Ujwal Chaudhary

Effect of Porosity on Photocatalytic Activity of Plasma-Sprayed TiO2 Coating

The effect of porosity on photocatalytic activity of plasma-sprayed TiO2 coating on steel substrate is studied by varying processing parameters viz. plasma power and powder feed rate. The relationship between porosity content and methylene blue (MB) dye decomposition rate was established to correlate coating microstructure and its photocatalytic activity. The coating with the highest porosity content exhibited best photocatalytic efficiency. The same processing parameters were used to deposit TiO2 coating on FTO glass. The photocatalytic activity of TiO2 coating on FTO was 2.5 times better than TiO2 coating on the steel substrate. TiO2 coating on FTO glass contains bimodal porosity distribution (micropores and submicron pores) which accelerated MB decomposition by accelerated diffusion of ionic species.

Motor response investigation in individuals with cerebral palsy using near infrared spectroscopy: pilot study

Cerebral palsy (CP) describes a group of motor impairment syndromes secondary to genetic that may be due to acquired disorders of the developing brain. In this study, near infrared spectroscopy (NIRS) is used to investigate the prefrontal cortical activation and lateralization in response to the planning and execution of motor skills in controls and individuals with CP. The prefrontal cortex, which plays a dominant role in the planning and execution of motor skill stimulus, is noninvasively imaged using a continuous wave-based NIRS system. During the study, 7 controls (4 right-handed and 3 left-handed) and 2 individuals with CP (1 right-handed and 1 left-handed) over 18 years of age performed 30 s of a ball throwing task followed by 30 s rest in a 5-block paradigm. The optical signal acquired from the NIRS system was processed to elucidate the activation and lateralization in the prefrontal region of controls and individuals with CP. The preliminary result indicated a difference in activation between the task and rest conditions in all the participant types. Bilateral dominance was observed in the prefrontal cortex of controls in response to planning and execution of motor skill tasks, while an ipsilateral dominance was observed in individuals with CP. In conjunction, similar contralateral dominance was observed during rest periods, both in controls and individuals with CP.

Communication in locked-in state after brainstem stroke: a brain-computer-interface approach

In a recent study by Sellers et al. (1) a patient in locked-in state after brainstem stroke was able to successfully communicate via electroencephalography (EEG) based brain computer interface (BCI) employing a P300 speller paradigm.

Joint attention studies in normal and autistic children using NIRS

Autism is a socio-communication brain development disorder. It is marked by degeneration in the ability to respond to joint attention skill task, from as early as 12 to 18 months of age. This trait is used to distinguish autistic from nonautistic. In this study Near infrared spectroscopy (NIRS) is being applied for the first time to study the difference in activation and connectivity in the frontal cortex of typically developing (TD) and autistic children between 4-8 years of age in response to joint attention task. The optical measurements are acquired in real time from frontal cortex using Imagent (ISS Inc.) - a frequency domain based NIRS system in response to video clips which engenders a feeling of joint attention experience in the subjects. A block design consisting of 5 blocks of following sequence 30 sec joint attention clip (J), 30 sec non-joint attention clip (NJ) and 30 sec rest condition is used. Preliminary results from TD child shows difference in brain activation (in terms of oxy-hemoglobin, HbO) during joint attention interaction compared to the nonjoint interaction and rest. Similar activation study did not reveal significant differences in HbO across the stimuli in, unlike in an autistic child. Extensive studies are carried out to validate the initial observations from both brain activation as well as connectivity analysis. The result has significant implication for research in neural pathways associated with autism that can be mapped using NIRS.

Corrigendum: Brain-computer interfaces for communication and rehabilitation

Nature Reviews Neurology 12, 513–525 (2016) In the initial version of this article, details of the BrainGate2 study were omitted from Table 1. This error has been corrected in the HTML and PDF versions of the article.

A 20-Questions-Based Binary Spelling Interface for Communication Systems

Brain computer interfaces (BCIs) enables people with motor impairments to communicate using their brain signals by selecting letters and words from a screen. However, these spellers do not work for people in a complete locked-in state (CLIS). For these patients, a near infrared spectroscopy-based BCI has been developed, allowing them to reply to “yes”/”no” questions with a classification accuracy of 70%. Because of the non-optimal accuracy, a usual character-based speller for selecting letters or words cannot be used. In this paper, a novel spelling interface based on the popular 20-questions-game has been presented, which will allow patients to communicate using only “yes”/”no” answers, even in the presence of poor classification accuracy. The communication system is based on an artificial neural network (ANN) that estimates a statement thought by the patient asking less than 20 questions. The ANN has been tested in a web-based version with healthy participants and in offline simulations. Both results indicate that the proposed system can estimate a patient’s imagined sentence with an accuracy that varies from 40%, in the case of a “yes”/”no” classification accuracy of 70%, and up to 100% in the best case. These results show that the proposed spelling interface could allow patients in CLIS to express their own thoughts, instead of only answer to “yes”/”no” questions.

Lernen von Hirnkontrolle – Klinische Anwendung von Brain-Computer Interfaces@@@Learning of brain control: Clinical application of brain-computer interfaces

Brain-Computer Interfaces (Gehirn-Computer -Schnittstellen, BCI) nutzen neuroelektrische und metabolische Hirnaktivität, um periphere Geräte und Computer ohne Vermittlung des motorischen Systems zu bedienen. Um die Gehirn-Computer-Schnittstelle zu aktivieren, müssen die Personen ein gewisses Ausmaß an Hirnkontrolle erlernen. Es zeigte sich, dass die Selbstkontrolle der Hirnaktivität den Prinzipien des Fertigkeiten-Lernens und des instrumentellen Konditionierens folgt. Diese Übersicht konzentriert sich auf die klinische Anwendung von Gehirn-Computer-Schnittstellen bei gelähmten Patienten mit Locked-in Syndrom und/oder vollständigem Locked-in Syndrom (CLIS). Es wurde gezeigt, dass EEG-basierte Gehirn-Computer-Schnittstellen die Auswahl von Buchstaben und Wörtern in einem Computermenü mithilfe verschiedener EEG-Signale ermöglichen. Bei Patienten mit vollständigem Locked-in Syndrom ohne jede Muskelkontrolle, insbesondere der Augenbewegungen, waren EEG-basierte Gehirn-Computer-Schnittstellen jedoch nicht erfolgreich. Sogar nach der Implantatation von Elektroden in das Gehirn waren CLIS-Patienten nicht in der Lage, zu kommunizieren. Wir entwickelten ein theoretisches Modell, das dieses grundlegende Defizit des instrumentellen Lernens der Hirnkontrolle und der willentlichen Kommunikation erklärt: Patienten mit vollständiger Lähmung löschen zielgerichtetes reaktionsorientiertes Denken und Absichten. Daher wurde ein reflexives klassisches Konditionierungsverfahren entwickelt und mithilfe der Messung der metabolischen Hirnsignale mit Nah-Infrarot-Spektroskopie (NIRS) waren CLIS-Patienten in der Lage, einfache Fragen mit einer „ja“- oder „nein“-Hirnantwort zu beantworten. Die bisher erhobenen Daten zeigen, dass erstmals CLIS-Patienten mit einem solchen BCI-System kommunizieren können, indem sie metabolische Hirnsignale und einfache reflexive Lernaufgaben verwenden. Schließlich werden Gehirn-Maschine-Schnittstellen und Rehabilitation bei chronischem Schlaganfall beschrieben und gezeigt, dass chronische Schlaganfallpatienten ohne jede Restbewegung der oberen Extremität eine erstaunliche Wiederherstellung der motorischen Funktion sowohl auf der motorischen als auch auf neuronaler Ebene mit BCI erreichen können. Nach umfangreichem BCI-Training kombiniert mit verhaltensorientierter Physiotherapie konnte eine signifikante Verbesserung der motorischen Funktion bei dieser bisher unbehandelbaren Lähmungen erreicht werden. Zusammenfassend lässt sich sagen, dass die klinischen Anwendungen von Gehirn-Maschine-Schnittstellen bei gut definierten und umschriebenen neurologischen Erkrankungen überraschend positive Wirkungen gezeigt haben. Die Anwendung von Gehirn-Computer-Schnittstellen bei psychiatrischen und klinisch-psychologischen Störungen hat bisher jedoch nicht zu einer wesentlichen Verbesserung dieser komplexen Verhaltensstörungen geführt. Brain-Computer Interfaces (BCI) use neuroelectric and metabolic brain activity to activate peripheral devices and computers without mediation of the motor system. In order to activate the BCI persons have to learn a certain amount of brain control. Self-regulation of brain activity was found to follow the principles of skill learning and instrumental conditioning. This review focuses on the clinical application of brain-computer interfaces in paralyzed patients with locked-in syndrome or/and complete locked-in syndrome (CLIS). It was shown that EEG-based brain-computer interfaces allow selection of letters and words in a computer menue with different types of EEG signals. However, in patients with complete locked-in syndrome without any muscular control, particularly of eye movements, classical, EEG-based brain-computer interfaces were not successful. Even after implantation of electrodes in the human brain, CLIS patients were unable to communicate. We developed a theoretical model explaining this fundamental deficit in instrumental learning of brain control and voluntary communication: patients in complete paralysis extinguish goal-directed response-oriented thinking and intentions. Therefore a reflexive classical conditioning procedure was developed and metabolic brain signals measured with Near Infrared-Spectroscopy were used in CLIS patients to answer simple questions with a “yes”- or “no”-brain response. The data collected so far are promising and show that for the first time CLIS patients communicate with such a BCI system using metabolic brain signals and simple reflexive learning tasks. Finally, brain machine interfaces and rehabilitation in chronic stroke are described demonstrating in chronic stroke patients without any residual upper limb movement a surprising recovery of motor function on the motor level as well as on the brain level. After extensive combined BMI training with behaviorally oriented physiotherapy significant improvement in motor function was shown in these previously intractable paralysis. In conclusion, clinical application of brain machine interfaces in well-defined and circumscribed neurological disorders have demonstrated surprisingly positive effects. The application of BCIs to psychiatric and clinical-psychological problems, however, at present did not result in substantial improvement of complex behavioral disorders.

Simultaneous NIRS and kinematics study of planning and execution of motor skill task: towards cerebral palsy rehabilitation

Cerebral palsy (CP) is a term that describes a group of motor impairment syndromes secondary to genetic and/or acquired disorders of the developing brain. In the current study, NIRS and motion capture were used simultaneously to correlate the brain’s planning and execution activity during and with arm movement in healthy individual. The prefrontal region of the brain is non-invasively imaged using a custom built continuous-wave based near infrared spectroscopy (NIRS) system. The kinematics of the arm movement during the studies is recorded using an infrared based motion capture system, Qualisys. During the study, the subjects (over 18 years) performed 30 sec of arm movement followed by 30 sec rest for 5 times, both with their dominant and non-dominant arm. The optical signal acquired from NIRS system was processed to elucidate the activation and lateralization in the prefrontal region of participants. The preliminary results show difference, in terms of change in optical response, between task and rest in healthy adults. Currently simultaneous NIRS imaging and kinematics data are acquired in healthy individual and individual with CP in order to correlate brain activity to arm movement in real-time. The study has significant implication in elucidating the evolution in the functional activity of the brain as the physical movement of the arm evolves using NIRS. Hence the study has potential in augmenting the designing of training and hence rehabilitation regime for individuals with CP via kinematic monitoring and imaging brain activity.

Non-invasive Optical Imaging technology: Breast cancer imaging and functional brain mapping

In our Optical Imaging Laboratory, hand-held based optical imaging devices are developed towards breast cancer imaging studies. In parallel, the optical devices are modified to perform dynamic functional brain mapping studies, particular in the areas of autism and cerebral palsy.

Temporal Mapping and Connectivity using NIRS for Language Related Tasks

Near Infrared Spectroscopy (NIRS) offers an invaluable tool to monitor the functionality of the brain. NIRS with its high temporal resolution and good spatial resolution has been applied towards various area of brain research in order to map the cortical regions of the brain. The present study is aimed at using NIRS to understand the functionality of the temporal cortex in response to language-related tasks. A 32-channel NIRS system (Imagent ISS Inc.) is used to perform experimental studies on 15 normal adults. A block-design based Word Expression and Word Reception tasks were independently presented to the participants during the imaging study. Unlike past research where only the brain activation was determined for language tasks, in the current study the activation, connectivity, and lateralization in the temporal cortex are correlated. In the future, the work is focused to target the pediatric epileptic populations, where understanding the temporal brain functionality in response to language is essential in pre-surgical clinical environment.