Delusional thinking is a complex phenomenon often associated with various neuropsychiatric disorders, including schizophrenia, Alzheimer’s disease, and substance-induced psychoses. Understanding the neurobiological underpinnings of delusions involves examining specific brain regions, neurotransmitter systems, and cognitive processes that contribute to the formation and maintenance of these fixed false beliefs.
Research indicates that delusions may arise from aberrant salience attributed to stimuli, which is often linked to dysregulation in dopaminergic pathways, particularly in the mesolimbic system. The aberrant salience hypothesis posits that chaotic disinhibition of dopamine release leads to the misattribution of significance to otherwise neutral stimuli, fostering delusional beliefs (Hayashi et al., 2021; Mishara & Fusar‐Poli, 2013). This is supported by findings that show increased activation in the ventral striatum during delusional experiences, suggesting that motivational and reward-related processes are involved in the reinforcement of these beliefs (Raij et al., 2018; Arjmand et al., 2020). Furthermore, neuroimaging studies have demonstrated that individuals with persecutory delusions exhibit heightened activation in the medial temporal lobe when processing negatively valenced stimuli, indicating a potential neural basis for the emotional and cognitive aspects of delusions (Perez et al., 2015).
In the context of Alzheimer’s disease, delusions are often linked to cognitive deficits, particularly memory impairments. Studies have shown that patients with Alzheimer’s frequently exhibit delusions alongside memory deficits, which may stem from a failure to accurately recall information, leading to the formation of erroneous beliefs (Sultzer et al., 2014; Ismail et al., 2011). Neurobiological correlates such as decreased blood flow and metabolic activity in the frontal and temporal lobes have been associated with the prevalence of delusions in this population (Lai et al., 2017; Nomura et al., 2012). Moreover, the presence of neurovascular dysfunction and blood-brain barrier permeability issues has been proposed as contributing factors to the neurobiology of delusions in various psychiatric conditions, including schizophrenia and Alzheimer’s (Najjar et al., 2017; Prasad, 2019).
The right hemisphere of the brain has also been implicated in the manifestation of delusions. Research suggests that lesions or dysfunctions in the right hemisphere may disrupt the processes involved in reality testing and belief updating, leading to the persistence of delusional beliefs despite contradictory evidence (Gurin & Blum, 2017). This aligns with the two-factor theory of delusions, which posits that the initial neuropsychological impairment that prompts a delusion is compounded by a second impairment that hinders belief evaluation processes (Coltheart, 2010).
In summary, delusional thinking is associated with a variety of neurobiological factors, including dopaminergic dysregulation, temporal lobe dysfunction, and right hemisphere involvement. These factors interact with cognitive processes, such as memory and belief evaluation, to contribute to the persistence of delusions across different psychiatric disorders. Further research is needed to elucidate the complex interplay between these neurobiological and cognitive mechanisms, which could inform more effective treatment strategies for individuals experiencing delusions.
References
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