Negative
emotions, anxiety and depression are thought to promote the onset of
neurodegenerative diseases and dementia. But what is their impact on the
brain and can their deleterious effects be limited? Neuroscientists
observed the activation of the brains of young and older adults when
confronted with the psychological suffering of others. The neuronal
connections of the older adults show significant emotional inertia:
negative emotions modify them excessively and over a long period of
time, particularly in the posterior cingulate cortex and the amygdala,
two brain regions strongly involved in the management of emotions and
autobiographical memory. These results, to be published in Nature Aging, indicate that a better management of these emotions - through meditation for example - could help limit neurodegeneration.
For
the past 20 years, neuroscientists have been looking at how the brain
reacts to emotions. ‘‘We are beginning to understand what happens at the
moment of perception of an emotional stimulus,’’ explains the last
author of this study. ‘‘However, what happens afterwards remains a
mystery. How does the brain switch from one emotion to another? How does
it return to its initial state? Does emotional variability change with
age? What are the consequences for the brain of mismanagement of
emotions?’’
Previous
studies in psychology have shown that an ability to change emotions
quickly is beneficial for mental health. Conversely, people who are
unable to regulate their emotions and remain in the same emotional state
for a long time are at higher risks of depression. ‘‘Our aim was to
determine what cerebral trace remains after the viewing of emotional
scenes, in order to evaluate the brain’s reaction, and, above all, its
recovery mechanisms. We focused on the older adults, in order to
identify possible differences between normal and pathological ageing,’’
says a co-lead of this work.
The
scientists showed volunteers short television clips showing people in a
state of emotional suffering - during a natural disaster or distress
situation for example - as well as videos with neutral emotional
content, in order to observe their brain activity using functional MRI.
First, the team compared a group of 27 people over 65 years of age with a
group of 29 people aged around 25 years. The same experiment was then
repeated with 127 older adults.
‘‘Older
people generally show a different pattern of brain activity and
connectivity from younger people,’’ says the first author of this work.
‘‘This is particularly noticeable in the level of activation of the
default mode network, a brain network that is highly activated in
resting state. Its activity is frequently disrupted by depression or
anxiety, suggesting that it is involved in the regulation of emotions.
In the older adults, part of this network, the posterior cingulate
cortex, which processes autobiographical memory, shows an increase in
its connections with the amygdala, which processes important emotional
stimuli. These connections are stronger in subjects with high anxiety
scores, with rumination, or with negative thoughts.’’
However,
older people tend to regulate their emotions better than younger
people, and focus more easily on positive details, even during a
negative event. But changes in connectivity between the posterior
cingulate cortex and the amygdala could indicate a deviation from the
normal ageing phenomenon, accentuated in people who show more anxiety,
rumination and negative emotions. The posterior cingulate cortex is one
of the regions most affected by dementia, suggesting that the presence
of these symptoms could increase the risk of neurodegenerative disease.
‘‘Is
it poor emotional regulation and anxiety that increases the risk of
dementia or the other way around? We still don’t know,’’ says the
author. ‘‘Our hypothesis is that more anxious people would have no or
less capacity for emotional distancing. The mechanism of emotional
inertia in the context of ageing would then be explained by the fact
that the brain of these people remains ‘frozen’ in a negative state by
relating the suffering of others to their own emotional memories.”
Could
it be possible to prevent dementia by acting on the mechanism of
emotional inertia? The research team is currently conducting an 18-month
interventional study to evaluate the effects of foreign language
learning on the one hand, and meditation practice on the other. ‘‘In
order to further refine our results, we will also compare the effects of
two types of meditation: mindfulness, which consists of anchoring
oneself in the present in order to concentrate on one’s own feelings,
and what is known as ‘compassionate’ meditation, which aims to actively
increase positive emotions towards others,’’ the authors add.
https://www.nature.com/articles/s43587-022-00341-6
http://sciencemission.com/site/index.php?page=news&type=view&id=publications%2Fexposure-to-negative&filter=22