Temporal Modulation Transfer Functions Research Articles

Assessment of temporal resolution and detectability of moving objects in CT: A task-based image quality study

The metrics used for assessing image quality in computed tomography (CT) do not integrate the influence of temporal resolution. A shortcoming in the assessment of image quality for imaging protocols where motion blur can therefore occur. We developed a method to calculate the temporal resolution of standard CT protocols and introduced a specific spatiotemporal formulation of the non-prewhitening with eye filter (NPWE) model observer to assess the detectability of moving objects as a function of their speed. We scanned a cubic water phantom with a plexiglass cylindrical insert (120 HU) using a large panel of acquisition parameters (rotation times, pitch factors and collimation widths) on two systems (GE Revolution Apex and Siemens SOMATOM Force) to determine the in-plane task-based transfer functions (TTF) and noise power spectra (NPS). The phantom set in a uniform rectilinear motion in the transverse plane allowed the temporal modulation transfer function (MTF) calculation. The temporal MTF appropriately compared the temporal resolution of the various acquisition protocols. The longitudinal TTF was measured using a thin tungsten wire. The detectability index showed the advantage of applying high rotation speed, wide collimations and high pitch for object detection in the presence of motion. No counterpart to the increase in these three parameters was found in the in-plane and longitudinal image quality.

Behavioral characterization of the cochlear amplifier lesion due to loss of function of stereocilin (STRC) in human subjects

Loss of function of stereocilin (STRC) is the second most common cause of inherited hearing loss. The loss of the stereocilin protein, encoded by the STRC gene, induces the loss of connection between outer hair cells and tectorial membrane. This only affects the outer hair cells (OHCs) function, involving deficits of active cochlear frequency selectivity and amplifier functions despite preservation of normal inner hair cells. Better understanding of cochlear features associated with mutation of STRC will improve our knowledge of normal cochlear function, the pathophysiology of hearing impairment, and potentially enhance hearing aid and cochlear implant signal processing. Nine subjects with homozygous or compound heterozygous loss of function mutations in STRC were included, age 7–24 years. Temporal and spectral modulation perception were measured, characterized by spectral and temporal modulation transfer functions. Speech-in-noise perception was studied with spondee identification in adaptive steady-state noise and AzBio sentences with 0 and -5 dB SNR multitalker babble. Results were compared with normal hearing (NH) and cochlear implant (CI) listeners to place STRC−/− listeners’ hearing capacity in context. Spectral ripple discrimination thresholds in the STRC−/− subjects were poorer than in NH listeners (p < 0.0001) but remained better than for CI listeners (p < 0.0001). Frequency resolution appeared impaired in the STRC−/− group compared to NH listeners but did not reach statistical significance (p = 0.06). Compared to NH listeners, amplitude modulation detection thresholds in the STRC−/− group did not reach significance (p= 0.06) but were better than in CI subjects (p < 0.0001). Temporal resolution in STRC−/− subjects was similar to NH (p = 0.98) but better than in CI listeners (p = 0.04). The spondee reception threshold in the STRC−/− group was worse than NH listeners (p = 0.0008) but better than CI listeners (p = 0.0001). For AzBio sentences, performance at 0 dB SNR was similar between the STRC−/− group and the NH group, 88 % and 97 % respectively. For -5 dB SNR, the STRC−/− performance was significantly poorer than NH, 40 % and 85 % respectively, yet much better than with CI who performed at 54 % at +5 dB SNR in children and 53 % at + 10 dB SNR in adults. To our knowledge, this is the first study of the psychoacoustic performance of human subjects lacking cochlear amplification but with normal inner hair cell function. Our data demonstrate preservation of temporal resolution and a trend to impaired frequency resolution in this group without reaching statistical significance. Speech-in-noise perception compared to NH listeners was impaired as well. All measures were better than those in CI listeners. It remains to be seen if hearing aid modifications, customized for the spectral deficits in STRC−/− listeners can improve speech understanding in noise. Since cochlear implants are also limited by deficient spectral selectivity, STRC−/− hearing may provide an upper bound on what could be obtained with better temporal coding in electrical stimulation.

EEG-based auditory attention decoding with audiovisual speech for hearing-impaired listeners.

Auditory attention decoding (AAD) was used to determine the attended speaker during an auditory selective attention task. However, the auditory factors modulating AAD remained unclear for hearing-impaired (HI) listeners. In this study, scalp electroencephalogram (EEG) was recorded with an auditory selective attention paradigm, in which HI listeners were instructed to attend one of the two simultaneous speech streams with or without congruent visual input (articulation movements), and at a high or low target-to-masker ratio (TMR). Meanwhile, behavioral hearing tests (i.e. audiogram, speech reception threshold, temporal modulation transfer function) were used to assess listeners' individual auditory abilities. The results showed that both visual input and increasing TMR could significantly enhance the cortical tracking of the attended speech and AAD accuracy. Further analysis revealed that the audiovisual (AV) gain in attended speech cortical tracking was significantly correlated with listeners' auditory amplitude modulation (AM) sensitivity, and the TMR gain in attended speech cortical tracking was significantly correlated with listeners' hearing thresholds. Temporal response function analysis revealed that subjects with higher AM sensitivity demonstrated more AV gain over the right occipitotemporal and bilateral frontocentral scalp electrodes.

Assessment of auditory perception abilities using temporal envelope and fine structure processing in children with self-limited epilepsy with centrotemporal spikes

ObjectivesChildren with self-limited epilepsy with centrotemporal spikes (SeLECTS) exhibit difficulty processing spoken messages without hearing loss. The temporal envelope and fine structure processing abilities are the fundamental aspects of the normal listening process. There is limited literature on the temporal envelope and fine structure processing in children with SeLECTS. We evaluated the temporal envelope and fine structure processing in children with SeLECTS. DesignThe study included 35 children with SeLECTS and 50 typically developing children (TDC). The temporal envelope processing was measured using the temporal modulation transfer function (TMTF) and temporal fine structure using the temporal fine structure low-frequency (TFS LF) test. The TMTF was measured for the modulation rates 4, 8, 16, 32, 64 and 128 Hz. The TFS LF was done for 250, 500 and 750 Hz. ResultsThe difference in modulation detection thresholds at 4 Hz was not found to be significant, whereas there was a significant difference in modulation detection thresholds observed for all the other modulation frequencies (p < 0.05) between the children with SeLECTS and TDC. The thresholds at 250, 500 and 750 Hz were higher (poorer) for children with SeLECTS than the TDC and was significant (p < 0.05). ConclusionsThe TMTF and TFS LF tests were of practical use in evaluating temporal envelope and fine structure processing abilities in children with SeLECTS. The results suggest that children with SeLECTS have a poor temporal envelope and fine structure processing compared to the TDC.

Does Binaural Stimulation Enhance Temporal Processing in Young Children?

Background and objective Temporal processing abilities help perceive signal changes over time. Efficient temporal processing is necessary for pitch perception, voice identification, and speech perception. It plays a significant role in language development. Internal redundancy of the central auditory nervous plays a role in processing sensory information. There is a need to gain more insights into the maturation of neural hardwiring that supports binaural temporal processing at a young age. The purpose of the present study was to evaluate the difference between monaural and binaural temporal processing in children aged 7-11 years. Methods Temporal processing was assessed using gap detection and temporal modulation transfer function (TMTF) tests. The tests were administered in 40 typically developing children with normal clinical auditory sensitivity. The maximum likelihood procedure (MLP), a MATLAB toolbox, was employed to deliver the stimulus. A multivariate analysis followed by post hoc analysis was performed to analyze the data. Results There was a significant difference between binaural and monoaural stimulation in children aged 7-11 years. However, there was no statistically significant difference between the right and left ears for gap detection threshold (GDT) and TMTF across all test frequencies. Conclusion Based on our findings, binaural stimulation enhances temporal processing in young children.

Effect of Contralateral Acoustic Stimulation on Temporal Processing Abilities in Individuals with Normal Hearing.

The aim of the article was to compare the conditions of silent and contralateral noise on the temporal processing parameters. A total of 40 participants (20 males and 20 females) were enrolled in the study with a mean age of 21.7years, participants with normal hearing thresholds and no history of middle ear pathology were enrolled for the study. The temporal processing tests such as duration discrimination test, gap detection test, and temporal modulation transfer function tests were carried out in these 40 individuals in the two conditions of silent and contralateral noise using MATLAB. Statistical analysis was carried out using the SPSS version 25.0 were descriptive and inferential statistics were carried out. Data was normally distributed on the Shapiro-Wilk's test of normality due to which a paired t test was carried out to establish the nature of significance between the silent and contralateral noise condition. Results reveal the presence of significant difference (p < 0.01) between the groups for all the parameters of temporal resolution with contralateral noise condition performing better than silent condition for the parameters. There is a positive effect of the efferent auditory pathway on the temporal resolution parameters thus implying that speech perception in noise is improved in the presence of background noise for normal hearing individuals due to this effect.

Listening Effort in Prelingual Cochlear Implant Recipients: Effects of Spectral and Temporal Auditory Processing and Contralateral Acoustic Hearing.

Considering the impact of listening effort (LE) on auditory perception, attention, and memory, it is a significant aspect in the daily hearing experiences of cochlear implant (CI) recipients. Reduced spectral and temporal information on an acoustic signal can make listening more difficult; as a result, it is important to understand the relationship between LE and spectral and temporal auditory processing capacities in CI receivers. This study used spectral ripple discrimination and temporal modulation transfer function to evaluate 20 prelingually deafened and early implanted CI recipients. The speech perception in noise test (primary) and the digit recall task (DRT-secondary) were used to assess LE using the dual-task paradigm. To assess the effects of acoustic hearing, contralateral acoustic hearing thresholds between 125 Hz and 8 kHz with a hearing aid were also acquired. To examine the relationship between the research variables, correlation coefficients were generated. Furthermore, the Mann-Whitney U test was used to compare unilateral and bimodal users. There was a statistically significant correlation between LE and spectral ripple discrimination (r = 0.56; p = 0.011), 125 Hz (r = 0.51; p = 0.020), 250 Hz (r = 0.48; p = 0.030), 500 Hz (r = 0.45; p = 0.045), 1,000 Hz (r = 0.51; p = 0.023), 2000 Hz (r = 0.48; p = 0.031), and 4,000 Hz (r = 0.48; p = 0.031), whereas no statistically significant correlations were observed between temporal modulation transfer function in four frequencies and LE. There was no statistically significant difference between unilateral and bimodal CI recipients ( p > 0.05). As a result of the improved signal-to-noise ratio in the auditory environment, CI users with better spectral resolutions and acoustic hearing have a reduced LE. On the other hand, temporal auditory processing, as measured by temporal modulation detection, does not contribute to the LE.

Evaluation of phase-locking to parameterized speech envelopes.

Humans rely on the temporal processing ability of the auditory system to perceive speech during everyday communication. The temporal envelope of speech is essential for speech perception, particularly envelope modulations below 20 Hz. In the literature, the neural representation of this speech envelope is usually investigated by recording neural phase-locked responses to speech stimuli. However, these phase-locked responses are not only associated with envelope modulation processing, but also with processing of linguistic information at a higher-order level when speech is comprehended. It is thus difficult to disentangle the responses into components from the acoustic envelope itself and the linguistic structures in speech (such as words, phrases and sentences). Another way to investigate neural modulation processing is to use sinusoidal amplitude-modulated stimuli at different modulation frequencies to obtain the temporal modulation transfer function. However, these transfer functions are considerably variable across modulation frequencies and individual listeners. To tackle the issues of both speech and sinusoidal amplitude-modulated stimuli, the recently introduced Temporal Speech Envelope Tracking (TEMPEST) framework proposed the use of stimuli with a distribution of envelope modulations. The framework aims to assess the brain's capability to process temporal envelopes in different frequency bands using stimuli with speech-like envelope modulations. In this study, we provide a proof-of-concept of the framework using stimuli with modulation frequency bands around the syllable and phoneme rate in natural speech. We evaluated whether the evoked phase-locked neural activity correlates with the speech-weighted modulation transfer function measured using sinusoidal amplitude-modulated stimuli in normal-hearing listeners. Since many studies on modulation processing employ different metrics and comparing their results is difficult, we included different power- and phase-based metrics and investigate how these metrics relate to each other. Results reveal a strong correspondence across listeners between the neural activity evoked by the speech-like stimuli and the activity evoked by the sinusoidal amplitude-modulated stimuli. Furthermore, strong correspondence was also apparent between each metric, facilitating comparisons between studies using different metrics. These findings indicate the potential of the TEMPEST framework to efficiently assess the neural capability to process temporal envelope modulations within a frequency band that is important for speech perception.

Threshold and frequency- and temporal resolutions of distantly presented bone-conducted sound in the audible-frequency range

As a vibrator needs to be pressed onto the osseous parts of the head, bone conduction is often accompanied by pain and esthetic problems. To solve these problems, a “distant presentation” that involves presenting vibrators to the neck, trunk, or upper limb was proposed. Our previous studies focused on the perceptual and propagation characteristics of distantly presented bone-conducted sounds in the ultrasonic range. However, only a few studies have been conducted in the audible-frequency range. In this study, to examine the basic properties of distantly presented bone-conduction perception in the audible-frequency range, hearing thresholds, difference limens for frequency, and temporal modulation transfer functions were measured with insulated air-conducted sounds. The results indicate that the distance attenuation is much larger than that in the ultrasonic range, and the degradation of frequency and temporal information occurring in the propagation process of bone-conducted sounds is sufficiently small for the transmission of sound information.

Topographical distribution of spectrotemporal receptive field properties in the bat primary auditory cortex

Spectrotemporal modulations are a prominent feature of natural sounds including animal vocalizations and human speech. Echolocating bats must process spectrotemporal cues such as echo delays and spectrum properties to navigate their environment; however, the neuronal networks in the primary auditory cortex (A1) that process features of natural sounds remain incompletely understood. Here, we investigated the topographical distribution of tuning properties throughout A1 of Mexican free-tailed bats. While the majority of the bats’ A1 neurons are tuned to downward FM sweeps, the entire cortex is required to capture and categorize patterns of spectral details embedded within each biosonar echo. We captured the neural responses of the A1 to complex acoustic stimuli using linear, 16-channel translaminar microelectrode arrays. We analyzed 145 spectrotemporal receptive fields (STRFs) across A1, as well as the spectral and temporal modulation transfer functions (sMTF and tMTF, respectively) to determine neural tuning preferences in the spectral and temporal dimensions. We found evidence of neuronal sub-categories that were classified as having simple or complex (multi-peaked) STRFs. For simple STRFs, sMTFs and tMTFs were evaluated as a function of best frequency, and spatial location and revealed tonotopic trends similar to those reported for non-specialized animals.

Temporal Modulation Transfer Functions of Amplitude-Modulated Cervical Vestibular-Evoked Myogenic Potentials in Young Adults.

Cervical vestibular-evoked myogenic potentials (cVEMPs) are widely used to evaluate saccular function in clinical and research applications. Typically, transient tonebursts are used to elicit cVEMPs. In this study, we used bone-conducted amplitude-modulated (AM) tones to elicit AMcVEMPs. This new approach allows the examination of phase-locked vestibular responses across a range of modulation frequencies. Currently, cVEMP temporal modulation transfer functions (TMTFs) are not well defined. The purposes of the present study were (1) to characterize the AMcVEMP TMTF in young, healthy individuals, (2) to compare AMcVEMP TMTFs across different analysis approaches, and (3) to determine the upper frequency limit of the AMcVEMP TMTF. Young adults (ages 21 to 25) with no history of vestibular lesions or middle ear pathologies participated in this study. Stimuli were amplitude-modulated tones with a carrier frequency of 500 Hz and modulation frequencies ranging from 7 to 403 Hz. Stimuli were presented at 65 dB HL via a B81 bone-oscillator. AMcVEMP waveforms consisted of transient onset responses, steady-state responses, and transient offset responses; the behavior of these different types of responses varied with modulation frequency. Differences in the TMTF shape were noted across different measures. The amplitude TMTF had a sharp peak, while signal-to-noise ratio and phase coherence TMTFs had broader shapes with plateaus across a range of modulation frequencies. Amplitude was maximal at modulation frequencies of 29 and 37 Hz. Signal-to-noise ratio maintained its peak value at modulation frequencies between 17 Hz and 127 Hz. Phase coherence and modulation gain maintained their peak values at modulation frequencies between 17 Hz and 143 Hz. AMcVEMPs reflect transient onset and offset responses, as well as a sustained response with the periodicity of an amplitude-modulation frequency. AMcVEMP TMTFs had variable shapes depending on the analysis being applied to the response; amplitude had a narrow shape while others were broader. Average upper frequency limits of the AMcVEMP TMTF were as high as approximately 300 Hz in young, healthy adults.

Temporal MTF evaluation of slow motion mode in mobile phones

While slow motion has become a standard feature in mainstream cell phones, a fast approach without relying on specific training datasets to assess slow motion video quality is not available. This manuscript proposes a fast and generalized no-reference objective metric based on temporal loss in modulation transfer function (MTF) to evaluate interpolated slow motion mode in mobile phones. First, a standard chart embodying slanted edges is used to capture a slow-motion video. Second, the edge spread function is extracted from a region of interest in individual slow motion frames. Third, the line spread functions and MTFs are calculated. Finally, reference and interpolated frames are identified. Sharpness loss in slow motion mode is quantified by the MTF area difference between minimum interpolated frame and reference frame MTF scores. The proposed approach is evaluated in simulated and experimentally captured slow motion videos. In experiments, slow-motion videos are captured by moving mobile phones mounted on a motorized linear stage apart from the test chart at a constant speed while keeping the test chart still. The proposed MTF scores of several mainstream cell phones are analyzed and compared.

Basic properties of distantly-presented bone-conduction perception.

Since a vibrator needs to be pressed onto the osseous parts of the head, bone-conduction (BC) is often accompanied by pain and esthetic problems. In order to solve these problems, "distant presentation" has been proposed. In the distant presentation, vibrators are presented to the neck, upper limb or trunk. Our previous studies focused on the perception and propagation characteristics of distantly-presented BC sound in the ultrasonic range and an application to a novel audio-interface. On the other hand, a limited number of studies have been conducted on distantly-presented BC in the audible-frequency range. In this study, to examine the basic properties of the distantly-presented BC perception in the audible-frequency range, hearing thresholds, difference limens for frequency (DLFs) and temporal modulation transfer functions (TMTFs) were measured under the condition that AC sounds were insulated sufficiently. The results obtained indicated that BC sounds can be clearly perceived at distal parts of the body even in the audible-frequency range and no significant degradation of frequency and temporal information occurs in the propagation process in the body.

Determining attributed factors of hearing handicap in individuals with auditory sensory and neural pathology

IntroductionThere is a modest relationship between speech perception skills and perceived hearing handicap in individuals with hearing loss. In this study, an attempt is made at linking psychoacoustic results and speech perception skills to understand the subjective handicap and quality of life. ObjectiveTo investigate how speech perception in noise (signal to noise ratio-50), difference limen frequency, temporal modulation transfer function, hearing handicap inventory for adults, and quality of life in auditory neuropathy spectrum disorder differs from sensorineural hearing loss. Further we attempt to discern attributed factors of hearing handicap in auditory neuropathy spectrum disorder and sensorineural hearing loss. MethodsA cross-sectional study with comparative and correlational research designs were utilized. Eighty-four participants were grouped into sensorineural hearing loss (n = 49), and auditory neuropathy spectrum disorder (n = 35) was sub-grouped into mild, moderately severe, and severe. We evaluated signal to noise ratio-50, difference limen frequency, and temporal modulation transfer function. In addition, hearing handicap inventory for adults, and quality of life questionnaires were administered. ResultsMild auditory neuropathy spectrum disorder showed impairment in speech perception and discriminating frequency, which were similar to the severe sensory neural hearing loss. Temporal resolution impairment in auditory neuropathy spectrum disorder mild was significantly higher than in each sub-groups of sensorineural hearing loss. The severity of the hearing handicap in was similar to severe sensorineural hearing loss, quality of life was equally affected in sensorineural hearing loss and auditory neuropathy spectrum disorder. In sensorineural hearing loss, signal to noise ratio-50 was positively related, and quality of life was negatively related to hearing handicap. In auditory neuropathy spectrum disorder, no contributory factors were related to hearing handicap. ConclusionMild auditory neural pathology demonstrates impairment in speech recognition and psychoacoustic skills similar to severe cochlear pathology. In sensorineural hearing loss, hearing handicap is predicted from quality of life and speech perception, but none of the contributory factors predicted hearing handicap in auditory neuropathy spectrum disorder.

Effects of diurnal changes on temporal processing in morning-type and evening-type individuals with normal hearing

The present study aims at determining the influence of diurnal changes in duration discrimination and temporal resolution in the morning- and evening-type individuals with normal hearing sensitivity. Sixty individuals with normal hearing were divided into morning, evening and intermediate types using the Morningness-Eveningness Questionnaire. Tests for Duration discrimination, Gap detection, and Temporal modulation transfer function were carried out in all the participants during morning and evening. The performance of subjects of all the three groups during both morning and evening was analyzed. Results revealed a diurnal effect on morning and evening type individuals' performance where morning type exhibited better performance when tested during morning and evening individuals when tested during the evening. At the same time, there were no significant diurnal effects seen in the intermediate type. The poor cognitive performance and lack of inhibitory control at the time of the off-peak hours possibly result in the poor scores. Furthermore, the diurnal effects on objective audiological tests in morning and evening type individuals should be studied. The influence of diurnal changes could be considered an extraneous variable in future research on psychoacoustic tests in younger adults.

Assessment of Hidden Hearing Loss in Individuals Exposed to Occupational Noise Using Cochlear, Neural, Temporal Functions and Quality of Life Measures.

The present study aims to identify the objective tests that can identify hidden hearing loss in a group of individuals exposed to occupational noise, which is not otherwise evident as a clinically relevant permanent threshold shift. A standard group comparison design was used to study the hidden auditory effect of occupational noise on traffic police officers. A total of 50 participants (n = 25 exposed to occupational noise; n = 25 non-occupational noise-exposed) were included in the study. The test battery comprised of behavioral tests (hearing thresholds from 250 to 16,000Hz), fine structure Distortion product otoacoustic emissions (DPOAE's) as physiological measure, Click and CE-chirp® evoked auditory brain stem response (ABR) as electrophysiological, and Gap detection test (GDT) and Temporal modulation transfer function (TMTF) as psychophysical measures. Among the measures evaluated, extended high-frequency audiometry, fine structure DPOAE amplitude, CE-chirp® ABR, GDT, and TMTF showed a significant difference (p < 0.05) between the traffic police individuals exposed to occupational noise and the controls. However, routine audiometry and click-evoked ABR did not show any significant differences. The high-frequency audiometric thresholds, fine structure DPOAEs, CE-chirp® evoked ABR, GDT and TMTF have been shown to be affected in individuals exposed to occupational noise. This finding indicates a hidden hearing loss in the study group. Hence, this study paves the way for early identification and intervention of noise-induced hearing loss by including these measures along with routine test protocol in susceptible individuals.

Stimulus-evoked phase-locked activity along the human auditory pathway strongly varies across individuals

Phase-locking to the temporal envelope of speech is associated with envelope processing and speech perception. The phase-locked activity of the auditory pathway, across modulation frequencies, is generally assessed at group level and shows a decrease in response magnitude with increasing modulation frequency. With the exception of increased activity around 40 and 80 to 100 Hz. Furthermore, little is known about the phase-locked response patterns to modulation frequencies ≤ 20 Hz, which are modulations predominately present in the speech envelope. In the present study we assess the temporal modulation transfer function (TMTFASSR) of the phase-locked activity of the auditory pathway, from 0.5 to 100 Hz at a high-resolution and by means of auditory steady-state responses. Although the group-averaged TMTFASSR corresponds well with those reported in the literature, the individual TMTFASSR shows a remarkable intersubject variability. This intersubject variability is especially present for ASSRs that originate from the cortex and are evoked with modulation frequencies ≤ 20 Hz. Moreover, we found that these cortical phase-locked activity patterns are robust over time. These results show the importance of the individual TMTFASSR when assessing phase-locked activity to envelope fluctuations, which can potentially be used as a marker for auditory processing.

Age-related decline in motion contrast sensitivity due to lower absorption rate of cones and calculation efficiency

Motion perception is affected by healthy aging, which impairs the ability of older adults to perform some daily activities such as driving. The current study investigated the underlying causes of age-related motion contrast sensitivity losses by using an equivalent noise paradigm to decompose motion contrast sensitivity into calculation efficiency, the temporal modulation transfer function (i.e., temporal blur) and 3 sources of internal noise: stochastic absorption of photons by photoreceptors (i.e., photon noise), neural noise occurring at the retinal level (i.e., early noise) and at the cortical level (i.e., late noise). These sources of internal noise can be disentangled because there impacts on motion contrast sensitivity vary differently as a function of luminance intensity. The impact of healthy aging on these factors was evaluated by measuring motion contrast sensitivity of young and older healthy adults at different luminance intensities, temporal frequencies and with/without external noise. The older adults were found to have higher photon noise, which suggests a lower photon absorption rate of cones. When roughly equating the amount of photons being absorbed by the photoreceptors, older adults had lower calculation efficiencies, but no significant aging effect was found on temporal modulation transfer function, early noise and late noise.

The rhythm of attention: Perceptual modulation via rhythmic entrainment is lowpass and attention mediated.

Modulation patterns are known to carry critical predictive cues to signal detection in complex acoustic environments. The current study investigated the persistence of masker modulation effects on postmodulation detection of probe signals. Hickok, Farahbod, and Saberi (Psychological Science, 26, 1006-1013, 2015) demonstrated that thresholds for a tone pulse in stationary noise follow a predictable periodic pattern when preceded by a 3-Hz amplitude modulated masker. They found entrainment of detection patterns to the modulation envelope lasting for approximately two cycles after termination of modulation. The current study extends these results to a wide range of modulation rates by mapping the temporal modulation transfer function for persistent modulatory effects. We found significant entrainment to modulation rates of 2 and 3 Hz, a weaker effect at 5 Hz, and no entrainment at higher rates (8 to 32 Hz). The effect seems critically dependent on attentional mechanisms, requiring temporal and level uncertainty of the probe signal. Our findings suggest that the persistence of modulatory effects on signal detection is lowpass in nature and attention based.

Acoustic Change Responses to Amplitude Modulation in Cochlear Implant Users: Relationships to Speech Perception.

ObjectivesThe ability to understand speech is highly variable in people with cochlear implants (CIs) and to date, there are no objective measures that identify the root of this discrepancy. However, behavioral measures of temporal processing such as the temporal modulation transfer function (TMTF) has previously found to be related to vowel and consonant identification in CI users. The acoustic change complex (ACC) is a cortical auditory-evoked potential response that can be elicited by a “change” in an ongoing stimulus. In this study, the ACC elicited by amplitude modulation (AM) change was related to measures of speech perception as well as the amplitude detection threshold in CI users.MethodsTen CI users (mean age: 50 years old) participated in this study. All subjects participated in behavioral tests that included both speech and amplitude modulation detection to obtain a TMTF. CI users were categorized as “good” (n = 6) or “poor” (n = 4) based on their speech-in noise score (<50%). 64-channel electroencephalographic recordings were conducted while CI users passively listened to AM change sounds that were presented in a free field setting. The AM change stimulus was white noise with four different AM rates (4, 40, 100, and 300 Hz).ResultsBehavioral results show that AM detection thresholds in CI users were higher compared to the normal-hearing (NH) group for all AM rates. The electrophysiological data suggest that N1 responses were significantly decreased in amplitude and their latencies were increased in CI users compared to NH controls. In addition, the N1 latencies for the poor CI performers were delayed compared to the good CI performers. The N1 latency for 40 Hz AM was correlated with various speech perception measures.ConclusionOur data suggest that the ACC to AM change provides an objective index of speech perception abilities that can be used to explain some of the variation in speech perception observed among CI users.