Tham khảo tài liệu 'new developments in biomedical engineering 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 312 New Developments in Biomedical Engineering Extracellular Recording Although intracellular recordings provide the measurement of the intracellular potential of a cell they are in any case invasive to the cell and its membrane. These recordings are therefore always limited in time. This rules out some investigations of important communication processes such as late phase long-term potentiation LTP recordings. Potential changes of the membrane of a cell can also be measured from the outside of the membrane without making any physical contact to the cell. Glass micro-electrodes or thin insulated metal electrodes can be used for extracellular recording of the membrane potential. Ionic movements across cell membranes are detected by placing a recording electrode close to the cell. The extracellular signal recorded upon the firing of an action potential is characterized by a brief alternating voltage between the recording electrode and a ground electrode. Extracellular recordings with a glass electrode are thus advantageous in the investigation of long-term processes such as LTP. Because the electrode is in close proximity but not in direct contact with the cell the recordings are usually stable and not liable to mechanical instabilities. Although activity can be detected at the level of a single cell recordings usually reflect the averaged response of a population of cells. Despite the non-invasiveness of this method the throughput of this type of experiments is rather low. The researcher has to manually bring the electrodes close to the cell membrane to be able to perform the recordings. With the progress in micro-fabrication techniques planar micro-electrodes were developed that were able to record extracellularly from cultured cells grown on top of the electrode area. Planar micro-electrodes have been used as substrates for the culture support and non-invasive recording of cells and electrical activity of single cells and networks of cells have been monitored
