Advancements in Transcranial Magnetic Stimulation Research and the Path to Precision

Transcranial magnetic stimulation (TMS) has become increasingly popular in clinical practice in recent years, and there have been significant advances in the principles and stimulation modes of TMS. With the development of multi-mode and precise stimulation technology, it is crucial to have a comprehensive understanding of TMS. The neuroregulatory effects of TMS can vary depending on the specific mode of stimulation, highlighting the importance of exploring these effects through multimodal application. Additionally, the use of precise TMS therapy can help enhance our understanding of the neural mechanisms underlying these effects, providing us with a more comprehensive perspective. This article aims to review the mechanism of action, stimulation mode, multimodal application, and precision of TMS.

The influences of stimulation mode and stimulus frequency on acoustic reflex latency (ARL) among young adults

INTRODUCTION

Acoustic reflex (AR) is a valuable clinical test for hearing diagnosis. Parameters of AR such as its amplitude and threshold have been commonly reported in research. Acoustic reflex latency (ARL) has not been widely studied and more research is warranted to determine its basic properties and clinical usefulness. The present study aimed to determine the influences of stimulation mode and stimulus frequency on ARL.

METHODS

In this study, 52 healthy young adults were enrolled (mean age = 23.2 ± 0.8 years, 61.8% were males). They underwent the standard AR testing and ARL values were computed. Both ipsilateral and contralateral recordings were made at 500, 1000, 2000 and 4000 Hz frequencies.

RESULTS

The ARL values obtained are consistent with the findings from the previous studies. Two-way analysis of variance (ANOVA) revealed that the ARL values were not statistically influenced by either stimulation mode (p = 0.061) or stimulus frequency (p = 0.598).

CONCLUSION

Among young adults, ARL does not appear to be influenced by stimulation mode and stimulus frequency. Further large scale research is warranted to support the present study's findings. The preliminary normative data for ARL obtained in this study can serve as the reference for future research involving this particular population.

Temporal Modulation Detection Depends on Sharpness of Spatial Tuning

Prior research has shown that in electrical hearing, cochlear implant (CI) users' speech recognition performance is related in part to their ability to detect temporal modulation (i.e., modulation sensitivity). Previous studies have also shown better speech recognition when selectively stimulating sites with good modulation sensitivity rather than all stimulation sites. Site selection based on channel interaction measures, such as those using imaging or psychophysical estimates of spread of neural excitation, has also been shown to improve speech recognition. This led to the question of whether temporal modulation sensitivity and spatial selectivity of neural excitation are two related variables. In the present study, CI users' modulation sensitivity was compared for sites with relatively broad or narrow neural excitation patterns. This was achieved by measuring temporal modulation detection thresholds (MDTs) at stimulation sites that were significantly different in their sharpness of the psychophysical spatial tuning curves (PTCs) and measuring MDTs at the same sites in monopolar (MP) and bipolar (BP) stimulation modes. Nine postlingually deafened subjects implanted with Cochlear Nucleus® device took part in the study. Results showed a significant correlation between the sharpness of PTCs and MDTs, indicating that modulation detection benefits from a more spatially restricted neural activation pattern. There was a significant interaction between stimulation site and mode. That is, using BP stimulation only improved MDTs at stimulation sites with broad PTCs but had no effect or sometimes a detrimental effect on MDTs at stimulation sites with sharp PTCs. This interaction could suggest that a criterion number of nerve fibers is needed to achieve optimal temporal resolution, and, to achieve optimized speech recognition outcomes, individualized selection of site-specific current focusing strategies may be necessary. These results also suggest that the removal of stimulation sites measured with poor MDTs might improve both temporal and spectral resolution.