Mirror Test Research Articles

Impact of short-term total dissolved gas supersaturation on cognitive function and swimming performance in medaka (Oryzias latipes)

During the flood season, high dam discharge rates result in total dissolved gas (TDG) supersaturation. This condition causes gas bubble trauma and can lead to fish mortality, which poses a significant threat to downstream river ecosystems. Assessing the ecological risks of TDG supersaturation is a challenge in waterpower-intensive river basins worldwide. Few studies have explored the impact of TDG supersaturation on fish behaviours, such as aggression and memory, which are crucial for feeding, reproduction, and predator avoidance. In this study, behavioural tests were conducted in a T-maze to investigate the effects of acute TDG supersaturation on swimming behaviour, aggression, and memory in medaka (Oryzias latipes). The results demonstrated that medaka exposed to TDG levels of 115% and 130% for 2 h had significantly reduced swimming performance.At TDG levels of 100%, 115% and 130%, medaka activity rates in the mirror arm of the maze in the mirror test were 44.34 ± 12.88%, 40.27 ± 15.44% and 35.35 ± 16.07%, respectively. Similarly, the activity rates of medaka in the active stimulus arm of the maze in the memory test were 50.35 ± 14.75%, 40.76 ± 12.51% and 35.35 ± 18.47%, respectively. The behaviour of medaka changed with increasing TDG supersaturation. These findings contribute to the development of an ecological risk assessment model for TDG supersaturation based on memory and aggression in fish and provide data for developing management strategies to mitigate the adverse effects of TDG supersaturation.

Exploring the Neural Mechanisms of Mirrored-Self Misidentification in Alzheimer's Disease.

Alzheimer's disease (AD) is a complex neurodegenerative condition that causes a range of cognitive disturbances, including mirror-self misidentification syndrome (MSM), in which patients cannot recognize themselves in a mirror. However, the mechanism of action of MSM is not precisely known. This study aimed to explore the possible neural mechanisms of action of MSM in AD using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). This study included 48 AD patients, 13 in the MSM group and 35 in the non-MSM group. The permeability of the blood-brain barrier (BBB) was quantitatively monitored by measuring the transfer rate (Ktrans) of the contrast agent from the vasculature to the surrounding tissue using DCE-MRI. The concentration of contrast agents in different brain regions was measured, and the Patlak model was used to calculate Ktrans. Ktrans values were compared between the left and right cerebral hemispheres in different brain areas between the MSM and non-MSM groups. Additionally, the difference in Ktrans values between mild and severe MSM was assessed. Logistic regression analysis was used to examine the risk factors for MSM. The Mann‒Whitney U test was used to compare two groups and revealed elevated Ktrans values in the left thalamus, left putamen, left globus pallidus, left corona radiata, and right caudate in the MSM group (p<0.05). Logistic regression analysis revealed that increased Ktrans values in the left putamen (OR=1.53, 95% CI=1.04, 2.26) and left globus pallidus (OR=1.54, 95% CI=1.02, 2.31) may be risk factors for MSM. After dividing MSM patients into mild and moderate-severe groups, the Ktrans values of the thalamus in the moderate-severe group were greater than those in the mild group (p<0.05). Our study revealed the relationship between BBB permeability and MSM in AD. MSM is associated with BBB breakdown in the left putamen and globus pallidus. The left putamen and globus pallidus may function in mirror self-recognition. Higher BBB permeability in the thalamus may reflect the severity of AD in MSM.

Cleaner fish with mirror self-recognition capacity precisely realize their body size based on their mental image

Animals exhibiting mirror self-recognition (MSR) are considered self-aware; however, studies on their level of self-awareness remain inconclusive. Recent research has indicated the potential for cleaner fish (Labroides dimidiatus) to possess a sophisticated level of private self-awareness. However, as this study revealed only an aspect of private self-awareness, further investigation into other elements is essential to substantiate this hypothesis. Here, we show that cleaner fish, having attained MSR, construct a mental image of their bodies by investigating their ability to recall body size. A size-based hierarchy governs the outcomes of their confrontations. The mirror-naïve fish behaved aggressively when presented with photographs of two unfamiliar conspecifics that were 10% larger and 10% smaller than their body sizes. After passing the MSR test, they refrained from aggression toward the larger photographs but still behaved aggressively toward the smaller ones without re-examining their mirror images. These findings suggest that cleaner fish accurately recognize their body size based on mental images of their bodies formed through MSR. Additionally, mirror-experienced fish frequently revisited the mirror when presented with an intimidating larger photograph, implying the potential use of mirrors for assessing body size. Our study established cleaner fish as the first non-human animal to be demonstrated to possess private self-awareness.

Early impact of domestication on aggressiveness, activity, and stress behaviors in zebrafish (Danio rerio) using mirror test and automated videotracking

Fish domestication progresses through five levels: from the initial acclimatization to captivity (Level 1), to the life cycle completion in captivity (Level 4), and even to the implementation of selective breeding programs (Level 5). Domestication leads to phenotypic changes over generations, sometimes from the very first generation. Behavioral traits are among the first to change. However, in fish, potential behavioral changes during early domestication have been little studied. Therefore, we studied potential behavioral changes among early and advanced levels of domestication in a model species, the zebrafish (Danio rerio), using a mirror test experiment, commonly used to assess traits involved in activity, aggressiveness, and stress in this species. We compared these traits between wild zebrafish in captivity (F0; Level 1), the first generation of their captive-born offspring (F1; Level 4), and three laboratory strains (AB, TU, and WIK; Level 5). Each fish was individually filmed and tracked using an automated procedure for 5 min. Nine behavioral traits and one activity-related trait were characterized for each individual based on the movements and positioning of the fish. We applied a principal component analysis (PCA) and tested the significance of potential differences between groups using an analysis of similarities (ANOSIM). We applied an indicator value analysis (IndVal) to determine which traits were most expressed by each group. We detected differences between groups and across domestication levels. More specifically, we highlighted differentiations between different levels of domestication (e.g. between F1, AB, TU, and WIK) as early as the beginning of the domestication process (i.e. F0 vs. F1), but also within the same level of domestication (i.e. AB vs. TU). Based on PCA and IndVal, (i) F0 and F1 tended to show stronger expression of stress-related traits than the other groups, (ii) F0 was more active than others, and (iii) TU was more aggressive than AB. Our results confirmed that domestication can change fish behavior, even in the first generation born in captivity, although these modifications remain limited. In contrast, we did not observe any general trends correlated with domestication levels, given that AB and TU diverged in their aggressiveness levels, and WIK differed only from F1. This result needs to be generalized to other species but also considered for domestication for aquaculture. If future studies confirm that the changes observed at the beginning of the domestication process remain limited and that there is no consistent evolutionary trend across generations in fish, this would highlight the crucial importance of selecting the right species from the outset of domestication. It would also emphasize the need to design selective breeding programs that shape fish stocks with the most desirable characteristics. To our knowledge, this study is one of the few to examine the behavior of wild zebrafish alongside laboratory strains, offering a unique insight into the early stages of domestication.

Tocotrienol-rich fraction (TRF) protects against retinal cell apoptosis and preserves visual behavior in rats with streptozotocin-induced diabetic retinopathy

BackgroundTocotrienol is a vitamin E analogue that is known to exert anti-inflammatory and antioxidant effects. Hence, in the current study, the effects of TRF on the expression of pro- and anti-apoptotic proteins in the streptozotocin-induced diabetic rat retinas were investigated. The effect of TRF on the visual behaviour of rats was also studied.MethodsDiabetes was induced in rats by intraperitoneal injection of streptozotocin and was confirmed by a blood sugar level of at least 20 mmol/L, 48 h, post-injection. Diabetic rats were divided into a group treated with vehicle (DV) and the other treated with TRF (100 mg/kg; DT). A group of non-diabetic rats treated with vehicle (N) served as the control group. All treatments were administered orally for 12 weeks. Rats were then subjected to an assessment of general behaviour in an open field arena and a two-chamber mirror test to assess their visual behaviour. At the end of the experimental period, rats were sacrificed, and their retinas were isolated to measure the expression of pro- (Casp3, Bax) and anti-apoptotic (Bcl2) markers using RT-qPCR and ELISA. TUNEL staining was used to detect the apoptotic retinal cells.ResultsTreatment with TRF lowered the retinal expression of Casp3 protein by 2.26-folds (p < 0.001) and Bax protein by 2.18-fold (p < 0.001) compared to vehicle-treated rats. The retinal anti-apoptotic protein Bcl2 expression was 1.87-fold higher in DT compared to DV rats (p < 0.001). Accordingly, the Bax/Bcl2 ratio in the TRF-treated group was significantly greater in DT compared to DV rats. Retinal Casp3, Bax, and Bcl2 gene expression, as determined by RT-qPCR, also showed changes corresponding to protein expression. In the open field test, DV rats showed greater anxiety-related behaviour than group N, while the behaviour of DT rats was similar to the N group of rats. DT rats and group N rats preferred the inverse mirror chamber over the mirror-containing chamber in the two-mirror chamber test (p < 0.01).ConclusionOral TRF therapy for 12 weeks lowers retinal cell apoptosis by decreasing pro- and increasing anti-apoptotic markers. The preservation of visual behaviour in a two-chamber mirror test supported these retinal molecular alterations in diabetic rats.

Influence of humic acids on growth performance, bravery, stress resistance, antioxidant activity, and immune gene expression in male Siamese fighting fish (Betta splendens)

The current study investigated the effects of a humic acid supplement on the growth performance, antioxidant enzyme activity, immune-related genes, behavior and endocrinology of male Betta splendens fish. Fish species that are naturally exposed to high levels of humic substances in their environment are likely to perform better under captive conditions when given these substances. In this study, fish were fed a diet containing 0, 0.5 %, 1 %, and 1.5 % humic acid for six weeks. The results showed no significant differences in growth and feeding parameters between treatments (p > 0.05). The fish with a diet of 1.5 % humic acid showed more aggressive behavior in the mirror test than the control group (p < 0.05). In contrast, the fish fed a diet containing 1 % and 1.5 % humic acid showed a higher level of activity in the test with new objects than the control group (p < 0.05). The testosterone levels after aggression were significantly higher in the fish fed diets containing 1 % and 1.5 % humic acid than in the control group (p < 0.05). In addition, the humic acid-treated fish showed lower oxidative stress and cortisol production in common aquaculture stressors than the control (p < 0.05). Gene expression analysis showed upregulation of immune-related genes, including β-defensin 1, c-type lysozyme, interleukin-1β, and tumor necrosis factor-α, in response to humic acid supplementation compared to control (p < 0.05). Overall, the results of this study indicate that a diet containing 1 % humic acid has a positive effect on the physiology, immunology, and behavior of male B. splendens.

Ghost crab (Ocypode quadrata) modify their behavior during mirror exposure

Recently, ghost crabs (Ocypode quadrata) were shown to exhibit behavior consistent with passing the mark test, which implies the capacity for self-recognition. Considering this, it seems reasonable to suggest these animals can also distinguish their mirror image from different social stimuli, such as live conspecifics. In the current research, ghost crabs were placed in an experimental tank bisected by a mirror, clear partition separating a conspecific, and non-reflective partition on separate trials. Aggressive threat displays, time spent near partitions, eye cleaning, and partition contact were recorded during each condition. Results showed more aggression in trials with a conspecific present (i.e. clear partition), though this effect was only marginally significant. In addition, eye cleaning was significantly lower in the clear, compared to mirror and non-reflective treatments. Significantly more contact occurred with non-reflective partitions and time near each barrier was similar. These findings might suggest the capacity to distinguish mirror reflections from conspecifics, and mirror self-recognition could promote such ability. This, and other alternatives, are discussed as potential explanations for the observed effects.

Histoire de la description du « signe du miroir » dans les Annales Médico-Psychologiques (1927–1930). Aperçus sur sa postérité et sa valeur sémiologique

Described as an early sign of schizophrenia (or dementia praecox) between the years 1927 and 1930 by two French psychiatrists, Paul Abély and Achille Delmas, the “mirror sign” was subsequently the object of in-depth studies by eminent specialists outside of France who discussed its semiotic value and its early interpretations. In this regard, we will underscore the key role played by psychoanalytical ideas, specifically the concept of narcissism. We will also note the relative neglect of results of the mirror test for other categories of patients, particularly those with intellectual deficiencies due to aging (a now well-studied group).

Machine learning-based aggressiveness assessment model construction for crabs: A case study of swimming crab Portunus trituberculatus

Aggressiveness trait-based selection is crucial for alleviating interspecies cannibalism in economic crab species and enhancing survival rates in aquaculture. However, there is a lack of efficient and simple methods for assessing aggressiveness. In this study, we measured aggressiveness of the swimming crab Portunus trituberculatus through repeated mirror tests and fighting experiments. Factor analysis and the K-means algorithm were used to assess aggressiveness quantitatively and qualitatively. A combination of multiple linear regression and support vector machine (SVM) analyses was employed to construct an aggressiveness assessment model for swimming crabs and explore the relationship between aggressiveness and fighting ability. The results showed significant correlations among repeated aggressive behaviors (attacking, chela extending, defending, crossing, reverse walking, and freezing). Aggression score was significantly correlated with fighting behaviors, and there were significant differences in fighting abilities among different levels of aggressiveness. This suggested that aggressive behaviors are consistent within individuals and that aggressiveness, as a personal trait, affects the fighting ability of swimming crabs. Aggression score (Y) and clustering results of K-means can serve as assessment indicators of aggressiveness. The predictive variables for the quantitative assessment model were relative movement distance (X1) and freezing duration (X2). The adjusted R-square of the optimized quantitative model was 0.72, it also had the smallest Sigma, AIC, MSE, and RMSE values and the best fitting regression equation, which was Y = 0.023X1 – 0.001X2 – 0.002. The predictor variables for the qualitative assessment model were relative movement distance, freezing frequency, and duration. SVM was used to construct the qualitative model, and the prediction accuracy was 92%, sensitivity was 84%, and specificity was 100%, indicating the model has a good classification and prediction effect. The machine learning-based aggressiveness assessment model constructed in this study provides a behavioral method for the selection and high-throughput measurement of economic crab species with excellent aggressiveness traits, giving it important industrial application value.

Political Conocimiento in Teaching Mathematics: mathematics teacher candidates enacting their ethical identities

The sanctioned language around “mathematics teacher knowledge” in the US centers pedagogy, content (mathematical knowledge), and students. Yet, this teacher learning approach often promotes (explicitly or implicitly) teaching and learning of mathematics that operationalizes mathematics as rigid, as a gatekeeper, and only useful for global competition in STEM-related fields. These tacit capitalist goals result in teachers being expected to convey “clear and useful” mathematical information to students, not question why mathematics is being taught, who benefits, and/or how to intervene if the learning environment is harmful for students who are Black, Indigenous, students of Color, multilingual, dis/abled, queer, nonbinary, and/or of immigrant backgrounds. In this article, we build upon a form of relational knowing that intertwines mathematics, pedagogies, students, and politics called Political Conocimiento in Teaching Mathematics. Focusing on political knowledge brings the margins to the center by recognizing political issues cannot be separated from other dimensions or added on, as if politics are not already present in mathematics teaching and learning. As three women of Color, we present empirical results from three teacher education programs in the USA with teacher candidates (n = 55) who range in intersectional identities. Using scenario-based activities that support their development of political knowledge, we apply the lens of “The Mirror Test” to highlight how teacher candidates’ intersectional identities influenced the ethical identities they enacted. Some candidates focused more on “accountability” while others focused on “performativity.” We offer implications for future research on ethical identities in mathematics education with teachers and teacher candidates of various intersectional identities.

Testing of spherical mirrors with extremely large R numbers using a quasi-autocollimation method

Spherical mirrors with large R numbers have extreme advantages in optical systems with large apertures and long focus lengths for improving imaging resolution and field of view. Their manufacturing and testing accuracy directly affects the final wavefront aberration of the systems. However, due to the influence of airflow disturbance in the long optical path, testing large R number spherical mirrors with high precision is difficult for the direct testing method. In this paper, a quasi-autocollimation test (QACT) method is proposed based on the consistency and reverse compensation between sphere and paraboloid with large R numbers. In QACT, the length of the testing path is reduced to half, and the test sensitivity of the surface figure error is doubled. According to the Kolmogorov turbulence theory, the suppressed degree of QACT to airflow disturbance is quantitatively evaluated, and QACT can suppress the random error in test to 35%. A comparative experiment between direct test and QACT method is carried out on a ∅100 spherical mirror with 8-meter radius of curvature. Airflow disturbance in the testing environment is calculated by mathematical fitting and the repeated accuracy is improved from 4 nm to 1.4 nm in a single test using the QACT method, which is consistent with theoretical analysis. The research results will provide a new strategy for ultra-precision and efficiency tests of large R number spherical mirrors.

Are lateralized and bold fish optimistic or pessimistic?

Cognitive bias is defined as the influence of emotions on cognitive processes. The concept of the cognitive judgement bias has its origins in human psychology but has been applied to animals over the past 2 decades. In this study we were interested in determining if laterality and personality traits, which are known to influence learning style, might also be correlated with a cognitive bias in the three-spined sticklebacks (Gasterosteus aculeatus). We used the judgement bias test with the go/no-go procedure where fish were first trained to discriminate between a black and white card and, after reaching a minimum learning criterion, tested their response to an ambiguous card (grey). Optimistic subjects were expected to have a high expectation of reward associated with an ambiguous stimulus, whereas pessimistic subjects a high expectation of non-reward. We used an emergence and a mirror test to quantify boldness and laterality, respectively. We hypothesised that male, bolder and more strongly lateralized fish would be more optimistic than female, shy and less strongly lateralised fish. We found that males and more strongly lateralized fish were more optimistic than females and less strongly lateralized fish. In addition, bold males were more optimistic than shy males as we predicted, but females showed the opposite pattern. Finally, fish trained on the black colour card learned the training task faster than those trained on a white card. Our results indicate that both laterality and personality traits are linked to animals’ internal states (pessimistic or optimistic outlooks) which likely has broad implications for understanding animal behaviour particularly in a welfare context.

Qualitative evaluation of a parabolic mirror with substructured Ronchi gratings

In this work we propose to qualitatively test the quality of a concave parabolic mirror by means of the Ronchi interferometric test using substructured gratings to increase the sharpness of the fringes. The substructured gratings are designed considering that the grating period is divided into several stripes of equal width that can be transparent or opaque; the transmission coefficients of the stripes along the grating period are not periodic, but a previously chosen binary sequence. Equations were derived to obtain the corresponding intensity profiles and an analysis of these profiles was performed for different sequences and positions of the substructured gratings with respect to the test mirror. It was experimentally verified that the fringes are sharper at the Rayleigh distance inside and outside the mirror focus.

Aggressiveness predicts dominance rank in greylag geese: mirror tests and agonistic interactions.

Individual differences in aggressiveness, if consistent across time and contexts, may contribute to the long-term maintenance of social hierarchies in complex animal societies. Although agonistic interactions have previously been used to calculate individuals' positions within a dominance hierarchy, to date the repeatability of agonistic behaviour has not been tested when calculating social rank. Here, we examined the consistency and social relevance of aggressiveness as a personality trait in a free-flying population of greylag geese (Anser anser). For each individual, we quantified (i) aggressiveness using a standardized mirror stimulation test and (ii) dominance ranking based on the number of agonistic interactions won and lost in a feeding context. We found that individual differences in aggressiveness were significantly repeatable and that individuals' aggressiveness predicted their dominance rank position. The flock showed a robust and intermediately steep dominance hierarchy. Social rank was higher in paired birds, males and older birds, and most agonistic interactions occurred between individuals with moderate rank differences. We suggest that selection favours aggressiveness as a personality trait associated with resource acquisition and social rank, whereby a dominance hierarchy may increase the benefits of group living and reduce costs over conflict within dyads.

Multi-wavelength pinhole point diffraction interferometry for optics metrology with interferometric intensity based phase retrieval method

In this paper, we propose a multi-wavelength pinhole point diffraction interferometry (MPPDI) and a two-step phase extraction method based on the interferometric intensity information. MPPDI is mainly used to extend the dynamic measurement range of traditional pinhole point diffraction interferometry (PPDI) to realize the measurement of large-aperture and high-order aspheric surface. Spherical/aspherical optics will be test under three different wavelengths, and the corresponding interferograms are recoded by 3CMOS detector at the same moment. By combining different wavelengths, MPPDI can obtain a synthetic wavelength with a larger measuring range and greater flexibility. In interferometry, the choice of the wavelength of the light source has a great influence on the measurement range and accuracy. In MPPDI, we can choose different wavelength combinations to select the most suitable synthetic wavelength according to the asphericity of the tested mirror. To enhance efficiency and reduce the impact of air disturbances during phase shifts, we propose a new phase extraction method based on interferometric intensity to interpret the phase map of surface information. The background intensity of diffraction wavefront is firstly pre-recorded by 3CMOS, then phase-shift interferograms of test mirror is acquired with two-step piezoelectric ceramic driver (PZT) movement. From the analysis, it can be found that fringe modulation has tiny influence on the interferograms intensity. Therefore, based on global intensity distribution of fringe pattern and grayscale information, phase map can be retrieval using proposed two-step processing method (only single phase-shift). The two-step phase extraction method can reduce the number of phase shifts from 9 to 3, which improves the efficiency and reduces errors due to multiple phase shifts. MPPDI and two-step phase extraction we proposed have a larger measurement while reducing the number of phase shifts and avoiding error accumulation due to too many phase shifts. Suitable for large-aperture and high-order aspheric surface measurement.

Dual-Task and Single-Task Practice Does Not Influence the Attentional Demands of Movement Sequence Representations

This study examined the attentional demands of movement sequence representations at different temporal points after single- or dual-task practice. The visual-spatial representation encodes the movement based on visual-spatial coordinates such as the target locations. The motor representation encodes the movement in motor coordinates including joint angles and muscle activation patterns. Participants were randomly assigned to a single-task or dual-task practice group. Following acquisition, participants performed two retention tests and inter-manual transfer tests, both under dual-task and single-task. The transfer tests consisted of a mirror and non-mirror test and examined motor and visual-spatial representation development. The main finding is that attentional demands of the sequence representations were not affected by the practice condition. However, movement initiation requires more attention than the end of the movement in both representations.

Tactile localization promotes infant self-recognition in the mirror-mark test

Mirror self-recognition has been hailed by many as a milestone in the acquisition of self-awareness with respect to phylogenesis and human ontogenesis.1,2,3,4,5,6 Yet there has been considerable controversy over the extent to which species other than humans and their closest primate relatives are capable of mirror self-recognition, and to the mechanisms that give rise to this ability.1,7 One influential view is that mirror self-recognition in humans and their closest primate relatives is a cognitive advance that is a product of primate evolution, stemming from more recently evolved neural structures and networks that develop through experience-independent mechanisms during ontogenesis.1 In contrast, we show that the development of mirror self-recognition in human infants is a perception-action achievement, building on infants' ability to localize and reach to targets on the body. Infants who were given experience reaching to tactile targets on their bodies in the months prior to recognizing themselves in a mirror achieved mirror self-recognition earlier than infants in either a yoked age-matched control group or a longitudinal control group without such experience. Our results demonstrate that self-touch functions as an intermodal gateway through which infants learn how to localize and reach to stimuli on their bodies, including those that can only be seen in a mirror. These findings identify an overlooked role for the routine activity of self-touch in establishing a representation of the body and suggest that the development of human self-awareness is rooted in self-directed action.

Effect of Makeup Use on Depressive Symptoms: An Open, Randomized and Controlled Trial.

Depression is one of the most disabling diseases globally, with a high disease burden that generates high direct and indirect costs. The incidence of depression is twofold higher in adult women than in men. Biological and psychosocial factors constitute the pathophysiological bases of the condition and due to the complexity of the condition, current understanding is that the "treatment strategy must be multimodal". The objective of this study was to measure the effect of introducing the frequent use of makeup on improving depressive symptoms in adult women of medium-low purchasing power METHODS: Participants with the targeted profile who did not frequently use makeup were selected and randomised to receive (test group) or not (control group) stimuli and makeup products intended for encouraging the frequent use of makeup. The Zung Depression Self-Assessment Scale was used to assess depressive symptoms, with additional assessments on self-image perception using the mirror test and salivary cortisol level. The results demonstrated a sustained reduction in depressive symptoms (8.3 percentage points reduction in the Average Zung Index; P < 0.05), with a significant improvement in self-image perception (25% increase in the average score obtained in the mirror test; P < 0.05) and a specific influence on salivary cortisol levels (55% reduction in salivary cortisol concentration; P < 0.05) after the first makeup application. The results show that encouraging the frequent use of makeup, a practice that can be achieved by most people and which is simple and inexpensive to implement, can contribute to effective and sustainable improvement in the well-being and mental health of a significant portion of the population.

Self-recognition: From touching the body to knowing the self

Recognizing oneself in a mirror is a classic test of self-concept. A new study has revealed the perceptual-motor foundations of conceptual self-knowledge: infants' success in the mirror test was accelerated after touching a tactile stimulus while viewing themselves in a mirror.

A pilot study: effect of somatosensory loss on motor corrections in response to unknown loads in a reaching task by chronic stroke survivors.

Despite recent studies indicating a significant correlation between somatosensory deficits and rehabilitation outcomes, how prevailing somatosensory deficits affect stroke survivors' ability to correct their movements and recover overall remains unclear. To explore how major deficits in somatosensory systems impede stroke survivors' motor correction to various external loads, we conducted a study with 13 chronic stroke survivors who had hemiparesis. An inertial, elastic, or viscous load, which was designed to impose perturbing forces with various force profiles, was introduced unexpectedly during the reaching task using a programmable haptic robot. Participants' proprioception and cutaneous sensation were also assessed using passive movement detection, finger-to-nose, mirror, repositioning, and Weinstein pressure tests. These measures were then analyzed to determine whether the somatosensory measures significantly correlated with the estimated reaching performance parameters, such as initial directional error, positional deviation, velocity deviations, and speed of motor correction were measured.Of 13 participants, 5 had impaired proprioception, as they could not recognize the passive movement of their elbow joint, and they kept showing larger initial directional errors even after the familiarization block. Such continuously found inaccurate initial movement direction might be correlated with the inability to develop the spatial body map especially for calculating the initial joint torques when starting the reaching movement. Regardless of whether proprioception was impaired or not, all participants could show the stabilized, constant reaching movement trajectories. This highlights the role of proprioception especially in the execution of a planned movement at the early stage of reaching movement.