BIOL PSYCHIATRY 1990;27:469-471
469
EDITORIAL
The Black Hole of Trauma
One of the striking features of post-traumatic stress disorder (PTSD) is the degree to which a past event comes to dominate the patient's associations. As all roads lead to Rome, all the patient's thoughts lead to the trauma. A war veteran known to us can't look at his wife's nude body without recalling with revulsion the naked bodies he saw in a burial pit in Vietnam, can't stand the sight of children's dolls because their eyes remind him of the staring eyes of the war dead, and can't walk on his property without eyeing the tree line for infiltrators. A child-abuse victim fears that every time her psychiatrist leans forward, he's about to reach out and grab her. A group of veterans astound their therapist when they argue that olive pickers in a painting really portray snipers in trees, and accuse him of hanging the painting in his office to provoke them. Sometimes these associations to the trauma seem so forced that the inexperk:nced clinician may think that the patient is putting it on. The experienced clinician, however, knows that, far from a put-on, associations to the traumatic event are quite beyond the PTSD patient's voluntary control. The trauma appears to irresistibly draw thoughts and perceptions to it. Lang (1979, 1985) has proposed that PTSD be vi:wed ~s a pathological associative ~;etwork (Pitman, 1988). In a two-dimensional net~Jork model, such as originally contemplated by Lang and by Pitman, memories of the traumatic event would be located at the center, with associations of progressively decreasing relatedness to the trauma radiating outward. Although a two-dimensional model can provide for the organization of memory, it cannot provide tbr its flow. In an address given at the 1989 American Psychiatric Association Annual Meeting, Professor John Hopfieid showed how adding a third dimension can address this limitation. Summarizing the results of work with neuronlike circuit models of associative networks (Hopfield, 1982; Tank and Hopfield, 1987), Hopfield described how such networks can be viewed as contour maps, with associations flowing from higher to lower points under the influence of a kind of gravity. A stimulus impinging on the mind can be conceived as behaving like a " . . . raindrop iand(ing) on a terrain of hllis and valleys. The drop moves generally downhill until it ends up at the bottom of a nearby valley" (Tank and Hopfield, 1987, p. 106~. Likewise, associative currents Pow into basins of memory that represent the equivalents of the nodal points in two-dimensional networks. The deeper the memory basin and the steeper its walls, the more likely a train of associations is to end up in it. In PTSD, the traumatic event may be conceptualized as occupying a basal location in the contour map of the mind, forming a Dead Sea of memory, into which all too many of the patient's associations, even those of distant origin, inexorably flow. In the extreme case, "the basin of attraction will fill the e n t i r e . . , s u r f a c e . . , leaving only one stable state for the circuit" (Tank and Hopfield, 1987, pp. 106-107). The ultimate gravitational attraction in the physical universe is represented by the black hole, a place in space-time that has such high gravity that even light cannot pass by without being drawn into it. In a children's science ficdon story (Walt Disney Productions, © 1990 Society of Biological Psychiatry
0006-3223/90/$03.50
470
BIOL PSYCHIATRY
Editorial
1990;27:469-471
1979), the crew of the spaceship Palomino struggle to avoid coming too close to a black hole ~ d being sucked in. So too our PTSD patients struggle to avoid thoughts, activities, or situations associated with the trauma (American Psychiatric Association, 1987), not only because they are so painful but also because ~ey are so absorbing. Within a black hole, the passage of time comes to an end (Hawkins, 1988). Similexly, the traamatic event may have the quality of timelessness fo'~:the PTSD sufferer (Pitman, 1988). One veteran complained "Since Vietnam, I feel like I've been in a time warp." The insight into the structural basis of P1"SD offered by Hopfield's biophysics challenges the biological psychiatrist to learn what pathophysiological mechanisms might establish and maintain the impact of trauma. How does the traumatic event carve its canyons and basins of memory into the living brain? In modeling neuronal networks, Tank and Hopf~eld (1987) have employed electronic circuits consisting of amplifiers with excitatory an~ inhibitory interconnections. The circuit's topographical properties are determined by two factors: the input currents to the amplifiers (neurons), ~ d the valences and strengths of the connections between ampiitiers (synapses). A physiological process modulating the strength of synaptic connectivity between neurons could provide a means by which the response to the traumatic event forms the PTSD network. Perhaps stress hormones and neuromodulators mobilized at the time of the event serve this role (Pitman, 1989). Tank and Hopfield have further found that increasing the current input to the amplifiers in their circuits results in a deepening of the valleys in the circuit's topography. This leads the biological psychiatrist to wonder whether continuing inputs to neurons might maintain the steepness of the memory basins of PTSD. Clinically, one observes that strong negative emotion facilitates PTSD associations. Could emotion entail a physiological modulating input to neurons in PTSD networks, analogous to the current inputs to Hopfield's amplifiers? If so, by what mechanism? Miller (1981) has suggested that diffusely acting chemical transmitters, possibly neuropeptides, may serve such a role for drive, a concept closely related to emotion. If we can identify the processes by which a traumatic ever t engraves itself on memory, and by which the strength of the memory is maintained, what guidap,ze might such insight provide for the therapeutic modification of PTSD? Certain kinds ~)f psychological interventions, e.g., flooding (Lyons and Keane, 1989), appear capable of modifying PTSD networks. This must have an underlying biological basis, and two possibilities come to mind. The first involves therapy's changing associative connections in the traumatic network by the incorporation of "corrective information" (Foa and Kozak, 1986). The second involves fla'ttening the contour of the network by the reduction of negative emotion, leaving the associative memory of the trauma unaltered but diminishing its pull. The mental disorder identified and described as PTSD also poses a challenge to the basic neuroscientist. As is often the case with psychopathological phenomena, PTSD illustrates the operation of certain brain processes with exaggerated clarity and high relief, thereby creating an opportunity for their study and elucidation. Roger K. Pitnvm Scott P. Orr
References American Psychiatric Association (1987): Diagnostic and StatisticalManual o/Mental Disorders, Third Ed. (revised). Washington: American Psychiatric Association. Foa BE, Kozak MJ (1986): Emotional processing of fear: Exposure to corrective information. Psychol Bull 99:20-35.
F.ditorial
BIOL PSYCHIATRY 1990;27:~.~9-471
471
Hawkins S (1988): A BriefHistory of Time: From the Big Bang to Black Holes. blew York: Bantam Books. Hopfield JJ (1982): Neural ne.~-.orks and physical systems with emergent collective computational abilities. Proc Natl Acad Sci USA 79:2554-2558. Lang PJ (1979): A bio-informational theory of emotional imagery. Psychophysiology 16:495-512. Lang PJ (1985): The cognitive psychophysiology of emotion: fear and anxiety. In Tuma AH, Maser J (eds) Anxiety and the Anxiety Disorders. Hillsdale, NJ: Lawrence Erlbaum Associates, pp. 131-170. Lyons JA, Keane TM (1989): Implosive therapy for the treatment of combat related PTSD. J~urnal of Traumatic Stress 2:137-152. Miller R (1981): Meaning and Purpose in the Intact Brain. Oxford: Clarendon Press. Pitman RK (1988): Post-traumatic stress disorder, conditioning, and network theory. Psychiatric Annals 18:182-189. Pitman RK (1989): Post-traumatic stress disorder, hormones, and memory. Biol Psychiatry 26:221223. Tank DW, Hopfield JJ (1987): Collective computation in neuronlike circui~. Sci Am 257:104114. Walt Disney Productions (1979): The Black Hole. New York: Random F ouse.
469
EDITORIAL
The Black Hole of Trauma
One of the striking features of post-traumatic stress disorder (PTSD) is the degree to which a past event comes to dominate the patient's associations. As all roads lead to Rome, all the patient's thoughts lead to the trauma. A war veteran known to us can't look at his wife's nude body without recalling with revulsion the naked bodies he saw in a burial pit in Vietnam, can't stand the sight of children's dolls because their eyes remind him of the staring eyes of the war dead, and can't walk on his property without eyeing the tree line for infiltrators. A child-abuse victim fears that every time her psychiatrist leans forward, he's about to reach out and grab her. A group of veterans astound their therapist when they argue that olive pickers in a painting really portray snipers in trees, and accuse him of hanging the painting in his office to provoke them. Sometimes these associations to the trauma seem so forced that the inexperk:nced clinician may think that the patient is putting it on. The experienced clinician, however, knows that, far from a put-on, associations to the traumatic event are quite beyond the PTSD patient's voluntary control. The trauma appears to irresistibly draw thoughts and perceptions to it. Lang (1979, 1985) has proposed that PTSD be vi:wed ~s a pathological associative ~;etwork (Pitman, 1988). In a two-dimensional net~Jork model, such as originally contemplated by Lang and by Pitman, memories of the traumatic event would be located at the center, with associations of progressively decreasing relatedness to the trauma radiating outward. Although a two-dimensional model can provide for the organization of memory, it cannot provide tbr its flow. In an address given at the 1989 American Psychiatric Association Annual Meeting, Professor John Hopfieid showed how adding a third dimension can address this limitation. Summarizing the results of work with neuronlike circuit models of associative networks (Hopfield, 1982; Tank and Hopfield, 1987), Hopfield described how such networks can be viewed as contour maps, with associations flowing from higher to lower points under the influence of a kind of gravity. A stimulus impinging on the mind can be conceived as behaving like a " . . . raindrop iand(ing) on a terrain of hllis and valleys. The drop moves generally downhill until it ends up at the bottom of a nearby valley" (Tank and Hopfield, 1987, p. 106~. Likewise, associative currents Pow into basins of memory that represent the equivalents of the nodal points in two-dimensional networks. The deeper the memory basin and the steeper its walls, the more likely a train of associations is to end up in it. In PTSD, the traumatic event may be conceptualized as occupying a basal location in the contour map of the mind, forming a Dead Sea of memory, into which all too many of the patient's associations, even those of distant origin, inexorably flow. In the extreme case, "the basin of attraction will fill the e n t i r e . . , s u r f a c e . . , leaving only one stable state for the circuit" (Tank and Hopfield, 1987, pp. 106-107). The ultimate gravitational attraction in the physical universe is represented by the black hole, a place in space-time that has such high gravity that even light cannot pass by without being drawn into it. In a children's science ficdon story (Walt Disney Productions, © 1990 Society of Biological Psychiatry
0006-3223/90/$03.50
470
BIOL PSYCHIATRY
Editorial
1990;27:469-471
1979), the crew of the spaceship Palomino struggle to avoid coming too close to a black hole ~ d being sucked in. So too our PTSD patients struggle to avoid thoughts, activities, or situations associated with the trauma (American Psychiatric Association, 1987), not only because they are so painful but also because ~ey are so absorbing. Within a black hole, the passage of time comes to an end (Hawkins, 1988). Similexly, the traamatic event may have the quality of timelessness fo'~:the PTSD sufferer (Pitman, 1988). One veteran complained "Since Vietnam, I feel like I've been in a time warp." The insight into the structural basis of P1"SD offered by Hopfield's biophysics challenges the biological psychiatrist to learn what pathophysiological mechanisms might establish and maintain the impact of trauma. How does the traumatic event carve its canyons and basins of memory into the living brain? In modeling neuronal networks, Tank and Hopf~eld (1987) have employed electronic circuits consisting of amplifiers with excitatory an~ inhibitory interconnections. The circuit's topographical properties are determined by two factors: the input currents to the amplifiers (neurons), ~ d the valences and strengths of the connections between ampiitiers (synapses). A physiological process modulating the strength of synaptic connectivity between neurons could provide a means by which the response to the traumatic event forms the PTSD network. Perhaps stress hormones and neuromodulators mobilized at the time of the event serve this role (Pitman, 1989). Tank and Hopfield have further found that increasing the current input to the amplifiers in their circuits results in a deepening of the valleys in the circuit's topography. This leads the biological psychiatrist to wonder whether continuing inputs to neurons might maintain the steepness of the memory basins of PTSD. Clinically, one observes that strong negative emotion facilitates PTSD associations. Could emotion entail a physiological modulating input to neurons in PTSD networks, analogous to the current inputs to Hopfield's amplifiers? If so, by what mechanism? Miller (1981) has suggested that diffusely acting chemical transmitters, possibly neuropeptides, may serve such a role for drive, a concept closely related to emotion. If we can identify the processes by which a traumatic ever t engraves itself on memory, and by which the strength of the memory is maintained, what guidap,ze might such insight provide for the therapeutic modification of PTSD? Certain kinds ~)f psychological interventions, e.g., flooding (Lyons and Keane, 1989), appear capable of modifying PTSD networks. This must have an underlying biological basis, and two possibilities come to mind. The first involves therapy's changing associative connections in the traumatic network by the incorporation of "corrective information" (Foa and Kozak, 1986). The second involves fla'ttening the contour of the network by the reduction of negative emotion, leaving the associative memory of the trauma unaltered but diminishing its pull. The mental disorder identified and described as PTSD also poses a challenge to the basic neuroscientist. As is often the case with psychopathological phenomena, PTSD illustrates the operation of certain brain processes with exaggerated clarity and high relief, thereby creating an opportunity for their study and elucidation. Roger K. Pitnvm Scott P. Orr
References American Psychiatric Association (1987): Diagnostic and StatisticalManual o/Mental Disorders, Third Ed. (revised). Washington: American Psychiatric Association. Foa BE, Kozak MJ (1986): Emotional processing of fear: Exposure to corrective information. Psychol Bull 99:20-35.
F.ditorial
BIOL PSYCHIATRY 1990;27:~.~9-471
471
Hawkins S (1988): A BriefHistory of Time: From the Big Bang to Black Holes. blew York: Bantam Books. Hopfield JJ (1982): Neural ne.~-.orks and physical systems with emergent collective computational abilities. Proc Natl Acad Sci USA 79:2554-2558. Lang PJ (1979): A bio-informational theory of emotional imagery. Psychophysiology 16:495-512. Lang PJ (1985): The cognitive psychophysiology of emotion: fear and anxiety. In Tuma AH, Maser J (eds) Anxiety and the Anxiety Disorders. Hillsdale, NJ: Lawrence Erlbaum Associates, pp. 131-170. Lyons JA, Keane TM (1989): Implosive therapy for the treatment of combat related PTSD. J~urnal of Traumatic Stress 2:137-152. Miller R (1981): Meaning and Purpose in the Intact Brain. Oxford: Clarendon Press. Pitman RK (1988): Post-traumatic stress disorder, conditioning, and network theory. Psychiatric Annals 18:182-189. Pitman RK (1989): Post-traumatic stress disorder, hormones, and memory. Biol Psychiatry 26:221223. Tank DW, Hopfield JJ (1987): Collective computation in neuronlike circui~. Sci Am 257:104114. Walt Disney Productions (1979): The Black Hole. New York: Random F ouse.
