Healthy controls without tinnitus or pain complaints

Objective signs of central sensitization by means of Quantitative Sensory Testing (mechanical and heat detection and pain thresholds, endogenous pain facilitation and inhibition)

• Audiometry Performance of pure tone audiometry according to the modified Hughson-Westlake method
• Tinnitus analysis Measurement of psychoacoustic features of tinnitus, including (1) tinnitus pitch, (2) loudness, (3) masking ability, and (4) residual inhibition.
• Uncomfortable Loudness measures Performance of Uncomfortable Loudness measurements to evaluate the presence of hyperacusis. .

Evaluation of cognitive functioning by means of:

• Auditory Stroop test
• Detecting letters task
• Letter-number sequencing task

Evaluation of listening effort by means of the modified version of the behavioral listening effort test based on a dual-task paradigm by Degeest, Keppler & Corthals (2018) .

Evaluation of psychological factors by means of:

• Depression, Anxiety and Stress Scale (DASS-21)
• Beck Depression Inventory (BDI)
• Big Five Inventory (BFI)
• Connor-Davidson Resilience Scale

Evaluation of lifestyle factors by means of:

Baecke Questionnaire Pittsburg Sleep Quality Index Insomnia Severity Index Stress subscale of the DASS 21

Evaluation of self-reported pain processing by means of the Pain Catastrophizing Scale

Self-reported quality of life by means of the SF-36 questionnaire

Evaluation of self-reported tinnitus severity and impact on daily life by means of the Tinnitus Functional Index

Evaluation of self-reported characteristics of hyperacusis by means of the Hyperacusis Questionnaire

Evaluation of self-reported tinnitus characteristics by means of the Tinnitus Sample Case History Questionnaire

Evaluation of self-reported neck pain related disability using the Neck Disability Index

Heat stimuli are given using the CHEPS PATHWAY system (Medoc). This probe is placed on the skin at the 5 standardized locations. It provides a heat stimulus that rises at a rate of 1°C/second.

Using a dual response button, the participant has to indicate when the heat sensation changes into a pain sensation by pressing a blue button (detection threshold). The temperature keeps rising after the blue button is pressed. If the patient scores the pain sensation resulting from the heat stimulus as a 6/10 on the NRS they have to press the red button. At that moment, the temperature of the thermode goes back to the baseline temperature of 32°C. When the baseline temperature is reached, a second heat stimulus is given after a 15 second break. 3 consecutive trials will be performed.

This protocol is performed at 5 standardized body locations, being: C5-C cervical joint, N. Trigeminus, M. Masseter, M. Extensor carpi radialis longus, M. Tibialis Anterior

Temporal Summation is performed with the Contact Heat-Evoked Potential Stimulator (CHEPS) model. Temporal summation is evaluated at the M. tibialis anterior and the M. extensor carpi radialis longus.

The temperature corresponding with the mean score of the 6/10 NRS score (heat pain threshold) from the corresponding body part is used as the painful stimulus. Ten stimuli from the same heat are given to the participant with a thermode. After stimulus 1, 5 and 10 a beep sound is heard. At these moments the participant has to score the pain that they experience from the previous stimulus on the NRS from 0 to 10. Between stimuli the temperature goes back to the baseline temperature of 32°C. The velocity of the heating is 70°C/second and the velocity of the cooling down is 40°/second. Each stimulus is 0.5 seconds long with a frequency of 0.5 Hz.

Conditioned pain modulation is tested by asking the participant to put their non- non-dominant or non-painful dominant hand (up to the wrist joint) in a water bath of 45,5°C for 1 minute. This is the conditioning stimulus. After this, a PPT measurement is performed to measure pressure detection and pain thresholds again, at the level of the M. extensor carpi radialis longus. Two consecutive measurements of the PPTs are being performed with a 30 seconds interval in between. Thereafter, the non-dominant or non-painful hand is placed in the hot water for another minute and after this minute, heat detection and pain thresholds are evaluated again at the M. extensor carpi radialis longus. Both pressure and heat are the testing stimulus.

Also, the NRS score (0-10) for the water was asked to know if they perceived the water as a high enough pain stimulus.

The Central Sensitization Inventory measures the somatic and emotional symptoms commonly associated with central sensitization. It consists of two parts, one measuring 25 symptoms, the other asks whether patients have been previously diagnosed with ten specific diagnoses. A cut off of 40 out of 100 is used to determine the presence of self-reported signs of central sensitization (the higher the score, the higher the severity).

Three negative emotional dimensions: 'depression', 'anxiety' and 'stress were evaluated using the self-report Depression Anxiety and Stress Scale 21 (DASS21), which is a short version of the DASS.The total score ranges between 0 and 126 and higher scores indicate more severe negative emotional status.

The Dutch version of the Beck Depression Inventory (BDI) was used for the assessment of depression. The total score of the BDI ranges between 0 and 63 and higher scores reflect more severe depression.

The Dutch version of the Connor-Davidson Resilience Scale 25 (CD-RISC 25) was used to assess resilience, which is a measure of stress coping ability. The total score ranges between 0 and 100 and a higher score reflects greater resilience.

The Big Five Index 2 (BFI-2) was used to quantify five traits of personality, namely agreeableness, conscientiousness, extraversion, neuroticism, and openness. The BFI-2 consists of 15 facets, describing different features of each trait

Self-reported physical activity levels were evaluated using the Baecke Physical Activity Questionnaire. This questionnaire consists of 16 items assessing three different domains of physical activity: work, sports and leisure time. The total score varies between 3 and 15 with a higher score reflecting a greater level of physical activity.

The Pittsburgh Sleep Quality Index (PSQI) was used to evaluate self-perceived overall sleep quality in 7 domains: subjective sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbance, sleep medication, and daytime dysfunction over the previous month. The maximal score ranges between 0 and 21, and a global score of 5 or higher indicates clinically significant sleep problems

The Insomnia Severity Index (ISI) was used to assess the patient's perception of insomnia severity. The ISI consists of seven items assessing the severity of sleep onset and sleep maintenance difficulties (both nocturnal and early morning awakenings), satisfaction with current sleep pattern, interference with daily functioning, notice ability of impairment attributed to the sleep problem and degree of distress or concern caused by the sleep problem. The maximal score ranges between 0 and 28 and higher scores indicate more severe insomnia.

Self-reported health-related quality of life will be evaluated using the SF- 36. This self-report questionnaire consists of 36 items that can be clustered into eight subscales: physical functioning, role limitations due to physical problems, bodily pain, general health, vitality, social functioning, role limitations due to emotional problems, and mental health. The summation of all subscales provides the total score (0-800).

The Dutch version of the Neck Disability Index (NDI) will be used to evaluate the level of self-reported pain-related disability. The NDI consists of 10 items and has a total score of 50. Higher NDI scores reflect higher levels of neck pain-related disability. A score between 0 and 4 reflects no disability, a score between 5 and 14 indicates mild disability, between 15 and 24 moderate disability, between 25 and 34 severe disability and > 35 is considered as complete disability. (

Neck pain catastrophizing will be assessed using the Dutch Pain Catastrophizing Scale (PCS), which is a self-report questionnaire to evaluate the presence of catastrophic thoughts and feelings towards pain. The PCS consists of 13 items and has a maximal score of 52. Higher scores indicate higher levels of pain catastrophizing. The PCS includes three subscales; magnification (experiencing pain as a threat), rumination (repeated worrying), and helplessness (believing that nothing can resolve the pain).

The Dutch validated version of the Tinnitus Sample Case History Questionnaire (TSCHQ) will be used for the standardized collection of information regarding the tinnitus history, tinnitus characteristics, modulating factors and other symptoms such as neck pain or headache.

The Dutch validated version of the Tinnitus Functional Index (TFI) will be used to evaluate tinnitus impact. The TFI is a 25-item self-report questionnaire with a total score ranging between 0 and 100, which consists of eight different subscales (intrusiveness, cognition, sleep, sense of control, relaxation, emotional, auditory and quality of life subscales). The higher the score, the higher the tinnitus impact.

The Dutch version of the Hyperacusis Questionnaire (HQ) will be used for the quantification and characterization of hyperacusis. The HQ consists of 14 items with a total score ranging between 0 and 42, a score greater than 28 is considered to represent auditory hypersensitivity or hyperacusis.

The Auditory Stroop test will be used to measure cognitive flexibility and inhibition.

The detecting letters-task (COTESS) will be used to test the participant's attention span.

The letter-number sequencing task is part of the Wechsler Adults Intelligence Scale (WAIS-IV-NL) and will be used to evaluate verbal working memory capacity and processing speed.

A modified version of the behavioral listening effort test based on a dual-task paradigm by Degeest, Keppler & Corthals (2018) will be used. The test consists of a primary and secondary task that will be administered separately (baseline condition) and simultaneously ( dual-task condition).