Detection efficiency of auditory steady state evoked by modulated noise.

AIM: This study aimed to investigate the efficiency of Magnitude Squared Coherence (MSC) and Spectral F test (SFT) for the detection of auditory steady state responses (ASSR) obtained by amplitude-modulated noises. MATERIAL AND METHODS: Twenty individuals (12 women) without any history of neurological or audiological diseases, aged from 18 to 59 years (mean ± standard deviation = 26.45 ± 3.9 years), who provided written informed consent, participated in the study. The Audiostim system was used for stimulating and ASSR recording. The tested stimuli were amplitude-modulated Wide-band noise (WBN), Low-band noise (LBN), High-band noise (HBN), Two-band noise (TBN) between 77 and 110 Hz, applied in intensity levels of 55, 45, and 25 dB sound pressure level (SPL). MSC and SFT, two statistical-based detection techniques, were applied with a significance level of 5%. Detection times and rates were compared using the Friedman test and Tukey-Kramer as post hoc analysis. Also based on the stimulation parameters (stimuli types and intensity levels) and detection techniques (MSC or SFT), 16 different pass/fail protocols, for which the true negatives (TN) were calculated. RESULTS: The median detection times ranged from 68 to 157s for 55 dB SPL, 68-99s for 45 dB SPL, and 84-118s for 25 dB SPL. No statistical difference was found between MSC and STF considering the median detection times (p > 0.05). The detection rates ranged from 100% to 55.6% in 55 dB SPL, 97.2%-38.9% in 45 dB SPL and 66.7%-8.3% in 25 dB SPL. Also for detection rates, no statistical difference was observed between MSC and STF (p > 0.05). True negatives (TN) above 90% were found for Protocols that employed WBN or HBN, at 55 dB SPL or that used WBN or HBN, at 45 dB SPL. For Protocols employing TBN, at 55 dB SPL or 45 dB SPL TN below 60% were found due to the low detection rates of stimuli that included low-band frequencies. CONCLUSION: The stimuli that include high-frequency content showed higher detection rates (>90%) and lower detection times (<3 min). The noise composed by two bands applied separately (TBN) is not feasible for clinical applications since it requires prolonging the exam duration, and also led to a reduced percentage of true negatives. On the other hand, WBN and HBN achieved high detection performance and high TN and should be investigated to implement pass/fail protocol for hearing screening with clinical population. Finally, both WBN and HBN seemed to be indifferent to the employed technique (SFT or MSC), which can be seen as another advantage of ASSR employment.

Daytime sleepiness in Parkinson's disease: perception, influence of drugs, and mood disorder.

Parkinson's disease (PD) is associated with sleep complaints as excessive daytime sleepiness (EDS) and several factors have been implicated in the genesis of these complaints. Objective. To correlate the subjective perception of EDS with variables as the severity of the motor symptoms, medications, and the presence of depressive symptoms. Materials and Methods. A cross-sectional study, using specific scales as Epworth sleepiness scale (ESS), Beck depression inventory (iBeck) and Hoehn and Yahr (HY), in 42 patients with PD. Results. The patients had a mean age of 61.2 ± 11.3 years and mean disease duration of 4.96 ± 3.3 years. The mean ESS was 7.5 ± 4.7 and 28.6% of patients reached a score of abnormally high value (>10). There was no association with gender, disease duration, and dopamine agonists. Patients with EDS used larger amounts of levodopa (366.7 ± 228.0 versus 460.4 ± 332.25 mg, P = 0.038), but those who had an iBeck >20 reached lower values of ESS than the others (5.9 ± 4.1 versus 9.3 ± 4.8, P = 0.03). Conclusions. EDS was common in PD patients, being related to levodopa intake. Presence of depressed mood may influence the final results of self-assessment scales for sleep disorders.

Obstructive sleep apnea severity correlates with cellular and plasma oxidative stress parameters and affective symptoms.

Obstructive sleep apnea syndrome (OSAS) is considered a sleep-related respiratory disorder, characterized by repetitive episodes of complete (apnea) or partial (hypopnea) obstruction of airflow in the upper airway (UA) during sleep. The pathophysiology of upper airway obstruction in OSAS is multifactorial, leading to a chronic recurrent state of intermittent hypoxemia and reoxygenation during sleep, maintaining a state of oxidative stress, which seems to be the key to the pathophysiological manifestations of OSAS, and is associated with the development of a number of high morbidity-mortality systematic complications, such as obesity, type 2 diabetes, metabolic syndrome, and cardiovascular and neuropsychological diseases. This study is an open, cross-sectional, and comparative clinical trial, whose general objective was to assess the correlation between OSAS severity, oxidative stress markers, and the presence of affective symptoms (depressive and anxious) in OSAS patients. We studied 38 adult males, who had been diagnosed with OSAS by overnight polysomnography, between 18 and 60 years of age, divided into three groups: group 1-10 individuals with mild OSAS (AHI between 5 and 14.9/h), group 2-13 individuals with moderate OSAS (AHI between 15 and 30/h), and group 3-15 individuals with severe OSAS (AHI >30/h). All individuals were evaluated for level of subjective sleepiness using the Epworth Sleepiness Scale, for depressive and anxiety symptoms by the Hamilton Depression (HAM-D) and Anxiety (HAM-A) Scales, and for parameters of the oxidative stress state, measuring superoxide radical and serum nitrates and nitrites levels. There was a progressive and significant increase in the state of oxidative stress (p < 0.05), in the total score of depressive symptoms (p = 0.001) and in the overall score of anxiety symptoms (p = 0.004) directly proportional to the severity of apnea when comparing the mild group to the severe group. Positive correlations were identified between superoxide production and the apnea-hypopnea index (AHI) (r = 0.48), Epworth sleepiness score (r = 0.36), and Hamilton depression score (HAM-D) (r = 0.40); between serum nitrates and nitrites levels and SO(2) min (r = 0.44); and between the AHI and the HAM-D (r = 0.51) score and HAM-A (r = 0.40) score. Negative correlations were observed between the AHI and serum nitrates and nitrites levels (r = -0.42), between superoxide production and SO(2) min (r = -0.31), between serum nitrates and nitrites levels and HAM-D (r = -0.50) and HAM-A (-0.42) scores, and between SO(2) min and HAM-D (r = -0.48) and HAM-A (r = -0.40) scores. According to the results of this study, we can conclude that (1) individuals with OSAS show an increase in the production of superoxide radical and a decrease in serum nitrates and nitrites levels, which are objective signs of a state of oxidative stress. (2) The more severe the OSAS, the more fragmented the sleep and the greater the nocturnal hypoxemia, the more severe is the oxidative stress state and the greater is the incidence of daytime symptoms, especially sleepiness and depressive and anxiety symptoms. Future studies might explore the investigation of oxidative stress parameters as an alternative approach to anticipate symptoms, measure prognosis, and monitor OSAS progression or treatment response.

Anatomy and functional architecture of the anconeus muscle / Anatomía y arquitectura funcional del músculo ancóneo

The anconeus is a small muscle situated at the elbow. Although the anconeus is active during elbow extension its importance for the movement is probably small. It could work as an elbow stabilizer. The object of this study was to investigate some anatomic and architectural characteristics of the anconeus, in the hope of shedding light on its function. We studied twenty adult cadaveric specimens. The anconeus originates by the lateral epicondyle of the humerus and inserts along the proximal ulna. The superficial shape of the anconeus is triangular. Tridimensionally the anconeus resembles a hemisected rectangular-based pyramid, with the base at the ulna and apex at the lateral epicondyle. The muscle fibers arise obliquely from the tendinous expansion and inserts at the ulna. Thus, the architecture of the anconeus is penniform, an architecture able to produce more force then displacement. The design index of 0.3 also suggests a force muscle.

El ancóneo es un pequeño músculo situado en la región del codo. Aunque el músculo ancóneo es activo durante la extensión del codo su importancia para este movimiento es probablemente pequeña. Podría actuar como estabilizador del codo. El objetivo de este trabajo fue investigar algunas características anatómicas y arquitectónicas del músculo ancóneo, con la esperanza de lanzar una cierta luz en su función. Estudiamos 20 cadáveres de adultos. El músculo ancóneo se origina al lado del epicóndilo lateral y se inserta en la ulna. La forma superficial del músculo ancóneo es triangular. Tridimensionalmente, el músculo ancóneo se asemeja a la mitad de una pirámide de base rectangular, con la base en la ulna y el ápice lateral al epicóndilo lateral. Sus fibras musculares describen un trayecto oblicuo con una extensión tendinosa que se insertan en la ulna. Por lo tanto, la arquitectura del músculo ancóneo es peniforme, una arquitectura conveniente para producir mayor fuerza con el desplazamiento. El índice de diseño de 0,3 también lo sugiere como un músculo de fuerza.

Multiple auditory steady-state responses (MASTER): stimulus and recording parameters.

Steady-state responses evoked by simultaneously presented amplitude-modulated tones were measured by examining the spectral components in the recording that corresponded to the different modulation frequencies. When using modulation frequencies between 70 and 110 Hz and an intensity of 60 dB SPL, there were significant interactions between two stimuli when the carrier frequencies were closer than one half of an octave apart, with attenuation of the response to the lower carrier frequency. However, there were no significant decreases in response amplitude with four simultaneous stimuli provided the carrier frequencies differed by one octave or more. Higher intensities (70 dB SPL) resulted in greater interactions between the stimuli than when low intensities (35 dB SPL) were used. Modulation frequencies could be as closely spaced as 1.3 Hz without affecting the responses. Using broad-band noise as a carrier instead of a pure tone resulted in a significantly larger response when the stimuli were presented at the same sound pressure level. At modulation frequencies between 30 and 50 Hz, there were greater interactions between stimuli than at faster modulation frequencies. These results support the following recommendations for using multiple stimuli in evoked potential audiometry: (1) The multiple stimulus technique works well for steady state responses at frequencies between 70 and 110 Hz. (2) Up to four stimuli can be simultaneously presented to an ear without significant loss in amplitude of the response, provided the carrier frequencies are separated by an octave and the intensities are 60 dB SPL or less. (3) Bandpass noise might serve as a better carrier signal than pure tones.

Frequency-specific audiometry using steady-state responses.

OBJECTIVE: To evaluate the audiometric usefulness of steady-state responses to multiple simultaneous tones, amplitude-modulated at 75 to 110 Hz. DESIGN: Steady-state responses to multiple tones amplitude-modulated at different rates between 75 and 110 Hz and presented simultaneously were recorded at different intensities in normal adults, well babies, normal adults with simulated hearing loss, and adolescents with known hearing losses. Response thresholds were compared with behavioral thresholds. RESULTS: In normal adults the thresholds for steady-state responses to tones of 0.5, 1, 2, and 4 kHz were 14 +/- 11, 12 +/- 11, 11 +/- 8, and 13 +/- 11 dB, respectively, above behavioral thresholds for air-conducted stimuli, and 11 +/- 5, 14 +/- 8, 9 +/- 8, and 10 +/- 10 dB above behavioral thresholds for bone-conducted stimuli. In well babies tested in a quiet environment, the thresholds were 45 +/- 13, 29 +/- 10, 26 +/- 8, and 29 +/- 10 dB SPL. In adolescents with known hearing losses, the steady-state responses thresholds predict behavioral thresholds with correlation coefficients (r) of 0.72, 0.70, 0.76, and 0.91 at 0.5, 1, 2, and 4 kHz, respectively. CONCLUSION: Steady-state responses to tone amplitude-modulated at 75 to 110 Hz can be used for frequency-specific objective audiometry. The multiple-stimulus technique allows thresholds to be estimated for eight different stimuli at the same time.

Auditory steady-state responses to multiple simultaneous stimuli.

Steady-state responses can follow multiple simultaneous auditory stimuli. If the stimuli are modulated at different rates, responses specific to each stimulus can be assessed by measuring in the frequency domain response the spectral component corresponding to the rate of modulation. When each stimulus has a different carrier frequency or different ear of presentation, the responses when 8 stimuli are presented simultaneously are not significantly different than when each stimulus is presented alone. Since significant responses can be recognized down to intensities that average 14 dB above behavioral threshold, this technique may be useful in objective audiometry. It is also possible to record steady-state responses to multiple modulations of the same carrier frequency. In this case, the amplitude of the responses when the stimuli are combined is smaller than when the stimuli are presented alone. The decrease in amplitude depends upon the number of concomitant stimuli and their relative intensities. These effects are probably due to the compressive rectification occurring during cochlear transduction, and the data may be used to model cochlear processing of auditory stimuli.

Auditory steady-state responses to tones amplitude-modulated at 80-110 Hz.

Steady-state responses can be recorded from the human scalp in response to tones that are sinusoidally modulated in amplitude at rates between 60 and 120 Hz. For 60 dB SPL 1000-Hz tones the maximum baseline-to-peak amplitude of about 0.06 microV occurs for modulation rates between 80 and 95 Hz. The phase of the response does not change with modulation depths greater than 25% and the amplitude saturates at modulation depths greater than 50%. The presence or absence of a response can be accurately determined by frequency-domain statistics and the response becomes clearly recognizable at intensities that are 16 +/- 8 dB above behavioral thresholds. With increasing intensity the response increases in amplitude at 1.9 nV/dB until an intensity of 70 dB SPL. As the intensity increases above 70 dB SPL the response increases in amplitude more rapidly at 7.8 nV/dB (at 1000 Hz) and contains significant energy at harmonics of the modulation frequency. This second stage of the intensity function is more prominent for stimuli with lower carrier frequencies (500 more than 1000 more than 2000 Hz) and is attenuated by high-pass masking. These steady-state responses should be helpful in evaluating human auditory physiology and in objective audiometry.

Ocular artifacts in EEG and event-related potentials. I: Scalp topography.

The ocular artifacts that contaminate the EEG derive from the potential difference between the cornea and the fundus of the eye. This corneofundal or corneoretinal potential can be considered as an equivalent dipole with its positive pole directed toward the cornea. The cornea shows a steady DC potential of approximately +13 mV relative to the forehead. Blink potentials are caused by the eyelids sliding down over the positively charged cornea. The artifacts from eye-movements result from changes in orientation of the corneo-fundal potential. The scalp-distribution of the ocular artifacts can be described in terms of propagation factors--the fraction of the EOG signal at periocular electrodes that is recorded at a particular scalp location. These factors vary with the location of the scalp electrode. Propagation factors for blinks and upward eye-movements are significantly different.

Ocular artifacts in recording EEGs and event-related potentials. II: Source dipoles and source components.

The source dipoles for blinks point radially whereas the source dipoles for saccades point tangentially, in the direction of the eye movement. This indicates that blink potentials are not generated by eye movements but by the eyelid sliding down over the positively charged cornea. Dipole source dipole analysis shows that the "rider artifact" at the onset of upward and lateral saccades is caused by the eyelid as it lags a little behind the eyes at the beginning of the movement. Dipole source analysis allows both the EEG and the EOG to be modeled simultaneously and EOG generators to be distinguished from nearby EEG generators. Ocular source components can be calculated from a principal component analysis of EEG and EOG recordings during blinks and saccades. The effectiveness of propagation factors, source dipoles and source components in removing ocular artifacts from EEG samples was assessed. The most effective correction procedure uses source components.