scholarly journals Ability of primary auditory cortical neurons to detect amplitude modulation with rate and temporal codes: neurometric analysis

2012 ◽  
Vol 107 (12) ◽  
pp. 3325-3341 ◽  
Author(s):  
Jeffrey S. Johnson ◽  
Pingbo Yin ◽  
Kevin N. O'Connor ◽  
Mitchell L. Sutter
Keyword(s):  
Amplitude Modulation ◽  
Cortical Neurons ◽  
Modulation Depth ◽  
Modulation Frequency ◽  
Primary Auditory Cortex ◽  
Detection Methods ◽  
Lower Envelope ◽  
Detection Thresholds ◽  
Modulation Detection ◽  
Temporal Measures

Amplitude modulation (AM) is a common feature of natural sounds, and its detection is biologically important. Even though most sounds are not fully modulated, the majority of physiological studies have focused on fully modulated (100% modulation depth) sounds. We presented AM noise at a range of modulation depths to awake macaque monkeys while recording from neurons in primary auditory cortex (A1). The ability of neurons to detect partial AM with rate and temporal codes was assessed with signal detection methods. On average, single-cell synchrony was as or more sensitive than spike count in modulation detection. Cells are less sensitive to modulation depth if tested away from their best modulation frequency, particularly for temporal measures. Mean neural modulation detection thresholds in A1 are not as sensitive as behavioral thresholds, but with phase locking the most sensitive neurons are more sensitive, suggesting that for temporal measures the lower-envelope principle cannot account for thresholds. Three methods of preanalysis pooling of spike trains (multiunit, similar to convergence from a cortical column; within cell, similar to convergence of cells with matched response properties; across cell, similar to indiscriminate convergence of cells) all result in an increase in neural sensitivity to modulation depth for both temporal and rate codes. For the across-cell method, pooling of a few dozen cells can result in detection thresholds that approximate those of the behaving animal. With synchrony measures, indiscriminate pooling results in sensitive detection of modulation frequencies between 20 and 60 Hz, suggesting that differences in AM response phase are minor in A1.

scholarly journals Auditory Cortex Phase Locking to Amplitude-Modulated Cochlear Implant Pulse Trains

2008 ◽  
Vol 100 (1) ◽  
pp. 76-91 ◽  
Author(s):  
John C. Middlebrooks
Keyword(s):  
Auditory Cortex ◽  
Cochlear Implant ◽  
Amplitude Modulation ◽  
Cortical Neurons ◽  
Modulation Depth ◽  
Phase Locking ◽  
Modulation Frequency ◽  
Electrical Pulse ◽  
Electrode Arrays ◽  
Pulse Trains

Cochlear implant speech processors transmit temporal features of sound as amplitude modulation of constant-rate electrical pulse trains. This study evaluated the central representation of amplitude modulation in the form of phase-locked firing of neurons in the auditory cortex. Anesthetized pigmented guinea pigs were implanted with cochlear electrode arrays. Stimuli were 254 pulse/s (pps) trains of biphasic electrical pulses, sinusoidally modulated with frequencies of 10–64 Hz and modulation depths of −40 to −5 dB re 100% (i.e., 1–56.2% modulation). Single- and multiunit activity was recorded from multi-site silicon-substrate probes. The maximum frequency for significant phase locking (limiting modulation frequency) was ≥60 Hz for 42% of recording sites, whereas phase locking to pulses of unmodulated pulse trains rarely exceeded 30 pps. The strength of phase locking to frequencies ≥40 Hz often varied nonmonotonically with modulation depth, commonly peaking at modulation depths around −15 to −10 dB. Cortical phase locking coded modulation frequency reliably, whereas a putative rate code for frequency was confounded by rate changes with modulation depth. Group delay computed from the slope of mean phase versus modulation frequency tended to increase with decreasing limiting modulation frequency. Neurons in cortical extragranular layers had lower limiting modulation frequencies than did neurons in thalamic afferent layers. Those observations suggest that the low-pass characteristic of cortical phase locking results from intracortical filtering mechanisms. The results show that cortical neurons can phase lock to modulated electrical pulse trains across the range of modulation frequencies and depths presented by cochlear implant speech processors.

scholarly journals How Do Age and Hearing Loss Impact Spectral Envelope Perception?

2018 ◽  
Vol 61 (9) ◽  
pp. 2376-2385 ◽  
Author(s):  
Erol J. Ozmeral ◽  
Ann C. Eddins ◽  
David A. Eddins
Keyword(s):  
Hearing Loss ◽  
Spectral Resolution ◽  
Modulation Frequency ◽  
Normal Hearing ◽  
Frequency Resolution ◽  
Spectral Envelope ◽  
Detection Thresholds ◽  
Spectral Modulation ◽  
Modulation Detection ◽  
Moderate Hearing Loss

Purpose The goal was to evaluate the potential effects of increasing hearing loss and advancing age on spectral envelope perception. Method Spectral modulation detection was measured as a function of spectral modulation frequency from 0.5 to 8.0 cycles/octave. The spectral modulation task involved discrimination of a noise carrier (3 octaves wide from 400 to 3200 Hz) with a flat spectral envelope from a noise having a sinusoidal spectral envelope across a logarithmic audio frequency scale. Spectral modulation transfer functions (SMTFs; modulation threshold vs. modulation frequency) were computed and compared 4 listener groups: young normal hearing, older normal hearing, older with mild hearing loss, and older with moderate hearing loss. Estimates of the internal spectral contrast were obtained by computing excitation patterns. Results SMTFs for young listeners with normal hearing were bandpass with a minimum modulation detection threshold at 2 cycles/octave, and older listeners with normal hearing were remarkably similar to those of the young listeners. SMTFs for older listeners with mild and moderate hearing loss had a low-pass rather than a bandpass shape. Excitation patterns revealed that limited spectral resolution dictated modulation detection thresholds at high but not low spectral modulation frequencies. Even when factoring out (presumed) differences in frequency resolution among groups, the spectral envelope perception was worse for the group with moderate hearing loss than the other 3 groups. Conclusions The spectral envelope perception as measured by spectral modulation detection thresholds is compromised by hearing loss at higher spectral modulation frequencies, consistent with predictions of reduced spectral resolution known to accompany sensorineural hearing loss. Spectral envelope perception is not negatively impacted by advancing age at any spectral modulation frequency between 0.5 and 8.0 cycles/octave.

scholarly journals Association of Auditory Steady State Responses with Perception of Temporal Modulations and Speech in Noise

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Venugopal Manju ◽  
Kizhakke Kodiyath Gopika ◽  
Pitchai Muthu Arivudai Nambi
Keyword(s):  
Steady State ◽  
Speech Perception ◽  
Amplitude Modulation ◽  
Modulation Depth ◽  
Normal Hearing ◽  
Positive Correlation ◽  
Behavioral Method ◽  
Modulation Detection ◽  
Auditory Steady State Responses ◽  
40 Hz

Amplitude modulations in the speech convey important acoustic information for speech perception. Auditory steady state response (ASSR) is thought to be physiological correlate of amplitude modulation perception. Limited research is available exploring association between ASSR and modulation detection ability as well as speech perception. Correlation of modulation detection thresholds (MDT) and speech perception in noise with ASSR was investigated in twofold experiments. 30 normal hearing individuals and 11 normal hearing individuals within age range of 18–24 years participated in experiments 1 and 2, respectively. MDTs were measured using ASSR and behavioral method at 60 Hz, 80 Hz, and 120 Hz modulation frequencies in the first experiment. ASSR threshold was obtained by estimating the minimum modulation depth required to elicit ASSR (ASSR-MDT). There was a positive correlation between behavioral MDT and ASSR-MDT at all modulation frequencies. In the second experiment, ASSR for amplitude modulation (AM) sweeps at four different frequency ranges (30–40 Hz, 40–50 Hz, 50–60 Hz, and 60–70 Hz) was recorded. Speech recognition threshold in noise (SRTn) was estimated using staircase procedure. There was a positive correlation between amplitude of ASSR for AM sweep with frequency range of 30–40 Hz and SRTn. Results of the current study suggest that ASSR provides substantial information about temporal modulation and speech perception.

The effects of modulator shape and methods for expressing modulation depth on spectral modulation detection thresholds

2019 ◽  
Vol 145 (3) ◽  
pp. 1722-1722 ◽  
Author(s):  
Sittiprapa Isarangura ◽  
Katherine Palandrani ◽  
Trevor Stavropoulos ◽  
Aaron Seitz ◽  
Eric C. Hoover ◽  
...  
Keyword(s):  
Modulation Depth ◽  
Detection Thresholds ◽  
Spectral Modulation ◽  
Modulation Detection

scholarly journals Methods for expressing spectral modulation depth and the effects of modulator shape on spectral modulation detection thresholds

2019 ◽  
Author(s):  
Sittiprapa Isarangura ◽  
Katherine N. Palandrani ◽  
Trevor Stavropoulos ◽  
Aaron Seitz ◽  
Eric C. Hoover ◽  
...  
Keyword(s):  
Modulation Depth ◽  
Detection Thresholds ◽  
Spectral Modulation ◽  
Modulation Detection

Amplitude modulation detection thresholds and associated psychometric functions.

1997 ◽  
Vol 101 (5) ◽  
pp. 3083-3083 ◽  
Author(s):  
René H. Gifford ◽  
Timothy D. Trine ◽  
D. Wesley Grantham
Keyword(s):  
Amplitude Modulation ◽  
Detection Thresholds ◽  
Modulation Detection
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