Consequences of ptsd and memory processing

Editor's Notes

• #5: Recent studies show that dendritic spines are dynamic structures. Their rapid creation, destruction and shape-changing are essential for short- and long-term plasticity at excitatory synapses on pyramidal neurons in the cerebral cortex. The onset of long-term potentiation, spine-volume growth and an increase in receptor trafficking are coincident, enabling a ‘functional readout’ of spine structure that links the age, size, strength and lifetime of a synapse. Spine dynamics are also implicated in long-term memory and cognition: intrinsic fluctuations in volume can explain synapse maintenance over long periods, and rapid, activity-triggered plasticity can relate directly to cognitive processes. Thus, spine dynamics are cellular phenomena with important implications for cognition and memory. Furthermore, impaired spine dynamics can cause psychiatric and neurodevelopmental disorders.
• #6: It has been widely recognized that the understanding of the brain code would require large-scale recording and decoding of brain activity patterns. In 2007 with support from Georgia Research Alliance, we have launched the Brain Decoding Project Initiative with the basic idea which is now similarly advocated by BRAIN project or Brain Activity Map proposal. As the planning of the BRAIN project is currently underway, we share our insights and lessons from our efforts in mapping real-time episodic memory traces in the hippocampus of freely behaving mice. We show that appropriate large-scale statistical methods are essential to decipher and measure real-time memory traces and neural dynamics. We also provide an example of how the carefully designed, sometime thinking-outside-the-box, behavioral paradigms can be highly instrumental to the unraveling of memory-coding cell assembly organizing principle in the hippocampus. Our observations to date have led us to conclude that the specific-to-general categorical and combinatorial feature-coding cell assembly mechanism represents an emergent property for enabling the neural networks to generate and organize not only episodic memory, but also semantic knowledge and imagination.
• #7: Robert M. Sapolsky (1986); GCs endanger hippocampal neurons by impairing their energy metabolism. Diminished volumes, neuronal integrity, and functional integrity of the hippocampus in PTSD (Shin et al, 2006). Ehlers 2004: Distressing and intrusive reexperiencing of the trauma is a hallmark symptom of posttraumatic stress disorder (PTSD; American Psychiatric Association, 1994). However, unwanted memories of trauma are not a sign of pathology per se. In the initial weeks after a traumatic experience, intrusive memories are common. For most trauma survivors, intrusions become less frequent and distressing over time. A central question for understanding and treating patients with PTSD is therefore what maintains distressing intrusive reexperiencing in these people. Three factors appear to be important: (1) memory processes responsible for the easy triggering of intrusive memories, (2) the individuals’ interpretations of their trauma memories, and (3) their cognitive and behavioral responses to trauma memories. Bremner, 1995 - Monkeys exposed to the extreme stress of improper caging have shown increased glucocorticoid release as well as damage to the CA2 and CA3 subfields of the hippocampus (10). Studies in a variety of animal species suggest that direct glucocorticoid exposure results in a loss of neurons and a decrease in dendritic branching in the hippocampus (11, 12) with associated deficits in memory function (13). The mechanism of action of glucocorticoid toxicity is probably through an increase in the vulnerability of neurons to the toxicity of excitatory amino acids (14–16).
• #8: The amygdala’s function in the assessment of threat-based stimuli relates to the processing of fear conditioning. Due to the hyper-responsivity of the amygdala in PTSD cases, people tend to be hypervigilant and negatively appraise events or potential threats in their environment (Höistad et al, 2008).
• #9: When the mPFC becomes hyporesponsive or traumatised or damaged, individuals suffering from trauma struggle to appropriately express and extinguish their fear responses to daily life stimuli (Hanson et al, 2015)
• #11: A variety of the psychtherapeutic approaches to PTSD, all involving some form of exposure and trauma processing have been shown to be effective – exposure, stress inoculation training, cognitive processing therapy, EMDR, CPT, specifically designed for the treatment of PTSD resulting from sexual assault, consists of two integrated components: cognitive therapy and exposure in the form of writing and reading about the traumatic event (Resick, 1992; Resick & Schnicke, 1992, 1993). Resick et al 2002: exposure component consists of having clients write detailed accounts of the most traumatic incident(s) that they read to themselves and to the therapists. Clients are encouraged to experience their emotions while writing and reading
• #15: Molecular magnetic resonance imaging A Hengerer, PhD1,* and J Grimm, MD2
• #16: Molecular magnetic resonance imaging A Hengerer, PhD1,* and J Grimm, MD2