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EVAWI > Resources > Best Practices > FAQs > Neurobiology of Trauma
Q Can someone be sexually assaulted, without actually experiencing fear?
Q We work with survivors whose first response is to fight. How does this fit with the idea that we evolved to freeze first, and then flee if possible?
Q Could you explain the "continuum" of tonic immobility, and/or the differences between tonic immobility and collapsed immobility?
Q Before my current job as a prosecutor, I represented a victim of sexual assault who was charged with falsely reporting because she could not identify the perpetrator and went into a state of tonic immobility as a result of a prior assault. Very sad that the prosecutor who worked in sexual assault did this. How well known is this science now?
Q How does the prefrontal cortex relate to victims fainting due to fear?
Q What's the difference between an explicit and episodic memory? What are the implications for people who have experienced trauma, such as sexual assault victims?
Q I have vaguely heard reference to a person who has been traumatized needing two full sleep cycles before the prefrontal cortex returns to near normal functioning after trauma. Any information on that? To elaborate, it may support the recall of information over time.
Q Is there research documenting fear responses when alcohol is involved?
Q What are the effects of high levels of intoxication, not just low/moderate?
Q I see patients who have experienced Drug Facilitated Sexual Assault (DFSA). In the acute period, when I am providing them care, they can recall very few, if any, memories of the assault. Will these patients experience some memory retrieval in the days following?
Q Can you talk about how this research applies to different populations of survivors, like male survivors and trans folks? Who were the subjects involved in this research?
Q Has there been any research on similarities/differences with what is going on in the brains of perpetrators during a sexual assault and a physical assault (e.g., during intimate partner violence)?
Q What are the implications of repeated assaults? For example, incest throughout childhood? How are the dynamics similar or different to sexual assaults perpetrated against adolescents or adults?
Q If abuse, especially early childhood, is repetitive and persistent can the executive function be developed and/or healed?
Q Can you explain strengthening and weakening of memories more? How can one strengthen/ weaken encoding of a memory that isn't there to begin with?
Q I've read that if a victim feels a police officer is "unsafe" during the initial report, that this can impair the prefrontal cortex again. Could you speak to this?
A The following responses were written by Dr. Jim Hopper, Clinical Psychologist, Independent Consultant and Teaching Associate in Psychology, Harvard Medical School.

Can someone be sexually assaulted, without actually experiencing fear?

Dr. Jim Hopper: If “fear” refers to the subjective experience of being afraid, one can be conscious of being assaulted (i.e., not passed out) but not experience fear. That’s the main way that dissociation, a relatively common and automatic survival reflex, protects people in the midst of traumatic and horrible experiences like sexual assault. Dissociation is a way of escaping mentally when physical escape is (or is appraised as) impossible or likely to get one killed or seriously physically injured.

In this training material, the “defense circuitry” is described as a circuitry of the brain that:

  1. Continually scans the external and internal world, automatically and outside of awareness, for threats and danger, even hints that danger could be near or imminent, and;
  2. When it detects possible or actual danger, let alone undeniable attack, automatically and immediately implements survival reflexes and/or self-protective habits, along with a variety of physiological changes in the brain and body.

That circuitry has been known as the “fear circuitry” for decades, even though it can (a) trigger states of dissociation in which fear is not subjectively experienced and (b) continue functioning in the absence of such experiential fear.

Recently some researchers, notably the influential neuroscientist Joseph LeDoux, who has devoted his career to studying what he himself long referred to as the “fear circuitry,” have for good reasons advocated restricting using “fear circuitry” to refer to the circuitry responsible for fearful subjective mental states and using “defense circuits” or “defense circuitry” to refer to the mostly subcortical circuitry, including the amygdala, that detects and responds to threats and attacks, including with defensive behaviors and physiological adjustments that promote survival of predatory attack (LeDoux & Pine, 2016).1  In line with this development, I have now begun using the term “defense circuitry,” to describe these functions, and their impacts on the brain, experience, and behavior – which do not necessarily include mental states of “fear.” However, videos and webinars and writings of mine are still available that use the term “fear circuitry,” and what I say in them is still valid. The viewer or reader just needs to know that “fear circuitry” is interchangeable with “defense circuitry.”


1 See LeDoux, J. & Pine, D. (2016). Using neuroscience to help understand fear and anxiety: A two system framework, American Journal of Psychiatry, 173, 1083-1093.

A We work with survivors whose first response is to fight. How does this fit with the idea that we evolved to freeze first, and then flee if possible?

Dr. Jim Hopper: Some people’s very early response is to fight, and that’s a response that’s expected by most people, based on our cultural myths and misconceptions regarding sexual assault. However, even when it seems a person’s first response was to fight, it may not have been. That is, in many such cases there’s some kind of very brief appraisal of the attack/assault and perhaps a brief freeze response before the brain goes into fight mode. However, some people do reflexively strike out within a fraction of a second after being touched in a way they don’t want, or simply being touched unexpectedly.

This training material is focused on brain-based responses that are (a) quite common in sexual assault victims and (b) still not understood as brain-based by most victims, investigators and everyone else. Those brain-based responses include the defense circuitry taking over; the prefrontal cortex becoming impaired; alterations of attentional deployment; reflexive responses including freezing, dissociation, tonic immobility and collapsed immobility; and habit-based responses associated with responses to aggressive or dominant people, prior victimization (e.g., child abuse, witnessing domestic violence, bullying), and socialization in how to respond to unwanted sexual advances).

A Could you explain the "continuum" of tonic immobility, and/or the differences between tonic immobility and collapsed immobility?

Dr. Jim Hopper: By referring to the “continuum of tonic immobility,” I just mean that it’s not always an all-or-nothing state. Some victims report being able to move one or two parts of their bodies (e.g., one hand but not the other, or both hands but not arms) to some extent, but not the rest of their body.

Sometimes victims report slowly emerging from tonic immobility, although the state typically ends very suddenly, as we see in this video involving a dog. The differences between tonic and collapsed immobility are addressed in this training material. However, I can summarize it here. In tonic immobility the body is rigid, and the person may or may not be dissociated, but the person will not typically become faint or lose consciousness. In collapsed immobility, the body becomes limp, and due to dramatic decreases in blood pressure and heart rate, the brain receives less oxygenated blood. As a result, the person becomes faint and may even pass out. Then, given the oxygen deprivation issues, emergence from collapsed immobility is always more gradual.

For much more detailed information on tonic and collapsed immobility, please see the excellent review article by Kozlowska et al. (2015).2


2 For much more detailed information on tonic and collapsed immobility, please see the excellent review article by Kozlowska, K., et al. (2015). Fear and the defense cascade: Clinical implications and management. Harvard Review of Psychiatry, 23, 263-287.

A Before my current job as a prosecutor, I represented a victim of sexual assault who was charged with falsely reporting because she could not identify the perpetrator and went into a state of tonic immobility as a result of a prior assault. Very sad that the prosecutor who worked in sexual assault did this. How well known is this science now?

Dr. Jim Hopper: Unfortunately, this science is still not known by most police officers, prosecutors, judges, Title IX officers, university administrators, military commanders, judges, legislators, etc. It’s also not understood by most of the writers, directors and actors of television shows and films featuring sexual assault. It’s certainly not known by the general public. Even many therapists and victim advocates who work with sexual assault victims don’t know much about this science.

There has been no survey research to quantify the percentages of people in various professions and the general public who know about this science, but as someone who teaches about it all the time, I would estimate that it’s very low (below 5%) both in the general population and among law enforcement professionals who investigate sexual assaults. It may be highest among victim advocates and others whose work is focused on supporting sexual assault victims. Even then, I’m only referring to the percentage of people who understand general notions, for example that sexual assault (a) triggers massive activation of the brain’s defense circuitry which results in (b) impairment of the prefrontal cortex, (c) alterations of memory encoding, and (d) the activation of reflexive responses including fight, flight and “freeze.” In addition, many people still remain confused about what “freeze” means, and wrongly lump together what scientists refer to as “freeze” with tonic immobility and collapsed immobility, which are very different brain and body reactions.

What is still known by very few (in any profession) is the more specific and nuanced knowledge, such as:

  1. The distinction between freezing as it’s actually understood by scientists (i.e., an initial and transient response associated with detection and rapid appraisal of the threat/attack and potentials for escape) and the very different responses of tonic immobility and collapsed immobility;
  2. The clarification that habit behaviors are common and commonly misunderstood brain-based responses associated with defense-circuitry domination; and
  3. The fact that stress, fear, and trauma do not simply impair the functioning of the hippocampus and the encoding of episodic memories, but rather typically do so in a time-dependent way such that detection of assault/attack briefly shifts the hippocampus into a super-encoding mode which is then followed by a “refractory period” in which encoding of new information, especially more complex contextual and time-sequence information, is impaired (Diamond et al., 2007; Zoladz et al., 2014).3

3 On the latter point, see also Diamond, D. et al. (2007). The temporal dynamics model of emotional memory processing: A synthesis on the neurobiological basis of stress-induced amnesia, flashbulb and traumatic memories, and the Yerkes-Dodson Law. Neural Plasticity, 60803; and Zoladz, P. et al. (2014). Amygdala-induced modulation of cognitive brain structures underlies stress-induced alterations of learning: Importance of stressor timing and sex differences. In A. Costa & E. Villalba (Ed.), Horizons in Neuroscience Research (Vol. 14), pp. 1-40. Hauppauge, NY: Nova Science Publishers.

A How does the prefrontal cortex relate to victims fainting due to fear?

Dr. Jim Hopper: When a person faints due to fear (in a state of collapsed immobility), the prefrontal cortex (along with the rest of the brain) is not receiving sufficient oxygenated blood to function in that nonconscious state. In addition, because of global brain impairment due to oxygen deprivation, the prefrontal cortex is not receiving sensory information to process, let alone engaging in reasoning or other executive functions.

A What's the difference between an explicit and episodic memory? What are the implications for people who have experienced trauma, such as sexual assault victims?

Dr. Jim Hopper: Episodic memories are a type of explicit memory. Explicit memories are memories that we realize are memories, and they can be either episodic or semantic in nature.

Episodic memories are memories of experiences or “episodes” from our lives, and these are explicit memories because when we recall them, we recognize them as (our) memories. Episodic memories include the specific images, sounds, smells, and any other sensations or thoughts that we experienced during the event or “episode,” and when they come into awareness, we realize that they are memories of things we have previously experienced.

Semantic memories are memories of ideas and concepts that do not consist of personal experience (i.e., episodic memories), although they may be partly based on them. For example, we can remember that Washington, DC is the nation’s capital, and when we remember that, we can realize that we’re having a memory, that is, recalling information. But it consists of abstract information, not memories of an episode of experience.

Implicit memories, in contrast, are memories that one does not recognize as memories. With respect to traumatic experiences such as sexual assault, implicit memories tend to be physiological and behavioral reactions (which are not recognized as memories), and that are triggered by reminders of the trauma (which are also not recognized as reminders). For example, a woman who is sexually assaulted by a man with a thick mustache might pass a man with a thick mustache while walking down the street, perceive that mustache in her peripheral vision without realizing that she’s seen it, then suddenly find herself feeling panicked and afraid. She doesn’t think to herself, “I just saw a guy with a mustache like the mustache of the guy who sexually assaulted me,” or even, “I’m remembering the fear I experienced when I was sexually assaulted.” Instead, her brain has reacted automatically, without having any conscious understanding of why, and she remembers aspects of the assault implicitly, that is, without realizing that’s what’s happening.

Or a man who was sexually assaulted by a group of other men might find himself overcome with horror and dread on a crowded bus with lots of other men on it, but he may not realize that he’s feeling and remembering the horror and dread he experienced at that terrible moment when he realized the group of men who assaulted him were actually going to carry out the threats they’d been making. Understandably, these kinds of implicit-memory based experiences can be very confusing and disturbing, and lead people to feel “crazy” because their bodies and emotions feel out of control and they don’t realize that it’s a normal, brain-based response to trauma.

A I have vaguely heard reference to a person who has been traumatized needing two full sleep cycles before the prefrontal cortex returns to near normal functioning after trauma. Any information on that? To elaborate, it may support the recall of information over time.

Dr. Jim Hopper: Two full sleep cycles may be necessary for the episodic memory circuitry to consolidate (that is, store into a retrievable state) information that was encoded at the time of a sexual assault (or other trauma). Researchers have found that processes occurring during both rapid eye movement (REM) and non-rapid eye movement (NREM) sleep play critical roles in the consolidation of memories.

However, the issue here is the episodic memory circuitry, not the prefrontal cortex. The impairment of prefrontal cortex function associated with states of extreme stress, fear, and trauma resolves when stress and fear are reduced – which may not require sleep. Indeed, when the victim receives compassionate care from family, friends, and responding professionals, prefrontal cortex function could return to normal levels within an hour or so after an assault. Also, a sexual assault victim could have two very restful nights of sleep but then, upon encountering trauma-related triggers (e.g., an investigator who, by failing to empower and connect with the victim, triggers trauma-related states more than the investigation would otherwise) suffer prefrontal cortex impairment greater than any experienced since the assault itself.

A Is there research documenting fear responses when alcohol is involved?

Dr. Jim Hopper: There are decades of research on how alcohol (aka ethanol or ethyl alcohol) inhibits or decreases activity in the brain circuitries of fear and anxiety – particularly via its effect on receptors for gamma-Aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system. Indeed, that’s one of the main reasons why people drink: to feel less socially afraid and anxious, to “loosen up.” While the research literature on alcohol’s fear- and anxiety-reducing effects has had various methodological limitations (Eckardt et al., 1998),4 more rigorous and recent studies in animals and humans have established the reality of these effects and clarified their brain bases (Bjork & Gilman, 2014; Nie et al., 2004).5


4 See Eckardt, M., et al. (1998). Effects of moderate alcohol consumption on the central nervous system. Alcoholism: Clinical and Experimental Research, 22, 998-1040.

5 For example, see Nie, Z. et al. (2004). Ethanol augments GABAergic transmission in central amygdala via CRF1 receptors. Science, 303 (5663), 1512-1514; Bjork, J. & Gilman, J. (2014). The effects of acute alcohol administration on the human brain: Insights from neuroimaging, Neuropharmacology, 84, 101-110.

A What are the effects of high levels of intoxication, not just low/moderate?

Dr. Jim Hopper: High levels of intoxication are associated with much greater impairment across all brain circuitries. Not only is the prefrontal cortex impaired, but so is the defense circuitry and the brain’s capacity to access and implement (a) survival reflexes programmed into the brain by evolution and (b) habit responses programmed by childhood experiences and cultural conditioning. Even at high levels of intoxication, however, there are differences between blackout states, where reflex and habit responses may be relatively intact but the person will have no way of recalling them later, and passed out states, where the brain and body are simply nonresponsive to what’s happening as part of the assault. (In blackout states, however, there may be brief “breakthroughs” of awareness and memory encoding associated with intense pain, fear, and/or horror.)

A I see patients who have experienced Drug Facilitated Sexual Assault (DFSA). In the acute period, when I am providing them care, they can recall very few, if any, memories of the assault. Will these patients experience some memory retrieval in the days following?

Dr. Jim Hopper: That depends on what, if anything, was encoded during the assault. If information was not encoded in the first place, then it can’t be consolidated either, and, therefore, it can never be retrieved. That is, it’s literally “not in there” to be accessed and retrieved. However, keep in mind the distinction between explicit and implicit memories, and that implicit memories can be encoded and consolidated even when no explicit memories are.

Also, if the person was not rendered completely unconscious during the entire assault, it is possible that there may be fragments of memory (for example associated with brief periods of “coming to” in response to particularly painful, terrifying or horrifying things being done to one’s body) that do manage to receive awareness, attention and episodic-memory encoding during the assault. But even those “breakthrough” fragments may be consolidated and available for retrieval after a day or two. And even then, retrieval of newly consolidated information may depend on encountering the right “retrieval cue” (e.g., a particular interview question or reminder encountered in the environment) and/or the right “retrieval context” (e.g., a particular kind of room or bodily state).

In short, keep in mind the distinction between implicit and explicit memory, and understand that some information may never have been encoded, that consolidation can take a few days, and that consolidated information will only be retrieved with the right retrieval cues and contexts.

A Can you talk about how this research applies to different populations of survivors, like male survivors and trans folks? Who were the subjects involved in this research?

Dr. Jim Hopper: The brain-based reactions that people have during sexual assault have been “baked into” human brains by millions of years of evolution and are basically the same for all people, whatever their sex, gender, race or ethnicity. There is some evidence for differences between men and women, based on hormone levels that may vary with the phase of the menstrual cycle. However, the evidence for such differences is limited, and the similarities between men and women are greater than any differences. Furthermore, any such differences tend to be a matter of degree (and/or the probability of having a particular response), rather than completely different categories of responses. It is also worth noting that the ways these basic responses are expressed, in physiology and behaviors, may be influenced by:

  1. Specific genes or combinations of genes, which may differ between biological siblings;
  2. How gene expression is shaped by environmental factors, including by stress and trauma during development and by social and cultural factors associated with race, class, sex, and gender identity, and;
  3. In some cases, by habits of behavior (including verbal behavior) shaped by familial and various other social and cultural factors.

This training material focuses on brain-based responses that are (a) quite common in sexual assault victims and (b) still not understood as brain-based by most victims, investigators and everyone else. Of course there are many different responses people can have during a sexual assault, and not all of them are associated with massive impairments in prefrontal cortex functioning or are purely based on habits and reflexes (although the more stressed, afraid, and overwhelmed the person is, the more that will be the case).

Some sexual assaults take place over substantial periods of time, over hours or even days. During such long-lasting sexual assaults (and even in those lasting a shorter period of time), people may have varying levels of defense circuitry domination and prefrontal cortex function, resulting in varying potentials to respond based on reasoning, deliberate choices, etc. Also, social and cultural conditioning (for example, associated with sex and gender identity) can determine which habits are accessed while the defense circuitry is in control. Thus some men and women from certain families or communities may be much more likely to engage in verbally or physically aggressive responses, even when they lack prefrontal cortex function.

Genetics also play a role, in ways associated with being biologically/genetically male or female, and in ways that are unrelated to biological sex. For example, tendencies to dissociate or enter into tonic immobility appear to be partly genetically based. There is also some evidence that collapsed immobility is more likely in some people than others due to genetic factors, and that those genetic factors are more prevalent in women than men. Interestingly, these factors are associated with blood and needle phobias, and passing out in situations involving blood or needles.

Finally, in response to the question of who were the subjects in this research, my training materials draw on research from thousands of studies involving many different species of animals, from birds and fish to mammals; studies of many different mammalian species, from rats and rabbits to primates and humans; and studies of male and female humans. I am not aware of differences in brain-based responses to predatory attack or sexual assault as a function of race, ethnicity, gender, sexual identity or sexual orientation. As noted above, the brain-based responses on which the presentation focused have been selected by millions, even hundreds of millions of years of evolution, and the fundamental realities described in this training material – including defense-circuitry control, prefrontal cortex impairment, and responses based on reflexes and habits – will be preserved across all kinds of other differences between people.

A Has there been any research on similarities/differences with what is going on in the brains of perpetrators during a sexual assault and a physical assault (e.g., during intimate partner violence)?

Dr. Jim Hopper: Regardless of whether we are talking about physical abuse or sexual assault, if the perpetrator is extremely stressed, angry or enraged, then there will be impairment of the prefrontal cortex (thus of executive functions including reasoning, monitoring one’s behavior, controlling impulses, etc.) and the perpetrator will be acting on habits and impulses. In that case, the habits and impulses will be those associated with aggression, violence and domination (as opposed to the victim’s self-protective habits and survival reflexes). But not all perpetrators are angry or even particularly stressed when they engage in violence. For some, the violence is mostly or exclusively instrumental, that is, a way to manipulate and dominate their victim. Their brain may be in a state that is calm, cold, and calculating (even cruel or sadistic).

One group of researchers has categorized IPV perpetrators into “cobras” and “pit bulls,” with the cobras exhibiting decreased physiological arousal associated with calculated instrumental violence and the pit bulls inhibiting high levels of physiological arousal associated with (partly) reactive anger- or rage-fueled violence (Gottman & Jacobson, 2007).6 A pit bull engaging in violence would have activation of the defense circuitry (e.g., fear of being “disrespected,” “disobeyed,” abandoned, etc.) and activation of the circuitries associated with anger and rage (which are not entirely the same). This type of perpetrator can be largely motivated to avoid, escape and otherwise “defend” against feared states of helplessness, shame, and humiliation. Thus unlike the cobra, who may have a highly functioning prefrontal cortex focused on achieving dominance, humiliation of the victim, etc., the pit bull engaging in violence would have prefrontal cortex impairment and behavior dominated by aggressive habits and impulses.


6 Gottman, J. & Jacobson, N. (2007). When Men Batter women: New Insights into Ending Abusive Relationships. New York, NY: Simon & Schuster.

A What are the implications of repeated assaults? For example, incest throughout childhood? How are the dynamics similar or different to sexual assaults perpetrated against adolescents or adults?

Dr. Jim Hopper: First of all, like most child sexual abuse, incest tends to be associated with grooming, and grooming is designed to gradually break down the child’s resistance to sexual contact that, were it to be engaged in from the outset, would be very stressful and potentially terrifying to the child. Indeed, most perpetrators of child sexual abuse, including incest, are systematically training the child to dissociate from the inappropriate, strange, unwanted and potentially frightening behaviors, sensations, and emotions associated with such betrayal and exploitation. Thus most (but certainly not all) child sexual abuse, including incest, tends not to be associated with the states of intense fear that result in sudden defense circuitry activation and dominance of the brain. However, states of dissociation can involve impairment of the prefrontal cortex, impairment of memory encoding (primarily through altered attention e.g., imagining one is at the beach or floating on the ceiling), and “autopilot” behavior consisting entirely of habits, including habits of attention, thinking and behaving that were cultivated during the grooming process and prior incidents of abuse. These patterns could also potentially be seen in cases of repeated victimization of adolescent or adult victims.

In cases of incest throughout childhood, dissociation is very common, with the child “spacing out” and “going on autopilot” at the first indication that the abuse is about to happen again (e.g., the creak of the bedroom door or floorboards in the night). Of course, some child sexual abuse, including repeated incestuous abuse, involves states of intense fear and terror in the child (e.g., sadistic and cruel abuse by a perpetrator who deliberately inflicts emotional and physical pain and harm). In those situations, the victim may enter the states of intense fear and terror that are more common in adult sexual assault victims. However, some children (and some adult IPV victims) subjected to such chronic sadistic abuse also express their fear and distress in a dissociative autopilot way, in which they exhibit the outward behaviors of fear and terror (that the sadistic perpetrator wants to see) while subjectively feeling none of the sensations or emotions.

A If abuse, especially early childhood, is repetitive and persistent can the executive function be developed and/or healed?

Dr. Jim Hopper: It’s very important not be become attached to ideas about how abuse and assault, even when severe and chronic, can “damage” the brain. Research over the past 20 years has consistently shown that the human brain is much more resilient and capable of healing than we ever realized. The scientific term for this is “neuroplasticity,” and the therapeutic one is “resiliency.”

Yes, chronic abuse may alter brain function and structure, and it can thwart the development of certain brain capacities, including executive functions of the prefrontal cortex that partly depend on nurturing early relationships with caregivers. But brains can heal, adapt, and develop previously lacking or impaired functions, and they can develop structural and functional “work arounds” that result in the same functionality that would otherwise have developed through normal pathways. So, yes, there is a lot of potential to develop what was thwarted by chronic childhood abuse and to heal the brain.

Also, much of what may appear to be structural problems, or the absence of executive functioning capacities, can actually be better understood as problems with the “software” rather than the “hardware” of the brain. That is, we can understand patterns of particular activity and functionality “running on” human brain circuitries in ways that software apps are running on the circuitries of our computers and smartphones. Someone with very strong prefrontal cortex executive functioning, for example a military service member, police officer, or other professional may be overwhelmed by trauma-related memories and emotions in the weeks and months following a sexual assault, and appear to have impaired executive functioning. This may be especially true for those who experience unhelpful responses from family, friends, and/or responding professionals. For professionals and others (such as jurors) who didn’t know the victim before the assault, it may seem like the victim is a person who never had good prefrontal cortex capacities. But that’s often not the case. It’s just that prefrontal cortex capacities have temporarily been impaired by now-dominant patterns of activity in the emotion- and fear-processing areas of the brain – patterns of activity that can be transformed and healed by very supportive relationships, effective therapy, and/or other healthy experiences.

The same can be true for children and teenagers who have suffered chronic abuse: What may appear as thwarted and/or deficient prefrontal cortex development may simply be a persistent dominance of activity patterns in brain circuitries involved in emotion and fear, and habitual and impulsive attempts to avoid and escape trauma-related experiences. With the right relationships and other healing influences, previously dormant prefrontal cortex capacities may come to the fore and play a much greater, and more dominant, role in one’s functioning. The bottom line: Be very, very careful about assuming “brain damage” in traumatized people, let alone “permanent” damage, even in those who have endured chronic and repeated childhood abuse. Yes, it can happen, but all too often people are assuming such damage when it’s much more a matter of patterns of brain activity or “apps” running on a traumatized person’s brain.

A Can you explain strengthening and weakening of memories more? How can one strengthen/ weaken encoding of a memory that isn't there to begin with?

Dr. Jim Hopper: You cannot strengthen the encoding of a piece of memory that was not encoded in the first place. When experiences are encoded into memory, they are encoded as pieces or “memory representations” that are literally distributed around the brain. Encoding happens during and immediately after the experience, such that external and internal sensory information and thoughts are represented in particular areas of the brain as they are being processed during the experience. They are first encoded into short-term memory, which is a kind of “buffer” (like a computer’s RAM) that lasts only about 30 seconds. Visual images are encoded in occipital or visual cortex; sounds are encoded in temporal or auditory cortex; body sensations are encoded in somatosensory cortex; etc. After that initial encoding into short-term memory, the information may – or may not – be “consolidated” or stored into long-term memory.

Also, some representations are encoded into short-term memory more strongly than others. This “encoding strength” is influenced by:

  1. How much attention was given to that part of the experience (e.g., whether it was a central or peripheral detail and/or how long it was present to awareness and being encoded); and
  2. How much emotional significance it had at the time, (e.g., a victim who placed great hope on a person who came into the room and told the perpetrator to stop, only to have those hopes dashed when the perpetrator continued the assault).

However, just because a part of the experience gets encoded into memory does not mean that it will get consolidated and then be available for later retrieval. Once the hippocampus goes into the “refractory mode,” there may be new information that gets encoded into short-term memory but does not get consolidated into long-term memory. This is because hippocampal resources are devoted to consolidating information encoded right before and during the moment when the defense circuitry detected that a sexual attack was happening.

Finally, consolidation is a process that takes time. When encoded information gets “tagged” for the consolidation process (before it disappears from short-term memory), that is only the beginning of a consolidation process that involves a variety of cellular and circuitry processes. These will take place over the following minutes, hours, and days, including during sleep.

When I talk about potentially strengthening and weakening memories I am referring to a process that memory researchers refer to as “reconsolidation.” Basically, every time a collection of previously consolidated memory representations is retrieved, that collection of representations and the connections between those representations (which are “associations” that literally depend on connections between brain cells), that collection of memory representations and the connections between them (a) becomes malleable, that is, susceptible to alteration, and (b) will then undergo a “re-consolidation” process, whereby any changes, additions or subtractions to that collection of memory pieces and the connections between them is re-consolidated or stored into the brain again.

Therefore, every time someone activates and retrieves into awareness a collection of memory pieces (e.g., in response to an investigator’s question, retrieves a few images, a sound, and a couple of body sensations from a particular part of an assault), there is the potential for more – or less – fully retrieving the memory representations that were originally encoded at that moment in the assault.

There is also a potential for “sending into reconsolidation” a more or less fleshed-out array of memory representations. A poorly worded question, or a question said in an impatient tone of voice that makes a sexual assault victim feel unsafe or under interrogation, may potentially prevent them from being able to retrieve that memory into awareness. Or a particularly embarrassing piece of memory can cause a victim to remember fewer details than have actually been encoded and consolidated into memory. Even worse, this may cause a victim to reconsolidate that part of the experience without those pieces of memory that were not retrieved due to the investigator’s interviewing techniques or style. In this way, poorly conducted interviews can actually cause victims to lose pieces of their memories, because those pieces were not retrieved and thus not reconsolidated.

Going forward it will be even harder for the victim to activate and retrieve these pieces of memories into awareness, and they may become inaccessible from then on. In contrast, an investigator who uses an effective interviewing approach, with good questions and a way of relating that enables a victim to feel safe and to access many more pieces of memory, will help the victim to repeatedly retrieve and reconsolidate memories that are as complete and accurate as possible. In this way, well-conducted investigative interviews can strengthen the accuracy and accessibility of memories.

Most unfortunate is when an interviewer asks leading questions that actually inject false information into the victim’s memories. This might be done without even realizing it, if the investigator isn’t vigilant about avoiding making that mistake (as good interviewing methods teach one to do). Then, that incorrect information becomes integrated into the victim’s reconsolidated memories. In my experience as an expert witness working on sexual assault cases, including reviewing videotapes and transcripts of investigative interviews, the majority of inconsistent and inaccurate memories of sexual assault victims are created by poorly conducted investigative interviews. (However, forensic examiners, prosecutors, and well-meaning family members and friends can also ask leading questions and introduce false information into victims’ memories.)

Finally, because the original consolidation of short-term memory information into long-term memory takes time (including a couple of sleep cycles), there will always be pieces of memory – sometimes pieces critical to an investigation – that have been encoded, and have begun to be consolidated, but have not yet been sufficiently consolidated to be retrieved during an investigative interview that happens within 24 or even 48 hours of the assault. In this situation, it may only be after two or more days (and sleep cycles) that the information is available for recall, no matter how good the interviewing approach.

The information has been encoded. It’s “in there.” But it hasn’t been consolidated yet, so it’s not yet in a form that can be retrieved in response to an investigator’s questioning. Failure to understand this can result in all kinds of problems, including closing a case as unfounded based on incomplete immediate recollections; not collecting important information because the investigator didn’t conduct an interview after enough time had passed for complete consolidation to occur; questioning why the victim didn’t relay certain information during the first interview; and assuming that the victim was actually able to retrieve that information previously when that may not have been the case.

A I've read that if a victim feels a police officer is "unsafe" during the initial report, that this can impair the prefrontal cortex again. Could you speak to this?

Dr. Jim Hopper: States of high stress, and especially states of fear, are associated with prefrontal cortex impairment. Therefore, experiencing a police officer, other investigator, or anyone else as unsafe (e.g., uncaring, unbelieving, impatient, disempowering, judgmental, etc.) will generate states of stress and fear that impair prefrontal cortex functioning. In such states the victim will have difficulty paying attention to what the investigator is saying and asking, understanding questions, and engaging in “top-down” retrieval attempts that require prefrontal cortex activity. This is especially true for questions about time-sequence or anything else that requires formulating a narrative out of fragmentary memories.

Sadly, an investigator who presses a victim for a sequential narrative may be asking for information that was never encoded in the first place. Moreover, this may stress the victim so much that any potential that might have existed for retrieval of time-sequence information will be obliterated by the prefrontal cortex impairment the investigator has caused.

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