Manabu Tanifuji

Optical imaging of the in vitro guinea pig piriform cortex activity using a voltage-sensitive dye.

The spatio-temporal patterns of signal processing in guinea pig piriform cortex (PC) slices were analyzed by optical imaging using a voltage-sensitive dye. Slices (400 microns thick) were cut in a plane parallel to the lateral olfactory tract and perpendicular to the cortical surface. In all the anterior PC and the majority of the posterior PC preparations, neural activity elicited by electrical stimulation of layer Ia propagated along the same layer, then it invaded into layers II and III and propagated along them. In addition to the above pattern, invasion of activity into the deeper area than layer III was observed in some posterior PC preparations. Real-time imaging of an active zone evoked by Ia shocks and its spatio-temporal behavior will contribute to resolving olfactory information processing.

Optical responses evoked by single-pulse stimulation to the dorsal root in the rat spinal dorsal horn in slice.

Neuronal excitation evoked after dorsal-root (DR) stimulation in the spinal dorsal horn (DH) of rats was visualized with a high-resolution optical-imaging method, and the propagation mechanism was studied. Transverse slices of the spinal cord were obtained from 2-4 week-old rats and stained with the voltage-sensitive dye RH-482. Single-pulse stimulation to the primary-afferent A fibers in the DR attached to the slice evoked a weak, brief (<10 ms) excitatory optical response in the laminae I and III-V. When the stimulus intensity and duration were increased to activate both A and C fibers, an additional, much greater, and longer-lasting (>100 ms) excitatory response was generated in the laminae I-III, most intensely in the lamina II. A treatment with excitatory amino acid (EAA) antagonists, dl-2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2, 3-dione, significantly reduced the amplitude and duration of the response in the lamina II. The optical response in the antagonists-containing solution was quite similar to that recorded in a Ca2+-free solution that blocked afferent synaptic transmission. The late component (>10 ms) was, however, slightly greater than that in the Ca2+-free solution. Treatment with the ATP-receptor antagonist, suramin, had a minimal effect on the response in the presence of EAA antagonists. These results suggested that the propagation of the DR-stimulus-elicited excitation was contributed largely by EAA receptors, but also by other receptors to a much lesser extent.

Possible presence of the ATP-sensitive K+ channel in isolated spinal dorsal horn neurons of the rat

The ATP-sensitive K+ channel (KATP channel) is a K+ channel inhibited by cytoplasmic ATP. It was originally found in cardiac cells and recently in neuronal cells. Here, we present evidence indicating that the KATP channel also exists in spinal dorsal horn neurons: membrane currents were recorded by whole-cell voltage-clamp in spinal dorsal horn neurons isolated from young rats. The outward current was augmented by KATP channel activators nicorandil and minoxidil and reduced by the blocker glibenclamide. This glibenclamide-induced change in the current was augmented when the intracellular ATP was lowered and the reversal potential was shifted according to the external K+ concentration.

Signal propagation from piriform cortex to the endopiriform nucleus in vitro revealed by optical imaging

Optical signals were recorded from the posterior piriform cortex slices of guinea pigs stained with a voltage-sensitive dye to analyse spatio-temporal spread of neural activity evoked by electrical stimulation of afferent fibers. After propagation of activity along layers II and III, an isolated island of activity appeared deep to the layer III and moved caudally. Histological inspection revealed that the area where the island appeared corresponded well to the endopiriform nucleus. The present results provided an evidence for one of the main outflows of olfactory information from the posterior piriform cortex.

Genetic Evolution of a Logic Circuit which Controls an Autonomous Mobile Robot

In this paper, we propose a new approach to evolve controllers of autonomous robots, and experimental results of its application to a real mobile robot are described as well. It is based on two concepts: Firstly, behavior of a system in environment is generated by combinations of multiple sensory-motor reflexes, and secondly, the system behaves and evolves under the direct influence of its environment, thus the system is expected to adapt well for its environmental situations with flexibility.

Optical responses evoked by white matter stimulation in rat visual cortical slices and their relation to neural activities

To characterize optical responses (ORs) evoked by white matter (WM) stimulation in slices of rat visual cortex (VC) stained with voltage sensitive dyes, time course of ORs in each layer was investigated by recording ORs with a linearly aligned photodiode array, and the spatial patterns of the ORs at specified time after stimulation were investigated by a CCD camera in combination with stroboscopic illumination. The ORs recorded by the photodiode array were an increase in absorption at 700 nm and a decrease in the wavelength below 650 nm, suggesting that the ORs were dye related. The ORs were compared with field potentials (FPs) to clarify that neural events were represented by the ORs, and in support of this view, we found that the first order spatial differentials of ORs and that of FPs were in good agreement. We further compared ORs with intracellular responses, and found that the ORs mainly represent postsynaptic potentials (PSPs) of VC neurons except for the deeper part of layer VI, where a component representing action potentials in fibers stimulated directly was observed. The time-lapse imaging of ORs showed that excitation first propagated vertically up to layer I and subsequently in the horizontal direction along layers II-III and V-VI as in previous investigations. Spatio-temporal patterns of ORs under blockade of synaptic transmission were also investigated to reveal activity of fibers evoked by WM stimulation which produced such patterns of propagation.

Imaging a computational process in the visual cortex

Visual perception is a computational process reconstructing the 3D visual world based on the 2D images viewed by the two eyes, which inherently contains ill-posed problems due to information deficiency. A typical example is the correspondence problem in finding partner points between the two retinal images. A neural network model for solution of the correspondence problem was proposed by Marr (1982, Vision. San Francisco: Freeman and Co.), constructed of groups of neurons selectively responsive to different disparities of visual stimuli shown to the two eyes. This model solves the correspondence problem as a relaxation process of excitation working between the neuronal groups responding to the same disparity antagonized by inhibition working between those responding to different disparity. Optical recording of responses evoked in the rat visual cortical slice by electrical stimulation of the white matter demonstrated the relaxation process of excitation antagonized by inhibition. Copyright 1996 Elsevier Science Ltd.