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Dan Siegel on Explicit Memory

Dan Siegel hand model 3Dr. Daniel J. Siegel uses his “hand model” of the brain to show schools kids, and the rest of us, how we need all three of the brain’s main parts to be working, and to work together.  Say the wrist is the spinal cord.  Then the palm represents the reptilian brain stem, the thumb is the emotional limbic brain, and the fingers are the thinking frontal cortex. Video:

But last week, we said that neither the brain nor the mind can simply create memories like a video camera makes movies.  Instead, first we receive a flood of raw sensory data packets from the outside world which is scattered around the body, the nerves and the primitive reptilian brain stem.  And the primitive brain stem (palm of hand) doesn’t think — or have conscious memories.

For real permanent memory, which he calls “explicit memory,” Siegel says we need the hippocampus, which is up above the brain stem, in the limbic emotional lobe (thumb).  The hippocampus is responsible to A. integrate the raw sensory data into a coherent picture, and B. put a “time tag” on it – transfer it into long-term permanent memory, where it can be retrieved later.  That’s the only way to get it into conscious thought, which occurs in the frontal cortex, the highest cognitive part of the brain (the fingers in his model).

Explicit memory is what we usually “think” of as memory; it’s a “thinking memory” or “cognitive memory,” a memory we can remember in our thinking brain. It’s “the whole movie,” for which a caption of sorts has developed in the higher parts of the brain to say: ‘this is a dog, and it’s this particular dog right now” – as opposed to that dog you saw in 1994.

But there are (at least) four ways in which the hippocampus may not be available  –  which means, humans easily may not remember traumatic events, Siegel shows.

Four Ways to Turn Off Hippocampus

Scarecrow That's Me all overFirst off, from conception to 36 months, even in a 100% healthy child with secure attachment, the hippocampus isn’t working yet; doesn’t have enough myelin to fire, it’s just not online. Events which happen during this first 45 months of life just don’t automatically become conscious memories.  Siegel gives an example of a toddler bitten by a dog.  But this is also true for any memory function a toddler has, of all events pleasant or frightening, before the hippocampus is fully working around age 3.

“Let’s say I’m 6 months old and I’m bitten by a dog on the hand,” Siegel says. “And then I’m 2 and again I’m bitten by a dog on my hand. So I’m going to have a feeling of fear when I see dogs, I’m going to have a feeling of pain in my body,  I’ll have many memories, all implicit – feeling of fear, feeling of pain in my hand, visual what does a dog look like, barking sound what does a dog sound like – and the feeling that I want to get ready to run

“Implicit memory when it’s encoded and just stays in that pure form goes into storage where it’s just changes in my synaptic connections,” he says.  It’s purely a set of raw unconscious body memory packets.

Without a functioning hippocampus, the data sits scattered all over the body – like the straw Scarecrow in the Wizard of Oz.  “They tore my legs off and threw them over there,” he says. “ Then they took my chest out and threw it over there.”  “That’s you all over,” says the Tin Man.

So neither of these two incidents, the bite at six months or the bite at age 2, ever got integrated into a coherent conscious memory  – nor did they ever get a “time tag” put on them, a clear concept that the two incidents happened in 1992 and 1994, say.

What happens to this person as an adult 20 years later in 2014 when he sees a dog?  “Now today I hear a dog barking,” Siegel goes on, and my brain goes to retrieve whatever memory it has of “dog.”

“The retrieval of a memory is the firing of neural patterns that are similar to but not identical with, what was encoded at the initial time of the experience.

“But here’s the most important lesson about memory integration:  Implicit-only memory does not feel like it’s coming from the past.  When I hear a dog, I just feel fear, period.  I don’t say,  ‘Oh, I was bitten at six months, at two years… yeah, dogs can hurt you.’  No; I just feel scared – and I get ready to run [without thought.]  Maybe I focus on the fangs of a little puppy and I see a wolf – not just a little cute puppy.  Fear hijacks my perceptual system.” [ FN1]

Second, the hippocampus itself can be damaged during those 45 early developmental months (one reason it’s called “developmental trauma.”)  If an infant or toddler has repeatedly frightening experiences, such as hostile adults continuously in the home, the neurology of the primitive brain stem gets thrown off enough that it can harms the development of the higher brain lobes — which are outgrowths of the brain stem. The hippocampus can be badly damaged, to where when we feel scared irrationally, we physically can not “think our way out” just as Dr. Bessel van der Kolk told the New York Times.

This was me; I’d been told that I’d had infant trauma from conception to 36 months.  Listening to Siegel it hit me that talk therapy (and other cognitive work) regarding events and feelings during years no one can remember, had to be a waste of time. Siegel said the memories were lying around un-assembled in my body.

One of the next webinars I heard was his friend Dr. Peter A. Levine, talking about how to assemble these body memories, using “somatic experiencing.”  So I took Dr. Levine’s book “Healing Trauma” to my therapist and said: “Sorry you’re not familiar with somatic work, but I got traumatized before I was 3 and had a thinking brain, so the trauma’s baked down into my body parts, where talk and cognition can’t get at it.  This book is what we’re going to do.”  Our results were spectacular. [FN2]

Third, Siegel said that even if the hippocampus develops pretty well, trauma after 3 years of age and at any point in life, floods the body with so much stress hormones that  this can turn off the hippocampus. “If you massively secrete cortisol stress hormone, at the same time you’re secreting adrenaline, cortisol, in high amounts, shuts off the hippocampus temporarily.  Over the long run, it can actually kill hippocampus cells.

“But adrenaline increases the synaptic changes in implicit memory. So what we’ve just described, a useful vision for PTSD, is a model for explaining flashback of phenomena: when an implicit memory is reactivated without any explicit elements, the hippocampus hasn’t been involved to experience these things in awareness. So it’s not the same as unconscious memory or anything like that. These are elements encoded, stored and now retrieved into awareness, but when they’re implicit only, they have no tagging that they’re coming from the past.” [FN3]

Fourth, there are types of trauma where a person older than age 3 with a functional hippocampus can literally, during a traumatic event, dissociate themselves to avoid experiencing it when it’s happening  – so they can’t remember it later.  “You can divide attention,” says Siegel.  “If you’re being attacked you can focus on a beautiful beach, so you’ve taken your hippocampus out of the picture – but unfortunately you can not block the implicit coding [of the raw separate bodily memories of what was actually being done to you -kb]…

“If you were betrayed by your father or mother, if they abandoned you or hurt you or ignored you in terrible ways, it makes no sense that that would happen to you. So how do you make sense of something which doesn’t make any sense?,” says Siegel.  “It turns out that the part of our hippocampus which is the narrator is in the left hemisphere, but it has to draw on the hippocampus in the right hemisphere for storage of autobiographical data.

“Say your dad drank and he attacked you — so you dissociated and thought about the beach.

“So now [years later] the therapist asks you ‘What did that feel like, were you terrified of your parents?’   Your left narrator wants to cooperate, so it calls over to the right side and asks ‘Any feelings of fear of parents over there?’ and the right side answers back ‘Nothing over here, Dan, but sand and water.’  But your body also feels fear and you  may be sick to your stomach — none of it conscious.”   [FN4]


Kathy’s news blogs expand on her book “DON’T TRY THIS AT HOME: The Silent Epidemic of Attachment Disorder—How I accidentally regressed myself back to infancy and healed it all.” Watch for the continuing series each Friday, as she explores her journey of recovery by learning the hard way about Attachment Disorder in adults, adult Attachment Theory, and the Adult Attachment Interview.


FN1   Siegel, Daniel J., MD, “Domains of Integration,” July 27, 2010 lecture audio  To download, right click Play arrow, left click Save Audio As  [or go to  scroll down to title, right click to download]

FN2  Levine, Peter A., PhD, “Healing Trauma: A Pioneering Program for Restoring the Wisdom of Your Body,” ‘Sounds True, Inc.,’ Boulder CO, 2005; ISBN 1-159179-247-9

FN3   Siegel, Daniel J., MD, “How Mindfulness Can Change the Wiring of Our Brains, October 12, 2011 Webcast, National Institute for the Clinical Application of Behavioral Medicine (NICABM),

FN4   op cit  FN1  Siegel, “Domains of Integration”

Daniel J. Siegel, MD, is clinical professor of psychiatry at the UCLA School of Medicine on the faculty of the Center for Culture, Brain, and Development and founding co-director of the Mindful Awareness Research Center.  He is a Distinguished Fellow of the American Psychiatric Association and Executive Director of the Mindsight Institute. He is also Founding Editor for the Norton Professional Series on Interpersonal Neurobiology which contains over three dozen textbooks.

Must-read interview:
Siegel, Daniel J., MD, “Early childhood and the developing brain,” on “All in the Mind,” ABC Radio National, Radio Australia, June 24, 2006 at:

Books by Dan Siegel:
–”The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are,” (Guilford, 1999). How attachment in infancy and childhood creates the brain and the mind.
–”Healing Trauma: Attachment, Mind, Body, and Brain,” Marion F Solomon, Daniel J Siegel, editors,  New York, NY:  W.W. Norton and Company;  2003.   357pg  Reviewed by Hilary Le Page, MBBS at:
–”The Mindful Brain: Reflection and Attunement in the Cultivation of Well-Being,” (Norton, 2007)
–”The Mindful Therapist: A Clinician’s Guide to Mindsight and Neural Integration,” (Norton, 2010)
–”Mindsight: The New Science of Personal Transformation,” (Bantam, 2010)
–”Parenting from the Inside Out: How a Deeper Self-Understanding Can Help You Raise Children Who Thrive,” (Tarcher/Penguin, 2003) with Mary Hartzell
–”The Whole-Brain Child: 12 Revolutionary Strategies to Nurture Your Child’s Developing Mind,” (Random House, 2011) with Tina Payne Bryson, Ph.D
–”Brainstorm: Power and Purpose of the Teenage Brain,”  (Tarcher, 2013)

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