There are two worrying features of Alzheimer's disease: it is
highly prevalent
(it is estimated to affect 50 million people globally, rising to 132 million by 2050), and
it has no cure
.
A third could be added: its cruelty.
The memory failure usually progresses, and increases until the person stops recognizing
even their loved ones
.
Taking all this into account, prevention becomes one of the most important facets.
Early detection
is
also an aspiration, since it allows us to get started sooner, and treatments generally come to a better conclusion.
A new study co-authored by researchers from MIT, Cornell University and Massachusetts General Hospital provides clues so that people and their environment can be on the lookout for
early signs
of Alzheimer's disease.
Language as a way of entry
At the end of 2022,
Clarín
published an interview with neuroscientist Adolfo García, director of the Center for Cognitive Neurosciences at the University of San Andrés, fellow of the
Global Brain Health Institute
at the University of California, and researcher at the University of Santiago de Chile and from CONICET;
in which he explained the importance of language as a
tool to spy on
the integrity of certain brain circuits.
“Different brain diseases associated with aging, such as neurodegenerative diseases, Alzheimer's, Parkinson's, or frontotemporal dementia;
“They are characterized by patterns of atrophy, or molecular alterations, or
connectivity alterations
in different regions of the brain,” he stated.
And he continued reflecting: “When we understand the brain basis of different
linguistic activities
, that certain words rely on some circuits, that certain grammatical constructions depend on others, that certain pronunciation skills depend on others;
We can start to think 'If I know that Alzheimer's is characterized by certain types of alterations, that those linguistic abilities resort mainly to certain regions, won't I be able to use those linguistic tests to see if those regions are functioning well or poorly?'” .
In this context, according to the new study, published in the
Journal of Neurolinguistics
- and in which García did not participate - memory loss used to be conceived as an indicator of amnestic mild cognitive impairment.
According to his findings,
language processing
difficulties are also important.
They found that people with mild cognitive impairment had difficulty processing certain ambiguous sentences.
Photo Shutterstock.
While it is true that people with mild cognitive impairment (MCI), especially the "amnestic subtype," are at higher risk of dementia due to Alzheimer's disease compared to cognitively healthy older adults, the study has identified
a key deficit
in people with MCI, which is related to the production of complex language.
This deficit is
independent of the memory deficit
that characterizes this group and may provide an additional “cognitive biomarker” to aid in early detection – the time when treatments, as they continue to be developed, are likely to be most effective.
What is the production of a “complex” language?
The researchers found that while people with MCI could appreciate the basic structure of sentences (syntax) and their meaning (semantics), they had difficulty processing
certain ambiguous sentences
in which the pronouns referred to people who were not reference in the sentences themselves.
"These results are among the first to
address the complex syntax
and reach the abstract calculation involved in the processing of these linguistic structures," says MIT linguistics scholar Suzanne Flynn, co-author of a paper.
The increase in the prevalence of Alzheimer's disease is of concern.
Photo Shutterstock.
According to the researchers, it is
novel
to focus on the subtleties of language processing in relation to mild cognitive impairment and its possible transition to dementia such as Alzheimer's disease.
"Previous research has most often focused on individual words and vocabulary," adds co-author Barbara Lust, professor emeritus at Cornell University.
“We analyze a more complex level of language knowledge.
When we process a sentence, we have to grasp its syntax and construct meaning.
We find a breakdown at that higher level where you are integrating form and meaning.”
The study: the role of anaphora
To carry out the study, the academics conducted experiments in which
they compared the cognitive performance
of patients with mild impairment with that of cognitively healthy individuals in separate, younger and older control groups.
The study identified how well people process and reproduce sentences involving "anaphora."
In linguistic terms, this usually refers to the relationship between
a word and another form
in the sentence, such as the use of "his" in the sentence "The electrician repaired his equipment."
(The term “anaphora” has another related use in the field of rhetoric, which involves the repetition of terms.)
In the study, researchers ran a variety of sentence constructions on MCI patients and control groups.
For example, in the sentence “The electrician fixed the light switch when he visited the tenant,” it is actually not clear whether “he” refers to the electrician or someone else entirely.
The “he” could be a family member, a friend, or a landlord, among other possibilities.
The cognitive performance of individuals with mild cognitive impairment was compared with that of cognitively healthy individuals.
Photo Shutterstock.
On the other hand, in the sentence “He visited the tenant when the electrician was repairing the light switch,” “he” and the electrician cannot be the same person.
Alternatively, in the sentence “The babysitter emptied the bottle and prepared the formula,” there is no reference to a person beyond the sentence.
Ultimately, MCI patients performed
significantly worse
than control groups when producing sentences with “anaphoric coreference,” those with ambiguity about the identity of the person referred to by a pronoun.
The importance of context in sentence production
“It is not that patients with cognitive impairment have lost the ability to process syntax or put complex sentences together, or that they have lost words;
is that they are
showing a deficit
when the mind has to decide whether to stay in the sentence or get out of it, to discover who we are talking about,” Lust specifies.
And he clarifies: "When they did not have to go outside the sentence to look for context, sentence production was preserved in the mildly impaired individuals we studied."
For his part, and to highlight the importance of the finding, Flynn assures: “This contributes to our understanding of the deterioration that occurs in the early stages of the dementia process.
The deficits
go beyond
memory loss.”
And it explains that although the participants studied have memory deficits, their memory difficulties do not explain the research team's findings in language, as demonstrated by the lack of correlation in their performance in the language task and in the memory measures.
“This suggests that, in addition to the memory difficulties that people with MCI experience, they also
struggle with this
central aspect of language,” he ponders.
Searching for a path to treatment
The current paper is part of a series of ongoing studies that Flynn, Lust, Sherman, and their colleagues have conducted.
The findings have the potential to direct neuroscience studies toward brain regions that process language, investigating mild cognitive impairment and other forms of dementia, such as
primary progressive aphasia
.
The study may also help inform linguistic theory about various forms of anaphora.
Looking ahead, academics say they would like to increase the volume of studies as part of an effort to continue defining how diseases progress and
how language can predict it
.
"Our data is from a small population, but it is very theoretically oriented," Lust says.
“Hypotheses that are linguistically grounded are needed to make advances in neurolinguistics.
"There is a lot of interest in the years before the diagnosis of Alzheimer's disease, to see if its progression can be detected and stopped."
"The more precise we are about the
neural locus of impairment
, the more it will make a difference in terms of treatment development," Flynn concluded.
***
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