I’m the scientist who has proved it really is possible to erase bad memories – and replace them with good ones. This is how it works… and what it means for the future: PROF STEVE RAMIREZ
It’s an idea straight out of a sci-fi blockbuster: having the ability to change a person’s memory. Wiping it clean; expunging bad experiences from your mind; turning traumatic thoughts into uplifting ones, or even implanting new memories and experiences – the idea scientists might be able to ‘rewire’ our memory is one that has long fascinated everyone from philosophers to movie scriptwriters. Think Eternal Sunshine Of The Spotless Mind meets Total Recall. The ability to change a memory feels almost omnipotent. But as someone who has achieved just this kind of memory manipulation as part of my groundbreaking research, let me tell you this: being a memory researcher is more like being a mechanic of the brain, taking apart the fleshy machine between our ears one piece at a time in an attempt to understand what each piece does and how it enables our smooth mental time-travel. This is because each memory leaves a kind of lasting physical imprint in the brain – somehow, the marvellous waters of memory carve measurable grooves in the neural riverbeds of the brain. This can be observable on fMRI brain scans. Put very simply, when you think of something – the moment you last embraced your parent, broke up with a girlfriend, played with a beloved pet – certain areas of the brain light up with activity. These spots are the physical site that process this particular memory. There’s an official term for this memory trace: an engram. Professor Steve Ramirez says he believes finding engrams is the key to unlocking the power of our brain’s mental time machine I believe finding engrams is the key to unlocking the power of our brain’s mental time machine. And the real-life therapeutic possibilities in being able to manipulate someone’s memory are almost unimaginably vast. One application is in mental health conditions. Our knowledge of engrams means they should no longer be perceived as purely untouchable, but as physically traceable as an oncologist finding a cancer cell or a dentist finding a cavity. And, therefore, potentially just as repairable. I believe that one day negative memories could be suppressed to prevent the debilitating effects of post-traumatic stress disorder (PTSD), or ease a bout of overwhelming anxiety to prevent a panic attack. Positive memories could also be activated to curb symptoms of depression. And I can even see that, eventually, we will reach a time when we can restore entire memories that have been lost – with direct relevance for those suffering from amnesia or who have Alzheimer’s. Memories damaged by conditions like these could be rejuvenated by the new discoveries we have made. So much of the workings of our brain remains unknown – and, needless to say, our brains are extraordinarily complex. Indeed, while our memories have a concrete basis – they are measurable, viewable and controllable – the neurons (or nerve cells) that transmit them fire in idiosyncratic patterns mere milliseconds in duration. And single engrams aren’t just housed in one spot, but rather are a constellation of neurons, distributed throughout the brain. And the average human brain has 86 billion neurons! But still, in May 2011, in a windowless dark room at the Brain and Cognitive Sciences building at the Massachusetts Institute of Technology, I took part in pioneering research with my then lab partner, Xu Liu, that proved scientists can manipulate memories. Using a small black mouse as our subject, we hoped to ‘turn on’ a memory if we triggered the parts of the brain where that memory lived. First, we anaesthetised this mouse before carefully placing two glass barrels into the top of its skull. Like miniature flashlights, shorter than the nail on your little finger, these glass barrels were capable of focusing light onto the part of the mouse’s brain in which they are nestled – in this case, the mouse hippocampus, the memory centre of the brain. Why did we want to shine light onto the mouse’s hippocampus? As part of our experiment, we’d made this particular mouse special using some genetic trickery called optogenetics. Essentially, optogenetics entails handcrafting special bits of DNA that make a cell light-sensitive. Once these brain cells are made light sensitive, researchers can turn them on or off with light, like a switch. We planned to focus beams of light directly on to our newly light-sensitive cells in the hippocampus. Based on what was already known about the inner workings of the brain, we had every reason to believe that the hippocampus, which contains millions of brain cells, is like a mental time machine: an area that’s active when a mouse is trying to remember the shortest path to return to the tasty crumbs in the kitchen pantry, or in one of us humans, when you recall last Friday’s delicious steak frites dinner. The hippocampus, in short, teleports us to relive the past. Our next step was to create a fear memory we could then try to manipulate. Typically in rodent studies this is done by placing the animals in a new environment – in this case a small box with a metal grid for a floor, dim lighting, and a black triangular roof scented with a zesty orange aroma – and sending a very mild electric shock to their feet. They’re thus conditioned: trained to associate the environment with a negative stimulus, which would make them freeze. Then we placed our study mouse into an almond-scented box with white floors, transparent walls and a camera mounted overhead, which it had previously investigated and associated with nothing important: it had no reason to be afraid this time. We connected the glass barrels in the mouse’s brain to a laser, then funnelled pulses of light into the light sensitive cells to awaken the dormant fear memory. When we did so, despite being in the ‘safe’ white box, the mouse immediately froze in place. Our experiment had worked. When we published our findings in 2012 in the journal Nature, our work received international attention. Further discoveries followed, some from our own expanding team of memory researchers. We already knew the act of recalling a memory puts it in a susceptible state at a cellular level – in other words, just remembering something makes the memory physically vulnerable in the brain. This is because when you remember something, your brain must then store it again – which, just like when it was stored the first time, requires the production of new proteins within the brain. Proteins are a bit like neural mortar, holding the bricks – here, the cells containing the memory – together and making them accessible for future use. The more you remember something, and successfully re-store it, the more hard-wired it becomes in your mind. This is perhaps why older people remember things from long ago better than recent memories – because older memories are processed and stabilised in the brain’s cortex, the outer layer of the brain, while new memories tend to be processed and made malleable in the hippocampus. Memories can be both weakened and strengthened by stimulating the human brain itself WAYS TO IMPROVE MEMORY NOW Away from the lab, there are things we can do to help our memories. Exercise – any! – in particular remodels memory circuits of the brain by promoting the creation of new brain cells. And the fresher the cells, the more likely they are to help process memory or participate in storing and retrieving memories. Dancing, walking, jogging, yoga and any form of exercise can be particularly effective at treating disorders of the brain. Both regions form a real-time dialogue every time a memory is stored and recalled. However, if you administer a drug called anisomycin which blocks proteins in the brain at the moment of recall, you can block the reconsolidating of the memory – thus creating a kind of amnesia for that experience. In 2015, my then colleague Tomas Ryan used optogenetics on mouse brain cells that were active when a fear memory was formed, then administered a protein-inhibiting drug to prevent them from being consolidated in the brain. When the animals were placed back in the environment that had caused the fear memory, they behaved as though nothing negative had happened. They were amnesic. However, when Tomas optogenetically reactivated the brain cells – using our laser technique – that had processed the fear memory, the animals immediately froze. He was able to artificially bring a memory back, awakening a dormant memory that we thought was forever lost. This experiment demonstrated that as long as we have access to the cells that processed the memory in the first place, then we have a target for retrieving it. Again, headlines were sparked around the world in 2015: ‘Neuroscientists reactivate “lost” memories in mice,’ ‘Amnesia patients could recover their lost memory,’ ‘Bringing memories back from the dead: science, not fiction’. Other discoveries have been equally as exciting. A few years after Tomas’s study, Paul Frankland and his lab at the University of Toronto published a groundbreaking paper that asked whether memories formed in infancy were lost for ever. Using our optogenetics technique, they stimulated the brain cells of mice containing hidden infant memories – and reawakened them when they were adults. One of the researchers involved later told me over coffee that ‘the finding that the engrams still exist in the brain in a “silent” state might explain how these forgotten memories continue to influence our thoughts and behaviours as adults’. Earlier in 2013, I also managed to successfully achieve our ‘dream’ experiment: warping memories, by successfully implanting a false memory in a mouse. And the University of Toronto team even conducted research that led to a mind-blowingly provocative finding from a paper aptly titled, ‘Memory formation in the absence of experience’. They were able to write a memory from within the brain without the animal having ever experienced the event. So what does all this mean for us humans? Well, our brains are pretty similar to mice brains, built from the same pieces – i.e., brain cells – and sharing similar structures, like the cortex and hippocampus. And so I believe that if a researcher can edit memories in the mouse brain in a lab, we should reasonably expect that our work will one day inspire future inventions and methods for targeting memories in the human brain. Today, the theory behind memory manipulation science can already be implemented to a degree on humans. Memories can be both weakened and strengthened by stimulating the human brain itself. Transcranial direct current stimulation (tDCS), for instance, is an approach in which mild electrical stimulation is delivered through the scalp – whereas deep brain stimulation (DBS) is a more invasive approach in which electrodes implanted in the brain deliver small amounts of electricity. Both are promising approaches for creating new memory ‘treatments’ in a clinical setting and have been proven in experiments to disrupt or enhance our memories of facts and events. For example, one influential study in the journal Neuroimage in 2014 found that stimulating brain areas near the hippocampus while a human subject learned the locations of various landmarks enhanced their spatial memory, meaning they were able to navigate to the landmarks faster on subsequent tests than they were before the stimulation. Crucially, going forward, it’s key that we use less-invasive approaches more tailored to improving the patient’s quality of life. Of course, memory manipulation and ethical dilemmas surely go hand-in-hand, and the goal is to prevent the misuse of memory manipulation, while also planning how we intervene if it falls into the wrong hands. As the technology develops we will need a carefully thought-through legal and social infrastructure to prevent such exploitation from happening. Our work in this field goes on: we are just in the foothills of a revolution in memory research. One day, we will get to the summit. HOW TO HELP YOUR BRAIN COPE WITH GRIEF When my grandmother died, my dad taught me those we lose rest in our mental memorial permanently. ‘When you remember someone, you reconnect with them,’ he told me. His insight wasn’t scientific, just his emotional sense of how the world worked. But it turns out there is a neuroscientific basis for this. For there is a physical site in your brain, where your lost loved one will always reside. The brain goes out of its way to make sure it physically holds onto memories of people that matter. In mammals, for instance, more brain cells become active when a social bond is made compared to when a non-social event is experienced. This increase in neural activity can even predict the strength of the bond itself. A sombre prediction is that a partner’s passing will leave this exact pattern of cellular activity quiet for the rest of a person’s life. The cells that breathe life into the memories of a partner continue to exist, even when that partner does not. But this brings a new biological challenge. The brain cells holding onto these memories are only fully engaged by the physical presence of the individual they’re holding onto. When that individual passes away, everything our brain thought was certain is no longer certain. It has to process your loved one’s permanent absence. Initially, the brain delivers jolts of stress hormones when a bond is broken in some way, such as when someone goes missing – while we know they are no longer there, this violation of our expectations puts our brain into this search mode as we hunt for some kind of answer to how they can no longer be here. This perpetuates the feeling of loss. But just as memories are updated, little by little, it takes multiple experiences with someone’s absence to fully accept the reality of their passing. Finding the positive meaning of memories can help. A particularly relevant study in 2021 found that after losing a loved one, individuals benefited from recalling memories if they did so in ways that had ‘positive self functions’. An example of this is thinking ‘I miss my Dad so much… but he helped me become the good person I am.’ Or ‘I’ve lost my husband, but that’s to be expected because one day I will die too and that’s natural.’ I believe that loss happens when all of the building blocks of memory topple over – and the reverse process is where healing begins. Adapted from How To Change A Memory by Steve Ramirez (Robinson, £16.99), to be published November 6. © Steve Ramirez 2025. To order a copy for £15.29 (offer valid to 11/11/25; UK P&P free on offers over £25) go to mailshop.co.uk, or call 020 3176 2937.
প্রকাশিত: 2025-10-28 07:00:00
উৎস: www.dailymail.co.uk
