A "double-water-film electrode" has been developed for the long-term characterization of the electrical properties across the interface between the nodal (N) and internodal (A or B) cells and the vacuole along the length of an internode of Chara as functions of time and temperature. The electrode unit consisted of a pair of the water-film electrodes described elsewhere (Ogata 1983, Coster and others 1984, Chilcott 1988, etc.). The distance between two water-film probes was fixed at 10mm. By scanning the electrode unit, the spatial variations in electrical resistance and capacitance along the longitudinal axis of Chara were observed. Analysis was performed by applying an electrical equivalent circuit for the biomembrane (Philippson1921). Across the internode (-A or -B) central nodal cells interface, the specific parallel resistance (Rm) and the parallel capacitance (Cm) at 20℃ were 30±5×10-3Ωm^2 and 1.5±0.5×10-1F/m^2 (at 30Hz), respectively. And the series resistance (Rs), corresponding to the vacuole of the internode was 8×10-3Ωm^2. Study of temperature depencencies of Rm and Cm suggested that a dynamic homeostatic regulation was operating at the interface where numerous plasmaodesmata were observed with an electron microscope (Pickett-Heaps 1967, Spanswick and Costerton 1967). Assumming that the individual cylinder of plasmadesma was filled only with cytoplasm, the number of plasmodesma per interface was estimated at 2.6×10^5.

One of the main research questions in neuroimaging today is how best to combine the spatial accuracy of heamodynamic techniques, specifically functional magnetic resonance imaging (fMRI), with the high temporal resolution of electrographic recordings, specifically magnetoencephalography (MEG). In the majority of studies the approach taken is to constrain the generators at the loci identified by the "good heamodynamic localizers" and then estimate their timecourses from the average electrographic data. For such an analysis to be meaningful the changes in heamodynamic demand must match accurately the timelocked activations that survive the average of electrographic data. Although some evidence for some correlation in some activated areas the details are likely to be different, partly because of the widely different timescales involved and the different mechanism that generate the respective fMRI and MEG signals. We have repeatedly demonstrated good spatial resolution for the generators of the MEG signal with minimal but judicial constraints using magnetic field tomography (MFT), relying on a non-linear distributed source solution of the biomagnetic inverse problem [1].
The presentation will begin with a demonstration that accurate reconstructions from MEG data alone is indeed possible, even at the level of analysis of single trials or continuous activity [2]. The implications for such a capability will then discussed in terms of a series of examples showing how the new look at the dynamics of brain function help us understand normal [3,4] and pathological brain function [5]. Recent results using object recognition task and a task requiring the recognition of facial expression will be used to link studies of normal brain function and pathology. Specifically activity elicited by faces in an object (including faces) and emotional facial expression recognition tasks will finally be used to demonstrated feedforward and feedback type of activity. Finally these brain activations related to the processing of faces will be studied in schizophrenic subjects [5].

References
[1] Ioannides, A. A., Bolton, J. P. R., and Clarke, C. J. S. (1990) "Continuous probabilistic solutions to the biomagnetic inverse problem" Inverse Probl. 6: 523-542.

[2] Moradi, F., Liu, L.C., Cheng, K, Waggoner, R.A., Tanaka, K. and Ioannides, A.A. "Consistent and precise localization of brain activity in human primary visual cortex by MEG and fMRI" (Under review)

[3] Ioannides, A. A. (2001) "Real time human brain function: observations and inferences from single trial analysis of magnetoencephalographic signals" Clinical EEG 32: 98-111.

[4] Ioannides, A.A., Kostopoulos,G.K., Laskaris, N.A., Liu, L.C., Shibata, T., Schellens, M., Poghosyan, V. and Khurshudyan A. (2002) "Timing and connectivity in the human somatosensory cortex from single trial mass electrical activity" Human Brain Mapping 15:231-246.

[5] Streit M, Ioannides AA, Sinnemann T, Woelwer W, Dammers J, Zilles K, Gaebel W (2001) "Disturbed facial affect recognition in patients with schizophrenia associated with hypoactivity in distributed brain regions: a magnetoencephalographic study" Am J Psychiatry. 158:1429-1436.

Cervical spinal cord slices were prepared from adult rats. Intracellular recordings from motoneurons revealed that electrical stimulation of the ventralmost part of the dorsal funiculus (which contains primarily descending corticospinal axons) elicited EPSPs in 75% of the neurons.
The latencies of these EPSPs tended to be shorter than those elicited by dorsal horn gray matter stimulation. Pairs of subthreshold dorsal funiculus stimuli were able to elicit action potentials in motoneurons.
These data are consistent with previous morphological and electrophysiological studies indicating that cervical motoneurons receive both mono-and polysynaptic corticospinal inputs. In addition, motoneurons were markedly depolarized by iontophoretic application of AMPA or KA (7 out of 7 neurons), but only weakly depolarized by NMDA (1 out of 6 neurons). CNQX (but not AP-5) blocked EPSPs elicited by dorsal funiculus stimulation. Thus, corticospinal transmission to motoneurons is mediated primarily by non-NMDA glutamate receptors.

Each taste bud consists of 50~100 cells in mammalians. Among these taste bud cells, only part of them have chemical synapses with taste nerves. Since no chemical and electrical synapses have been confirmed among mammalian taste bud cells, the majority of taste bud cells are assumed to be supportive. In mouse taste buds, however, our optical recordings with a voltage-sensitive dye suggest the interactions among taste bud cells; the number of chemosensitive taste bud cells was larger than that of innervated ones by taste nerves, and that taste bud cells, which elicited either depolarizing or hyperpolarizing receptor potentials in response to taste substances, grouped by the polarity of their receptor potentials. We also found that mouse taste bud cells expressed gap junctions among them, and that serotonin or glutamate applied to their basolateral membranes generated oscillating currents and increased intracellular Ca2+. These results suggest that taste bud cells express chemical or electrical synapses among them, and that these cell networks process taste information. In other words, there may be micro-brains on tongues. Today, I show the basic properties of mouse taste cells such as their excitabilities and taste responses, and then discuss the role of taste bud cell networks.

Regulation of spontaneous rhythmic activity and preserved stimulus dependent pattern by spike timing dependent synaptic plasticity (STDP) were investigated in the hippocampal CA3 network model. With the presence of STDP, rhythmic activity such as theta rhythm might modify recurrent connections in the hippocampal CA3. In this study, we applied STDP to a hippocampal CA3 network model that causes spontaneous rhythmic activity. As a result, some local regions appeared in the network by themselves, from which the spontaneous rhythmic activity propagated toward surrounding area (source of propagation). We found that the frequency of the spontaneous rhythmic activity converged into one specific frequency depending on the shape of the STDP modification function. We also found that burst stimulation with sufficiently high frequency of bursts could produce a source of propagation at the stimulus site which may work as a memory trace.

Catecholamines such as norepinephrine and dopamine, are one of representative neurotransmitters in central and peripheral nervous system. The research of catecholamine has played an important role in understanding cardiovascular diseases (for example; hypertension and arrhythmia), psychiatric disorders (for example; psychosis and depression) and central nervous system degenerating disorders (for example; Parkinson's disease). In our laboratory, we have been studying the regulation of catecholamine synthesis, release and re-uptake in cultured bovine adrenal medullary cells, using as a model of brain catecholaminergic neurons , and collaborated it with Clinical Departments in our school. In my presentation, I will show you previous and current topics of our catecholamine research.

Exposure to volatile solvent vapors results in narcoticism, irritation, dizziness etc. In the chemical workplace, the toxic effect of chronic exposure with a relatively low concentration of chemical vapor is an urgent matter to be clarified. For example, 1-bromopropane, a newly introduced substitute for ozone layer depleting compounds, has been widely used as a cleaning agent for metal, electronics, optical instruments etc with no explanation of possible adverse effects on health.
Furthermore, central intolerance to a low-level of volatile chemical compound such as formaldehyde has become a social problem. In chemically intolerant individuals, cognitive problems such as difficulties in remembering or concentration have been commonly reported. In this seminar I briefly summarize our recent results on functional impairment in the hippocampal formation of animals chronically exposed to different volatile compounds separately such as, 1-bromopropane and formaldehyde.

In order to examine whether target saliency influences on smooth pursuit initiation, we measured changes in eye position during the open-loop period of smooth pursuit in monkeys. The visual stimulus consisted of red or green dots (0.5x0.5 deg) randomly projected on a wide visual field (70x40 deg). The pursuit target was a cluster of 14 dots (3x3 deg) in the same (green or red) color, while the remaining dots formed the stationary background. The density of the dots in the background was exactly the same as that of the target. By introducing visual stimuli consisting of elements that either matched the background or differed from the background in color, we manipulated the target's saliency prior to the onset of motion. We compared the changes in eye position over the 60 ms interval beginning at 50 ms after the onset of target motion (initial tracking responses, ITR), while colors of the dots in the target and background were different (salient), and while their colors were the same (non-salient). We found that target saliency specifically increased the ITR to centripetal target motion (when the target moved toward the fovea), but not to centrifugal target motion (when the target moved away from the fovea). By varying the delay of motion onset after its color change, we found that the effect of the target's saliency was obvious even when the target became salient as little as 100 ms before the onset of motion. These results suggest that the attention of the subject might increase the efficacy of visual information processing of centripetally moving targets. This mechanism would facilitate effective tracking of an object moving toward the observer.
Supported by: CREST/JST and AIST.