Human-Related Emotional Stimuli Can Cause a Hippocampal and Thalamic Over-Response in People with Unstable Personalities

Abstract

Hippocampus is crucial for the formation of emotional memory. We found the relationship between hippocampal responses to emotional stimuli and the mental stabilities of people in our preliminary study. In this study, we have also evaluated how the emotional stimuli would affect amygdala and thalamus in the brain, and how the personality stabilities could relate to the responses in the brain using functional magnetic resonance imaging (fMRI). We evaluated the subjects' personality features with the Yatabe-Guilford Personality Test (Y-G test) and psychosomatic symptoms with the Cornell Medical Index (CMI). The subjects were categorized into the mentally stable group and the mentally unstable group according to the total scores of the Y-G test and the CMI. The brain functional responses under emotional stimuli were measured using fMRI. The region of interest (ROI) analysis was performed to abstract significant changes in order to compare responses among the different emotional stimuli. We conducted the regression analysis to abstract the relationship between the mean % signal change from fMRI and the personality stability. The fMRI results showed that the hippocampus, thalamus, and right amygdala activities under the human relationship stimuli increased with ascending value of mental instability. Our findings suggest that the memory process in the hippocampus and the threat alarm system in the thalamus under the human-related stimuli crucially influence the emotional reaction of mentally unstable people. These processes in the brain would affect the event that stresses on human relationships that often cause people to suffer from mental disorders.

An fMRI study of cognitive regulation of reward processing in generalized anxiety disorder (GAD)

“…It is worth mentioning that another explanation for these changes in FC might involve the thalamus directly. Studies have shown that hyperactivation of the thalamus might be associated with an increase in emotional distress and dysregulation (Geng et al, 2018;Mizuno-Matsumoto et al, 2013). Our results suggest that thalamus is recruiting dlPFC and vmPFC for regulation, as it is known to happen in other studies (Hutcherson et al, 2012).…”

Altered brain activation and connectivity during anticipation of uncertain threat in trait anxiety

“…Second, high anxious individuals showed stronger thalamus activation in the uncertain threat condition. Given the aforementioned role of the thalamus in rapid emotional processing, this finding suggests that when facing uncertain threat situations, high anxious individuals engage stronger and more rapid anticipatory emotional reaction (Mizuno‐Matsumoto et al, ). This statement is supported by previous behavioral studies which found that anxious individuals showed intense emotional reactions (i.e., startle) during the anticipation of uncertain threat than the certain condition (Grillon et al, ; Shankman et al, ).…”

“…We found that high anxious individuals showed stronger activations in the thalamus, PHA, dlPFC, and IPS, which are important for both emotional processing and cognitive control. The thalamus is a core hub in the ‘low road’ emotional path, which is critical for automatic processing of emotional stimulus (Mizuno‐Matsumoto et al, ; Pessoa & Adolphs, ). Increased activation of the thalamus in this study may indicate rapid “high‐way” emotional reaction during the anticipation of the future.…”

How do the parasympathetic nervous system and EEG respond to emotional memory recall?

“…When the emotional stimuli are treated in the brain, the pleasant and unpleasant emotional information could be processed in different ways . First, all kinds of emotional stimuli could be assessed to see whether the stimuli are pleasant or unpleasant in the amygdala.…”