Functional connectivity of dissociative responses in posttraumatic stress disorder: a functional magnetic resonance imaging investigation.

Compared to patients with a flashback response, dissociative PTSD patients showed increased FC between right cingulate gyrus and left IFG.

“Compared to patients with a flashback response, dissociative patients showed increased FC between right cingulate gyrus and left IFG [56].”

Compared to controls, dissociative PTSD patients showed stronger FC of left VLT with right insula, middle frontal gyrus, superior temporal gyrus, cuneus, and left parietal lobe, but reduced VLT-FC with left superior frontal gyrus, right parahippocampal gyrus, and right superior occipital gyrus.

“compared to controls, dissociative patients showed stronger FC of the left ventrolateral thalamus (VLT) with right insula, middle frontal gyrus, superior temporal gyrus, cuneus, and with left parietal lobe, but reduced VLT-FC with the left superior frontal gyrus, right parahippocampal gyrus, and right superior occipital gyrus.”

For PTSD patients with dissociative responses to autobiographical trauma scripts, there is evidence for altered functional connectivity in areas implicated in sensory processing, consciousness, memory, and emotion regulation.

“For PTSD patients who showed dissociative responses to autobiographical trauma scripts (compared to patients with a flashback response and healthy controls), there is also evidence for altered functional connectivity (FC), i.e., coactivation in areas implicated in sensory processing, consciousness, memory, and emotion regulation [56]”

The dissociative PTSD pattern involves changes in connectivity and activation of the right anterior insula.

“changes in connectivity and activation of the right anterior insula,55,127,128”

Drawing on animal research, Porges postulates that hypoxic conditions, such as hyperventilation-induced cerebral hypoxia, increase the probability that sporadically active cardiac vagal neurons in the DMN will be activated, resulting in an episode of collapsed immobility.

“Drawing on animal research, Porges3 postulates that hypoxic conditions—of which hyperventilation-induced cerebral hypoxia is an example—increase the probability that the sporadically active102 cardiac vagal neurons in the DMN will be activated, resulting in an episode of collapsed immobility.”

Another study from the same research group found that although some dissociative PTSD patients had unchanged (or not increased) HR during trauma exposure, there was no clinical difference between these patients and those who exhibited decreased or increased HR.

“Another study from the same research group found that although some dissociative PTSD patients had unchanged (or not increased) HR during trauma exposure, there was no clinical difference between these patients and those who exhibited decreased or increased HR (Lanius et al., 2005).”

The PTSD dissociative subtype demonstrates additional concomitant brainstem-mediated periaqueductal gray connectivity with structures linked to passive defensive responses and emotional detachment, including the temporoparietal junction, which has been previously associated with depersonalization.

“Specifically, the PTSD dissociative subtype demonstrated additional concomitant brainstem-mediated periaqueductal gray connectivity with structures linked to passive defensive responses and emotional detachment, including the temporoparietal junction, which has been previously associated with depersonalization (Lanius et al., 2005; Harricharan et al., 2016).”

The posterior insula is thought to be important for receiving raw internal viscerosensory information related to interoceptive sensory processing, while the temporoparietal junction is thought to be involved in understanding one's self-location in external space.

“Whereas the posterior insula is thought to be important for receiving raw internal viscerosensory information related to interoceptive sensory processing, the temporoparietal junction is thought to be involved in understanding one’s self-location in external space (Craig, 2003; Lanius et al., 2005; Heydrich and Blanke, 2013; Simmons et al., 2013; Suzuki et al., 2013).”

Individuals with PTSD + DS exhibit increased v/l PAG functional connectivity with OP2 and TPJ, primary vestibular-multisensory processing regions associated with depersonalization symptoms.

“Alternatively, individuals with PTSD + DS exhibited increased v/l PAG functional connectivity with OP2 and TPJ, primary vestibular-multisensory processing regions ( Ibitoye et al., 2022 ) associated with depersonalization symptoms ( Lanius et al., 2005 ; Harricharan et al., 2017 ).”