Abstract
Objective: During the COVID-19 pandemic, quarantine and
staying at home is advised. The social relationship between people has
become deficient, and human social
isolation (SI) has become the consequence of this situation. It was
shown that SI has made changes in hippocampal neuroplasticity, which
will lead to poor cognitive function and behavioral abnormalities. There
is a connection between SI,
learning, and memory impairments.
In addition, anxiety-like behavior and increased aggressive mood in
long-term isolation have been revealed during the COVID-19 outbreak.
Methods: Term searches was done in Google Scholar, Scopus,
ScienceDirect, Web of Science and PubMed databases as well as hand
searching in key resource journals from 1979–2020.
Results: Studies have shown that some drug administrations may
positively affect or even prevent social isolation consequences in
animal models. These drug
treatments have included opioid drugs, anti-depressants, Antioxidants,
and herbal medications. In addition to drug interventions,
there are non-drug treatments that
include an enriched environment, regular exercise, and music.
Conclusion: This manuscript aims to review improved
cognitive impairments induced by
SI during COVID-19.
Keywords: COVID-19, social isolation, learning and memory, anxiety, drug
treatments, non-drug treatments
Introduction
Social interaction has a crucial role in human well-being, both mentally
and physically (1). Human social isolation (SI) happens when
the social relationship between individuals become deficient (2).
Moreover, it mostly occurs when the number of individuals, who are
members of social links, decrease, or the qualification of social
relations, diminishes. During SI, people experience unpleasant
situations mentally, emotionally, and spiritually (3, 4). Some
conditions force individuals to leave human groups and reduce their
social interactions, presence in the population, and group activities.
Being single, getting a divorce and separation may also result in
isolation (2, 5). Further, weak connections and lack of social support
have shown to be significant risk factors of isolation, which result in
loneliness, stress, and committing suicide (6, 7). Meanwhile, some
infectious diseases like COVID-19, AIDS, and some physical disorders
have shown to develop SI in humans (8, 9).
Adverse effects on cognition and behavior, decision-making, and pain
perception are followed by social isolation (10, 11). SI has shown to
change the immune system, glutamate system, and hormones (12, 13).
Besides, cardiovascular disease, high blood pressure, stroke, and
developmental neurodegenerative diseases have occurred during SI (14).
Depression was also induced while motor dysfunction decreased during
isolation (15-17). Some evidence demonstrated more oxidative stress and
inflammation because of increased IL-1ß, cytokines, and brain
macrophages during SI (18). Isolation and loneliness lead to a higher
rate of morbidity, mortality, and it is strongly related to chronic
disease with death in adults (17, 19).
Previous researches have shown
there is a relation between SI and alternations in the hippocampus.
According to studies, changes in hippocampal neuroplasticity will lead
to poor cognitive function and behavioral abnormalities (20, 21). There
is a connection between SI, learning, and memory impairments as well.
Some studies have reported that environmental factors play a significant
role in brain development and cognitive function in rodents, which
directly affect learning and memory performance (22, 23). Results
suggest that SI as the lack of presence of others or the few numbers of
meaningful relationships is vastly associated with many aspects of
memory and learning impairment (24, 25). Morris Water Maze’s outcomes
have also shown spatial learning and memory dysfunction during isolation
(26, 27). Other studies have demonstrated inhibition of autophagy by the
production of some factors (28), deficit spatial learning and memory,
social recognition memory, reversal learning, and short-term memory
during SI periods (29). Alternatively, some studies have shown that
isolated environments did not affect spatial learning and memory,
spatial reference memory, reversal learning, and short-term memory.
Moreover, in some cases, results have suggested that memory and learning
performance has improved due to social isolation (28, 30).
Animal research indicated depression, anxiety-like behavior, and
increased aggressive mood in long-term isolation (31, 32). Moreover, the
time spent in the open arms of the Elevated plus Maze has decreased as a
consequence of higher anxiety (33). Chronic stress has taken place as a
feature of anxiety and depression.
The human species depends on social behavior and social interaction.
Being social helps humans survive and solve problems; while, weak social
interaction negatively affects social memory and sociability during SI
(34, 35). There has been a correlation between neuroendocrine disability
and impairments in neurogenesis of the hippocampus and decline in BDNF
expression (36).
The results have also revealed that SI has developed Alzheimer’s
disease, and it has exacerbated spatial learning impairment in aged mice
(37). Motor activity is not affected according to open field outcomes;
however, chronic stress during SI has shown to the deficit the motor
function in rodent models of Parkinson’s disease (38, 39).