Letter Representations Research Articles

Mental Rotation of Digitally-Rendered Haptic Objects by the Visually-Impaired.

In the event of visual impairment or blindness, information from other intact senses can be used as substitutes to retrain (and in extremis replace) visual functions. Abilities including reading, mental representation of objects and spatial navigation can be performed using tactile information. Current technologies can convey a restricted library of stimuli, either because they depend on real objects or renderings with low resolution layouts. Digital haptic technologies can overcome such limitations. The applicability of this technology was previously demonstrated in sighted participants. Here, we reasoned that visually-impaired and blind participants can create mental representations of letters presented haptically in normal and mirror-reversed form without the use of any visual information, and mentally manipulate such representations. Visually-impaired and blind volunteers were blindfolded and trained on the haptic tablet with two letters (either L and P or F and G). During testing, they haptically explored on any trial one of the four letters presented at 0°, 90°, 180°, or 270° rotation from upright and indicated if the letter was either in a normal or mirror-reversed form. Rotation angle impacted performance; greater deviation from 0° resulted in greater impairment for trained and untrained normal letters, consistent with mental rotation of these haptically-rendered objects. Performance was also generally less accurate with mirror-reversed stimuli, which was not affected by rotation angle. Our findings demonstrate, for the first time, the suitability of a digital haptic technology in the blind and visually-impaired. Classic devices remain limited in their accessibility and in the flexibility of their applications. We show that mental representations can be generated and manipulated using digital haptic technology. This technology may thus offer an innovative solution to the mitigation of impairments in the visually-impaired, and to the training of skills dependent on mental representations and their spatial manipulation.

The “Inferior Temporal Numeral Area” distinguishes numerals from other character categories during passive viewing: A representational similarity analysis

A region in the posterior inferior temporal gyrus (pITG) is thought to be specialized for processing Arabic numerals, but fMRI studies that compared passive viewing of numerals to other character types (e.g., letters and novel characters) have not found evidence of numeral preference in the pITG. However, recent studies showed that the engagement of the pITG is modulated by attention and task contexts, suggesting that passive viewing paradigms may be ill-suited for examining numeral specialization in the pITG. It is possible, however, that even if the strengths of responses to different category types are similar, the distributed response patterns (i.e., neural representations) in a candidate numeral-preferring pITG region (“pITG-numerals”) may reveal categorical distinctions, even during passive viewing. Using representational similarity analyses with three datasets that share the same task paradigm and stimulus sets (total N ​= ​88), we tested whether the neural representations of digits, letters, and novel characters in pITG-numerals were organized according to visual form and/or conceptual categories (e.g., familiar versus novel, numbers versus others). Small-scale frequentist and Bayesian meta-analyses of our dataset-specific findings revealed that the organization of neural representations in pITG-numerals is unlikely to be described by differences in abstract shape, but can be described by a categorical “digits versus letters” distinction, or even a “digits versus others” distinction (suggesting greater numeral sensitivity). Evidence of greater numeral sensitivity during passive viewing suggest that pITG-numerals is likely part of a neural pathway that has been developed for automatic processing of objects with potential numerical relevance. Given that numerals and letters do not differ categorically in terms of shape, categorical distinction in pITG-numerals during passive viewing must reflect ontogenetic differentiation of symbol set representations based on repeated usage of numbers and letters in differing task contexts.

Iterative Design and Evaluation of a Tangible Robot-Assisted Handwriting Activity for Special Education.

In this article we investigate the role of interactive haptic-enabled tangible robots in supporting the learning of cursive letter writing for children with attention and visuomotor coordination issues. We focus on the two principal aspects of handwriting that are linked to these issues: Visual perception and visuomotor coordination. These aspects, respectively, enhance two features of letter representation in the learner's mind in particular, namely the shape (grapheme) and the dynamics (ductus) of the letter, which constitute the central learning goals in our activity. Building upon an initial design tested with 17 healthy children in a preliminary school, we iteratively ported the activity to an occupational therapy context in 2 different therapy centers, in the context of 3 different summer school camps involving a total of 12 children having writing difficulties. The various iterations allowed us to uncover insights about the design of robot-enhanced writing activities for special education, specifically highlighting the importance of ease of modification of the duration of an activity as well as of adaptable frequency, content, flow and game-play and of providing a range of evaluation test alternatives. Results show that the use of robot-assisted handwriting activities could have a positive impact on the learning of the representation of letters in the context of occupational therapy (V = 1, 449, p < 0.001, r = 0.42). Results also highlight how the design changes made across the iterations affected the outcomes of the handwriting sessions, such as the evaluation of the performances, monitoring of the performances, and the connectedness of the handwriting.

The Development of Morphological Knowledge and Spelling in French.

The Frenchorthographic system is particularly difficult to learn because nearly 30% of words in the lexicon end with a silent letter. One metalinguistic skill that has been identified to facilitate spelling acquisition in French is morphological knowledge. This cross-sectional study investigated the construct of morphological knowledge, its development and its role in building accurate orthographic representations in a sample of francophone elementary students. We proposed that morphological knowledge, a superordinate process, encompasses children’s implicit use of morphemes in everyday language and their conscious, targeted manipulation of morphemes. In the present study, we assessed children’s recognition of morphogrammes, the silent-letter endings (SLEs) of root words that become pronounced in suffixed forms (e.g., the silent t in chant/ʃã/ [song] → chanteur /ʃãtœʀ/ [singer]). When spelling root words, children may mark morphogrammes by recalling morphologically related words in which the morphogramme is not silent – thus, morphological knowledge was hypothesized to positively predict morphogramme spelling. One hundred and twenty-three children in grades 1–3 were assessed on four measures of morphological knowledge, two measures of spelling recognition and a dictation of pseudowords to explore their inclusion of silent-letter endings in novel words. As expected, morphological tasks that required explicit morphological manipulations were harder than implicit ones. Moreover, first graders struggled to complete explicit morphological tasks, while third graders were near ceiling performance on implicit tasks. Nevertheless, the four tasks converged on a single morphological knowledge construct as confirmed by a factor analysis. Importantly, morphological knowledge explained unique variance in children’s accurate representation of silent-letter endings after controlling for grade, reading for pleasure and general orthographic recognition of words. Finally, children rarely used silent-letter endings when spelling pseudowords; however, when they did, they displayed sensitivity to the appropriate phonological context for the letter used. The findings are in accord with theoretical models suggesting that the representations of letters without phonological value are difficult to construct and may remain fuzzy.

Word contexts enhance the neural representation of individual letters in early visual cortex

Visual context facilitates perception, but how this is neurally implemented remains unclear. One example of contextual facilitation is found in reading, where letters are more easily identified when embedded in a word. Bottom-up models explain this word advantage as a post-perceptual decision bias, while top-down models propose that word contexts enhance perception itself. Here, we arbitrate between these accounts by presenting words and nonwords and probing the representational fidelity of individual letters using functional magnetic resonance imaging. In line with top-down models, we find that word contexts enhance letter representations in early visual cortex. Moreover, we observe increased coupling between letter information in visual cortex and brain activity in key areas of the reading network, suggesting these areas may be the source of the enhancement. Our results provide evidence for top-down representational enhancement in word recognition, demonstrating that word contexts can modulate perceptual processing already at the earliest visual regions.

Conditions for cognitive self-organisation implied by visual-word processing

In order to find conditions for biologically plausible, cognitive self-organisation, an adequate representation of the final stage of this process is crucial. The implications of this assumption are analysed for the area of visual-word processing, in particular for position-specific top-down processes from a word – to a letter representation. These processes pose a problem to reviewed models of word reading and computational models in general. A solution in the form of a conceptual network is proposed. In this general model for cognitive brain processes, neural binding of identity and location and of identity and position play a fundamental role: temporary connections emerge during word recognition and are reactivated later, when a letter at given position has to be identified. It is shown how modules active in word recognition are “re-used” in letter identification. In simulations, the role of a critical threshold of cell-assemblies is shown and the selective propagation of activation loops at task-dependent time scales. Requirements for prospective studies on cognitive self-organisation and relations with new empirical work on visual-word processing are discussed.

No Difference in the Neural Underpinnings of Number and Letter Copying in Children: Bayesian Analysis of Functional Near‐Infrared Spectroscopy Data

ABSTRACTIt is under debate whether the neural representation of numbers and letters might rely on distinct neural correlates, or on a mostly shared neural network. In the present study, a total of 47 children in fifth grade (Experiment 1) and sixth grade (Experiment 2) simply copied numbers and letters on a touch screen while brain activation changes were recorded by means of functional near‐infrared spectroscopy (fNIRS). fNIRS data of both experiments and a joint analysis revealed that a shared neural network, particularly in the left hemisphere, was activated in response to both number and letter copying. Interestingly, no difference was observed in brain activation patterns between these two stimuli, as revealed by Bayesian analysis. Our findings indicate that both number and letter copying lead to similar brain activation in children. We further suggest methodological and applied applications of these findings in the frame of educational neuroscience.

Recognition of Handwriting Research: Many Years of Achievement

Previous research indicates that writing practice may be more beneficial than nonmotor practice for letter learning. Here, we report a training study comparing typing, visual, and writing learning conditions in adults (N = 42). We investigated the behavioral consequences of learning modality on literacy learning and evaluated the nature of the learned letter representations. Specifically, the study addressed three questions. First, are the benefits of handwriting practice due to motor learning per se or to other incidental factors? Second, do the benefits generalize to untrained tasks? And third, does handwriting practice lead to learning and strengthening only of motor representations or of other types of representations as well? Our results clearly show that handwriting compared with nonmotor practice produces faster learning and greater generalization to untrained tasks than previously reported. Furthermore, only handwriting practice leads to learning of both motor and amodal symbolic letter representations.

Visual crowding disrupts the cortical representation of letters in early visual areas

Visual crowding disrupts the cortical representation of letters in early visual areas

Mapping visual symbols onto spoken language along the ventral visual stream

Reading involves transforming arbitrary visual symbols into sounds and meanings. This study interrogated the neural representations in ventral occipitotemporal cortex (vOT) that support this transformation process. Twenty-four adults learned to read 2 sets of 24 novel words that shared phonemes and semantic categories but were written in different artificial orthographies. Following 2 wk of training, participants read the trained words while neural activity was measured with functional MRI. Representational similarity analysis on item pairs from the same orthography revealed that right vOT and posterior regions of left vOT were sensitive to basic visual similarity. Left vOT encoded letter identity and representations became more invariant to position along a posterior-to-anterior hierarchy. Item pairs that shared sounds or meanings, but were written in different orthographies with no letters in common, evoked similar neural patterns in anterior left vOT. These results reveal a hierarchical, posterior-to-anterior gradient in vOT, in which representations of letters become increasingly invariant to position and are transformed to convey spoken language information.

Mental Rotation of Digitally-Rendered Haptic Objects.

Sensory substitution is an effective means to rehabilitate many visual functions after visual impairment or blindness. Tactile information, for example, is particularly useful for functions such as reading, mental rotation, shape recognition, or exploration of space. Extant haptic technologies typically rely on real physical objects or pneumatically driven renderings and thus provide a limited library of stimuli to users. New developments in digital haptic technologies now make it possible to actively simulate an unprecedented range of tactile sensations. We provide a proof-of-concept for a new type of technology (hereafter haptic tablet) that renders haptic feedback by modulating the friction of a flat screen through ultrasonic vibrations of varying shapes to create the sensation of texture when the screen is actively explored. We reasoned that participants should be able to create mental representations of letters presented in normal and mirror-reversed haptic form without the use of any visual information and to manipulate such representations in a mental rotation task. Healthy sighted, blindfolded volunteers were trained to discriminate between two letters (either L and P, or F and G; counterbalanced across participants) on a haptic tablet. They then tactually explored all four letters in normal or mirror-reversed form at different rotations (0°, 90°, 180°, and 270°) and indicated letter form (i.e., normal or mirror-reversed) by pressing one of two mouse buttons. We observed the typical effect of rotation angle on object discrimination performance (i.e., greater deviation from 0° resulted in worse performance) for trained letters, consistent with mental rotation of these haptically-rendered objects. We likewise observed generally slower and less accurate performance with mirror-reversed compared to prototypically oriented stimuli. Our findings extend existing research in multisensory object recognition by indicating that a new technology simulating active haptic feedback can support the generation and spatial manipulation of mental representations of objects. Thus, such haptic tablets can offer a new avenue to mitigate visual impairments and train skills dependent on mental object-based representations and their spatial manipulation.

Evidence from masked-priming that initial identification of brand names is via abstract letter identities.

Although visual-word recognition is often assumed to proceed on the basis of case-invariant letter representations, previous research has shown a role for letter-case in recognizing brand names. One recent study reported early effects of letter-case in a brand-decision task using masked primes (Perea etal., 2015, British Journal of Psychology, 106, 162). The present study attempts to replicate this finding using brand names typically presented in all lowercase (e.g., adidas), all uppercase (e.g., IKEA), or titlecase (e.g., Ford). Across three masked-priming experiments, we found no advantage for case-matched identity primes over case-mismatched identity primes. This finding suggests that brand-specific letter-case information does not play a role in the early processing of brand names. However, we observed evidence that case may be used as a cue for making brand decisions, which may explain the effect reported by Perea etal. (2015, British Journal of Psychology, 106, 162).

A deficit in post-graphemic writing processes: Evidence for a graphomotor buffer

ABSTRACTPost-graphemic writing processes transform abstract letter representations into representations of writing movements. We describe an individual with an acquired post-graphemic writing deficit. NGN is normal in spelling words aloud, but impaired in writing words to dictation, with most errors involving letter substitutions (e.g., RUMOR written as BUMOR). NGN’s deficit affects graphic motor plans, which specify the writing strokes for producing letters. Analyses of writing speed, fluency, and stroke patterns suggest that NGN’s errors result from incomplete motor-plan activation. NGN’s error rate is high for the first letter in a word, and declines across subsequent positions. On the basis of this serial position effect and other results, we propose that post-graphemic writing mechanisms include a graphomotor buffer, a writing-specific working memory that holds activated graphic motor plans bound to specific serial positions. We suggest that NGN’s graphomotor buffer is damaged such that early serial positions are affected most severely. Finally, we present results speaking to the roles and capabilities of the graphomotor buffer, and the structure of graphic motor plans.

How does reading expertise influence letter representations in the brain? An fMRI study

How does reading expertise influence letter representations in the brain? An fMRI study

Selective visual representation of letters and words in the left ventral occipito-temporal cortex with intracerebral recordings

We report a comprehensive cartography of selective responses to visual letters and words in the human ventral occipito-temporal cortex (VOTC) with direct neural recordings, clarifying key aspects of the neural basis of reading. Intracerebral recordings were performed in a large group of patients (n = 37) presented with visual words inserted periodically in rapid sequences of pseudofonts, nonwords, or pseudowords, enabling classification of responses at three levels of word processing: letter, prelexical, and lexical. While letter-selective responses are found in much of the VOTC, with a higher proportion in left posterior regions, prelexical/lexical responses are confined to the middle and anterior sections of the left fusiform gyrus. This region overlaps with and extends more anteriorly than the visual word form area typically identified with functional magnetic resonance imaging. In this region, prelexical responses provide evidence for populations of neurons sensitive to the statistical regularity of letter combinations independently of lexical responses to familiar words. Despite extensive sampling in anterior ventral temporal regions, there is no hierarchical organization between prelexical and lexical responses in the left fusiform gyrus. Overall, distinct word processing levels depend on neural populations that are spatially intermingled rather than organized according to a strict postero-anterior hierarchy in the left VOTC.

Analysis of Letter Representation Using Latin and Arabic Scripts: A Masked Priming Study.

Reading plays an essential role in our everyday lives. The aim of this study is to investigate how letters are represented in the brain using the unique characteristics of the Arabic language, which can be written with 2 different scripts. The hypothesis proposed is that the processing of script is sound based: Phonology is what determines letter identity. Using a forward-masked priming paradigm, we showed that Latin-script primes facilitated the recognition of subsequent Arabic-script targets which differed in orthography but shared phonology, thus suggesting a common level of phonological processing. In addition, semantic priming effects were controlled for. The findings thus confirmed our hypothesis and showed that letters that represent the same sound are processed similarly.

Low-Power Sparse Hyperdimensional Encoder for Language Recognition

Editor’s note: Online learning for data analysis, categorization and anomaly detection has become a key technique in a range of adaptive embedded applications. In this article the authors propose a very low power encoder design using a sparse, hyperdimensional representation of letters and words in natural language and they show that this representation and their design can be used with high energy efficiency for a language recognition task. — Axel Jantsch, Royal Institute of Technology Electronics, Computer and Software Systems

Hand finger gesture modeling in advanced CAD system

ABSTRACTThe current paper presents a system for the dynamic simulation of the human hand. The simulation of the human hand offers the capability to acquire handshapes that correspond to letters of the finger alphabet, enabling an integrated representation of words and sentences. The hand model is designed using the Autodesk InventorTM and Autodesk AutoCadTM design environments. The user is able to type words or sentences which are dynamically translated into postures according to the finger alphabet. The system is based on the physiometric characteristics of an average human hand. High precision design is utilized in every part through integration of all the necessary functionalities needed to perform the movements required. The system has been tested on more than 500 words with a letter representation success rate in the range of 95–97%.

A DNA Structural Alphabet Distinguishes Structural Features of DNA Bound to Regulatory Proteins and in the Nucleosome Core Particle.

We analyzed the structural behavior of DNA complexed with regulatory proteins and the nucleosome core particle (NCP). The three-dimensional structures of almost 25 thousand dinucleotide steps from more than 500 sequentially non-redundant crystal structures were classified by using DNA structural alphabet CANA (Conformational Alphabet of Nucleic Acids) and associations between ten CANA letters and sixteen dinucleotide sequences were investigated. The associations showed features discriminating between specific and non-specific binding of DNA to proteins. Important is the specific role of two DNA structural forms, A-DNA, and BII-DNA, represented by the CANA letters AAA and BB2: AAA structures are avoided in non-specific NCP complexes, where the wrapping of the DNA duplex is explained by the periodic occurrence of BB2 every 10.3 steps. In both regulatory and NCP complexes, the extent of bending of the DNA local helical axis does not influence proportional representation of the CANA alphabet letters, namely the relative incidences of AAA and BB2 remain constant in bent and straight duplexes.

How reading changes letter representations: a double dissociation using orthographically distinct scripts in India

How reading changes letter representations: a double dissociation using orthographically distinct scripts in India