Letter Rotation Research Articles

Emerging Technology Enabling Dyslexia Users To Read and Perceive Written Text Correctly

Dyslexia is treated by many specialists as a cognitive impairment involving visual attention deficit. It may cause an image of letter rotation or overlapping. Both children and adults suffer from this disease, differing in individual needs and seriousness. With a growing amount of information being distributed digitally, there is a need to accommodate online text to dyslexic users. However, with different types of operating systems, web browsers and substantial dyslexia individualism, it is not easy to fully automatize such needs. We are developing an extension for Chrome browser which is based on our previous cognitive research and empirical data. Such an extension will allow users with dyslexia to accommodate web content with special fragmentation sign which demonstrably suppresses reading problems caused (not only) by dyslexia.

Different Effects of Hypoxia on Mental Rotation of Normal and Mirrored Letters: Evidence from the Rotation-Related Negativity.

The present study explored the neural mechanism underlying the effect of moderate and transient hypoxic exposure on mental rotation of two-dimensional letters in both normal and mirror versions. Event-related potential data and behavioral data were acquired in the task of discrimination between normal and mirrored versions separately in conditions of normoxia (simulated sea level) and hypoxia conditions (simulated 5000 meter altitude). The behavioral results revealed no significant difference between the normoxia and hypoxia conditions both in response time and error rate. However, obvious differences between these two conditions in ERP were found. First, enlarged P300 and Rotation-related Negativity (RRN) were observed in the hypoxia condition compared to the normoxia condition only with normal letters. Second, the angle effect on the amplitude of RRN was more evident with normal letters in the hypoxia condition than that in the normoxia condition. However, this angle effect nearly disappeared with the mirrored letters in the hypoxia condition. Third, more bilateral parietal activation was observed in the hypoxia condition than the normoxia condition. These results suggested that the compensation mechanism existed in the hypoxia condition and was effective with normal letters but had little effect on the mirrored letters. This study extends the research about the hypoxic effect on spatial ability of humans by employing a mental rotation task and further provides neural evidence for this effect.

When I am (almost) 64: The effect of normal ageing on implicit motor imagery in young elderlies

Motor imagery (M.I.) is a cognitive process in which movements are mentally evoked without overt actions. Behavioral and fMRI studies show a decline of explicit M.I. ability (e.g., the mental rehearsal of finger oppositions) with normal ageing: this decline is accompanied by the recruitment of additional cortical networks.However, none of these studies investigated behavioral and the related fMRI ageing modifications in implicit M.I. tasks, like the hand laterality task (HLT).To address this issue, we performed a behavioral and fMRI study: 27 younger subjects (mean age: 31 years) and 29 older subjects (mean age: 61 years) underwent two event-related design fMRI experiments. In the HLT, participants were asked to decide whether a hand rotated at different angles was a left or right hand. To test the specificity of any age related difference in the HLT, we used a letter rotation task as a control experiment: here subjects had to decide whether rotated letters were presented in a standard or a mirror orientation.We did not find any group difference in either behavioral task; however, we found significant additional neural activation in the elderly group in occipito-temporal regions: these differences were stronger for the HLT rather than for the LRT with group by task interactions effects in right occipital cortices.We interpret these results as evidence of compensatory processes associated with ageing that permit a behavioral performance comparable to that of younger subjects. This process appears to be more marked when the task specifically involves motor representations, even when these are implicitly evoked.

Cognitive mapping deficits in schizophrenia: Evidence from clinical correlates of visuospatial transformations

The ‘cognitive mapping’ component of spatial cognition, namely – the allocentric/egocentric function and its relation to symptoms in schizophrenia is relatively unexplored. In this study, we compared schizophrenia patients (N=44) to demographically-matched healthy controls (N=43) using computer-administered visuospatial transformation tasks with egocentric and allocentric components and analyzed their correlation with symptoms. Significant diagnosis X task-type interaction effect was seen on task accuracy. Patients performed significantly worse than controls in the allocentric letter rotation task (LRT) but not in the egocentric people rotation task (PRT). Accuracy in the LRT was significantly lesser than in PRT among patients but not among controls. Patients were significantly slower as compared to controls in both tasks. Both groups took longer to perform PRT as compared to LRT. LRT accuracy showed significant negative correlation with total positive symptoms as well as negative symptoms scores. Angle of rotation, perspective (front-facing/back-facing), orientation (mirrored/normal), and stimulus type (letter/number) were found to significantly influence performance in both groups of subjects. The present data support the finding that there is a differential impairment of allocentric abilities in schizophrenia patients. Further systematic research in this area may facilitate better understanding of schizophrenia pathogenesis.

Mental rotation of letters, body parts and scenes during whole-body tilt: Role of a body-centered versus a gravitational reference frame

It is known that in mental-rotation tasks, subjects mentally transform the displayed material until it appears “upright” and then make a judgment. Here we evaluate, by using three typical mental rotation tasks with different degrees of embodiment, whether “upright” is coded to a gravitational or egocentric reference frame, or a combination of both. Observers stood erect or were whole-body tilted by 60°, with their left ear down. In either posture, they saw stimuli presented at different orientation angles in their frontal plane: in condition LETTER, they judged whether the stimuli were normal or mirror-reversed letters, in condition HAND whether they represented a left or a right hand, and in condition SCENE whether a weapon laid left or right in front of a displayed person. Data confirm that reaction times are modulated by stimulus orientation angle, and the modulation curve in LETTER and HAND differs from that in SCENE. More importantly, during 60° body tilt, the modulation curve shifted 12° away from the gravitational towards the egocentric vertical reference; this shift was comparable in all three conditions and independent of the degree of embodiment. We conclude that mental rotation in all conditions relied on a similar spatial reference, which seems to be a weighted average of the gravitational and the egocentric vertical, with a higher weight given to the former.

Neurocognitive impairment of mental rotation in major depressive disorder: evidence from event-related brain potentials.

Mental rotation performance may be used as an index of mental slowing or bradyphrenia and may reflect speed of motor preparation. Previous studies suggest that major depressive disorder (MDD) presents correlates of impaired behavioral performance for mental rotation and psychomotor disturbance. Very little is known about the electrophysiological mechanism underlying this deficit. The present study was the first to investigate the event-related brain potential (ERP) correlates of mental rotation and their mental slowing or bradyphrenia in MDD. ERPs were recorded while we tested 25 MDD patients and 26 healthy controls by evaluating the performance of MDD patients on hand and letter rotation tasks at different orientations, and their 400-to-600-msec time window was measured and analyzed for latencies and peak amplitudes over the electrodes. First, individuals with MDD were slower and made more errors in mentally rotating hands and letters than healthy controls did, and individuals with MDD exhibited a greater difference in response times and errors than controls did between hands and letters. Second, the mean peak amplitude was significantly lower and the mean latency was significantly longer in the 400-to-600-msec time window at the parietal site in the hand tasks in MDD patients than in controls, but this was not seen in the letter task, with only lower mean peak amplitude. MDD patients present the absence of a typical mental rotation function for the amplitude of the rotation-related negativity in the hand and letter tasks. Third, the scalp activity maps in MDD patients exhibited the absence of activation in the left parietal site for the mental rotation of hands, as shown in healthy participants. In contrast, their brain activation for the letter task was similar to those of healthy participants. These data suggest that mental imagery of hands and letters relies on different cognitive and neural mechanisms and indicate that the left posterior parietal lobe is a necessary structure for mental transformations of human hands. Importantly, MDD deficits were more seriously present specific to the hands than the letters. Such impairment may also be an important and possibly defining marker of MDD in particular.

The role of embodied simulation in mental transformation of whole-body images: Evidence from Parkinson’s disease

It has been repeatedly demonstrated that mentally performing an action and mentally transforming body-parts entail simulation of one’s own body movements, consistent with predictions of embodied cognition theories. However, the involvement of embodied simulation in mental transformation of whole-body images is still disputed. Here, we assessed own body transformation in Parkinson’s disease (PD) patients with symptoms most affecting the left or the right body side. PD patients were required to perform left–right judgments on front-facing or back-facing human figures, and a letter rotation task. Results demonstrated that PD patients were selectively impaired in judging the side of back-facing human figures corresponding to their own most affected side, but performed as well as healthy subjects on mental transformation of front-facing bodies and on letter rotation. These findings demonstrate a parallel impairment between motor and mental simulation mechanisms in PD patients, thus highlighting the specific contribution of embodied cognition to mental transformation of whole-body images.

Motor Imagery in Asperger Syndrome: Testing Action Simulation by the Hand Laterality Task

Asperger syndrome (AS) is a neurodevelopmental condition within the Autism Spectrum Disorders (ASD) characterized by specific difficulties in social interaction, communication and behavioural control. In recent years, it has been suggested that ASD is related to a dysfunction of action simulation processes, but studies employing imitation or action observation tasks provided mixed results. Here, we addressed action simulation processes in adolescents with AS by means of a motor imagery task, the classical hand laterality task (to decide whether a rotated hand image is left or right); mental rotation of letters was also evaluated. As a specific marker of action simulation in hand rotation, we assessed the so-called biomechanical effect, that is the advantage for judging hand pictures showing physically comfortable versus physically awkward positions. We found the biomechanical effect in typically-developing participants but not in participants with AS. Overall performance on both hand laterality and letter rotation tasks, instead, did not differ in the two groups. These findings demonstrated a specific alteration of motor imagery skills in AS. We suggest that impaired mental simulation and imitation of goal-less movements in ASD could be related to shared cognitive mechanisms.

EEG coherence during mental rotation of letters, hands and scenes

The purpose of the present study was to investigate differences in the electrocortical synchronization pattern during mental rotation of three different object categories as well as six different rotation angles. Therefore, event-related coherence of the electroencephalographic (EEG) activity between selective frontal and parietal electrode pairs of ten subjects was measured during the performance of a mental rotation task consisting of rotation of letters, hands and scenes. Statistical analysis showed an increased coherence of frontal and parietal electrode pairs for the condition LETTER in comparison to the other conditions in the alpha1- (8.5–10Hz) and alpha2-band (10, 5–12Hz) supporting the notion of different mental rotation mechanisms for externally and internally represented objects. Additionally decreased coherence of the frontal and parietal electrode pairs was found for the rotation angles 30° to 150° in comparison to the 0° and 180° rotations for the alpha1- and alpha2-band as well as the gamma frequency band (30–45Hz). It is assumed that this decrease of synchronization reflects the mental rotation process implying that the mental rotation process of 180° differs from the rotation process of all other rotation angles.

Developmental changes of the biomechanical effect in motor imagery

Motor imagery has been investigated in childhood and early adolescence, but not across adolescence stages; moreover, available evidence did not clarify whether the involvement of motor information in mental rotation of body parts becomes stronger or weaker during development. In the present study, we employed the hand laterality task to assess motor imagery in ninety-seven typically developing adolescents divided into three age groups (i.e., 11-12, 14-15, and 17-18 years); mental rotation of objects and letters were also assessed. As a specific marker of the motor involvement in mental rotation of body parts, we assessed the so-called biomechanical effect, that is, the advantage for judging hand pictures showing physically comfortable positions with respect to hand pictures showing physically impossible or awkward positions. Results demonstrated that the biomechanical effect did not significantly affect early adolescents' performance, whereas it became significant in 14- to 15-year-old participants and even more stronger in 17- to 18-year-old participants; this pattern did not depend on an increase in processing speed to mentally rotate both corporeal and non-corporeal (objects and letters) stimuli. The present findings demonstrated that: (1) motor imagery undergoes a continuous and progressive refinement throughout adolescence, and (2) full exploitation of motor information to mentally transform corporeal stimuli can be attained in late adolescence only.

Mental rotation of a letter, hand and complex scene in microgravity

Previous studies showed egocentric but not allocentric mental rotation tasks to be impaired in microgravity when feedback cues about vertical surroundings were restricted. Those studies are difficult to reconcile, however, since they were limited not only to small subject groups, but also differed dramatically in design. According to this lack, the present study was conducted in order to compare three typical egocentric and allocentric mental rotation stimuli in microgravity within a single experiment and using the same subjects and setup conditions. In order to simulate astronauts’ working conditions in space, visual and tactile vertical references were provided. Six subjects mentally rotated letters, body parts, and complex scenes in parabolic flight during near-weightlessness and level flight conditions. Subjects viewed letters and judged whether they were mirror-reversed or not (task LETTER), viewed pictures of a hand and assessed whether it was a right or a left hand (task HAND), and viewed drawings of a person at a table that contained both a weapon and a rose and had to decide whether the weapon was on the right or left side of the table (task SCENE). Material could be in canonical orientation or rotated from 0° up to 180° in ±60° steps. We calculated reaction times and error scores for each task, orientation in each condition, and performed additionally intra-subject correlations between reaction times of both conditions for each task. We found typical reaction times and error scores for each stimulus category with increasing rotation level. More importantly, response time and error score were not impaired in microgravity, independent of stimulus type and orientation. This finding is further confirmed by correlation analysis. We conclude that the mental rotation of letters, hand shapes, and complex scenes is not affected by short periods in microgravity when visual and tactile vertical references are provided. This finding is relevant for astronauts who are normally aware of their surroundings, and it is in accordance with previous findings, where only egocentric stimuli were impaired in microgravity when sensory cues about the vertical reference were restricted.

Mental rotation of letters, body parts and complex scenes: Separate or common mechanisms?

This study compares mental rotation with three stimuli: letters, body parts and complex scenes. Twenty-four subjects saw letters and judged whether they were mirror-reversed or not (task LETTER), saw pictures of a hand and indicated whether it was a right or a left one (task HAND), and saw drawings of a person at a table on which a weapon and a rose laid and decided whether the weapon was to the person’s right or left (task SCENE). Stimuli were presented in canonical orientation or rotated by up to 180°. Our analyses focused on intra-subject correlations between reaction times of the different tasks. We found that reaction times for stimuli in canonical orientation co-varied in HAND and LETTER, the increase of reaction times with increasing object rotation co-varied in HAND and SCENE, and reaction times for 180° rotations co-varied between all tasks. We suggest that basic processes like visual perception and decision-making are distinct for scenes versus letters and body parts, that the mechanism for mental rotation of letters is distinct from that for mental self- and body part rotation, and suggest an extra mechanism for 180° rotations that shared among all tasks. These findings confirm and expand hypotheses about mental rotation that were based on comparisons of between-subject means.

Preschoolers' mental rotation of letters: Sex differences in hemispheric asymmetry

Adults' mental rotation performance has been found to produce one of the largest sex differences in cognition accompanied by sex differences in functional cerebral asymmetry. In this study sex differences in mental rotation of letters were investigated with children as young as five years. Based on the electrophysiological brain correlates of mental rotation, we observed a bilateral brain activity for preschool girls whereas the preschool boys' brain activity was clearly lateralized towards the right hemisphere if and only if mental rotation was needed to solve the task. At the same time, we did not find any sex differences in mental rotation speed or accuracy. Thus, sex differences in functional hemispheric asymmetry during mental rotation do not require hormonal changes that occur during puberty.

Empathy, schizotypy, and visuospatial transformations

Introduction. Adopting another person's visuospatial perspective has been associated with empathy, which involves adopting the psychological perspective of another individual. Both reduced empathy and abnormal visuospatial processing have been observed in those with schizophrenia and schizophrenia-related personality traits. In the current study, we sought to explore the relationship between empathy, schizotypy, and visuospatial transformation ability. Methods. 32 subjects (16 women) performed a visuospatial perspective-taking task and a mental letter rotation task. Response times and accuracy were analysed in relation to dimensions of self-reported empathy, indexed using the Interpersonal Reactivity Index, and schizotypy, as measured by the Schizotypal Personality Questionnaire. Results. We found that: (1) greater cognitive and affective empathy were associated with reduced negative schizotypy, and, in men, greater cognitive empathy was associated with reduced positive schizotypy; (2) improved accuracy for imagined self–other transformations in the perspective-taking task was associated with greater self-reported cognitive empathy in women and higher positive schizotypy across genders; (3) faster mental letter rotation was associated with reduced cognitive empathy and increased negative schizotypy in women. Conclusions. Together, the findings partially support the commonalities in visuospatial transformation ability, empathy, and schizotypy, and posit an interesting link between spatial manipulations of our internal representations and interactions with the physical world.

Action observation improves motor imagery: specific interactions between simulative processes

In the present study, we demonstrated that observation of hand rotation had specific facilitation effects on a classical motor imagery task, the hand-laterality judgement. In Experiment 1, we found that action observation improved subjects' performance on the hand laterality but not on the letter rotation task (stimulus specificity). In Experiment 2, we demonstrated that this facilitation was not due to mere observation of a moving hand, because it was triggered by observation of manual rotation but not of manual prehension movements (motion specificity). In Experiment 3, this stimulus- and motion-specific effect was found to be right hand-specific, compatible with left-hemispheric specialization in motor imagery but not in action observation. These data provided direct support to the idea that different simulation states, such as action observation and motor imagery, share some common mechanisms but also show specific functional differences.

The Effect of Global Precedence on Mental Rotation of Compound Stimuli

Perceptual global precedence referred to a priority in perceptual processing for the global features of a form or object. This phenomenon was firstly reported by Navon (1977) with compound stimuli (larger letters were constructed from smaller letters,e.g.,a large H made up of small Ss). Navon required observers to identify either the large (i.e.,global) or the small (i.e.,local) letters and found that global letters were identified more rapidly than local letters and also that irrelevant global letters were more difficult to ignore than irrelevant local letters. Perceptual global precedence had been widely replicated within certain boundary conditions (Dalrymple et al.,2007; Roalf et al,2006; Schatz Erlandson,2003; Han Shihui Chen Lin,1996; Kimchi,1992). However,it was still unclear that whether global precedence could exist in other higher cognitive processes,such as mental rotation. Mental rotation was one typical transformation of mental images,which was reported to be functional equivalence with visual perception. Whether there was an effect of global precedence on mental rotation was explored in the present research. Compound stimuli combined with rotation task were used in two experiments. Participants were required to judge whether the large letter or small letter of the compound stimulus was in its regular format or left-right mirror. In Experiment 1,2 (task:identification of normal image /mirror-reversed image for large or small letters )×2 (stimuli :congruence or incongruence of large-small letters) was designed to eliminate perceptual global precedence through prolonging the duration of target stimuli. Experiment 2 investigated the global precedence on mental rotation with a 4 (rotation degree:0,60,120,180 )×2 (rotation pattern:rotation of large letters or small letters)×2 (stimuli:congruence or incongruence of rotation angles of large-small letters) within-subject factorial design. Repeated measures analyses of variance were conducted separately for the two experiments. In experiment 1,perceptual global precedence could be eliminated by prolonging targets' duration. There was no significant difference between the RTs of identification of normal image for large and small letters,and the congruity of large-small letters had no effect on identification of normal image for large and small letters. However,in experiment 2,when mental rotation was added to the task,large letters were responded more quickly than small letters,though the congruity of rotation angles of large-small letters didn't influence the rotation of large and small letters; in addition,the difference between the rotation speeds of the large letters and small letters reached a marginal significant level. Based on these results,the conclusion was that global precedence did exist in mental rotation even when perceptual global precedence was excluded in mental rotation task. Time required in global rotation was much shorter than that in local rotation. In addition,neither large letters rotation nor small letters rotation was influenced by the congruity of rotation angles of large-small letters. That was to say,the global precedence in mental rotation was of a little difference from the perceptual global precedence. The present findings not only extended the field of mental image,but also shed light on the research of global precedence in higher cognitive processes,and the method of eliminating perceptual global precedence was also of great significance for future research.

Double Dissociation between Motor and Visual Imagery in the Posterior Parietal Cortex

Because motor imagery (MI) and visual imagery (VI) are influenced differently by factors such as biomechanical constraints or stimulus size, it is conceivable that they rely on separate processes, possibly involving distinct cortical networks, a view corroborated by neuroimaging and neuropsychological studies. In the posterior parietal cortex, it has been suggested that the superior parietal lobule (SPL) underlies VI, whereas MI relies on the supramarginalis gyrus (SMG). However, because several brain imaging studies have also shown an overlap of activations in SPL and SMG during VI or MI, the question arises as to which extent these 2 subregions really contribute to distinct imagery processes. To address this issue, we used repetitive transcranial magnetic stimulation to induce virtual lesions of either SMG or SPL in subjects performing a MI (hand drawing rotation) or a VI (letter rotation) task. Whatever hemisphere was stimulated, SMG lesions selectively altered MI, whereas SPL lesions only affected VI, demonstrating a double dissociation between MI and VI. Because these deficits were not influenced by the angular distance of the stimuli, we suggest that SMG and SPL are involved in the reenactment of the motor and visual representations, respectively, and not in mental rotation processes per se.

Motor Imagery Development in Primary School Children

Motor imagery provides a unique window on the integrity of movement representation. How this ability unfolds during development remains unknown, however. It was the aim of this cross-sectional study to chart the development of movement imagery over childhood using validated measures, and to examine its relationship to movement skill. A sample of 58 children aged 7–12 years were recruited from Australian primary schools. Motor imagery ability was assessed using the Radial Pointing Task and a (mental) Hand Rotation Task, whereas visual (or object-related) imagery was measured on a Letter Rotation Task. Motor skill was assessed on the McCarron Assessment of Neuromuscular Development (MAND). Results showed clear age differences on all measures: motor skill, motor imagery, and visual imagery. The relationship between motor imagery and motor skill was shown to become stronger with age, whereas no relationship between visual imagery and motor skill was evident at any age. Taken together, these results show that motor imagery has a distinct developmental trajectory that is entwined with the development of movement skill in children. We argue that movement imagery reflects the unfolding of internal modeling processes providing the foundation for adaptive, goal-directed movements.

THE PROCESSING-STORAGE RELATIONSHIP IN WORKING MEMORY SPAN: FROM A PERSPECTIVE OF A REPRESENTATION-BASED INTERFERENCE VIEW

Recent studies using working memory (WM) span tests have reported that processing activities negatively affected memory performance on the one hand and storage activities adversely affected processing efficiency on the other hand. We examined this processing-storage relationship in two WM span tests that required participants to maintain spatial or verbal memory items while engaging in mental letter rotation, focusing on an interference effect derived from this visuospatial processing task. Results showed that the mental letter rotation task interfered with memory of verbal as well as spatial items, indicating the similarity of these two span tests. Furthermore, the two span tests produced a proportional slowdown in processing speed toward the end of each span list. We discussed possible mechanisms in which the processing and maintenance activities disturb each other from the perspectives of domain-specific representation-based interference and domain-general attentional switching in working memory.

Central executive involvement in children's spatial memory

Previous research with adults found that spatial short-term and working memory tasks impose similar demands on executive resources. We administered spatial short-term and working memory tasks to 8- and 11-year-olds in three separate experiments. In Experiments 1 and 2 an executive suppression task (random number generation) was found to impair performances on a short-term memory task (Corsi blocks), a working memory task (letter rotation), and a spatial visualisation task (paper folding). In Experiment 3 an articulatory suppression task only impaired performance on the working memory task. These results suggest that short-term and working memory performances are dependent on executive resources. The degree to which the short-term memory task was dependent on executive resources was expected to be related to the amount of experience children have had with such tasks. Yet we found no significant age-related suppression effects. This was attributed to differences in employment of cognitive strategies by the older children.