Supra-Threshold LS CE-Chirp Auditory Brainstem Response in the Elderly.

INTRODUCTION: Aging deteriorates peripheral and central auditory structures and functions. In elders, for an accurate audiological evaluation, it is important to explore beyond the cochlear receptor. Audiograms provide an estimation of hearing thresholds, while the amplitudes and latencies of supra-threshold auditory brainstem response (ABR) can offer noninvasive measures of the auditory pathways functioning. Regarding ABR, in young populations, level-specific chirp (LS CE-chirp) stimulus has been proposed as an alternative synchronizing method to obtain larger ABR responses than those evoked by clicks. However, the supra-threshold characteristics of chirp evoked ABR, and their association to hearing thresholds is relatively unknown in the elderly. The aim of this study was to evaluate supra-threshold LS CE-chirp ABRs in an aged population by comparing their features with click ABRs, and evaluating their relationship with audiometric hearing thresholds. METHODS: We carried out a cross-sectional study to characterize the hearing of 125 adults aged over 65 years. We determined the audiometric hearing thresholds and supra-threshold ABRs elicited by LS CE-chirp and click stimuli at 80 dB nHL. We evaluated associations by means of partial correlations and covariate adjustment. We performed specific frequencies' analysis and subgroup analysis per hearing level. RESULTS: Wave V responses had significantly shorter latencies and larger amplitudes when elicited by LS CE-chirp as compared to click-evoked responses. Audiometric hearing thresholds correlated with age, but ABR characteristics did not. We found mild correlations between hearing thresholds and ABR characteristics, predominantly at higher frequencies and with chirp. We found scarce evidence of correlation between ABR characteristics and the average of behavioral hearing thresholds between 0.5 to 4 kHz (0.5-4 kHz PTA). After subgroup analysis according to the hearing level, no stronger or more significant correlations were found between ABR characteristics and 0.5-4 kHz PTA. DISCUSSION: In this study, we found that supra-threshold LS CE-chirp ABR presented some of the previously described similitudes and differences with supra-threshold click ABR in younger populations. Although, the average amplitude and latency of wave V evoked by LS CE-chirp were larger and faster than those evoked by clicks, these results should be taken with caution at the individual level, and further studies are required to state that LS CE-chirp ABRs are better than click ABRs in elders for clinical evaluations. We did not find consistent associations between hearing thresholds and supra-threshold wave V features, suggesting that these measures should be considered independently in the elderly.

Cochlear dysfunction as an early biomarker of cognitive decline in normal hearing and mild hearing loss.

INTRODUCTION: Age-related hearing loss is an important risk factor for cognitive decline. However, audiogram thresholds are not good estimators of dementia risk in subjects with normal hearing or mild hearing loss. Here we propose to use distortion product otoacoustic emissions (DPOAEs) as an objective and sensitive tool to estimate the risk of cognitive decline in older adults with normal hearing or mild hearing loss. METHODS: We assessed neuropsychological, brain magnetic resonance imaging, and auditory analyses on 94 subjects > 64 years of age. RESULTS: We found that cochlear dysfunction, measured by DPOAEs-and not by conventional audiometry-was associated with Clinical Dementia Rating Sum of Boxes (CDR-SoB) classification and brain atrophy in the group with mild hearing loss (25 to 40 dB) and normal hearing (<25 dB). DISCUSSION: Our findings suggest that DPOAEs may be a non-invasive tool for detecting neurodegeneration and cognitive decline in the older adults, potentially allowing for early intervention.

EOG-Based Human-Computer Interface: 2000-2020 Review.

Electro-oculography (EOG)-based brain-computer interface (BCI) is a relevant technology influencing physical medicine, daily life, gaming and even the aeronautics field. EOG-based BCI systems record activity related to users' intention, perception and motor decisions. It converts the bio-physiological signals into commands for external hardware, and it executes the operation expected by the user through the output device. EOG signal is used for identifying and classifying eye movements through active or passive interaction. Both types of interaction have the potential for controlling the output device by performing the user's communication with the environment. In the aeronautical field, investigations of EOG-BCI systems are being explored as a relevant tool to replace the manual command and as a communicative tool dedicated to accelerating the user's intention. This paper reviews the last two decades of EOG-based BCI studies and provides a structured design space with a large set of representative papers. Our purpose is to introduce the existing BCI systems based on EOG signals and to inspire the design of new ones. First, we highlight the basic components of EOG-based BCI studies, including EOG signal acquisition, EOG device particularity, extracted features, translation algorithms, and interaction commands. Second, we provide an overview of EOG-based BCI applications in the real and virtual environment along with the aeronautical application. We conclude with a discussion of the actual limits of EOG devices regarding existing systems. Finally, we provide suggestions to gain insight for future design inquiries.

Speech Perception and Dichotic Listening Are Associated With Hearing Thresholds and Cognition, Respectively, in Unaided Presbycusis.

Presbycusis or age-related hearing loss is a prevalent condition in the elderly population, which affects oral communication, especially in background noise, and has been associated with social isolation, depression, and cognitive decline. However, the mechanisms that relate hearing loss with cognition are complex and still elusive. Importantly, recent studies show that the use of hearing aids in presbycusis, which is its standard management, can induce neuroplasticity and modify performance in cognitive tests. As the majority of the previous studies on audition and cognition obtained their results from a mixed sample of subjects, including presbycusis individuals fitted and not fitted with hearing aids, here, we revisited the associations between hearing loss and cognition in a controlled sample of unaided presbycusis. We performed a cross-sectional study in 116 non-demented Chilean volunteers aged ≥65 years from the Auditory and Dementia study cohort. Specifically, we explored associations between bilateral sensorineural hearing loss, suprathreshold auditory brain stem responses, auditory processing (AP), and cognition with a comprehensive neuropsychological examination. The AP assessment included speech perception in noise (SIN), dichotic listening (dichotic digits and staggered spondaic words), and temporal processing [frequency pattern (FP) and gap-in-noise detection]. The neuropsychological evaluations included attention, memory, language, processing speed, executive function, and visuospatial abilities. We performed an exploratory factor analysis that yielded four composite factors, namely, hearing loss, auditory nerve, midbrain, and cognition. These four factors were used for generalized multiple linear regression models. We found significant models showing that hearing loss is associated with bilateral SIN performance, while dichotic listening was associated with cognition. We concluded that the comprehension of the auditory message in unaided presbycusis is a complex process that relies on audition and cognition. In unaided presbycusis with mild hearing loss (<40 dB HL), speech perception of monosyllabic words in background noise is associated with hearing levels, while cognition is associated with dichotic listening and FP.

Neural links between facial emotion recognition and cognitive impairment in presbycusis.

OBJECTIVES: Facial emotion recognition (FER) is impaired in people with dementia and with severe to profound hearing loss, probably reflecting common neural changes. Here, we aim to study the association between brain structures and FER impairment in mild to moderate age-related hearing loss participants. METHODS: We evaluated FER in a cross-sectional cohort of 111 Chilean nondemented elderly participants. They were assessed for FER in seven different categories using 35 facial stimuli. We collected pure-tone average (PTA) audiometric thresholds, cognitive and neuropsychiatric assessments, and morphometric brain imaging using a 3-Tesla MRI. RESULTS: According to PTA threshold levels, participants were classified as controls (≤25 dB, n = 56) or presbycusis (>25 dB, n = 55), with an average PTA of 17.08 ± 4.8 dB HL and 36.27 ± 9.5 dB HL respectively. Poorer total FER score was correlated with worse hearing thresholds (r = -0.23, p < 0.05) in participants with presbycusis. Multiple regression models explained 57 % of the variability of FER in presbycusis and 10% in controls. In both groups, the main determinant of FER was cognitive performance. In the brain structure of presbycusis participants, FER was correlated with the atrophy of the right insula, right hippocampus, bilateral cingulate cortex and multiple areas of the temporal cortex. In controls, FER was only associated with bilateral middle temporal cortex volume. CONCLUSIONS: FER impairment in presbycusis is distinctively associated with atrophy of neural structures engaged in the perceptual and conceptual level of face emotion processing.

Effects of Mental Effort on Premotor Muscle Activity and Maximal Grip Force.

The present study sought to evaluate how mental effort modulates premotor activity within forearm muscles in the context of an isometric grasping task. Muscle activity of the flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC) was recorded during the application of maximum grip forces in nineteen healthy adult subjects. Each subject was examined under two experimental conditions: 1) spontaneous initiation of grasp (SI) and 2) focused concentration preceding the initiation of grasp (CA). Two novel parameters, the mean premotor duration (MPD) and the mean premotor power (MPP) were used to distinguish patterns of muscle activity. Here we tested the hypothesis was maximal grip strength is primed by muscle activity during the premotor phase. Our results demonstrate that MPD for each muscle group was significantly longer in the CA condition than for the SI condition (BF10 = 491497) and that MPP was significantly greater in EDC than in FDS (BF10 = 4305). Furthermore, both the MPD and MPP of the EDC were significantly correlated with maximum grip force. These results suggest that the increase of premotor activity consequent to the mental effort (focused concentration) may support internal biomechanical and physiological mechanisms which serve to enhance patterns of neuromuscular synergies.

Reduced suprathreshold auditory nerve responses are associated with slower processing speed and thinner temporal and parietal cortex in presbycusis.

Epidemiological evidence shows an association between hearing loss and dementia in elderly people. However, the mechanisms that connect hearing impairments and cognitive decline are still unknown. Here we propose that a suprathreshold auditory-nerve impairment is associated with cognitive decline and brain atrophy. METHODS: audiological, neuropsychological, and brain structural 3-Tesla MRI data were obtained from elders with different levels of hearing loss recruited in the ANDES cohort. The amplitude of waves I (auditory nerve) and V (midbrain) from auditory brainstem responses were measured at 80 dB nHL. We also calculated the ratio between wave V and I as a proxy of suprathreshold brainstem function. RESULTS: we included a total of 101 subjects (age: 73.5 ± 5.2 years (mean ± SD), mean education: 9.5 ± 4.2 years, and mean audiogram thresholds (0.5-4 kHz): 25.5 ± 12.0 dB HL). We obtained reliable suprathreshold waves V in all subjects (n = 101), while replicable waves I were obtained in 92 subjects (91.1%). Partial Spearman correlations (corrected by age, gender, education and hearing thresholds) showed that reduced suprathreshold wave I responses were associated with thinner temporal and parietal cortices, and with slower processing speed as evidenced by the Trail-Making Test-A and digit symbol performance. Non-significant correlations were obtained between wave I amplitudes and other cognitive domains. CONCLUSIONS: These results evidence that reduced suprathreshold auditory nerve responses in presbycusis are associated with slower processing speed and brain structural changes in temporal and parietal regions.

Insula and Amygdala Atrophy Are Associated With Functional Impairment in Subjects With Presbycusis.

Hearing loss is an important risk factor for dementia. However, the mechanisms that relate these disorders are still unknown. As a proxy of this relationship, we studied the structural brain changes associated with functional impairment in activities of daily living in subjects with age related hearing loss, or presbycusis. One hundred eleven independent, non-demented subjects older than 65 years recruited in the ANDES cohort were evaluated using a combined approach including (i) audiological tests: hearing thresholds and cochlear function measured by pure tone averages and the distortion product otoacoustic emissions respectively; (ii) behavioral variables: cognitive, neuropsychiatric, and functional impairment in activities of daily living measured by validated questionnaires; and (iii) structural brain imaging-assessed by magnetic resonance imaging at 3 Tesla. The mean age of the recruited subjects (69 females) was 73.95 ± 5.47 years (mean ± SD) with an average educational level of 9.44 ± 4.2 years of schooling. According to the audiometric hearing thresholds and presence of otoacoustic emissions, we studied three groups: controls with normal hearing (n = 36), presbycusis with preserved cochlear function (n = 33), and presbycusis with cochlear dysfunction (n = 38). We found a significant association (R 2 D = 0.17) between the number of detected otoacoustic emissions and apathy symptoms. The presbycusis with cochlear dysfunction group had worse performance than controls in global cognition, language and executive functions, and severe apathy symptoms than the other groups. The neuropsychiatric symptoms and language deficits were the main determinants of functional impairment in both groups of subjects with presbycusis. Atrophy of insula, amygdala, and other temporal areas were related with functional impairment, apathy, and language deficits in the presbycusis with cochlear dysfunction group. We conclude that (i) the neuropsychiatric symptoms had a major effect on functional loss in subjects with presbycusis, (ii) cochlear dysfunction is relevant for the association between hearing loss and behavioral impairment, and (iii) atrophy of the insula and amygdala among other temporal areas are related with hearing loss and behavioral impairment.

Temporal Deployment of Attention by Mental Training: an fMRI Study.

In this study, we employed a visuo-motor imagery task of alertness as a mental training to examine temporal processing of motor responses within healthy young adults. Participants were divided into two groups (group 1; n = 20 who performed the mental training before the real physical task and a control group who performed the physical task without mental training). We vary the time interval between the imperative stimulus and the preceding one (fore-period) in which temporal preparation and arousal increase briefly. Our behavioural results provide clear evidence that mental training reinforces both temporal preparation and arousal, by shortening reaction time (RT), especially for the shortest fore-periods (FP) within exogenous "FP 250 ms" (p = 0.008) and endogenous alertness "FP 650 ms" (p = 0.001). We investigated how the brain controls such small temporal changes. We focus our neural hypothesis on three brain regions: anterior insula, dorsolateral prefrontal cortex, and anterior cingulate cortex and three putative circuits: one top-down (from dorsolateral prefrontal cortex to anterior cingulate cortex) and two bottom-up (from anterior insula to dorsolateral prefrontal cortex and anterior cingulate cortex). In fMRI, effective connectivity is strengthened during exogenous alertness between anterior insula and dorsolateral prefrontal cortex (p = 0.001), between anterior insula and cingulate cortex (p = 0.01), and during endogenous alertness between dorsolateral prefrontal cortex and anterior cingulate cortex (p = 0.05). We suggest that attentional reinforcement induced by an intensive and short session of mental training induces a temporal deployment of attention and allow optimizing the time pressure by maintaining a high state of arousal and ameliorating temporal preparation.

Electro-Encephalography and Electro-Oculography in Aeronautics: A Review Over the Last Decade (2010-2020).

Electro-encephalography (EEG) and electro-oculography (EOG) are methods of electrophysiological monitoring that have potentially fruitful applications in neuroscience, clinical exploration, the aeronautical industry, and other sectors. These methods are often the most straightforward way of evaluating brain oscillations and eye movements, as they use standard laboratory or mobile techniques. This review describes the potential of EEG and EOG systems and the application of these methods in aeronautics. For example, EEG and EOG signals can be used to design brain-computer interfaces (BCI) and to interpret brain activity, such as monitoring the mental state of a pilot in determining their workload. The main objectives of this review are to, (i) offer an in-depth review of literature on the basics of EEG and EOG and their application in aeronautics; (ii) to explore the methodology and trends of research in combined EEG-EOG studies over the last decade; and (iii) to provide methodological guidelines for beginners and experts when applying these methods in environments outside the laboratory, with a particular focus on human factors and aeronautics. The study used databases from scientific, clinical, and neural engineering fields. The review first introduces the characteristics and the application of both EEG and EOG in aeronautics, undertaking a large review of relevant literature, from early to more recent studies. We then built a novel taxonomy model that includes 150 combined EEG-EOG papers published in peer-reviewed scientific journals and conferences from January 2010 to March 2020. Several data elements were reviewed for each study (e.g., pre-processing, extracted features and performance metrics), which were then examined to uncover trends in aeronautics and summarize interesting methods from this important body of literature. Finally, the review considers the advantages and limitations of these methods as well as future challenges.

Cingulate Cortex Atrophy Is Associated With Hearing Loss in Presbycusis With Cochlear Amplifier Dysfunction.

Age-related hearing loss is associated with cognitive decline and has been proposed as a risk factor for dementia. However, the mechanisms that relate hearing loss to cognitive decline remain elusive. Here, we propose that the impairment of the cochlear amplifier mechanism is associated with structural brain changes and cognitive impairment. Ninety-six subjects aged over 65 years old (63 female and 33 male) were evaluated using brain magnetic resonance imaging, neuropsychological and audiological assessments, including distortion product otoacoustic emissions as a measure of the cochlear amplifier function. All the analyses were adjusted by age, gender and education. The group with cochlear amplifier dysfunction showed greater brain atrophy in the cingulate cortex and in the parahippocampus. In addition, the atrophy of the cingulate cortex was associated with cognitive impairment in episodic and working memories and in language and visuoconstructive abilities. We conclude that the neural abnormalities observed in presbycusis subjects with cochlear amplifier dysfunction extend beyond core auditory network and are associated with cognitive decline in multiple domains. These results suggest that a cochlear amplifier dysfunction in presbycusis is an important mechanism relating hearing impairments to brain atrophy in the extended network of effortful hearing.

Collaboration of Cerebello-Rubral and Cerebello-Striatal Loops in a Motor Preparation Task.

In this study, we used fMRI to identify brain regions associated with concentration (sustained attention) during a motor preparation task. In comparison with a non-concentration task, increased activities were observed (P < 0.05, FWE-corrected P values) in cerebellar lobules VI and VII, motor cortex, pre-supplementary motor area (pre-SMA), thalamus, red nucleus (RN), and caudate nucleus (CN). Moreover, analysis of effective connectivity inter-areal (psychophysiological interactions) showed that during preparation, concentration-related brain activity increase was dependent on Cerebello-thalamo-pre-SMA-RN and Pre-SMA-CN-thalamo-M1 loops. We postulate that, while pre-SMA common to both loops is specifically involved in the movement preparation and readiness for voluntary movement through the striatum, the cerebellar lobule VI in conjunction with RN, likely through a cerebellar-rubro-olivary-cerebellar loop, might be implicated in concentration-related optimization of upcoming motor performances.

Effects of verbal encouragement on force and electromyographic activations during exercise.

BACKGROUND: The aim of the present study was to examine the effects of verbal encouragement on isometric force and associated electromyographic (EMG) parameters during a handgrip task. METHODS: Twenty-three participants (12 women and 11 men) performed maximal voluntary isometric handgrip contractions following three conditions: 1) verbal encouragement (VE) condition: participants executed isometric contractions while being verbally encouraged; 2) non-verbal encouragement (nVE) condition: the same starting and stopping signal but without encouragement; 3) non-concentration and non-motivation (nCM) condition: self-initiated contractions without concentration and motivation. Start and stop of the contraction were self-initiated. The maximal voluntary force (MVF) and the maximal rate of force development (MRFD) were measured. Integrated EMG corresponding to MVF (iEMGMVF) and to MRFD (iEMGMRFD) were collected from flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC) muscles. RESULTS: MVF was higher during VE compared with nVE (+11.7%; P<0.05) and nCM (+23.2%; P<0.05) conditions. Likewise, MRFD was significantly higher during VE, compared with nVE (+21.7%; P<0.05) and nCM (+55.4%; P<0.05) conditions. iEMGMVF increased for FDS and EDC during VE, compared to nVE (+26.19%, +20.5%) and nCM conditions (+68.85%, +48.91%), respectively. iEMGMRFD increased for FDS and EDC during VE, compared to nVE (+21.2%, +46.07%) and nCM conditions (+23.79%, +42.32%). Furthermore, the reproducibility of all these indices was higher with VE condition. CONCLUSIONS: Taken together, force production (MVF and MRFD) and EMG data supported the view that muscles activity is considerably influenced by the verbal encouragements during isometric force exercise.

Exploration and Identification of Cortico-Cerebellar-Brainstem Closed Loop During a Motivational-Motor Task: an fMRI Study.

The cerebellum is involved not only in motor coordination, training, and memory, but also in cognition and emotion. Lobule VI in particular belongs to sensorimotor, salience, and executive cerebellar networks. This study aims to determine whether lobule VI would constitute an integrative interface between motor and cognitive/emotional circuits during a motor task with verbal encouragement, likely in conjunction with the basal ganglia (reward and motivational system). We used fMRI to identify specific recruitment of cerebellar and striatal systems during physical performance using two motor tasks with and without encouragement. We found that: (i) Force results were higher during verbal encouragement than during basal condition in all participants. (ii) The anterior part of the right lobule VI was activated by motor execution in both tasks, while its posterior part was specifically activated by verbal encouragement. (iii) The closed-connectivity loop maintained motivation induced by verbal encouragement between cerebral and cerebellar through the red nucleus and striatal network. Therefore, right lobule VI is a hub-controlling sensorimotor and motivates aspects of motor performance in relation with the red nucleus and the ventral striatum. These results could have important implications for extrapyramidal and multisystem degenerative diseases.