Causal network localization of brain stimulation targets for trait anxiety

Deep Brain Stimulation in the Bed Nucleus of Stria Terminalis and Medial Forebrain Bundle in Two Patients With Treatment-Resistant Depression and Generalized Anxiety Disorder-A Long-Term Follow-Up

This case report presents positive outcomes from deep brain stimulation (DBS) targeting the bed nucleus of the stria terminalis (BNST) in two patients with treatment-resistant depression and generalized anxiety disorder. DBS effects in the medial forebrain bundle (MFB) area were unclear. Further research into DBS's efficacy when comorbid anxiety is present is required.

Personalised transcranial magnetic stimulation for treatment-resistant depression, depression with comorbid anxiety and negative symptoms of schizophrenia: a narrative review

ABSTRACT

Transcranial magnetic stimulation (TMS) is a promising intervention for treatment-resistant psychiatric disorders. However, conventional TMS typically utilises a one-size-fits-all approach when determining stimulation targets. Recent retrospective brain circuit-based analyses using lesion network mapping have suggested that a left dorsal lateral prefrontal cortex target has a higher efficacy for alleviating depression symptoms, a dorsomedial prefrontal cortex target is more effective for anxiety symptoms, and a rostromedial prefrontal cortex target is effective for schizophrenia-associated psychiatric symptoms. Nonetheless, symptom-specific brain circuit targeting has not been tested prospectively. We conducted a narrative review of selected literature to investigate individualised targeting for TMS and discuss potential future directions to elucidate the efficacy of this approach.

Mechanisms of Action of TMS in the Treatment of Depression

Transcranial magnetic stimulation (TMS) is entering increasingly widespread use in treating depression. The most common stimulation target, in the dorsolateral prefrontal cortex (DLPFC), emerged from early neuroimaging studies in depression. Recently, more rigorous casual methods have revealed whole-brain target networks and anti-networks based on the effects of focal brain lesions and focal brain stimulation on depression symptoms. Symptom improvement during therapeutic DLPFC-TMS appears to involve directional changes in signaling between the DLPFC, subgenual and dorsal anterior cingulate cortex, and salience-network regions. However, different networks may be involved in the therapeutic mechanisms for other TMS targets in depression, such as dorsomedial prefrontal cortex or orbitofrontal cortex. The durability of therapeutic effects for TMS involves synaptic neuroplasticity, and specifically may depend upon dopamine acting at the D1 receptor family, as well as NMDA-receptor-dependent synaptic plasticity mechanisms. Although TMS protocols are classically considered 'excitatory' or 'inhibitory', the actual effects in individuals appear quite variable, and might be better understood at the level of populations of synapses rather than individual synapses. Synaptic meta-plasticity may provide a built-in protective mechanism to avoid runaway facilitation or inhibition during treatment, and may account for the relatively small number of patients who worsen rather than improve with TMS. From an ethological perspective, the antidepressant effects of TMS may involve promoting a whole-brain attractor state associated with foraging/hunting behaviors, centered on the rostrolateral periaqueductal gray and salience network, and suppressing an attractor state associated with passive threat defense, centered on the ventrolateral periaqueductal gray and default-mode network.