No description available.

No description available.

Event-related potentials have been found to be a useful indicator of brain states and brain abnormality. The contingent negative variation, P300 and bereitschafts potential are well researched event-related potentials of particular interest. Many factors have to be considered in the design of measurement systems to record multiple channels of these signals accurately. The correlation between channels must be high and channel noise and distortion must be minimal, whilst the system as a whole must meet the requirements of the medical safety standards. For further research there was found to be a requirement for a dedicated thirty-two channel ERP measurement system that met these criteria. This has been achieved in a PC based system that utilises simultaneous sampling of all channels, and filters that extend to very low frequencies. Software control of the system enables user adjustment of recording parameters and paradigm implementation. Data processing using high level software enables digital signal processing techniques to be applied for further noise removal and signal analysis. The system has been tested using synthetically generated signals and by limited recording of the three ERPs. The results prove that the system is a suitable tool for high accuracy, multi-channel recording of ERPs.

An electroencephalographic (EEG) protocol was used to examine cerebral activity in the moments proceeding self paced motor performance. Throughout the series of investigations, power in the alpha waveband (8-13 Hz) was used as the dependant variable. In the first investigation, subjects completed a variety of stereotyped 'left and right brain' tasks. These tasks induced a reliable and predictable pattern of lateralised activity. Furthermore, tasks categorised as 'right brain' were shown to induce a more consistent effect. In the second investigation, expert Karate athletes performed a number of Karate specific tasks together with a skill acquisition and cognitive task condition. Significant increases in alpha band power, mediated by task difficulty, were found to be associated with one category of task. In the third study, subjects completed a series of novel tasks, designed to systematically vary the effort and accuracy demands. A significant decrease in alpha band power was shown to be associated with preparation for the asymmetrical high effort task, namely a leg extension against resistance. Outcome of the high accuracy condition was found to significantly mediate alpha band power immediately prior to performance. In the final investigation, the alpha band powers of cricketers, non-cricketing sportsmen and non-sportsmen were compared as they performed a variety of Cricket related, throwing tasks. Significant differences were detected between the different groups and between the different tasks. Once again, success was found to mediate the pattern of alpha band power. It was concluded that the effects observed were probably due to changes in the Rolandic Wicket or Mu rhythm generated in the central and pre-central regions.

No description available.

No description available.

Many tasks in the real world require simultaneous processing of mental information alongside physical activity. Most of researchers have studied the impact of physical activities on simple cognitive tasks, but have neglected other important influences (such as different attentional resource pools, as well as gender). Therefore, this thesis proposes a new model that investigates the combined impact of physical and mental workload on different attentional resources (visual and auditory, verbal and spatial). This thesis presents three experimental studies that examined the effects of physical and mental workload interactions, as well as gender, on visual tasks performance and auditory tasks. This thesis uses different methods to evaluate the impacts of workload interactions on task performance: performance measure, physiological parameters and brain activity (Near-Infrared Spectroscopy (NIRS) method) and subjective assessment tools. Finally, this thesis translates the experimental studies setting into a field study to validate the model. Based on the experimental results, this research creates a new theoretical model that illustrates in general that physical activity is beneficial for performance on cognitive tasks (visual and auditory), particularly at low levels of workload interactions, while other workload interactions lead to worse performance on cognitive tasks. However, when physical activity was introduced, performance at the medium level of mental workload was equivalent to that in the low mental workload condition; furthermore, at the low mental workload, there were no differences in performance between low and medium physical workloads. The general pattern of results suggests that physical workload leads to better performance in these medium-demand conditions up to the higher level in the low-demand condition. A mechanism for this effect is proposed based on physiological arousal and brain oxygenation. This thesis further suggests that the NIRS is a valuable technique to reflect the influence of physical and mental workload interactions on brain activity. Finally, this thesis demonstrates the translation of experimental findings into a field setting to verify the new model as well as to make recommendations for job design.

The effects of external electric fields (EEF) on brain activity in anesthetized rats were studied. The field strengths used, 9 kV/m and 5 kV/m, both D.C. and A.C. (60Hz) were in the range of those measured beneath current overhead transmission lines. Brain activity was monitored from surface electrodes and from electrodes stereotaxically implanted in the posterior-lateral portion of the hypothalamus. It was found that 9 kV/m and 5 kV/m EEF's both D.C. and A.C. brought about statistically significant changes in hypothalamic activity, however, the effects were bi-directional, (i.e. increases and decreases). Only seven of the 60 animals exposed showed changes in the EEG recorded with surface electrodes. The data clearly indicate that (1) anesthetized animals do respond to a change in the external electric field around them, (2) the hypothalamus may contain special electro-receptors that, in turn, may alter various other physiological processes, and (3) the data indicates the need for further research to help government agencies to establish more adequate safety guidelines.

How is information organized in the brain during natural reading? Where and when do the required processes occur, such as the perception of individual words and the construction of sentence meanings. How are semantics, syntax and higher-level narrative structure represented? Answering these questions is core to understanding how the brain processes language and organizes complex information. However, due to the complexity of language processing, most brain imaging studies focus only on one of these questions using highly controlled stimuli which may not generalize beyond the experimental setting. This thesis proposes an alternative framework to study language processing. We acquire data using a naturalistic reading paradigm, annotate the presented text using natural language processing tools and predict brain activity with machine learning techniques. Finally, statistical testing is used to form rigorous conclusions. We also suggest the use of direct non-parametric hypothesis tests that do not rely on any model assumptions, and therefore do not suffer from model misspecification. Using our framework, we construct a brain reading map from functional magnetic resonance imaging data of subjects reading a chapter of a popular book. This map represents regions that our model reveals to be representing syntactic, semantic, visual and narrative information. Using this single experiment, our approach replicates many results from a wide range of classical studies that each focus on one aspect of language processing. We extend our brain reading map to include temporal dynamics as well as spatial information by using magnetoencephalography. We obtain a spatio-temporal picture of how successive words are processed by the brain. We show the progressive perception of each word in a posterior to anterior fashion. For each region along this pathway we show a differentiation of the word properties that best explain its activity.

Darbo tikslas - išanalizuoti, kaip Lietuvos studentai vertina smegenų veiklą stimuliuojančių medžiagų vartojimą. Susipažinta su neuroetinėmis smegenų veiklą stimuliuojančių medžiagų/preparatų (SVSP) vartojimo problemomis pasaulyje ir Lietuvoje, palygintos SVSP vartojimo bei vertinimo tendencijos Lietuvoje ir užsienio šalyse. Atlikta sociologinė apklausa, kurioje dalyvavo 531 studentas. Respondentams pateikta 44 klausimų anketa. Apklausti 7 universitetinių ir 3 neuniversitetinių aukštųjų mokyklų studentai. Rezultatai apdoroti SPSS programa. Nustatyta, jog SVSP yra aktuali tema Lietuvos studentams. 40,9 proc. respondentų vartoja arba yra vartoję SVSP. SVSP vartojimo problematika Lietuvoje ir pasaulyje skiriasi. Vakarų šalyse opiausios problemos: piktnaudžiavimas smegenų veiklą stimuliuojančiais vaistais, nekorektiška reklama, socialinė nelygybė tarp vartojančiųjų ir nevartojančiųjų SVSP. Lietuvoje nesilaikoma ženklinimo ir reklamos reikalavimų. Dauguma apklausos respondentų SVSP vartojime neįžvelgia socialinių, teisinių ar etinių problemų, tačiau tai gali sąlygoti išsamios ir teisingos informacijos trūkumas, nes 80,4 proc. respondentų apie juos sužinojo iš reklamos. Tikėtina, kad greitėjant gyvenimo tempui, smegenų veiklą stimuliuojančių preparatų vartojimas Lietuvoje didės, o vartotojams trūkstant išsamios ir korektiškos informacijos apie šiuos preparatus, teisinės, etinės ir socialinės problemos gali paaštrėti. / The aim of this research was to perfom an analysis on Lithuanian students evaluation of brain activity enhancing substances usage. Neuroethical problems araising while using brain activity enhancers were reviewed as well as tendencies of usage and evaluation were compared in Lithuania and other countries. Sociological survey has been performed in 7 universities and 3 non-university higher education institutions. 531 student filled-in a questionaire which contained 44 questions. Data has been analyzed using SPSS program. The usage of brain activity enhancing substances is a relevant topic for Lithuanian students. Brain enhancers are or have been used by 40,9 percent respondents. Although problems regarding brain activity enhancers usage are different in Lithuania and Western countries. Relevant problems in economical developed countries are misuse of brain enhancers, incorrect advertisement, social inequality. In Lithuania labelling and advertising requirement often are not followed. Majority of respondents do not think that using brain activity enhancers can cause any social, ethical or legal problems. Although such oppinion can be influenced by lack of comprehensive information. Information about brain activity enhancers was recieved through commercial means by 80,4 percent respondents. It can be predicted that usage of brain activity enhancers will grow together with rapid life-style. And since there is lack of comprehensive information regarding brain activity enhancers... [to full text]