Single-unit Recording - History

History

The ability to record from single units started with the discovery that the nervous system has electrical properties. Since then, single unit recordings have become an important method for understanding mechanisms and functions of the nervous system. Over the years, single unit recording continued to provide insight on topographical mapping of the cortex. Eventual development of microelectrode arrays allowed recording from multiple units at a time.

• 1790s: The first evidence of electrical activity in the nervous system was observed by Luigi Galvani in the 1790s with his studies on dissected frogs. He discovered that you can induce a dead frog leg to twitch with a spark.
• 1888: Santiago Ramón y Cajal, a Spanish neuroscientist, revolutionized neuroscience with his neuron theory, describing the structure of the nervous system and presence of basic functional units— neurons. He won the Nobel Prize in Physiology or Medicine for this work in 1906.
• 1928: The first account of being able to record from the nervous system was by Edgar Adrian in his 1928 publication “The Basis of Sensation”. In this, he describes his recordings of electrical discharges in single nerve fibers using a Lippmann electrometer. He won the Nobel Prize in 1932 for his work revealing the function of neurons.
• 1940: Renshaw, Forbes & Morrison performed original studies recording discharge of pyramidal cells in the hippocampus using glass microelectrodes in cats.
• 1950: Woldring and Dirken report the ability to obtain spike activity from the surface of the cerebral cortex with platinum wires.
• 1952: Li and Jasper applied the Renshaw, Forbes, & Morrison method to study electrical activity in the cerebral cortex of a cat. Hodgkin-Huxley model was revealed, where they used a giant squid axon to determine the exact mechanism of action potentials.
• 1953: Iridium microelectrodes developed for recording.
• 1957: John Eccles used intracellular single-unit recording to study synaptic mechanisms in motoneurons (for which he won the Nobel Prize in 1963).
• 1958: Stainless steel microelectrodes developed for recording.
• 1959: Studies by David H. Hubel and Torsten Wiesel. They used single neuron recordings to map the visual cortex in unanesthesized, unrestrained cats using tungsten electrodes. This work won them the Nobel Prize in 1981 for information processing in the visual system.
• 1960: Glass-insulated platinum microelectrodes developed for recording.
• 1967: The first record of multi-electrode arrays for recording was published by Marg and Adams. They applied this method to record many units at a single time in a single patient for diagnostic and therapeutic brain surgery.
• 1978: Schmidt et al. implanted chronic recording micro-cortical electrodes into the cortex of monkeys and showed that they could teach them to control neuronal firing rates, a key step to the possibility of recording neuronal signals and using them for BMIs.
• 1981: Kruger and Bach assemble 30 individual microelectrodes in a 5x6 configuration and implant the electrodes for simultaneous recording of multiple units.
• 1992: Development of the "Utah Intracortical Electrode Array (UIEA), a multiple-electrode array which can access the columnar structure of the cerebral cortex for neurophysiological or neuroprosthetic applications".
• 1994: The Michigan array, a silicon planar electrode with multiple recording sites, was developed. NeuroNexus, a private neurotechnology company, is formed based on this technology.
• 1998: A key breakthrough for BMIs was achieved by Kennedy and Bakay with development of neurotrophic electrodes. In patients with amyotrophic lateral sclerosis (ALS), a neurological condition affecting the ability to control voluntary movement, they were able to successfully record action potentials using microelectrode arrays to control a computer cursor.