalography, and the neurochemistry, as assessed by proton magnetic resonance spectroscopy, of the auditory cortex.

No indication of brain reorganization after unilateral ischemic lesions of the auditory cortex.

by Peter Soros

Sörös P, Dziewas R, Manemann E, Teismann IK, Lütkenhöner B. Neurology 2006;67(1):1059-1061.

We used magnetoencephalography to study contralesional auditory reorganization in three men with chronic unilateral... more We used magnetoencephalography to study contralesional auditory reorganization in three men with chronic unilateral ischemic lesions of the auditory cortex. Although no response was found over the lesioned hemisphere, processing in the unaffected hemisphere was indistinguishable vs healthy controls. In contrast to sensorimotor and language systems, the auditory system seems to lack contralateral reorganization, presumably because patients are typically not aware of hearing deficits and thus do not perform training.