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Sun Y.,National University of Singapore | Thakor N.,Singapore Institute for Neurotechnology
IEEE Transactions on Biomedical Engineering | Year: 2016

Photoplethysmography (PPG) is a noninvasive optical technique for detecting microvascular blood volume changes in tissues. Its ease of use, low cost and convenience make it an attractive area of research in the biomedical and clinical communities. Nevertheless, its single spot monitoring and the need to apply a PPG sensor directly to the skin limit its practicality in situations such as perfusion mapping and healing assessments or when free movement is required. The introduction of fast digital cameras into clinical imaging monitoring and diagnosis systems, the desire to reduce the physical restrictions, and the possible new insights that might come from perfusion imaging and mapping inspired the evolution of the conventional PPG technology to imaging PPG (IPPG). IPPG is a noncontact method that can detect heart-generated pulse waves by means of peripheral blood perfusion measurements. Since its inception, IPPG has attracted significant public interest and provided opportunities to improve personal healthcare. This study presents an overview of the wide range of IPPG systems currently being introduced along with examples of their application in various physiological assessments. We believe that the widespread acceptance of IPPG is happening, and it will dramatically accelerate the promotion of this healthcare model in the near future. © 2015 IEEE. Source


Maksimovic M.,University of Helsinki | Aitta-Aho T.,University of Helsinki | Korpi E.R.,University of Helsinki | Korpi E.R.,National University of Singapore | Korpi E.R.,Singapore Institute for Neurotechnology
European Journal of Pharmacology | Year: 2014

Malfunction of glutamate transmission is implicated in several neuropsychiatric disorders. Gria1-/- mouse line with knocked-out GluA1 subunits of ionotropic AMPA glutamate receptor displays several behavioural features of schizoaffective disorder. Typically, these mice show hyperactivity provoked by environmental novelty, which is attenuated after 4-week treatment with the standard mood-stabilisers lithium and valproate and the mood-stabilising anticonvulsants topiramate and lamotrigine (Maksimovic, M., Vekovischeva, O.Y., Aitta-Aho, T., Korpi, E.R., 2014. Chronic treatment with mood-stabilizers attenuates abnormal hyperlocomotion of GluA1-subunit deficient mice. PloS One. 9, e100188). Here, we complement our study by treating these mice chronically with perampanel, a novel non-competitive antagonist of AMPA receptors, for 4 weeks at the dose of 60 mg/kg diet, and found reduced locomotor hyperactivity in the Gria1-/- animals, while not affecting the wild-type littermates. To study the cellular mechanism by which chronic treatments with glutamate-modulating mood-stabilizing drugs alleviate this hyperactivity, we used the immediate early gene c-Fos protein expression as a marker of neuronal activity in the brain. Chronic lithium, valproate and topiramate blunted the c-Fos expression especially in the dorsal hippocampus of the Gria1-/- mice, with all of them reducing the number of c-Fos-positive cells in the CA3 region and valproate and topiramate also in the dentate gyrus (DG). Lamotrigine and perampanel treatments had the same effect in the all CA1, CA3 and DG subfields of the dorsal hippocampus of Gria1-/- mice. The results suggest that abnormal (hippocampal) glutamatergic transmission underlies the hyperactive phenotype of the Gria1-/- mice in a novel environment, and based on the efficacies of the present chronic drug treatments, this mouse model may serve as a predictive tool for studying novel mood-stabilisers. © 2014 Elsevier B.V. Source


Hellsten K.S.,University of Helsinki | Linden A.-M.,University of Helsinki | Korpi E.R.,University of Helsinki | Korpi E.R.,National University of Singapore | Korpi E.R.,Singapore Institute for Neurotechnology
Neuroscience | Year: 2015

A GABA-site agonist gaboxadol (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) at 3mg/kg induces strong anxiolytic response in a transgenic Thy1α6 mouse line ectopically expressing the GABAA receptor α6 subunit gene under the Thy-1.2 promoter. Now, we compared brain activation patterns between Thy1α6 and wild-type mice to identify brain structures potentially mediating this anxiolytic response. Acutely efficient anxiolytics such as benzodiazepines typically depress most brain regions while activating specifically neurons within the central extended amygdala. Gaboxadol treatment (3mg/kg, i.p., 2h) induced a significant increase in c-Fos expression selectively in many Thy1α6 brain regions including the limbic cortex, anterior olfactory nucleus, septal area and central and basolateral nuclei of amygdala. It failed to activate the lateral part of mediodorsal thalamic nucleus (MDL) in the Thy1α6 mice that was activated in the wild-type mice. Detailed mapping of the α6 subunit mRNA by in situ hybridization revealed expression in the middle layers of the isocortex, olfactory areas, hippocampal formation and basolateral nucleus of amygdala (BLA) in the Thy1α6 forebrain. The ligand autoradiographies (t-butylbicyclophosphoro[35S]thionate ([35S]TBPS) and [3H]Ro 15-4513) revealed high levels of pharmacologically active extrasynaptic α6β and α6βγ2 GABAA receptors in these same areas. However, c-Fos induction by gaboxadol treatment in Thy1α6 brain was not restricted to areas highly expressing the α6-containing GABAA receptors suggesting that indirect pathways lead to the paradoxically widespread activation. Interestingly, the activation pattern by gaboxadol at the dose that is anxiolytic in Thy1α6 mice resembled closely that observed after various fear- and stress-provoking challenges. However, our results are consistent with a recent observation that optogenetic activation of specific neuronal pathways in the extended amygdala mediates anxiolytic responses. Our results suggest that the widespread neuronal inhibition as typically associated with benzodiazepines is not the exclusive mechanism of anxiolysis. © 2015 IBRO. Source


Han D.,Nanyang Technological University | Zheng Y.,Institute of Microelectronics, Singapore | Rajkumar R.,Nanyang Technological University | Dawe G.S.,Nanyang Technological University | And 4 more authors.
IEEE Transactions on Biomedical Circuits and Systems | Year: 2013

Neural prosthetics and personal healthcare have increasing need of high channel density low noise low power neural sensor interfaces. The input referred noise and quantization resolution are two essential factors which prevent conventional neural sensor interfaces from simultaneously achieving a good noise efficiency factor and low power consumption. In this paper, a neural recording architecture with dynamic range folding and current reuse techniques is proposed and dedicated to solving the noise and dynamic range trade-off under low voltage low power operation. Measured results from the silicon prototype show that the proposed design achieves 3.2 μVrms input referred noise and 8.27 effective number of bits at only 0.45 V supply and 0.94 μ W/channel power consumption. © 2014 IEEE. Source


Yap H.K.,National University of Singapore | Ang B.W.K.,National University of Singapore | Lim J.H.,National University of Singapore | Goh J.C.H.,National University of Singapore | And 2 more authors.
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2016

This paper presents a soft robotic glove designed to assist individuals with functional grasp pathologies in performing activities of daily living. The glove utilizes soft fabric-regulated pneumatic actuators that are low-profile and require lower pressure than previously developed actuators. They are able to support fingers and thumb motions during hand closure. Upon pressurization, the actuators are able to generate sufficient force to assist in hand closing and grasping during different manipulation tasks. In this work, experiments were conducted to evaluate the performances of the actuators as well as the glove in terms of its kinetic and kinematic assistance on a healthy participant. Additionally, surface electromyography and radio-frequency identification techniques were adopted to detect user intent to activate or deactivate the glove. Lastly, we present preliminary results of a healthy participant performing different manipulation tasks with the soft robotic glove controlled by surface electromyography and radio-frequency identification techniques. © 2016 IEEE. Source

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