Abstract: A method and an apparatus are disclosed for measuring the electrical properties of biological cells. The method involves a switching excitation with a sinusoidally amplitude-modulated current coupled with a real-time estimation algorithm for extracting a phase-shifted sinusoidal voltage output. The algorithm uses a unique time-domain formulation that provides accurate and continuous measurements with a high temporal resolution. The invention is suitable for measuring small signals under noisy conditions such as the membrane resistance and capacitance of a living cell accessed via a microelectrode. The resulting apparatus achieves a similar effect of a lock-in amplifier for suppressing noise but with a different approach. The invention also has the advantage that the input and the output can be decoupled by time-multiplexing on a single electrode.

Abstract: A digital stereotaxic manipulator for animal research is provided with two enhancements. In one enhancement, rotary encoders are provided, to allow tilting of the manipulator, about vertical and/or horizontal axes, to be measured within a fraction of a degree. With assistance from software that applies sine and cosine values, orthogonal coordinates that are emitted by linear reader heads can be corrected to provide accurate orthogonal coordinates, even when an instrument has been rotated and/or tilted substantially. In a second enhancement, a “fine-drive” mechanism provides precise control over dorsal/ventral motion of an instrument. A radial gear is mounted on the main threaded shaft in the vertical arm assembly. A helical gear on a horizontal shaft is used to drive rotation of the radial gear and vertical shaft. If a 1:20 gearing ratio is provided by the helical and radial gears, this provides an operator with 20-times more precise control over vertical motion of an instrument.

Abstract: A system is disclosed that allows stereotaxic procedures being performed on lab animals to interact, on a “live” or “real-time” basis, with information that has been compiled in stereotaxic brain atlases. For example, during an invasive procedure, a researcher can see, on a cross-sectional brain map displayed on a full-sized computer monitor, the location and travel of an instrument tip, indicated by means such as a bright blinking cursor or icon. If desired, important brain structures (such as major nerve bundles) can been prominently labeled and/or colored, to clearly indicate their locations, and help the researcher ensure that they are avoided. This system can be provided by coupling a digital stereotaxic manipulator to a dedicated controller with touch-screen capability, and coupling the PLC processor to a computer having a monitor screen that is large enough to display a brain map with good resolution.