Tinnitus perception and distress is related to abnormal spontaneous brain activity as measured by magnetoencephalography

Abstract

Background: The neurophysiological mechanisms underlying tinnitus perception are not well understood. Surprisingly, there have been no group studies comparing abnormalities in ongoing, spontaneous neuronal activity in individuals with and without tinnitus perception.

Methods and findings: Here, we show that the spontaneous neuronal activity of a group of individuals with tinnitus (n = 17) is characterised by a marked reduction in alpha (8-12 Hz) power together with an enhancement in delta (1.5-4 Hz) as compared to a normal hearing control group (n = 16). This pattern was especially pronounced for temporal regions. Moreover, correlations with tinnitus-related distress revealed strong associations with this abnormal spontaneous activity pattern, particularly in right temporal and left frontal areas. Overall, effects were stronger for the alpha than for the delta frequency band. A data stream of 5 min, recorded with a whole-head neuromagnetometer under a resting condition, was sufficient to extract the marked differences.

Conclusions: Despite some limitations, there are arguments that the regional pattern of abnormal spontaneous activity we found could reflect a tinnitus-related cortical network. This finding, which suggests that a neurofeedback approach could reduce the adverse effects of this disturbing condition, could have important implications for the treatment of tinnitus.

Figure 1. Power Spectra Averaged over All Sensors Show a Reduced Alpha Peak in Participants with Tinnitus and an Enhancement for Delta

The sharp peak centred at 16 2/3 Hz represents technical noise resulting from the 1-km-distant railway system.

Figure 2. Difference Maps between Participants with Tinnitus and Controls for Alpha and Delta

The results suggest that areas for which alpha reduction and delta enhancements are found partly overlap. Overall, the effect for the alpha band is considerably stronger (note that for this reason the scaling ranges are chosen differently).

Figure 3. Display of the Group × Frequency Band Interaction Effects Averaged over Temporal Sources

Effects for right (A) and left (B) temporal cortex, where the strongest enhancements of alpha and reductions of were found.

Figure 4. Correlation Map between Alpha, Delta, and Tinnitus-Related Distress

Since previous analyses (see Figure 3) implicated corresponding areas for the effects found for alpha and delta, tinnitus-related distress was additionally correlated with a frequency index ([delta – alpha]/[delta + alpha]; bottom panel). Effects are largest for right temporal and left frontal sources.