Rapid Alternate Flicker Modulates Binocular Interaction in Adults With Abnormal Binocular Vision.

Purpose: The current understanding of binocular processing is primarily derived from static spatial visual perception: this leaves the role of temporal information unclear. In this study, we addressed this gap by testing the effect of alternating flicker on binocular information processing in adults with abnormal binocular vision. Our goal was to determine which temporal frequency optimally balanced input from both eyes. Methods: We took measurements in four groups of human adults: 10 normal adults with the individual's nondominant eye covered by a 2% neutral density filter (aged 25.60 ± 1.43 years, experiment 1), 9 nonamblyopic anisometropes (aged 24.33 ± 1.66 years, experiment 2), 7 amblyopes (aged 26.5 ± 1.64 years, experiment 3), and 7 treated amblyopes (aged 24 ± 3.21 years, experiment 4). The balance point (BP), where participants' two eyes are equally effective, was measured using a binocular orientation combination task at four spatial frequencies (SFs; 0.5-4 c/d) and five temporal frequencies (TFs; baseline and 4, 7, 10, and 15 Hz). Its log transformation |logBP| was taken into further analysis. Results: We observed clear U-shaped temporal tuning of the |logBP| for the entire range of TFs (that we measured: trough occurred at 7 Hz). This pattern occurred and was significant in all four groups (P < 0.001). In addition, the effect of SFs on |logBP| was significant in normal, amblyopic, and treated amblyopic groups (all P < 0.001) and was marginally significant in the nonamblyopic anisometropic group (P = 0.086). Conclusions: Alternating flicker around 7 Hz may be the optimal temporal frequency for balancing eyes in human adults with binocular imbalance.

Temporal synchrony discrimination is abnormal in dichoptic but not monocular visual processing in treated anisometropic amblyopes.

PURPOSE: To evaluate whether temporal synchrony processing deficits remain when normal visual acuity is restored in adults with unilateral anisometropic amblyopia. METHODS: We recruited 14 clinically treated anisometropic amblyopes (mean age 23.17 ± 2.53 years) with best-corrected visual acuity ≤ 0.1 logMAR and 15 age-matched emmetropes (mean age 24.40 ± 1.92 years) with normal vision to participate in our experiment. We presented two pairs of flicking Gaussian dots (1 Hz) as visual stimuli: one pair of dots was synchronous (reference), and the other pair of dots was asynchronous (signal). Subjects were asked to determine the position of the asynchronous pair. We applied the constant stimuli method to measure the temporal synchrony threshold under monocular and dichoptic viewing conditions. There were eight temporal phase lags in the asynchronous pair. The minimum degree of the temporal phase at which a participant can discriminate a signal pair is defined as the temporal synchrony threshold. RESULTS: Under monocular viewing conditions where both the reference and signal pairs were presented to one eye, the temporal synchrony thresholds of previous amblyopic eyes and fellow eyes were not significantly different (p = 0.15). Under dichoptic viewing conditions where both the reference and signal pairs were dichoptically presented to both eyes, the temporal synchrony threshold in the treated anisometropic amblyopes was significantly higher than that of the controls (119.34 ± 20.43 vs. 99.78 ± 16.60 ms, p = 0.009). There was no significant correlation between the monocular and dichoptic viewing conditions in the treated amblyopes (r = -0.22, p = 0.94). CONCLUSIONS: Temporal synchrony discrimination is abnormal under dichoptic but not under monocular visual stimulation in treated anisometropic amblyopes with normalised visual acuity.

Internal neural states influence the short-term effect of monocular deprivation in human adults.

The adult human visual system maintains the ability to be altered by sensory deprivation. What has not been considered is whether the internal neural states modulate visual sensitivity to short-term monocular deprivation. In this study we manipulated the internal neural state and reported changes in intrinsic neural oscillations with a patched eye open or closed. We investigated the influence of eye open/eye closure on the unpatched eye's contrast sensitivity and ocular dominance (OD) shifts induced by short-term monocular deprivation. The results demonstrate that internal neural states influence not only baseline contrast sensitivity but also the extent to which the adult visual system can undergo changes in ocular dominance.

Orthography influences spoken word production in blocked cyclic naming.

Does the way a word is written influence its spoken production? Previous studies suggest that orthography is involved only when the orthographic representation is highly relevant during speaking (e.g., in reading-aloud tasks). To address this issue, we carried out two experiments using the blocked cyclic picture-naming paradigm. In both experiments, participants were asked to name pictures repeatedly in orthographically homogeneous or heterogeneous blocks. In the naming task, the written form was not shown; however, the radical of the first character overlapped between the four pictures in this block type. A facilitative orthographic effect was found when picture names shared part of their written forms, compared with the heterogeneous condition. This facilitative effect was independent of the position of orthographic overlap (i.e., the left, the lower, or the outer part of the character). These findings strongly suggest that orthography can influence speaking even when it is not highly relevant (i.e., during picture naming) and the orthographic effect is less likely to be attributed to strategic preparation.

The effects of lexical frequency and homophone neighborhood density on incomplete tonal neutralization.

We investigated the effects of lexical frequency and homophone neighborhood density on the acoustic realization of two neutralizing falling tones in Dalian Mandarin Chinese. Monosyllabic morphemes containing the target tones (Tone 1 and Tone 4) were produced by 60 native speakers from two generations (middle-aged vs. young). The duration of tone-bearing syllable rhymes, as well as the F0 curves and velocity profiles of the lexical tones were quantitatively analyzed via linear mixed-effects modeling and functional data analysis. Results showed no durational difference between T1 and T4. However, the F0 contours of the two falling tones were incompletely neutralized for both young and middle-aged speakers. Lexical frequency showed little effect on the incomplete tonal neutralization; there were significant differences in the turning point of the two falling tones in syllables with both high and low lexical frequency. However, homophone neighborhood density showed an effect on the incomplete neutralization between the two falling tones, reflected in significant differences in the slope and turning point of the F0 velocity profiles between the two tones carried by syllables with low density but not with high density. Moreover, homophone neighborhood density also affected the duration, the turning point of F0 curves, and velocity profiles of the T1- and T4-syllables. These results are discussed with consideration of social phonetic variations, the theory of Hypo- and Hyper-articulation (H&H), the Neighborhood Activation Model, and communication-based information-theoretic accounts. Collectively, these results broaden our understanding of the effects that lexical properties have on the acoustic details of lexical tone production and tonal sound changes.

Encoding category-level and context-specific phonological information at different stages: An EEG study of Mandarin third-tone sandhi word production.

Pronunciation of words or morphemes may vary systematically in different phonological contexts, but it remains unclear how different levels of phonological information are encoded in speech production. In this study, we investigated the online planning process of Mandarin Tone 3 (T3) sandhi, a case of phonological alternation whereby a low-dipping tone (T3) changes to a Tone 2 (T2)-like rising tone when followed by another T3. To examine the time course of the encoding of the abstract category-level (underlying form) and context-specific phonological form (surface form) of T3, we conducted an electroencephalographic (EEG) study with a phonologically-primed picture naming task and examined the event-related potentials (ERPs) time-locked to the stimulus onset as well as speech response onset. The behavioral results showed that targets primed by T3 or T2 primes yielded shorter naming latencies than those primed by control primes. Importantly, the EEG data revealed that T3 primes elicited larger positive amplitude over broad frontocentral regions roughly in the 320-550 ms time window of stimulus-locked ERP and -500 to -400 ms time window of response-locked ERP, whereas T2 primes elicited larger negative amplitude over left frontocentral regions roughly in the -240 to -100 ms time window of response-locked ERP. These results indicate that the underlying and the surface form are encoded at different processing stages. The former presumably occurs in the earlier phonological encoding stage, while the latter probably occurs in the later phonetic encoding or motor preparation stage. The current study offers important implications for understanding the processing of phonological alternations and tonal encoding in Chinese word production.

The shift in sensory eye dominance from short-term monocular deprivation exhibits no dependence on test spatial frequency.

BACKGROUND: Studies have shown that short-term monocular deprivation induces a shift in sensory eye dominance in favor of the deprived eye. Yet, how short-term monocular deprivation modulates sensory eye dominance across spatial frequency is not clear. To address this issue, we conducted a study to investigate the dependence of short-term monocular deprivation effect on test spatial frequency. METHODS: Ten healthy young adults (age: 24.7 ± 1.7 years, four males) with normal vision participated. We deprived their dominant eye with a translucent patch for 2.5 h. The interocular contrast ratio (dominant eye/non-dominant eye, i.e., the balance point [BP]), which indicates the contribution that the two eyes make to binocular combination, was measured using a binocular orientation combination task. We assessed if BPs at 0.5, 4 or 6 cycles/degree (c/d) change as a result of monocular deprivation. Different test spatial frequency conditions were conducted on three separate days in a random fashion. RESULTS: We compared the BPs at 0.5, 4 and 6 c/d before and after monocular deprivation. The BPs were found to be significantly affected by deprivation, where sensory eye dominance shift to the deprived eye (F1.86, 16.76 = 33.09, P < 0.001). The changes of BP were consistent at 0.5, 4, and 6 c/d spatial frequencies (F2,18 = 0.15, P = 0.57). CONCLUSION: The sensory eye dominance plasticity induced by short-term deprivation is not dependent on test spatial frequency, suggesting it could provide a practical solution for amblyopic therapy that was concerned with the binocular outcome.

Issues Revisited: Shifts in Binocular Balance Depend on the Deprivation Duration in Normal and Amblyopic Adults.

INTRODUCTION: Recent studies indicate that short-term monocular deprivation increases the deprived eye's contribution to binocular fusion in both adults with normal vision and amblyopia. In this study, we investigated whether the changes in visual plasticity depended on the duration of deprivation in normal and amblyopic adults. METHODS: Twelve anisometropia amblyopic observers (aged 24.8 ± 2.3 years) and 12 age-matched normal observers (aged 23.9 ± 1.2 years) participated in the study. The non-dominant eye of normal observers or amblyopic eye of amblyopic observers was deprived for 30, 120, and 300 min in a randomized order. Their eye balance was measured with a phase combination task, which is a psychophysical test, before and after the deprivation. This design enabled us to measure changes induced in binocular balance as an index visual plasticity due to monocular deprivations. RESULTS: By comparing the ocular dominance changes as a result of monocular deprivation with different deprivation durations, we found evidence that the ocular dominance changes are slightly larger after longer deprivations in both normal and amblyopic observers, albeit with a statistical significance. The changes from 120-min were significantly greater than those from 30-min deprivation in both groups. The magnitude of changes in sensory eye balance was significantly larger in normal observers than that in the amblyopic observers; however, the longevity of changes in visual plasticity was found to be more long-lasting in amblyopic observers than the normal counterparts. CONCLUSIONS: The duration of deprivation matters in both normal and amblyopic observers. Ocular dominance imbalance that is typically observed in amblyopia can be more ameliorated with a longer duration of deprivation.

Perception of Different Tone Contrasts at Sub-Lexical and Lexical Levels by Dutch Learners of Mandarin Chinese.

This study explores the difficulties in distinguishing different lexical tone contrasts at both sub-lexical and lexical levels for beginning and advanced Dutch learners of Mandarin, using a sequence-recall task and an auditory lexical decision task. In both tasks, the Tone 2-Tone 3 contrast is most prone to errors for both groups of learners. A significant improvement in the advanced group was found for this tone contrast in the sub-lexical sequence recall task, but not in the lexical decision task. This is taken as evidence that utilizing tones in on-line spoken word recognition is more complex and demanding for L2 learners than in a memory-based task. The results of the lexical decision task also revealed that advanced learners have developed a stronger sensitivity to Tone 1 compared to the other three tones, with Tone 4 showing the least sensitivity. These findings suggest different levels of robustness and distinctiveness for the representation of different lexical tones in L2 learners' lexicon and consequently different levels of proficiency in integrating tones for lexical processing. The observed patterns of difficulty are potentially related to the acoustic characteristics of different lexical tone contrasts as well as to the interference of the suprasegmental features of learner's native language (i.e., the tonal contrasts of Dutch intonation) on the acquisition of the Mandarin lexical tone contrasts.

Music training is associated with better clause segmentation during spoken language processing.

Musical expertise is known to affect speech perception at units below clause/sentence. This study investigated whether the musician's advantage extends to a higher and more central level of speech processing (i.e., clause segmentation). Two groups of participants (musician vs. nonmusician) were presented with sentences that contain an internal clause boundary. The acoustic correlates of the boundary were manipulated in six conditions: all-cue, pause-only, final-lengthening-only, pitch-reset-only, pause-and-final-lengthening-in-combination, and no-cue conditions. Participants were asked to judge whether the sentence they heard had an internal boundary. Results showed that the musicians detected more boundaries than the nonmusicians in the all-cue and the pause-only conditions, but fewer boundaries in the no-cue condition. Further analyses of cue weight showed that both musicians and nonmusicians placed more importance on pause than the other two cues, but this weighting bias was more pronounced for the musicians. These results suggest that music training is associated with increased perceptual acuity not only to the acoustic markings of speech boundaries but also to the weighting of the cues. Our findings extend the role of musical expertise to sentence-level speech processing.

A Joint Lateral Motion-Stereo Constraint.

Purpose: We developed a stereo task that is based on a motion direction discrimination to examine the role that depth can play in disambiguating motion direction. Methods: In this study, we quantified normal adults' static and dynamic (i.e., laterally moving) stereoscopic performance using a psychophysical task, where we dichoptically presented randomly arranged, limited lifetime Gabor elements at two depth planes (one plane was at the fixation plane and the other at an uncrossed disparity relative to the fixation plane). Each plane contained half of the elements. For the dynamic condition, all elements were vertically oriented and moved to the left in one plane and to the right in another plane; for the static condition, the elements were horizontally oriented in one plane and vertically oriented in another plane. Results: For the range of motion speed that we measured (from 0.17°/s to 5.33°/s), we observed clear speed tuning of the stereo sensitivity (P = 3.0 × 10-5). The shape of this tuning did not significantly change with different spatial frequencies. We also found a significant difference in stereo sensitivity between stereopsis with static and laterally moving stimuli (speed = 0.67°/s; P = 0.004). Such difference was not evident when we matched the task between the static and moving stimuli. Conclusions: We report that lateral motion modulates human global depth perception. This motion/stereo constraint is related to motion velocity not stimulus temporal frequency. We speculate that the processing of motion-based stereopsis of the kind reported here occurs in dorsal extrastriate cortex.

Context Matters for Tone and Intonation Processing in Mandarin.

In tonal languages such as Mandarin, both lexical tone and sentence intonation are primarily signaled by F0. Their F0 encodings are sometimes in conflict and sometimes in congruency. The present study investigated how tone and intonation, with F0 encodings in conflict or in congruency, are processed and how semantic context may affect their processing. To this end, tone and intonation identification experiments were conducted in both semantically neutral and constraining contexts. Results showed that the overall performance of tone identification was better than that of intonation. Specifically, tone identification was seldom affected by intonation information irrespective of semantic contexts. However, intonation identification, particularly question intonation, was susceptible to the final lexical tone identity and affected by the semantic context. In the semantically neutral context, questions ending with a rising tone and a falling tone were equally difficult to identify. In the semantically constraining context, questions ending with a falling tone were much better identified than those ending with a rising tone. This perceptual asymmetry suggests that top-down information provided by the semantically constraining context can play a facilitating role for listeners to disentangle intonational information from tonal information, but mainly in sentences with the lexical falling tone in the final position.

Binocular Summation Is Intact in Intermittent Exotropia After Surgery.

Purpose: To determine binocular summation of surgically treated intermittent exotropia (IXT) patients by measuring the contrast threshold. Methods: We recruited 38 surgically treated IXT patients aged 8-24 years and 20 age-matched healthy controls. All participants had normal or corrected-to-normal visual acuity (Snellen ≥ 20/20) in both eyes. The IXT patients had undergone the surgery at least a year prior to the study. Twenty-one of them obtained good alignment and 17 experienced a recurrence of exotropia. We measured the observers' monocular and binocular contrast sensitivities (CS) at six spatial frequencies (1.5, 3, 6, 12, 18, 24 cycles/degree) as an index of visual information processing at the threshold level. Binocular summation was evaluated against a baseline model of simple probability summation based on the CS at each spatial frequency and the area under the log contrast sensitivity function (AULCSF). Results: The exo-deviation of IXTs with good alignment was -6.38 ± 3.61 prism diopters (pd) at 33 cm and -5.14 ± 4.07 pd at 5 m. For the patients with recurrence, it was -23.47 ± 5.53 pd and -21.12 ± 4.28 pd, respectively. There was no significant difference in the binocular summation ratio (BSR) between the surgically treated IXT patients, including those with good alignment and recurrence, and normal controls at each spatial frequency [F (2,55) = 0.416, P = 0.662] and AULCSF [F (2,55) = 0.469, P = 0.628]. In addition, the BSR was not associated with stereopsis (r = -0.151, P = 0.365). Conclusion: Our findings of normal contrast sensitivity binocular summation ratio in IXT after surgical treatment suggest that the ability of the visual cortex in processing binocular information is intact at the contrast threshold level.

Can Short-Term Ocular Dominance Plasticity Provide a General Index to Visual Plasticity to Personalize Treatment in Amblyopia?

PURPOSE: Recently, Lunghi et al. (2016) showed that amblyopic eye's visual acuity per se after 2 months of occlusion therapy could be predicted by a homeostatic plasticity, that is, the temporary shift of perceptual eye dominance observed after a 2-h monocular deprivation, in children with anisometropic amblyopia. In this study, we assess whether the visual acuity improvement of the amblyopic eye measured after 2 months of occlusion therapy could be predicted by this plasticity. METHODS: Seven children (6.86 ± 1.46 years old; SD) with anisometropic amblyopia participated in this study. All patients were newly diagnosed and had no treatment history before participating in our study. They finished 2 months of refractive adaptation and then received a 4-h daily fellow eye patching therapy with an opaque patch for a 2-month period. Best-corrected visual acuity of the amblyopic eye was measured before and after the patching therapy. The homeostatic plasticity was assessed by measuring the temporary shift of perceptual eye dominance from 2-h occlusion of the amblyopic eye before treatment. A binocular phase combination paradigm was used for this study. RESULTS: We found that there was no significant correlation between the temporary shift of perceptual eye dominance observed after 2-h occlusion of the amblyopic eye and the improvement in visual acuity in the amblyopic eye from 2 months of classical patching therapy. This result, although in disagreements with the conclusions of Lunghi et al. involving the short-term patching of the amblyopic eye, is in fact consistent with a reanalysis of Lunghi and colleagues' data. CONCLUSION: The short-term changes in perceptual eye dominance as a result of short-term monocular deprivation do not provide an index of cortical plasticity in the general sense such that they are able to predict acuity outcomes from longer-term classical patching.

Tonal split and laryngeal contrast of onset consonant in Lili Wu Chinese.

This study examines the acoustic properties concerning tonal split and stop onsets in an under-documented Wu Chinese variety, Lili Wu, using speech production data collected from field research. Lili Wu Chinese has been reported to demonstrate an unusual tonal split phenomenon known as "aspiration-induced tonal split" (ATS). ATS refers to the distinct lowering of f0 of a lexical tone over syllables beginning with a voiceless aspirated obstruent, compared to that of syllables beginning with an unaspirated obstruent. Two debates lingering in the existing literature are discussed: (i) is ATS an on-going change or a completed change? and (ii) is it onset aspiration or vowel breathiness that directly triggers ATS? Results suggest that ATS is a completed change, which, however, is conditioned by tonal contexts. Regarding the second debate, results suggest that neither aspiration nor breathiness serves as the direct trigger for tonal split. Moreover, one unexpected on-going sound change was observed: The breathiness of vowels after voiced onsets seems to be disappearing among the younger generation. These findings extend the understanding of the acoustic properties of tonal development in a complex system and highlight the importance of experimental methods in understanding the sound structure and changes of under-documented languages.

Tonal mapping of Xi'an Mandarin and Standard Chinese.

One long-neglected fact in linguistic research on Standard Chinese (SC) is that most speakers of SC also speak a local dialect, which may share phonological features with SC. Tonal information can be a determinant of the phonological similarities or differences between some Chinese dialects and SC, yet relatively little empirical research has been conducted on the tonal system of other language varieties in Chinese aside from SC. Among these dialects, Xi'an Mandarin (XM) is particularly interesting for the seemingly simple, yet intricate mapping between its lexical tones with those in SC. In this study, the tonal systems of XM and SC were compared empirically. Tones with similar contours from XM and SC were paired, and both tone production and perception experiments were carried out on bidialectal speakers of XM and SC. The two experiments together showed that there is indeed systematic mapping of tones between XM and SC. The degree of similarity of the mapped tone pair in tone perception was largely dependent on the acoustic phonetic similarity between the tones in tone production, with a phonological rule playing a role in the tone pair of low contour.

Short-Term Deprivation Does Not Influence Monocular or Dichoptic Temporal Synchrony at Low Temporal Frequency.

Studies on binocular combination and rivalry show that short-term deprivation strengthens the contribution of the deprived eye in binocular vision. However, whether short-term monocular deprivation affects temporal processing per se is not clear. To address this issue, we conducted a study to investigate the effect of monocular deprivation on dichoptic temporal synchrony. We tested ten adults with normal vision and patched their dominant eye with an opaque patch for 2.5 h. A temporal synchrony paradigm was used to measure if temporal synchrony thresholds change as a result of monocular pattern deprivation. In this paradigm, we displayed two pairs of Gaussian blobs flickering at 1 Hz with either the same or different phased- temporal modulation. In Experiment 1, we obtained the thresholds for detecting temporal asynchrony under dichoptic viewing configurations. We compared the thresholds for temporal synchrony between before and after monocular deprivation and found no significant changes of the interocular synchrony. In Experiment 2, we measured the monocular thresholds for detecting temporal asynchrony. We also found no significant changes of the monocular synchrony of either the patched eye or the unpatched eye. Our findings suggest that short-term monocular deprivation induced-plasticity does not influence monocular or dichoptic temporal synchrony at low temporal frequency.

Action Video Gaming Does Not Influence Short-Term Ocular Dominance Plasticity in Visually Normal Adults.

Action video gaming can promote neural plasticity. Short-term monocular patching drives neural plasticity in the visual system of human adults. For instance, short-term monocular patching of 0.5-5 h briefly enhances the patched eye's contribution in binocular vision (i.e., short-term ocular dominance plasticity). In this study, we investigate whether action video gaming can influence this plasticity in adults with normal vision. We measured participants' eye dominance using a binocular phase combination task before and after 2.5 h of monocular patching. Participants were asked to play action video games, watch action video game movies, or play non-action video games during the period of monocular patching. We found that participants' change of ocular dominance after monocular patching was not significantly different either for playing action video games versus watching action video game movies (Comparison 1) or for playing action video games versus playing non-action video games (Comparison 2). These results suggest that action video gaming does not either boost or eliminate short-term ocular dominance plasticity, and that the neural site for this type of plasticity might be in the early visual pathway.

Abnormal Monocular and Dichoptic Temporal Synchrony in Adults with Amblyopia.

Purpose: We investigate temporal synchrony within one eye and between both eyes in adults with amblyopia. Methods: Eight adult amblyopes (range, 19.88-27.81 years old; median, 22.86 years old) and 12 age-matched adults with normal vision (range, 21.2-50.30 years old; median, 23.78 years old) participated in the experiment. We showed two pairs of Gaussian blobs flickering at 1 Hz as visual stimuli, one pair with the same temporal phase modulation (i.e., the reference) and another pair with a distinct temporal phase (i.e., the signal). We employed the constant stimuli method to measure the minimum degree of temporal phase (temporal synchrony threshold), at which participants were able to discriminate the signal pair under binocular, monocular, and dichoptic viewing configurations. Results: The temporal synchrony threshold was different across the six configurations (P = 0.001). There was also an interaction between the configuration and the group (P = 0.004). The synchrony threshold was significantly higher in amblyopes than in controls under the configurations where two pairs of blobs were presented to the amblyopic eye (136.52 ± 50.19 vs. 97.08 ± 22.02 ms, P = 0.027) and where the paired blobs were presented to different eyes (163.15 ± 80.85 vs. 111.61 ± 22.46 ms, P = 0.049). The visual deficits in these two configurations were significantly correlated (r = 0.824, P = 0.012). Conclusions: The threshold for detecting temporal asynchrony increased when the stimuli were presented only to the amblyopic eye and when they were dichoptically presented to the amblyopic and fellow eyes.

Corrigendum: The Binocular Balance at High Spatial Frequencies as Revealed by the Binocular Orientation Combination Task.

[This corrects the article DOI: 10.3389/fnhum.2019.00106.].