11Attention, Salience and the Default-Mode Network

FAttention amplifies the phantom

Attention is a volume control. Directing attention toward a sound enhances its cortical representation; directing it away suppresses it. In tinnitus this ordinary mechanism turns pathological: the more the brain monitors the phantom sound, the more salient and intrusive it becomes, in a self-reinforcing loop [2013].

This is why tinnitus seems loudest in silence and at night, when no competing signal pulls attention away, and why patients who can engage absorbing tasks report the sound “disappearing.” Behavioural and imaging work shows that people with tinnitus have measurable alterations in attentional performance and in the brain networks that allocate attention [2015].

TThe salience network: deciding the sound matters

The salience network — anchored by the anterior insula and dorsal anterior cingulate cortex — tags incoming events as important and worth acting on. In tinnitus this network repeatedly flags the phantom sound as relevant, recruiting emotional and attentional resources to a signal that carries no information [2021].

The salience network is also the switch that toggles the brain between an internally focused resting state and externally directed task engagement. When it is captured by tinnitus, that switching is disrupted, helping explain the concentration difficulties and the sense that the sound “won’t let go” [2013].

TDefault-mode network disruption

The default-mode network (DMN) — medial prefrontal cortex, posterior cingulate/precuneus and angular gyrus — is normally active during rest and mind-wandering and deactivates when a task demands attention. In tinnitus this orderly deactivation is impaired: the phantom percept intrudes on the resting brain and prevents it from settling [2013].

Resting-state studies show altered connectivity within the DMN and between the DMN, attention and auditory networks in tinnitus, with the precuneus emerging as a hub whose coupling tracks symptom severity [2015]. The clinical correlate is the patient who cannot relax, whose mind is never quiet because the sound co-opts the network meant for rest.

CThe triple-network framework

These observations converge on a triple-network model: tinnitus reflects an imbalance among the salience network, the central-executive (attention) network and the default-mode network. The salience network over-flags the percept; the executive network is repeatedly pulled to it; and the default-mode network cannot deactivate, so the brain never returns to quiet baseline [2021].

This framework is directly relevant to habituation and CBT. Habituation is precisely the process of the salience network learning to stop flagging the sound; CBT and mindfulness retrain attentional allocation and restore normal DMN deactivation. The triple-network view therefore supplies a mechanistic rationale for why psychological therapies work even when the auditory signal is unchanged [2013].