Microneurography

Microneurography is a neurophysiological method employed by scientists to visualize and record the normal traffic of nerve impulses that are conducted in peripheral nerves of waking human subjects. The method has been successfully employed to reveal functional properties of a number of neural systems, e.g. sensory systems related to touch, pain, and muscle sense as well as sympathetic activity controlling the constriction state of blood vessels. To study nerve impulses of an identified neural system, a fine tungsten needle electrode is inserted into the nerve and connected to a high gain recording amplifier. The exact position of the electrode tip within the nerve is then adjusted in minute steps until the electrode discriminates impulses of the neural system of interest. A unique feature and a significant strength of the microneurography method is that subjects are fully awake and able to cooperate in tests requiring mental attention, while impulses in a representative nerve fibre or set of nerve fibres are recorded, e.g. when cutaneous sense organs are stimulated or subjects perform voluntary precision movements. Microneurography is a neurophysiological method employed by scientists to visualize and record the normal traffic of nerve impulses that are conducted in peripheral nerves of waking human subjects. The method has been successfully employed to reveal functional properties of a number of neural systems, e.g. sensory systems related to touch, pain, and muscle sense as well as sympathetic activity controlling the constriction state of blood vessels. To study nerve impulses of an identified neural system, a fine tungsten needle electrode is inserted into the nerve and connected to a high gain recording amplifier. The exact position of the electrode tip within the nerve is then adjusted in minute steps until the electrode discriminates impulses of the neural system of interest. A unique feature and a significant strength of the microneurography method is that subjects are fully awake and able to cooperate in tests requiring mental attention, while impulses in a representative nerve fibre or set of nerve fibres are recorded, e.g. when cutaneous sense organs are stimulated or subjects perform voluntary precision movements. Before the microneurography technique was developed in the late 1960s, impulses in peripheral nerves had been recorded in animal experiments alone using a technique that involved dissection and splitting the nerve. This approach is not tolerable for general use in man although it has been pursued in one single study. Actually, the concern of nerve damage was a major obstacle for the development of microneurography because the approach of inserting a needle electrode in a human nerve was generally regarded as highly dangerous involving substantial risks of permanent nerve damage. The two Swedish scientists who developed the microneuropgraphy technique (Hagbarth and Vallbo) handled the medical-ethical concern by performing a large series of experiments on their own nerves during a period of about 2 years while carefully checking for nerve damage. Working at the Department of Clinical Neurophysiology, Academic Hospital, Uppsala, they collected data resulting in the first complete papers representing three areas to become major fields of microneurography, i.e. afference from intra-muscular sense organs during voluntary contractions, response of cutaneous sense organs related to touch stimuli, and efferent sympathetic activity controlling the constriction state of human blood vessels. The microneurography approach of Hagbarth and Vallbo based on epoxy resin coated tungsten electrodes is now generally accepted whereas an alternative attempt using glass coated platina-iridium electrodes had obviously limited success as it yielded a single short note alone.