IntroductionIn the field of upper limb brain computer interfaces (BCIs), the research focusing on bilateral decoding mostly based on the neural signals from two cerebral hemispheres. In addition, most studies used spikes for decoding. Here we examined the representation and decoding of different laterality and regions arm motor imagery in unilateral motor cortex based on local field potentials (LFPs).MethodsThe LFP signals were recorded from a 96-channel Utah microelectrode array implanted in the left primary motor cortex of a paralyzed participant. There were 7 kinds of tasks: rest, left, right and bilateral elbow and wrist flexion. We performed time-frequency analysis on the LFP signals and analyzed the representation and decoding of different tasks using the power and energy of different frequency bands.ResultsThe frequency range of <8 Hz and >38 Hz showed power enhancement, whereas 8–38 Hz showed power suppression in spectrograms while performing motor imagery. There were significant differences in average energy between tasks. What’s more, the movement region and laterality were represented in two dimensions by demixed principal component analysis. The 135–300 Hz band signal had the highest decoding accuracy among all frequency bands and the contralateral and bilateral signals had more similar single-channel power activation patterns and larger signal correlation than contralateral and ipsilateral signals, bilateral and ipsilateral signals.DiscussionThe results showed that unilateral LFP signals had different representations for bilateral motor imagery on the average energy of the full array and single-channel power levels, and different tasks could be decoded. These proved the feasibility of multilateral BCI based on the unilateral LFP signal to broaden the application of BCI technology.Clinical trial registrationhttps://www.chictr.org.cn/showproj.aspx?proj=130829, identifier ChiCTR2100050705.
IntroductionHow the human brain coordinates bimanual movements is not well-established.MethodsHere, we recorded neural signals from a paralyzed individual’s left motor cortex during both unimanual and bimanual motor imagery tasks and quantified the representational interaction between arms by analyzing the tuning parameters of each neuron.ResultsWe found a similar proportion of neurons preferring each arm during unimanual movements, however, when switching to bimanual movements, the proportion of contralateral preference increased to 71.8%, indicating contralateral lateralization. We also observed a decorrelation process for each arm’s representation across the unimanual and bimanual tasks. We further confined that these changes in bilateral relationships are mainly caused by the alteration of tuning parameters, such as the increased bilateral preferred direction (PD) shifts and the significant suppression in bilateral modulation depths (MDs), especially the ipsilateral side.DiscussionThese results contribute to the knowledge of bimanual coordination and thus the design of cutting-edge bimanual brain-computer interfaces.
The Ganjiang River, one of eight major tributaries of the Yangtze River, located in the western hinterland of the Cathaysia Block, SE China, has a length of 823 km and a drainage area of 82 809 km2, whose detrital zircons provide a valuable means to trace sediment provenances of the river and explore the crustal growth and evolution of the Cathaysia Block. In the current study, 389 concordia zircon U–Pb age spots and rare earth element (REE) contents, in combination with 201 Lu–Hf isotope analyses, have been determined. Oscillatory zoning, high Th/U ratios and REE distribution patterns indicate that most detrital zircon grains are of magmatic origin. The age can be further divided into seven groups: 130–185 Ma with a peak at 153 Ma (7 %); 217–379 Ma with a peak at 224 Ma (16 %); 390–494 Ma with a peak at 424 Ma (37 %); 500–698 Ma with a peak at 624 Ma (5 %); 716–897 Ma with a peak at 812 Ma (10 %); 902–1191 Ma with a peak at 976 Ma (13 %); and 2232–2614 Ma with a peak at 2471 Ma (5 %). The sources of almost all the zircon age groups can be found from the exposed rocks. In particular, Yanshanian, Hercynian to Indosinian, Pan-African, Grenvillian and Palaeoproterozoic–Archaean zircons can be mainly sourced from the northern Guangdong – southern Jiangxi – western Fujian region, while Caledonian zircons come from southern and central Jiangxi, and Jinningian zircons are from central and northern Jiangxi. Most determined zircon grains exhibit negative εHf(t) values and TDM2 ages of 797 to 4016 Ma with a wide peak at 1500–2100 Ma and a keen peak at 1824 Ma, suggesting that most zircons are sourced from the reworked ancient crustal materials or crust–mantle mixing. The zircon Hf model age cumulative probability diagram shows that rapid crustal growth took place at the Palaeo- to Mesoproterozoic and that about 90 % of the crust of the Cathaysia Block was formed before 1.5 Ga.
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