Transcranial magnetic stimulation is a non-invasive method used to stimulate small regions of the brain. It relies on electromagnetic induction to produce electric currents that can modulate neuronal activity. The technological advancements behind TMS have opened new avenues for clinical and research applications, ranging from therapy outcomes in depression to insights into motor cortex physiology. However, a nuanced understanding of how different TMS coil designs affect stimulation efficacy has remained elusive until now.

This study meticulously evaluates various TMS coil configurations, including figure-eight and circular types, in an effort to decode their specific influences on phosphene induction. Phosphenes are sensations of light that occur when the visual cortex is stimulated, even in the absence of visual stimuli. Understanding how different coil designs alter phosphene thresholds is vital, as it provides critical insights into the functional state of the motor cortex, which is essential for both clinical and research paradigms.

The findings reveal that the figure-eight coil, known for its focal stimulation capabilities, elicited significantly lower phosphene thresholds compared to the circular coil, which offers a more diffuse stimulation profile. This suggests that the figure-eight coil is more effective at targeting the motor cortex precisely, raising important implications for both the therapeutic and experimental use of TMS. The ability to modulate excitation levels with greater accuracy could lead to more reliable interventions for neurological disorders.

Moreover, the study further investigates the relationship between phosphene thresholds and overall motor cortex excitability. It posits that as thresholds decrease, indicating enhanced cortical excitability, there is a corresponding increase in the efficacy of motor neuron activation. This vital link could serve as a new measure for assessing the operational capacity of central nervous system functions, which is incredibly pertinent for conditions such as epilepsy, stroke recovery, and neurological rehabilitation.

An additional layer of complexity arises when considering individual variability in response to TMS. The authors adeptly highlight the necessity of personalized approaches to TMS protocol settings based on individual neurophysiological characteristics. This revelation underscores the broader trend towards precision medicine, where treatment strategies are tailored to the unique profiles of patients rather than applying a one-size-fits-all model.

The implications of this research stretch far beyond merely improving TMS protocols for research purposes. Enhanced understanding and application of TMS could translate into novel therapeutic interventions for a diverse array of neuropsychiatric conditions, including depression, anxiety, and chronic pain syndromes. Furthermore, the potential integration of these findings into routine clinical practices may signal a transformative shift in how we approach neurorehabilitation.

As advancements in neurotechnology continue to burgeon, the study highlights the necessity for further research to establish standardized guidelines that govern TMS application in clinical settings. This call to action resonates with the broader scientific community, advocating for collaborative efforts to foster interdisciplinary dialogue between neuroscientists, clinicians, and engineers alike.

In light of the findings, the study effectively underscores the critical role that methodological considerations play in TMS applications. With technology rapidly advancing, there is an ever-growing need for innovative coil designs, ensuring that researchers and clinicians have the tools necessary to maximize the efficacy of TMS interventions.

Vibrant discussions are already emerging across academic platforms as researchers digest these findings and consider the implications for their works. The community’s engagement can potentially accelerate innovations and applications, driving forward the frontiers of neuroscience and expanding our understanding of complex brain dynamics.

As interest surges in TMS and its utility in understanding brain function and disorders, this study serves as a cornerstone for future explorations. The quest to unlock the mysteries of brain activity via TMS may lead to potent interventions, fundamentally altering how we treat various neuropsychiatric conditions and ultimately enhancing patient outcomes.

Moreover, the synergetic relationship between technology and neuroscience may catalyze the development of new paradigms in cognitive rehabilitation. Consequently, this research is poised to spark discussions that may shape the trajectory of future studies and therapeutic approaches, demonstrating the profound impact that understanding TMS coil functions can have on neuroscience.

In conclusion, the work conducted by Fidancı and colleagues not only enriches the current body of knowledge surrounding TMS but also sets a precedent for continuous exploration of TMS applications. Scientists and clinicians alike are now urged to reconsider established protocols in light of new evidence, rekindling excitement about the evolving capabilities of neurostimulation technologies.

Subject of Research: Transcranial Magnetic Stimulation and Motor Cortex Excitability

Article Title: Effects of different transcranial magnetic stimulation coil types on phosphene thresholds and their association with motor cortex excitability.

Article References:

Fidancı, H., Alaydın, H.C., Cöddü, C. et al. Effects of different transcranial magnetic stimulation coil types on phosphene thresholds and their association with motor cortex excitability. BMC Neurosci 26, 62 (2025). https://doi.org/10.1186/s12868-025-00977-1

Image Credits: AI Generated

DOI: https://doi.org/10.1186/s12868-025-00977-1

Keywords: Transcranial Magnetic Stimulation, Motor Cortex Excitability, Phosphene Thresholds, Neurotechnology, Precision Medicine

Major depressive disorder is a pervasive and debilitating mental health condition characterized by persistent low mood and a constellation of cognitive impairments that impair daily functioning and social integration. These cognitive impairments often linger even after mood symptoms improve, posing a significant challenge for clinicians. Traditionally, cognitive evaluations rely on extensive neuropsychological testing batteries, which are time-intensive and susceptible to subjective bias. The present study pioneers the use of RMT—a quantitative measure of motor cortical excitability obtained via transcranial magnetic stimulation (TMS)—as an objective, potentially scalable tool to predict cognitive function.

The investigation enrolled a sizable cohort of 158 first-episode, drug-naive patients with MDD, assessed between August 2023 and April 2024. The participants underwent the MATRICS Consensus Cognitive Battery (MCCB), a comprehensive suite designed to evaluate multiple cognitive domains relevant to psychiatric conditions, alongside RMT measurement via TMS. Additionally, hormone assays were performed to control for the modulatory effects of endocrine factors on neurocognitive function. This robust methodological framework ensured that the findings reflect intrinsic brain physiology rather than medication effects or hormonal confounds.

The analysis included 138 patients who completed all assessments, comprising 41 males and 97 females with an average age of approximately 19 years, marking a young cohort at a critical developmental period. Statistical correlations revealed that in the total sample, higher right hemisphere RMT correlated positively with enhanced attention and vigilance, as measured by the Continuous Performance Test-Identical Pairs (CPT-IP). This suggests that greater motor cortex excitability in the right hemisphere might confer an advantage in sustaining attention among individuals with depression, a domain frequently impaired in MDD.

Intriguingly, when stratified by sex, the data exposed starkly divergent patterns. In male patients, a higher left hemisphere RMT was associated with poorer verbal learning performance, gauged by the Hopkins Verbal Learning Test-Revised (HVLT-R), while the right hemisphere RMT exhibited a protective effect, correlating positively with verbal learning outcomes. Such lateralized correlations intimate that hemispheric motor cortical excitability differentially influences cognitive faculties in males, potentially mediating the severity and profile of cognitive dysfunction in depression. Female patients, however, showed no significant association between RMT and the cognitive domains assessed, underscoring a critical sex-specific dissociation.

These results bear profound implications for the pathophysiology and treatment of MDD. RMT, as a non-invasive and reproducible neurophysiological index, may serve as a biomarker reflecting the integrity of cortical excitability and its modulation of cognitive processes. The distinct lateralization and sex-dependent associations revealed here emphasize the necessity of incorporating biological sex as a fundamental variable in both research paradigms and clinical protocols. This nuanced understanding could refine therapeutic approaches, particularly those employing repetitive transcranial magnetic stimulation (rTMS), which targets motor cortex excitability to alleviate both mood and cognitive symptoms in depression.

Notably, the study’s multiple regression analyses demonstrated that the relationships between RMT and cognitive outcomes were independent of confounders such as age, education level, and hormone concentrations. This underscores the direct relevance of motor cortical excitability to cognitive performance, rather than these associations being secondary to demographic or endocrine factors. Consequently, RMT may emerge as an objective biomarker that surpasses traditional cognitive testing in predictive power and clinical utility.

Despite its promising findings, this exploratory study invites caution and calls for replication and extension. The relatively young sample and the cross-sectional design limit the generalizability and causal inferences. Longitudinal research encompassing larger, more diverse populations is essential to validate the prognostic value of RMT and to elucidate the mechanistic pathways linking motor cortical excitability and cognitive function in depression across the lifespan.

Moreover, the absence of significant correlations in female patients raises complex questions about sex-specific neurobiological mechanisms in depression. Future investigations might explore hormonal fluctuations, neuroinflammatory profiles, or genetic modulators that differentially influence cortical excitability and cognitive networks in women. Such research could unravel tailored interventions optimized for sex-based neurocircuitry differences.

Importantly, the integration of RMT assessment into clinical practice could revolutionize the management of cognitive impairments in MDD. Non-invasive brain stimulation techniques, calibrated based on individual RMT profiles, hold the promise to modulate neural plasticity and restore cognitive functions impaired by depression. This personalized neurotherapeutic approach aligns with the broader precision psychiatry movement, aiming for interventions that address not only mood symptoms but also the often-neglected cognitive dimensions of mental illness.

In summary, this pioneering study leverages the intersection of neurophysiology and cognitive psychiatry to identify RMT as a potential objective marker for cognitive capacities in drug-naive individuals with major depressive disorder. The elucidation of sex-specific patterns enhances our understanding of depression’s heterogeneous neurobiology and advocates for sex-informed clinical strategies. As rTMS and related modalities gain traction, the use of RMT could inform both prognosis and individualized treatment planning, heralding a new era in the holistic care of patients battling depression.

Xu, L., He, J., Yang, L., and colleagues have set a compelling precedent for future research exploring the neurobiological determinants of cognitive dysfunction in MDD. Their work, published in BMC Psychiatry, not only advances scientific knowledge but also opens avenues for innovative clinical applications that may alleviate the cognitive burden borne by millions affected by this debilitating disorder.

Subject of Research: Utilization of resting motor threshold (RMT) as a neurophysiological predictor of cognitive function in drug-naive patients with major depressive disorder (MDD), with a focus on sex-specific differences.

Article Title: Utilizing resting motor threshold to predict cognitive function in drug-naive patients with major depressive disorder

Article References:
Xu, L., He, J., Yang, L. et al. Utilizing resting motor threshold to predict cognitive function in drug-naive patients with major depressive disorder. BMC Psychiatry 25, 1001 (2025). https://doi.org/10.1186/s12888-025-07393-z

DOI: https://doi.org/10.1186/s12888-025-07393-z

Opioid addiction remains a devastating public health crisis worldwide, with profound psychological, social, and economic repercussions. Despite the availability of pharmacological treatments such as methadone and buprenorphine, relapse rates remain high and effective long-term recovery solutions are elusive. Central to the pathology of addiction is the dysfunction of reward processing circuits, which impairs an individual’s ability to experience pleasure and makes drug-seeking behavior compulsive rather than voluntary. While much of prior research has focused on the dopamine system and limbic structures, this study shifts focus to the aMCC, highlighting its crucial role in mediating responses to reward stimuli in opioid users.

The anterior midcingulate cortex straddles the intersection of cognitive control, pain perception, and motivational aspects of behavior. Functionally, it acts as an integrative hub, processing signals related to reward expectation and error monitoring. In opioid-dependent individuals, this study documents that the aMCC response to rewarding stimuli is significantly attenuated—a phenomenon that explains, in part, the diminished sensitivity to natural reinforcers observed clinically. Utilizing functional magnetic resonance imaging (fMRI) during reward-based tasks, researchers recorded neural activations, revealing that, compared to healthy controls, opioid users consistently exhibited lower aMCC activation in response to monetary incentives.

To interrogate whether this neural deficit is reversible, the researchers applied repetitive TMS over the dorsolateral prefrontal cortex (DLPFC), a brain region interconnected with the aMCC and implicated in executive control and regulation over limbic circuits. TMS utilizes magnetic pulses to induce electric fields in targeted cortical areas, transiently enhancing or suppressing neuronal excitability. In this cohort of opioid users, daily sessions of prefrontal TMS were delivered over a two-week period. Post-treatment neuroimaging revealed a remarkable restoration of aMCC activity during reward tasks, bringing the neural signature closer to that observed in non-addicted individuals.

What cements the significance of this study is the demonstration that the normalization of brain activity was coupled with improved behavioral indices related to reward sensitivity and reduced drug craving. Participants reported decreased urges to use opioids and showed improved performance in decision-making paradigms, which rely heavily on intact reward circuits. These findings suggest that TMS-induced modulation of frontocingulate networks can recalibrate reward processing deficits, offering a potential adjunct or alternative to pharmacotherapy in OUD.

The mechanistic insights derived from this work extend beyond mere correlation, proposing a causal pathway wherein disrupted communication between the prefrontal cortex and aMCC underlies impaired reward responsiveness in opioid addiction. By dampening the cortical hypoactivity through external magnetic stimulation, it is possible to reinstate normal functional dynamics, essentially ‘resetting’ the dysfunctional circuits. This has powerful implications for how we conceptualize addiction at a systems neuroscience level—as a disorder amenable to circuit-level intervention, rather than purely chemical imbalance.

This novel approach aligns with a growing movement in psychiatry and neurology to leverage neuromodulation technologies such as TMS, transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS) for the treatment of neuropsychiatric disorders. Previously established indications for TMS in depression and obsessive-compulsive disorder hint at its versatility, but its application in addiction medicine is still emergent. This study importantly validates the feasibility and efficacy of targeting frontocingulate pathways in a well-defined substance use disorder population.

The clinical translation of these findings could be transformative. Unlike pharmacological agents that require daily administration and carry risks of side effects or dependence, TMS offers a non-pharmacological, non-invasive intervention. Furthermore, identifying biomarkers such as aMCC activation patterns can refine patient selection and track treatment response, ushering in an era of personalized addiction medicine. These advances could ultimately reduce relapse rates and improve quality of life for millions suffering from opioid addiction.

However, the study authors caution that larger randomized controlled trials are essential to corroborate these preliminary outcomes and optimize stimulation parameters, including frequency, intensity, and duration of TMS sessions. The heterogeneity inherent to addiction—spanning differences in drug type, duration of use, comorbid psychiatric conditions, and individual neurobiology—necessitates flexible and adaptive therapeutic frameworks. Additionally, combining TMS with behavioral therapies or pharmacological agents could potentiate treatment efficacy, an avenue ripe for exploration.

On a neuroscientific front, this research enriches our understanding of the complex interplay between cognitive control networks and reward systems in addiction pathology. The aMCC, often underappreciated compared to classic reward centers like the ventral striatum or orbitofrontal cortex, emerges as a critical node whose dysfunction embodies the diminished reward learning and motivational deficits driving compulsive drug use. It also prompts further inquiry into whether similar neural mechanisms exist in other forms of addiction, such as stimulants or alcohol, thus broadening therapeutic horizons.

Technically, the study employed rigorous multimodal imaging paradigms combining fMRI with electrophysiological monitoring during TMS sessions, ensuring precise mapping of neural responses and stimulation effects. Advanced analytic approaches dissected signal changes at a fine temporal and spatial resolution, allowing for robust interpretation of frontocingulate circuit dynamics. This methodological sophistication strengthens confidence in the reported neurobiological mechanisms and their clinical relevance.

Moreover, the safety profile of prefrontal TMS was favorable, with minimal adverse events reported, underscoring its suitability for potential widespread clinical use. The non-invasive nature of TMS also sidesteps many obstacles associated with invasive neuromodulation strategies, such as DBS, including surgical risks and long-term device management. Accessibility and patient tolerance further support its integration into standard addiction treatment regimens.

As the opioid epidemic continues to ravage communities globally, fueled by potent synthetic opioids and limited treatment options, innovative interventions are desperately needed. This study provides hope that harnessing the plasticity of brain networks through technologies like TMS can heal the disrupted reward systems at the heart of addiction. It champions a conceptual shift from symptom management toward functional brain restoration—a paradigm that promises enduring recovery and resilience.

In conclusion, the normalization of anterior midcingulate cortex responses to reward in opioid users by prefrontal transcranial magnetic stimulation represents a seminal step forward in addiction neuroscience and therapy. By bridging molecular, circuit, and behavioral domains, this research pioneers a translational approach that can reshape therapeutic landscapes. Continued investigation into the optimization, integration, and long-term outcomes of TMS for OUD has the potential to revolutionize how we confront and conquer one of modern medicine’s most intractable challenges.

Subject of Research: Neural mechanisms underlying opioid addiction and modulation of reward processing via prefrontal transcranial magnetic stimulation

Article Title: Blunted anterior midcingulate response to reward in opioid users is normalized by prefrontal transcranial magnetic stimulation

Article References:
Biernacki, K., Goldstein, R.Z., Güth, M.R. et al. Blunted anterior midcingulate response to reward in opioid users is normalized by prefrontal transcranial magnetic stimulation. Transl Psychiatry 15, 340 (2025). https://doi.org/10.1038/s41398-025-03569-z

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41398-025-03569-z