2Basic Neurobiology of Trauma CortexSensory ThalamusDr. Ryback has just described the many psychological symptoms that accompany an individual’s traumatic response to rape.She also alluded to the vast body of scientific literature documenting those findings.There is another, more recent scientific literature that has emerged in the past 5 to 10 years that now allows us to understand the biological underpinnings of the symptoms that Dr. Ryback has described.My goal, for the next 15 minutes, is to provide you with a mini-course on this new neurobiological science.The bottom line of this 15-minute presentation is this: The rape victim’s traumatic reactions and symptoms are grounded in physiological and anatomical changes in the brain.The cast of characters:This is a very, very schematic diagram of the principal brain structures I’ll be talking about. Please don’t take this as an accurate rendering of what’s inside your skull.The cortex: the location of our higher cognitive and integrative functioning.The Sensory Cortex: the switching station where all incoming sensory information is first analyzed and then directed onward for further processing.The Amygdala: A more ancient part of our brain, one that was essentially identical 100 million years ago when we were all mammals, not yet thinking about becoming the apes we are today.AmygdalaBasic Neurobiology of Trauma
3The “high” road The “low” road FEAR Although most of us don’t consider fear to be a pleasant experience, it is actually crucial for our survival, and has been for the millions of years of our species’ evolution.So evolution has provided us with 2 pathways for processing information that might lead us to experience fear.The “high” road, leads from the sensory thalamus up into the cortex, where the sensory stiumulus we are evaluating can be thoroughly analyzed. This is a very important step, but it has one significant disadvantage: it is relatively slow. It can takea few seconds to analyze a new sensory stimulus.So evolution has seen fit to provide us with a “low” road. A pathway that leads from the sensory thalamus directly to the amygdala. This pathway provides no opportunity for advanced analysis of the stimulus, but it does one very important thing: within milliseconds, it fires of neurons in the amgdala which in turn trigger our body’s emergency response systems.FEAR
4VINE? SNAKE? So, this is how it might work: Here is someone who has never before been bitten by a snake. A non-traumatized person.He or she perceives a stimulus that could be a snake or could be a vine.The amygdala is alerted by the sensory thalamus, while simultaneously, the informtion from the percept is fed to the cortex for more thorough analysis.
5VINEPhew! VineIn this scenario, the cortex, after comparing the sensory information to stored data about the physical attributes of snakes vs. vines, concludes that the stimulus is a vine.As a result, it sends inhibitory signals to the amygdala, shutting down the alert.
6SNAKE!SNAKE!In this scenario, the cortex confirms that the stimulus is indeed a snake.It sends signals to the amygdala that amplify the alert and trigger the amygdala into initiating a full-bore response.The fight or flight response is triggered.You will probably freeze momentarily, and then you might either run for your life, or find out what it’s like to do battle with a rattlesnake.Fear
7Fear SNAKE! HERE WE ARE, 3 MONTHS LATER: LOOK WHAT’S CHANGED IN THIS PERSON’S BRAIN.THE NEURAL NETWORKS THAT RECOGNIZE SNAKE STIMULI WERE BURNED INTO THE SENSORY THALAMUS AND AMYGDALA BY THE EXPERIENCE OF BEING BITTEN BY THE COBRA.AS A RESULT, ONLY WEAK SIGNALS ARE NOW SENT TO THE CORTEX, WHILE POWERFUL SIGNALS ARE SENT TO THE AMYGDALA.IN EFFECT, THE CORTEX IS NOW BY-PASSED, AND EVERY TIME THIS PERSON SEES A VINE, A COILED GARDEN HOSE OR ANYTHING ELSE RESEMBLING A SNAKE, THEIR AMYGDALA IS IMMEDIATELY TRIGGERED INTO ACTION AND THEY EXPERIENCE A FULL-FLEDGED FIGHT OR FLIGHT RESPONSE.Fear
8No Threat No Danger Pre-Trauma Processing of “ordinary” stimulus SO, LET’S TRANSLATE THIS TO THE WORLD OF THE RAPE VICTIM.HERE’S A STIMULUS THAT ORDINARILY WOULD NOT TRIGGER A FEAR RESPONSE.THE BRAIN PROCESSES THE STIMULUS ALMOST EXCLUSIVELY THROUGH THE CORTEX, AND NO FEAR RESPONSE IS TRIGGERED.Pre-Trauma Processing of “ordinary” stimulus
9Threat!! Danger!! Post-Trauma Processing of “ordinary” stimulus BUT AFTER A RAPE, THAT ORDINARY STIMULUS IS NOW RECOGNIZED BY THIS BRAIN AS A FEAR STIMULUS.WHY? BECAUSE A PAIR OF HANDS WERE USED TO HOLD HER DOWN DURING THE RAPE.SO NOW, A PAIR OF HANDS ARE NO LONGER A MUNDANE STIMULUS.WHEN THEY ARE PERCEIVED, THE INFORMATION IS FED DIRECTLY TO THE AMYGDALA, BYPASSING THE CORTEX, AND A FULL-FLEDGED FIGHT OR FLIGHT RESPONSE IS TRIGGERED.THE CORTEX EITHER CANNOT INHIBIT THIS FROM HAPPENING, BECAUSE IT HAPPENS BEFORE THE CORTEX CAN INTERVENE.OR, THE CORTEX MAY ACTUALLY AMPLIFY THE SIGNALS, IN EFFECT, AGREEING WITH THE INITIAL INTERPRETATION OF THREAT.Post-Trauma Processing of “ordinary” stimulus
10Trauma produces an anatomical change in the brain THIS IS THE ANATOMICAL CHANGE THAT IS RESPONSIBLE FOR THIS PERSON’S REACTION TO THE PAIR OF HANDS.THE RAPE CREATED A PERMANENT NETWORK OF NEURAL CONNECTIONS IN THE AMYGDALA.THIS NETWORK DOES 2 THINGS:1) IT IS HYPERSENSITIVE TO ANY INCOMING STIMULI THAT RESEMBLE ANY OF THE STIMULI THAT WERE PRESENT DURING THE RAPE.2) WHEN ANY SIMILAR STIMULI ARE PERCEIVED, IT REACTS WITH HYPER-SPEED, IMMEDIATELY TRIGGERING A FIGHT OR FLIGHT RESPONSE.Post-trauma fear network in Amygdala
11A landscape of fear-inducing cues AND OF COURSE A PAIR OF HANDS IS JUST A SINGLE EXAMPLE.FOR ALL RAPE VICTIMS, THERE ARE MANY, MANY STIMULI THAT, AFTER THE RAPE, ARE POTENTIAL TIME BOMBS THAT CAN SET OFF THE AMYGDALA.SO, IF A RAPE VICTIM IS ON THE STAND, AND THE DEFENSE ATTORNEY MANOUVERS HIMSELF SO THAT SHE HAS TO LOOK AT THE DEFENDANT, IT SHOULD NOT BE SURPRISING IF SHE FREEZES, OR BECOMES SUDDENLY FEARFUL AND DISORGANIZED.SHE ISN’T BEING WEAK, OR UNCOOPERATIVE, SHE IS SIMPLY REACTING THE WAY EVOLUTION HAS DEMANDED.ONE LOOK AT THE DEFENDANT’S FACE, OR HANDS, AND SUDDENLY SHE IS EXPERIENCING EXACTLY WHAT YOU WOULD NOW ALL BE EXPERIENCING IF SOMEONE WALKED INTO THIS ROOM AND BEGAN SHOOTING US ALL DOWN.A landscape of fear-inducing cuesPost-trauma fear network in Amygdala
12Neurobiology of Non-Traumatic Memory Integrated NarrativeNeurobiology of Non-Traumatic Memory
13Neurobiology of Traumatic Memory LTP builds the neural networks that create new memoriesLTPLTPLTPHippocampusNeurobiology of Traumatic Memory
14Neurobiology of Traumatic Memory Trauma interferes with LTP functioningLTPResults in loss & fragmentation of memoriesLTPLTPHippocampusNeurobiology of Traumatic Memory