神经生理学导论

Neurophysiology is the study of how the nervous system functions, including the brain, spinal cord, peripheral nerves, and sensory organs. Neurophysiologists investigate the nervous system at multiple levels of organization, from functional systems and circuits to single neurons and neuronal compartments. A unifying focus is understanding the mechanisms that generate and propagate electrical impulses within and between neurons.

In 1771, Luigi Galvani demonstrated that electrical shock could make a dead frog muscle twitch, proposing 'animal electricity' as the cause. Later, in the 1840s, Emil Du Bois-Reymond proved that animal electricity was actually a nerve impulse or action potential. These discoveries established that electrical signals underlie nervous system function.

Developed in 1976 by Erwin Neher and Bert Sakmann, patch clamp electrophysiology uses a fine glass capillary electrode sealed onto a neuron to monitor electrical activity at the cell and molecular level. This technique allows researchers to study ion channels and membrane properties in exquisite detail, making it one of the most widely used methods for investigating neurons today.

Calcium imaging loads neurons with a fluorescent dye that changes brightness in response to elevated intracellular calcium concentration. Since calcium levels rise during action potentials, this technique provides an indirect measure of neuronal excitation across the entire neuron, allowing researchers to visualize activity patterns in living cells.

Optogenetics, developed in 2005, involves genetically engineering neurons to express light-sensitive ion channels called opsins. By activating these channels with targeted light, researchers can excite or inhibit specific neurons with unprecedented precision, enabling detailed manipulation of neuronal circuits and revealing how specific neurons control behavior.

Brain-machine interfaces monitor brain activity while a subject thinks about performing a task, such as moving a cursor. This neural activity is converted into computer commands that control external devices. This application demonstrates how neurophysiological research enables device control using thought, offering potential therapeutic benefits for patients with motor impairments.

Electroencephalography (EEG) uses electrodes placed on the skull to monitor electrical activity across the entire brain non-invasively. Electrocorticography (ECoG) places electrodes directly on the brain surface, typically during clinical procedures like epilepsy surgery, providing higher spatial resolution. Both techniques help neurophysiologists study large-scale brain activity patterns.