An Exploratory Study of the Effect of Tinnitus on Listening Effort Using EEG and Pupillometry.

OBJECTIVE: Previous behavioral studies on listening effort in tinnitus patients did not consider extended high-frequency hearing thresholds and had conflicting results. This inconsistency may be related that listening effort is not evaluated by the central nervous system (CNS) and autonomic nervous system (ANS), which are directly related to tinnitus pathophysiology. This study matches hearing thresholds at all frequencies, including the extended high-frequency and reduces hearing loss to objectively evaluate listening effort over the CNS and ANS simultaneously in tinnitus patients. STUDY DESIGN: Case-control study. SETTING: University hospital. METHODS: Sixteen chronic tinnitus patients and 23 matched healthy controls having normal pure-tone averages with symmetrical hearing thresholds were included. Subjects were evaluated with 0.125 to 20 kHz pure-tone audiometry, Montreal Cognitive Assessment Test (MoCA), Tinnitus Handicap Inventory (THI), Visual Analog Scale (VAS), electroencephalography (EEG), and pupillometry. RESULTS: Pupil dilation and EEG alpha band in the "coding" phase of the sentence presented in tinnitus patients was less than in the control group (p < .05). VAS score was higher in the tinnitus group (p < .01). Also, there was no statistically significant relationship between EEG and pupillometry components and THI or MoCA (p > .05). CONCLUSION: This study suggests that tinnitus patients may need to make an extra effort to listen. Also, pupillometry may not be sufficiently reliable to assess listening effort in ANS-related pathologies. Considering the possible listening difficulties in tinnitus patients, reducing the listening difficulties, especially in noisy environments, can be added to the goals of tinnitus therapy protocols.

The mismatch negativity responses of individuals with tinnitus with normal extended high-frequency hearing-is it possible to use mismatch negativity in the evaluation of tinnitus?

OBJECTIVE: This study uses the multi-feature paradigm to compare the MMN responses of individuals with normal hearing thresholds, including the high frequencies with and without tinnitus. METHODS: Sixteen subjects with chronic subjective idiopathic tinnitus and twenty matched healthy controls were included in the study. Participants with hearing thresholds (0.125-16 kHz) less than 20 dB HL and MoCA test scores above 21 were included in the study. MMN responses and topographical maps of the responses resulting from the multi-feature MMN paradigm were recorded from 22 surface scalp electrodes. Amplitude and latency parameters of the MMN responses of five different deviants, consisting of frequency, intensity, duration, location, and silent gap, were compared between the two groups. RESULTS: The amplitudes of MMN responses were lower in the tinnitus group than in the control group at Fz electrode for all deviant types. At the same time, there was no difference between the groups for MMN latencies and, no correlation was found between THI and MMN. CONCLUSION: According to our results, the MMN might indicate a possible impairment in pre-attentive and automatic central auditory processing for chronic tinnitus patients. Since MMN responses in the tinnitus group differ from those of healthy individuals, it might be used as a reference for evaluating the central auditory pathways of tinnitus patients.

Heart Rate Variability During Nocturnal Sleep and Daytime Naps in Patients With Narcolepsy Type 1 and Type 2.

PURPOSE: Heart rate variability is a noninvasive measure of autonomic function. The aim of this study was to determine the risk of cardiovascular autonomic dysfunction during sleep in patients with narcolepsy. The effect of daytime napping was also examined in patients with narcolepsy type 1 and type 2. METHODS: Polysomnography recordings and multiple sleep latency tests from 11 patients with narcolepsy type 1 (N1) and 20 patients with narcolepsy type 2 (N2) were included and compared with 12 healthy controls. Heart rate variability values (measured by time- and frequency-domain parameters) were calculated using electrocardiography data from the polysomnography-multiple sleep latency test recordings. RESULTS: As an indicator of increasing sympathovagal imbalance, the low-frequency/high-frequency ratio was higher in all patients than in controls during non-rapid eye movement (NREM)-2 stage sleep (P ≤ 0.01). The root mean square of successive RR interval differences was lower (indicating parasympathetic tone) in N1 patients compared with N2 patients during REM sleep (P ≤ 0.04). In addition, decreased heart rate variability values were observed during sleep-onset REM-negative multiple sleep latency test periods compared with sleep-onset REM-positive periods. CONCLUSIONS: Heart rate variability abnormalities during sleep and the role of these changes on the development of cardiovascular diseases must be investigated in prospective follow-up studies of patients with narcolepsy. Heart rate variability changes during night sleep, daytime napping, and presence of sleep-onset REM periods may affect the life-threatening events.

A reduction of sleep spindles heralds seizures in focal epilepsy.

OBJECTIVES: Sleep has profound effects on epilepsy. It may alter the occurrence of interictal discharges (IEDs) and seizures. Vice versa, an active epilepsy changes sleep. Sleep spindles are typically associated with an increase of IEDs. We examined whether seizures change the number and power of spindles preceding nightly seizures. METHODS: We retrospectively examined the nightly EEG recordings of presurgical epilepsy patients from our EEG-video-monitoring unit. We evaluated the 200s before the EEG seizure onset for spindle density (spindles per minute) and spindle power and compared that to the interictal baseline sleep. RESULTS: The spindle density and the spindle power decreased significantly before the first seizure. The reduction before secondarily generalized seizures (8.7±2.5; p=0.001) was more pronounced than before focal seizures (10.5±2.5; p=0.003) compared to baseline (12.2±2.7). This finding was more pronounced in extratemporal lobe epilepsies than in temporal lobe epilepsies. The reduction of spindle power was also significant and was more pronounced in XTLE. These results were consistent for all other seizures during sleep, the mean spindle density decreased significantly in all focal (10.2±1.9; p=0.001) and generalized preictal period (8.8±2.4; p=0.001) compared to the mean interictal period (12.1±2.1). These were also more significant in XTLE than TLE group. CONCLUSIONS: Our data demonstrate that the occurrence of seizures and propensity of seizure generalisation in focal epilepsy is modulated by specific characteristics of light sleep such as sleep spindles. SIGNIFICANCE: This study supports the notion that changes in the epileptic network precede the seizure onset and have an influence on seizure generation and termination.

Event-related potentials to changes of rhythmic unit: differences between musicians and nonmusicians.

We investigated whether the expected differences between musicians and nonmusicians in their ability to detect a rhythm change were reflected in their event-related potentials (ERPs) and, if reflected, how these ERP differences associated with behavioral indices. Stimuli were three consecutive and equally spaced drum beats followed by a rest period to form a rhythmic unit (RU). By using three different inter-beat periods, three RUs were produced. Combinations of these RUs served as the "target/standard" pairs of an oddball sequence. In four different experiments, we tried two RU-change types each with two levels of detection difficulty. ERPs were recorded from the F3, Fz, F4, Cz and Pz scalp sites of 12 musicians and 12 nonmusicians. RT, hit and false-alarm rates were also measured. The data have shown with high statistical confidence that, associated with the musicians' better detection performance and shorter RTs, their ERP P3 to rhythm changes peaked significantly earlier and was significantly larger compared to nonmusicians. Intergroup ERP differences allowed above 90% correct classification. This study has also showed that not only violations of relatively complex musical regularities, but very simple rhythmic unit alterations could lead to significant P3 differences between musicians and nonmusicians. The high accuracy of the musician/nonmusician classification based only on their P3 data strongly supported the hypothesis that sensory and/or cognitive advantage of musicians in detecting rhythm changes does reflect in their P3.

Lateralisation of sound in temporal-lobe epilepsy: comparison between pre- and postoperative performances and ERPs.

OBJECTIVE: Our aim was to investigate if spatial hearing is impaired in mesial temporal lobe epilepsy and temporal lobectomy has an effect on this function. METHODS: Thirteen patients with mesial temporal lobe epilepsy (TLE) due to sclerosis in their left (n=6) or right (n=7) hippocampus were studied. Their sound lateralisation performance indexed by d' was tested against that of a group of normal subjects (n=13). Patients' ERPs to lateralisation shifts induced by interaural disparities of intensity (IID) and time (ITD) were also recorded. Eight of the patients were re-tested after they underwent anterior temporal lobectomy, which involved the resection/removal of medial structures including amygdala, hippocampus and parahippocampal gyrus. RESULTS: The sound-lateralisation performance of the TLE patients was significantly lower than normal subjects, and this disadvantage of the patients was specific to IID-based lateralisation. Amplitudes of their N1 and P2 responses to laterally shifting sounds were much lower than those reported previously for normal subjects. Lobectomy did not have a statistically significant effect on patients' sound-lateralisation performance nor on the amplitude of their auditory directional ERPs. CONCLUSIONS: The results show that especially the IID-based sound-lateralisation performance is impaired in TLE patients and that lobectomy should not cause any further deterioration. SIGNIFICANCE: This study suggests that a test for assessing the ability of sound lateralisation based on each of the IID and ITD cues should be included in the evaluation of TLE patients.

Changes in the alpha and beta amplitudes of the central EEG during the onset, continuation, and offset of long-duration repetitive hand movements.

Electroencephalographic alpha and beta activities recorded from central electrodes are known to display movement-related suppression or enhancement. We investigated whether the suppression that is known to occur during the onset of a single movement would persist or otherwise habituate when the movement is continuously repeated for a long period of time. Fourteen subjects took part in the experiments. They performed repetitive simultaneous extension-flexions of the fingers II-V in one hand, continuously for a period of at least 30 s. They then stopped this self-paced movement and rested for at least 30 s. Bipolar recording was made from C3-Cz and C4-Cz. Patterns of amplitude changes in the alpha and beta bands were calculated against a resting baseline. Following a bilateral alpha and beta suppression at the movement onset, alpha amplitude gradually but not fully recovered towards the baseline during the 30 s post-onset. Habituation of afferences and transfer of the cortical function were discussed as the two alternative explanations for this gradual recovery. Beta amplitude, however, displayed no recovery as long as the movement continued. Considering the relatively rapid beta recovery reported for sustained movements, this finding demonstrated that the sustained and continuous movements are conducted through quite different processes. A transient contralateral beta rebound was observed only after the end of the long movement period, strengthening the viewpoint that links the beta rebound with the closure of the cortical processes running throughout a motor sequence. Modulation of the beta amplitude, rather than the changes in alpha amplitude, appeared to be more closely correlated with the execution of a continuous movement.