The field of neuropsychological profile research in dementias is a prolific field, more and more interest is placed in knowing what are the defining characteristics of this nosological entity, understanding in depth how the different cognitive abilities are affected will help us to make early diagnoses in order to intervene in subjects and slow down or alleviate, as far as possible, the development and progression of the disease.

In this article we have focused on the higher cognitive capacity of language in order to analyze the characteristics of its impairment in people with dementia. The data show that language is affected in all modalities in the development of dementia, although there are some discrepancies in both the form and extent of the involvement. Therefore, we are facing a field, full of possibilities for future progress, which will allow us to be more accurate in diagnosis and more accurate in intervention.

The concept of mild cognitive impairment (MCI) was introduced in 1988 by Reisberg and defined in the scientific literature by Flicker and collaborators, although its interest was consolidated by a study carried out by the Mayo Clinic, a famous entity dedicated to clinical practice, education and research in the USA. MCI patients are at a stage between normal aging and dementia. Moreover, statistics show that 50% of people with MCI will develop one of the dementias. For this reason, it is important to know the signs and symptoms that characterize these pathologies, to refine the diagnosis and establish early intervention systems to stop the progression of these diseases.

Research on language as a detector of dementias

The study of language skills as a detector of dementias is one of the most fruitful fields in the effort to define the neuropsychological profile of the prodromal phase of dementias. The language skills studied so far are affected to varying degrees, giving a primary role to the study of naming and phonological and semantic fluency. Simultaneously, studies have been initiated on other linguistic dimensions that had not been of interest to scientists so far. In fact, most studies have focused on the lexical evaluation of subjects.

Gradually, paradigms such as “tip of the tongue” (TOT) are being incorporated into the studies, this phenomenon involves difficulty in remembering known words, characterized by the sensation that their recall may be imminent. Linguistic dimensions such as semantic and syntactic complexity of spontaneous and narrative language are also investigated. Furthermore, in the future it will be necessary to consider the opening of new fields and to analyze the relationships between language dimensions and other cognitive processes altered concurrently or secondarily.

Definition of the neuropsychological profile of language

In defining the neuropsychological profile of language, four modalities must be taken into consideration: oral expression, oral comprehension, written expression and written comprehension.

Oral expression

Oral expression is all communication that is carried out by means of speech. Among the different linguistic dimensions that can be evaluated within oral expression we can point out: naming, semantic verbal fluency, phonological verbal fluency and general verbal capacity.

Naming

Naming or ability to name visual stimuli can be quantitatively assessed with tests in which the individual is asked to name, using the most precise term possible, the image that appears in a set of pictures, the exploration of visual naming allows to observe and quantify a wide semiology, especially the presence of anosmia and paraphasic errors, substitution of some words for others, sometimes with the same sound, but with a different meaning.

Petersen in two studies in 1999 and 2009 points out that in patients who are beginning to develop any of the dementias, there is a progressive deterioration of naming abilities, in verb naming tasks, there is a continuous decrease, more errors occur in naming, especially paraphasias. On the other hand, both age and educational level have a significant effect on performance in this type of assessment.

Semantic and phonological verbal fluency

Phonological and semantic verbal fluency is considered very useful in neuropsychological assessment because of its easy and quick evaluation, verbal fluency is operationalized by measuring the number of words produced within a given category that can be evoked in a limited period of time, these tests are of the type, say as many words as you can that begin with the letter D or any other letter, or say as many words as you can within the category animals.

General verbal ability

General verbal ability consists of reasoning with verbal contents, establishing among them principles of classification, ordering, relationship and meaning. Likewise, in this parameter there are defects in the coherence of the speech, in the presence and maintenance of the central theme, in the repetition of the event, in the excessive use of pronouns and non-specific referents and in false starts and internal corrections in people who begin with the development of dementias. To assess the effectiveness of communication, it would be useful to measure its agility, naturalness, clarity, order, coherence, gesticulation, articulation, content and paralinguistic features of speech, such as; volume, tone, timbre, duration, speed, vocalizations: yawning, laughter, coughing, throat clearing, sighing, non-verbal codes, such as; gestures, body movements, distance, timing, sweating, blushing, gaze… In fact, none of these parameters is reviewed in the studies that have been carried out so far of those we have consulted.

Listening comprehension

Listening comprehension is an active skill, which sets in motion a series of linguistic and non-linguistic mechanisms. It involves developing the ability to listen in order to understand what others are saying. In addition, to evaluate this skill, the tests used would consist of the administration of oral commands, the transmission of stories after which comprehension would be evaluated through questions. People who begin with the development of dementia have more difficulty in correctly understanding irony and in general present worse performance in all tests assessing oral comprehension.

Written expression

Written expression consists of exposing, by means of conventional signs and in an orderly manner, any thought or idea, can be evaluated through a variant of the oral semantic and phonological naming tests, in this case the evaluation is done through a test with semantic and phonological key with pencil and paper. The results of studies of this dimension of language show that people who begin with the development of dementia write fewer correct words with the phonological evocation criteria, the same happens with the semantic evocation criteria, they also produce more perseverations, in short, there is a progressive deterioration of writing skills.

Written comprehension

Written comprehension is the ability to understand what is read, both in terms of the meaning of the words that make up a text and in terms of the overall comprehension of a written text. The tests used to assess this dimension consist of lexical decision tasks, in which, after reading a text, decisions must be made with respect to what the text asks of us, with which we can evaluate whether it has been understood, as well as word identification and reading aloud tests.

Certainly, in people who begin to develop dementia, there is evidence of a compromise in the processing of written language comprehension that makes it more difficult to understand lexical stimuli and that begin to emerge early in the initial stages of the disease. Moreover, in sentence recognition, worse performance is observed in all types of sentences in people who begin with the development of any of the dementias. Moreover, variability increases with increasing impairment in the case of nouns and propositional sentences that do not follow the syntactic order.

On the other hand, it is noted that in reading comprehension there is a continuous deterioration, finding statistically significant differences in reading aloud tests and in sentence and paragraph comprehension in the performance between people with normal aging and people who begin with the development of dementia.

Conclusions

In conclusion, the data available to us through research that has been done on the neuropsychological profile of cognitive language ability in dementias indicate that it is not yet entirely clear that the deficit in naming is due to difficulty in accessing the phonological content and not the semantic content of the concept, it is argued that a semantic representation of the word is produced but the transmitting impulse to the phonological representation is missing, since the individuals evaluated in one of the investigations were able to describe characteristics of the word they wanted to name but were not able to name it.

Speech as a predictor of dementia

What we can conclude is that naming tasks are good predictors of clinical groups that initiate with the development of dementias versus healthy individuals as pointed out to us by numerous investigations. (Petersen et al, 1999; Facal et al 2009; Carballo et al, 2015, Rodriguez, Facal and Juncos-Rabadán, 2008; and Hubner et al, 2017), taking into account that both the educational level and age of the individuals produce different results in the naming assessment.

Moreover, phonological and semantic fluency seem to have a fairly accurate discriminant value (Facal et al, 2009 and Carballo et al, 2015.).

General verbal ability is impaired in terms of expression at various extremes studied through discourse elicitation (Diggle et al, 2016 and Alonso-Sánchez et al 2018).

Oral comprehension as a predictor of dementias

Oral comprehension also seems to be compromised in the development of dementias, although we found conflicting results. Gaudreau et al, 2013 and Carballo et al, 2015, speak of compromised comprehension, but in Facal et al, 2009, they point out that comprehension is not impaired. Sometimes we do not understand, not because we do not understand the words uttered by our interlocutor, but because we do not know the context. For this reason, the structuring of this type of test should be considered.

Written expression as a predictor of dementia

In written expression, healthy groups evoke more words in both phonological and semantic criteria, there are also differences in the encoding of the different words evoked (Ruiz Sanchez de Leon et al, 2011; Carballo et al, 2015. Werner et al, 2006). Therefore, it would be worthwhile to have an impact on the study of the evolution in written expression, in the sense of determining what type of constructs can be used to discriminate between cognitively impaired and healthy individuals. In addition, we could evaluate the use of words morphologically, the use of syntax, spelling errors, gender, number… Characterize these tests with a deeper content than the simple fact of the number of words evoked.

Written comprehension as a predictor of dementia

Written comprehension has also been found to be impaired in patients with developing dementia (López-Higes et al, 2010. López-Higes et al, 2014. Hernández and Amórtegui, 2016. Carballo et al, 2015). Therefore, we could introduce different forms in this type of tests to locate which type of sentences are more difficult to determine or which are more sensitive to impairment, among enunciative, positive or negative, interrogative, exclamatory, exclamatory, exhortative, conditional, future….

The importance of the study of the neuropsychological profile of language in dementias lies in the implementation of accurate diagnostic procedures and thus to implement early intervention techniques in this capacity, adapting the training to the different dimensions that comprise human language. In fact, cognitive stimulation of this ability is a necessary and very useful tool to alleviate the deterioration of this skill that gives us the ability to understand and comprehend the speech of others, which favors the autonomy and independence of people. Moreover, through cognitive stimulation and neurorehabilitation tools we must train, exercise, maintain and preserve language as long as possible and with the best possible skill, expertise and fluency in people diagnosed with dementia as it will result in greater welfare and adaptation of these people.

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More references regarding language as a predictor of dementias

Juncos- Rabadan, O., Rodriguez, N., Facal, D., Cuba, J. y Pereiro, A. (2011). Tip of the tongue for proper namens in mild cognitive impairment. Semantic or post semantic impairments?. Journal of Neurolinguistics, 24, 636-651.

Juncos-Rabadán, O., Pereiro, A., Facal, D. y Rodriguez, N. (2009). Una revisión de la investigación sobre lenguaje en el deterioro cognitivo leve [A review of language research in mild cognitive impairment]. Revista de Logopedia, Foniatría y audiología, 30-2, 73-83

Juncos-Rabadán, O., Facal, D., Álvarez, M. y Rodriguez, M. (2006). El fenómeno de la punta de la lengua en el proceso de envejecimiento [The tip-of-the-tongue phenomenon in the aging process]. Psicothema , 18, 501-506.

Juncos-Rabadán, O., Pereiro, A., Alvarez, M. y Facal, D. (2006). Variabilidad en el acceso al lexico en el envjecimiento normal [Variability in lexical access in normal aging]. Revista de Logopedia, Foniatría y audiología, 26, 132-138.

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Lopez-Higes, R., Prados, J.M., Montejo, P., Montenegro, M. y Lozano, M., (2014). Is there a grammatical comprenhension deficit in multidomain mild cognitive impairment. Universitas Psychologica, 13(4), 1569-1579.

Lopez-Higes, R., Rubio, S., Martín, A. y del,Rio, D. (2010). Interindividual variability in vocabulary, sentence comprenshension and working memory in the el derly: effects of cognitive deterioration. The Spanish journal of Psychology, 13, 75-87.

Lopez-Higes, R., Rubio, S., Aragoneses, M. y del Rio, D. (2008). Variabilidad en la comprension grammatical en el envjecimiento normal [Variability in grammatical comprehension in normal aging]. Revista de Logopedía, foniatría y audiología,28, 15-27.

Macoir, J., Lafay, A. y Hudon, C. (2018) . Reduced lexical Access to verbs in individuals with subjetctive cognitive decline. American Journal of Alzheimer´s Disease and others Dementias XX (X). DOI:10.1177/1533317518790541

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More documentation about language and dementias

Ruiz Sanchez de León, J.M., Moratilla, P. y Llanero, M. (2011). Fluidez verbal escrita en el envejecimiento normal con quejas subjetivas de memoria y en el deterioro cognitive leve [Written verbal fluency in normal aging with subjective memory complaints and in mild cognitive impairment]. Anales de Psicología, 27, 360-368.

Rodriguez, N., Juncos-Rabadan, O. y Facal, D. (2008). El fenómeno de la punta de la lengua en el deterioro cognitivo leve [The tip-of-the-tongue phenomenon in mild cognitive impairment]. Un estudio piloto. Revista de logopedia, foniatría y audiología, 28, 28-33.

Subirana, J., Bruna, O., Puyuelo, M y Virgili, C. (2009). Lenguaje y funciones ejecutivas en la valoración incial del deterioro cognitivo leve y la demencia tipo Alzheimer [Language and executive functions in the initial assessment of mild cognitive impairment and Alzheimer’s type dementia]. Revista de logopedia, foniatría y audiología, 29. P. 13-20.

Taler, V. y Philips, N. A. (2008). Language performance in Alzheimer´s disease and mild cognitive impairment: A comparative review. Journal of Clinical and Experimental Neurosychology, 30, p. 501-556

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