The frontoparietal multiple demand network interacts with the dual pathways in auditory working memory.

The frontoparietal multiple demand (MD) network has been proposed as a control network that regulates processing demands while enabling goal-directed actions. This study tested the MD network account in auditory working memory (AWM) and identified its functional role and relationship with the dual pathways model in AWM, where segregation of function was based on the sound domain. Forty-one healthy young adults performed an n-back task consisting of an orthogonal combination of the sound domain (spatial versus nonspatial) and cognitive operation (low load versus high load). Functional connectivity and correlation analyses were performed to assess the connectivity of the MD network and the dual pathways. Our results confirmed the contribution of the MD network to AWM and identified its interactions with the dual pathways in both sound domains and during high and low load levels. At high loads, the strength of connectivity with the MD network correlated with task accuracy, indicating the key role of the MD network in supporting successful performance as cognitive load increases. This study contributed to the auditory literature by showing that both the MD network and dual pathways collaborate with each other to support AWM, and neither of them alone is adequate to explain auditory cognition.

Mismatch negativity as a marker of auditory pattern separation.

To what extent does incidental encoding of auditory stimuli influence subsequent episodic memory for the same stimuli? We examined whether the mismatch negativity (MMN), an event-related potential generated by auditory change detection, is correlated with participants' ability to discriminate those stimuli (i.e. targets) from highly similar lures and from dissimilar foils. We measured the MMN in 30 young adults (18-32 years, 18 females) using a passive auditory oddball task with standard and deviant 5-tone sequences differing in pitch contour. After exposure, all participants completed an incidental memory test for old targets, lures, and foils. As expected, participants at test exhibited high sensitivity in recognizing target items relative to foils and lower sensitivity in recognizing target items relative to lures. Notably, we found a significant correlation between MMN amplitude and lure discrimination, but not foil discrimination. Our investigation shows that our capacity to discriminate sensory inputs at encoding, as measured by the MMN, translates into precision in memory for those inputs.

Absolute pitch: neurophysiological evidence for early brain activity in prefrontal cortex.

Absolute pitch (AP) is the ability to rapidly label pitch without an external reference. The speed of AP labeling may be related to faster sensory processing. We compared time needed for auditory processing in AP musicians, non-AP musicians, and nonmusicians (NM) using high-density electroencephalographic recording. Participants responded to pure tones and sung voice. Stimuli evoked a negative deflection peaking at ~100 ms (N1) post-stimulus onset, followed by a positive deflection peaking at ~200 ms (P2). N1 latency was shortest in AP, intermediate in non-AP musicians, and longest in NM. Source analyses showed decreased auditory cortex and increased frontal cortex contributions to N1 for complex tones compared with pure tones. Compared with NM, AP musicians had weaker source currents in left auditory cortex but stronger currents in left inferior frontal gyrus (IFG) during N1, and stronger currents in left IFG during P2. Compared with non-AP musicians, AP musicians exhibited stronger source currents in right insula and left IFG during N1, and stronger currents in left IFG during P2. Non-AP musicians had stronger N1 currents in right auditory cortex than nonmusicians. Currents in left IFG and left auditory cortex were correlated to response times exclusively in AP. Findings suggest a left frontotemporal network supports rapid pitch labeling in AP.

Aging Enhances Neural Activity in Auditory, Visual, and Somatosensory Cortices: The Common Cause Revisited.

In humans, age-related declines in vision, hearing, and touch coincide with changes in amplitude and latency of sensory-evoked potentials. These age-related differences in neural activity may be related to a common deterioration of supra-modal brain areas (e.g., PFC) that mediate activity in sensory cortices or reflect specific sensorineural impairments that may differ between sensory modalities. To distinguish between these two possibilities, we measured neuroelectric brain activity while 37 young adults (18-30 years, 18 males) and 35 older adults (60-88 years, 20 males) were presented with a rapid randomized sequence of lateralized auditory, visual, and somatosensory stimuli. Within each sensory domain, we compared amplitudes and latencies of sensory-evoked responses, source activity, and functional connectivity (via phase-locking value) between groups. We found that older adults' early sensory-evoked responses were greater in amplitude than those of young adults in all three modalities, which coincided with enhanced source activity in auditory, visual, and somatosensory cortices. Older adults also showed stronger neural synchrony than young adults between superior prefrontal and sensory cortices; and in older adults, the degree of phase synchrony was positively correlated with the magnitude of source activity in sensory areas. Critically, older adults who showed enhanced neural activity in one sensory domain also showed enhanced activity in other modalities. Together, these findings support the common cause hypothesis of aging and highlight the role of prefrontal regions in exerting top-down control over sensory cortices.SIGNIFICANCE STATEMENT A prominent theory of aging posits that age-related declines in sensory processing across domains are related to a single common neurobiological mechanism. However, the neural evidence supporting this common cause hypothesis has remained elusive. Our study revealed robust age-related changes in three sensory domains across a range of neural metrics. Importantly, older adults who showed increased neural activity within one sensory domain also showed enhanced neural activity in the other two sensory modalities. No such relation among activity in sensory cortices was observed in young adults. Age-related increases in neural activity in sensory cortices coincided with enhanced neural synchrony between the PFC and sensory cortices, underlining the importance of the PFC in regulating sensory processing.

Individual Differences in Multisensory Processing Are Related to Broad Differences in the Balance of Local versus Distributed Information.

The brain's ability to extract information from multiple sensory channels is crucial to perception and effective engagement with the environment, but the individual differences observed in multisensory processing lack mechanistic explanation. We hypothesized that, from the perspective of information theory, individuals with more effective multisensory processing will exhibit a higher degree of shared information among distributed neural populations while engaged in a multisensory task, representing more effective coordination of information among regions. To investigate this, healthy young adults completed an audiovisual simultaneity judgment task to measure their temporal binding window (TBW), which quantifies the ability to distinguish fine discrepancies in timing between auditory and visual stimuli. EEG was then recorded during a second run of the simultaneity judgment task, and partial least squares was used to relate individual differences in the TBW width to source-localized EEG measures of local entropy and mutual information, indexing local and distributed processing of information, respectively. The narrowness of the TBW, reflecting more effective multisensory processing, was related to a broad pattern of higher mutual information and lower local entropy at multiple timescales. Furthermore, a small group of temporal and frontal cortical regions, including those previously implicated in multisensory integration and response selection, respectively, played a prominent role in this pattern. Overall, these findings suggest that individual differences in multisensory processing are related to widespread individual differences in the balance of distributed versus local information processing among a large subset of brain regions, with more distributed information being associated with more effective multisensory processing. The balance of distributed versus local information processing may therefore be a useful measure for exploring individual differences in multisensory processing, its relationship to higher cognitive traits, and its disruption in neurodevelopmental disorders and clinical conditions.

Neural correlates of concurrent sound perception: A review and guidelines for future research.

The perception of concurrent sound sources depends on processes (i.e., auditory scene analysis) that fuse and segregate acoustic features according to harmonic relations, temporal coherence, and binaural cues (encompass dichotic pitch, location difference, simulated echo). The object-related negativity (ORN) and P400 are electrophysiological indices of concurrent sound perception. Here, we review the different paradigms used to study concurrent sound perception and the brain responses obtained from these paradigms. Recommendations regarding the design and recording parameters of the ORN and P400 are made, and their clinical applications in assessing central auditory processing ability in different populations are discussed.

Objective and Subjective Hearing Difficulties Are Associated With Lower Inhibitory Control.

OBJECTIVE: Evidence suggests that hearing loss increases the risk of cognitive impairment. However, the relationship between hearing loss and cognition can vary considerably across studies, which may be partially explained by demographic and health factors that are not systematically accounted for in statistical models. DESIGN: Middle-aged to older adult participants (N = 149) completed a web-based assessment that included speech-in-noise (SiN) and self-report measures of hearing, as well as auditory and visual cognitive interference (Stroop) tasks. Correlations between hearing and cognitive interference measures were performed with and without controlling for age, sex, education, depression, anxiety, and self-rated health. RESULTS: The risk of having objective SiN difficulties differed between males and females. All demographic and health variables, except education, influenced the likelihood of reporting hearing difficulties. Small but significant relationships between objective and reported hearing difficulties and the measures of cognitive interference were observed when analyses were controlled for demographic and health factors. Furthermore, when stratifying analyses for males and females, different relationships between hearing and cognitive interference measures were found. Self-reported difficulty with spatial hearing and objective SiN performance were better predictors of inhibitory control in females, whereas self-reported difficulty with speech was a better predictor of inhibitory control in males. This suggests that inhibitory control is associated with different listening abilities in males and females. CONCLUSIONS: The results highlight the importance of controlling for participant characteristics when assessing the relationship between hearing and cognitive interference, which may also be the case for other cognitive functions, but this requires further investigations. Furthermore, this study is the first to show that the relationship between hearing and cognitive interference can be captured using web-based tasks that are simple to implement and administer at home without any assistance, paving the way for future online screening tests assessing the effects of hearing loss on cognition.

Effects of temporal order and intentionality on reflective attention to words in noise.

Speech perception in noise is a cognitively demanding process that challenges not only the auditory sensory system, but also cognitive networks involved in attention. The predictive coding theory has been influential in characterizing the influence of prior context on processing incoming auditory stimuli, with comparatively less research dedicated to "postdictive" processes and subsequent context effects on speech perception. Effects of subsequent semantic context were evaluated while manipulating the relationship of three target words presented in noise and the temporal position of targets compared to the subsequent contextual cue, demonstrating that subsequent context benefits were present regardless of whether the targets were related to each other and did not depend on the position of the target. However, participants instructed to focus on the relation between target and cue performed worse than those who did not receive this instruction, suggesting a disruption of a natural process of continuous speech recognition. We discuss these findings in relation to lexical commitment and stimulus-driven attention to short-term memory as mechanisms of subsequent context integration.

Proposal for Cut-off Scores for Sensitive Skin on Sensitive Scale-10 in a Group of Adult Women.

Sensitive skin is commonly assessed on the basis of self-reports from patients, and sometimes questionnaires, such as the Sensitive Scale-10, are used. The severity of sensitive skin follows a continuum, from the absence of sensitive skin to very sensitive skin. The aims of this cross-sectional study were to compare subjects with and without symptomatic sensitive skin and to propose diagnostic criteria for sensitive skin. A total of 160 women, between 18 and 65 years of age, with and without sensitive skin, and without any associated skin diseases, were recruited. Mean age was 41 years old. Fifty-five percent of participants reported having "very sensitive" or "sensitive" skin. In the sensitive skin group, the participants mainly experienced skin irritability (100%), tautness (97.5%), discomfort (90%) and redness (90%). According to the receiver operating characteristic curve, a Sensitive Scale-10 (SS-10) cut-off value of 12.7 can be used to detect sensitive skin (with a sensitivity of 72.4% and specificity of 90.3%).

Use of Cosmetic Products in Real Life by Women with Facial Sensitive Skin: Results from an Exposure Study and Comparison with Controls.

Triggering factors of sensitive skin are supposed to be physical, chemical (cosmetics, water, and pollutants), and occasionally psychological (stress). A recent meta-analysis showed that the most important triggering factor declared by subjects is the use of cosmetics. This study was designed to compare the consumption of cosmetic products in women with sensitive skin and controls. After a dermatological examination, women between the ages of 18 and 65 years with or without sensitive skin were recruited. They completed different questionnaires about the presence of sensitive skin and use of 28 cosmetics that could be applied on the face. The amount per application was recorded for all products used at least once a week on the face. In total, 160 women were included, with a mean age of 41 ± 13 years. Two groups of 40 women were created based on the sensitive scale (SS-10 score), with the lowest SS-10 scores (nonsensitive skin group) and the highest SS-10 score (sensitive skin group). The number of products used daily was similar in the 2 groups. Women with sensitive skin were significantly more frequent users of liquid soap/soap-free gel cleansers than those without sensitive skin (70 vs. 43%). There was no difference concerning the frequency of use of products in the 2 groups. Concerning the amount of product used by application, women with sensitive skin used twice as much cream per application compared with the women without sensitive skin: 511 ± 438 µg versus 290 ± 203 µg (p = 0.039). Concerning the composition of the cosmetic products used, the only difference concerned phenoxyethanol, which was more often present in the moisturizer of women without sensitive skin (66.7%) than in those with sensitive skin (32.4%) (p = 0.007). Women with sensitive skin were more likely to buy products recommended for sensitive skin by manufacturers. The relationship of causality between the use of cosmetics and sensitive skin cannot be established. Women with sensitive skin used different cosmetic products than women without sensitive skin. Women with sensitive skin used a higher amount of moisturizer, used products recommended for sensitive skin, and bought more cosmetic products at pharmacies than supermarkets. We hypothesized that subjects with sensitive skin are looking for products that improve the sensation of skin sensitivity.

Involuntary Orienting and Conflict Resolution during Auditory Attention: The Role of Ventral and Dorsal Streams.

Selective attention to sound object features such as pitch and location is associated with enhanced brain activity in ventral and dorsal streams, respectively. We examined the role of these pathways in involuntary orienting and conflict resolution using fMRI. Participants were presented with two tones that may, or may not, share the same nonspatial (frequency) or spatial (location) auditory features. In separate blocks of trials, participants were asked to attend to sound frequency or sound location and ignore the change in the task-irrelevant feature. In both attend-frequency and attend-location tasks, RTs were slower when the task-irrelevant feature changed than when it stayed the same (involuntary orienting). This behavioral cost coincided with enhanced activity in the pFC and superior temporal gyrus. Conflict resolution was examined by comparing situations where the change in stimulus features was congruent (both features changed) and incongruent (only one feature changed). Participants were slower and less accurate for incongruent than congruent sound features. This congruency effect was associated with enhanced activity in the pFC and was greater in the right superior temporal gyrus and medial frontal cortex during the attend-location task than during the attend-frequency task. Together, these findings do not support a strict division of "labor" into ventral and dorsal streams but rather suggest interactions between these pathways in situations involving changes in task-irrelevant sound feature and conflict resolution. These findings also validate the Test of Attention in Listening task by revealing distinct neural correlates for involuntary orienting and conflict resolution.

Simultaneous EEG and MEG recordings reveal vocal pitch elicited cortical gamma oscillations in young and older adults.

The frequency-following response with origin in the auditory brainstem represents the pitch contour of voice and can be recorded with electrodes from the scalp. MEG studies also revealed a cortical contribution to the high gamma oscillations at the fundamental frequency (f0) of a vowel stimulus. Therefore, studying the cortical component of the frequency-following response could provide insights into how pitch information is encoded at the cortical level. Comparing how aging affects the different responses may help to uncover the neural mechanisms underlying speech understanding deficits in older age. We simultaneously recorded EEG and MEG responses to the syllable /ba/. MEG beamformer analysis localized sources in bilateral auditory cortices and the midbrain. Time-frequency analysis showed a faithful representation of the pitch contour between 106 Hz and 138 Hz in the cortical activity. A cross-correlation revealed a latency of 20 ms. Furthermore, stimulus onsets elicited cortical 40-Hz responses. Both the 40-Hz and the f0 response amplitudes increased in older age and were larger in the right hemisphere. The effects of aging and laterality of the f0 response were evident in the MEG only, suggesting that both effects were characteristics of the cortical response. After comparing f0 and N1 responses in EEG and MEG, we estimated that approximately one-third of the scalp-recorded f0 response could be cortical in origin. We attributed the significance of the cortical f0 response to the precise timing of cortical neurons that serve as a time-sensitive code for pitch.

Neural dynamics supporting auditory long-term memory effects on target detection.

Auditory long-term memory has been shown to facilitate signal detection. However, the nature and timing of the cognitive processes supporting such benefits remain equivocal. We measured neuroelectric brain activity while young adults were presented with a contextual memory cue designed to assist with the detection of a faint pure tone target embedded in an audio clip of an everyday environmental scene (e.g., the soundtrack of a restaurant). During an initial familiarization task, participants heard such audio clips, half of which included a target sound (memory cue trials) at a specific time and location (left or right ear), as well as audio clips without a target (neutral trials). Following a 1-h or 24-h retention interval, the same audio clips were presented, but now all included a target. Participants were asked to press a button as soon as they heard the pure tone target. Overall, participants were faster and more accurate during memory than neutral cue trials. The auditory contextual memory effects on performance coincided with three temporally and spatially distinct neural modulations, which encompassed changes in the amplitude of event-related potential as well as changes in theta, alpha, beta and gamma power. Brain electrical source analyses revealed greater source activity in memory than neutral cue trials in the right superior temporal gyrus and left parietal cortex. Conversely, neutral trials were associated with greater source activity than memory cue trials in the left posterior medial temporal lobe. Target detection was associated with increased negativity (N2), and a late positive (P3b) wave at frontal and parietal sites, respectively. The effect of auditory contextual memory on brain activity preceding target onset showed little lateralization. Together, these results are consistent with contextual memory facilitating retrieval of target-context associations and deployment and management of auditory attentional resources to when the target occurred. The results also suggest that the auditory cortices, parietal cortex, and medial temporal lobe may be parts of a neural network enabling memory-guided attention during auditory scene analysis.

Inhibitory Control Deficits in Individuals with Amnestic Mild Cognitive Impairment: a Meta-Analysis.

Amnestic mild cognitive impairment (aMCI) is a prodromal stage of Alzheimer's disease that is characterized by impairments in episodic memory. Recent evidence has shown that inhibitory control is also impaired in aMCI. The aim of the present meta-analysis was to quantify inhibitory control ability in individuals with aMCI by examining performance across a range of well-defined inhibition paradigms that tapped into one of three inhibitory control subtypes (i) interference control (e.g., Stroop task), (ii) response inhibition (e.g., Go/Nogo task), or (iii) inhibition of cognitive sets (Wisconsin Card Sort Task). Reference databases (PsychINFO, PubMed, and Web of Science) were searched for studies comparing individuals with aMCI to healthy controls on behavioural measures of inhibition. Across 70 effect sizes involving 2184 adults with aMCI and 3049 controls, overall inhibition deficits of moderate magnitude (g = -0.73) were found among individuals with aMCI. Inhibition deficits were moderate in size regardless of inhibitory control subtype: interference control (g = -0.74), response inhibition (g = -0.71), inhibition of cognitive sets (g = -0.76). Subgroup analyses revealed that Stroop outcome measure (reaction time vs. accuracy) and recruitment source (clinical vs. community) moderated interference control deficits. Together these findings support a generalized inhibition deficit in aMCI, and suggest that inhibition tasks should be included routinely in neuropsychological test batteries to provide a more comprehensive overview of executive dysfunction in aMCI.

Orienting Attention to Auditory and Visual Short-term Memory: The Roles of Age, Hearing Loss, and Cognitive Status.

Background/Study Context: Attention can be reflectively oriented to a visual or auditory representation in short-term memory, but it is not clear how aging and hearing acuity affects reflective attention. The purpose of the present study was to examine whether performance in auditory and visual reflective attention tasks varies as a function of participants' age and hearing status.Methods: Young (19 to 33 years) and older adults with normal or mild to moderate hearing loss (62-90 years) completed a delayed match-to-sample task in which participants were first presented with a memory array of four different digits to hold in memory. Two digits were presented visually (left and right hemifield), and two were presented aurally (left and right ears simultaneously). During the retention interval, participants were presented with a cue (dubbed retro-cue), which could be either uninformative or indicated to the participants to retrospectively orient their attention to either auditory short-term memory (ASTM) or visual short-term memory (VSTM). The cue was followed by another delay, after which a single item was presented (i.e., test probe) for comparison (match or no match) with the items held in ASTM and/or VSTM.Results: Overall, informative retro-cue yielded faster response time than uninformative retro-cue. The retro-cue benefit in response time was comparable for auditory and visual-orienting retro-cue and similar in young and older adults. Regression analyses showed that only the auditory-orienting retro-cue benefit was predicted by hearing status rather than age per se.Conclusion: Both younger and older adults can benefit from visual and auditory-orienting retro-cues, but the auditory-orienting retro-cue benefit decreases with poorer hearing acuity. This finding highlights changes in cognitive processes that come with age even in those with just mild-to-moderate hearing loss, and suggest that older adults' performance in working memory tasks is sensitive to low level auditory scene analysis (i.e., concurrent sound segregation).

Mild Cognitive Impairment Is Characterized by Deficient Brainstem and Cortical Representations of Speech.

Mild cognitive impairment (MCI) is recognized as a transitional phase in the progression toward more severe forms of dementia and is an early precursor to Alzheimer's disease. Previous neuroimaging studies reveal that MCI is associated with aberrant sensory-perceptual processing in cortical brain regions subserving auditory and language function. However, whether the pathophysiology of MCI extends to speech processing before conscious awareness (brainstem) is unknown. Using a novel electrophysiological approach, we recorded both brainstem and cortical speech-evoked brain event-related potentials (ERPs) in older, hearing-matched human listeners who did and did not present with subtle cognitive impairment revealed through behavioral neuropsychological testing. We found that MCI was associated with changes in neural speech processing characterized as hypersensitivity (larger) brainstem and cortical speech encoding in MCI compared with controls in the absence of any perceptual speech deficits. Group differences also interacted with age differentially across the auditory pathway; brainstem responses became larger and cortical ERPs smaller with advancing age. Multivariate classification revealed that dual brainstem-cortical speech activity correctly identified MCI listeners with 80% accuracy, suggesting its application as a biomarker of early cognitive decline. Brainstem responses were also a more robust predictor of individuals' MCI severity than cortical activity. Our findings suggest that MCI is associated with poorer encoding and transfer of speech signals between functional levels of the auditory system and advance the pathophysiological understanding of cognitive aging by identifying subcortical deficits in auditory sensory processing mere milliseconds (<10 ms) after sound onset and before the emergence of perceptual speech deficits.SIGNIFICANCE STATEMENT Mild cognitive impairment (MCI) is a precursor to dementia marked by declines in communication skills. Whether MCI pathophysiology extends below cerebral cortex to affect speech processing before conscious awareness (brainstem) is unknown. By recording neuroelectric brain activity to speech from brainstem and cortex, we show that MCI hypersensitizes the normal encoding of speech information across the hearing brain. Deficient neural responses to speech (particularly those generated from the brainstem) predicted the presence of MCI with high accuracy and before behavioral deficits. Our findings advance the neurological understanding of MCI by identifying a subcortical biomarker in auditory-sensory processing before conscious awareness, which may be a precursor to declines in speech understanding.

Cortical sources of the auditory attentional blink.

Attentional blink (AB) refers to the situation where correctly identifying a target impairs the processing of a subsequent probe in a sequence of stimuli. Although the AB often coincides with a modulation of scalp-recorded cognitive event-related potentials (ERPs), the neural sources of this effect remain unclear. In two separate experiments, we used classical LORETA analysis recursively applied (CLARA) to estimate the neural sources of ERPs elicited by an auditory probe when it immediately followed an auditory target (i.e., AB condition), when no auditory target was present (i.e., no-AB condition), and when the probe followed an auditory target but occurred outside of the AB time window (i.e., no-AB condition). We observed a processing deficit when the probe immediately followed the target, and this auditory AB was accompanied by reduced P3b amplitude. Contrasting brain electrical source activity from the AB and no-AB conditions revealed reduced source activity in the medial temporal region as well as in the temporoparietal junction (extending into inferior parietal lobe), ventromedial prefrontal cortex, left anterior thalamic nuclei, mammillary body, and left cerebellum. The results indicate that successful probe identification following a target relies on a widely distributed brain network and further support the suggestion that the auditory AB reflects the failure of the probe to reach short-term consolidation. NEW & NOTEWORTHY Within a rapid succession of auditory stimuli, the perception of a predefined target sound often impedes listeners' ability to detect another target sound that is presented close in succession. This attentional blink may be related to activity in brain areas supporting attention and memory. We show that the auditory attentional blink is associated with brain activity changes in a network including the medial temporal lobe, parietal cortex, and prefrontal cortex. This study suggests that a problem in the interaction between attention and memory underlies the auditory attentional blink.

Listening under difficult conditions: An activation likelihood estimation meta-analysis.

The brain networks supporting speech identification and comprehension under difficult listening conditions are not well specified. The networks hypothesized to underlie effortful listening include regions responsible for executive control. We conducted meta-analyses of auditory neuroimaging studies to determine whether a common activation pattern of the frontal lobe supports effortful listening under different speech manipulations. Fifty-three functional neuroimaging studies investigating speech perception were divided into three independent Activation Likelihood Estimate analyses based on the type of speech manipulation paradigm used: Speech-in-noise (SIN, 16 studies, involving 224 participants); spectrally degraded speech using filtering techniques (15 studies involving 270 participants); and linguistic complexity (i.e., levels of syntactic, lexical and semantic intricacy/density, 22 studies, involving 348 participants). Meta-analysis of the SIN studies revealed higher effort was associated with activation in left inferior frontal gyrus (IFG), left inferior parietal lobule, and right insula. Studies using spectrally degraded speech demonstrated increased activation of the insula bilaterally and the left superior temporal gyrus (STG). Studies manipulating linguistic complexity showed activation in the left IFG, right middle frontal gyrus, left middle temporal gyrus and bilateral STG. Planned contrasts revealed left IFG activation in linguistic complexity studies, which differed from activation patterns observed in SIN or spectral degradation studies. Although there were no significant overlap in prefrontal activation across these three speech manipulation paradigms, SIN and spectral degradation showed overlapping regions in left and right insula. These findings provide evidence that there is regional specialization within the left IFG and differential executive networks underlie effortful listening.

Assessment of Aflatoxin M1 and M2 exposure risk through Oaxaca cheese consumption in southeastern Mexico.

The present study evaluated the exposure of Southeast Mexican population to Aflatoxin M1 (AFM1) and M2 (AFM2) through the consumption of Oaxaca cheese. The intake of Oaxaca cheese was assessed via a food 7-day dairy questionnaire (N = 1100, 2014 and 2015). Thirty Oaxaca cheeses were randomly sampled, and the origin of the samples was also investigated. AFM1 and AFM2 were quantified by HPLC-FD. The exposure was assessed through the combination of the Probabilistic Density Functions (probabilistic approach). The percentage of the population at risk was calculated through the population exceeding the toxicological reference values (TDI). The risk assessment revealed that the population at higher risk to AFM1 and AFM2 was the children, followed by the adolescents and adult women. To our knowledge, the present study is the first to assess the exposure risk of different age groups of a population to AFM1 and AFM2 through the consumption of cheese.

Noise differentially impacts phoneme representations in the auditory and speech motor systems.

Although it is well accepted that the speech motor system (SMS) is activated during speech perception, the functional role of this activation remains unclear. Here we test the hypothesis that the redundant motor activation contributes to categorical speech perception under adverse listening conditions. In this functional magnetic resonance imaging study, participants identified one of four phoneme tokens (/ba/, /ma/, /da/, or /ta/) under one of six signal-to-noise ratio (SNR) levels (-12, -9, -6, -2, 8 dB, and no noise). Univariate and multivariate pattern analyses were used to determine the role of the SMS during perception of noise-impoverished phonemes. Results revealed a negative correlation between neural activity and perceptual accuracy in the left ventral premotor cortex and Broca's area. More importantly, multivoxel patterns of activity in the left ventral premotor cortex and Broca's area exhibited effective phoneme categorization when SNR ≥ -6 dB. This is in sharp contrast with phoneme discriminability in bilateral auditory cortices and sensorimotor interface areas (e.g., left posterior superior temporal gyrus), which was reliable only when the noise was extremely weak (SNR > 8 dB). Our findings provide strong neuroimaging evidence for a greater robustness of the SMS than auditory regions for categorical speech perception in noise. Under adverse listening conditions, better discriminative activity in the SMS may compensate for loss of specificity in the auditory system via sensorimotor integration.