- Email: [email protected]
EEG-fMRI of sleep spindles and K-complexes at 3 Tesla
e72
Society Proceedings / Clinical Neurophysiology 118 (2007) e9–e116
A combination of electrophysiological and behavioural data as objective measure of the impairment in congenital prosopagnosia—A. Lueschow 1, A. Lueschow 1, J.E. Weber 1, T. Sander 2, C.C. Carbon 3, T. Grueter 4, M. Grueter 4, L. Trahms 2, G. Curio 1 (1 Charite´-Universita¨tsmedizin, Berlin, 2 Physikalisch-Technische Bundesanstalt, Berlin, 3 Psychologische Fakulta¨t, Wien, 4 Westfa¨lische Wilhelms-Universita¨t, Mu¨nster) Recently a form of prosopagnosia has attracted attention that is not accompanied by any discernible brain lesion. Because subjects complain a lifelong impairment and because a familial clustering has been reported this condition has been termed congenital prosopagnosia (cPA) although sensu stricto ‘‘congenital’’ requires the molecular establishment of a genetic basis. In the absence of such determination of this neuropsychological condition as an entity on its own it is necessary to aim at a delineation by neuroimaging and behavioural data. In 14 subjects with cPA and 19 normals (all screened by a specially developed questionnaire) evoked responses were measured by simultaneous EEG and MEG recording in a viewing task with a sequence of faces and houses. A double dissociation between methodology and stimulus category was revealed: (i) In the cPA group, only MEG, but not EEG, showed an M170 (a component that has been linked to structural encoding of faces and to intercategorical discrimination) that was significantly reduced over the right hemisphere (t = 2.49; p = 0.019) and delayed over the left hemisphere (t = 2.78; p = 0.01). This asymmetry between hemispheres is in line with findings which attribute different functional roles to right and left occipitotemporal cortex in face processing. (ii) The M170 for houses was not altered, suggesting that the deficit is restricted to a face processing system. Additional analysis with accuracy data from three basic tests (face-familiarity, face recognition, face imagery) revealed a significantly negative correlation (r = 0.48; p = 0.047) between hit rate and latency of M170 over the left hemisphere for subjects with cPA only. This suggests a link
between strength of impairment as measured behaviourally and MEG-correlates of face processing in cPA. In summary electrophysiological measures alone as well as their combination with behavioural measures offer an objective criterion to dissociate cPA from normal face processing. doi:10.1016/j.clinph.2006.11.166
EEG-fMRI of sleep spindles and K-complexes at 3 Tesla— T. Lund 1, T. Lund 1, M. Walker 3, H. Laufs 2 (1 Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark, 2 Klinik fu¨r Neurologie und Brain Imaging Centre, Johann Wolfgang Goethe-Universtita¨t, Frankfurt am Main, Germany, 3 Institute of Neurology, UC London, UK) Background: In 1935, Loomis first described ‘‘spindles’’ on the electroencephalogram (EEG) during human sleep. They are thought to be related to reticular thalamic hyperpolarization and are often associated with K-complexes (KC) which may result from synchronized cortical networks imposing excitatory and inhibitory actions on thalamic and cortical neurons (Amzica, 1997; Steriade, 2005). Methods: A healthy, eyes-closed resting volunteer was studied with echo planar imaging at 3 T (Trio, Siemens, Erlangen, Germany) and simultaneous polysomnography recordings following DGKN guidelines including EEG, EOG, EMG (BrainAmp MRplus/ExG, Brain Products, Munich, Germany), respirationbelt, pulse-oximetry (Siemens)). After artifact subtraction, a sleep stage II (Rechtschaffen, 1968) EEG segment was identified to analyse blood oxygenation level-dependent (BOLD) signal changes in response to spindles and KC. In a general linear model (GLM), including regressors for realignment, respiration and cardiac cycle as effects of no interest (Glover, 2000), visually coded spindles and KC were modelled as
Fig. 1. EEG sample of sleep stage II (Rechtschaffen and Kales, 1968). Bipolar montage of selected channels during functional magnetic resonance imaging at 3 T after artifact subtraction. Onset of volume acquisitions are indicated by ‘‘Scan Start’’ markers (TR = 2). Note association of K-complexes (KC) with sleep spindles but additional separate occurrences of spindles. Positive occipital sharp transients of sleep (POSTS) can be also seen.
Society Proceedings / Clinical Neurophysiology 118 (2007) e9–e116
e73
Fig. 2. Overlay of statistical parametric maps (SPM, P < 0.001 for visualization) onto the subject’s individual but normalized anatomy. (A and B) T1 surface rendering, lateral views, SPM{F} for spindle (red) and K complexes (KC, green). Signal change was positive for spindles and negative for KC. color intensity is a function of depth overlying colors mix. (C and D) Normalized mean EPI, mesial sagittal plane (C) and coronal plane through thalamus (D), SPM{T} for KC, negative haemodynaic response (blue) and for spindles, positive response (red). Cluster maxima in primary cortices survived correction for multiple comparisons at P < 0.05 (family wise error).
events of interest by convolution with the canonical hemodynamic response function, its time and dispersion derivatives (SPM2, http://www.fil.ion.ucl.ac.uk/spm). Findings: After 4.5 min the subject reached 14 min of stage II sleep, with 115 spindles and 50 associated KC (Fig. 1). BOLD signal changes to spindles and KC were co-localized and generally bilateral, opposite in direction, positive for spindles and negative for KC and detectable in the thalamus, frontal and central (sensorimotor), temporal (auditory) and, to a lesser degree, occipital (visual) cortices (Fig. 2). Conclusion: Our findings suggest that sleep spindles and KC reflect synchronized activity of primary cortices coordinated via the thalamus. KC may reflect inhibition of sensorimotor and auditory cortices activated by noise and vibrations from the MRI scanner occurring during sleep spindles with the thalamus as a gating relay station. Given the high correlation of KC with spindles, the direction of the signal changes attributed to spindles and KC by the GLM may not be accurate but rather reflect the occurrence of a biphasic signal change in response to these EEG sleep phenomena. doi:10.1016/j.clinph.2006.11.167
A stepping mechanism in tilt table mobilization can prevent syncopes in patients with traumatic brain injury: A case report—M. Luther, C. Krewer, F. Mu¨ller, E. Koenig (Neurologische Klinik Bad Aibling) Background: A major problem in the mobilization of patients in persistent vegetative or minimally conscious state is the poten-
tial circulatory collapse because of orthostatic hypotension that might occur while changing from supine to vertical position after prolonged confinement to bed. Therefore, a tilt table with integrated stepping device (Erigo, Hocoma AG, Zurich) was developed, which allows passive stepping movements in order to reduce venous blood pooling. Case description: The patient, a 45-year-old male, had suffered a severe traumatic brain injury (initial GCS 7) in form of a severe diffuse axonal injury and smaller contusional intracerebral bleedings bifrontal as well as a complicated injury to the left knee in a motorcycle accident. Two months after the trauma the patient still was minimally conscious (Koma Remission Scale 20/24). He showed spontaneous movements of both legs and arms, and had a tracheal cannula because of dysphagia. During the first attempt of a mobilization into assisted standing in physical therapy he had a syncope with loss of consciousness after 2 min. He was then trained once on the conventional tilt table and once on the Erigo. Verticalization up to 50° was tolerated well on both devices, but the patient showed tachypnea and pallor as symptoms of presyncope on the tilt table after 1 min at 70° so that the training had to be stopped early. Systolic blood pressure revealed a decrease of 13 mm Hg, heart rate decreased by 12 bpm. On the next day, the patient was mobilized on the Erigo, where an inclination of 70° was kept for 16 min without detecting any signs of presyncope in the patient. Conclusion: Erigo is an efficient way of early mobilization for unconscious or minimally conscious patients with hypostatic dysfunction. On the tilt table no leg movement is possible because of the fixed position. In contrast, by performing the verticalization on the Erigo the muscle pump is activated to augment venous return. Long term effects on the circulatory system as well as
Society Proceedings / Clinical Neurophysiology 118 (2007) e9–e116
A combination of electrophysiological and behavioural data as objective measure of the impairment in congenital prosopagnosia—A. Lueschow 1, A. Lueschow 1, J.E. Weber 1, T. Sander 2, C.C. Carbon 3, T. Grueter 4, M. Grueter 4, L. Trahms 2, G. Curio 1 (1 Charite´-Universita¨tsmedizin, Berlin, 2 Physikalisch-Technische Bundesanstalt, Berlin, 3 Psychologische Fakulta¨t, Wien, 4 Westfa¨lische Wilhelms-Universita¨t, Mu¨nster) Recently a form of prosopagnosia has attracted attention that is not accompanied by any discernible brain lesion. Because subjects complain a lifelong impairment and because a familial clustering has been reported this condition has been termed congenital prosopagnosia (cPA) although sensu stricto ‘‘congenital’’ requires the molecular establishment of a genetic basis. In the absence of such determination of this neuropsychological condition as an entity on its own it is necessary to aim at a delineation by neuroimaging and behavioural data. In 14 subjects with cPA and 19 normals (all screened by a specially developed questionnaire) evoked responses were measured by simultaneous EEG and MEG recording in a viewing task with a sequence of faces and houses. A double dissociation between methodology and stimulus category was revealed: (i) In the cPA group, only MEG, but not EEG, showed an M170 (a component that has been linked to structural encoding of faces and to intercategorical discrimination) that was significantly reduced over the right hemisphere (t = 2.49; p = 0.019) and delayed over the left hemisphere (t = 2.78; p = 0.01). This asymmetry between hemispheres is in line with findings which attribute different functional roles to right and left occipitotemporal cortex in face processing. (ii) The M170 for houses was not altered, suggesting that the deficit is restricted to a face processing system. Additional analysis with accuracy data from three basic tests (face-familiarity, face recognition, face imagery) revealed a significantly negative correlation (r = 0.48; p = 0.047) between hit rate and latency of M170 over the left hemisphere for subjects with cPA only. This suggests a link
between strength of impairment as measured behaviourally and MEG-correlates of face processing in cPA. In summary electrophysiological measures alone as well as their combination with behavioural measures offer an objective criterion to dissociate cPA from normal face processing. doi:10.1016/j.clinph.2006.11.166
EEG-fMRI of sleep spindles and K-complexes at 3 Tesla— T. Lund 1, T. Lund 1, M. Walker 3, H. Laufs 2 (1 Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark, 2 Klinik fu¨r Neurologie und Brain Imaging Centre, Johann Wolfgang Goethe-Universtita¨t, Frankfurt am Main, Germany, 3 Institute of Neurology, UC London, UK) Background: In 1935, Loomis first described ‘‘spindles’’ on the electroencephalogram (EEG) during human sleep. They are thought to be related to reticular thalamic hyperpolarization and are often associated with K-complexes (KC) which may result from synchronized cortical networks imposing excitatory and inhibitory actions on thalamic and cortical neurons (Amzica, 1997; Steriade, 2005). Methods: A healthy, eyes-closed resting volunteer was studied with echo planar imaging at 3 T (Trio, Siemens, Erlangen, Germany) and simultaneous polysomnography recordings following DGKN guidelines including EEG, EOG, EMG (BrainAmp MRplus/ExG, Brain Products, Munich, Germany), respirationbelt, pulse-oximetry (Siemens)). After artifact subtraction, a sleep stage II (Rechtschaffen, 1968) EEG segment was identified to analyse blood oxygenation level-dependent (BOLD) signal changes in response to spindles and KC. In a general linear model (GLM), including regressors for realignment, respiration and cardiac cycle as effects of no interest (Glover, 2000), visually coded spindles and KC were modelled as
Fig. 1. EEG sample of sleep stage II (Rechtschaffen and Kales, 1968). Bipolar montage of selected channels during functional magnetic resonance imaging at 3 T after artifact subtraction. Onset of volume acquisitions are indicated by ‘‘Scan Start’’ markers (TR = 2). Note association of K-complexes (KC) with sleep spindles but additional separate occurrences of spindles. Positive occipital sharp transients of sleep (POSTS) can be also seen.
Society Proceedings / Clinical Neurophysiology 118 (2007) e9–e116
e73
Fig. 2. Overlay of statistical parametric maps (SPM, P < 0.001 for visualization) onto the subject’s individual but normalized anatomy. (A and B) T1 surface rendering, lateral views, SPM{F} for spindle (red) and K complexes (KC, green). Signal change was positive for spindles and negative for KC. color intensity is a function of depth overlying colors mix. (C and D) Normalized mean EPI, mesial sagittal plane (C) and coronal plane through thalamus (D), SPM{T} for KC, negative haemodynaic response (blue) and for spindles, positive response (red). Cluster maxima in primary cortices survived correction for multiple comparisons at P < 0.05 (family wise error).
events of interest by convolution with the canonical hemodynamic response function, its time and dispersion derivatives (SPM2, http://www.fil.ion.ucl.ac.uk/spm). Findings: After 4.5 min the subject reached 14 min of stage II sleep, with 115 spindles and 50 associated KC (Fig. 1). BOLD signal changes to spindles and KC were co-localized and generally bilateral, opposite in direction, positive for spindles and negative for KC and detectable in the thalamus, frontal and central (sensorimotor), temporal (auditory) and, to a lesser degree, occipital (visual) cortices (Fig. 2). Conclusion: Our findings suggest that sleep spindles and KC reflect synchronized activity of primary cortices coordinated via the thalamus. KC may reflect inhibition of sensorimotor and auditory cortices activated by noise and vibrations from the MRI scanner occurring during sleep spindles with the thalamus as a gating relay station. Given the high correlation of KC with spindles, the direction of the signal changes attributed to spindles and KC by the GLM may not be accurate but rather reflect the occurrence of a biphasic signal change in response to these EEG sleep phenomena. doi:10.1016/j.clinph.2006.11.167
A stepping mechanism in tilt table mobilization can prevent syncopes in patients with traumatic brain injury: A case report—M. Luther, C. Krewer, F. Mu¨ller, E. Koenig (Neurologische Klinik Bad Aibling) Background: A major problem in the mobilization of patients in persistent vegetative or minimally conscious state is the poten-
tial circulatory collapse because of orthostatic hypotension that might occur while changing from supine to vertical position after prolonged confinement to bed. Therefore, a tilt table with integrated stepping device (Erigo, Hocoma AG, Zurich) was developed, which allows passive stepping movements in order to reduce venous blood pooling. Case description: The patient, a 45-year-old male, had suffered a severe traumatic brain injury (initial GCS 7) in form of a severe diffuse axonal injury and smaller contusional intracerebral bleedings bifrontal as well as a complicated injury to the left knee in a motorcycle accident. Two months after the trauma the patient still was minimally conscious (Koma Remission Scale 20/24). He showed spontaneous movements of both legs and arms, and had a tracheal cannula because of dysphagia. During the first attempt of a mobilization into assisted standing in physical therapy he had a syncope with loss of consciousness after 2 min. He was then trained once on the conventional tilt table and once on the Erigo. Verticalization up to 50° was tolerated well on both devices, but the patient showed tachypnea and pallor as symptoms of presyncope on the tilt table after 1 min at 70° so that the training had to be stopped early. Systolic blood pressure revealed a decrease of 13 mm Hg, heart rate decreased by 12 bpm. On the next day, the patient was mobilized on the Erigo, where an inclination of 70° was kept for 16 min without detecting any signs of presyncope in the patient. Conclusion: Erigo is an efficient way of early mobilization for unconscious or minimally conscious patients with hypostatic dysfunction. On the tilt table no leg movement is possible because of the fixed position. In contrast, by performing the verticalization on the Erigo the muscle pump is activated to augment venous return. Long term effects on the circulatory system as well as