Mid-level feature differences underlie early animacy and object size distinctions: Evidence from EEG decoding

Responses to visually-presented objects along the cortical surface of the human brain have a large-scale organization reflecting the broad categorical divisions of animacy and object size. Mounting evidence indicates that this topographical organization is driven by differences between objects in mid-level perceptual features. With regard to the timing of neural responses, images of objects quickly evoke neural responses with decodable information about animacy and object size, but are mid-level features sufficient to evoke these rapid neural responses? Or is slower iterative neural processing required to untangle information about animacy and object size from mid-level features? To answer this question, we used electroencephalography(EEG) to measure human neural responses to images of objects and their texform counterparts - unrecognizable images which preserve some mid-level feature information about texture and coarse form. We found that texform images evoked neural responses with early decodable information about both animacy and real-world size, as early as responses evoked by original images. Further, successful cross-decoding indicates that both texform and original images evoke information about animacy and size through a common underlying neural basis. Broadly, these results indicate that the visual system contains a mid-level feature bank carrying linearly decodable information on animacy and size, which can be rapidly activated without requiring explicit recognition or protracted temporal processing.

Perception of Deep Band Modulated Speech in the Presence of Noise by Elderly Individuals with Hearing Impairment

Background: Deep band modulation (DBM) is an envelope enhancement strategy that enhances temporal modulation and may provide a cue for speech understanding among individuals who suffer from temporal processing deficits. Objective: To investigate the effect of deep band modulation on phrase recognition scores at different signal-to-noise ratios (SNRs) among older adults having hearing loss classified as good and poor performers based on temporal resolution ability. Method: Phrase recognition score was obtained for unprocessed and DBM phrases at three SNRs (4, 5, and - 4 dB signal to noise ratio) in 25 (age range 60 to 82 years, mean age 71.48 years) older adults having bilateral mild to moderately severe sloping sensorineural hearing loss. In addition, the gap detection test was also administered to the study participants. Results: A significant better recognition score was obtained in DBM than the unprocessed phrase. The magnitude of improvement from DBM was not the same in all the participants. Thus, the participants were classified into good and poor performers based on their temporal processing ability. The mean unprocessed and DBM phrase recognition scores in each SNR were higher for good performers than the poor performers. The benefit of deep band modulation was evident for the good performers, especially at high SNR, which was moderately correlated with age and temporal processing ability. Conclusion: The benefit from DBM on recognition score for the good performers is predicted from the temporal resolution abilities and age. However, the benefit is minuscule for the poor performers in noise.

The Mind Is a DJ: Rhythmic Entrainment in Beatmatching and Embodied Temporal Processing

In music, rhythmic entrainment occurs when the attention and body movements of listeners, dancers and musicians become synchronized with the beat. This synchronization occurs due to the mechanisms of phase and period correction. Here, I describe what happens to these mechanisms during beatmatching—a central skill in DJing that involves synchronizing the beats of two records on a set of turntables. Via the enactivist approach to the embodied mind, I argue that beatmatching affords a different form of entrainment that requires more conscious control of and embodied operationalization of temporal error correction, and thus provides a vivid model of the embodied distribution of rhythmic entrainment.

Rate discrimination training may partially restore temporal processing abilities from age-related deficits

The ability to understand speech in complex environments depends on the ability of the brain to preserve the precise timing characteristics of the speech signal. Age-related declines in temporal processing may contribute to the communication difficulties in challenging listening conditions experienced by older adults. The study purpose was to evaluate the effects of rate discrimination training on auditory temporal processing. A double-blind, randomized control design assigned 77 young normal-hearing, older normal-hearing, and older hearing-impaired listeners to one of two treatment groups: experimental (rate discrimination for 100-Hz and 300-Hz pulse trains) and active control (tone detection in noise). All listeners were evaluated during pre- and post-training sessions using perceptual rate discrimination of 100-, 200-, 300-, and 400-Hz band-limited pulse trains and auditory steady-state responses (ASSRs) to the same stimuli. Training generalization was evaluated using several temporal processing measures and sentence recognition tests that included time-compressed and reverberant speech stimuli. Results demonstrated a session x training group interaction for perceptual and ASSR testing to the trained frequencies (100 and 300 Hz), driven by greater improvements in the training group than in the active control group. Further, post-test rate discrimination of the older listeners reached levels that were equivalent to those of the younger listeners at pre-test. The training-specific gains generalized to untrained frequencies (200 and 400 Hz), but not to other temporal processing or sentence recognition measures. Further, non-auditory inhibition/attention performance predicted training-related improvement in rate discrimination. Overall, the results demonstrate the potential for auditory training to partially restore temporal processing in older listeners and highlight the role of cognitive function in these gains.

Neural Basis of Acoustic Species Recognition in a Cryptic Species Complex

Sexual traits that promote species recognition are important drivers of reproductive isolation, especially among closely related species. Identifying neural processes that shape species differences in recognition is crucial for understanding the causal mechanisms of reproductive isolation. Temporal patterns are salient features of sexual signals widely used in species recognition by several taxa, including anurans. Recent advances in our understanding of temporal processing by the anuran auditory system provide an opportunity to investigate the neural basis of species-specific recognition. The anuran inferior colliculus (IC) consists of neurons that are selective for temporal features of calls. Of potential relevance are auditory neurons known as interval-counting neurons (ICNs) that are often selective for the pulse rate of conspecific advertisement calls. Here, we tested the hypothesis that ICNs mediate acoustic species recognition by exploiting the known differences in temporal selectivity in two cryptic species of gray treefrog (Hyla chrysoscelis and Hyla versicolor). We examined the extent to which the threshold number of pulses required to elicit behavioral responses from females and neural responses from ICNs was similar within each species but potentially different between the two species. In support of our hypothesis, we found that a species difference in behavioral pulse number thresholds closely matched the species difference in neural pulse number thresholds. However, this relationship held only for ICNs that exhibited band-pass tuning for conspecific pulse rates. Together, these findings suggest that differences in temporal processing of a subset of ICNs provide a mechanistic explanation for reproductive isolation between two cryptic treefrog species.

The development of auditory temporal processing during the first year of life

The processing of auditory temporal information is important for the extraction of voice pitch, linguistic information, as well as the overall temporal structure of speech. However, many aspects regarding its early development remains not well understood. This paper reviews the development of different aspects of auditory temporal processing during the first year of life when infants are acquiring their native language. First, potential mechanisms of neural immaturity are discussed in the context of neurophysiological studies. Next, what is known about infant auditory capabilities is considered with a focus on psychophysical studies involving non-speech stimuli to investigate the perception of temporal fine structure and envelope cues. This is followed by a review of studies involving speech stimuli, including those that present vocoded signals as a method of degrading the spectro-temporal information available to infant listeners. Finally, we highlight key findings from the cochlear implant literature that illustrate the importance of temporal cues in speech perception.