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PF5.4 Brain Plasticity during Motor Learning
2009 Asian and Oceanian Congress of Clinical Neurophysiology
Session PF5. Functional Neuroimaging and Neural Processing PF5.1 Effects of Neonatal Dexamethasone Treatment on Brain Synaptic Plasticity and Function Amer Al-Ansari1,2 *, Patrick Kamhuis2 , Ali Mohmmed Al-Satir1 1 Arabian Gulf University/Bahrain, College of Medicine, Bahrain, 2 College of Medicine, Rudolf Magnus Institute of Neurosciences, Utrecht University, Netherlands E-mail address: [email protected] Background: Synthetic glucocorticoids (GC) like dexamethasone (Dex) are widely used for treatment and prevention of chronic lung disease in premature human infants. In rats, GC treatment and stress result in impaired performance in spatial learning tasks. Since the hippocampus has a crucial role in spatial learning and memory, this suggests that neonatal GC may influence hippocampal development and function. The aim of this study was to evaluate the effect of neonatal Dex administration on the brain development and function. Methods: New born rats were i.p injected with Dex on neonatal day 1, 2, and 3 (0.5, 0.3, and 0.1 mg/g body wt). Controls were injected with equal volumes of saline (Sal). At age of 3 4 months, spatial learning was tested in the Morris water maze (210 cm diameter) with a hidden or a visible platform. The animals were then decapitated and hippocampal slices were prepared. Synaptic long term potentiation (LTP) and depression (LTD) were induced in these slices. Responses were recorded by glass microelectrodes in CA1 field of the hippocampus. Results: The performance of Dex rats in the water maze showed increased escape latency compared with Sal rats (P < 0.05). Neurophysiologic experimental data showed that low-frequency stimulation depressed significantly the synapses more in the Dex (slope reduced to 66.5±3.7% of the baseline) than in the Sal group (94.1±4.3%). High-frequency stimulation, on the other hand induced more LTP in the Sal (227.2±14.3%) than in the Dex group (112.5±4.7%). Conclusions: Neonatal Dex affects significantly the hippocampus synaptic plasticity. The water Maze testing showed that the Dex group of animals was performing less than the Sal group. PF5.2 Effects of Viagra (Sildenafil) as a Phosphodiesterase Inhibitor on Electrophysiology of Hippocampus in the Old Male Rat Siamak Shahidi *, Alireza Komaki Dept. of Physiology, Hamadan University of Medical Sciences, Iran E-mail address: [email protected] Background: Long-term potentiation (LTP) is a long-term increase in synaptic transmission induced by high frequency stimulation (HFS). It is widely considered as a cellular model for learning and memory. Hippocampal nitric oxide/cGMP signaling pathway plays crucial role in the learning and memory processing. Phsphodiesterase interact with this signaling pathway. In this study, we examined the effects of acute administration of sildenafil (Viagra), as a phosphodiesterase inhibitor, on the evoked potentials and LTP induction in the hippocampal dentate gyrus of rats. Methods: Adult old male Wistar rats were used. They were anesthetized and placed in a stereotaxic device. Then, recording and stimulating electrodes were positioned in the dentate gyrus and perforant pathway, respectively. After baseline recording, single i.p injection of saline or sildenafil (2 or 10 mg/kg) was done. LTP was induced using HFS. The population spike (PS) amplitude and the slope of excitatory post synaptic potentials (EPSP) were compared between these three groups. In addition, paired pulses stimuli were applied to determine recurrent inhibition as a role of inhibitory interneurons. Results: The results showed that the doses of 2 and 10 mg/kg of sildenafil significantly increased the EPSP and PS from basal level. Also, 5, 30, 60 and 120 minutes following the tetanic stimulation EPSP and PS were significantly increase in compare with saline treated group by 2 and 10 mg/kg of sildenafil dose dependently. Sildenafil had no effects on the recurrent inhibition. Conclusions: These results indicate that acute administration of sildenafil dose dependently improved induction of long term potentiation via direct effects on the perforant path-dentate gyrus synapse (but not by
S31 disinhibition) in the hippocampus of normal aged rats. Sildenafil may play a role as a memory enhancer or prevents the age related memory impairment. PF5.3 Effects of Emotional Stimulation on Cortico-Spinal Coherence during Isometric Contraction in Humans Satria Fextha *, Nobuki Murayama, Tomohiko Igasaki, Yuki Hayashida Dept. of Graduate School of Science and Technology, Kumamoto University, Japan E-mail address: [email protected] Background: To study the effect of emotional stimulation on motor cortex-muscle synchronization, coherence between electroencephalography (EEG) and electromyography (EMG) was measured in normal subjects under control and task (ignore and assess) conditions. Methods: Eight normal healthy male subjects aged 19 35 years old participated in two (control and task) experiments. Subjects were instructed to fix their eyes on the center of the screen which is placed 1 m in front of the subject and perform the weak isometric contraction of right hand of the first dorsal interosseous (FDI) muscle. During control conditions, a black image was displayed on the screen for 1 minute. Control conditions were performed before and after each task condition. During the task condition, one unpleasant, high arousal, mono-color image from the International Affective Picture System was displayed on the screen for 1 minute. In this condition, subjects were asked to fix their eyes on the center of the screen and ignore the image (Ignore) for the first experiment, then assess the image (Assess) in the second experiment. Results: Significant magnitude of coherence was found at C3 site. The frequency range of the significant coherence was in the beta frequency band. In ignore condition, the magnitude in the peak coherence at C3 site increases significantly, while that of the peak coherence at C3 site decreases significantly in the assess condition. Conclusions: In ignore condition, the magnitude in the peak coherence at C3 site increases, while that of the peak coherence at C3 site decreases in the assess condition. PF5.4 Brain Plasticity during Motor Learning Ken Nagata *, David Wright Dept. of Neurology, Research Institute for Brain and Blood Vessels, Japan E-mail address: [email protected] Background: Previous neuroimaging studies have reported changes in the primary motor cortex activation with motor learning, and have suggested that this indicates a level of neural plasticity in the primary motor cortex, which underlies motor learning. The present study was carried out to elucidate the neural correlates of motor learning and motor memory consolidation. Methods: Thirty healthy right-handed male volunteers participated in this activation study with positron emission tomography (PET). A star shape was presented to the subject on a computer monitor positioned above the PET gantry. During each trial the subject used a Felix pointing device to guide a small red dot around the star shape in an anti-clockwise direction. Subjects were instructed to perform the trace as quickly and accurately as possible using their left hand. After the tenth trial the Felix was reconfigured so that hand movements were ‘mirrored’ on the computer screen. The subject then performed the tasks further 15 times. Over the course of the learning, a series of 10 PET scans was conducted, and the behavioural data was also collected. Results: During the early stages of motor learning the right premotor, right pre-supplementary motor, right prefrontal, bilateral inferior parietal, right temporal lobe, anterior cingulate cortices and left cerebellar lobe were significantly activated. During the late stages, the primary motor, supplementary motor, bilateral occipital cortex including the lingual gyrus, cuneus, precuneus, and posterior cingulate, and left cerebellar cortices were significantly activated. Conclusions: This data suggests that during the early stages of learning, motor control is more externally mediated via neural networks, which are highly influenced by visuospatial information, error feed back, working memory and attention. While following practice, skilled motor control is more internally mediated via internal visual task representations.
Session PF5. Functional Neuroimaging and Neural Processing PF5.1 Effects of Neonatal Dexamethasone Treatment on Brain Synaptic Plasticity and Function Amer Al-Ansari1,2 *, Patrick Kamhuis2 , Ali Mohmmed Al-Satir1 1 Arabian Gulf University/Bahrain, College of Medicine, Bahrain, 2 College of Medicine, Rudolf Magnus Institute of Neurosciences, Utrecht University, Netherlands E-mail address: [email protected] Background: Synthetic glucocorticoids (GC) like dexamethasone (Dex) are widely used for treatment and prevention of chronic lung disease in premature human infants. In rats, GC treatment and stress result in impaired performance in spatial learning tasks. Since the hippocampus has a crucial role in spatial learning and memory, this suggests that neonatal GC may influence hippocampal development and function. The aim of this study was to evaluate the effect of neonatal Dex administration on the brain development and function. Methods: New born rats were i.p injected with Dex on neonatal day 1, 2, and 3 (0.5, 0.3, and 0.1 mg/g body wt). Controls were injected with equal volumes of saline (Sal). At age of 3 4 months, spatial learning was tested in the Morris water maze (210 cm diameter) with a hidden or a visible platform. The animals were then decapitated and hippocampal slices were prepared. Synaptic long term potentiation (LTP) and depression (LTD) were induced in these slices. Responses were recorded by glass microelectrodes in CA1 field of the hippocampus. Results: The performance of Dex rats in the water maze showed increased escape latency compared with Sal rats (P < 0.05). Neurophysiologic experimental data showed that low-frequency stimulation depressed significantly the synapses more in the Dex (slope reduced to 66.5±3.7% of the baseline) than in the Sal group (94.1±4.3%). High-frequency stimulation, on the other hand induced more LTP in the Sal (227.2±14.3%) than in the Dex group (112.5±4.7%). Conclusions: Neonatal Dex affects significantly the hippocampus synaptic plasticity. The water Maze testing showed that the Dex group of animals was performing less than the Sal group. PF5.2 Effects of Viagra (Sildenafil) as a Phosphodiesterase Inhibitor on Electrophysiology of Hippocampus in the Old Male Rat Siamak Shahidi *, Alireza Komaki Dept. of Physiology, Hamadan University of Medical Sciences, Iran E-mail address: [email protected] Background: Long-term potentiation (LTP) is a long-term increase in synaptic transmission induced by high frequency stimulation (HFS). It is widely considered as a cellular model for learning and memory. Hippocampal nitric oxide/cGMP signaling pathway plays crucial role in the learning and memory processing. Phsphodiesterase interact with this signaling pathway. In this study, we examined the effects of acute administration of sildenafil (Viagra), as a phosphodiesterase inhibitor, on the evoked potentials and LTP induction in the hippocampal dentate gyrus of rats. Methods: Adult old male Wistar rats were used. They were anesthetized and placed in a stereotaxic device. Then, recording and stimulating electrodes were positioned in the dentate gyrus and perforant pathway, respectively. After baseline recording, single i.p injection of saline or sildenafil (2 or 10 mg/kg) was done. LTP was induced using HFS. The population spike (PS) amplitude and the slope of excitatory post synaptic potentials (EPSP) were compared between these three groups. In addition, paired pulses stimuli were applied to determine recurrent inhibition as a role of inhibitory interneurons. Results: The results showed that the doses of 2 and 10 mg/kg of sildenafil significantly increased the EPSP and PS from basal level. Also, 5, 30, 60 and 120 minutes following the tetanic stimulation EPSP and PS were significantly increase in compare with saline treated group by 2 and 10 mg/kg of sildenafil dose dependently. Sildenafil had no effects on the recurrent inhibition. Conclusions: These results indicate that acute administration of sildenafil dose dependently improved induction of long term potentiation via direct effects on the perforant path-dentate gyrus synapse (but not by
S31 disinhibition) in the hippocampus of normal aged rats. Sildenafil may play a role as a memory enhancer or prevents the age related memory impairment. PF5.3 Effects of Emotional Stimulation on Cortico-Spinal Coherence during Isometric Contraction in Humans Satria Fextha *, Nobuki Murayama, Tomohiko Igasaki, Yuki Hayashida Dept. of Graduate School of Science and Technology, Kumamoto University, Japan E-mail address: [email protected] Background: To study the effect of emotional stimulation on motor cortex-muscle synchronization, coherence between electroencephalography (EEG) and electromyography (EMG) was measured in normal subjects under control and task (ignore and assess) conditions. Methods: Eight normal healthy male subjects aged 19 35 years old participated in two (control and task) experiments. Subjects were instructed to fix their eyes on the center of the screen which is placed 1 m in front of the subject and perform the weak isometric contraction of right hand of the first dorsal interosseous (FDI) muscle. During control conditions, a black image was displayed on the screen for 1 minute. Control conditions were performed before and after each task condition. During the task condition, one unpleasant, high arousal, mono-color image from the International Affective Picture System was displayed on the screen for 1 minute. In this condition, subjects were asked to fix their eyes on the center of the screen and ignore the image (Ignore) for the first experiment, then assess the image (Assess) in the second experiment. Results: Significant magnitude of coherence was found at C3 site. The frequency range of the significant coherence was in the beta frequency band. In ignore condition, the magnitude in the peak coherence at C3 site increases significantly, while that of the peak coherence at C3 site decreases significantly in the assess condition. Conclusions: In ignore condition, the magnitude in the peak coherence at C3 site increases, while that of the peak coherence at C3 site decreases in the assess condition. PF5.4 Brain Plasticity during Motor Learning Ken Nagata *, David Wright Dept. of Neurology, Research Institute for Brain and Blood Vessels, Japan E-mail address: [email protected] Background: Previous neuroimaging studies have reported changes in the primary motor cortex activation with motor learning, and have suggested that this indicates a level of neural plasticity in the primary motor cortex, which underlies motor learning. The present study was carried out to elucidate the neural correlates of motor learning and motor memory consolidation. Methods: Thirty healthy right-handed male volunteers participated in this activation study with positron emission tomography (PET). A star shape was presented to the subject on a computer monitor positioned above the PET gantry. During each trial the subject used a Felix pointing device to guide a small red dot around the star shape in an anti-clockwise direction. Subjects were instructed to perform the trace as quickly and accurately as possible using their left hand. After the tenth trial the Felix was reconfigured so that hand movements were ‘mirrored’ on the computer screen. The subject then performed the tasks further 15 times. Over the course of the learning, a series of 10 PET scans was conducted, and the behavioural data was also collected. Results: During the early stages of motor learning the right premotor, right pre-supplementary motor, right prefrontal, bilateral inferior parietal, right temporal lobe, anterior cingulate cortices and left cerebellar lobe were significantly activated. During the late stages, the primary motor, supplementary motor, bilateral occipital cortex including the lingual gyrus, cuneus, precuneus, and posterior cingulate, and left cerebellar cortices were significantly activated. Conclusions: This data suggests that during the early stages of learning, motor control is more externally mediated via neural networks, which are highly influenced by visuospatial information, error feed back, working memory and attention. While following practice, skilled motor control is more internally mediated via internal visual task representations.