Amyloid beta peptide is an important biomarker in Alzheimer’s disease, with the amyloidogenic hypothesis as one of the central hypotheses trying to explain this type of dementia. Despite numerous studies, the etiology of Alzheimer’s disease remains incompletely known, as the pathological accumulation of amyloid beta aggregates cannot fully explain the complex clinical picture of the disease. Or, for the development of effective therapies, it is mandatory to understand the roles of amyloid beta at the brain level, from its initial monomeric stage prior to aggregation in the form of senile plaques. In this sense, this review aims to bring new, clinically relevant data on a subject intensely debated in the literature in the last years. In the first part, the amyloidogenic cascade is reviewed and the possible subtypes of amyloid beta are differentiated. In the second part, the roles played by the amyloid beta monomers in physiological and pathological (neurodegenerative) conditions are illustrated based on the most relevant and recent studies published on this topic. Finally, considering the importance of amyloid beta monomers in the pathophysiology of Alzheimer’s disease, new research directions with diagnostic and therapeutic impacts are suggested.

Cognitive decline is a frequent complaint in healthy controls and neurological patients, regardless of the underlying pathology. Whilst cognitive impairment can be easily diagnosed in the more advanced stages of neurodegenerative diseases, early detection can be challenging. This is mainly the consequence of the incomplete understanding of the underlying pathophysiological mechanisms. In addition, currently available neurological treatments do not specifically target cognitive decline, since other motor and non‑motor symptoms, such as bradykinesia, tremor, autonomic disturbances and depression, are of greater relevance from a therapeutic perspective. In this context, prospective studies must address a number of issues, including the risk factors associated with cognitive deficits in neurodegenerative diseases. The present review aims to offer a novel perspective on the association between Epstein‑Barr virus infection and cognitive decline found in patients with neurodegenerative disorders. Specifically, relevant epidemiological studies and clinical trials explaining this connection were reviewed, focusing on the most frequent neurodegenerative disorders. They are namely Alzheimer's disease, Parkinson's disease and multiple sclerosis. Despite their limitations, possible underlying pathophysiological mechanisms that explain the impact of Epstein‑Barr virus infection on cognitive decline are expected to offer novel study directions on this clinically relevant topic.

Cognitive impairment is one of the most significant burdens among the many neurological complaints in multiple sclerosis patients. Cognitive deficits negatively impact these patients’ quality of life, leading to partial or total loss of several mental functions, such as learning, memory, perception, or problem-solving. While the precise mechanisms involved in the onset and evolution of cognitive decline remain unknown, several risk factors have been associated with intellectual disability. With increasing data on this topic in recent years, the main aim of this review is to summarize the most relevant risk factors correlated with cognitive impairment in multiple sclerosis patients. Firstly, the authors demonstrate the importance of mental disability based on epidemiological data from multiple sclerosis patient cohorts. Subsequently, the intensely debated major risk factors for cognitive decline are discussed, with brief insights into the pathophysiology and possible underlying mechanisms. Finally, the authors describe the impact of medication on cognitive impairment in multiple sclerosis patients, highlighting the main research directions for future studies.