While Murayama was doing his PhD research in the early 2000s, researchers like Jackie Schiller started to report the discovery of a new kind of firing in brain cells. But finding the spike first involved an Alpine detour. A string of studies published by Murayama and colleagues has zoomed in on the dendritic spike as the necessary signal for accurate perception. The thinking is that accurate memory requires accurate conscious perception, which in turn relies on the right kind of brain cell activity. In another touchy-feely task, mice explore different floor textures making use of their natural attraction to novelty, researchers can test whether mice remember experiencing certain textures on previous days. The air puff is just one in a suite of experimental sensory tests used in his lab to evoke responses in the mouse somatosensory cortex. It doesn’t seem accidental that Murayama’s research program now revisits some of these formative, intensely tactile themes. During the day he staved off drowsiness by jabbing himself with a pencil, then returned to the newspaper offices to stuff ads in the papers. To pay for all the intense after-hours studying, he delivered newspapers both day and night. When his teenage ambition of becoming a professional footballer fell apart in the wake of the Japanese economic bubble, he had some catching up to do, and in true Japanese fashion he headed to the cram school. Now the laser-focused scientist, Murayama knows a thing or two about maintaining an awake state. “We think it has a crucial role in consciousness.” “The dendritic spike is a powerful computational element in the brain that occurs frequently in the awake, conscious state,” Murayama explains. Paws and their representation in the brain are also more comparable to the whiskerless human experience.Ī puff of air to the mouse hindpaw launched Murayama’s quest to figure out the neural activity underlying consciousness, and in the past decade it has led him to the dendritic spike, an atypical electrical discharge generated within the cellular arbors at the receiving end of many neurons in mouse cortex. The stimulation of whiskers, says Murayama, may induce more than just sensory phenomena, since stimulated whiskers will subsequently move on their own, and active whisking will include motor signals. Murayama took a different tack, eschewing whiskers in favor of the mouse hindpaw. Research on somatosensation in mice has traditionally focused on whiskers: stimulate a whisker, record the activity from the corresponding part of the brain called the barrel cortex which, like many perceptual areas of the brain, is structured like a map, neighboring whiskers represented by neighboring neurons. The mouse brain is roughly the size of a pinky fingertip and has about 70 million neurons. And when you’re looking for the basic building blocks of any scientific phenomenon, you have to start small and simple. Scientists are trying to find the minimum number and configuration of supporting blocks that distinguishes the upright tower of consciousness from the toppled pile of blocks in unconscious states like sleep or anaesthesia. “For me, perception seemed the easiest and most accessible.” The search for NCC is like reverse-engineering a Jenga tower. “We can’t study consciousness itself, but we can study the individual brain functions, like perception or decision-making or emotion, that make up consciousness,” says Murayama. A tinkerer by nature, scientific questions for Murayama are not just about biology, but about how new technology can extend our senses to probe hidden realms. He has built his own experimental equipment, relocated around the world for science, and even delivered newspapers at night to fund his studies. Murayama is nothing if not enterprising in this quest. He thinks if we can just describe how the brain perceives the world with sufficient accuracy - the underlying cellular activity and connections - we’ll have largely also found those elusive ‘neural correlates of consciousness’ (NCC), the brain signatures that define the awake, sentient state thought to be unique to higher mammals. “Shaking hands changes the surface tension of the skin,” observes Murayama, “while looking at someone’s face, for example, doesn’t change the face itself.” It is the act of touching and perceiving textures, or somatosensation, and the intimate link with the brain from the skin and the underlying muscle that is the object of Murayama’s ascending research career. The blanket of cells that covers the body is the most direct, keen connection we have to the world. If you ask Masanori Murayama, the path to unlocking consciousness starts in the skin.
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