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Kita K.,University of Tokyo | Kita K.,Computational Neuroscience Laboratories | Kato R.,University of Electro - Communications | Yokoi H.,University of Electro - Communications
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC'10 | Year: 2010

To evaluate the proficiency level of an operating myoelectric hand, we proposed an evaluation index consisting of the accuracy and the reproducibility of electromyography (EMG) signal patterns. Our proposed method is not an absolute evaluation because we use bio-signals, so it is necessary to verify the correlation between the proposed index and performance evaluation to confirm the usefulness of the index. Therefore, we conducted classification tests on eight forearm motions and verified the correlation between the proposed method and the classification rate. There was a strong correlation between the accuracy and the classification rate. In addition, if the accuracy was high, high reproducibility led to an increase in the classification rate. We conclude that the proposed method can evaluate the proficiency level of a myoelectric hand. © 2010 IEEE.

Callan D.E.,Computational Neuroscience Laboratories | Schweighofer N.,University of Southern California
Human Brain Mapping | Year: 2010

Spaced presentations of to-be-learned items during encoding leads to superior long-term retention over massed presentations. Despite over a century of research, the psychological and neural basis of this spacing effect however is still under investigation. To test the hypotheses that the spacing effect results either from reduction in encoding-related verbal maintenance rehearsal in massed relative to spaced presentations (deficient processing hypothesis) or from greater encoding-related elaborative rehearsal of relational information in spaced relative to massed presentations (encoding variability hypothesis), we designed a vocabulary learning experiment in which subjects encoded paired-associates, each composed of a known word paired with a novel word, in both spaced and massed conditions during functional magnetic resonance imaging. As expected, recall performance in delayed cued-recall tests was significantly better for spaced over massed conditions. Analysis of brain activity during encoding revealed that the left frontal operculum, known to be involved in encoding via verbal maintenance rehearsal, was associated with greater performance-related increased activity in the spaced relative to massed condition. Consistent with the deficient processing hypothesis, a significant decrease in activity with subsequent episodes of presentation was found in the frontal operculum for the massed but not the spaced condition. Our results suggest that the spacing effect is mediated by activity in the frontal operculum, presumably by encoding-related increased verbal maintenance rehearsal, which facilitates binding of phonological and word level verbal information for transfer into long-term memory. © 2009 Wiley-Liss, Inc.

Hosoya H.,Computational Neuroscience Laboratories | Hosoya H.,Japan Science and Technology Agency | Hyvarinen A.,Aalto University
Journal of Neuroscience | Year: 2015

Previous theoretical and experimental studies have demonstrated tight relationships between natural image statistics and neural representations in V1. In particular, receptive field properties similar to simple and complex cells have been shown to be inferable from sparse coding of natural images. However, whether such a relationship exists in higher areas has not been clarified. To address this question for V2, we trained a sparse coding model that took as input the output of a fixed V1-like model, which was in its turn fed a large variety of natural image patches as input. After the training, the model exhibited response properties that were qualitatively and quantitatively compatible with three major neurophysiological results on macaque V2, as follows: (1) homogeneous and heterogeneous integration of local orientations (Anzai et al., 2007); (2) a wide range of angle selectivities with biased sensitivities to one component orientation (Ito and Komatsu, 2004); and (3) exclusive length and width suppression (Schmid et al., 2014). The reproducibility was stable across variations in several model parameters. Further, a formal classification of the internal representations of the model units offered detailed interpretations of the experimental data, emphasizing that a novel type of model cell that could detect a combination of local orientations converging toward a single spatial point (potentially related to corner-like features) played an important role in reproducing tuning properties compatible with V2. These results are consistent with the idea that V2 uses a sparse code of natural images. © 2015, the authors.

Kodl J.,Imperial College London | Ganesh G.,Japan National Institute of Information and Communications Technology | Ganesh G.,Computational Neuroscience Laboratories | Burdet E.,Imperial College London
PLoS ONE | Year: 2011

Traditionally motor studies have assumed that motor tasks are executed according to a single plan characterized by regular patterns, which corresponds to the minimum of a cost function in extrinsic or intrinsic coordinates. However, the novel via-point task examined in this paper shows distinct planning and execution stages in motion production and demonstrates that subjects randomly select from several available motor plans to perform a task. Examination of the effect of pre-training and via-point orientation on subject behavior reveals that the selection of a plan depends on previous movements and is affected by constraints both intrinsic and extrinsic of the body. These results provide new insights into the hierarchical structure of motion planning in humans, which can only be explained if the current models of motor control integrate an explicit plan selection stage. © 2011 Kodl et al.

Su E.L.M.,Imperial College London | Su E.L.M.,University of Technology Malaysia | Ganesh G.,Imperial College London | Ganesh G.,National Institute of Communication and Information Technology | And 4 more authors.
Proceedings - IEEE International Workshop on Robot and Human Interactive Communication | Year: 2010

This study examines effects of learning 3D micromanipulation in an unstable dynamic environment. A test group trained in an unstable divergent force field while a control group trained the movement in the null force field. The subjects in the test group increased the success rate, in contrast to the control group which had similar rate after training. The error and its standard deviation decreased in the test group but not in the control group. In summary, training in unstable dynamics enable subjects to become more accurate, in contrast to training using only visual feedback. © 2010 IEEE.

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