Masanori Ishiguro

Effects of propofol on IPSCs in CA1 and dentate gyrus cells of rat hippocampus: Propofol effects on hippocampal cells’ IPSCs

Propofol (2, 6-diisopropylphenol) is one of the most popular intravenous anesthetic agents. In this study, we compared the effects of propofol on inhibitory postsynaptic currents (IPSCs) induced by single and paired electrical stimulations in CA1 pyramidal cells (CA1-PCs) and dentate gyrus granule cells (DG-GCs) in rat hippocampal slices using the whole cell patch-clamp technique. In the absence of propofol, the amplitude of evoked IPSC by single stimulation and decay time constants were stable in both CA1-PCs and DG-GCs for 30 min. Propofol (1 μM and 10 μM) increased both IPSC amplitude in CA1-PCs, but not in DG-GCs. Further, using a paired pulse stimulation protocol, the ratio of IPSC amplitudes (the second response: A2/the first response: A1) was increased by propofol in CA1, but not in DG-GCs. These results suggest that propofol selectively affects IPSCs in CA1-PCs, which is similar to previously reported actions of benzodiazepines.

Load effect on background rhythms during motor execution: A magnetoencephalographic study

We investigated the effect of load against self-paced movement on cortical involvement for motor execution. Ten right-handed healthy volunteers were requested to perform brisk extension of the right index finger at self-paced intervals exceeding 10s for three load conditions: 0g, 50g and 100g. Movement-related magnetic fields were recorded using an MEG system. The signals were band-pass-filtered through 18-23Hz and rectified before averaging with respect to EMG onset. We analyzed the time course and %change of peak amplitude with reference to the baseline amplitude in event-related desynchronization (ERD) or synchronization (ERS) in each hemisphere. Maximum response was observed around the left somatomotor area for all conditions. ERD did not show any significant difference before the movement onset among the three load conditions. For %change, ERS in the post-movement period was significantly larger for the 100g load condition than for the 0g load condition, and that was significantly greater over the left than over the right hemisphere. These findings indicate that the load has little effect on pre-movement desynchronization, whereas it affects the post-movement synchronization on background rhythms.

Modulation of alpha activity in the parieto-occipital area by distractors during a visuospatial working memory task: A magnetoencephalographic study

Oscillatory brain activity is known to play an essential role in information processing in working memory. Recent studies have indicated that alpha activity (8–13 Hz) in the parieto-occipital area is strongly modulated in working memory tasks. However, the function of alpha activity in working memory is open to several interpretations, such that alpha activity may be a direct neural correlate of information processing in working memory or may reflect disengagement from information processing in other brain areas. To examine the functional contribution of alpha activity to visuospatial working memory, we introduced visuospatial distractors during a delay period and examined neural activity from the whole brain using magnetoencephalography. The strength of event-related alpha activity was estimated using the temporal spectral evolution (TSE) method. The results were as follows: (1) an increase of alpha activity during the delay period as indicated by elevated TSE curves was observed in parieto-occipital sensors in both the working memory task and a control task that did not require working memory; and (2) an increase of alpha activity during the delay period was not observed when distractors were presented, although TSE curves were constructed only from correct trials. These results indicate that the increase of alpha activity is not directly related to information processing in working memory but rather reflects the disengagement of attention from the visuospatial input.

18. Motor-related areas are activated in inhibitory motor response to omission of somatosensory stimuli: An MEG study

The aim of this study was to develop a method for functional imaging of human nerve electrical activities in the lumbar spine from evoked neuromagnetic measurements. The source reconstruction of nerve electrical activities was carried out over a curved surface that contained the nerve fiber in the lumbar spine. This curved surface was determined by using subject’s lateral X-ray image. We proposed to apply the Unit-Gain Constraint Minimum Norm filter with a Recursively Update Gram matrix spatial filter to reconstruct source activities on this surface. Reconstructed source intensity reflected cauda equine travel. This line was determined by using reconstructed source imaging of the front direction. Reconstructed sources propagated from caudal to rostral along the lumbar spinal canal. During the time courses at five selected voxels along the nerve travel, each time course showed a clear peak and into latency indicated the instants when nerve activity arrived at five voxel locations. Our proposed imaging method can clearly visualize the dynamics and the temporal intensity changes of nerve electrical activities in the lumbar spine.

P33-2 Motor related 20Hz brain activity can be enhanced by weak somatosensory stimuli below motor threshold: An MEG study

the S condition. The L(M)-L(S) and R(M)-R(S) tasks caused a significant enhancement only in SIIi. The L(M)-R(S) task enhanced the amplitude only in SIIc. The laterality index showed that SII modulation with voluntary movement was more dominant in the hemisphere ipsilateral to movement but was not affected by the side of stimulation. Conclusions: These results provided the characteristics of activities in somatosensory cortices, a simple inhibition in SI but complicated changes in SII depending on the side of movement and stimulation, which may indicate the higher cognitive processing in SII.

P33-13 The load effect on background rhythms during motor execution: a magnetoencephalographic study

T. Toyoshima1,2,3, S. Yazawa3, S. Simohama2, T. Murahara3, S. Takeda4, M. Ishiguro3, H. Shiraishi5, T. Nagamine3 1The Department of Neurology, Sapporo Shirakaba-dai Hospital, Sapporo, Japan, 2The Department of Neurology, School of Medicine, Sapporo Medical University, Sapporo, Japan, 3The Department of Neurophysiology, School of Medicine, Sapporo Medical University, Sapporo, Japan, 4The Department of Occupational Therapy, School of Health Sciences, Sapporo Medical University, Sapporo, Japan, 5The Department of Pediatrics, School of Medicine, Hokkaido University, Sapporo, Japan

P36-21 Cerebral networks underlying motor execution triggered by auditory omission

Conclusion: The symmetrically distributed PCA component during BP and NS could reflect activity of the premotor areas with radially oriented cortical generators. A second component started to appear during BP but was maximal and prevalent during MP. It probably represents bilateral activity of the motor cortex with generators oriented tangentially. Using PCA, it is possible to distinguish different components of the SRCP, probably corresponding to premotor and motor cortical activity.

Recovery of hindlimb locomotor function after spinal cord injury: A study using decerebrate animal models

Neurogenesis in the adult brain has been widely studied and a recent study has shown that hippocampal neurogenesis occurs in a time-of-day dependent manner. Oligodendrocyte precursor cell (OPC) is the main proliferating cell type in the adult brains, however, little is known about its proliferating manner. Here, we focused on adult hippocampal OPC proliferation in regard with the daily rhythm. To assess cell proliferation, we performed a BrdU-labeling assay during a 12:12 h light-dark cycle. We found that in the hippocampus, excluding the subgranular zone where neurogenesis typically occurs, there was a significant change in cell proliferation with greater numbers at the light phase. Immunohistochemical analysis revealed that the cells proliferating with daily variation were NG2 positive OPCs. Since hippocampalmediated learning and memory show a daily variation, I will discuss about the possible relationship between OPC proliferation and hippocampal function.

Hindlimb locomotor pattern evoked by the midbrain stimulation in decerebrate, paralyzed rabbits

The striatum can be divided into two compartments, patch and matrix, which are known to have distinct chemical compositions and connections. Here, neurons located in either patch or matrix were infected with recombinant sindbis virus, and their labeled axons were entirely reconstructed with a camera lucida. Some reconstructed axons originating from matrix arborized into the three main striatal targets, while some reconstructed axons originating from patch terminated at only external segment of globus pallidus. These data are inconsistent with the previous concept of a dual striatofugal system: direct/indirect and patch/matrix, and call for a reevaluation of the organization striatofugal projection system.