No association between chronic cannabis use and loudness dependence of auditory evoked potentials as indicator of central serotonergic neurotransmission

Chronic cannabis use has been found to be associated with major depression. It is suggested that cannabis use induces changes in neurotransmitter systems involved in the pathogenesis of depressive disorders, particularly in the serotonergic system. The analysis of the loudness dependence of auditory evoked potentials (LDAEP) is a valid non-invasive indicator of central serotonergic activity in animals and humans. In the present study, we investigated the effects of chronic cannabis use on LDAEP in 30 psychiatrically unaffected users compared to 30 non-user controls. Users were required to abstain from cannabis for at least 24 h before testing. Putative depressive symptoms were assessed by using the Beck Depression Inventory (BDI) and the Hamilton Rating Scale for Depression (HAMD-21). LDAEP as well as BDI and HAMD-21 scores did not differ between cannabis users and controls. Moreover, LDAEP neither correlate with duration and quantity of cannabis use nor with psychometric assessments. These results indicate that chronic cannabis use had no influence on the LDAEP in this study sample. It can be suggested that significant alterations in serotonergic systems may rather be related to acute activation of the endogenous cannabinoid system or to cannabis dependence accompanied by manifest depressive symptoms.     

Modification of the Threshold Equalising Noise (TEN) test for cochlear dead regions for use with steeply sloping high-frequency hearing loss

Steeply sloping high-frequency hearing loss is often associated with cochlear dead regions. These can be identified by measuring pure-tone thresholds in quiet and in Threshold-Equalising Noise (TEN). However, many patients cannot be adequately tested because the low frequencies in the TEN lead to uncomfortable loudness. We investigated the effect of high-pass filtering on the TEN-test results and the loudness of the TEN. Twenty-four normally hearing subjects and 35 subjects with steeply sloping high-frequency hearing loss were tested, using the standard TEN (TENs), and TEN high-pass filtered at 0.5?kHz (TEN0.5) or 1?kHz (TEN1). For both groups, masked thresholds did not differ across noise types for frequencies above 1?kHz. Over 50% of the hearing-impaired ears tested met the criteria for a dead region at 4?kHz, using all three noise types. However, masked thresholds and the prevalence of positive TEN-test results at 1?kHz were both lower with the TEN1. The TEN1 was judged the most comfortable noise by 68% of the hearing-impaired subjects. We conclude that high-pass filtering would allow testing at higher TEN levels for patients with steeply sloping hearing loss.

Sumario

La hipoacusia de perfil abruptamente descendente en frecuencias agudas se asocia frecuentemente con regiones cocleares muertas. Esto se puede identificar midiendo los umbrales tonales en silencio y en ruido ecualizado al umbral (TEN). Sin embargo, algunos pacientes no pueden ser estudiados adecuadamente porque las frecuencias bajas en el TEN, les produce molestia. Investigamos el efecto del filtro pasa-alto en los resultados de las pruebas TEN y la intensidad subjetiva del TEN. Se examinaron 24 sujetos normoyentes y 35 con hipoacusia de perfil abruptamente descendente en frecuencias agudas, utilizando el TEN habitual y el TEN con filtro pasa/alto a 0.5?kHz (TEN0.5) o 1?kHz (TEN1). Los umbrales de enmascaramiento no difirieron con los diferentes tipos de ruido para las frecuencias por arriba de 1?kHz en ambos grupos. Más del 50% de los oídos hipoacúsicos cumplieron con los criterios para considerar una zona muerta a 4?kHz, con los tres tipos de ruido. Sin embargo, los umbrales de enmascaramiento y la prevalencia de una prueba TEN positiva a 1?kHZ fueron menores con el TEN1. El 68% de los hipoacúsicos consideraron al TEN1 como el ruido más confortable. Concluimos que el filtro pasa-alto puede permitir realizar pruebas con mayor intensidad TEN en pacientes con hipoacusia de perfil abruptamente descendente en frecuencias agudas.     

Cochlear Findings in VIIIth Nerve Tumors

We have been particularly concerned with the large number of patients with confirmed retrocochlear lesions who have demonstrated cochlear test results on audiological evaluation. The literature is replete with information suggesting that the patient with a tumor of the VIIIth nerve will demonstrate the classical signs of significant reduction in auditory speech discrimination, abnormal tone decay, lack of loudness recruitment, negative SISI scored and Békésy tracings classifiable as either type III or type IV. We feel it is safe to say that one rarely encounters such a clearcut picture.

In this paper we discuss the audiologic data for a series of patients recently evaluated in our department. All these patients demonstrated only cochlear findings on audiological evaluation, yet all patients had surgically confirmed VIIIth nerve tumors.     

Visual distance cues modulate neuromagnetic auditory N1m responses

Objective

Auditory distance judgment relies on several acoustic cues and can be modulated by visual information. Sound intensity serves as one such cue as it decreases with increasing distance. In this magnetoencephalography (MEG) experiment, we tested whether N1m MEG responses, previously described to scale with sound intensity, are modulated by visual distance cues.

Methods

We recorded behavioral and MEG data from 15 healthy normal hearing participants. Noise bursts at different sound pressure levels were paired with synchronous visual cues at different distances. We hypothesized that noise paired with far visual cues will be represented louder and result in increased N1m amplitudes compared to a pairing with close visual cues. This might be based on a compensation of visually induced distance when processing loudness.

Results

Psychophysically, we observed no significant modulation of loudness judgments by visual cues. However, N1m MEG responses at about 100 ms after stimulus onset were significantly stronger with distal compared to proximal visual cues in the left auditory cortex.

Conclusions

Our results suggest an audio–visual interaction at an early stage in the left auditory cortex, possibly related to cue integration for auditory distance processing.

Significance

Sound distance processing could prove itself as a promising model system for the investigation of intra-modal and cross-modal integration principles.     

Post-operative Stapedius Reflex Tests with Simultaneous Loudness Scaling in Patients Supplied with Cochlear Implants

The estimation of the maximum comfort loudness levels (MCL) by measurements of the electrically elicited stapedius reflex was examined in six experienced cochlear implant users supplied with the COMBI 40 implant system. The stapedius reflex was tested and loudness scaling was performed simultaneously using an up/down stimulation protocol close to the reflex threshold with automated recording of both test procedures. The electrical stapedius reflex threshold (ESRT) and loudness scaling were evaluated separately. Scaling at the reflex threshold ranged between normal and loud. The range of stimulus intensities corresponding to ESRT is much smaller than that at a particular loudness category. The overall correlation between ESRT and MCL was high (r=0.92), with a similar dependence of ESRT and MCL on the channel stimulated. Thus, when the stapedius reflex can be detected post-op-eratively, the ESRT can be applied successfully for the fitting procedure of the speech processor. Simultaneous loudness scaling during the entire reflex test showed that overstimulation via the implant can be avoided effectively.     

Critical Bandwidth in Patients with a Hearing Loss Induced by Salicylates

During a slight temporary salicylate-induced hearing loss, the normal loudness difference between broad-band noise and narrow-band noise was markedly reduced at all levels, except the highest. The critical band, measured at 1 kHz by means of a loudness summation method, appeared to become wider in 9 out of 16 subjects, to a degree roughly proportional to the degree of hearing loss. However, some discrepancies in the data and a rather large intersubject variability of the loudness estimates were present. The localization of the mechanism which forms the basis for the critical band concept is discussed in view of the results.

Au cours d'une surdité légère et passagère due au salicylate, la différence, normale, de sonie entre une bande large de bruit et une bande étroite de bruit s'est trouvée réduite sensiblement pour tous les niveaux d'intensité sauf les plus forts. La bande critique pour 1 kHz mesurée par la méthode de l'intégration des sonies est apparue plus large chez 9 sujets sur 16, et cela d'une façon approximativement proportionnelle au degré de surdité. Nous devons cependant retenir un manque d'uniformité dans les résultats et une variabilité assez importante de sujet à sujet a propos de l'estimation de la sonie. A la lumière des résultats obtenus, nous discutons la localisation du mécanisme sur lequel est basé le concept de bande critique.     

Trait impulsivity and increased pre-attentional sensitivity to intense stimuli in bipolar disorder and controls

Impulsivity and sensation seeking are stimulus-oriented traits. Because they differ in degree of intention and planning, they may have distinct neurophysiological mechanisms. Impulsivity is prominent in bipolar disorder, and may be related to pre-attentional information filtering and stimulus-orientation. We investigated specificity of relationships between impulsivity and sensitivity to stimulus intensity in bipolar disorder and controls, using intensity–sensitivity of auditory evoked potentials. Seventy-six subjects (37 healthy controls, 39 with bipolar disorder) were administered an intensity–sensitivity paradigm. Additional measures included Barratt Impulsiveness Scale (BIS-11) and Eysenck Impulsivity and Venturesomeness scores. State-dependent rapid-response impulsivity was measured using the Immediate Memory Task. Intensity-sensitivities of the auditory evoked P1N1, N1P2, P1, N1, and P2 potentials were assessed as the slope of amplitude relative to loudness. Analyses used general linear models (GLM) with impulsivity-related measures as dependent variables and age, gender, education, and diagnosis as dependent variables. BIS-11 total, motor, and attentional impulsivity scores correlated positively with pre-attentional N1 and P1N1 intensity–sensitivity slopes in bipolar disorder, but not in controls. BIS-11 nonplanning and Eysenck Venturesomeness scores did not correlate with intensity–sensitivity. Intensity–sensitivity slopes did not correlate with rapid-response impulsivity. Correlations between N1 or P1N1 slopes and BIS-11 scores in bipolar disorder were not affected by age, education, WAIS, treatment, symptoms, or gender. Trait impulsivity in bipolar disorder may be related to poorly modulated stimulus-driven late pre-attentional responses to stimuli, potentially resulting in exaggerated responses to intense stimuli even before conscious awareness. Components of trait impulsivity are physiologically heterogenous relative to intensity–sensitivity.     

Loudness adaptation measured by the simultaneous dichotic loudness balance technique differs between genders

Loudness adaptation was measured using the classic simultaneous, dichotic loudness balance technique. A 6-min continuous tone was introduced using headphones to a participant’s adaptingear. Immediately upon presentation of the tone and at 1-min intervals, participants adjusted the sound level of a tone of the same frequency in the contralateral controlear until both tones sounded equally loud. The control ear, which was otherwise retained in silence, measured adaptation in the adapting ear. As the constant-sound level stimulus to the adapting ear continued, the sound level that a participant selected to produce equal loudness between ears decreased, oscillating towards an apparent asymptotic value. This value was used to calculate total decibels of adaptation. The magnitude of female adaptation exceeded that of males at all time points measured following stimulus onset. The ratio total dB of adaptation to dB SL of the test tone may provide an empirical estimate for the loudness exponent, n, seen in Stevens’ power law, L = kφⁿ_, which relates the intensity of a pure tone, φ, to the loudness of the tone, L. Since dB of adaptation for females was greater than that of males, female n-values exceeded those of males, in accordance with previous research.     

Loudness summation and the mismatch negativity event-related brain potential in humans

Abstract Infrequently omitting a sound from a repetitive sequence elicits the mismatch negativity (MMN) ERP response when the stimulus onset asynchrony (SOA) is less than 200 ms. We contrasted two alternative explanations of omission MMN. (1) Each sound starts a separate temporal integration process. Omissions violate the constancy of the temporal structure within the integration window. (2) Sounds preceding an omission are perceived to be louder than those followed by a sound within the integration period, because omissions allow the full stimulus aftereffect to be included in perceived loudness. We varied the SOA between 117 and 217 ms. For this case, the temporal structure explanation predicts that no MMN will be elicited, whereas the loudness summation explanation predicts that MMN will be elicited. MMN was elicited by tone omissions with random SOA, suggesting that loudness summation plays an important role in the elicitation of omission MMN.     

伴有重振听力障碍者的助听器验配

目的探讨伴有重振的听力障碍者助听器验配方法。方法对于伴有重振的听力障碍者在选配助听器时尽可能选择压缩线路的数字助听器,或者是具备自动增益功能的助听器;在助听器的调节时应注重最大声输出的限制,并适当降低听觉动态范围较窄的个别频率的增益;此外助听器的适应性训练和随诊调节助听器也是验配成功的重要环节。结果92%的患者获得了满意的配戴效果。结论伴有重振的听力障碍者验配助听器要采用适当的方法。