In this chapter, our goal is to provide a comprehensive exploration of TMS in psychiatric treatment. This includes an overview of the fundamental principles and common parameters of TMS, as well as advanced techniques and approaches used in clinical practice. We will also discuss treatment procedures, key precau­tions, underlying mechanisms, and factors inuencing the efcacy of TMS.Through this examination, we aim to offer a thorough understanding of how TMS is utilized to address various psychiatric conditions and optimize therapeutic outcomes.

According to Faraday’s law of electromagnetic induction, the changing magnetic eld induces an electric eld in the conductive tissue of the cerebral cortex. This electric eld, in turn, generates an induced current in the neurons. When the induced current affects the neurons, it alters their membrane potential. If the membrane potential reaches the depolarization threshold, voltage-gated sodium channels open, allowing sodium ions to inux and triggering an action potential, thereby increasing neuronal excitability. Conversely, if the membrane potential is hyperpolarized, neu­ronal excitability is reduced [5].

Prolonged intermittent theta burst stimulation represents a special stimulation para­digm. It is based on the principle of theta burst stimulation (TBS), which involves pulse-train stimulation at a theta wave frequency (in the range of 4–7Hz). Moreover, piTBS further extends the stimulation duration based on intermittent TBS.From a neurophysiological perspective, this stimulation modality exhibits potential advan­tages in inducing brain plasticity. It can more effectively modulate the connection strength between brain neurons [7].

Deep transcranial magnetic stimulation has the capacity to generate a stronger mag­netic eld, enabling it to penetrate deeper into brain tissues. The enhanced magnetic eld strength of dTMS is achieved through specic coil designs and engineering optimizations [9]. These modications allow for a more focused and intense mag­netic eld that can overcome the attenuation and scattering effects as the magnetic eld penetrates the overlying brain layers and skull. Studies have demonstrated that dTMS can have differential effects on neural circuits within deeper brain regions, potentially modulating neurotransmitter release and synaptic plasticity in a distinct manner compared to supercial TMS [10].

Priming (guiding) transcranial magnetic stimulation likely utilizes an initial appli­cation of a weak or specic patterned magnetic stimulation to “prime” the neural response mechanisms in the brain, thereby creating favorable conditions for sub­sequent more effective stimulation or neuromodulation procedures.

Synchronized transcranial magnetic stimulation (sTMS) involves the synchronization of magnetic stimulation with the natural rhythms of the brain (such as brainwaves). From the perspective of the precision of neuromodulation, this synchronized stimula­tion modality can more precisely target the temporal windows of brain neural activity, thereby enhancing the stimulation effect [13]. Additionally, it may potentially enhance the treatment efcacy for cognitive dysfunction. Evidence has shown that sTMS syn­chronized with specic brain rhythms can modulate the synchronization and coher­ence of neural networks, leading to improved cognitive performance and potentially therapeutic benets in patients with cognitive impairments [14].

3. Bilateral TBS: Bilateral theta burst stimulation is an advanced form of TMS that

applies theta burst protocols to both the left and right dorsolateral prefrontal cortex (DLPFC). It involves the simultaneous or sequential delivery of intermit­tent or continuous theta burst stimulation, which modulates neuronal excitability and functional connectivity in these key brain regions. Bilateral TBS has shown promising therapeutic potential in treating mood disorders, such as depression, by enhancing neuroplasticity and restoring balance in dysregulated neural cir­cuits. As a noninvasive neuromodulation technique, it offers a novel alternative to traditional pharmacological interventions, particularly for patients with treat­ment-resistant conditions [17, 18].

TMS involves several key parameters that determine its effects on neural activity. Stimulation frequency is a crucial factor. High-frequency TMS (>1Hz) typically increases neuronal excitability and may induce long-term potentiation (LTP)-like effects, while low-frequency TMS (<1Hz) usually decreases excitability, similar to long-term depression (LTD) mechanisms. Intensity, measured in percentage of the maximum stimulator output, inuences the depth and extent of neural activation. Pulse width, which is the duration of each individual magnetic pulse, affects the energy delivered and the resulting electric eld in the brain. The number of pulses per session and the total number of sessions over a treatment course also play sig­nicant roles in modulating neural plasticity and achieving therapeutic outcomes. Additionally, the coil design, such as gure-of-eight or circular, determines the focality and distribution of the magnetic eld, thereby impacting the specic brain regions targeted. Precise control and optimization of these common parameters are essential for both research applications and clinical effectiveness of TMS.

Pretreatment preparation includes gathering the patient’s medical history, conduct­ing physical and neurological exams, and obtaining informed consent after explain­ing the TMS process, risks, and discomforts. Patient positioning is essential, with the patient sitting comfortably, ensuring proper head and neck support, and adjust­ing the head for accurate coil placement on the target area.

To minimize seizure risk during TMS, patients with a history of epilepsy or seizure disorders must undergo thorough screening, including seizure type, frequency, and current antiepileptic treatment. Stimulation parameters should be carefully man­aged, limiting frequency (usually <20–30Hz), titrating intensity, and controlling pulse count and duration to reduce seizure risk.

Other precautions include screening for metallic implants, particularly ferromag­netic materials, as they may interact with the magnetic eld. TMS during pregnancy and lactation is generally avoided due to insufcient safety data, and should only be considered with a multidisciplinary assessment if benets outweigh risks.

TMS-induced currents modulate neuronal membrane potential [20]. Depolarization elevates the membrane potential to threshold, initiating an action potential and enhancing neuronal excitability. Conversely, hyperpolarization lowers the mem­brane potential, reducing the likelihood of reaching threshold and decreasing neuro­nal excitability.

Ion channels on the neuronal membrane are pivotal in modulating excitability changes induced by TMS.Voltage-gated sodium channels (Nav) facilitate action potential generation upon depolarization, allowing sodium inux [21]. In GABA­ergic neurons, TMS may inuence chloride channels, such as the GABAA receptor