The differences in brain activity between narrow band noise and pure tone tinnitus

Abstract

Background: Tinnitus is an auditory sensation characterized by the perception of sound or noise in the absence of any external sound source. Based on neurobiological research, it is generally accepted that most forms of tinnitus are attributable to maladaptive plasticity due to damage to auditory system. Changes have been observed in auditory structures such as the inferior colliculus, the thalamus and the auditory cortex as well as in non-auditory brain areas. However, the observed changes show great variability, hence lacking a conclusive picture. One of the reasons might be the selection of inhomogeneous groups in data analysis.

Methodology: The aim of the present study was to delineate the differences between the neural networks involved in narrow band noise and pure tone tinnitus conducting LORETA based source analysis of resting state EEG.

Conclusions: Results demonstrated that narrow band noise tinnitus patients differ from pure tone tinnitus patients in the lateral frontopolar (BA 10), PCC and the parahippocampal area for delta, beta and gamma frequency bands, respectively. The parahippocampal-PCC current density differences might be load dependent, as noise-like tinnitus constitutes multiple frequencies in contrast to pure tone tinnitus. The lateral frontopolar differences might be related to pitch specific memory retrieval.

Figure 1. EEG power in tinnitus patients for narrow band noise tinnitus patients, pure tone tinnitus patients and control subjects, averaged over all electrodes.

Figure 2. Electrode comparison of power spectra for narrow band noise tinnitus patients, pure tone tinnitus patients and control subjects.

Figure 3. sLORETA contrast analysis between Narrow-Band-Noise versus Pure Tone tinnitus (p<.05).

Decreased activity within Delta (1–3.5 Hz; Top Panel) in the prefrontal cortex (BA10), and increased activity within Beta (25–30 Hz; Middle Panel) and Gamma (30.5–45 Hz; Bottom Panel) in respectively posterior cingulate cortex (PCC; BA23) and the right parahippocampal area (BA35) for patients presenting with bilateral narrow band tinnitus in comparison to bilateral pure tone tinnitus.

Figure 4. sLORETA contrast analysis between Narrow-Band-Noise tinnitus patients versus Control subjects (p<.05).

Increased activity within Beta (25–30 Hz; Top Panel) in the posterior cingulate cortex (PCC; BA31) and Gamma (30.5–45 Hz; Bottom Panel) in the right and left parahippocampal areas (BA35) for bilateral narrow band tinnitus in comparison to controls.

Figure 5. sLORETA contrast analysis between Pure Tone tinnitus patients versus Control subjects (p<.05).

Increased activity within Beta (25–30 Hz; Top Panel) and Gamma (30.5–45 Hz; Bottom Panel) in the posterior cingulate cortex (PCC; BA31) for patients with bilateral pure tone tinnitus in comparison to controls.