ABSTRACT
Levetiracetam (LEV) and topiramate (TPM) are considered highly effective novel antiepileptic drugs (AEDs) in the treatment of focal epilepsies. To explore potential side effects, this study investigated their influence on cognitive functions comparatively by means of a standardized neuropsychological test battery assessing several cognitive domains. In this observational study, cognitive changes were explored in 30 consecutively recruited patients with focal epilepsy treated with LEV and in 21 patients treated with TPM, comparing functions assessed prior to gradual initiation and after reaching steady state of the individual target dosage. Before titration, patient groups did not differ significantly with respect to cognitive performance. Whereas the LEV group manifested no change in cognitive performance after AED titration, the TPM group worsened in the cognitive domains of cognitive speed and verbal fluency, as well as short-term memory. These findings suggest that TPM, unlike LEV, may impair frontal lobe functions. The lack of cognitive side effects related to LEV treatment may be relevant for treatment decisions.
Subject(s)
Anticonvulsants/pharmacology , Cognition/drug effects , Epilepsy/physiopathology , Fructose/analogs & derivatives , Piracetam/analogs & derivatives , Adult , Case-Control Studies , Electroencephalography/methods , Epilepsy/drug therapy , Female , Fructose/pharmacology , Humans , Intelligence/drug effects , Levetiracetam , Male , Memory, Short-Term/drug effects , Middle Aged , Multivariate Analysis , Neuropsychological Tests , Piracetam/pharmacology , Topiramate , Visual Perception/drug effectsABSTRACT
BACKGROUND: How does the brain convert sounds and phonemes into comprehensible speech? In the present magnetoencephalographic study we examined the hypothesis that the coherence of electromagnetic oscillatory activity within and across brain areas indicates neurophysiological processes linked to speech comprehension. RESULTS: Amplitude-modulated (sinusoidal 41.5 Hz) auditory verbal and nonverbal stimuli served to drive steady-state oscillations in neural networks involved in speech comprehension. Stimuli were presented to 12 subjects in the following conditions (a) an incomprehensible string of words, (b) the same string of words after being introduced as a comprehensible sentence by proper articulation, and (c) nonverbal stimulations that included a 600-Hz tone, a scale, and a melody. Coherence, defined as correlated activation of magnetic steady state fields across brain areas and measured as simultaneous activation of current dipoles in source space (Minimum-Norm-Estimates), increased within left- temporal-posterior areas when the sound string was perceived as a comprehensible sentence. Intra-hemispheric coherence was larger within the left than the right hemisphere for the sentence (condition (b) relative to all other conditions), and tended to be larger within the right than the left hemisphere for nonverbal stimuli (condition (c), tone and melody relative to the other conditions), leading to a more pronounced hemispheric asymmetry for nonverbal than verbal material. CONCLUSIONS: We conclude that coherent neuronal network activity may index encoding of verbal information on the sentence level and can be used as a tool to investigate auditory speech comprehension.
Subject(s)
Brain/physiology , Comprehension/physiology , Magnetoencephalography/methods , Nerve Net/physiology , Speech Perception/physiology , Acoustic Stimulation/methods , Adult , Brain/anatomy & histology , Brain Mapping , Female , Humans , Language , Male , Nerve Net/anatomy & histologyABSTRACT
Drawings of objects were presented in series of 54 each to 14 German speaking subjects with the tasks to indicate by button presses a) whether the grammatical gender of an object name was masculine ("der") or feminine ("die") and b) whether the depicted object was man-made or nature-made. The magnetoencephalogram (MEG) was recorded with a whole-head neuromagnetometer and task-specific patterns of brain activity were determined in the source space (Minimum Norm Estimates, MNE). A left-temporal focus of activity 150-275 ms after stimulus onset in the gender decision compared to the semantic classification task was discussed as indicating the retrieval of syntactic information, while a more expanded left hemispheric activity in the gender relative to the semantic task 300-625 ms after stimulus onset was discussed as indicating phonological encoding. A predominance of activity in the semantic task was observed over right fronto-central region 150-225 ms after stimulus-onset, suggesting that semantic and syntactic processes are prominent in this stage of lexical selection.
