Somatosensory Acuity Research Articles

Voluntary postural sway control and mobility in adults with low back pain.

Low back pain (LBP) is associated with altered somatosensory perception, which is involved in both involuntary and voluntary control of posture. Currently, there is a lack of methods and tools for assessing somatosensory acuity in patients with LBP. The purpose of this study was (1) to assess the reliability of the sway discrimination apparatus (SwayDA) (2) to evaluate the differences in somatosensory acuity between patients with LBP and pain-free individuals, and (3) to examine relationships between somatosensory acuity, severity of LBP, and mobility in patients with LBP. Twenty participants (10 patients with LBP and 10 matched asymptomatic controls) were recruited in a test-retest reliability test. Another 56 participants were recruited for this study with 28 individuals presenting with LBP and a further twenty-eight being asymptomatic. The SwayDA was custom-built to measure somatosensory perception during voluntary anterior-posterior (SwayDA-AP), medial-lateral to the dominant side (SwayDA-ML-D), and non-dominant side (SwayDA-ML-ND) postural sway control. Participants also completed mobility tests, including 10 times and 1-min sit-to-stand tests (10-STS, 1 m-STS). The area under the receiver operating characteristic curve (AUC) was calculated to quantify somatosensory acuity in discriminating different voluntary postural sway extents. The ICC (2.1) for the SwayDA-AP, SwayDA-ML-D, and SwayDA-ML-ND were 0.741, 0.717, and 0.805 with MDC95 0.071, 0.043, and 0.050. Patients with LBP demonstrated significantly lower SwayDA scores (tSwayDA-AP = -2.142, p = 0.037; tSwayDA-ML-D = -2.266, p = 0.027) than asymptomatic controls. The AUC values of the SwayDA-AP test were significantly correlated with ODI (rSwayDA-AP-ODI = -0.391, p = 0.039). Performances on the 1 m-STS and the 10-STS were significantly correlated with the AUC scores from all the SwayDA tests (-0.513 ≤ r ≤ 0.441, all p < 0.05). The SwayDA tests evaluated showed acceptable reliability in assessing somatosensory acuity during voluntary postural sway. Somatosensory acuity was diminished in patients with LBP compared to asymptomatic controls. In patients with LBP, lower somatosensory acuity was associated with increased LBP-related disability. Future research could focus on investigating the factors contributing to the decreased somatosensory perception and mobility in individuals with LBP.

The effect of compression and combined compression-tactile stimulation on lower limb somatosensory acuity

BackgroundLower limb somatosensation and proprioception are important for maintaining balance. Research has shown that compression garments or exposure to textured surfaces, can enhance somatosensation however, little is known about the effect of combined compression and texture on somatosensory acuity in the lower limb. This study aimed to assess the effects of combined compression socks with a plantar textured sole, on lower limb somatosensory acuity.MethodsThirty participants completed a somatosensory acuity task (active movement extent discrimination apparatus; AMEDA) under three conditions: barefoot (control condition), standard knee-high compression sock (compression sock), and knee-high compression sock with internal rubber nodules situated on the sole (textured-compression sock). Somatosensory acuity was assessed between the different sock conditions for the (i) entire group, (ii) high performers, and (iii) low performers. It was hypothesized that low performers would see gains wearing either sock, but the greatest improvement would be in the textured-compression sock condition.ResultsAMEDA scores were not significantly different between conditions when the entire group was analyzed (p = 0.078). The low performers showed an improvement in somatosensory acuity when wearing the compression sock (p = 0.037) and the textured compression sock (p = 0.024), when compared to barefoot, but there was no difference between the two sock conditions (p &amp;gt; 0.05). The high performers did not show any improvement (p &amp;gt; 0.05 for all).ConclusionThese findings demonstrate that additional sensory feedback may be beneficial to individuals with lower baseline somatosensory acuity but is unlikely to provide benefit for those with higher somatosensory acuity.

Reinforcement Motor Learning After Cerebellar Damage Is Related to State Estimation.

Recent work showed that individuals with cerebellar degeneration could leverage intact reinforcement learning (RL) to alter their movement. However, there was marked inter-individual variability in learning, and the factors underlying it were unclear. Cerebellum-dependent sensory prediction may contribute to RL in motor contexts by enhancing body state estimates, which are necessary to solve the credit-assignment problem. The objective of this study was to test the relationship between the predictive component of state estimation and RL in individuals with cerebellar degeneration. Individuals with cerebellar degeneration and neurotypical control participants completed two tasks: an RL task that required them to alter the angle of reaching movements and a state estimation task that tested the somatosensory perception of active and passive movement. The state estimation task permitted the calculation of the active benefit shown by each participant, which is thought to reflect the cerebellum-dependent predictive component of state estimation. We found that the cerebellar and control groups showed similar magnitudes of learning with reinforcement and active benefit on average, but there was substantial variability across individuals. Using multiple regression, we assessed potential predictors of RL. Our analysis included active benefit, somatosensory acuity, clinical ataxia severity, movement variability, movement speed, and age. We found a significant relationship in which greater active benefit predicted better learning with reinforcement in the cerebellar, but not the control group. No other variables showed significant relationships with learning. Overall, our results support the hypothesis that the integrity of sensory prediction is a strong predictor of RL after cerebellar damage.

Bovine Meissner-like corpuscle and evolutionary ecology of mammalian somatosensory acuity.

The mammalian snout has Meissner's corpuscles (MCs), which transmit epicritic sensations as the animal explores its surroundings. To comprehend the somatosensory acuity in mammals, we examined the structural organization and density of bovine Meissner-like corpuscles (BMLCs) at various ages and compared the changes with other mammalian MCs. The skin from the snout of cows or oxen (2-11 years old) was obtained and processed through routine histological technique. Five-μm thick sections were prepared, silver stained according to the Bielschowsky technique as modified by Winkelman and Schmidt (Mayo Clinic Proceedings, 1957, 217), and observed under a compound light microscope quantitatively and qualitatively. The glabrous skin of the cow snout consisted of two types of BMLCs: One was a cylindrical or elongated structure found in the dermal papillae. The other type was spherical and developed in the superficial layers of the epidermis. BMLCs consisted of both coarse and fine nerve fibres. In the young, the corpuscle comprised thin nerve fibres with indistinct cell outlines. In adults, nerve fibres in the corpuscles were closely packed, and networks, varicosities and end bulbs were well developed. With advancing age, the MCs attenuated into a disorganized mass of nerve fibres. The bovine snout is a highly evolved somatosensory organ due to its rich nerve supply and functionally resembles the anthropoid fingertip. Somatosensory acuity will be lower in the glabrous bovine skin than in primate glabrous skin of the fingertip, as the nerve terminals within the BMLCs are less elaborate in content and structural complexity.

Auditory and Somatosensory Development for Speech in Later Childhood.

This study collected measures of auditory-perceptual and oral somatosensory acuity in typically developing children and adolescents aged 9-15 years. We aimed to establish reference data that can be used as a point of comparison for individuals with residual speech sound disorder (RSSD), especially for RSSD affecting American English rhotics. We examined concurrent validity between tasks and hypothesized that performance on at least some tasks would show a significant association with age, reflecting ongoing refinement of sensory function in later childhood. We also tested for an inverse relationship between performance on auditory and somatosensory tasks, which would support the hypothesis of a trade-off between sensory domains. Ninety-eight children completed three auditory-perceptual tasks (identification and discrimination of stimuli from a "rake"-"wake" continuum and category goodness judgment for naturally produced words containing rhotics) and three oral somatosensory tasks (bite block with auditory masking, oral stereognosis, and articulatory awareness, which involved explicit judgments of relative tongue position for different speech sounds). Pairwise associations were examined between tasks within each domain and between task performance and age. Composite measures of auditory-perceptual and somatosensory functions were used to investigate the possibility of a sensory trade-off. Statistically significant associations were observed between the identification and discrimination tasks and the bite block and articulatory awareness tasks. In addition, significant associations with age were found for the category goodness and bite block tasks. There was no statistically significant evidence of a trade-off between auditory-perceptual and somatosensory domains. This study provided a multidimensional characterization of speech-related sensory function in older children/adolescents. Complete materials to administer all experimental tasks have been shared, along with measures of central tendency and dispersion for scores in two subgroups of age. Ultimately, we hope to apply this information to make customized treatment recommendations for children with RSSD based on sensory profiles.

Motion sickness susceptibility and visually induced motion sickness as diagnostic signs in Parkinson's disease.

Postural instability and loss of vestibular and somatosensory acuity can be part of the signs encountered in Parkinson's Disease (PD). Visual dependency is described in PD. These modifications of sensory input hierarchy are predictors of motion sickness (MS). The aim of this study was to assess MS susceptibility and effects of real induced MS in posture. 63 PD patients, whose medication levels (levodopa) reflected the pathology were evaluated, and 27 healthy controls, filled a MS questionnaire; 9 PD patients and 43 healthy controls were assessed by posturography using virtual reality. Drug amount predicted visual MS (p=0.01), but not real induced MS susceptibility. PD patients did not experience postural instability in virtual reality, contrary to healthy controls. Since PD patients do not seem to feel vestibular stimulated MS, they may not rely on vestibular and somatosensory inputs during the stimulation. However, they feel visually induced MS more with increased levodopa drug effect. Levodopa amount can increase visual dependency. The strongest MS predictors must be studied in PD to better understand the effect of visual stimulation and its absence in vestibular stimulation.

Characterizing sensorimotor profiles in children with residual speech sound disorder: a pilot study

PurposeChildren with speech errors who have reduced motor skill may be more likely to develop residual errors associated with lifelong challenges. Drawing on models of speech production that highlight the role of somatosensory acuity in updating motor plans, this pilot study explored the relationship between motor skill and speech accuracy, and between somatosensory acuity and motor skill in children. Understanding the connections among sensorimotor measures and speech outcomes may offer insight into how somatosensation and motor skill cooperate during speech production, which could inform treatment decisions for this population. MethodTwenty-five children (ages 9-14) produced syllables in an /ɹ/ stimulability task before and after an ultrasound biofeedback treatment program targeting rhotics. We first tested whether motor skill (as measured by two ultrasound-based metrics of tongue shape complexity) predicted acoustically measured accuracy (the normalized difference between the second and third formant frequencies). We then tested whether somatosensory acuity (as measured by an oral stereognosis task) predicted motor skill, while controlling for auditory acuity. ResultsOne measure of tongue shape complexity was a significant predictor of accuracy, such that higher tongue shape complexity was associated with lower accuracy at pre-treatment but higher accuracy at post-treatment. Based on the same measure, children with better somatosensory acuity produced /ɹ/ tongue shapes that were more complex, but this relationship was only present at post-treatment. ConclusionThe predicted relationships among somatosensory acuity, motor skill, and acoustically measured /ɹ/ production accuracy were observed after treatment, but unexpectedly did not hold before treatment. The surprising finding that greater tongue shape complexity was associated with lower accuracy at pre-treatment highlights the importance of evaluating tongue shape patterns (e.g., using ultrasound) prior to treatment, and has the potential to suggest that children with high tongue shape complexity at pre-treatment may be good candidates for ultrasound-based treatment.

Physical performance and fitness gain during an Infantry Commanders Course are influenced by chronic ankle instability

Introduction: Army training often incurs physical injury, with ankle injuries occurring in 10-20 % of soldiers during training. These patterns are reported with similar frequency and body-part distribution of injury in Israeli Defence Force (IDF) combat units. Research has shown that 32 % of individuals with ankle injuries develop chronic ankle instability (CAI). This study aimed to determine whether having chronic ankle instability (CAI) affects the physical performance of soldiers during their army training, as measured in routine army fitness tests, and in other neuromuscular tests. It was hypothesised that soldiers with CAI would not perform as well on all lower limb performance tests, and would improve less during the period of military training. Methods: A prospective cohort comparison was made within soldiers undertaking the Infantry Commanders Course (IC Course) of the IDF. Soldiers were tested at weeks one and 14 of the course, including with a 3,000m timed run, an agility test over an X-shaped course, the Y Balance Test (YBT) and the Active Movement Extent Discrimination Assessment (AMEDA) somatosensory test. All participants completed the required physical training throughout the course. Changes in physical performance were analysed using a two-way ANOVA, for soldier groups categorised as having healthy ankles or CAI based on a score of ≤25 on the Cumberland Ankle Instability Tool (CAIT) questionnaire. Results: 105 soldiers (mean (±SD) height 1.75m ± 0.06, weight 75.15kg ± 10.74) participated and were separated into those with and without CAI (n=59 and 46, respectively). Overall, scores on all 4 tests (3,000 m run, X-agility test, YBT and AMEDA) improved during the course. However, soldiers with CAI did not improve on the X-agility test, while those with healthy ankles did. At the start of the course, soldiers with CAI performed worse on the YBT-PM (postero-medial direction), but this difference was no longer present at 14 weeks. Compared with their healthy counterparts, soldiers with CAI performed better on the AMEDA at the start and 14 -week testing points. Discussion: Ankle instability restricts agility gains in soldiers during 14-weeks of physical training but has no effect on 3,000m running performance. Soldiers with CAI perform worse in YBT balance tests, in the Anterior and PM directions particularly. Soldiers with CAI have better somatosensory acuity than those with stable ankles, despite the CAI association with worse performance in other tests. This heightened somatosensory awareness may enable them to compensate for lower performance in other tests. Conflict of interest statement: “This study was supported by a research grant from the Medical Research Directorate of the Israeli Defence Forces. No other specific grant funding was received from agencies in the public, commercial, or not-for-profit sectors.”

Toward an index of oral somatosensory acuity: Comparison of three measures in adults.

Somatosensory targets and feedback are instrumental in ensuring accurate speech production. Individuals differ in their ability to access and respond to somatosensory information, but there is no established standard for measuring somatosensory acuity. The primary objective of this study was to determine which of three measures of somatosensory acuity had the strongest association with change in production accuracy in a vowel learning task, while controlling for the better-studied covariate of auditory acuity. Three somatosensory tasks were administered to 20 female college students: an oral stereognosis task, a bite block task with auditory masking, and a novel phonetic awareness task. Individual scores from the tasks were compared to their performance on a speech learning task in which participants were trained to produce novel Mandarin vowels with visual biofeedback. Of the three tasks, only bite block adaptation with auditory masking was significantly associated with performance in the speech learning task. Participants with weaker somatosensory acuity tended to demonstrate larger increases in production accuracy over the course of training. The bite block adaptation task measures proprioceptive awareness rather than tactile acuity and assesses somatosensory knowledge implicitly, with limited metalinguistic demands. This small-scale study provides preliminary evidence that these characteristics may be desirable for the assessment of oral somatosensory acuity, at least in the context of vowel learning tasks. Well-normed somatosensory measures could be of clinical utility by informing diagnosis/prognosis and treatment planning.

Effects of vibrotactile feedback on postural sway in trans-femoral amputees: A wavelet analysis

Loss of somatosensory feedback after amputation inflicts a serious challenge to achieve postural stability. Improving motor skills by incorporating sensory feedback in rehabilitation protocols for persons with lower limb amputation has been gaining traction over time. However, the control mechanisms involved in this regarding time–frequency analysis have not been investigated yet. The purpose of this study was to explore the frequencies/time-scales responsible for postural stability in trans-femoral amputees with vibrotactile feedback. Center of Pressure (COP) signals were collected from 5 trans-femoral amputees and 10 healthy subjects during weight shifting balance tasks. A customized foot insole was used to estimate the COP for actuation of vibratory feedback. The evaluation of postural sway fluctuations by means of COP excursions with vibrotactile feedback was computed by wavelet transform method. Vibrotactile feedback was found to be effective in controlling low frequency postural sway in amputees. We found significantly higher energy (p = 0.004, 0.0007) at shorter time-scales (j = 6,7, freq. = 0.6–1.25 Hz) and lower energy (p = 0.0006) at longer time-scale (j = 10, freq. = 0.078 Hz) in amputees with vibrotactile feedback in comparison to healthy subjects using Coif 1 wavelet. We also found significant increase in energy (p = 0.003) during forward weight shifting with vibrotactile feedback in the sound limb of amputees in comparison to no feedback session at frequency/time-scales corresponding to somatosensory acuity (j = 6–8, freq. = 0.3–1.5 Hz) using Haar wavelet. These findings reflect the higher contribution of somatosensory receptors in amputees with vibrotactile feedback and may provide a better understanding of the mechanisms associated with standing balance in terms of time–frequency analysis.

Increased intrinsic excitability and decreased synaptic inhibition in aged somatosensory cortex pyramidal neurons

Sensorimotor performance declines during advanced age, partially due to deficits in somatosensory acuity. Cortical receptive field expansion contributes to somatosensory deficits, suggesting increased excitability or decreased inhibition in primary somatosensory cortex (S1) pyramidal neurons. To ascertain changes in excitability and inhibition, we measured both properties in neurons from vibrissal S1 in brain slices from young and aged mice. Because adapting and non-adapting neurons—the principal pyramidal types in layer 5 (L5)—differ in intrinsic properties and inhibitory inputs, we determined age-dependent changes according to neuron type. We found an age-dependent increase in intrinsic excitability in adapting neurons, caused by a decrease in action potential threshold. Surprisingly, in non-adapting neurons we found both an increase in excitability caused by increased input resistance, and a decrease in synaptic inhibition. Spike frequency adaptation, already small in non-adapting neurons, was further reduced by aging, whereas sag, a manifestation of Ih, was increased. Therefore, aging caused both decreased inhibition and increased intrinsic excitability, but these effects were specific to pyramidal neuron type.

Establishing an index of somatosensory acuity: comparison of three measures in adults

Speech production is directed by auditory and somatosensory targets that shape and update the motor plan through corresponding feedback channels (Guenther, 2016). Somatosensory feedback is instrumental in ensuring accurate articulator placement, as shown in studies where perturbed somatosensory feedback leads to reduced speech precision (Ringel and Steer, 1963; Gammon et al., 1971; Jones and Munhall, 2003). As no gold standard for measuring somatosensory acuity exists, the current study will compare three measures in 20 adults: (1) an oral stereognosis task (Steele et al., 2014) measuring tactile input received by the articulators; (2) a novel phonetic awareness task measuring the proprioceptive sense of articulator position; (3) a bite-block task with auditory masking (Zandipour et al., 2006) measuring the degree of compensation for perturbation using only somatosensory feedback. To test the hypothesis that participants with higher somatosensory acuity showed larger increases in production accuracy, participants’ scores on each task will be used to predict performance in an L2 vowel learning task (Li et al., in press). Three linear regression models will be fit, one for each somatosensory measure. The model that best explains change in production accuracy will be selected using the Akaike/Bayes Information Criteria. Establishing a valid measure of somatosensory acuity will enable future research to elucidate somatosensory influences on speech production.

Effect of stochastic resonance on proprioception and kinesthesia in anterior cruciate ligament reconstructed patients

Low amplitude mechanical noise vibration has been shown to improve somatosensory acuity in various clinical groups with comparable deficiencies through a phenomenon known as Stochastic Resonance (SR). This technology showed promising outcomes in improving somatosensory acuity in other clinical patients (e.g., Parkinson’s disease and osteoarthritis). Some degree of chronic somatosensory deficiency in the knee has been reported following anterior cruciate ligament (ACL) reconstruction surgery. In this study, the effect of the SR phenomenon on improving knee somatosensory acuity (proprioception and kinesthesia) in female ACL reconstructed (ACLR) participants (n = 19) was tested at three months post-surgery, and the results were compared to healthy controls (n = 28). Proprioception was quantified by the measure of joint position sense (JPS) and kinesthesia with the threshold to detection of passive movement (TDPM).The results based on the statistical analysis demonstrated an overall difference between the somatosensory acuity in the ACLR limb compared to healthy controls (p = 0.007). A larger TDPM was observed in the ACLR limb compared to the healthy controls (p = 0.002). However, the JPS between the ACLR and healthy limbs were not statistically significantly different (p = 0.365). SR significantly improved JPS (p = 0.006) while the effect was more pronounced in the ACLR cohort. The effect on the TDPM did not reach statistical significance (p = 0.681) in either group.In conclusion, deficient kinesthesia in the ACLR limb was observed at three months post-surgery. Also, the positive effects of SR on somatosensory acuity in the ACL reconstructed group warrant further investigation into the use of this phenomenon to improve proprioception in ACLR and healthy groups.

Speech production and sensory impairment in mild Parkinson's disease.

Little is known about speech-related sensory systems and the link to speech in Parkinson's disease (PD). This study investigates auditory and somatosensory acuity and their association to speech in PD, using /s/ and /ʃ/ as speech targets. Ten adults with mild PD and ten age- and gender-matched healthy participants performed three tasks. In the auditory task, participants discriminated three aperiodic sounds acoustically modified from /s/ and /ʃ/ and differing in spectral shapes. In the tactile task, they judged the orientation of a dome-shaped grating probe gently touching their tongue tip. Measures of auditory and tactile acuity were determined based on participants' responses. For the production task, participants read a passage and eight sentences with /s/- and /ʃ/-initial words; acoustic contrast between the two sibilants was measured using difference between the average first spectral moments of /s/ and /ʃ/. The PD participants showed reduced auditory acuity of spectral sibilant contrast and reduced tactile acuity of the tongue tip. For speech production, the PD group showed smaller sibilant contrast in the sentence readings, but the difference was not statistically significant. Correlation analyses showed significant correlations between tactile acuity and sibilant contrast for the PD group, but not for auditory task.

Production and perception of the English sibilants /s/ and /∫/ in persons with Parkinson's disease

Parkinson's disease (PD) presents with both sensory and motor deficits including speech, characterized by soft voice, monotonicity, and imprecise articulation. Both audition and somatosense are believed important for accurate speech production. Individual studies have identified auditory impairment and somatosensory impairment of the orofacial structures and the larynx. No studies have examined the relationship between imprecise articulation and sensory impairment. This research aims at examining sensory deficits and the relationship between sensory deficits and imprecise articulation in persons with PD. The production of /s/ and /∫/, auditory discrimination and identification in spectral shape, and somatosensory acuity on the tongue tip are examined. In the production task, participants read monosyllabic words beginning with /s/ and /∫/ embedded in a carrier sentence; measures of spectral shapes are made. Auditory tasks comprise an acuity task testing for participants' auditory acuity in perceiving spectral shapes and a /s/-/∫/ categorization task testing for their categorical boundaries. The somatosensory acuity task tests for participants' somatosensory acuity in spatial orientation on the tongue tip. Relationships between production of /s/ and /∫/ and sensory performance are tested in correlational tests.

Integration of auditory and somatosensory error signals in the neural control of speech movements

We investigated auditory and somatosensory feedback contributions to the neural control of speech. In task I, sensorimotor adaptation was studied by perturbing one of these sensory modalities or both modalities simultaneously. The first formant (F1) frequency in the auditory feedback was shifted up by a real-time processor and/or the extent of jaw opening was increased or decreased with a force field applied by a robotic device. All eight subjects lowered F1 to compensate for the up-shifted F1 in the feedback signal regardless of whether or not the jaw was perturbed. Adaptive changes in subjects' acoustic output resulted from adjustments in articulatory movements of the jaw or tongue. Adaptation in jaw opening extent in response to the mechanical perturbation occurred only when no auditory feedback perturbation was applied or when the direction of adaptation to the force was compatible with the direction of adaptation to a simultaneous acoustic perturbation. In tasks II and III, subjects' auditory and somatosensory precision and accuracy were estimated. Correlation analyses showed that the relationships 1) between F1 adaptation extent and auditory acuity for F1 and 2) between jaw position adaptation extent and somatosensory acuity for jaw position were weak and statistically not significant. Taken together, the combined findings from this work suggest that, in speech production, sensorimotor adaptation updates the underlying control mechanisms in such a way that the planning of vowel-related articulatory movements takes into account a complex integration of error signals from previous trials but likely with a dominant role for the auditory modality.

An investigation of the relation between sibilant production and somatosensory and auditory acuity

The relation between auditory acuity, somatosensory acuity and the magnitude of produced sibilant contrast was investigated with data from 18 participants. To measure auditory acuity, stimuli from a synthetic sibilant continuum ([s]-[ʃ]) were used in a four-interval, two-alternative forced choice adaptive-staircase discrimination task. To measure somatosensory acuity, small plastic domes with grooves of different spacing were pressed against each participant's tongue tip and the participant was asked to identify one of four possible orientations of the grooves. Sibilant contrast magnitudes were estimated from productions of the words 'said,' 'shed,' 'sid,' and 'shid'. Multiple linear regression revealed a significant relation indicating that a combination of somatosensory and auditory acuity measures predicts produced acoustic contrast. When the participants were divided into high- and low-acuity groups based on their median somatosensory and auditory acuity measures, separate ANOVA analyses with sibilant contrast as the dependent variable yielded a significant main effect for each acuity group. These results provide evidence that sibilant productions have auditory as well as somatosensory goals and are consistent with prior results and the theoretical framework underlying the DIVA model of speech production.

Ecological correlates of infraorbital foramen area in primates

The infraorbital foramen (IOF) transmits the infraorbital nerve (ION) to specialized sensory cells (mechanoreceptors) in the maxillary region. The size of the IOF has been used in numerous paleoecological interpretations of the fossil record. However, these interpretations have been applied without an explicit analysis of the relationship between ecological variables and the IOF. ION and IOF cross-sectional area show a strong positive correlation. As a result, IOF area can be a proxy for ION area, and it is hypothesized that IOF area may be a good measure for maxillary somatosensory acuity. Differences in diet, substrate preference, and/or activity pattern have been shown to correlate with differences in maxillary somatosensory acuity among mammals. This study examines how IOF area covaries with different ecological variables. IOF area was measured for 89 primate species. Ecological profiles were also created for each species and used to evaluate interspecific variation in relative IOF area within each ecological category. The results show a significant relationship between relative IOF area and diet, but not substrate preference or activity pattern. Frugivores have significantly larger relative IOFs than either folivores or insectivores, but the relative IOFs of folivores and insectivores do not differ significantly from one another. These results partially support the hypothesis that maxillary mechanoreception is a critical sensory cue for primates within a feeding context. Results for this study suggest the IOF can be used as an informative character in some paleoecological interpretations of the primate fossil record.

Meissner corpuscles and somatosensory acuity: the prehensile appendages of primates and elephants.

Meissner corpuscles (MCs) are specialized mechanoreceptors located exclusively in the papillae of glabrous skin. They are confined largely to cutaneous pads of the extremities and respond to transient, phasic, or vibratory stimuli. Though absent in most eutherian taxa, MCs are reported in all primates studied, being most developed in modern humans. The location of MCs between the internal ridges of the epidermis indicates they are well situated to detect friction or deformation at the external surface. Accordingly, MCs are hypothesized to provide primates generally with an enhanced tactile perception. However, the selective pressures favoring greater somatosensory acuity in primates are seldom considered. Interestingly, primate digital dexterity varies greatly. In general, dexterity improves with the extent to which foraging requires food manipulation or textural evaluation. This observation implies that MC density could vary accordingly. Here we report on the density of MCs in five anthropoid taxa selected to represent diverse dietary regimes. Results show that greater MC density correlates with the extent to which primates are frugivorous; however, locomotor and/or phylogenetic effects cannot be discounted.

Magnification, receptive-field area, and "hypercolumn" size in areas 3b and 1 of somatosensory cortex in owl monkeys.

Magnification, receptive-field area, and "hypercolumn" size in areas 3b and 1 of somatosensory cortex in owl monkeys.M Sur, M M Merzenich, and J H KaasM Sur, M M Merzenich, and J H KaasPublished Online:01 Aug 1980https://doi.org/10.1152/jn.1980.44.2.295MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByTactile innervation densities across the whole bodyGiulia Corniani and Hannes P. Saal19 October 2020 | Journal of Neurophysiology, Vol. 124, No. 4Biases in tactile localization by pointing: compression for weak stimuli and centering for distributions of stimuliJack Brooks, Tatjana Seizova-Cajic, and Janet L. 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The forelimb representation achieved by a mosaic of segregatesBrain Research Reviews, Vol. 13, No. 1Somatosensory cortex in macaque monkeys: laminar differences in receptive field size in areas 3b and 1Brain Research, Vol. 342, No. 2Parallel processing of somatosensory information: A theoryBrain Research Reviews, Vol. 6, No. 1A realistic computer simulation of primary somatosensory cortex replicating static properties of topographic organization More from this issue > Volume 44Issue 2August 1980Pages 295-311 https://doi.org/10.1152/jn.1980.44.2.295PubMed7411189History Published online 1 August 1980 Published in print 1 August 1980 Metrics