| 1. |
- Eklund, Anders, et al.
(författare)
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Balancing an Inverted Pendulum by Thinking A Real-Time fMRI Approach
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present a method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverse pendulum by activating the left or right hand or resting. The brain activity is classified each second by a neural network and the classification is sent to a pendulum simulator to change the force applied to the pendulum. The state of the inverse pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverse pendulum both with real activity and imagined activity. The developments here have a potential to aid people with communication disabilities e.g., locked in people. It might also be a tool for stroke patients to be ableto train the damaged brain area and get real-time feedback of when they do it right.
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| 2. |
- Eklund, Anders, et al.
(författare)
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Using Real-Time fMRI to Control a Dynamical System
- 2009
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Ingår i: ISMRM 17th Scientific Meeting & Exhibition. - Linköping : Linköping University Electronic Press.
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Konferensbidrag (refereegranskat)abstract
- We present e method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverse pendulum by activating the left or right hand or resting. The brain activity is clasified each second by a neural network and the classification is sent to a pendulum simulator to change the state of the pendulum. The state of the inverse pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverse pendulum during a 7 minute test run.
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| 3. |
- Eklund, Anders, 1981-, et al.
(författare)
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Using Real-Time fMRI to Control a Dynamical System by Brain Activity Classification
- 2009. - 1
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Ingår i: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2009. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642042676 - 9783642042683 ; , s. 1000-1008
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Konferensbidrag (refereegranskat)abstract
- We present a method for controlling a dynamical system using real-time fMRI. The objective for the subject in the MR scanner is to balance an inverted pendulum by activating the left or right hand or resting. The brain activity is classified each second by a neural network and the classification is sent to a pendulum simulator to change the force applied to the pendulum. The state of the inverted pendulum is shown to the subject in a pair of VR goggles. The subject was able to balance the inverted pendulum during several minutes, both with real activity and imagined activity. In each classification 9000 brain voxels were used and the response time for the system to detect a change of activity was on average 2-4 seconds. The developments here have a potential to aid people with communication disabilities, such as locked in people. Another future potential application can be to serve as a tool for stroke and Parkinson patients to be able to train the damaged brain area and get real-time feedback for more efficient training.
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| 4. |
- Lundström, Claes, 1973-, et al.
(författare)
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The alpha-histogram: Using Spatial Coherence to Enhance Histograms and Transfer Function Design
- 2006
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Ingår i: Proceedings Eurographics/IEEE Symposium on Visualization 2006, Lisbon, Portugal. ; , s. 227-234
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The high complexity of Transfer Function (TF) design is a major obstacle to widespread routine use of Direct Volume Rendering, particularly in the case of medical imaging. Both manual and automatic TF design schemes would benefit greatly from a fast and simple method for detection of tissue value ranges. To this end, we introduce the a-histogram, an enhancement that amplifies ranges corresponding to spatially coherent materials. The properties of the a-histogram have been explored for synthetic data sets and then successfully used to detect vessels in 20 Magnetic Resonance angiographies, proving the potential of this approach as a fast and simple technique for histogram enhancement in general and for TF construction in particular.
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| 5. |
- Ohlsson, Henrik, 1981-, et al.
(författare)
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Enabling Bio-Feedback using Real-Time fMRI
- 2008
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Ingår i: 47th IEEE Conference on Decision and Control, 2008, CDC 2008. - Linköping : IEEE. - 9781424431236 ; , s. 3336-3341
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Konferensbidrag (refereegranskat)abstract
- Despite the enormous complexity of the human mind, fMRI techniques are able to partially observe the state of a brain in action. In this paper we describe an experimental setup for real-time fMRI in a bio-feedback loop. One of the main challenges in the project is to reach a detection speed, accuracy and spatial resolution necessary to attain sufficient bandwidth of communication to close the bio-feedback loop. To this end we have banked on our previous work on real-time filtering for fMRI and system identification, which has been tailored for use in the experiment setup. In the experiments presented the system is trained to estimate where a person in the MRI scanner is looking from signals derived from the visual cortex only. We have been able to demonstrate that the user can induce an action and perform simple tasks with her mind sensed using real-time fMRI. The technique may have several clinical applications, for instance to allow paralyzed and "locked in" people to communicate with the outside world. In the meanwhile, the need for improved fMRI performance and brain state detection poses a challenge to the signal processing community. We also expect that the setup will serve as an invaluable tool for neuro science research in general.
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| 6. |
- Allwood, Carl Martin, 1952, et al.
(författare)
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Eyewitnesses under influence: How feedback affect the realism in confidence
- 2006
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Ingår i: Psychology, Crime & Law. - : Informa UK Limited. ; 12:1, s. 25-38
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of two types of feedback (confirmatory and disconfirmatory) on the accuracy in witness’ confidence judgements of their event memory. Overall the witnesses evidenced overconfidence both when they received feedback and in the control condition (no feedback). The results showed that confirmatory feedback caused higher overconfidence, compared both with when receiving disconfirmatory and no feedback. The results suggest that the impact of feedback on the accuracy of confidence judgments show the same pattern of results for event memory as for line-up identification tasks. Finally, when witnesses rated the total number of questions that they had answered correctly they gave fairly correct estimates compared with their actual number of correct answers.
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| 7. |
- Andersson, Eva, 1955, et al.
(författare)
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Incidence of asthma among workers exposed to sulfur dioxide and other irritant gases
- 2006
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Ingår i: European Respiratory Journal. - : European Respiratory Society (ERS). - 0903-1936 .- 1399-3003. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate whether repeated peak exposure (gassings) to sulphur dioxide (SO2) and other irritant gases increases the risk of new-onset asthma. A questionnaire was sent to 4,112 sulphite workers, of whom 1,919 completed the questionnaire and 396 completed the short-form questionnaire, which was sent out as a last reminder. A sample of 130 nonrespondents completed a telephone interview using the short-form questionnaire. The incidence of adult-onset, physician-diagnosed asthma during employment duration was analysed in relation to exposure to SO2 and gassings giving rise to respiratory symptoms. Incidence rates, as well as incidence rate ratios with 95% confidence interval (CI), were calculated. Further Cox regression models were used allowing assessment of hazard ratios (HR) stratified for sex and adjusted for atopy, smoking habits and age. The incidence rate for asthma among sulphite mill workers reporting gassings of SO2 was 6.2 out of 1,000 person-yrs, compared with 1.9 out of 1,000 person-yrs among subjects unexposed to SO2 and any gassings (HR (95% CI) 4.0 (2.1-7.7)). Among males reporting gassings to SO2, the HR (95% CI) for asthma was 5.8 (2.6-13) compared with unexposed males. In conclusion, repeated peak exposure to sulphur dioxide increased the incidence of asthma during work in sulphite pulp mills, which supports the hypothesis of irritant-induced asthma.
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| 8. |
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| 9. |
- Brun, Anders, 1976-, et al.
(författare)
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A tensor-like representation for averaging, filtering and interpolation of 3D object orientation data
- 2005
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Ingår i: Image Processing, 2005. ICIP 2005. IEEE International Conference on (Volume:3 ). - 0780391349 ; , s. 1092-1095
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Konferensbidrag (refereegranskat)abstract
- Averaging, filtering and interpolation of 3-D object orientation data is important in both computer vision and computer graphics, for instance to smooth estimates of object orientation and interpolate between keyframes in computer animation. In this paper we present a novel framework in which the non-linear nature of these problems is avoided by embedding the manifold of 3-D orientations into a 16-dimensional Euclidean space. Linear operations performed in the new representation can be shown to be rotation invariant, and defining a projection back to the orientation manifold results in optimal estimates with respect to the Euclidean metric. In other words, standard linear filters, interpolators and estimators may be applied to orientation data, without the need for an additional machinery to handle the non-linear nature of the problems. This novel representation also provides a way to express uncertainty in 3-D orientation, analogous to the well known tensor representation for lines and hyperplanes.
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| 10. |
- Brun, Anders, 1976-, et al.
(författare)
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Fast manifold learning based on Riemannian normal coordinates
- 2005
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Ingår i: Image Analysis. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540263203 - 9783540315667 ; , s. 920-
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Konferensbidrag (refereegranskat)abstract
- We present a novel method for manifold learning, i.e. identification of the low-dimensional manifold-like structure present in a set of data points in a possibly high-dimensional space. The main idea is derived from the concept of Riemannian normal coordinates. This coordinate system is in a way a generalization of Cartesian coordinates in Euclidean space. We translate this idea to a cloud of data points in order to perform dimension reduction. Our implementation currently uses Dijkstra’s algorithm for shortest paths in graphs and some basic concepts from differential geometry. We expect this approach to open up new possibilities for analysis of e.g. shape in medical imaging and signal processing of manifold-valued signals, where the coordinate system is “learned” from experimental high-dimensional data rather than defined analytically using e.g. models based on Lie-groups.
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