Memory erasure is the selective artificial removal of memories or associations from the mind.
Memory erasure has been shown to be possible in some experimental conditions; some of the techniques currently being investigated are: drug-induced amnesia, selective memory suppression, destruction of neurons, interruption of memory, reconsolidation, [1] and the disruption of specific molecular mechanisms. [2]
There are many reasons that research is being done on the selective removal of memories. Potential patients for this research include patients with psychiatric disorders such as post traumatic stress disorder, or substance use disorder, among others. [2]
Memory erasure is also featured in numerous works of fiction, with fictional methods and properties that do not necessarily correspond with scientific reality.
Research focused on gaining a better understanding of what memories are has been going on for many years, in this way so has research in memory erasure. The basis for the recent history for memory erasure has been focused on determining how the brain actively keeps memories stored and retrieves them. There have been several instances where researchers found drugs that when applied to certain areas of the brain, usually the amygdala, have relative success in being able to erase some memories. As early as 2009 researchers were able to trace and destroy neurons involved in supporting the specific type of memory that they were trying to erase. These neurons were targeted by using replication-defective herpes simplex virus (HSV) to increase cyclic adenosine monophosphate response element-binding protein (CREB) in them. As a result, the neurons were activated in fear memory or testing far more often in both wild-type and CREB-deficient mice. For the study, transgenic mice were used that allowed use of diphtheria toxin to preferentially target cells that were overexpressing CREB, since these were the cells more likely involved with fear memories. This caused the erasure of the target memory but allowed the mice to still form new fear memories which confirmed the cells were involved only in storing fear memories and not forming them. [3]
Aside from the biotechnology approach to studying memory, research in psychiatry on how memories work has also been going on for several years. There have been some studies that show that some behavioral therapy can erase bad memories. [4] There has been some evidence that psychodynamic therapy and other energy techniques [5] can help with forgetting memories among other psychiatric issues there is no proven therapeutic approach for trying to erase bad memories. [6]
There are several different types of possible patients that have the potential to draw great benefit from the selective memory erasure; these include people with drug addiction, or posttraumatic stress disorder (PTSD). PTSD patients may include war veterans, people who witnessed horrific events, victims of violent crimes and many other possibly traumatic events. These potential patients have unwanted memories that can be absolutely devastating to their daily lives and cause them to not be able to function properly. [7]
Research continues, and in 2020, researchers were looking at potential new approaches to PTSD treatment. [8] [9]
There are three main types of memories: sensory memory, short-term memory, and long-term memory. Sensory memory, in short, is the ability to hold sensory information for a short period of time, for example, looking at an object and being able to remember what it looked like moments after. Short-term memory is memory that allows a person to recall a short period of time; this can be a few seconds to a minute. Short-term memory allows people to remember what happened during that short time span without actually practicing the memory. Long-term memory has a much larger capacity than the prior two and actually stores information from both these types of memories to create a long lasting and large memory. Long-term memory is the largest target for research involving selective memory erasure.
Within long-term memory there are several types of retention. [10] Implicit memory (or 'muscle memory') is generally described as the ability to remember how to use objects or specific movements of the body (e.g. using a hammer). Explicit memory, (or 'declarative memory') is that which can be consciously drawn upon by a person to remember.
Explicit memory can be split into further subcategories; episodic memory, which is the memory of specific events and the information surrounding it, and semantic memory, which is the ability to remember factual information (e.g. what numbers mean). [11]
A type of memory of main concern for memory erasure are emotional memories. These memories often involve several different aspects of information in them that can come from a variety of the different categories of memories mentioned above. These emotional memories are powerful memories that can illicit strong physiological effects on a person. [12] An example of an emotional memory can be found in patients with PTSD, for these patients a traumatic event has left a lasting emotional memory that can have powerful effects on a person even without them consciously retrieving the memory. [13]
Drug-induced amnesia is the idea of selectively losing or inhibiting the creation of memories using drugs. Amnesia can be used as a treatment for patients who have experienced psychological trauma or for medical procedures where full anesthesia is not an option. Drug-induced amnesia is also a side-effect of other drugs like alcohol and rohypnol.
There are other drugs that also can cause their users to be put in an amnesic state, where they experience some type of amnesia because of their use. Examples of these drugs include Triazolam, Midazolam and Diazepam. [14]
There is a growing amount of information that has shown that memory depends largely on the brain's synaptic plasticity, with a large part of this being dependent on its ability to maintain long-term potentiation (LTP). [15] Studies on LTP have also started to indicate that there are several molecular mechanisms that may be at the basis of memory storage. [16] A more recent approach to erasing memories and the associations the brain makes with objects is disrupting specific molecular mechanisms in the brain that are actively keeping memories active. [17]
Recovering methamphetamine (METH) addicts have reported that the sight of certain objects such as a lighter, gum or drug paraphernalia can cause massive cravings that can sometimes lead to a break in their mental strength and cause them to relapse. [2] This indicates that long-term memories can be called upon by various different associations that were made with the memory without the conscious effort of the person. With an increasing belief that memories are largely supported by functional and structural plasticity deriving from F-actin polymerization in postsynaptic dendritic spines at excitatory synapses. [2] Recent research has been done to target this F-actin polymerization by using direct actin depolymerization or a myosin II inhibitor to disrupt the polymerized F-actin associated with METH memory associations. The study indicated types of associations can be disrupted days to weeks after consolidation. [2] Although the depolymerization techniques had no effect on food reward based associations or shock based associations the results demonstrate the idea that meth associated memories' actin cytoskeleton is constantly changing making it uniquely sensitive to depolymerization during the maintenance phase. This is some of the first evidence showing that memories made with different associations are actively maintained using different molecular substrates. These results also show that the actin cytoskeleton may be a promising target for selective disruption of unwanted long-term memories. [2]
Selective memory suppression is the idea that someone can consciously block an unwanted memory. Several different therapeutic techniques or training have been attempted to test this idea with varied success. [18] Many of these techniques focus on blocking the retrieval of a memory using suppression techniques to slowly teach the brain to suppress the memory. Although some of these techniques have been useful for some people it has not been shown to be a clear cut solution to forgetting memories. Because these memories are not truly erased but merely suppressed the question of how permanent the solution is and what actually happens to the memories can be troubling for some. [19]
Selective memory suppression is also something that can occur without a person being consciously aware of suppressing the creation and retrieval of unwanted memories. When this occurs without the person knowing it is usually referred to as memory inhibition; the memory itself is called a repressed memory. [20]
One of the ways scientists have attempted to erase these memories through suppression is by interrupting the reconsolidation of a memory. Memory consolidation of a memory is when a person recalls a memory, usually a fearful one, it becomes susceptible to alteration, and then gets stored again. [21] This has led many researchers to believe that this time period is the best time for memories to be altered or erased. Studies have shown that through behavioral training results showed that they were able to erase memories by tampering with memories during the reconsolidation phase. [22]
With evidence showing that different memories excite different neurons or system of neurons in the brain [23] the technique of destroying select neurons in the brain to erase specific memories is also being researched. Studies have started to investigate the possibility of using distinct toxins along with biotechnology that allows the researchers to see which areas of the brain are being used during the reward learning process of making a memory to destroy target neurons. In a paper published in 2009, authors showed that neurons in the lateral amygdala that had a higher level of cyclic adenosine monophosphate response element-binding protein (CREB) were activated primarily over other neurons by fear memory expression. This indicated to them that these neurons were directly involved in the making of the memory trace for that fear memory. They then proceeded to train mice using auditory fear training to produce a fear memory. They proceeded to check which of the neurons were overexpressing CREB and then, using an inducible diphtheria-toxin strategy, they destroyed those neurons, resulting in persistent and strong memory erasure of the fear memory. [1]
Researchers have also found that the levels of the neurotransmitter, acetylcholine, can also effect which memories are most prominent in our minds. [24]
Due to the lack of understanding of the brain this technique of destroying neurons may have a much larger effect on the patient than just the removal of the intended memories. Due to this complex nature of the brain treatment that would stun the neurons instead of destroying them could be another approach that could be taken. [25]
A way of selectively erasing memories may be possible through optogenetics, a type of gene therapy that targets specific neurons. In 2017, researchers at Stanford demonstrated a technique for observing hundreds of neurons firing in the brain of a live mouse, in real time, and have linked that activity to long-term information storage. By using a virus to trigger production of a light-sensitive protein in neurons linked to a fear, they could erase the memory by weakening the pathways using light. [26] [27]
There is an epistemological issue in determining whether the absence of evidence (i.e., memory trace) is evidence of absence. In experimental studies, the absence of behavior indicative of memory is sometimes interpreted as the absence of the memory trace; however, the memory impairment may be temporary due to deficits in recall. [28] Alternatively, the memory trace be latent and demonstrable via its indirect effects on new learning. [29] [30] The measurement issue is compounded by the fact that memory processes are dynamic and may not always manifest in single locations or in static and easily identifiable changes detectable by current technologies.
Michael Davis, researcher at Emory University, argues that complete erasure can only be confidently concluded if all of the biological events that occurred when the memory was formed revert to their original status. [31] The current state of technology and methodology may not be sensitive enough to detect all types of memory traces. Davis contends that because making these measurements in a complex organism is implausible, the concept of complete memory erasure (what he deems "strong form of forgetting") is not useful scientifically. [31]
As with most new technologies the idea of being able to erase memories comes with many ethical questions. One ethical question that arises is the idea that although there are some extremely painful memories that some people (for example PTSD patients) would like to be rid of, not all unpleasant memories are bad. [7] The ability to soften or erase memories could have drastic effects on how society functions. The ability to remember unpleasant effects from one's past has a huge impact on the future actions they may take. Remembering and learning from past mistakes is crucial in the emotional development of a person and helps to ensure they do not repeat previous errors. [32] The ability to erase memory could also have a massive impact on the law. When it comes to determining the outcome of a trial, the ability to modify memory could have a massive impact on the judicial system. Another ethical question that arises is to how the government will use this technology and what restrictions would need to be put in place. Some worry that if soldiers can go into battle knowing that the memories created during that time period can simply be erased they may not uphold military morale and standards. [7] Many are also skeptical with who should be able to have procedures done on them, so they are urging for a set of laws to determine this.
Memory erasure has also been a common topic of interest in science fiction and other fiction. Several notable comics, TV shows and movies feature mindwipes, including Telefon , Total Recall , Men in Black , Eternal Sunshine of the Spotless Mind , Black Mirror , Futurama , The Bourne Identity , NBC's Heroes and Dollhouse . [33] Novels that feature memory erasure include The Invincible by Stanisław Lem, some of the Harry Potter novels (including Harry Potter and the Chamber of Secrets ) by J. K. Rowling, and The Giver by Lois Lowry. Several works by Philip K. Dick are about mindwipes, including "Paycheck", "We Can Remember It for You Wholesale" (which served as the inspiration for Total Recall).
Long-term memory (LTM) is the stage of the Atkinson–Shiffrin memory model in which informative knowledge is held indefinitely. It is defined in contrast to sensory memory, the initial stage, and short-term or working memory, the second stage, which persists for about 18 to 30 seconds. LTM is grouped into two categories known as explicit memory and implicit memory. Explicit memory is broken down into episodic and semantic memory, while implicit memory includes procedural memory and emotional conditioning.
In neurology, anterograde amnesia is the inability to create new memories after an event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. This is in contrast to retrograde amnesia, where memories created prior to the event are lost while new memories can still be created. Both can occur together in the same patient. To a large degree, anterograde amnesia remains a mysterious ailment because the precise mechanism of storing memories is not yet well understood, although it is known that the regions of the brain involved are certain sites in the temporal cortex, especially in the hippocampus and nearby subcortical regions.
In neurology, retrograde amnesia (RA) is the inability to access memories or information from before an injury or disease occurred. RA differs from a similar condition called anterograde amnesia (AA), which is the inability to form new memories following injury or disease onset. Although an individual can have both RA and AA at the same time, RA can also occur on its own; this 'pure' form of RA can be further divided into three types: focal, isolated, and pure RA. RA negatively affects an individual's episodic, autobiographical, and declarative memory, but they can still form new memories because RA leaves procedural memory intact. Depending on its severity, RA can result in either temporally graded or more permanent memory loss. However, memory loss usually follows Ribot's law, which states that individuals are more likely to lose recent memories than older memories. Diagnosing RA generally requires using an Autobiographical Memory Interview (AMI) and observing brain structure through magnetic resonance imaging (MRI), a computed tomography scan (CT), or electroencephalography (EEG).
Lacunar amnesia is the loss of memory about a specific event. This specific form of amnesia is caused by brain damage in the limbic system which is responsible for our memories and emotions. When the damage occurs it leaves a lacuna, or a gap, in the record of memory within the cortex region of the brain. There is a general belief that certain emotions from the lost memory may be triggered without the recollection of the event.
Neuropharmacology is the study of how drugs affect function in the nervous system, and the neural mechanisms through which they influence behavior. There are two main branches of neuropharmacology: behavioral and molecular. Behavioral neuropharmacology focuses on the study of how drugs affect human behavior (neuropsychopharmacology), including the study of how drug dependence and addiction affect the human brain. Molecular neuropharmacology involves the study of neurons and their neurochemical interactions, with the overall goal of developing drugs that have beneficial effects on neurological function. Both of these fields are closely connected, since both are concerned with the interactions of neurotransmitters, neuropeptides, neurohormones, neuromodulators, enzymes, second messengers, co-transporters, ion channels, and receptor proteins in the central and peripheral nervous systems. Studying these interactions, researchers are developing drugs to treat many different neurological disorders, including pain, neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease, psychological disorders, addiction, and many others.
A flashback, or involuntary recurrent memory, is a psychological phenomenon in which an individual has a sudden, usually powerful, re-experiencing of a past experience or elements of a past experience. These experiences can be frightful, happy, sad, exciting, or any number of other emotions. The term is used particularly when the memory is recalled involuntarily, especially when it is so intense that the person "relives" the experience, and is unable to fully recognize it as memory of a past experience and not something that is happening in "real time".
Joseph E. LeDoux is an American neuroscientist whose research is primarily focused on survival circuits, including their impacts on emotions such as fear and anxiety. LeDoux is the Henry and Lucy Moses Professor of Science at New York University, and director of the Emotional Brain Institute, a collaboration between NYU and New York State with research sites at NYU and the Nathan Kline Institute for Psychiatric Research in Orangeburg, New York. He is also the lead singer and songwriter in the band The Amygdaloids.
Dominique de Quervain is a Swiss neuroscientist. He is professor of neuroscience and director of the Division of Cognitive Neuroscience at the University of Basel, Switzerland. He is known for his pioneering research into the use of glucocorticoids (cortisol) in the treatment of PTSD and phobias. He is understood to have found a link between cortisol and forgetting, specifically that cortisol can inhibit memory retrieval. Furthermore, he is known for his contributions to the field of genetics of human memory.
Memory consolidation is a category of processes that stabilize a memory trace after its initial acquisition. A memory trace is a change in the nervous system caused by memorizing something. Consolidation is distinguished into two specific processes. The first, synaptic consolidation, which is thought to correspond to late-phase long-term potentiation, occurs on a small scale in the synaptic connections and neural circuits within the first few hours after learning. The second process is systems consolidation, occurring on a much larger scale in the brain, rendering hippocampus-dependent memories independent of the hippocampus over a period of weeks to years. Recently, a third process has become the focus of research, reconsolidation, in which previously consolidated memories can be made labile again through reactivation of the memory trace.
The neuroanatomy of memory encompasses a wide variety of anatomical structures in the brain.
Amnesia is a deficit in memory caused by brain damage or brain diseases, but it can also be temporarily caused by the use of various sedative and hypnotic drugs. The memory can be either wholly or partially lost due to the extent of damage that is caused.
The cellular transcription factor CREB helps learning and the stabilization and retrieval of fear-based, long-term memories. This is done mainly through its expression in the hippocampus and the amygdala. Studies supporting the role of CREB in cognition include those that knock out the gene, reduce its expression, or overexpress it.
Drug-induced amnesia is amnesia caused by drugs. Amnesia may be therapeutic for medical treatment or for medical procedures, or it may be a side-effect of a drug, such as alcohol, or certain medications for psychiatric disorders, such as benzodiazepines. It is seen also with slow acting parenteral general anaesthetics.
The management of traumatic memories is important when treating mental health disorders such as post traumatic stress disorder. Traumatic memories can cause life problems even to individuals who do not meet the diagnostic criteria for a mental health disorder. They result from traumatic experiences, including natural disasters such as earthquakes and tsunamis; violent events such as kidnapping, terrorist attacks, war, domestic abuse and rape. Traumatic memories are naturally stressful in nature and emotionally overwhelm people's existing coping mechanisms.
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, it would be impossible for language, relationships, or personal identity to develop. Memory loss is usually described as forgetfulness or amnesia.
Memory allocation is a process that determines which specific synapses and neurons in a neural network will store a given memory. Although multiple neurons can receive a stimulus, only a subset of the neurons will induce the necessary plasticity for memory encoding. The selection of this subset of neurons is termed neuronal allocation. Similarly, multiple synapses can be activated by a given set of inputs, but specific mechanisms determine which synapses actually go on to encode the memory, and this process is referred to as synaptic allocation. Memory allocation was first discovered in the lateral amygdala by Sheena Josselyn and colleagues in Alcino J. Silva's laboratory.
Daniela Schiller is a neuroscientist who leads the Affective Neuroscience Lab at the Mount Sinai School of Medicine. She is best known for her work on memory reconsolidation, and on modification of emotional learning and memory.
The hippocampus participates in the encoding, consolidation, and retrieval of memories. The hippocampus is located in the medial temporal lobe (subcortical), and is an infolding of the medial temporal cortex. The hippocampus plays an important role in the transfer of information from short-term memory to long-term memory during encoding and retrieval stages. These stages do not need to occur successively, but are, as studies seem to indicate, and they are broadly divided in the neuronal mechanisms that they require or even in the hippocampal areas that they seem to activate. According to Gazzaniga, "encoding is the processing of incoming information that creates memory traces to be stored." There are two steps to the encoding process: "acquisition" and "consolidation". During the acquisition process, stimuli are committed to short term memory. Then, consolidation is where the hippocampus along with other cortical structures stabilize an object within long term memory, which strengthens over time, and is a process for which a number of theories have arisen to explain the underlying mechanism. After encoding, the hippocampus is capable of going through the retrieval process. The retrieval process consists of accessing stored information; this allows learned behaviors to experience conscious depiction and execution. Encoding and retrieval are both affected by neurodegenerative and anxiety disorders and epilepsy.
Sheena Josselyn is a Canadian neuroscientist and a full professor of psychology and physiology at Hospital for Sick Children and The University of Toronto. Josselyn studies the neural basis of memory, specifically how the brain forms and stores memories in rodent models. She has made critical contributions to the field of Neuronal Memory Allocation and the study of engrams.
Courtney A. Miller is an American neuroscientist and Professor of the Department of Molecular Medicine at the Scripps Research Institute in Jupiter, Florida. Miller investigates the biological basis of neurological and neuropsychiatric diseases and develops novel therapeutics based on her mechanistic discoveries.
Does the amnestic agent block consolidation, or now reconsolidation, or impair retrieval? Is the memory deficit permanent or is there spontaneous recovery or the possibility of recovering the memory by further treatments or reminders? It is evident that the same logical objection voiced by Weiskrantz (1966)...He warned that experimental amnesia studies are fatally flawed from the outset, since it is not possible to prove the null hypothesis, i.e. the absence of a memory trace.