Posttraumatic Stress Disorder: Cerebellar Regulation ...

Posttraumatic stress disorder: Cerebellar regulation of ... Ursano, Robert J;Fullerton, Carol S Psychiatry; Winter 1999; 62, 4; ProQuest pg. 325

Posttraumatic Stress Disorder: Cerebellar Regulation of Psychological, Interpersonal, and Biological Responses to Trauma? Robert J. Ursano and Carol S. Fullerton ALTERATION in the sense of time is the most commonly reported peri traumatic dissociative symptom. A case report of a trauma victim illustrates the posttraumatic alteration in the sense of time as well as loss of spatial memory. Recent studies of cerebellar function indicate the cerebellum may be critical to both spatial memory and the sense of time. Identifying regulators of psychological, interpersonal, and biological responses to traumatic events is important in advancing our understanding of the effects of trauma. The cerebellum may be part of the initial posttraumatic response. For those interested in how psychotherapy changes behavior, traumatic events place in stark relief the process ofbehavior change. In addition, research and clinical work with traumatized individuals highlight the fundamental need to understand the interaction of the subjective, interpersonal, and biological responses to traumatic events. Dissociative symptoms, including changes in one's sense of time and place, are common during a traumatic event (i.e. peritraumatic dissociation) and may be a poor prognostic sign (Shalev, Peri, Canetti, and Schreiber 1998; Ursano, Fullerton, Epstein et al. 1999). Another cognitive process occurring during exposure to traumatic death is identification with the dead, the feeling "It could have been me." This process of thinking by similarity, perhaps activated by the traumatic exposure, also predicts a greater likelihood of more chronic problems (Ursano, Fullerton,

Vance, and Kao 1999). But we must ask, are these early symptoms different phenomena or are they an indication of a central disturbance? In fact, are intrusive memories, avoidance, peritraumatic dissociation, and thinking by similarity all different phenomena? Or might they be related to a dysregulation in one's ability to maintain time and space awareness, thus affecting the ability tobe in the present rather than the past and to maintain accurate person and place awareness? Regulators operate to maintain diverse behavioral responses-from bodily temperature control to sleep-wake cycles. Biological and behavioral regulation is maintained by our neurobiology and interpersonal interactions. For example, the interpersonal environment, including the mother's voice (Hofer 1987, 1998) or the presence of a trusted other for a phobic child approaching a feared object, can operate as a critical regulator of arousal and

Robert J. Ursano, MD, is Professor and Chairman of the Department of Psychiatry at Uniformed Services University of the Health Sciences (USUHSJ. CarolS. Fullerton, PhD, is Associate Professor (Research) in the Department of Psychiatry, USUHS. Address correspondence to Dr. Robert J. Ursano, Department of Psychiatry, Uniformed Services University of the Health Sciences, 4301 Jones-Bridge Rd., Bethesda, MD 20814.

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ROBERT J. URSANO AND CAROLS. FULLERTON

fear. Like the thermostat on the wall, regulators at the interpersonal or neurobiological levels modulate complex systems and simultaneously explain more than one effect (e.g., heat and cold). Alterations in regulators can result in profound effects or subtle shifts in the level offunction (Staab, Fullerton, and Ursano 1999). The cerebellum-that part of the brain that in the past had been only associated with balance and coordination-may be a fundamental regulator in the response to trauma. The cerebellum has recently been shown to be an important regulator of time and space awareness. The case below illustrates trauma related alterations in the sense of time and space that may be evidence of cerebellar dysregulation. CASE

A 44-year-old male was in a serious motor vehicle accident. While driving his car, he was hit on the passenger side by a truck that ran a red light. "If my wife had been with me, she would have been killed," he said. He sustained a wrist injury from holding the wheel, minor cuts from glass, and his car was destroyed. He reported no head injury, and his neurological exam was normal as were head X rays. Several weeks after the accident and continuing for 8 months he noted mild to moderate intrusive, avoidant, and arousal symptoms meeting criteria for posttraumatic stress disorder. He described the accident as "everything was in slow motion." For a number of hours after the accident, he noticed time seemed to go slow and he felt unusually calm, detached from the things around him as he arranged for his car to be towed, called his family, and was seen in the emergency room. Over the next several months he noted two problems. First, he had difficulty recalling where he parked his car in a parking lot. "Normally it is not something I attend to. But I found that I began to get anxious because I was not able to recall the place I had parked so I began a routine: after I parked I took

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a moment to note the area I was in. This helped-consciously using a marker near by-but I only felt comfortable after I had really located it by several markers, its location near lamp posts, doors, etc. That worked well. I could not trust my usual automatic knowing." He also observed the same loss of spatial memory in his work. He often worked with computer printouts of many numbers and automatically recalled where in a column of numbers the one of interest was located. He found this automatic recall was much slowed and sometimes unavailable. Sense of Time

Altered sense of time, feeling that time either slowed down or speeded up, is the most common peritraumatic dissociative symptom reported by individuals during or shortly after a traumatic event (Cardena and Spiegel 1993; Noyes and Kletti 1977; Shalev et al. 1996; Terr 1984). In the case of this 44-year-old man, time was noted to have slowed down during and immediately after the accident. Distortion of the sense of time has been examined in laboratory studies. Both the basal ganglia (Harrington, Haaland, and Hermanowicz 1998) and cerebellum (Jueptner, Fleurich, Weiller, Mueller, and Diener 1996) of the brain have been linked to a brain timing system. Brain imaging studies have shown both decreased cerebellar blood flow (Matthew, Wilson, Turkington, and Coleman 1998) and increased left cerebellar blood flow (Jueptner et al. 1996) associated with an altered sense of time. If there is a "time clock," the subjective experience of time speeding-up would mean that the time clock regulator had slowed down; that is, each second took longer to "tick" and vice versa (McCrone 1997). Spatial Memory

Both clinical and experimental studies suggest that the cerebellum and its network are involved in spatial processing. Three search strategies are generally de-

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PTSD: CEREBELLAR REGULATION?

scribed for spatial memory. A "place" strategy depends on using an "allocentric" spatial map, identifYing markers based on their absolute relationships to each other. A praxic strategy is repeating specific sequences of movements covering the same distance and angles. Lastly, a taxic strategy can be used whereby one approaches specific cues associated with the target (Molinari, Petrosini, and Grannaldo 1997). In the motor vehicle accident case above, place strategy was preserved, but praxic and taxic strategy were lost or impaired. Animal studies (Molinari et al. 1997; Petrosini, Molinari, and Dell'Anna 1996) have shown that hemicerebellectomized rats lose the ability to use praxic and taxic but preserve place strategy for spatial memory tasks in the Morris water maze (Morris 1981). The spatial system appears to continue to operate where other systems of memory are lost. The deficit is in impaired memory acquisition rather than utilization; that is, the animals are fine if they have an already acquired internal "map." (The opposite observation has been made with hippocampal injury; lesioned animals learn cues for location but cannot perform under a place strategy.) Thus cerebellar, and perhaps basal ganglia, dependent aspects of spatial memory appear to be related to the procedural- and performance-based aspects of spatial memory in contrast to the declarative-representational-based components. This may be a result of the cerebellar contribution to a timing and ordering cognitive function (lvry and Baldo 1992, Silveri, Leggio, and Molinari 1994).

DISCUSSION

Disturbance in the regulation of time and space perception may be important in the onset of posttraumatic stress disorder (PTSD). The cerebellum appears to be a critical neurobiological component of one's sense of time and space. We know little about the interpersonal and developmental aspects of time and space awareness. The disturbance of sense of time has often been reported during or immediately after a traumatic event. It may be proposed that arousal or anxiety is the initiator of the alterations of time and spatial sense. Alternatively, these time-space alterations are an indicator of a more general regulator disturbance that affects both cognition and arousal. Brain imaging studies of cerebellar function in stressful settings may be able to delineate whether this brain region makes substantial contributions to the disturbances seen after traumatic events. The study of the onset conditions of PTSD can offer new avenues for research and clinical intervention, which studies of the chronic disorder may overlook. The transitory symptoms of loss of time and spatial sense do not appear to persist after the early period of the trauma exposure and therefore may not be evident in studies of chronic PTSD. Studies of chronic PTSD may identifY sustaining factors of the illness rather than initiating factors. Prevention of chronic PTSD will require attention to the early onset symptoms of PTSD. The cerebellum may play a role in the initiation of the PTSD process.

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