Decrease in stereognostic ability of the tongue with age

The Feel of Speech: Multisystem and Polymodal Somatosensation in Speech Production

PURPOSE

The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production.

METHOD

The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience.

RESULTS AND CONCLUSIONS

The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders.

Evaluation of the neuromotor ability of the tongue in pediatric patients using a stereognostic examination

BACKGROUND

The term "stereognosis" comes from neurology and describes the capacity to distinguish objects solely by touch.

AIM

The aim of this research study was to compare the neuromotor ability of the tongue in patients with malocclusion and tongue dysfunction with and without superficial anesthesia on the tip of the tongue and hard palate.

MATERIALS AND METHODS

The study included 132 patients aged 6-13 years. Using a spatula for speech therapy and a visual evaluation while swallowing saliva, all individuals were identified as having swallowing dysfunctions and divided into three groups: study group (children with malocclusions and tongue dysfunctions) - 44 patients, comparator group (children with malocclusions and without tongue dysfunctions) - 44 patients, and control group (children without malocclusions or tongue dysfunctions) - 44 patients. The Koczorowski methods were used for the stereognostic tests.

RESULTS

Age, sex, and malocclusion were taken into account during the differential analysis. The study and comparison groups, study and control groups, and the comparator and control groups all showed statistically significant differences from one another. According to the results, tongue dysfunction affects patients' ability to coordinate their movements with their senses at a developing stage.

CONCLUSION

Patients with malocclusions that are made worse by tongue dysfunctions have poorer oral stereognostic sensibility. Speech therapy and interdisciplinary specialist orthodontic treatment are required for individuals with impaired oral perception who are still in the developmental stage and have abnormal tongue position and function.

Palatal coverage and oral stereognosis: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Complete denture wearers present with less sensory function than dentate individuals because of the loss of periodontal receptors. However, the role of the palatal receptors on such function is still unclear.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the influence of palatal coverage associated with complete dentures or palatal devices on oral stereognosis in edentulous or dentate adults.

MATERIAL AND METHODS

Eight major literature databases and the nonpeer-reviewed literature were searched up to December of 2021. Randomized clinical trials and nonrandomized clinical trials comparing oral stereognosis in edentulous or dentate participants using conventional complete dentures or implant-supported prostheses or those using palatal devices were included. Bias was assessed with Cochrane tools (ROBINS-I and RoB 2.0). Meta-analyses were conducted to compare oral stereognosis before and after palatal coverage (α=.05). Certainty of the evidence was verified using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

RESULTS

Of 14 included studies, the risk of bias was considered low for 9 studies and moderate for 5 studies. Despite the very low certainty of evidence, meta-analyses showed no differences in oral stereognosis immediately after complete denture insertion (standardized mean difference [SMD]=0.302; 95% confidence interval [CI]: -0.124, 0.728; P=.165; I2=92.4%). Oral stereognosis scores improved after ≥1 month of complete denture use compared with initial evaluations without them. Qualitative analysis indicated that oral stereognosis was not influenced by palatal coverage shortly after complete denture installation and that oral stereognosis scores improved over time after prosthesis use.

CONCLUSIONS

Oral stereognosis improved with the use of palate-covering prostheses over time. However, because of the very low certainty of evidence, the statement must be interpreted with caution.

Beyond language: The unspoken sensory-motor representation of the tongue in non-primates, non-human and human primates

The English idiom "on the tip of my tongue" commonly acknowledges that something is known, but it cannot be immediately brought to mind. This phrase accurately describes sensorimotor functions of the tongue, which are fundamental for many tongue-related behaviors (e.g., speech), but often neglected by scientific research. Here, we review a wide range of studies conducted on non-primates, non-human and human primates with the aim of providing a comprehensive description of the cortical representation of the tongue's somatosensory inputs and motor outputs across different phylogenetic domains. First, we summarize how the properties of passive non-noxious mechanical stimuli are encoded in the putative somatosensory tongue area, which has a conserved location in the ventral portion of the somatosensory cortex across mammals. Second, we review how complex self-generated actions involving the tongue are represented in more anterior regions of the putative somato-motor tongue area. Finally, we describe multisensory response properties of the primate and non-primate tongue area by also defining how the cytoarchitecture of this area is affected by experience and deafferentation.

Evaluation of the Association of Oral Stereognosis with Malocclusion in Children

Aim and objective

To evaluate the association between oral stereognosis with malocclusion in children.

Materials and methods

Stereognostic investigation was made with a set of seven different geometric configurations (circle, square, triangle, star, clover, diamond, and heart shapes) cut out from fresh, raw carrots using preformed iron molds. Any five of the seven geometric forms were randomly placed inside the mouth on the dorsum of the tongue by the investigator with the subject's eyes closed. A minimum of three shapes correctly identified out of the five offered to each child was considered as an indicator of the adequate stereognostic ability of that particular child.

Results

Among the children under Index of Orthodontic Treatment Needs (IOTN) grade I group, 82.4% of children came under the positive response group. Among IOTN grades II, III, and IV, the percentages of children with positive responses were 72.1%, 58.1%, and 18.8%, respectively. There is a statistically significant (p < 0.001) decrease in positive response with increasing IOTN grades.

Conclusion

The observations from the present study show that there is altered oral sensory perception in children graded as with malocclusion according to the index used and belonging to the age group selected in the study.

Clinical significance

Sensory and motor components of the orofacial region, like any other part of the human body, are inseparable in their structure and function, the association between orofacial growth and development and sensory maturation cannot be overlooked.

How to cite this article

Janardhanan R, Soman A, George S, et al. Evaluation of the Association of Oral Stereognosis with Malocclusion in Children. Int J Clin Pediatr Dent 2021;14(S-1):S18–S21.

Relationship between oral stereognostic ability and dietary intake in older Japanese adults with complete dentures

PURPOSE

Oral stereognostic ability (OSA) is a useful indicator of oral perception to recognize food characteristics during mastication. Previous studies have shown associations between dietary intake and oral health status, such as taste perception. However, the effect of oral sensory ability on dietary intake is unclear. The purpose of this study was to investigate the association between oral sensory ability and dietary intake in older Japanese complete denture wearers.

METHODS

This cross-sectional study included 164 participants aged 69-71 or 79-81years old, wearing both maxillary and mandibular complete dentures. OSA test was used to evaluate oral tactile perception. Diet during the preceding month was assessed using a self-administered diet history questionnaire. Multivariable linear regression analysis was conducted to assess the association between OSA score and food and nutrient intake after adjusting for age, sex, socioeconomic factors, and occlusal force.

RESULTS

The bivariate analysis showed that OSA score was significantly and positively correlated with intake of green and yellow vegetables and negatively correlated with intake of cereals among examined foods. OSA score was also positively correlated with intake of vitamins A, B₂, and C and α-tocopherol (as a substitute for vitamin E) among examined nutrients. After adjusting for age, sex, socioeconomic factors, and occlusal force, OSA score remained significantly associated with intake of green and yellow vegetables and α-tocopherol.

CONCLUSIONS

OSA was significantly associated with intake of green and yellow vegetables in older complete denture wearers.

Somatosensory innervation of the oral mucosa of adult and aging mice

Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner’s corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.

Somatosensory innervation of the oral mucosa of adult and aging mice

Oral mechanoreception is implicated in fundamental functions including speech, food intake and swallowing; yet, the neuroanatomical substrates that encode mechanical stimuli are not well understood. Tactile perception is initiated by intricate mechanosensitive machinery involving dedicated cells and neurons. This signal transduction setup is coupled with the topology and mechanical properties of surrounding epithelium, thereby providing a sensitive and accurate system to detect stress fluctuations from the external environment. We mapped the distribution of anatomically distinct neuronal endings in mouse oral cavity using transgenic reporters, molecular markers and quantitative histomorphometry. We found that the tongue is equipped with an array of putative mechanoreceptors that express the principal mechanosensory channel Piezo2, including end bulbs of Krause innervating individual filiform papillae and a novel class of neuronal fibers innervating the epithelium surrounding taste buds. The hard palate and gums are densely populated with three classes of sensory afferents organized in discrete patterns including Merkel cell-neurite complexes, Meissner's corpuscles and glomerular corpuscles. In aged mice, we find that palatal Merkel cells reduce in number at key time-points that correlate with impaired oral abilities, such as swallowing and mastication. Collectively, this work identifies the mechanosensory architecture of oral tissues involved in feeding.

Impact of cognitive function on oral perception in independently living older people

OBJECTIVES

Oral tactile perception is important for better mastication, appetite, and enjoyment of food. However, previous investigations have not utilized comprehensible variables thought to have negative effect on oral perception, including aging, denture wearing, and cognitive function. The aim of this study was to elucidate the impact of cognitive function on oral perception in independently living older individuals.

MATERIALS AND METHODS

The study sample was comprised of 987 participants (466 males, 521 females; age 69-71 years). Oral examinations, assessments of cognitive function in preclinical level by Montreal Cognitive Assessment (MoCA)-J, and determination of oral stereognostic ability as an indicator of oral perception were performed. Related variables were selected by univariate analyses; then, multivariate logistic regression model analysis was conducted.

RESULTS

Univariate analyses revealed that number of teeth, removable dentures usage, and cognitive function respectively had a significant relationship with stereognostic score. Next, the subjects were classified into good and poor perception groups (lowest 17.4%) according to oral stereognostic ability. Logistic regression analysis revealed that lower cognitive function was significantly associated with poor oral perception (OR = 0.934, p = 0.017) after controlling for other variables.

CONCLUSIONS

Cognitive decline even in preclinical stage was associated with reduced oral perception after controlling for gender, tooth number and denture use in independent living older people.

CLINICAL RELEVANCE

This study suggested that preclinical level of change in cognitive function affected oral perception. Dental practitioners and caregivers may need to pay attention to reduced oral perception among older people even if they do not have trouble in daily life.

Características orofaciais de idosos funcionalmente independentes

RESUMO Objetivo conhecer as características orofaciais de idosos funcionalmente independentes e analisar a associação com a idade, gênero, nível socioeconômico e estado dentário. Método estudo observacional, transversal de caráter analítico com amostra não probabilística. Foi aplicado o instrumento validado “Protocolo de Avaliação Miofuncional Orofacial com Escalas para Idoso” em sujeitos funcionalmente independentes com idade igual ou acima de 60 anos, em boas condições de saúde segundo avaliação geriátrica padronizada, intitulada Protocolo de Avaliação Multidimensional do Idoso. Resultados os idosos apresentaram padrões de normalidade acima de 60% nos parâmetros de aspecto e mobilidade das estruturas. As alterações significantes foram: sulco nasolabial acentuado; bochechas flácidas ou arqueadas; vedamento labial com tensão ou ausência de vedamento e comissuras labiais deprimidas. As alterações de mobilidade foram pequenas, entre 20,6% e 33,8%, com maior prevalência na elevação da língua e lateralização do ar em bochechas infladas e da mandíbula. Não houve relação destes achados perante a progressão da idade e as classes socioeconômicas. As mulheres apresentaram maior chance de exibirem aspecto normal dos lábios e alguma alteração da mobilidade. O número de dentes associou-se com o volume e a configuração dos lábios e a mobilidade da mandíbula. Além disso, o uso de prótese dentária associou-se significativamente com o aspecto do sulco nasolabial e a tensão/configuração das bochechas. Conclusão este trabalho sugere que o sistema oromiofacial encontra-se dentro dos padrões de normalidade na maioria dos idosos funcionalmente independentes. O que ampara a atuação multiprofissional na prevenção, promoção e tratamento da saúde oromiofuncional dos idosos.

Does shape discrimination by the mouth activate the parietal and occipital lobes? - near-infrared spectroscopy study

A cross-modal association between somatosensory tactile sensation and parietal and occipital activities during Braille reading was initially discovered in tests with blind subjects, with sighted and blindfolded healthy subjects used as controls. However, the neural background of oral stereognosis remains unclear. In the present study, we investigated whether the parietal and occipital cortices are activated during shape discrimination by the mouth using functional near-infrared spectroscopy (fNIRS). Following presentation of the test piece shape, a sham discrimination trial without the test pieces induced posterior parietal lobe (BA7), extrastriate cortex (BA18, BA19), and striate cortex (BA17) activation as compared with the rest session, while shape discrimination of the test pieces markedly activated those areas as compared with the rest session. Furthermore, shape discrimination of the test pieces specifically activated the posterior parietal cortex (precuneus/BA7), extrastriate cortex (BA18, 19), and striate cortex (BA17), as compared with sham sessions without a test piece. We concluded that oral tactile sensation is recognized through tactile/visual cross-modal substrates in the parietal and occipital cortices during shape discrimination by the mouth.

The perception of materials through oral sensation

This paper presents the results of a multimodal study of oral perception conducted with a set of material samples made from metals, polymers and woods, in which both the somatosensory and taste factors were examined. A multidimensional scaling analysis coupled with subjective attribute ratings was performed to assess these factors both qualitatively and quantitatively. The perceptual somatosensory factors of warmth, hardness and roughness dominated over the basic taste factors, and roughness was observed to be a less significant sensation compared to touch-only experiments. The perceptual somatosensory ratings were compared directly with physical property data in order to assess the correlation between the perceived properties and measured physical properties. In each case, a strong correlation was observed, suggesting that physical properties may be useful in industrial design for predicting oral perception.

Rate-related kinematic changes in younger and older adults

AIMS

This study aimed to investigate the effects of speech rate changes on kinematic characteristics and stability of speech movements in younger and older speakers using electromagnetic midsagittal articulography.

PATIENTS AND METHODS

Eight young adults and 8 older adults engaged in a series of syllable repetition tasks of /pa/, /sa/ and /ta/ obtained at self-paced slow, habitual and fast speech rates, as well as in a series of metronome-guided speech rates, ranging from 2 to 4 syllables per second. The kinematic parameters duration, amplitude and peak velocity were obtained for opening and closing movements.

RESULTS

Older speakers were able to increase speech rate to the same degree or higher compared to younger speakers in both pacing conditions. Kinematic data show that older adults increased duration and decreased peak velocity in closing movements of alveolar constrictions at slower rates more prominently than younger adults. The results on movement stability revealed no differences between age groups.

CONCLUSIONS

The results suggest that an age-related difference in speed-accuracy trade-off can be ruled out. Differences in kinematic characteristics point towards the possibility that older adults aimed to facilitate a closed-loop control system to maintain movement stability at slower speech rates.

Sensory input pathways and mechanisms in swallowing: a review

Over the past 20 years, research on the physiology of swallowing has confirmed that the oropharyngeal swallowing process can be modulated, both volitionally and in response to different sensory stimuli. In this review we identify what is known regarding the sensory pathways and mechanisms that are now thought to influence swallowing motor control and evoke its response. By synthesizing the current state of research evidence and knowledge, we identify continuing gaps in our knowledge of these mechanisms and pose questions for future research.