Neuromodulation serves as a cornerstone for brain sciences and clinical applications. Recent research indicates that midinfrared stimulation (MIRS) causes non-thermal modulation of brain functions. Current understanding of its mechanism hampers the routine application of MIRS. In this study, we examined how MIRS with 34.88THz modulated the sensorimotor transformation from neuronal signals to behavior performances in awaking-behaving pigeons. We applied MIRS and electrical stimulation to the pretectal nucleus lentiformis mesencephali (nLM), an essential retinorecipient structure in the pretectum, and compared their effects on the visual-guided eye movement optokinetic nystagmus. We found that MIRS altered eye movements by modulating a specific gain depending on the strength of visual inputs, in a manner different than the effect of ES. Simultaneous extracellular recordings and stimulation showed that MIRS could either excite and inhibit the neuronal activity in the same pretectal neuron depending on its ongoing sensory responsiveness levels in awake-behaving animals. These modulations increased with the size of MIRS output powers. Computational simulations suggest a potential mechanism underlying these effects in which MIRS preferentially enhances the resonance of a carbonyl group of the potassium channel, which critical to the action potential generation, thereby altering neuronal responses to sensory inputs and as a result guiding behavior. Our findings suggest that MIRS could be a promising approach for modulating neuronal functions for brain research and treating neurological diseases.
In this paper, a novel strategy for diagnosis of bTBI is proposed by measuring terahertz (THz) spectroscopy of serum in a rat model. A compressed air-driven shock wave generator was used to establish bTBI model of rats. It was validated by a neurological deficit assessment method. The spectral differences of serum for different degrees of bTBI rats have been demonstrated by THz time-domain spectroscopy (THz-TDS). Moreover, based on the THz spectra of serum, the principal component analysis (PCA) and support vector machine (SVM) were performed to automatically identify the degrees of bTBI. The results indicate that THz spectroscopy could provide a sensitive, rapid and label-free diagnosis method for bTBI.
We proposed a novel interference elimination method for CW-THz reflection imaging. Based on the study of interference mechanism in the imaging window, inverse processing was proposed to realize the interference elimination. Theoretical calculation showed that the interference phenomenon was closed related to the characteristics of imaging window. The refractive index and thickness of the window were the two main factors for the interference. Moreover, polarization was also taken into consideration for the CW-THz reflection imaging because the reflectivities of the s and p polarized waves were different from each other. This method was applied in different imaging systems for the demonstration of its feasibility. The high resistivity float-zone silicon (HRFZ-Si) plate was employed as the imaging window in the normal incidence system with a terahertz quantum cascade laser (THz-QCL) operating at 4.3THz. The oblique system employed quartz plate as the imaging window with an optical pumped THz laser operating at 2.52THz. Pork and liquid samples of water and edible oils were chosen as the imaging samples to demonstrate the interference elimination method.
Terahertz time domain spectroscopy has been widely used in tumor detection, chemical analysis and nondestructive testing. However, the measurement errors of terahertz time domain spectrum frequently occur because of vibration of experiment instrument platform or temperature and humidity changes. Lifting wavelet transform based on different wavelet basis functions was applied to the denoising of terahertz time domain spectrum of PTFE. The denoising results were compared with denoising results of wavelet soft threshold method. The wavelet soft threshold method got a highest signal to noise ratio (SNR) of 58.75 dB and a least root mean square error (RMSE) of 3.56*10^ (-5), while lifting wavelet transform method achieved a highest SNR of 60.69 dB and a least RMSE of 2.85*10^ (-5). These results imply that lifting wavelet transform performs better in terahertz spectrum denoising than wavelet soft threshold.
Biological tissue sections are always kept in a system purged with dry nitrogen for the measurement of terahertz spectrum. However, the injected nitrogen will cause dehydration of tissue sections, which will affect the accuracy of spectrum measurement. In this paper, terahertz time-domain spectrometer is used to measure the terahertz spectra of rat brain tissue sections during dehydration. The changes of terahertz properties, including terahertz transmittance, refractive index and extinction coefficient during dehydration are also analyzed. The amplitudes of terahertz time-domain spectra increase gradually during the dehydration process. Besides, the terahertz properties show obvious changes during the dehydration process. All the results indicate that the injected dry nitrogen has a significant effect on the terahertz spectra and properties of tissue sections. This study contributes to further research and application of terahertz technology in biomedical field.
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