Lai, C. S. W. | Search bioRxiv

bioRxiv2023

The Effect of Transcranial Direct Current and Magnetic Stimulation on Fear Extinction and Return of Fear: A meta-analysis and Systematic Review

Anxiety and fear-related disorders are among the most prevalent mental illnesses. Non-invasive brain stimulation methods such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) have been employed to modulate anxiety and fear-related symptoms, but their therapeutic effects remain inconclusive. Pavlovian conditioning and extinction are experimental analogues of exposure therapy that investigate the neural mechanisms of fear extinction and return of fear. We conducted a meta-analysis and qualitative review on the effects of tDCS and TMS on fear extinction and return of fear in non-primate animals and humans. Results show that both anodal and cathodal tDCS over the prefrontal cortex inhibit short-term contextual and cued fear retrieval in animal models. In human studies, anodal tDCS over the medial/ventromedial prefrontal cortex enhances fear extinction, whereas TMS over the dorsolateral/ventromedial prefrontal cortex inhibits return of fear. Our findings suggest the optimal non-invasive brain stimulation protocols for threat extinction in humans.

neuroscience↗

bioRxiv2022

Tomographic-encoded multiphoton (TEMP) microscopy

Axial scanning in multiphoton microscopy (MPM) is typically realized by mechanically shifting either the objective or the sample. However, the scan speed is usually hindered by the mechanical inertia of the bulky mass. Although the extended depth of field provided by the non-diffracting beam allows fast volumetric imaging, it abandons the axial resolution. Here, we demonstrate a novel and powerful tomographic technique using the Bessel droplet in MPM, termed Tomographic-Encoded MultiPhoton (TEMP) microscopy. We show that benefiting from the high-order nonlinear excitation in MPM, the side-lobes cancellation and smaller beam focus of the Bessel droplet realize better image quality. The TEMP microscopy allows fast axial scanning, less risks of photodamage and photobleaching, and high-resolution and high-contrast imaging. Furthermore, fewer raw images are required for the 3D image reconstruction. To demonstrate its usability and advantages for scattering tissues and biomedical applications, we showcase the TEMP microscopy with highly scattering fluorescence microspheres and mouse brain slice. More details can be visualized by the Bessel droplet compared with the conventional Gaussian and Bessel beam. More importantly, the TEMP technique is an easy-plug-in method for the current microscopy system. The TEMP microscopy is promising for fast volumetric multiphoton imaging, especially for highly scattering tissues.

bioengineering↗