|M.Sc Student||Haiman Guy|
|Subject||Characterization of the Neural Responses to Emotionally|
Loaded Verbal Stimuli among Multiple Sclerosis
Patients with Pseudobulbar affect
|Department||Department of Medicine||Supervisors||Professor Ariel Miller|
|Professor Emeritus Hillel Pratt|
Pseudobulbar affect (PBA) is a condition characterized by uncontrollable episodes of emotional lability such as inappropriate laughter and/or crying, disproportionate and incongruous with the underlying emotion. PBA has been associated with lesions involving the descending corticobulbar pathways and various areas of the brain including the frontal and temporal lobes and cerebellum, yet a specific link between the location of the lesion and the emergence of PBA has not yet been established.
The research aim was to characterize the electrophysiological activity and cortical brain structures, of multiple sclerosis patients with PBA, involved in response to emotionally-loaded auditory verbal stimuli, using the LORETA (Low resolution Electromagnetic Tomography Analysis) procedure for estimating source current density distribution in a 3D Talairach space of the brain’s gray matter.
Thirty three subjects, divided into 3 groups: multiple sclerosis patients with PBA (MS+PBA); multiple sclerosis patients without PBA (MS); healthy subjects (NORM), participated in this study.
Event related potentials (ERP) were recorded from 21 electrodes in response to verbal emotionally-loaded and neutral stimuli. LORETA current density estimations were performed on each subject’s ERPs waveforms, separately for emotionally-loaded and neutral stimuli. LORETA comparisons of current density were made between and within groups in response to experimental conditions, using statistical non parametric mapping (SnPM) procedure.
Electrophysiological analysis, in response to neutral stimuli, revealed significant differences between MS and NORM in P200 amplitude, LPC latency and a significant difference between MS+PBA and NORM in P100 amplitude. In response to emotionally loaded stimuli, significant difference between MS and NORM in LPC latency and significant differences between MS+PBA and NORM in P100 amplitude, N400 amplitude & latency and LPC latency.
LORETA comparisons between groups yielded distinct and significantly different activation in primary and associative somatosensory brain regions in response to neutral stimuli and significantly different activation in pre motor and supplementary motor brain regions in response to emotionally-loaded stimuli.
LORETA comparisons within groups revealed significant differences. In MS+PBA group, early activation in cortical regions associated with limbic system followed by a prolonged activation in cortical pre motor and supplementary motor areas. In NORM and MS groups, only late activations were observed in cortical regions associated with limbic system. In addition, for both emotionally-loaded and neutral stimuli, current density activation was higher in MS+PBA relative to MS and NORM groups.
These findings indicate that pseudobulbar affect involves cortical structures related to somatosensory and emotional processing in addition to involvement of motor cortical areas.