fMRI reveal Deficits in Emotion, Cognition, Memory and Sensori-motor Functions in patients of Dissociative Convulsions

Researchers in AIIMS, Delhi explored the neurobiological underpinnings of dissociative convulsions using a functional magnetic resonance imaging (fMRI) design targeting cognitive, affective, and resting state characteristics, and found that patients with dissociative convulsions have significant deficits in the areas associated with the processing of emotional, cognitive, memory, and sensory-motor functions.

Dissociative convulsion disorder has semiological similarities with epilepsy, which delays definitive diagnosis as well as treatment. The International Classification of Diseases ICD-10 defines dissociative convulsions as sudden and unexpected spasmodic movements, closely resembling any variety of epileptic seizures, but not followed by loss of consciousness and not accompanied by tongue-biting, Studies suggest an association with female gender, early age of onset, sexual as well as non-sexual traumatic exposures, anxiety symptoms, and higher scores on dissociation scales as compared to other dissociative motor symptoms.

Psychopathogenesis of dissociation can be understood using psychodynamic, social, and cognitive perspectives based on psychosocial theories. However, the underlying neurobiological changes and variability in physical manifestations in such patients are not understood. Persons with dissociative convulsions or PNES (PwDC) have higher difficulty in emotion regulation than healthy controls. These patients have working memory deficits and their attentional and mnemonic functions are impacted by stress and emotion regulation. Their cognitive performance is affected by emotional instability but is likely to have a better prognosis than epilepsy patients on cognitive parameters. Sub-cortical brain structures associated with cognition and emotion regulation have a role in the pathophysiology of dissociative convulsions as revealed by neuroimaging studies, which suggest the role of the non-dominant hemisphere in dissociation.

Functional magnetic resonance imaging (fMRI) studies have identified the involvement of circuits spanning the amygdala, cingulate cortex, middle frontal gyrus, dorsolateral prefrontal cortex (DLPFC), supplementary motor area (SMA), thalamic structures, and hippocampus suggesting an interaction of attention, memory, emotion, and motor control networks in patients with dissociative disorders.

In the current study published in Neuroloy India, Garg et al aimed to explore cognitive, affective as well as resting state characteristics of dissociation on fMRI in PwDC and compare these with the healthy controls. They designed the study to overcome the shortcomings of previous such studies by using a 3T MRI scanner, standardized images for the fMRI paradigm, excluding co-morbid epilepsy, psychiatric illness, and substance use, and ensuring homogeneity of sample cases.

They hypothesized that the functional networks associated with emotional and cognitive processing may be affected in PwDC disorder and may be correlated with the vulnerability to dissociate in such patients.

They found that PwDC are unable to process emotional stimuli adequately, which further leads to abnormal interaction with executive functions of planning, memory, attention, arousal, behavior control, and expression of emotions. This may eventually lead to varied sensory–motor manifestations including those resembling convulsions.

Their findings are contrary to increased activation in areas associated with emotion processing and attention–alertness in motor conversion disorder, which may be attributed to differences in dissociative disorder subgroups studied.

The results of rs-fMRI indicated greater connectivity between the left posterior superior temporal gyrus (involved in the perception of emotions in facial stimuli, social cognition, and language) and the left superior parietal lobule (involved in motor control and coordination, processing emotions during decision making and memory), among PwDC as compared to the healthy controls. This increased connectivity suggested that the processing of affective stimuli and stressful cues interferes with motor control-coordination pathways leading to physical manifestations such as convulsions in patients with dissociative disorder.

The team also found significantly higher connectivity between the precuneus (involved in self-awareness, consciousness, memory, and visuospatial coordination) and left angular gyrus (involved in visuospatial processing, behavior control, language, and arithmetic function), and left temporal fusiform cortex (involved in visual processing, face recognition, and memory function) in PwDC as compared to the healthy controls. This suggests that an increase in FC is associated with the phenomenon of altered consciousness and motor symptoms in PwDC disorder, in response to perceived stress or emotion or recall of distressing memories.

The reduced FC in patients in the study suggests deficits in emotional processing networks and their adverse interaction with somatosensory and executive functioning. Dissociative convulsions have an element of unresponsiveness (unlike dissociative motor symptoms) and may be attributed to deficits in emotion processing and neurocognition.

The findings suggest that PwDC has significant deficits in the areas associated with the processing of emotional, cognitive, memory, and sensory-motor functions. There is also a probable correlation between dissociative severity and the functioning of areas involving the processing of emotions, cognition, and memory.

Reference

fMRI Analysis of Dissociative Convulsions: A Case-Controlled Study

Harshit Garg, Pratap Sharan, Senthil S Kumaran, Rachna Bhargava, Bichitra N Patra, Manjari Tripathi

Neurology India, Vol. 71, No. 3, May-June 2023, pp. 476-486

DOI: 10.4103/0028-3886.378651