A neuroscientific perspective
Similar to emotional processing and perceptual reasoning, neurobiological theories of attention disorders in FND patients are based on a model of predictive processing, where functional symptoms are the result of a strong influence of abnormal prior information accompanied by an abnormal distribution of attention. This mechanism can in turn explain motor, sensory, cognitive and interoceptive phenomena (Drane et al., 2020; Teufel and Fletcher, 2020; Věchetová et al., 2023).
In Bayes' formulation, attention to a symptom with a strong prior belief in its presence overrides the actual sensory input and causes the overall perception to be consistent with the symptom itself (Huys et al., 2021).
Patients with FND often report cognitive symptoms such as problems with memory, concentration, sustained and selective attention (Teodoro et al., 2017), which may represent comorbid functional symptoms per se or may be due to an abnormal focus of attention on motor symptoms and the body. All of these can lead to an overload of working memory and result in poorer well-being, pain and fatigue (Věchetová et al., 2023).
Despite some studies investigating attention in patients with mFND (Huys et al., 2021; Voon et al., 2013), our understanding of cognitive symptoms and their neuropsychological correlates is still limited, as attention and other cognitive processes have not been studied using a standardized neuropsychological battery.
In a recent study, Věchetová and colleagues (2023) examined the cognitive abilities of patients diagnosed with mFNM using a neuropsychological battery of tests including:
a) attention, together with processing speed;
(b) executive functions, together with working memory;
(c) memory;
d) speech and language; and;
e) visual-spatial skills.
They found impaired subjective and objective functioning (attention, executive functions, and speech and language) in patients with mFNM, independent of depressive symptoms and effort deficit. The results of this study suggest and support the hypothesis of attentional impairment in patients and refute that excessive attention to symptoms is merely a consequence of psychiatric comorbidity, as it can be objectively measured, while impairments in attention are an integral part of motor functional impairment.
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Alluri, P. R., Solit, J., Leveroni, C. L., Goldberg, K., Vehar, J. V., Pollak, L. E., ... and Perez, D. L. (2020). Cognitive complaints in motor functional neurological (conversion) disorders: a focused review and clinical perspective. Cognitive and Behavioral Neurology, 33(2), 77-89.
Brown, H., Adams, R. A., Parees, I., Edwards, M., and Friston, K. (2013). Active inference, sensory attenuation and illusions. Cognitive processing, 14, 411-427.
de Vroege, L., Koppenol, I., Kop, W. J., Riem, M. M., and van der Feltz-Cornelis, C. M. (2021). Neurocognitive functioning in patients with conversion disorder/functional neurological disorder. Journal of Neuropsychology, 15(1), 69-87.
Drane, D. L., Fani, N., Hallett, M., Khalsa, S. S., Perez, D. L., and Roberts, N. A. (2021). A framework for understanding the pathophysiology of functional neurological disorder. CNS Spectrums, 26(6), 555-561.
Huys, A. C. M., Haggard, P., Bhatia, K. P., and Edwards, M. J. (2021). Misdirected attentional focus in functional tremor. Brain, 144(11), 3436-3450.
Pareés, I., Brown, H., Nuruki, A., Adams, R. A., Davare, M., Bhatia, K. P., ... and Edwards, M. J. (2014). Loss of sensory attenuation in patients with functional (psychogenic) movement disorders. Brain, 137(11), 2916-2921.
Perez, D. L., Nicholson, T. R., Asadi-Pooya, A. A., Bègue, I., Butler, M., Carson, A. J., ... and Aybek, S. (2021). Neuroimaging in functional neurological disorder: state of the field and research agenda. NeuroImage: Clinical, 30, 102623.
Teodoro, T., Edwards, M. J., and Isaacs, J. D. (2018). A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: a systematic review. Journal of Neurology, Neurosurgery & Psychiatry, 89(12), 1308-1319.
Teufel, C., and Fletcher, P. C. (2020). Forms of prediction in the nervous system. Nature Reviews Neuroscience, 21(4), 231-242.
Věchetová, G., Nikolai, T., Slovák, M., Forejtová, Z., Vranka, M., Straková, E., ... Attention impairment in motor functional neurological disorders: a neuropsychological study. Journal of neurology, 269(11), 5981-5990.