Attention and the right-ear advantage: What is the connection?

Top-down modulation of dichotic listening affects interhemispheric connectivity: an electroencephalography study

Introduction

Dichotic listening (DL) has been extensively used as a task to investigate auditory processing and hemispheric lateralisation in humans. According to the "callosal relay model," the typical finding of a right ear advantage (REA) occurs because the information coming from the right ear has direct access to the left dominant hemisphere while the information coming from the left ear has to cross via the corpus callosum. The underlying neuroanatomical correlates and neurophysiological mechanisms have been described using diffusion tensor imaging (DTI) and lagged phase synchronization (LPS) of the interhemispheric auditory pathway. During the non-forced condition of DL, functional connectivity (LPS) of interhemispheric gamma-band coupling has been described as a relevant mechanism related to auditory perception in DL. In this study, we aimed to extend the previous results by exploring the effects of top-down modulation of DL (forced-attention condition) on interhemispheric gamma-band LPS.

Methods

Right-handed healthy participants (n = 31; 17 females) performed three blocks of DL with different attention instructions (no-attention, left-ear attention, right-ear attention) during simultaneous EEG recording with 64 channels. Source analysis was done with exact low-resolution brain electromagnetic tomography (eLORETA) and functional connectivity between bilateral auditory areas was assessed as LPS in the gamma-band frequency range.

Results

Twenty-four participants (77%) exhibited a right-ear advantage in the no-attention block. The left- and right-attention conditions significantly decreased and increased right-ear reports, respectively. Similar to the previous studies, functional connectivity analysis (gamma-band LPS) showed significantly increased connectivity between left and right Brodmann areas (BAs) 41 and 42 during left ear reports in contrast with right ear reports. Our new findings notably indicated that the right-attention condition exhibited significantly higher connectivity between BAs 42 compared with the no-attention condition. This enhancement of connectivity was more pronounced during the perception of right ear reports.

Discussion

Our results are in line with previous reports describing gamma-band synchronization as a relevant neurophysiological mechanism involved in the interhemispheric connectivity according to the callosal relay model. Moreover, we newly added some evidence of attentional effects on this interhemispheric connectivity, consistent with the attention-executive model. Our results suggest that reciprocal inhibition could be involved in hemispheric lateralization processes.

Dichotic listening and interhemispheric integration after callosotomy: A systematic review

The right-ear advantage (REA) for recalling dichotically presented auditory-verbal stimuli has been traditionally linked to the dominance of the left cerebral hemisphere for speech processing. Early studies on patients with callosotomy additionally found that the removal of the corpus callosum leads to a complete extinction of the left ear, and consequently the today widely used models to explain the REA assume a central role of callosal axons for recalling the left-ear stimulus in dichotic listening. However, later dichotic-listening studies on callosotomy patients challenge this interpretation, as many patients appear to be able to recall left-ear stimuli well above chance level, albeit with reduced accuracy. The aim of the present systematic review was to identify possible experimental and patient variables that explain the inconsistences found regarding the effect of split-brain surgery on dichotic listening. For this purpose, a systematic literature search was conducted (databases: Pubmed, Web of Knowledge, EBSChost, and Ovid) to identify all empirical studies on patients with surgical section of the corpus callosum (complete or partial) that used a verbal dichotic-listening paradigm. This search yielded ks = 32 publications reporting patient data either on case or group level, and the data was analysed by comparing the case-level incidence of left-ear suppression, left-ear extinction, and right-ear enhancement narratively or statistically considering possible moderator variables (i.a., extent of the callosal surgery, stimulus material, response format, selective attention). The main finding was an increased incidence of left-ear suppression (odds ratio = 7.47, CI95%: [1.21; 83.49], exact p = .02) and right-ear enhancement (odds ratio = 21.61, CI95%: [4.40; 154.11], p < .01) when rhyming as compared with non-rhyming stimuli were used. Also, an increase in left-ear reports was apparent when a response by the right hemisphere was allowed (i.e., response with the left hand). While the present review is limited by the overall small number of cases and a lack of an appropriate control sample in most of the original studies, the findings nevertheless suggest an adjustment of the classical dichotic-listening models incorporating right-hemispheric processing abilities as well as the perceptual competition of the left- and right-ear stimuli for attention.

Behavioral and Cortical Activation Changes in Children Following Auditory Training for Dichotic Deficits

We report changes following auditory rehabilitation for interaural asymmetry (ARIA) training in behavioral test performance and cortical activation in children identified with dichotic listening deficits. In a one group pretest-posttest design, measures of dichotic listening, speech perception in noise, and frequency pattern identification were assessed before and 3 to 4.5 months after completing an auditory training protocol designed to improve binaural processing of verbal material. Functional MRI scans were also acquired before and after treatment while participants passively listened in silence or to diotic or dichotic digits. Significant improvements occurred after ARIA training for dichotic listening and speech-in-noise tests. Post-ARIA, fMRI activation increased during diotic tasks in anterior cingulate and medial prefrontal regions and during dichotic tasks, decreased in the left precentral gyrus, right-hemisphere pars triangularis, and right dorsolateral and ventral prefrontal cortices, regions known to be engaged in phonologic processing and working memory. The results suggest that children with dichotic deficits may benefit from the ARIA program because of reorganization of cortical capacity required for listening and a reduced need for higher-order, top-down processing skills when listening to dichotic presentations.

The effect of voice familiarity on attention to speech in a cocktail party scenario

Selective attention to one speaker in multi-talker environments can be affected by the acoustic and semantic properties of speech. One highly ecological feature of speech that has the potential to assist in selective attention is voice familiarity. Here, we tested how voice familiarity interacts with selective attention by measuring the neural speech-tracking response to both target and non-target speech in a dichotic listening "Cocktail Party" paradigm. We measured Magnetoencephalography from n = 33 participants, presented with concurrent narratives in two different voices, and instructed to pay attention to one ear ("target") and ignore the other ("non-target"). Participants were familiarized with one of the voices during the week prior to the experiment, rendering this voice familiar to them. Using multivariate speech-tracking analysis we estimated the neural responses to both stimuli and replicate their well-established modulation by selective attention. Importantly, speech-tracking was also affected by voice familiarity, showing enhanced response for target speech and reduced response for non-target speech in the contra-lateral hemisphere, when these were in a familiar vs. an unfamiliar voice. These findings offer valuable insight into how voice familiarity, and by extension, auditory-semantics, interact with goal-driven attention, and facilitate perceptual organization and speech processing in noisy environments.

Review of Binaural Processing With Asymmetrical Hearing Outcomes in Patients With Bilateral Cochlear Implants

Bilateral cochlear implants (BiCIs) result in several benefits, including improvements in speech understanding in noise and sound source localization. However, the benefit bilateral implants provide among recipients varies considerably across individuals. Here we consider one of the reasons for this variability: difference in hearing function between the two ears, that is, interaural asymmetry. Thus far, investigations of interaural asymmetry have been highly specialized within various research areas. The goal of this review is to integrate these studies in one place, motivating future research in the area of interaural asymmetry. We first consider bottom-up processing, where binaural cues are represented using excitation-inhibition of signals from the left ear and right ear, varying with the location of the sound in space, and represented by the lateral superior olive in the auditory brainstem. We then consider top-down processing via predictive coding, which assumes that perception stems from expectations based on context and prior sensory experience, represented by cascading series of cortical circuits. An internal, perceptual model is maintained and updated in light of incoming sensory input. Together, we hope that this amalgamation of physiological, behavioral, and modeling studies will help bridge gaps in the field of binaural hearing and promote a clearer understanding of the implications of interaural asymmetry for future research on optimal patient interventions.

The Right-Ear Advantage in Static and Dynamic Cocktail-Party Situations

When presenting two competing speech stimuli, one to each ear, a right-ear advantage (REA) can often be observed, reflected in better speech recognition compared to the left ear. Considering the left-hemispheric dominance for language, the REA has been explained by superior contralateral pathways (structural models) and language-induced shifts of attention to the right (attentional models). There is some evidence that the REA becomes more pronounced, as cognitive load increases. Hence, it is interesting to investigate the REA in static (constant target talker) and dynamic (target changing pseudo-randomly) cocktail-party situations, as the latter is associated with a higher cognitive load than the former. Furthermore, previous research suggests an increasing REA, when listening becomes more perceptually challenging. The present study examined the REA by using virtual acoustics to simulate static and dynamic cocktail-party situations, with three spatially separated talkers uttering concurrent matrix sentences. Sentences were presented at low sound pressure levels or processed with a noise vocoder to increase perceptual load. Sixteen young normal-hearing adults participated in the study. The REA was assessed by means of word recognition scores and a detailed error analysis. Word recognition revealed a greater REA for the dynamic than for the static situations, compatible with the view that an increase in cognitive load results in a heightened REA. Also, the REA depended on the type of perceptual load, as indicated by a higher REA associated with vocoded compared to low-level stimuli. The results of the error analysis support both structural and attentional models of the REA.

Atypical function of auditory sensory gating in children with developmental dyslexia: Investigating its relationship with cognitive abilities

Impairments of auditory processing are among frequent findings in dyslexia. However, it is unclear how auditory signals are gated from brainstem to higher central processing stages in these individuals. The present study was done to investigate auditory sensory gating in children with developmental dyslexia (DD), and to determine whether sensory gating correlates with performance on behavioural tasks. Auditory sensory gating at P50, N1 and P2 waves was evaluated in two groups including 20 children with DD and 19 children with typical reading development (TRD). Behavioural tests were used to evaluate phonological working memory (PWM) and selective attention abilities. Sensory gating in children with DD was significantly less efficient than their peers at P50, N1 and P2 waves. Lower auditory evoked potential (AEP) amplitudes were found in the DD group. The children with TRD scored better in all the behavioural tests. Relationships were reported between sensory gating at P50, N1, P2 and behavioural performance in the two groups. Children with dyslexia had deficient sensory gating in comparison with controls. In addition, children with dyslexia experienced problems with PWM and selective attention tasks. The function of sensory gating was associated with attentional and PWM performances in this group.

Dichotic-listening performance after complete callosotomy: No relief from left-ear extinction by selective attention

The surgical section of the corpus callosum (callosotomy) has been frequently demonstrated to result in a left-ear extinction in dichotic listening. That is, callosotomy patients report the left-ear stimulus below chance level, resulting in substantially enhanced right-ear advantage (REA) compared with controls. A small number of previous studies also suggest that callosotomy patients can overcome left-ear extinction when the instruction encourages to attend selectively to the left-ear stimulus. In the present case study, we re-examine the role of selective attention in dichotic listening in two patients with complete callosotomy and 40 age- and sex-matched controls. We used the standardised Bergen dichotic-listening paradigm which uses stop-consonant-vowel syllables as stimulus material and includes both a free-report and selective-attention condition. As was predicted, both patients showed a clear left-ear extinction. However, contrasting the earlier reports, we did not find any evidence for a relief from this extinction by selectively attending to the left-ear stimulus. We conclude that previous demonstrations of an attention-improved left-ear recall in callosotomy patients may be attributed to the use of suboptimal dichotic paradigms or residual callosal connectivity, rather than representing a genuine effect of attention.

Dichotic Sentences Test Performance of Adults with communication complaints

PURPOSE

To analyze the performance of normal-hearing adults with communication complaints in the Dichotic Sentences Test.

METHODS

We selected from the database 15 normal-hearing participants with normal results in the Digits Dichotic Test, aged between 19 and 44 years, right-handed, who reported communicative complaints. The Dichotic Sentences Test was applied using two protocols consisting of four different combinations of lists called sequences 1 and 2, in the following order: training, divided attention step, right and left directed attention steps.

RESULTS

In the first application sequence, the average performance in the divided attention step was 84.7% for the right ear and 60.67% for the left, with statistical difference between ears. The asymmetry between ears varied from -50% to 60%. In the directed attention step, the average performance was 99.33% for the right ear and 98% for the left, with no statistical difference. In the second application sequence, there was a tendency for better results, more pronounced for the left ear, with no statistical significance, with the performance variation and asymmetry between ears remaining high. In the comparison between the sequences, in the divided attention step, it was found that, for the right ear, 40% of the individuals did not vary, 33% performed worse, and 26.7% performed better; for the left ear, 6.6% did not vary, 20% performed worse, and 73.33% performed better. There was result stability in the directed attention step.

CONCLUSION

The normal-hearing adults with communication complaints presented a heterogeneous profile, especially in the divided attention step, with a marked difference between ears and response variability.

Investigating the lateralisation of experimentally induced auditory verbal hallucinations

Introduction

Auditory verbal hallucinations (AVHs), or hearing non-existent voices, are a common symptom in psychosis. Recent research suggests that AVHs are also experienced by neurotypical individuals. Individuals with schizophrenia experiencing AVHs and neurotypicals who are highly prone to hallucinate both produce false positive responses in auditory signal detection. These findings suggest that voice-hearing may lie on a continuum with similar mechanisms underlying AVHs in both populations.

Methods

The current study used a monaural auditory stimulus in a signal detection task to test to what extent experimentally induced verbal hallucinations are (1) left-lateralised (i.e., more likely to occur when presented to the right ear compared to the left ear due to the left-hemisphere dominance for language processing), and (2) predicted by self-reported hallucination proneness and auditory imagery tendencies. In a conditioning task, fifty neurotypical participants associated a negative word on-screen with the same word being played via headphones through successive simultaneous audio-visual presentations. A signal detection task followed where participants were presented with a target word on-screen and indicated whether they heard the word being played concurrently amongst white noise.

Results

Results showed that Pavlovian audio-visual conditioning reliably elicited a significant number of false positives (FPs). However, FP rates, perceptual sensitivities, and response biases did not differ between either ear. They were neither predicted by hallucination proneness nor auditory imagery.

Discussion

The results show that experimentally induced FPs in neurotypicals are not left-lateralised, adding further weight to the argument that lateralisation may not be a defining feature of hallucinations in clinical or non-clinical populations. The findings also support the idea that AVHs may be a continuous phenomenon that varies in severity and frequency across the population. Studying induced AVHs in neurotypicals may help identify the underlying cognitive and neural mechanisms contributing to AVHs in individuals with psychotic disorders.

Selective spatial attention in lateralized multi-talker speech perception: EEG correlates and the role of age

Speech comprehension under dynamic cocktail party conditions requires auditory search for relevant speech content and focusing spatial attention on the target talker. Here, we investigated the development of these cognitive processes in a population of 329 participants aged 20-70 years. We used a multi-talker speech detection and perception task in which pairs of words (each consisting of a cue and a target word) were simultaneously presented from lateralized positions. Participants attended to predefined cue words and responded to the corresponding target. Task difficulty was varied by presenting cue and target stimuli at different intensity levels. Decline in performance was observed only in the oldest group (age range 53-70 years) and only in the most difficult condition. The EEG analysis of neurocognitive correlates of lateralized auditory attention and stimulus evaluation (N2ac, LPCpc, alpha power lateralization) revealed age-associated changes in focussing on and processing of task-relevant information, while no such deficits were found on early auditory search and target segregation. Irrespective of age, more challenging listening conditions were associated with an increased allocation of attentional resources.

Interaural asymmetry of dynamic range: Abnormal fusion, bilateral interference, and shifts in attention

Speech information in the better ear interferes with the poorer ear in patients with bilateral cochlear implants (BiCIs) who have large asymmetries in speech intelligibility between ears. The goal of the present study was to assess how each ear impacts, and whether one dominates, speech perception using simulated CI processing in older and younger normal-hearing (ONH and YNH) listeners. Dynamic range (DR) was manipulated symmetrically or asymmetrically across spectral bands in a vocoder. We hypothesized that if abnormal integration of speech information occurs with asymmetrical speech understanding, listeners would demonstrate an atypical preference in accuracy when reporting speech presented to the better ear and fusion of speech between the ears (i.e., an increased number of one-word responses when two words were presented). Results from three speech conditions showed that: (1) When the same word was presented to both ears, speech identification accuracy decreased if one or both ears decreased in DR, but listeners usually reported hearing one word. (2) When two words with different vowels were presented to both ears, speech identification accuracy and percentage of two-word responses decreased consistently as DR decreased in one or both ears. (3) When two rhyming words (e.g., bed and led) previously shown to phonologically fuse between ears (e.g., bled) were presented, listeners instead demonstrated interference as DR decreased. The word responded in (2) and (3) came from the right (symmetric) or better (asymmetric) ear, especially in (3) and for ONH listeners in (2). These results suggest that the ear with poorer dynamic range is downweighted by the auditory system, resulting in abnormal fusion and interference, especially for older listeners.

Defining attention from an auditory perspective

Attention prioritizes certain information at the expense of other information in ways that are similar across vision, audition, and other sensory modalities. It influences how-and even what-information is represented and processed, affecting brain activity at every level. Much of the core research into cognitive and neural mechanisms of attention has used visual tasks. However, the same top-down, object-based, and bottom-up attentional processes shape auditory perception, largely through the same underlying, cognitive networks. This article is categorized under: Psychology > Attention.

Analysis of the auditory processing skills in 1,012 children aged 6–9 confirms the adequacy of APD testing in 6-year-olds

The aim of the study was to assess the validity of the use of the battery of tests assessing higher auditory functions in the diagnostic process of APD in 6-year-old children. The study involved 1,012 Polish-speaking children aged 6 to 9 years with normal hearing sensitivity. The evaluation of auditory functions was performed using the ATS Neuroflow test battery comprising: Adaptive Speech in Noise test (ASPN-S), Dichotic Digits Test (DDT) and Frequency Pattern Test (FPT). Two groups were distinguished: the group”S” (Study) containing 880 participants with APD (participants who obtained abnormal results in at least two tests) and the group”C” (Control) including 132 participants without APD. The results obtained by 6-year-old children in behavioral tests present a similar disorder’s profile to those of older children in terms of the prevalence of specific deficits and their severity. Performance in the APD tests of healthy 6-year-old children is higher than 9-year-old children with APD, despite the process of physiological development of hearing functions in older children. The test assessing understanding speech in noise was the most frequently impaired among all examined, while the dichotic listening with distracted attention was the least frequently impaired function. The deficit found in DDT was opposite between patients with APD and healthy children, we called the detected phenomenon the reversed lateralization pattern. The use of DDT, FPT and ASPN-S tests to evaluate higher auditory functions in the process of diagnosing APD in 6-year-old children is justified by the lack of discrepancy in the disorder profile of 6-year-old children in comparison with older children, both in the healthy population, and in children with impaired auditory function development. Early diagnosis can be beneficial for accurate programming of therapeutic goals.

Ear Asymmetry and Contextual Influences on Speech Perception in Hearing-Impaired Patients

The left hemisphere preference for verbal stimuli is well known, with a right ear (RE) advantage obtained when competing verbal stimuli are presented simultaneously, at comfortable intensities, to both ears. Speech perception involves not only the processing of acoustic peripheral information but also top–down contextual influences, filling the gaps in the incoming information that is particularly degraded in hearing-impaired individuals. This study aimed to analyze the potential asymmetry of those contextual influences on a simple speech perception task in hearing-impaired patients in light of hemispheric asymmetry. Contextual influences on disyllabic word perception scores of 60 hearing-impaired patients were compared between left ear (LE) and RE, in a balanced design, involving two repetitions of the same task. Results showed a significantly greater contextual influence on the RE versus the LE and, for the second repetition versus the first one, without any interaction between the two. Furthermore, the difference in contextual influences between RE and LE increased significantly with the RE advantage measured by a dichotic listening test in the absence of any significant correlation with hearing threshold asymmetry. Lastly, the contextual influence asymmetry decreased significantly as age increased, which was mainly due to a greater increase, with age, of contextual influences on the LE versus the RE. Those results agree with the literature reporting a relative right-shift of hemispheric asymmetry observed with age in speech in noise perception tasks in normal hearing subjects and the clinical reports of generally better audiometric speech scores obtained in RE versus LE.

Combined fMRI Region- and Network-Analysis Reveal New Insights of Top-Down Modulation of Bottom-Up Processes in Auditory Laterality

Dichotic listening along with the right-ear advantage (REA) has been a standard method of investigating auditory laterality ever since it was first introduced into neuropsychology in the early 1960s. Beginning in the 1980s, authors reported that it was possible to modulate the bottom-up driven perceptual REA by instructing subjects to selectively attend to and report only from the right or left ear. In the present study, we investigated neuronal correlates of both the bottom-up and top-down modulation of the REA through two fMRI analysis approaches: a traditional region approach and a network connectivity approach. Blood-Oxygenation-Level-Dependent (BOLD) fMRI data were acquired while subjects performed the standard forced-attention paradigm. We asked two questions, could the behavioral REA be replicated in unique brain markers, and second if the profound instruction-induced modulation of the REA found in behavioral data would correspond to a similar modulation of brain activation, both region- and network-specific modulations. The subjects were 70 healthy adult right-handers, about half men and half women. fMRI data were acquired in a 3T MR scanner, and the behavioral results replicated previous findings with a REA in the non-forced (NF) and forced-right (FR) conditions, and a tendency for a left-ear advantage (LEA) in the FL-condition. The fMRI data showed unique activations in the speech perception areas of the left temporal lobe when directly contrasted with activations in the homologous right side. However, there were no remaining unique activations when the FR- and FL-conditions were contrasted against each other, and with the NF-condition, using a conservative significance thresholding. The fMRI results are conceptualized within a network connectivity frame of reference, especially with reference to the extrinsic mode network (EMN). The EMN is a generalized task-positive network that is upregulated whenever the task demands exceed a certain threshold irrespective of the specifics and demands of the task. This could explain the similarity of activations for the FR- and FL-conditions, despite the clear differences in behavior.

Neurophysiological Evaluation of Right-Ear Advantage During Dichotic Listening

Right-ear advantage refers to the observation that when two different speech stimuli are simultaneously presented to both ears, listeners report stimuli more correctly from the right ear than the left. It is assumed to result from prominent projection along the auditory pathways to the contralateral hemisphere and the dominance of the left auditory cortex for the perception of speech elements. Our study aimed to investigate the role of attention in the right-ear advantage. We recorded magnetoencephalography data while participants listened to pairs of Japanese two-syllable words (namely, "/ta/ /ko/" or "/i/ /ka/"). The amplitudes of the stimuli were modulated at 35 Hz in one ear and 45 Hz in the other. Such frequency-tagging allowed the selective quantification of left and right auditory cortex responses to left and right ear stimuli. Behavioral tests confirmed the right-ear advantage, with higher accuracy for stimuli presented to the right ear than to the left. The amplitude of the auditory steady-state response was larger when attending to the stimuli compared to passive listening. We detected a correlation between the attention-related increase in the amplitude of the auditory steady-state response and the laterality index of behavioral accuracy. The right-ear advantage in the free-response dichotic listening was also found in neural activities in the left auditory cortex, suggesting that it was related to the allocation of attention to both ears.

Dichotic listening deficits in amblyaudia are characterized by aberrant neural oscillations in auditory cortex

OBJECTIVE

Children diagnosed with auditory processing disorder (APD) show deficits in processing complex sounds that are associated with difficulties in higher-order language, learning, cognitive, and communicative functions. Amblyaudia (AMB) is a subcategory of APD characterized by abnormally large ear asymmetries in dichotic listening tasks.

METHODS

Here, we examined frequency-specific neural oscillations and functional connectivity via high-density electroencephalography (EEG) in children with and without AMB during passive listening of nonspeech stimuli.

RESULTS

Time-frequency maps of these "brain rhythms" revealed stronger phase-locked beta-gamma (~35 Hz) oscillations in AMB participants within bilateral auditory cortex for sounds presented to the right ear, suggesting a hypersynchronization and imbalance of auditory neural activity. Brain-behavior correlations revealed neural asymmetries in cortical responses predicted the larger than normal right-ear advantage seen in participants with AMB. Additionally, we found weaker functional connectivity in the AMB group from right to left auditory cortex, despite their stronger neural responses overall.

CONCLUSION

Our results reveal abnormally large auditory sensory encoding and an imbalance in communication between cerebral hemispheres (ipsi- to -contralateral signaling) in AMB.

SIGNIFICANCE

These neurophysiological changes might lead to the functionally poorer behavioral capacity to integrate information between the two ears in children with AMB.

Acoustics versus linguistics? Context is Part and Parcel to lateralized processing of the parts and parcels of speech

The purpose of this review is to provide an accessible exploration of key considerations of lateralization in speech and non-speech perception using clear and defined language. From these considerations, the primary arguments for each side of the linguistics versus acoustics debate are outlined and explored in context of emerging integrative theories. This theoretical approach entails a perspective that linguistic and acoustic features differentially contribute to leftward bias, depending on the given context. Such contextual factors include stimulus parameters and variables of stimulus presentation (e.g., noise/silence and monaural/binaural) and variances in individuals (sex, handedness, age, and behavioural ability). Discussion of these factors and their interaction is also aimed towards providing an outline of variables that require consideration when developing and reviewing methodology of acoustic and linguistic processing laterality studies. Thus, there are three primary aims in the present paper: (1) to provide the reader with key theoretical perspectives from the acoustics/linguistics debate and a synthesis of the two viewpoints, (2) to highlight key caveats for generalizing findings regarding predominant models of speech laterality, and (3) to provide a practical guide for methodological control using predominant behavioural measures (i.e., gap detection and dichotic listening tasks) and/or neurophysiological measures (i.e., mismatch negativity) of speech laterality.

Defining the Role of Attention in Hierarchical Auditory Processing

Communication in noise is a complex process requiring efficient neural encoding throughout the entire auditory pathway as well as contributions from higher-order cognitive processes (i.e., attention) to extract speech cues for perception. Thus, identifying effective clinical interventions for individuals with speech-in-noise deficits relies on the disentanglement of bottom-up (sensory) and top-down (cognitive) factors to appropriately determine the area of deficit; yet, how attention may interact with early encoding of sensory inputs remains unclear. For decades, attentional theorists have attempted to address this question with cleverly designed behavioral studies, but the neural processes and interactions underlying attention's role in speech perception remain unresolved. While anatomical and electrophysiological studies have investigated the neurological structures contributing to attentional processes and revealed relevant brain-behavior relationships, recent electrophysiological techniques (i.e., simultaneous recording of brainstem and cortical responses) may provide novel insight regarding the relationship between early sensory processing and top-down attentional influences. In this article, we review relevant theories that guide our present understanding of attentional processes, discuss current electrophysiological evidence of attentional involvement in auditory processing across subcortical and cortical levels, and propose areas for future study that will inform the development of more targeted and effective clinical interventions for individuals with speech-in-noise deficits.

Action planning and affective states within the auditory peripersonal space in normal hearing and cochlear-implanted listeners

Fast reaction to approaching stimuli is vital for survival. When sounds enter the auditory peripersonal space (PPS), sounds perceived as being nearer elicit higher motor cortex activation. There is a close relationship between motor preparation and the perceptual components of sounds, particularly of highly arousing sounds. Here we compared the ability to recognize, evaluate, and react to affective stimuli entering the PPS between 20 normal-hearing (NH, 7 women) and 10 cochlear-implanted (CI, 3 women) subjects. The subjects were asked to quickly flex their arm in reaction to positive (P), negative (N), and neutral (Nu) affective sounds ending virtually at five distances from their body. Pre-motor reaction time (pm-RT) was detected via electromyography from the postural muscles to measure action anticipation at the sound-stopping distance; the sounds were also evaluated for their perceived level of valence and arousal. While both groups were able to localize sound distance, only the NH group modulated their pm-RT based on the perceived sound distance. Furthermore, when the sound carried no affective components, the pm-RT to the Nu sounds was shorter compared to the P and the N sounds for both groups. Only the NH group perceived the closer sounds as more arousing than the distant sounds, whereas both groups perceived sound valence similarly. Our findings underline the role of emotional states in action preparation and describe the perceptual components essential for prompt reaction to sounds approaching the peripersonal space.

Dichotic sentence identification test in Portuguese: a study in young adults

Introduction

Among the currently-applied auditory processing tests, dichotic listening tests have been widely used, since they allow investigating the hemispheric and inter-hemispheric function and their respective skills to process the received auditory information.

Objective

To obtain normality reference measures with the new dichotic sentence identification test in right-handed adults with normal hearing.

Methods

Quantitative, observational, cross-sectional study. 72 subjects were assessed, aged 19–44 years, right-handed, with normal hearing, without hearing complaints. The dichotic sentence identification test consists of different lists of sentences, which were combined two by two and presented at the same time, using earphones in both ears, at 50 dB Sensation Level. The test was applied in four stages: training of the 3 stages, free attention, right and left directed attention, thus evaluating different auditory skills.

Results

In the free attention task, the average percentage of correct answers in the right ear was 93.59% and in the left ear 86.06%, with a statistically significant difference between the ears, with an advantage for the right ear. In the directed attention task, the average percentage of correct answers was 99.37% in the right ear and 98.8% in the left ear, with no statistical difference between the ears.

Conclusion

It is suggested, as a normality reference for the stage of free attention, 90%–100% for correct answers for the right ear and for the left ear, from 80% to 100%. When there is asymmetry between the ears, differences of up to 20% are expected, with an advantage for the right ear For the directed attention stage, the expected normality reference values ​​are 100% for the right ear and for the left ear, with no asymmetry between the ears; however, if it occurs, a difference of 10% is expected between the ears, with an advantage for the right ear.

Divergence between functional magnetic resonance imaging and clinical indicators of language dominance in preoperative language mapping

Accurate determination of hemispheric language dominance prior to epilepsy surgery is critically important to minimize cognitive morbidity. Functional MRI (fMRI) is a noninvasive method that is highly concordant with other clinical indicators of language laterality, and is now commonly used to confirm language dominance. However, there is also a high frequency of divergence between fMRI findings and other clinical indices that complicate determination of dominance and surgical decision-making in individual patients. Despite this, divergent cases are rarely published or discussed. This article provides three illustrative examples to demonstrate common scenarios where fMRI may produce conflicting or otherwise difficult-to-interpret findings. We will also discuss potential reasons for divergence and propose a flow-chart to aid clinical decision making in such situations.

A 36-Class Bimodal ERP Brain-Computer Interface Using Location-Congruent Auditory-Tactile Stimuli

To date, traditional visual-based event-related potential brain-computer interface (ERP-BCI) systems continue to dominate the mainstream BCI research. However, these conventional BCIs are unsuitable for the individuals who have partly or completely lost their vision. Considering the poor performance of gaze independent ERP-BCIs, it is necessary to study techniques to improve the performance of these BCI systems. In this paper, we developed a novel 36-class bimodal ERP-BCI system based on tactile and auditory stimuli, in which six-virtual-direction audio files produced via head related transfer functions (HRTF) were delivered through headphones and location-congruent electro-tactile stimuli were simultaneously delivered to the corresponding position using electrodes placed on the abdomen and waist. We selected the eight best channels, trained a Bayesian linear discriminant analysis (BLDA) classifier and acquired the optimal trial number for target selection in online process. The average online information transfer rate (ITR) of the bimodal ERP-BCI reached 11.66 bit/min, improvements of 35.11% and 36.69% compared to the auditory (8.63 bit/min) and tactile approaches (8.53 bit/min), respectively. The results demonstrate the performance of the bimodal system is superior to each unimodal system. These facts indicate that the proposed bimodal system has potential utility as a gaze-independent BCI in future real-world applications.

Lateralization of Auditory Processing of Silbo Gomero

Left-hemispheric language dominance is a well-known characteristic of the human language system. However, it has been shown that leftward language lateralization decreases dramatically when people communicate using whistles. Whistled languages present a transformation of a spoken language into whistles, facilitating communication over great distances. In order to investigate the laterality of Silbo Gomero, a form of whistled Spanish, we used a vocal and a whistled dichotic listening task in a sample of 75 healthy Spanish speakers. Both individuals that were able to whistle and to understand Silbo Gomero and a non-whistling control group showed a clear right-ear advantage for vocal dichotic listening. For whistled dichotic listening, the control group did not show any hemispheric asymmetries. In contrast, the whistlers’ group showed a right-ear advantage for whistled stimuli. This right-ear advantage was, however, smaller compared to the right-ear advantage found for vocal dichotic listening. In line with a previous study on language lateralization of whistled Turkish, these findings suggest that whistled language processing is associated with a decrease in left and a relative increase in right hemispheric processing. This shows that bihemispheric processing of whistled language stimuli occurs independent of language.

Variability of the dichotic sentence test in the test and retest of normal hearing adults

PURPOSE

to investigate the variability of the Dichotic Sentence Test through the test and retest in normal-hearing adults.

METHOD

We evaluated thirty-six individuals aged 19 to 44 years old, right-handed and with normal hearing thresholds. We performed the basic audiological evaluation and then we applied the Dichotic Digit Test and Dichotic Sentence Test. The test and retest had two sessions, with an interval from 30 to 40 days, in the same shift.

RESULTS

In the integration task, there was an advantage of the right ear in both evaluation sessions. There was no significant difference between the measures obtained in the right ear in the two evaluation sessions, while in the left ear, we found a significant difference. In the analysis of the differences in ears between the test and the retest, we found that 64% of the individuals kept the same result in the right ear, while in the left one, only 36% of the individuals kept the same result in both stages and 44% showed a 10% difference between the two evaluations. We observed moderate positive correlation for both the right ear (r=0.420) and the left ear (r=0.550), with a tendency to improve retest scores. In the separation task, there was a small variability only in the left ear, also with improved retest scores.

CONCLUSION

There was a significant difference between the measures obtained in the test and retest only in the integration task in the left ear, but there was a moderate positive correlation between the measures obtained in the two evaluation sessions, showing a tendency to improve scores in the second evaluation session.

An optimal dichotic-listening paradigm for the assessment of hemispheric dominance for speech processing

Dichotic-listening paradigms are widely accepted as non-invasive tests of hemispheric dominance for language processing and represent a standard diagnostic tool for the assessment of developmental auditory and language disorders. Despite its popularity in research and clinical settings, dichotic paradigms show comparatively low reliability, significantly threatening the validity of conclusions drawn from the results. Thus, the aim of the present work was to design and evaluate a novel, highly reliable dichotic-listening paradigm for the assessment of hemispheric differences. Based on an extensive literature review, the paradigm was optimized to account for the main experimental variables which are known to systematically bias task performance or affect random error variance. The main design principle was to minimize the relevance of higher cognitive functions on task performance in order to obtain stimulus-driven laterality estimates. To this end, the key design features of the paradigm were the use of stop-consonant vowel (CV) syllables as stimulus material, a single stimulus pair per trial presentation mode, and a free recall (single) response instruction. Evaluating a verbal and manual response-format version of the paradigm in a sample of N = 50 healthy participants, we yielded test-retest intra-class correlations of rICC = .91 and .93 for the two response format versions. These excellent reliability estimates suggest that the optimal paradigm may offer an effective and efficient alternative to currently used paradigms both in research and diagnostic.

Superhuman Hearing - Virtual Prototyping of Artificial Hearing: a Case Study on Interactions and Acoustic Beamforming

Directivity and gain in microphone array systems for hearing aids or hearable devices allow users to acoustically enhance the information of a source of interest. This source is usually positioned directly in front. This feature is called acoustic beamforming. The current study aimed to improve users' interactions with beamforming via a virtual prototyping approach in immersive virtual environments (VEs). Eighteen participants took part in experimental sessions composed of a calibration procedure and a selective auditory attention voice-pairing task. Eight concurrent speakers were placed in an anechoic environment in two virtual reality (VR) scenarios. The scenarios were a purely virtual scenario and a realistic 360° audio-visual recording. Participants were asked to find an individual optimal parameterization for three different virtual beamformers: (i) head-guided, (ii) eye gaze-guided, and (iii) a novel interaction technique called dual beamformer, where head-guided is combined with an additional hand-guided beamformer. None of the participants were able to complete the task without a virtual beamformer (i.e., in normal hearing condition) due to the high complexity introduced by the experimental design. However, participants were able to correctly pair all speakers using all three proposed interaction metaphors. Providing superhuman hearing abilities in the form of a dual acoustic beamformer guided by head and hand movements resulted in statistically significant improvements in terms of pairing time, suggesting the task-relevance of interacting with multiple points of interests.

Functional Connectivity of Heschl's Gyrus Associated With Age-Related Hearing Loss: A Resting-State fMRI Study

A large proportion of older adults experience hearing loss. Yet, the impact of hearing loss on the aging brain, particularly on large-scale brain networks that support cognition and language, is relatively unknown. We used resting-state functional magnetic resonance imaging (fMRI) to identify hearing loss-related changes in the functional connectivity of primary auditory cortex to determine if these changes are distinct from age and cognitive measures known to decline with age (e.g., working memory and processing speed). We assessed the functional connectivity of Heschl's gyrus in 31 older adults (60-80 years) who expressed a range of hearing abilities from normal hearing to a moderate hearing loss. Our results revealed that both left and right Heschl's gyri were significantly connected to regions within auditory, sensorimotor, and visual cortices, as well as to regions within the cingulo-opercular network known to support attention. Participant age, working memory, and processing speed did not significantly correlate with any connectivity measures once variance due to hearing loss was removed. However, hearing loss was associated with increased connectivity between right Heschl's gyrus and the dorsal anterior cingulate in the cingulo-opercular network even once variance due to age, working memory, and processing speed was removed. This greater connectivity was not driven by high frequency hearing loss, but rather by hearing loss measured in the 0.5-2 kHz range, particularly in the left ear. We conclude that hearing loss-related differences in functional connectivity in older adults are distinct from other aging-related differences and provide insight into a possible neural mechanism of compensation for hearing loss in older adults.

The effect of the menstrual cycle on dichotic listening

The purpose of this study was to determine the effect of the menstrual cycle on responses to a dichotic listening task. It was hypothesized that participants would exhibit a stronger right ear advantage during the menstrual cycle days when estrogen levels are at their peak. It was also hypothesized that the women not taking oral contraceptives would exhibit greater variations in ear advantage over the course of their menstrual cycle than those taking oral contraceptives. Finally, it was hypothesized that the error response rates would remain similar across different listening conditions and over the menstrual cycle. The participants were 30 women who took oral contraceptives and 15 who did not. They completed nine listening sessions comprised of three dichotic listening tasks: forced-left, forced-right, and open. The data were analyzed using a mixed effects models. The participants exhibited a reduction in right ear responses on the days that corresponded to when the level of estrogen would begin to increase. This response was different from what had been hypothesized. The analysis also indicated no response differences between the two groups of women. In addition, the women exhibited fewer errors over the course of the sessions, implying that they adapted to the task. The results indicate that the women’s hormone fluctuation across the menstrual cycle affected their responses to the forced-left, cognitive control, task only.

Meaning in meaninglessness: The propensity to perceive meaningful patterns in coincident events and randomly arranged stimuli is linked to enhanced attention in early sensory processing

Perception of objectively independent events or stimuli as being significantly connected and the associated proneness to perceive meaningful patterns constitute part of the positive symptoms of schizophrenia, which are associated with altered attentional processes in lateralized speech perception. Since perceiving meaningful patterns is to some extent already prevalent in the general population, the aim of the study was to investigate whether the propensity to experience meaningful patterns in co-occurring events and random stimuli may be associated with similar altered attentional processes in lateralized speech perception. Self-reported and behavioral indicators of the perception of meaningful patterns were assessed in non-clinical individuals, along with EEG auditory evoked potentials during the performance of an attention related lateralized speech perception task (Dichotic Listening Test). A greater propensity to perceive meaningful patterns was associated with higher N1 amplitudes of the evoked potentials to the onset of the dichotically presented consonant-vowel syllables, indicating enhanced automatic attention in early sensory processing. The study suggests that more basic mechanisms in how people associate events may play a greater role in the cognitive biases that are manifest in personality expressions such as positive schizotypy, rather than that positive schizotypy moderates these cognitive biases directly.

Mismatch negativity (MMN) elicited by abstract regularity violations in two concurrent auditory streams

The study investigated whether violations of abstract regularities in two parallel auditory stimulus streams can elicit the MMN (mismatch negativity) event-related potential. Tone pairs from a low (220–392 Hz) and a high (1319–2349 Hz) stream were delivered in an alternating order either at a fast or a slow pace. With the slow pace, the pairs were perceptually heard as a single stream obeying an alternating low pair-high pair pattern, whereas with the fast pace, an experience of two separate auditory streams, low and high, emerged. Both streams contained standard and deviant pairs. The standard pairs were either in both streams ascending in the direction of the within-pair pitch change or in the one stream ascending and in the other stream descending. The direction of the deviant pairs was opposite to that of the same-stream standard pairs. The participant's task was either to ignore the auditory stimuli or to detect the deviant pairs in the designated stream. The deviant pairs elicited an MMN both when the directions of the standard pairs in the two streams were the same or when they were opposite. The MMN was present irrespective of the pace of stimulation. The results indicate that the preattentive brain mechanisms, reflected by the MMN, can extract abstract regularities from two concurrent streams even when the regularities are opposite in the two streams, and independently of whether there perceptually exists only one stimulus stream or two segregated streams. These results demonstrate the brain's remarkable ability to model various regularities embedded in the auditory environment and update the models when the regularities are violated. The observed phenomena can be related to several aspects of auditory information processing, e.g., music and speech perception and different forms of attention.

Right-Ear Advantage for Speech-in-Noise Recognition in Patients with Nonlateralized Tinnitus and Normal Hearing Sensitivity

Despite having normal hearing sensitivity, patients with chronic tinnitus may experience more difficulty recognizing speech in adverse listening conditions as compared to controls. However, the association between the characteristics of tinnitus (severity and loudness) and speech recognition remains unclear. In this study, the Quick Speech-in-Noise test (QuickSIN) was conducted monaurally on 14 patients with bilateral tinnitus and 14 age- and hearing-matched adults to determine the relation between tinnitus characteristics and speech understanding. Further, Tinnitus Handicap Inventory (THI), tinnitus loudness magnitude estimation, and loudness matching were obtained to better characterize the perceptual and psychological aspects of tinnitus. The patients reported low THI scores, with most participants in the slight handicap category. Significant between-group differences in speech-in-noise performance were only found at the 5-dB signal-to-noise ratio (SNR) condition. The tinnitus group performed significantly worse in the left ear than in the right ear, even though bilateral tinnitus percept and symmetrical thresholds were reported in all patients. This between-ear difference is likely influenced by a right-ear advantage for speech sounds, as factors related to testing order and fatigue were ruled out. Additionally, significant correlations found between SNR loss in the left ear and tinnitus loudness matching suggest that perceptual factors related to tinnitus had an effect on speech-in-noise performance, pointing to a possible interaction between peripheral and cognitive factors in chronic tinnitus. Further studies, that take into account both hearing and cognitive abilities of patients, are needed to better parse out the effect of tinnitus in the absence of hearing impairment.

A life in academia: My career in brief

In this article I have summarized some of the main trends and topics of my research career, spanning a time period of 50 years, from its start as a master student at the Department of Psychology, University of Uppsala, Sweden to seeing the end of a long career, now at the University of Bergen, Norway. This journey has, apart from having been a journey across various disciplines and topics in experimental psychology, psychophysiology and neuropsychology, functional neuroimaging and cognitive neuroscience, also been a social class journey for me personally. I describe my academic career from my arrival as a young student at the University of Uppsala, Sweden in the late 1960s to my graduation as PhD in 1977 at the age of 29 years, brief postdoc period at the University of Pennsylvania, USA, and finally professor at the University of Bergen, Norway. The article focuses on my view of the research and research findings during these years, including studies of hemispheric asymmetry, dyslexia and language, dichotic listening, fMRI, and during the last years, studies of auditory hallucinations in schizophrenia. I have collaborated with numerous people, both nationally and internationally over the years, far too many to mention in a space-limited overview article. I apologize for this, and wish that I had time and space to mention all the fantastic colleagues and friends that I have met during my career. This article is what I recall of dates, places, encounters, etc., and any errors and misunderstandings are entirely due to my far from perfect memory, for which I also apologize.

Enhanced Identification of Long Versus Short Voice Onset Time Consonant-Vowel Syllables in a Dichotic Listening Task

PURPOSE

This study investigated the influence of voice onset time (VOT) on the perception of consonant-vowel (CV) signals during a dichotic listening (DL) task.

METHOD

Sixty-two young adults with normal hearing were tested with the English language version of the Hugdahl Dichotic CV (DCV) Test. They were asked to identify 1 CV syllable during 3 DL conditions: free recall (report the syllable heard most clearly), forced right (report the syllable in the right ear), and forced left (report the syllable in the left ear). Averages for number and percent correct syllables were recorded under each condition and across the entire test.

RESULTS

All subjects demonstrated an overall right-ear advantage (REA) when scores from all 3 listening conditions were averaged. The REA occurred for all VOT pairings except when the long VOT was presented to the left ear, whereas the short VOT was presented to the right ear when subjects produced an average left-ear advantage. The left-ear advantage overcame the structural advantage of the right ear even when subjects were directed to attend to the right ear. This result was consistent with findings of earlier studies done with Norwegian and Australian subjects.

CONCLUSIONS

Listeners' REA may be overcome by interaural temporal differences that favor processing in the listener's nondominant ear during the DCV test. Balanced VOT conditions across the DCV test prevent this effect from producing an overall bias toward the left ear, but clinical DL tests with consonant-vowel-consonant words should be examined for effects of the long VOT on laterality of performance.

Hostility and cognitive control: Evidence of increased cardiovascular reactivity as a function of exposure to affective stress using a dichotic listening paradigm

Indices of cognitive control were examined in men with high and low levels of trait hostility as a function of exposure to affective and cognitive stress. A dual concurrent task paradigm was used whereby participants intentionally directed focus to the left or right ear under dichotic listening conditions before and after exposure to angry infant vocalizations. Analysis of the behavioral data supports the prediction of reduced right frontal regulatory control in men with high levels of hostility as indicated by diminished capacity to suppress report of phonemes presented to the language dominant left hemisphere (right ear) in the Focus Left condition. This diminishment in the capacity to suppress report of phonemes presented to the right ear in the Focus Left condition is suggestive of reduced cognitive control. With respect to the neurophysiological data, heart rate increased for only men with high levels of hostility in the Focus Left condition, and this was especially evident in the post-affective stress condition. This increase in right hemisphere arousal provides additional evidence of reduced cognitive control and support for the capacity model of hostility by implicating poor right frontal regulatory control over right posterior cerebral regions under dual task conditions. The results are discussed in terms of integrating the construct of cognitive control into the capacity model as well as providing implications regarding reductions in the capacity to suppress predominant aggressive responses in domestic settings.

Use of Multichannel Near Infrared Spectroscopy to Study Relationships Between Brain Regions and Neurocognitive Tasks of Selective/Divided Attention and 2-Back Working Memory

While dichotic listening (DL) was originally intended to measure bottom-up selective attention, it has also become a tool for measuring top-down selective attention. This study investigated the brain regions related to top-down selective and divided attention DL tasks and a 2-back task using alphanumeric and Japanese numeric sounds. Thirty-six healthy participants underwent near-infrared spectroscopy scanning while performing a top-down selective attentional DL task, a top-down divided attentional DL task, and a 2-back task. Pearson's correlations were calculated to show relationships between oxy-Hb concentration in each brain region and the score of each cognitive task. Different brain regions were activated during the DL and 2-back tasks. Brain regions activated in the top-down selective attention DL task were the left inferior prefrontal gyrus and left pars opercularis. The left temporopolar area was activated in the top-down divided attention DL task, and the left frontopolar area and left dorsolateral prefrontal cortex were activated in the 2-back task. As further evidence for the finding that each task measured different cognitive and brain area functions, neither the percentages of correct answers for the three tasks nor the response times for the selective attentional task and the divided attentional task were correlated to one another. Thus, the DL and 2-back tasks used in this study can assess multiple areas of cognitive, brain-related dysfunction to explore their relationship to different psychiatric and neurodevelopmental disorders.

Testing the Benefits of Neurofeedback on Selective Attention Measured Through Dichotic Listening

The electrophysiological changes after a single session of neurofeedback training (↑SMR/↓Theta) and its effects on executive attention during a dichotic listening test with forced attentional procedures were measured in a sample of 20 healthy women. A pre-post moment test double blind design, with the inclusion of a group receiving sham neurofeedback, allowed for minimization of alien influences. The interaction of Moment × Group was significant, indicating an enhancement of SMR band after the real neurofeedback. The dichotic listening scores were correlated with the amplitude of Beta band in baseline conditions. The performance on the forced left attentional condition in dichotic listening was significantly improved and correlated positively with the post-training enhancement of the SMR band. The sham neurofeedback group also improved DL scores, so a clear affirmation about the benefits of neurofeedback training over cognitive performance could not be unambiguously established. It is concluded that the protocol showed a good independence and acceptable trainability in modifying the EEG results, but there was limited interpretability regarding cognitive outcomes.

A right-ear bias of auditory selective attention is evident in alpha oscillations

Auditory selective attention makes it possible to pick out one speech stream that is embedded in a multispeaker environment. We adapted a cued dichotic listening task to examine suppression of a speech stream lateralized to the nonattended ear, and to evaluate the effects of attention on the right ear's well-known advantage in the perception of linguistic stimuli. After being cued to attend to input from either their left or right ear, participants heard two different four-word streams presented simultaneously to the separate ears. Following each dichotic presentation, participants judged whether a spoken probe word had been in the attended ear's stream. We used EEG signals to track participants' spatial lateralization of auditory attention, which is marked by interhemispheric differences in EEG alpha (8-14 Hz) power. A right-ear advantage (REA) was evident in faster response times and greater sensitivity in distinguishing attended from unattended words. Consistent with the REA, we found strongest parietal and right frontotemporal alpha modulation during the attend-right condition. These findings provide evidence for a link between selective attention and the REA during directed dichotic listening.

A lateralized functional auditory network is involved in anuran sexual selection

Right ear advantage (REA) exists in many land vertebrates in which the right ear and left hemisphere preferentially process conspecific acoustic stimuli such as those related to sexual selection. Although ecological and neural mechanisms for sexual selection have been widely studied, the brain networks involved are still poorly understood. In this study we used multi-channel electroencephalographic data in combination with Granger causal connectivity analysis to demonstrate, for the first time, that auditory neural network interconnecting the left and right midbrain and forebrain function asymmetrically in the Emei music frog (Babina daunchina), an anuran species which exhibits REA. The results showed the network was lateralized. Ascending connections between the mesencephalon and telencephalon were stronger in the left side while descending ones were stronger in the right, which matched with the REA in this species and implied that inhibition from the forebrainmay induce REA partly. Connections from the telencephalon to ipsilateral mesencephalon in response to white noise were the highest in the non-reproductive stage while those to advertisement calls were the highest in reproductive stage, implying the attention resources and living strategy shift when entered the reproductive season. Finally, these connection changes were sexually dimorphic, revealing sex differences in reproductive roles.

Network dynamics in dyslexia: Review and implications for remediation

Extant neurobiological theories of dyslexia appear fractional in focusing on isolated brain regions, mechanisms, and functional pathways. A synthesis of current research shows support for an Interactive Specialization (IS) model of dyslexia involving the dysfunctional orchestration of a widely-distributed, attentionally-controlled, hierarchical, and interhemispheric circuit of intercommunicating neuronal networks. This circuitry is comprised principally of the frontostriatal-parietal cognitive control system of networks, the posterior corpus callosum, and the left arcuate fasciculus. During development, the coalescence of these functionally specialized regions, acting together, may be essential to preventing the core phonemic and phonological processing deficits defining the dyslexic phenotype. Research demonstrating an association of each with processing phonology presents the foundational outline for a comprehensive, integrative theory of dyslexia and suggests the importance of inclusive remedial efforts aimed at promoting interactions among all three networking territories.

Dichotic listening as an index of lateralization of speech perception in familial risk children with and without dyslexia

Atypical language lateralization has been marked as one of the factors that may contribute to the development of dyslexia. Indeed, atypical lateralization of linguistic functions such as speech processing in dyslexia has been demonstrated using neuroimaging studies, but also using the behavioral dichotic listening (DL) method. However, so far, DL results have been mixed. The current study assesses lateralization of speech processing by using DL in a sample of children at familial risk (FR) for dyslexia. In order to determine whether atypical lateralization of speech processing relates to reading ability, or is a correlate of being at familial risk, the current study compares the laterality index of FR children who did and did not become dyslexic, and a control group of readers without dyslexia. DL was tested in 3rd grade and in 5/6th grade. Results indicate that at both time points, all three groups have a right ear advantage, indicative of more pronounced left-hemispheric processing. However, the FR-dyslexic children are less good at reporting from the left ear than controls and FR-nondyslexic children. This impediment relates to reading fluency.