Motor evoked potentials (MEPs) induced by transcranial magnetic stimulation (TMS) are commonly characterized only by their onset (latency) and size (amplitude) whereas other potentially important information in the MEPs is discarded. Hence, our aim was to examine the morphological information of MEPs using principal component regression (PCR) providing additional perception of MEPs. MEPs were recorded from the first dorsal interosseous muscle following navigated TMS focused at the primary motor cortex. The PCR holding of at least 96% of total variance of the MEP dataset was performed to parameterize MEPs into principal components (PCs), which were used with non-linear least square estimation to reconstruct original MEPs. The comparison between the original and reconstructed MEPs showed that PCs, which accounted for 96% of total variance, were able to characterize the MEP morphology, i.e., the PCR summarizes the repeated information in the MEP dataset into the PC set. In addition, PCR benefited the automated quantification of MEP features as it removed the random noise caused by the environmental interference and the inconsistency of neuronal pathways. Furthermore, we could determine the minimum number of trials required to reliably represent the whole dataset by estimating the partial information of those trials accounted for. Our results showed that this partial information exponentially increased with respect to the number of trials, and saturated within 20 MEPs holding approximately 90% of total variance of the dataset.

To derive the maturation of neurophysiological processes from childhood to adulthood reflected by the change of motor-evoked potential (MEP) features. 38 participants were recruited from four groups (age mean in years [SD in months], number (males)): children (7.3 [4.2], 7(4)), preadolescents (10.3 [6.9], 10(5)), adolescents (15.3 [9.8], 11(5)), and adults (26.9 [46.2], 10(5)). The navigated transcranial magnetic stimulation was performed on both hemispheres at seven stimulation intensity (SI) levels from sub- to supra-threshold and targeted to the representative cortical area of abductor pollicis brevis muscle. MEPs were measured from three hand- and two forearm-muscles. The input–output (I/O) curves of MEP features across age groups were constructed using linear mixed-effect models. Age and SI significantly affected MEP features, whereas the stimulated side had a minor impact. MEP size and duration increased from childhood to adulthood. MEP onset- and peak-latency dropped in adolescence, particularly in hand muscles. Children had the smallest MEPs with the highest polyphasia, whereas I/O curves were similar among preadolescents, adolescents, and adults. This study illustrates some of the changing patterns of MEP features across the ages, suggesting developing patterns of neurophysiological processes activated by TMS, and to motivate studies with larger sample size.

This paper represents the clinical decision support system for video head impulse test (vHIT) based on fuzzy inference system. It examines the eye and head movement recorded by the eye movement tracking device, calculates the vestibulo-ocular reflex (VOR) gain, and applies fuzzy inference system to output the normality and artifact index of the test result. The position VOR gain and the proportion of covert and overt catch-up saccades (CUS) within the dataset are used as the input of the inference system. In addition, this system yields one more factor, the artifact index, which represents the current interference in the dataset. Data of fifteen vestibular neuritis patients and two of normal subjects were evaluated. The artifact index appears to be very high in the lesion side of vestibular neuritis (VN) patients, indicating highly theoretical contradictions, which are low gain but without CUS, or normal gain with the appearance of CUS. Both intact side and normal subject show high normality and low artifact index, even though the intact side has slightly lower normality and higher artifact index. In conclusion, this is a robust system, which is the first one that takes gain and CUS into account, to output not only the normality of the vHIT dataset, but also the artifacts.

Vestibulo-ocular reflex (VOR) is an important biological reflex that controls eye movement to ensure clear vision while the head is in motion. Nowadays, VOR measurement is commonly done with a video head impulse test based on a velocity gain algorithm or a position gain algorithm, in which velocity gain is a VOR calculation on head and eye velocity, whereas position gain is calculated from head and eye position. The aim of this work is first to compare the two algorithms' performance and to detect covert catch-up saccade, then to propose a stand-alone recommendation application for the patient's diagnosis. In the first experiment, for ipsilesional and contralesional sides, the calculated position gain (0.94±0.17) is higher than velocity gain (0.84±0.19). Moreover, gain asymmetry of both lesion and intact sides using velocity gain is mostly higher than that from using position gain (four out of five subjects). Consequently, for subjects who have unilateral vestibular neuritis diagnosed from clinical symptoms and a vestibular function test, vestibular weakness is depicted by velocity gain much better than by position gain. Covert catch-up saccade and position gain then are used as inputs for recommendation applications.