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156. NMDA antagonist reduce the striatal hyperactivity of parkinsonian rats
Society Proceedings / Clinical Neurophysiology 119 (2008) e99–e164
Bayesian model averaging (BMA) was introduced under the evidence approximation (eBMA) as a tool for addressing the model uncertainty problem arising when dealing with different modeldependent EEG/MEG inverse solutions. In the present work a Variational Bayes formulation of BMA (vBMA) is introduced. Additionally, the eBMA approach is extended to include informative model prior probabilities (iMPPs) and to consider anatomical models defined on the cortical mantle. The proposed BMA inference was carried out by using a Markov Chain Monte Carlo method. The iMPPs were defined by using experiment-related fMRI data and the cortical BMA was obtained by restricting the sources to lie on the gray/white matter interface. Both vBMA and eBMA showed similar performance regarding detection and localization accuracy. Nevertheless, vBMA showed a relative independence on the source depth. Overall, the two approaches were robust to wrongly specified iMPPs, while improved the quality of the solutions and decreased the computational cost for correctly specified iMPPs. These results validate the use of the variational approach for complex models when the evidence approach is not viable. Introducing informative prior probabilities improved the performance of BMA regarding accuracy and computational cost. The cortical BMA offers a more computationally feasible alternative.
e137
We evaluate the relation between the volumes of 54 symmetrical anatomical regions of brain hemispheres in the Cuban MRI database. This would allow establishing normative data related to the asymmetries between homologous brain volumes, which could be used as a comparison pattern for subjects in evaluation for different suspected pathological conditions. Anatomical mris of 237 normal subjects were obtained. Automatic classification of 54 structures in each hemisphere was obtained using IBASPM. Student t-tests to compare the volume of homologous brain regions were used. Multivariate comparison was performed using the Hotelling‘s T2 test. Brain volumes between Cuban and Montreal Neurological Institute databases were compared. Structures with the highest correlation values were used to define a brain network. A high level of significant differences between left and right volumes in normal subjects was found. Normative Cuban volume values were similar to those reported in the Montreal Neurological Institute database. There is a relationship between handiness and correlation values between different brain structures. Also, sex differences of asymmetries between the two hemispheres were found. doi:10.1016/j.clinph.2008.04.171
doi:10.1016/j.clinph.2008.04.169
154. Penalized regression methods in the source analysis of face recognition—M. Vega Herna´ndez, E. Martı´nez Montes, J.P. Hidalgo Gato, J.M. Sa´nchez Bornot, P.A. Valde´s Sosa (Cuba) Formulation of the EEG inverse problem in terms of a multiple penalized least squares (MPLS) model offers the possibility of estimating several new inverse solutions with unexplored properties. This methodology allows the use of different constraints, such as smoothness (LORETA), sparseness (Lasso Fusion) and the combination of both constraints (enet). Here, we study the applicability of this approach to the source analysis of face recognition data. The estimation is carried out using the Minorization–Maximixation algorithm. Hotelling’s T2 statistics were computed across 10 subjects for conditions of correct and incorrect face detection and for the difference between them. Significant activations for the correct and incorrect detection of faces were found in the inferior and superior temporal gyrus right, in the middle frontal gyrus (right and left) and in the middle occipital gyrus right, although with different degree of activation. Significant differential sources were located mainly in the inferior temporal and middle occipital gyri right. LORETA, Lasso Fusion and enet found sources in agreement with previous studies with fMRI. Enet offered solutions with intermediate levels of blurring from LORETA (too smooth) to Lasso Fusion (too sparse). However, this method depends on the selection of optimal regularization parameters, which should be carefully estimated.
156. NMDA antagonist reduce the striatal hyperactivity of parkinsonian rats—P.E. Pomata, M. Belluscio, L.A. Riquelme, M.G. Murer (Argentina) The aim of the present work is to assess the effect of NMDA antagonist on the firing frequency of striatal neurons in an animal model of Parkinson’s disease. We recorded striatal activity in uretane-anaesthesiated rats that were either dopamine-depleted with 6-OHDA or sham lesioned. Extracellular multi-unit activity was acquired using 16 channel silicon probes simultaneously with the motor cortex local field potential. Drugs were infused through reverse microdialysis close to the recording probe. Striatal multiunit activity was markedly modulated by cortical slow waves and cortical activation in both, dopamine-depleted and control rats. Accordingly to preceding data, the basal rate of discharge was elevated in depleted rats (223.4 ± 42.8 vs. 101 ± 15.3 spikes/min). The infusion of intra-striatal competitive NMDA antagonist (AP-5 100lM) reduced reversibly the spike frequency of dopamine-depleted (54%) and sham rats (43.9%). Comparable results were observed with others NMDA antagonists. The analysis of single-unit activity revealed that AP-5 reduced specially the activity of phasic spiking neurons (77.8%) and had a small effect on those tonically active neurons (18.5%).These results indicate that NMDA antagonist were able to reduce the firing frequency of the striatal neurons in both depleted and control rats. The effect was largely observed in neurons with phasic pattern corresponding to MSN, suggesting the contribution of NMDA receptors to their depolarized states. doi:10.1016/j.clinph.2008.04.172
doi:10.1016/j.clinph.2008.04.170
155. Brain volumes asymmetries between homologous ´ lvarez, A. Calzado, A. regions of both hemispheres—A. A ´ Lage, Y. Aleman, L. Melie, P.A. Valde´s Sosa (Cuba)
157. Spatio-temporal correlations in fMRI time series: The innovation approach—J. Bosch Bayard, J. Riera Dı´az, R. Biscay Lirio, K. Wong, O. Yamashita, P.A. Valde´s Sosa, T. Ozaki (Cuba)
Bayesian model averaging (BMA) was introduced under the evidence approximation (eBMA) as a tool for addressing the model uncertainty problem arising when dealing with different modeldependent EEG/MEG inverse solutions. In the present work a Variational Bayes formulation of BMA (vBMA) is introduced. Additionally, the eBMA approach is extended to include informative model prior probabilities (iMPPs) and to consider anatomical models defined on the cortical mantle. The proposed BMA inference was carried out by using a Markov Chain Monte Carlo method. The iMPPs were defined by using experiment-related fMRI data and the cortical BMA was obtained by restricting the sources to lie on the gray/white matter interface. Both vBMA and eBMA showed similar performance regarding detection and localization accuracy. Nevertheless, vBMA showed a relative independence on the source depth. Overall, the two approaches were robust to wrongly specified iMPPs, while improved the quality of the solutions and decreased the computational cost for correctly specified iMPPs. These results validate the use of the variational approach for complex models when the evidence approach is not viable. Introducing informative prior probabilities improved the performance of BMA regarding accuracy and computational cost. The cortical BMA offers a more computationally feasible alternative.
e137
We evaluate the relation between the volumes of 54 symmetrical anatomical regions of brain hemispheres in the Cuban MRI database. This would allow establishing normative data related to the asymmetries between homologous brain volumes, which could be used as a comparison pattern for subjects in evaluation for different suspected pathological conditions. Anatomical mris of 237 normal subjects were obtained. Automatic classification of 54 structures in each hemisphere was obtained using IBASPM. Student t-tests to compare the volume of homologous brain regions were used. Multivariate comparison was performed using the Hotelling‘s T2 test. Brain volumes between Cuban and Montreal Neurological Institute databases were compared. Structures with the highest correlation values were used to define a brain network. A high level of significant differences between left and right volumes in normal subjects was found. Normative Cuban volume values were similar to those reported in the Montreal Neurological Institute database. There is a relationship between handiness and correlation values between different brain structures. Also, sex differences of asymmetries between the two hemispheres were found. doi:10.1016/j.clinph.2008.04.171
doi:10.1016/j.clinph.2008.04.169
154. Penalized regression methods in the source analysis of face recognition—M. Vega Herna´ndez, E. Martı´nez Montes, J.P. Hidalgo Gato, J.M. Sa´nchez Bornot, P.A. Valde´s Sosa (Cuba) Formulation of the EEG inverse problem in terms of a multiple penalized least squares (MPLS) model offers the possibility of estimating several new inverse solutions with unexplored properties. This methodology allows the use of different constraints, such as smoothness (LORETA), sparseness (Lasso Fusion) and the combination of both constraints (enet). Here, we study the applicability of this approach to the source analysis of face recognition data. The estimation is carried out using the Minorization–Maximixation algorithm. Hotelling’s T2 statistics were computed across 10 subjects for conditions of correct and incorrect face detection and for the difference between them. Significant activations for the correct and incorrect detection of faces were found in the inferior and superior temporal gyrus right, in the middle frontal gyrus (right and left) and in the middle occipital gyrus right, although with different degree of activation. Significant differential sources were located mainly in the inferior temporal and middle occipital gyri right. LORETA, Lasso Fusion and enet found sources in agreement with previous studies with fMRI. Enet offered solutions with intermediate levels of blurring from LORETA (too smooth) to Lasso Fusion (too sparse). However, this method depends on the selection of optimal regularization parameters, which should be carefully estimated.
156. NMDA antagonist reduce the striatal hyperactivity of parkinsonian rats—P.E. Pomata, M. Belluscio, L.A. Riquelme, M.G. Murer (Argentina) The aim of the present work is to assess the effect of NMDA antagonist on the firing frequency of striatal neurons in an animal model of Parkinson’s disease. We recorded striatal activity in uretane-anaesthesiated rats that were either dopamine-depleted with 6-OHDA or sham lesioned. Extracellular multi-unit activity was acquired using 16 channel silicon probes simultaneously with the motor cortex local field potential. Drugs were infused through reverse microdialysis close to the recording probe. Striatal multiunit activity was markedly modulated by cortical slow waves and cortical activation in both, dopamine-depleted and control rats. Accordingly to preceding data, the basal rate of discharge was elevated in depleted rats (223.4 ± 42.8 vs. 101 ± 15.3 spikes/min). The infusion of intra-striatal competitive NMDA antagonist (AP-5 100lM) reduced reversibly the spike frequency of dopamine-depleted (54%) and sham rats (43.9%). Comparable results were observed with others NMDA antagonists. The analysis of single-unit activity revealed that AP-5 reduced specially the activity of phasic spiking neurons (77.8%) and had a small effect on those tonically active neurons (18.5%).These results indicate that NMDA antagonist were able to reduce the firing frequency of the striatal neurons in both depleted and control rats. The effect was largely observed in neurons with phasic pattern corresponding to MSN, suggesting the contribution of NMDA receptors to their depolarized states. doi:10.1016/j.clinph.2008.04.172
doi:10.1016/j.clinph.2008.04.170
155. Brain volumes asymmetries between homologous ´ lvarez, A. Calzado, A. regions of both hemispheres—A. A ´ Lage, Y. Aleman, L. Melie, P.A. Valde´s Sosa (Cuba)
157. Spatio-temporal correlations in fMRI time series: The innovation approach—J. Bosch Bayard, J. Riera Dı´az, R. Biscay Lirio, K. Wong, O. Yamashita, P.A. Valde´s Sosa, T. Ozaki (Cuba)