Tinnitus Intensity Dependent Gamma Oscillations of the Contralateral Auditory Cortex

Non-pulsatile tinnitus is considered a subjective auditory phantom phenomenon present in 10 to 15% of the population. Tinnitus as a phantom phenomenon is related to hyperactivity and reorganization of the auditory cortex. Magnetoencephalography studies demonstrate a correlation between gamma band activity in the contralateral auditory cortex and the presence of tinnitus. The present study aims to investigate the relation between objective gamma-band activity in the contralateral auditory cortex and subjective tinnitus loudness scores. In unilateral tinnitus patients (N = 15; 10 right, 5 left) source analysis of resting state electroencephalographic gamma band oscillations shows a strong positive correlation with Visual Analogue Scale loudness scores in the contralateral auditory cortex (max r = 0.73, p<0.05). Auditory phantom percepts thus show similar sound level dependent activation of the contralateral auditory cortex as observed in normal audition. In view of recent consciousness models and tinnitus network models these results suggest tinnitus loudness is coded by gamma band activity in the contralateral auditory cortex but might not, by itself, be responsible for tinnitus perception

Correlation between Independent Components of scalp EEG and intra-cranial EEG (iEEG) time series

International audience19 scalp electrode (EEG) and 8 intra-cranial electrode (iEEG) are recorded simultaneously with a common reference. EEG data is subjected to independent component analysis (ICA) and localisation of components in grey matter is estimated by the sLORETA inverse solution. Correlation between the time series of two independent components and intra-cranial recordings is very high (computed over 23552 samples, max r = 0.8 and 0.67, respectively). One component is localized underneath the site of the implanted electrode. These findings were replicated using the second row of 8 iEEGs and an independent 19-electrode EEG recording, validating the source localisation provided by combining ICA and sLORETA

The Differences in Brain Activity between Narrow Band Noise and Pure Tone Tinnitus

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 memor