[{"id":253430,"date":"2026-08-10T00:00:43","date_gmt":"2026-08-10T04:00:43","guid":{"rendered":"https:\/\/www.thetransmitter.org\/?p=253430"},"modified":"2026-09-22T14:52:48","modified_gmt":"2026-09-22T18:52:48","slug":"are-parts-of-the-memory-trace-found-in-the-astroengram","status":"publish","type":"post","link":"https:\/\/www.thetransmitter.org\/memory\/are-parts-of-the-memory-trace-found-in-the-astroengram\/","title":{"rendered":"Are parts of the memory trace found in the \u2018astroengram?\u2019"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"

Neurons have long taken top billing in memory, but researchers are making the case for astrocytes. <\/p>\n","protected":false},"author":32,"featured_media":253434,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","footnotes":""},"categories":[153],"tags":[87,27,726,301],"class_list":["post-253430","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-features","tag-astrocytes","tag-audio-research-news","tag-engrams","tag-neurons"],"acf":{"primary_tag":225,"doi_url":"https:\/\/doi.org\/10.53053\/DPLC5914","citation_count":"0","custom_js_library":"","hero_type":"feat_image","hero_alt_image":null,"hero_youtube":"","hero_video":null,"hero_layout":"landscape","hero_caption":"Glial gap:<\/strong> A lack of tools has stymied attempts to prove astrocytes play a role in recall.","hero_by":"Illustration by Andreea Jurj","hero_credit":"","hero_bg_color":"tan","authors":[253432],"other_authors":"","related_title":"Explore more from The Transmitter<\/em>","related_hide":false,"related_filter":"latest","related_tag":null,"related_category":null,"related_custom":{"articles":null},"related_custom_wwn":{"articles":null},"newsletter":"","banner_content":"","banner_url":"","apple_article_id":"8805349f-151c-4fd3-9584-e38c9e2d217a","apple_article_revision":"AAAAAAAAAAAAAAAAAAAAAQ==","google_button_text":"","google_btn_bg_color":"","tooltip_text":"","sidebar_related_hide":false,"sidebar_related_title":"related articles","sidebar_related_hide_images":false,"sidebar_related_articles":"","comps":[{"acf_fc_layout":"audio_comp","audio_title":"LISTEN TO THIS STORY:","audio":254758,"apple_link":"","spotify_link":"","google_link":""},{"acf_fc_layout":"copy_comp","copy":"The engram is nothing new in neuroscience. For decades, researchers have maintained that these neuronal clusters\u2014which activate during learning and fire again during recall\u2014house memories in the brain.<\/span>\r\n\r\nResearchers have shown that small groups of neurons switch on during learning, undergo lasting chemical and structural changes, and then fire again during recall. These groups\u2014called engrams\u2014are now <\/span>widely accepted<\/span><\/a> as the physical trace a memory leaves in the brain.\u00a0<\/span>\r\n\r\nBut it may not be so simple. Memory traces in the brain also tap astrocytes, says <\/span>Marta Navarrete<\/span><\/a>, principal investigator at the Cajal Neuroscience Center. The \u201castroengram,\u201d as she and her team described it earlier this year in a <\/span>Nature Reviews Neuroscience<\/span><\/i> Perspective<\/span><\/a>, is implicated in the study of memory. No one knows if astrocytes are capable of storing memory rather than providing memory support, \u201cbecause nobody tested [it] before,\u201d she says.\u00a0<\/span>\r\n\r\nThat\u2019s partially because the activity of astrocytes wasn\u2019t discovered until a 1990 <\/span>study<\/span><\/a>, and the field had been focused elsewhere. All the current tools for understanding how the brain works are \u201crelated with a neuronal cell,\u201d Navarrete says, and researchers haven\u2019t been able to assess \u201cif there are other types of cells related\u201d to this higher brain function.\u00a0<\/span>\r\n\r\nIt\u2019s possible the field would have considered astrocytes in memory sooner \u201cif Ram\u00f3n y Cajal and [Camillo] Golgi had started with astrocytes,\u201d says <\/span>Steve Ramirez<\/span><\/a>, assistant professor of psychological and brain sciences at Boston University. Though Ramirez himself showed that reactivating a specific group of neurons was <\/span>enough to trigger recall<\/span><\/a>, he now thinks astrocytes play some role. \u201cThey\u2019re their own computational unit that\u2019s processing their own aspects of memory,\u201d he says. \u201cEither in parallel with neurons, in a synergistic role, or maybe even totally separate from neurons.\u201d\u00a0<\/span>\r\n\r\nBut it needs to be proved. \u201cNow it\u2019s a matter of under which conditions, and when, and why,\u201d Ramirez says.\u00a0<\/span>\r\n\r\n[tt_text class='']N[\/tt_text]avarrete built her astroengram theory on work showing that a specific subset of astrocytes in the nucleus accumbens\u2014the small structure in the forebrain that processes reward signals\u2014is recruited during learning, and that reactivating or silencing that group is enough to change an animal\u2019s behavior. To demonstrate this, she created a tool called AstroLight<\/a> and mapped astrocytes in mice as they were trained to correlate a flash of light with the availability of sugar water, located in dispensers on either side of a chamber. Over time, the mice developed a preference for one dispenser over the other.\r\n\r\nHer team then reactivated those astrocytes using the AstroLight tool, and also with clozapine N-oxide, which switches on a receptor engineered into the tagged astrocytes. In both cases, the mice more strongly preferred the dispenser they had previously favored. The reactivation, says <\/span>Jun Nagai<\/span><\/a>, a team director at the RIKEN Center for Brain Science, who was not involved in Navarrete\u2019s study, suggests astrocytes are \u201ccontrolling retrievability of memory network activity.\u201d\u00a0<\/span>\r\n\r\nWhen Navarrete\u2019s group then silenced the same group of astrocytes, the mice visited the dispensers more evenly.\u00a0<\/span>\r\n\r\nNavarrete also points to a <\/span>study<\/span><\/a> by <\/span>Benjamin Deneen<\/span><\/a>\u2019s group at Baylor College of Medicine, which tracked c-FOS\u2014a gene that switches on in recently active cells\u2014in hippocampal astrocytes during fear conditioning. Astrocyte FOS switched on when mice were given electric shocks. Days later, when the researchers reactivated those same astrocytes in a room where the mice had never been shocked, the mice froze as though reliving the fear.\u00a0\u00a0<\/span>\r\n\r\nAnd she cites a 2025 <\/span>study<\/span><\/a> from Nagai's lab, which tracked astrocyte FOS across the brain during fear conditioning and recall. Nagai found that fear conditioning alone did not activate astrocyte FOS, but it caused adrenaline receptors to ramp up in a subset of amygdala astrocytes, priming the mice to recall the experience when they returned to the chamber the next day. Only during recall did astrocyte FOS surge.\u00a0<\/span>\r\n\r\n[tt_sidebar_image image_id='253482' credit='' author='' author_link=''][\/tt_sidebar_image]\r\n\r\nIn both cases, manipulating astrocytes changed the animals\u2019 behavior in ways linked to memory. Navarrete says her work checked both boxes on the classical engram checklist: Reactivating the astrocytes was sufficient to shift behavior, and silencing them weakened it. Astrocytes are \u201cnecessary and also sufficient for memory,\u201d she says.\u00a0<\/span>\r\n\r\n[tt_text class='']B[\/tt_text]ut not even the authors of this work fully agree. \u201cIt\u2019s too early to say astrocytes are part of the engram,\u201d Nagai says. The strongest evidence still points to neurons as the core of the engram, he says. Back in 2009, Sheena Josselyn<\/a>\u2019s group demonstrated that destroying neurons recruited during fear learning erased the memory entirely<\/a>, whereas destroying a similar number of random neurons had no effect. And in 2012, Ramirez and his colleagues showed the reverse: Reactivating fear-linked neurons caused mice to freeze<\/a> in a place where they\u2019d never been shocked.\r\n\r\nThose experiments showed that neurons can be a clean on\/off switch for memory, Nagai says. And no experiment has shown astrocytes can do anything like that.\u00a0<\/span>\r\n\r\nBut Nagai admits that astrocytes probably help control how neurons access memory, because the astrocyte ensembles his team identified and tagged during recall can help keep a memory consistent each time it\u2019s recalled.\u00a0<\/span>\r\n\r\nThere\u2019s also a question of whether the astroengram debate is conflating memory with emotional state. Ciaran Murphy-Royal<\/a><\/span>\u2019s group at the University of Montreal knocked down receptors<\/a><\/span><\/span>\u00a0that respond to adrenaline-like stress signals on astrocytes in the mouse amygdala. Afterward, the mice became fearless; they wandered to the edge of an elevated platform and peered over the side. At the least, this showed the animals felt a new emotion about their surroundings.\u00a0<\/span>\r\n\r\n[tt_sidebar_quote author='Ciaran Murphy-Royal<\/span>']It\u2019s kind of untangling those two things\u2014the emotional state and the memory itself\u2014that\u2019s going to be our challenge.<\/span>[\/tt_sidebar_quote]\r\n\r\nIf astrocytes are primarily regulating emotional state, studies based on fear conditioning might simply muddy the waters. \u201cIt\u2019s kind of untangling the two [emotional state and memory itself] that\u2019s going to be our challenge,\u201d Murphy-Royal says. He points to Nagai\u2019s astrocyte study and notes that the astrocyte calcium response doesn\u2019t extend beyond about two weeks, which may be too short if astrocytes are supposed to be part of a memory that lasts a lifetime.<\/span>\r\n\r\nThe astroengram idea Navarette described in the Perspective requires proving that astrocytes can trigger recall, and that recall breaks without them. \u201cIf you get both of those, then you\u2019re cooking with gas,\u201d says <\/span>Mark Cembrowski<\/span><\/a>, associate professor of cellular and physiological sciences at the University of British Columbia.<\/span>\r\n\r\n[tt_text class='']P[\/tt_text]roving it would require labeling a group of astrocytes identified during a learning task, reactivating them while silencing surrounding neurons, and then testing recall. However, that necessitates \u201ca temporally well-controlled perturbation tool for astrocytes,\u201d Nagai says, and \u201cwe don\u2019t have that yet.\u201d\r\n\r\nMostly what\u2019s available are chemogenetic and optogenetic tools, and although they work in neurons, they behave unpredictably in astrocytes. \u201cWhat one tool produces for a result in the brain may not necessarily be reproducible by another tool,\u201d Ramirez says. Chemogenetics \u201chas its own timescale and its own way of modulating the brain, he says, as do drugs and optogenetics.<\/span>\r\n\r\nEven if researchers could independently control both cell types, there\u2019s the problem of keeping the signal contained. Neurons are wired together, and activating one group can ripple into neighbors, Murphy-Royal says. This issue could be worse in astrocytes, which are physically connected by gap junctions that let calcium signals pass from one cell to the next. Experimenters hoping to switch on a specific group of astrocytes might have their signal leak to neighboring cells, tainting results.\u00a0<\/span>\r\n\r\n[tt_sidebar_image image_id='253479' credit='' author='' author_link=''][\/tt_sidebar_image]\r\n\r\nAn ability to control both types of cells may be getting closer. Tools have matured enough that researchers can now load genetic cargo into engineered viruses and achieve 90 to 95 percent astrocyte-specific targeting, says <\/span>Dheeraj Roy<\/span><\/a>, assistant professor of physiology and biophysics at the University at Buffalo. And this can be done without accidentally hitting surrounding neurons. In principle, Roy says, researchers could now tag both neuronal and astrocyte ensembles in the same mouse and then use DREADDs\u2014synthetic receptors delivered into cells via the same engineered viruses, and activated by injecting the clozapine N-oxide\u2014to activate astrocytes while silencing neurons to test whether astrocytes alone can drive recall.\u00a0<\/span>\r\n\r\nBut the real question is how to capture cell activity precisely rather than over hours. Navarrete built AstroLight to address that problem, and Nagai developed his own tool, i\u03b2ARK, to dampen astrocyte signaling in his 2025 study. But \u201ci\u03b2ARK is expressed forever in the first target astrocytes,\u201d Nagai says, making it impossible to pinpoint which moment matters. What's required is to be able to silence astrocyte signaling during sleep or before recall, he says, and find exactly what time point we need.<\/span>\r\n\r\n[tt_text class='']N[\/tt_text]ot everyone is convinced that would work. Murphy-Royal points out that if engram neurons\u2014the cells that actually drive the mice to freeze in fear\u2014are silenced, activating astrocytes that modulate those same neurons shouldn\u2019t produce recall. And even if the mice did freeze, the behavior could be caused by general fear rather than a specific memory. To tell the difference, Murphy-Royal says, researchers would need to check whether the mice freeze only in response to a fear cue they previously learned.\r\n\r\nAnd an experiment would need to confirm that the neurons are truly silenced and that astrocyte calcium is genuinely elevated, and then track behavior beyond the typical 3- to 10-minute recall window to rule out artificial effects, Nagai says. Navarrete is now attempting that kind of work\u2014tagging the astrocytes that switch on during learning and then trying to tease apart their activity from neuronal activity during recall. But what\u2019s missing are longitudinal tools \u201cto follow the same astrocytic ensembles over days or weeks and fully understand their role across memory formation, storage, and recall,\u201d she says.<\/span>\r\n\r\nEven then, Ramirez cautions, every experiment in this field has limits. \u201cA lot of our perturbation experiments that are revealing how can memory work\u201d may not map onto how memory actually occurs in a normal brain, he says. Still, Ramirez thinks the astroengram concept will find a place in memory neuroscience.\u00a0<\/span>\r\n\r\n\u201cI am willing to bet the house that astrocytes play a causal role in memories and are very much involved in everything that we call an engram,\u201d he says.\u00a0<\/span>"}]},"_links":{"self":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253430","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/users\/32"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/comments?post=253430"}],"version-history":[{"count":10,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253430\/revisions"}],"predecessor-version":[{"id":256672,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253430\/revisions\/256672"}],"acf:post":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/contributor\/253432"}],"acf:term":[{"embeddable":true,"taxonomy":"post_tag","href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags\/225"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media\/253434"}],"wp:attachment":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media?parent=253430"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/categories?post=253430"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags?post=253430"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}},{"id":253341,"date":"2026-08-06T14:00:02","date_gmt":"2026-08-06T18:00:02","guid":{"rendered":"https:\/\/www.thetransmitter.org\/?p=253341"},"modified":"2026-08-12T11:14:30","modified_gmt":"2026-08-12T15:14:30","slug":"new-findings-begin-to-resolve-theta-sweep-debate","status":"publish","type":"post","link":"https:\/\/www.thetransmitter.org\/memory\/new-findings-begin-to-resolve-theta-sweep-debate\/","title":{"rendered":"New findings begin to resolve theta sweep debate"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"

Theta sweeps have been mired in controversy for decades, but the field is starting to converge on a consensus view of their function.<\/p>\n","protected":false},"author":73,"featured_media":253345,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","footnotes":""},"categories":[152],"tags":[23,225,307,167],"class_list":["post-253341","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","tag-hippocampus","tag-memory","tag-spatial-cognition-and-navigation","tag-systems-neuroscience"],"acf":{"primary_tag":225,"doi_url":"https:\/\/doi.org\/10.53053\/WWTP4433","citation_count":"0","custom_js_library":"","hero_type":"video","hero_alt_image":null,"hero_youtube":"","hero_video":253343,"hero_layout":"landscape","hero_caption":"Sweeping success:<\/strong> As a mouse chases a piece of food on a string, cells in the brain\u2019s navigation system produce rapid bursts of activity called theta sweeps, which mentally map out the path toward the food.","hero_by":"Vollan et al<\/em>. 2026","hero_credit":"","hero_bg_color":"tan","authors":[231924],"other_authors":"","related_title":"Explore more from The Transmitter<\/em>","related_hide":false,"related_filter":"latest","related_tag":null,"related_category":null,"related_custom":{"articles":null},"related_custom_wwn":{"articles":null},"newsletter":"","banner_content":"","banner_url":"","apple_article_id":"155716bd-14c1-48bb-ac39-aaa227658f87","apple_article_revision":"AAAAAAAAAAAAAAAAAAAAAA==","google_button_text":"","google_btn_bg_color":"","tooltip_text":"","sidebar_related_hide":false,"sidebar_related_title":"related articles","sidebar_related_hide_images":false,"sidebar_related_articles":"","comps":[{"acf_fc_layout":"copy_comp","copy":"As an animal navigates the world, cells in the hippocampus and entorhinal cortex produce rapid, repeating bursts of activity called theta sweeps: Grid and place cells fire in a specific sequence, first plotting the location the animal has just passed, then where it is currently and lastly what lies ahead.<\/span>\r\n\r\nWhether these theta sweeps simply scan the surrounding environment or instead represent the deliberation and planning needed for goal-directed movement is \u201csomething that people have been arguing about for 30 years,\u201d says <\/span>David Redish<\/span><\/a>, professor of neuroscience at the University of Minnesota.<\/span>\r\n\r\nThat debate may now be over: Theta sweeps serve both functions, depending on the situation, according to three new studies by independent teams. The brain produces systematic sweeps by default to passively sample an environment, but it switches to active, targeted sweeps whenever an animal is pursuing a goal or focused on something specific, the studies show.\u00a0<\/span>\r\n\r\n\u201cIt changes our conception of what theta sweeps do,\u201d says <\/span>Edvard Moser<\/span><\/a>, professor of neuroscience at the Norwegian University of Science and Technology and an investigator on one of the new studies, published today in <\/span>Science<\/span><\/i><\/a>. The other two studies appeared last month in <\/span>Nature Neuroscience<\/span><\/i>.<\/span>\r\n\r\nTheta sweeps occur within individual theta wave cycles, which are around 125-250 milliseconds long. The teams were able to detect the sweeps\u2019 trajectories by recording hundreds of individual neurons at once in 10-millisecond blocks, a time resolution fine enough to see individual theta cycles, Moser says, adding that they are\u00a0 \u201cinvisible if you only look at the average.\u201d\u00a0<\/span>\r\n\r\nTogether, the studies show how theta sweeps begin to plan an animal's next steps rather than sampling the world, says Redish, who was not involved in the work. \u201cIt\u2019s really exciting to see how the field is really converging on mechanisms and circuits that can drive [theta sweeps].\u201d<\/span>\r\n\r\n[tt_text class='']D[\/tt_text]irection-selective cells in the parasubiculum coordinate theta sweeps, <\/span>previous<\/span><\/a> studies <\/span>show<\/span><\/a>. At the population level, these cells generate an \u201cinternal direction\u201d signal that swings roughly 30 degrees to either side of a rat\u2019s actual heading on alternating theta cycles, and grid cells align their sweeps to that internal signal rather than to the head axis itself. When rats passively navigate an environment, this produces theta sweeps that sample space in front of the animal in a coordinated left-right pattern, according to previous work by Moser and his colleagues.\u00a0<\/span>\r\n\r\n\u201cWe interpreted this as a search mechanism,\u201d Moser says. \u201cBut the question then was, could these sweeps actually be more flexible?\u201d\u00a0<\/span>\r\n\r\nTo find out, Moser and his colleagues made electrophysiological measurements of hundreds of neurons in the medial entorhinal cortex and parasubiculum as rats either searched for food crumbs in an open area or chased a piece of food suspended from a string. During the latter \u201cfishing rod\u201d experiment, the left-right theta sweeps narrowed the area they sampled to point in the direction of the dangling food, even if the animal couldn\u2019t reach it. Rather than tracking the animal\u2019s head direction, the sweeps zoomed in on wherever the rat was paying attention.\u00a0<\/span>\r\n\r\nWhen the rat lost track of the moving food target, theta sweeps turned toward the food source before the animal did, decoupling the neural signals from the head axis. This finding suggests that the sweeps do more than just encode a future trajectory, and instead encode an attention-like mechanism.\u00a0<\/span>\r\n\r\n[tt_sidebar_quote author='Gy\u00f6rgy Buzs\u00e1ki<\/span>']Theta waves \u201care giving you punctuation marks. They\u2019re giving you grammar and syntax of how information could be packaged.\u201d<\/span>[\/tt_sidebar_quote]\r\n\r\n\u201cIt\u2019s very tempting to call this attention, and I think it actually is,\u201d Moser says. \u201cBut there are extra requirements for attention, mainly that the animal needs to not attend to something else.\u201d<\/span>\r\n\r\nThe work from Moser indeed shows that \u201ctheta sweeps do just go wherever [a rat] is thinking about [going],\u201d says <\/span>Neil Burgess<\/span><\/a>, professor of cognitive and computational neuroscience at University College London, who is an investigator on one of the <\/span>Nature Neuroscience<\/span><\/i> papers.<\/span>\r\n\r\nAnd theta sweeps continued during REM sleep, switching between passive left-right sampling and more narrow, attention-like sweeps, the study found. \u201cSince REM sleep is when at least humans have their dreams, you can speculate that this is related to dreaming. But that's just pure speculation,\u201d Moser says.<\/span>\r\n\r\n[tt_text class='']I[\/tt_text]n Burgess\u2019s <\/span>study<\/span><\/a>, he and his colleagues recorded from roughly a hundred hippocampal place cells as rats navigated a \u201choneycomb\u201d maze, made from small, moving hexagonal platforms. Initially, all the platforms were level, and a rat could navigate the maze freely to learn locations where it would receive a bit of food.\u00a0<\/span>\r\n\r\nDuring subsequent trials, however, individual platforms were raised such that the rat could still move through the maze\u2014but not always in the direction that it wanted to go. Regardless, \u201cthe sweeps seem to be going toward the goal, even though the rat can never go there,\u201d Burgess says.<\/span>\r\n\r\nIn the other <\/span>Nature Neuroscience<\/span><\/i> study<\/span><\/a>, rats either foraged randomly for water or learned the locations of three other water sources, whose positions changed from session to session. While the rats were foraging randomly, the theta waves alternated between left and right, neural population recordings from hippocampal CA1 revealed. The sweeps also alternated during the goal-directed task, but were interspersed with sweeps toward goal locations.<\/span>\r\n\r\nThe goal-directed sweeps, the team also found, are preferentially replayed during sharp-wave ripples, which are linked to memory consolidation and occur during sleep and periods of rest.<\/span>\r\n\r\n\u201c[Theta sweeps are a] way of anticipating behavior by simulating a potential trajectory,\u201d says study investigator <\/span>Antonio Fernandez-Ruiz<\/span><\/a>, assistant professor of neurobiology and behavior at Cornell University. \u201cIf you close your eyes and you\u2019re thinking about what you want to do after this, you\u2019re mentally traveling. You\u2019re exploring your internal map and simulating\u2014what if I go to the grocery store, then the bar. That type of planning, I think, is the primary function of the hippocampus. These theta sweeps are a mechanism to explore internal representations, irrespective of behavior.\u201d<\/span>\r\n\r\n[tt_text class='']W[\/tt_text]hether goal- and attention-related theta sweeps reflect genuinely different mechanisms, or the same circuit-level process triggered by different kinds of targets, is unclear. \"Whether you call it goal orientation or attention, it\u2019s an internal representation,\u201d Redish says.<\/span>\r\n\r\nThe three studies are \u201centirely consistent,\u201d Moser says. \u201cBut it\u2019s not only a long-distance goal, it can be anything that momentarily demands an animal\u2019s attention.\u201d<\/span>\r\n\r\nGoal-directed sweeps may \u201cnot necessarily [be] tied to the external world\u201d as attention-like sweeps are, at least in the hippocampus, Fernandez-Ruiz says. Instead, they may be \u201cprimarily a way to explore internal representations independently of the external world,\u201d not just an immediate sensory experience. The exact purpose of the sweeps is \u201cup for debate,\u201d he adds.<\/span>\r\n\r\nTheta sweeps may explore or evaluate future trajectories, Redish says. \u201cThe current theory is that these hippocampal sweeps, at least when they\u2019re goal-oriented, are some sort of planning\u201d signal, he says.\u00a0<\/span>\r\n\r\nPlanning in general involves more than just the information a theta sweep provides, Moser says. \u201cThis is a way to scan the immediate environment within a very short time cycle. I think this is a short-distance planning mechanism for navigation, and maybe for other kinds of navigation in abstract thought.\u201d How theta sweeps connect to that longer-range planning is still an <\/span>open question<\/span><\/a>, he adds, and the overall mechanism through which the sweeps arise is also still unclear.<\/span>\r\n\r\nTheta sweeps, like many oscillations in the brain, may convey information to other brain areas, says <\/span>Gy\u00f6rgy Buzs\u00e1ki<\/span><\/a>, professor of neuroscience and neurology at the New York University Grossman School of Medicine. \u201cThe rhythms in the brain are the most important things for neural communication, because, like in every single communication system, you have to have a beginning and end of messages,\u201d Buzs\u00e1ki says. Theta waves \u201care giving you punctuation marks. They\u2019re giving you grammar and syntax of how information could be packaged.\u201d<\/span>"}]},"_links":{"self":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253341","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/users\/73"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/comments?post=253341"}],"version-history":[{"count":7,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253341\/revisions"}],"predecessor-version":[{"id":253700,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253341\/revisions\/253700"}],"acf:post":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/contributor\/231924"}],"acf:term":[{"embeddable":true,"taxonomy":"post_tag","href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags\/225"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media\/253345"}],"wp:attachment":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media?parent=253341"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/categories?post=253341"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags?post=253341"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}},{"id":253192,"date":"2026-08-06T00:00:58","date_gmt":"2026-08-06T04:00:58","guid":{"rendered":"https:\/\/www.thetransmitter.org\/?p=253192"},"modified":"2026-08-12T11:10:55","modified_gmt":"2026-08-12T15:10:55","slug":"reverse-engineering-neural-circuits-success-stories-from-computational-neuroscience","status":"publish","type":"post","link":"https:\/\/www.thetransmitter.org\/computational-neuroscience\/reverse-engineering-neural-circuits-success-stories-from-computational-neuroscience\/","title":{"rendered":"Reverse engineering neural circuits; success stories from computational neuroscience"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"

<\/span>Kevin Mitchell talks with Timothy Behrens about ring attractors, the role of innate structure, and an expanded view of cognitive maps.<\/p>\n","protected":false},"author":2,"featured_media":253206,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"","_relevanssi_noindex_reason":"","footnotes":""},"categories":[995],"tags":[735,143,23,56,1195,573,1196],"class_list":["post-253192","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-qa","tag-computation","tag-computational-neuroscience","tag-hippocampus","tag-neural-circuits","tag-qa","tag-theoretical-neuroscience","tag-video"],"acf":{"primary_tag":143,"doi_url":"https:\/\/doi.org\/10.53053\/AJGZ5140","citation_count":"0","custom_js_library":"","hero_type":"youtube","hero_alt_image":null,"hero_youtube":"5H1c1cZhjGU","hero_video":null,"hero_layout":"landscape","hero_caption":"","hero_by":"","hero_credit":"","hero_bg_color":"tan","authors":[200325],"other_authors":"","related_title":"Explore more from The Transmitter<\/em>","related_hide":false,"related_filter":"latest","related_tag":null,"related_category":null,"related_custom":{"articles":null},"related_custom_wwn":{"articles":null},"newsletter":"","banner_content":"","banner_url":"","apple_article_id":"a3a79cee-8124-4404-ac75-575754868f83","apple_article_revision":"AAAAAAAAAAAAAAAAAAAAAg==","google_button_text":"","google_btn_bg_color":"","tooltip_text":"","sidebar_related_hide":false,"sidebar_related_title":"related articles","sidebar_related_hide_images":false,"sidebar_related_articles":"","comps":[{"acf_fc_layout":"copy_comp","copy":"How do brains work? How do neural circuits in different parts of the brain perform the operations that the organism needs to get around in the world? In essence, these are the questions that the field of computational neuroscience sets out to answer. In this interview, I talk with <\/span>Timothy Behrens<\/span><\/a> about the field\u2019s goals and approaches, its place as a bridge between brains and minds, and the notable progress being made across many fronts. Behrens is professor of computational neuroscience at the University of Oxford and a <\/span>group leader<\/span><\/a> at the Sainsbury Wellcome Centre for Neural Circuits and Behaviour at University College London.<\/span>\r\n\r\nBehrens has been a leader in the field for many years and has a particular interest in cognitive maps. I reached out to him after seeing his recent series of <\/span>posts on Bluesky<\/span><\/a> listing some systems in which he thought computational neuroscience had made real progress; these include the <\/span>ring attractor<\/span><\/a> in the central complex of flies that tracks heading, the grid cell circuit for path integration in rodents and the song learning circuit in zebrafinches, among others. I wanted to know what prompted him to write this list and what his criteria were for success.\u00a0<\/span>\r\n\r\nIn our conversation, which you can watch on this page, Behrens cites two main factors underlying progress in these specific systems. The first is that they operate over a fairly low-dimensional space\u2014the problems these systems have to solve are just not that complex (not in isolation, at least). The second is that, because the ecological tasks carried out by these circuits are so basic and so essential, evolution may have hard-wired the solutions into the circuit design.<\/span>\r\n<\/span>\r\n\r\nBoth Behrens and I suspect that much more of the brain is like that than most people think. The current preoccupation with learning rules and algorithms and the successes of large language models can make it seem like \u201call you need is learning.\u201d But this obscures the fact that brain circuits are highly diverse in their local architectures, with very specialized cells connected in very stereotyped ways. Hardware and software co-evolved in brain evolution\u2014indeed, they cannot be separated in the way they are in digital computers.\u00a0<\/span>\r\n\r\nAs Behrens points out, even flexible, learned behaviors benefit from some innate representations, or at least <\/span>an innately structured representational space<\/span><\/i>. He describes how such structured circuitry, mapping things such as physical space and progress toward goals, can be combined to build representations of complex tasks.\u00a0<\/span>\r\n\r\n[tt_text class='']M[\/tt_text]uch of Behrens\u2019 own work focuses on cognitive maps. These maps, as first conceived in 1948 by Edward Tolman, referred to an <\/span>internal causal model<\/span><\/a> that animals can use to navigate their surroundings and to predict what will happen if they take a particular action in the world. Thirty years later, John O\u2019Keeffe and Lynn Nadel developed this idea specifically in the <\/span>context of the hippocampus<\/span><\/a>. As it happens, these structured cognitive spaces are often physically laid out in ways that really do look like maps across the brain.\u00a0<\/span>\r\n\r\nThis structure likely reflects a core principle of wiring efficiency: Because neurons tend to connect most often with other neurons that are nearest to them in space, specialized clusters will tend to arise as a result of learning. But the fact that the layout of such clusters tends to be quite consistent across individuals strongly suggests it is scaffolded by some innate structuring of neural circuits. The amazing thing is that these kinds of maps are evident not just for things such as categories of visual objects, but also for much more abstract semantic concepts.<\/span>\r\n<\/span>\r\n\r\nBehrens\u2019 work explores how hippocampal maps work and interact with the cortex. Growing evidence suggests a more abstract role for the hippocampus beyond simple mapping of memory and space. In Behrens\u2019 view, this can account for the diverse functions of this structure in tracking movements in space, series of events, progress toward tasks, and many other cognitive parameters. We also touch on the crucial, but still mysterious, role of temporal oscillations in shaping communication between the hippocampus and cortex.\u00a0<\/span>\r\n\r\nIn closing, we discuss some of the exciting technological developments that are powering advances in computational neuroscience today. One of these is the growing ability to perform incredibly powerful experiments in animals\u2014using techniques such as optogenetic holography, for example\u2014to deduce detailed mechanisms underlying complicated cognitive tasks. Behrens is optimistic that these approaches will help fulfill the mission of computational neuroscience: to work out how animals learn about their world, how this knowledge is structured, and how those structures enable the processes of cognition to take place.<\/span>\r\n\r\nWatch our conversation<\/a> and read the transcript<\/a>."}]},"_links":{"self":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253192","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/comments?post=253192"}],"version-history":[{"count":10,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253192\/revisions"}],"predecessor-version":[{"id":253699,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/posts\/253192\/revisions\/253699"}],"acf:post":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/contributor\/200325"}],"acf:term":[{"embeddable":true,"taxonomy":"post_tag","href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags\/143"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media\/253206"}],"wp:attachment":[{"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/media?parent=253192"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/categories?post=253192"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thetransmitter.org\/wp-json\/wp\/v2\/tags?post=253192"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}]