A database based on electroencephalography to study the effects of acoustic therapies for the treatment of tinnitus
Tinnitus is a multifactorial and heterogeneous condition strongly associated with hearing loss (HL), age, sex, marital status, education and even employment. Additionally, a large number of people with tinnitus (about 65%) eventually experience sleep disturbances, emotional and cognitive distress (eg, stress, anxiety, or depression), or some other mental condition.1. In fact, about 70% of tinnitus cases are preceded by a mental disorder. Patients with very distressing tinnitus may additionally have cardiovascular, endocrine or metabolic diseases2.
Tinnitus is a heterogeneous condition with no effective standard treatment. A recent study3 based on a survey conducted by the web platform Tinnitus Hub, in which 5,017 tinnitus sufferers participated, seven of the 25 most widely used treatments were sound-based therapies. From the most applied therapies to the least applied, they are: 1st sound self-stimulation, 6e masker 11e Tinnitus Rehabilitation Therapy (TRT), 18e jagged music, 19e sound cure, 20e acoustic neuromodulation, and 21st neuromonic. As can be seen, almost a third of the treatments currently available for tinnitus depend on the effect of sound on the functioning of the body. It is well established that sound causes physiological, cognitive and psychological changes4. However, it is still unclear how sound-based treatment alleviates or alleviates tinnitus, and what is the appropriate therapy for each clinical case due to its heterogeneous nature.
To measure the sound effects of acoustic therapies on tinnitus, electroencephalographic (EEG) monitoring has been proposed. In5, the authors presented a review of computational methods for analyzing EEG signals to assess the sound effects of acoustic therapies at the cortical level. Over the past two years, acoustic therapies that have been evaluated are (1) neuromodulation, (2) auditory residual inhibition, (3) binaural beat therapy (BBT), and (4) auditory discrimination therapy. (ADT). In the first case6, neuromodulation therapy was applied for 75 days and EEG monitoring was performed every two weeks. It was found that the level of EEG connectivity decreased significantly. In the second case, auditory residual inhibition did not significantly reduce tinnitus intensity, and this finding was supported by EEG evidence since band power in alpha and gamma increased in amplitude.seven. Similarly, alpha band strength in auditory areas increased during auditory residual inhibition in the study conducted in8. In the third case, BBT reduced stress (23% of patients) and tinnitus perception (15% of patients), and slightly reduced EEG synchronicity on the right frontal lobe9. In the latter case, the level of EEG synchronicity due to auditory processing decreased due to attentional redirection achieved by ADTten.
As can be seen in previous studies, EEG analysis is a useful tool to assess the sound effects of acoustic therapies, in addition to psychoacoustic and clinical assessments. For this reason, the present database provides demographic, clinical, psychometric, and EEG information from 89 tinnitus sufferers who were randomly treated for eight weeks with one of five acoustic therapies. These were (1) relaxing music (placebo), (2) tinnitus retraining therapy (TRT), (3) ADT, (4) enriched acoustic environment (EAE), and (5) BBT. TRT seeks to reduce tinnitus by reducing the perceived loudness of unreal sound11.12. ADT aims to redirect the patient’s attention to the therapy by presenting a sound composed of standard and deviant pulses in a random pattern, and thus reducing the perception of tinnitus13. EAE intends to prevent HL and subsequent changes in the plastic tonotopic cortical map after acoustic trauma. EAE is based on a sequence of random frequency tones with an amplitude proportional to the HL reported on the patient’s audiometry14. BBT consists of two pure tones presented to each ear, having a frequency difference depending on the target oscillatory EEG band. Use of this therapy has reported reduction in stress levels by reducing activation of areas of the sympathetic system15, which in turn reduces the perception of tinnitus. In addition to the 89 tinnitus sufferers, 14 healthy volunteers were recruited, exposed to relaxing music (identical to the control group) and followed the same experimental procedure as the tinnitus sufferers.
In total, the database contains four types of information sources from 103 participants. See Table 1. First, ddemographic information refers to place of residence, gender, age (over 18) and nationality. Second, itclinical history includes the HL level, as well as the frequency, laterality and intensity of tinnitus perception. To finish, psychometric and EEG follow-up acoustic therapies is also included. It is important to note that the initial cohort was 108 participants, 103 of them were included in the study and 71 of them completed the experimental procedure. See Figs. 1.
Psychometric monitoring was based on the Spanish version of Hospital Anxiety and Depression Stress (HADS) and Tinnitus Handicap Inventory (THI), which provided the psychoacoustic effect of acoustic therapies. On the one hand, the HADS questionnaire evaluates the impact of tinnitus on anxiety and depression16. On the other hand, the THI questionnaire measures the degree of perception of tinnitus; emotional, physical and social response to tinnitus; and intrusiveness of tinnitus to hearing17. Further details regarding the questionnaire follow-up of this study protocol can be found in18.
EEG information provides insight into neuroplastic changes (if any) from acoustic therapies. The available EEG datasets allow signal analysis to be undertaken in three modes: spontaneous, evoked and induced EEG activity. In most previous studies, only spontaneous activity was analyzed, i.e., participants were either at rest or listening to their acoustic therapy. However, EEG signals provide deeper neural information when linked to specific motor, emotional, sensory, perceptual and/or cognitive events. These are evoked and induced EEG activity. The traditional models of evoked and induced EEG activity are event-related potentials and event-related (de-)synchronization, which can be estimated from the present database. The analysis of spontaneous activity makes it possible to assess the nature of the activity in progress. In contrast, the analysis of evocation and induced activity allows the study of brain responses when individuals perceive the sound, pay attention to the stimulus, make a decision and act accordingly. Briefly, the bottom-up and top-down mechanisms associated with neuroplastic changes due to acoustic rehabilitation can be studied using the present database.
This database was created following a protocol previously approved by the Ethics Committee of the National School of Medicine of the Tecnologico de Monterrey, described and published in19, and registered under trial number: ISRCTN14553550. The database is available at20.
The study protocol proceeded as follows. All participants were informed about the experimental procedure and signed a consent form, where they authorized the publication of their collected data and the results of their follow-ups. Most of the patients were recruited from the National Institute of Rehabilitation, and they were further informed that their chief physician was also monitoring the survey. Chief physicians provided clinical histories and patient demographics.
All patients who agreed to participate in the study were assigned to one of five groups: (1) TRT, (2) EAE, (3) ADT, (4) BBT, and (5) placebo. Patients without severe HL were randomly assigned to the placebo and EAE groups. On the other hand, patients with a well-identified tinnitus pitch were included in the TRT or ADT groups. Patients with tinnitus below 1 kHz were assigned to BBT. The control group (healthy volunteers) was asked to use the same relaxing music as the placebo group. On average, 17 volunteers were assigned per group (see Table 1). Note that each acoustic therapy was adjusted for HL level, frequency, and tinnitus intensity, with the exception of relaxing music which was used as a placebo.
All participants (with and without tinnitus) were asked to use the corresponding acoustic therapy for one hour every day, at any time of the day, for eight weeks. The therapy was followed four times during the two months: the first (session 1), the third (session 2), the fifth (session 3) and the eighth (session 4) week after initiating the therapy. At each monitoring session, the THI and HADS questionnaires were applied and an EEG recording was performed, as shown in Fig. 2. It can be seen in Fig. 1 that only 71 of 103 participants completed the experimental procedure. Although the repository contains 103 files, not all of them are complete. This information is specified in the Excel file present in20.