The mouse is fully alert. It is investigating a new item that has been placed in its cage, paws at work, whiskers twitching, engaging in all the activities of a curious and thoroughly sleep-deprived mouse. Yet, within one region of its brain, a section of cortex has discreetly drifted into slumber. Not in a metaphorical sense. The neurons in that area are fluctuating between bursts of activity and periods of complete stillness, following the same rhythm they would adopt during deep sleep, all while the animal continues its exploration as if nothing is wrong.<\/p>\n
That peculiar dual state is the result of scientists at the University of Wisconsin-Madison, who have succeeded in inducing a sleep-like pattern in one area of the brain while the rest remains alert. This technique, detailed this week in Nature Neuroscience<\/em>, appears to provide that small patch some of the healing it would typically receive from a good night’s sleep.<\/p>\n To grasp why this is significant, it’s essential to understand the actual activities of the sleeping brain. During non-REM sleep, which constitutes about 80 percent of an adult’s nightly sleep, cortical neurons cease their waking conversations and begin to fire in unison: all active, all inactive, repeatedly, hundreds of times per minute. These are the slow waves observable on an EEG. They are generally believed to be the phase when the brain assesses its connections, reinforcing the synapses worth retaining, eliminating the unnecessary ones, and creating space for new learning the following day.<\/p>\n This naturally leads to an important question. If those on\/off patterns are responsible for the much-needed restoration, could you manually set them up?<\/p>\n Chiara Cirelli and her team had a head start. They had previously demonstrated that sleep-deprived rats and humans experience brief, intermittent phases of slow-wave activity even while awake, a phenomenon they term local sleep. The hitch is that these episodes are too brief and too scattered to be beneficial (and they can interfere with performance if they occur in the wrong area at an inopportune time). However, no one had attempted to make the patterns intentional, sustained, and targeted at a specific location.<\/p>\n \u201cWhat we\u2019re effectively doing is inducing sleep in a localized area of the brain,\u201d Cirelli explains. The team employed optogenetics, a method that uses light to turn genetically modified neurons on and off.<\/p>\n They explored two pathways leading to the same goal. In one group of mice, they utilized light to activate a type of inhibitory cell known as somatostatin interneurons, which function as a sort of master brake on the local circuitry; in another group, they silenced the excitatory pyramidal neurons directly. In either case, for 30 minutes at the end of a five-hour sleep deprivation, one side of the cortex was driven through the slow rise and decline of induced inactive periods while the mouse remained awake and engaged. Following this, they allowed the animals to sleep and observed. On the stimulated side, slow-wave activity during subsequent sleep was lower than on the unaltered side. In simpler terms, that portion of the brain acted as if it had less recovery to do. It required less sleep because, in a way, it had already received some.<\/p>\n This is the aspect that surprised me. One might think the advantage arises simply from granting tired neurons a break, from reducing their activity. Some researchers have posited that view. Yet when the team employed a different tool to lower the overall firing rate to the same diminished level, without the rhythmic alternation, the effect disappeared. There was no decline in subsequent slow waves, no indication of relief. It was the on-and-off pattern itself that was crucial, the switching, not just the quiet.<\/p>\n The molecules echoed this narrative. After the awake stimulation, the treated cortex exhibited reduced levels of certain AMPA receptors, the proteins that gauge the strength of a synapse, resembling what one would anticipate discovering after a period of genuine sleep.<\/p>\n Then came the pivotal test. Mice learned to differentiate between two floor textures, a task that relies on sleep to consolidate memory. Some were permitted to sleep; others were kept awake for an hour; and a third group remained awake but received the on\/off stimulation throughout both sensory and motor cortex. The sleep-deprived animals that received no intervention performed poorly the next day. The ones that received the stimulation, even after missing their sleep, remembered nearly as well as the mice that had slept. The memory had effectively been preserved without the sleep that typically facilitates it.<\/p>\n None of this implies that a device for bypassing sleep is imminent. The research is conducted in mice, the methodology<\/p>\n","protected":false},"excerpt":{"rendered":" The mouse is fully alert. It is investigating a new item that has been placed in its cage, paws at work, whiskers twitching, engaging in all the activities of a curious and thoroughly sleep-deprived mouse. Yet, within one region of its brain, a section of cortex has discreetly drifted into slumber. Not in a metaphorical […]<\/p>\n","protected":false},"author":2,"featured_media":372952,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"Default","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[179],"class_list":["post-372951","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-source-scienceblog-com"],"_links":{"self":[{"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/posts\/372951","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=372951"}],"version-history":[{"count":0,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/posts\/372951\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=\/wp\/v2\/media\/372952"}],"wp:attachment":[{"href":"https:\/\/wolfscientific.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=372951"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=372951"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wolfscientific.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=372951"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}A section of cortex, switched off on demand<\/h2>\n
Memory preserved from a sleepless night<\/h2>\n