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Ragnehed, Mattias
Publications (10 of 20) Show all publications
van Ettinger-Veenstra, H., Ragnehed, M., McAllister, A., Lundberg, P. & Engström, M. (2012). Right-hemispheric cortical contributions to language ability in healthy adults. Brain and Language, 120(3), 395-400
Open this publication in new window or tab >>Right-hemispheric cortical contributions to language ability in healthy adults
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2012 (English)In: Brain and Language, ISSN 0093-934X, E-ISSN 1090-2155, Vol. 120, no 3, p. 395-400Article in journal (Refereed) Published
Abstract [en]

In this study we investigated the correlation between individual linguistic ability based on performance levels and their engagement of typical and atypical language areas in the brain. Eighteen healthy subjects between 21 and 64 years participated in language ability tests, and subsequent functional MRI scans measuring brain activity in response to a sentence completion and a word fluency task. Performance in both reading and high-level language tests correlated positively with increased right-hemispheric activation in the inferior frontal gyrus (specifically Brodmann area 47), the dorsolateral prefrontal cortex (DLPFC), and the medial temporal gyrus (Brodmann area 21). In contrast, we found a negative correlation between performance and left-hemispheric DLPFC activation.

Our findings indicate that the right lateral frontal and right temporal regions positively modulate aspects of language ability.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
Linguistics; Functional Magnetic Resonance Imaging; Functional laterality; Task performance; Reading; Fluency
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-73623 (URN)10.1016/j.bandl.2011.10.002 (DOI)000301759100019 ()22115846 (PubMedID)
Note
funding agencies|Stahls Foundation||Strategic Research Area of the Center of Medical Image Science and Visualization (CMIV) at Linkoping University, Sweden||Available from: 2012-01-10 Created: 2012-01-10 Last updated: 2017-12-08
Fornander, L., Nyman, T., Hansson, T., Ragnehed, M. & Brismar, T. (2010). Age- and time-dependent effects on functional outcome and cortical activation pattern in patients with median nerve injury: a functional magnetic resonance imaging study Clinical article. Journal of Neurosurgery, 113(1), 122-128
Open this publication in new window or tab >>Age- and time-dependent effects on functional outcome and cortical activation pattern in patients with median nerve injury: a functional magnetic resonance imaging study Clinical article
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2010 (English)In: Journal of Neurosurgery, ISSN 0022-3085, E-ISSN 1933-0693, Vol. 113, no 1, p. 122-128Article in journal (Refereed) Published
Abstract [en]

Object. The authors conducted a study to determine age- and time-dependent effects on the functional outcome after median nerve injury and repair and how such effects are related to changes in the pattern of cortical activation in response to tactile stimulation of the injured hand. Methods. The authors studied 11 patients with complete unilateral median nerve injury at the wrist repaired with epineural suture. In addition, 8 patients who were reported on in a previous study were included in the statistical analysis. In the entire study cohort, the mean age at injury was 23.3 +/- 13.4 years (range 7-57 years) and the time after injury ranged from 1 to 11 years. Sensory perception was measured with the static 2-point discrimination test and monofilaments. Functional MR imaging was conducted during tactile stimulation (brush strokes) of Digits II-III and IV-V of both hands, respectively. Results. Tactile sensation was diminished in the median territory in all patients. The strongest predictor of 2-point discrimination was age at injury (p less than 0.0048), and when this was accounted for in the regression analysis, the other age- and time-dependent predictors had no effect. The activation ratios (injured/healthy hand) for Digit II-III and Digit IV-V stimulation were positively correlated (rho 0.59, p less than 0.011). The activation ratio for Digit II-III stimulation correlated weakly with time after injury (p less than 0.041). The activation ratio of Digits IV-V correlated weakly with both age at injury (p less than 0.048) and time after injury (p less than 0.033), but no predictor reached significance in the regression model. The mean ratio of ipsi- and contralateral hemisphere activation after stimulation of the injured hand was 0.55, which was not significantly different from the corresponding ratio of the healthy hand (0.66). Conclusions. Following a median nerve injury (1-11 years after injury) there may be an initial increase in the volume of the cortical representation, which subsequently declines during the restoration phase. These dynamic changes may involve both median and ulnar nerve cortical representation, because both showed negative correlation with time after injury. These findings are in agreement with animal studies showing that cortical plasticity is an important mechanism for functional recovery after peripheral nerve injury and repair.

Place, publisher, year, edition, pages
American Association of Neurological Surgeons, 2010
Keywords
median nerve; hand injury; neuronal plasticity; functional magnetic resonance imaging
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-58291 (URN)10.3171/2009.10.JNS09698 (DOI)000279107300030 ()
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
Engström, M., Karlsson, M., Crone, M., Ragnehed, M., Antepohl, W., Landtblom, A.-M. & Lundberg, P. (2010). Clinical fMRI of language function in aphasic patients: Reading paradigm successful, while word generation paradigm fails. Acta Radiologica, 51(6), 679-686
Open this publication in new window or tab >>Clinical fMRI of language function in aphasic patients: Reading paradigm successful, while word generation paradigm fails
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2010 (English)In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 51, no 6, p. 679-686Article in journal (Refereed) Published
Abstract [en]

Background: In fMRI examinations, it is very important to select appropriate paradigms assessing the brain function of interest. In addition, the patients ability to perform the required cognitive tasks during fMRI must be taken into account. Purpose: To evaluate two language paradigms, word generation and sentence reading for their usefulness in examinations of aphasic patients and to make suggestions for improvements of clinical fMRI. Material and Methods: Five patients with aphasia after stroke or trauma sequelae were examined by fMRI. The patients language ability was screened by neurolinguistic tests and elementary pre-fMRI language tests. Results: The sentence-reading paradigm succeeded to elicit adequate language-related activation in perilesional areas whereas the word generation paradigm failed. These findings were consistent with results on the behavioral tests in that all patients showed very poor performance in phonemic fluency, but scored well above mean at a reading comprehension task. Conclusion: The sentence-reading paradigm is appropriate to assess language function in this patient group, while the word-generation paradigm seems to be inadequate. In addition, it is crucial to use elementary pre-fMRI language tests to guide the fMRI paradigm decision.

Place, publisher, year, edition, pages
Informa Healthcare, 2010
Keywords
fMRI; aphasia; language; word generation; sentence completion
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-58176 (URN)10.3109/02841851003753456 (DOI)000280219400012 ()
Note
Original Publication: Maria Engström, Marie Karlsson, Marie Crone, Mattias Ragnehed, Wolfram Antepohl, Anne-Marie Landtblom and Peter Lundberg, Clinical fMRI of language function in aphasic patients: Reading paradigm successful, while word generation paradigm fails, 2010, Acta Radiologica, (51), 6, 679-686. http://dx.doi.org/10.3109/02841851003753456 Copyright: Informa Healthcare http://informahealthcare.com/Available from: 2010-08-11 Created: 2010-08-09 Last updated: 2017-12-12
Engström, M., Ragnehed, M. & Lundberg, P. (2010). On the Advantage of Data Driven Analysis in Aphasic Patients with Severe Language Latncy. Paper presented at ISMRM 2010, Stockholm.
Open this publication in new window or tab >>On the Advantage of Data Driven Analysis in Aphasic Patients with Severe Language Latncy
2010 (English)Conference paper, Published paper (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-57137 (URN)
Conference
ISMRM 2010, Stockholm
Available from: 2010-06-10 Created: 2010-06-10 Last updated: 2014-10-02
van Ettinger-Veenstra, H. M., Ragnehed, M., Hällgren, M., Karlsson, T., Landtblom, A.-M., Lundberg, P. & Engström, M. (2010). Right-hemispheric brain activation correlates to language performance. NEUROIMAGE, 49(4), 3481-3488
Open this publication in new window or tab >>Right-hemispheric brain activation correlates to language performance
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2010 (English)In: NEUROIMAGE, ISSN 1053-8119, Vol. 49, no 4, p. 3481-3488Article in journal (Refereed) Published
Abstract [en]

Language function in the right-hemispheric homologues of Brocas and Wernickes areas does not only correlate with left-handedness or pathology, but occurs naturally in right-handed healthy subjects as well. In the current study, two non-invasive methods of assessing language lateralization are correlated with behavioral results in order to link hemispheric dominance to language ability in healthy subjects. Functional magnetic resonance imaging (fMRI) together with a sentence-completion paradigm was used to determine region-specific lateralization indices in the left- and right-sided Brocas and Wernickes areas, the frontal temporal lobe, the anterior cingulate cortex and the parietal lobe. In addition, dichotic listening results were used to determine overall language lateralization and to strengthen conclusions by correlating with fMRI indices. Results showed that fMRI lateralization in the superior parietal, the posterior temporal, and the anterior cingulate cortices correlated to dichotic listening. A decreased right ear advantage (REA), which indicates less left- hemispheric dominance in language, correlated with higher performance in most administered language tasks, including reading, language ability, fluency, and non-word discrimination. Furthermore, right hemispheric involvement in the posterior temporal lobe and the homologue of Brocas area suggests better performance in behavioral language tasks. This strongly indicates a supportive role of the right-hemispheric counterparts of Brocas and Wernickes areas in language performance.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-53932 (URN)10.1016/j.neuroimage.2009.10.041 (DOI)000274064500059 ()
Note
Original Publication: Helene M van Ettinger-Veenstra, Mattias Ragnehed, Mathias Hällgren, Thomas Karlsson, Anne-Marie Landtblom, Peter Lundberg and Maria Engström, Right-hemispheric brain activation correlates to language performance, 2010, NEUROIMAGE, (49), 4, 3481-3488. http://dx.doi.org/10.1016/j.neuroimage.2009.10.041 Copyright: Elsevier Science B.V., Amsterdam http://www.elsevier.com/Available from: 2010-02-12 Created: 2010-02-12 Last updated: 2014-10-02
Ragnehed, M., Dahlqvist Leinhard, O., Pihlsgård, J., Wirell, S., Sökjer, H., Fägerstam, P., . . . Lundberg, P. (2010). Visual Grading of 2D and 3D fMRI compared to image based descriptive measures. European Radiology, 20(3), 714-724
Open this publication in new window or tab >>Visual Grading of 2D and 3D fMRI compared to image based descriptive measures
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2010 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 20, no 3, p. 714-724Article in journal (Refereed) Published
Abstract [en]

A prerequisite for successful clinical use of functional Magnetic Resonance Imaging (fMRI) is the selection of an appropriate imaging sequence. In this paper, 2D and 3D fMRI sequences were compared using different image quality assessment methods. Descriptive image measures, such as activation volume and temporal signal-to-noise ratio (TSNR), were compared with results from Visual Grading Characteristics (VGC) analysis of the fMRI results. It was found that significant differences in activation volume and TSNR were not directly reflected by differences in VGC scores. The results suggest that better performance on descriptive image measures is not always an indicator of improved diagnostic quality of the fMRI results. In conclusion, in addition to descriptive image measures, it is important to include measures of diagnostic quality when comparing different fMRI data acquisition methods.

Place, publisher, year, edition, pages
Berlin / Heidelberg: Springer, 2010
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-17994 (URN)10.1007/s00330-009-1578-0 (DOI)000274544800023 ()19727748 (PubMedID)
Note

The original publication is available at www.springerlink.com: Mattias Ragnehed, Olof Dahlqvist Leinhard, Johan Pihlsgård, Staffan Wirell, Hannibal Sökjer, Patrik Fägerstam, Bo Jiang, Örjan Smedby, Maria Engström and Peter Lundberg, Visual Grading of 2D and 3D fMRI compared to image based descriptive measures, 2010, European Radiology, (20), 3, 714-724. http://dx.doi.org/10.1007/s00330-009-1578-0 Copyright: Springer Science Business Media http://www.springerlink.com/

Available from: 2009-04-30 Created: 2009-04-30 Last updated: 2018-10-08Bibliographically approved
Ragnehed, M. (2009). Functional Magnetic Resonance Imaging for Clinical Diagnosis: Exploring and Improving the Examination Chain. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Functional Magnetic Resonance Imaging for Clinical Diagnosis: Exploring and Improving the Examination Chain
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Functional Magnetic Resonance Imaging (fMRI) is a relatively new imaging technique, first reported in 1992, which enables mapping of brain functions with high spatial resolution. Functionally active areas are distinguished by a small signal increase mediated by changes in local blood oxygenation in response to neural activity. The ability to non-invasively map brain function and the large number of MRI scanners quickly made the method very popular, and fMRI have had a huge impact on the study of brain function, both in healthy and diseased subjects.

The most common clinical application of fMRI is pre-surgical mapping of brain functions in order to optimise surgical interventions. The clinical fMRI examination procedure can be divided into four integrated parts: (1) patient preparation, (2) image acquisition, (3) image analysis and (4) clinical decision. In this thesis, important aspects of all parts of the fMRI examination procedure are explored with the aim to provide recommendations and methods for prosperous clinical usage of the technique.

The most important results of the thesis were: (I) administration of low doses of diazepam to reduce anxiety did not invalidate fMRI mapping results of primary motor and language areas, (II) the choice of visual stimuli equipment can have severe impact on the mapping of visual areas, (III) three-dimensional fMRI imaging sequences did not perform better than two-dimensional imaging sequences, (IV) adaptive spatial filtering can improve the fMRI data analysis, (V) clinical decisions should not be based on activation results from a single statistical threshold.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. p. 73
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1121
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-18095 (URN)978-91-7393-645-3 (ISBN)
Public defence
2009-06-02, Majoren, Brigaden Restaurang & Konferens, Brigadgatan 17, 587 58 Linköping, Linköping, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2009-05-06 Created: 2009-05-06 Last updated: 2014-10-02Bibliographically approved
Ragnehed, M., Engström, M., Knutsson, H., Axelsson Söderfeldt, B. & Lundberg, P. (2009). Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique. Journal of Magnetic Resonance Imaging, 29(1), 146-154
Open this publication in new window or tab >>Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique
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2009 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 29, no 1, p. 146-154Article in journal (Refereed) Published
Abstract [en]

Purpose: To validate the performance of an analysis method for fMRI data based on restricted canonical correlation analysis (rCCA) and adaptive filtering, and to increase the usability of the method by introducing a new technique for significance estimation of rCCA maps.

Materials and Methods: Activation data from a language task and also a resting state fMRI data were collected from eight volunteers. Data was analyzed using both the rCCA method and the General Linear Model (GLM). A modified Receiver Operating Characteristic (ROC) method was used to evaluate the performance of the different analysis methods. The area under a fraction of the ROC curve was used as a measure of performance. On resting state data the fraction of voxels above certain significance thresholds were used to evaluate the significance estimation method.

Results: The rCCA method scored significantly higher on the area under the ROC curve than the GLM. The fraction of activated voxels determined by thresholding according to the introduced significance estimation technique showed good agreement with the thresholds selected.

Conclusion: The rCCA method is an effective analysis tool for fMRI data and its usability is increased with the introduced significance estimation method.

Keywords
fMRI, GLM, canonical correlation analysis, thresholding, significance
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-16411 (URN)10.1002/jmri.21494 (DOI)000262168200019 ()
Available from: 2009-01-23 Created: 2009-01-23 Last updated: 2017-12-14Bibliographically approved
Ragnehed, M., Philsgård, J., Dahlqvist Leinhard, O., Smedby, Ö., Engström, M. & Lundberg, P. (2008). Using Visual Grading Characteristic for the evaluation of different fMRI data acquisition methods. Paper presented at ESMRMB, Valencia, Spain, 2008.
Open this publication in new window or tab >>Using Visual Grading Characteristic for the evaluation of different fMRI data acquisition methods
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2008 (English)Conference paper, Published paper (Other academic)
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-64161 (URN)
Conference
ESMRMB, Valencia, Spain, 2008
Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2014-10-02
Ragnehed, M., Engström, M. & Lundberg, P. (2007). Does diazepam influence the BOLD response?. Paper presented at ISMRM, Berlin, Germany, 2007.
Open this publication in new window or tab >>Does diazepam influence the BOLD response?
2007 (English)Conference paper, Published paper (Other academic)
National Category
Social Sciences
Identifiers
urn:nbn:se:liu:diva-64171 (URN)
Conference
ISMRM, Berlin, Germany, 2007
Available from: 2011-01-13 Created: 2011-01-13 Last updated: 2014-10-02
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