The impact of atypical text presentation on transposed-word effects.

When asked to decide if an ungrammatical sequence of words is grammatically correct or not, readers find it more difficult to do so (longer response times (RTs) and more errors) if the ungrammatical sequence is created by transposing two words from a correct sentence (e.g., the white was cat big) compared with matched ungrammatical sequences where transposing two words does not produce a correct sentence (e.g., the white was cat slowly). Here, we provide a further exploration of transposed-word effects when reading unspaced text in Experiment 1, and when reading from right-to-left ("backwards" reading) in Experiment 2. We found significant transposed-word effects in error rates but not in RTs, a pattern previously found in studies using a one-word-at-a-time sequential presentation. We conclude that the absence of transposed-word effects in RTs in the present study and prior work is due to that atypical nature of the way that text was presented. Under the hypothesis that transposed-word effects at least partly reflect a certain amount of parallel word processing during reading, we further suggest that the ability to process words in parallel would require years of exposure to text in its regular format.

Transposed-word effects when reading serially.

When asked to decide if an ungrammatical sequence of words is grammatically correct or not readers find it more difficult to do so (longer response times (RTs) and more errors) if the ungrammatical sequence is created by transposing two words from a correct sentence (e.g., the white was cat big) compared with a set of matched ungrammatical sequences for which transposing any two words could not produce a correct sentence (e.g., the white was cat slowly). Here, we provide a further exploration of transposed-word effects while imposing serial reading by using rapid serial visual presentation (RSVP) in Experiments 1 (respond at the end of the sequence) and 2 (respond as soon as possible-which could be during the sequence). Crucially, in Experiment 3 we compared performance under serial RSVP conditions with parallel presentation of the same stimuli for the same total duration and with the same group of participants. We found robust transposed-word effects in the RSVP conditions tested in all experiments, but only in error rates and not in RTs. This contrasts with the effects found in both errors and RTs in our prior work using parallel presentation, as well as the parallel presentation conditions tested in Experiment 3. We provide a tentative account of why, under conditions that impose a serial word-by-word reading strategy, transposed-word effects are only seen in error rates and not in RTs.

Written Language Acquisition Is Both Shaped by and Has an Impact on Brain Functioning and Cognition.

Spoken language is a distinctive trace of our species and it is naturally acquired during infancy. Written language, in contrast, is artificial, and the correspondences between arbitrary visual symbols and the spoken language for reading and writing should be explicitly learned with external help. In this paper, I present several examples of how written language acquisition is both shaped by and has an impact on brain function and cognition. They show in one hand how our phylogenetic legacy influences education and on the other hand how ontogenetic needs for education can rapidly subdue deeply rooted neurocognitive mechanisms. The understanding of this bidirectional influences provides a more dynamic view of how plasticity interfaces phylogeny and ontogeny in human learning, with implications for both neurosciences and education.

A protocol to examine the learning effects of 'multisystem mapping' training combined with post-training sleep consolidation in beginning readers.

We have recently used randomized controlled trials to examine the impact of a short neuroscience-informed causal intervention using a targeted training to inhibit a deeply rooted visual mechanism (mirror invariance) that hinders literacy acquisition, combined with post-training sleep (for learning consolidation). Using this training protocol, we have shown unprecedented improvements in visual perception of letters, writing, and a two-fold increase in reading fluency in first graders. Here, we describe this ecologically valid school-based intervention protocol to probe inhibition of mirror invariance for letters, including the detailed training instructions, post-training sleep consolidation, as well as practical tips and potential adaptations to different school sizes. For complete details on the use and execution of this protocol, please refer to Torres et al., (2021).

An ERP investigation of transposed-word effects in same-different matching.

Can several words be read in parallel, and if so, how is information about word order encoded under such circumstances? Here we focused on the bottom-up mechanisms involved in word-order encoding under the hypothesis of parallel word processing. We recorded EEG while participants performed a visual same-different matching task with sequences of five words (reference sequence followed by a target sequence each presented for 400 ms). The reference sequence could be grammatically correct or an ungrammatical scrambling of the same words (e.g., he wants these green apples/green wants these he apples). Target sequences for 'different' responses were created by either transposing two words in the reference (e.g., he these wants green apples/green these wants he apples), or by changing two words (e.g., he talks their green apples/green talks their he apples). Different responses were harder to make in the transposition condition, and this transposed-word effect started to emerge around 250 ms post-target onset. The transposed-word effect was first seen on an early onsetting N400 component, with reduced amplitudes (i.e., less negative ERPs) in the transposed condition relative to a two-word replacement condition. A later transposed-word effect was seen on a more temporally widespread positive-going component. Converging behavioral and EEG results showed no effects of reference grammaticality on 'different' responses nor an interaction with transposed-word effects. Our results point to the noisy, bottom-up association of word identities to spatiotopic locations as one means of encoding word order information, and one key source of transposed-word effects.

Selective Inhibition of Mirror Invariance for Letters Consolidated by Sleep Doubles Reading Fluency.

Mirror invariance is a visual mechanism that enables a prompt recognition of mirror images. This visual capacity emerges early in human development, is useful to recognize objects, faces, and places from both left and right perspectives, and is also present in primates, pigeons, and cephalopods. Notwithstanding, the same visual mechanism has been suspected to be the source of a specific difficulty for a relatively recent human invention-reading-by creating confusion between mirror letters (e.g., b-d in the Latin alphabet). Using an ecologically valid school-based design, we show here that mirror invariance represents indeed a major leash for reading fluency acquisition in first graders. Our causal approach, which specifically targeted mirror invariance inhibition for letters, in a synergic combination with post-training sleep to increase learning consolidation, revealed unprecedented improvement in reading fluency, which became two-times faster. This gain was obtained with as little as 7.5 h of multisensory-motor training to distinguish mirror letters, such as "b" versus "d." The magnitude, automaticity, and duration of this mirror discrimination learning were greatly enhanced by sleep, which keeps the gains perfectly intact even after 4 months. The results were consistently replicated in three randomized controlled trials. They not only reveal an extreme case of cognitive plasticity in humans (i.e., the inhibition in just 3 weeks of a ∼25-million-year-old visual mechanism), that allows adaptation to a cultural activity (reading), but at the same time also show a simple and cost-effective way to unleash the reading fluency potential of millions of children worldwide.

On the noisy spatiotopic encoding of word positions during reading: Evidence from the change-detection task.

The present study builds on our prior work showing evidence for noisy word-position coding in an immediate same-different matching task. In that research, participants found it harder to judge that two successive brief presentations of five-word sequences were different when the difference was caused by transposing two adjacent words compared with different word replacements - a transposition effect. Here we used the change-detection task with a 1-s delay introduced between sequences - a task thought to tap into visual short-term memory. Concurrent articulation was used to limit the contribution of active rehearsal. We used standard response-time (RT) and error-rate analyses plus signal detection theory (SDT) measures of discriminability (d') and bias (c). We compared the transposition effects for ungrammatical word sequences and nonword sequences observed with these different measures. Although there was some evidence for transposition effects with nonwords, the effects were much larger with word sequences. These findings provide further support for the hypothesized noisy assignment of word identities to spatiotopic locations along a line of text during reading.

Adults with high functioning autism display idiosyncratic behavioral patterns, neural representations and connectivity of the 'Voice Area' while judging the appropriateness of emotional vocal reactions.

Understanding others in everyday situations requires multiple types of information processing (visual, auditory, higher order…) which implicates the use of multiple neural circuits of the human brain. Here, using a multisensory paradigm we investigate one aspect of social understanding less explored in the literature: instead of focusing on the capacity to infer what a specific person is thinking, we explore here how people with high functioning autism (HFA) and matched controls with typical development (TD) infer the "population thinking". For this we created an audio-visual 'social norm inference' task. Participants were required to imagine how most people would judge the appropriateness of vocal utterances in relation to different emotional visual contexts. Behavioral findings demonstrated that HFA individuals show more interindividual variability in these judgments despite equal within-participant reliability relative to TD. This was also the case for judgements of the valence of these vocalizations when presented in isolation. At the neural level, multivoxel pattern analysis of functional magnetic resonance imaging data revealed strikingly similar neural representations between HFA and TD participants at the group level across different hierarchical levels and neural systems. However, analyses at the individual-participant level revealed that the "Temporal Voice Area" (TVA) shows more interindividual variability in the HFA group, both for neural representations and functional connectivity. Thus, this larger neural idiosyncrasy in a high-level auditory area matches with the larger behavioral idiosyncrasy in HFA individuals, when judging auditory valence and its adequacy in different social scenarios. These results suggest that idiosyncrasy in task-relevant sensory areas in HFA participants could underlie their greater difficulties to estimate how others can think.

A transposed-word effect in same-different judgments to sequences of words.

The present study examined transposed-word effects in a same-different matching task with sequences of 5 words. The word sequences were presented one after the other, each for 400 ms, the first in lowercase and the second in uppercase. The first sequence, the reference, was either a grammatically correct sentence or a scrambled ungrammatical sequence of the same words. The second sequence, the target, was either the same as the reference or differed either by transposing the second and third words or the third and fourth words in the first sequence or by replacing the same 2 words with different words in Experiment 1 or by a single word replacement in Experiment 2. The results showed that "same" responses were easier to make with grammatically correct references and that "different" responses were harder to make when the difference involved a transposition compared with a replacement. This transposed-word effect was found to be independent of reference grammaticality in Experiment 1. Experiment 2 again found a transposed-word effect for ungrammatical sequences, but here the effect was reduced compared with grammatical sequences. The effects found with ungrammatical sequences are taken to reflect the noisy bottom-up association of word identities to locations along a line of text, and this process combines with the influence of top-down grammatical constraints when "different" judgments are harder to make. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Dissociating lexical and sublexical contributions to transposed-word effects.

When two sequences of words are presented successively for 400 ms each, it is harder to decide that the two sequences differ when the difference is generated by transposing two words compared with a condition where the same two words are replaced by different words. Interestingly, this transposed-word effect is obtained even when the first sequence is ungrammatical. One account of the effect seen with ungrammatical sequences is that participants detect mismatching letters rather than words. Under this account, the migration of letter identities across adjacent words would make it harder to judge the transposed-word condition as being different. The present experiment put this account to test by comparing transposition effects to sequences of words vs. pseudowords. We hypothesized that if same-different judgments are made on the basis of sublexical orthographic information only, then we should observe similar effects for words and pseudowords. Although transposition effects were found with pseudoword stimuli, the effects were significantly reduced compared to word sequences. This suggests that the noisy bottom-up allocation of word identities to locations along a line of text is one key mechanism driving transposed-word effects.

Neural Representations Behind 'Social Norm' Inferences In Humans.

Humans are highly skilled in social reasoning, e.g., inferring thoughts of others. This mentalizing ability systematically recruits brain regions such as Temporo-Parietal Junction (TPJ), Precuneus (PC) and medial Prefrontal Cortex (mPFC). Further, posterior mPFC is associated with allocentric mentalizing and conflict monitoring while anterior mPFC is associated with self-reference (egocentric) processing. Here we extend this work to how we reason not just about what one person thinks but about the abstract shared social norm. We apply functional magnetic resonance imaging to investigate neural representations while participants judge the social congruency between emotional auditory utterances in relation to visual scenes according to how 'most people' would perceive it. Behaviorally, judging according to a social norm increased the similarity of response patterns among participants. Multivoxel pattern analysis revealed that social congruency information was not represented in visual and auditory areas, but was clear in most parts of the mentalizing network: TPJ, PC and posterior (but not anterior) mPFC. Furthermore, interindividual variability in anterior mPFC representations was inversely related to the behavioral ability to adjust to the social norm. Our results suggest that social norm inferencing is associated with a distributed and partially individually specific representation of social congruency in the mentalizing network.

A Multitude of Neural Representations Behind Multisensory "Social Norm" Processing.

Humans show a unique capacity to process complex information from multiple sources. Social perception in natural environment provides a good example of such capacity as it typically requires the integration of information from different sensory systems, and also from different levels of sensory processing. Here, instead of studying one isolate system and level of representation, we focused upon a neuroimaging paradigm which allows to capture multiple brain representations simultaneously, i.e., low and high-level processing in two different sensory systems, as well as abstract cognitive processing of congruency. Subjects performed social decisions based on the congruency between auditory and visual processing. Using multivoxel pattern analysis (MVPA) of functional magnetic resonance imaging (fMRI) data, we probed a wide variety of representations. Our results confirmed the expected representations at each level and system according to the literature. Further, beyond the hierarchical organization of the visual, auditory and higher order neural systems, we provide a more nuanced picture of the brain functional architecture. Indeed, brain regions of the same neural system show similarity in their representations, but they also share information with regions from other systems. Further, the strength of neural information varied considerably across domains in a way that was not obviously related to task relevance. For instance, selectivity for task-irrelevant animacy of visual input was very strong. The present approach represents a new way to explore the richness of co-activated brain representations underlying the natural complexity in human cognition.

The Effect of Spatial Smoothing on Representational Similarity in a Simple Motor Paradigm.

Multi-voxel pattern analyses (MVPA) are often performed on unsmoothed data, which is very different from the general practice of large smoothing extents in standard voxel-based analyses. In this report, we studied the effect of smoothing on MVPA results in a motor paradigm. Subjects pressed four buttons with two different fingers of the two hands in response to auditory commands. Overall, independent of the degree of smoothing, correlational MVPA showed distinctive patterns for the different hands in all studied regions of interest (motor cortex, prefrontal cortex, and auditory cortices). With regard to the effect of smoothing, our findings suggest that results from correlational MVPA show a minor sensitivity to smoothing. Moderate amounts of smoothing (in this case, 1-4 times the voxel size) improved MVPA correlations, from a slight improvement to large improvements depending on the region involved. None of the regions showed signs of a detrimental effect of moderate levels of smoothing. Even higher amounts of smoothing sometimes had a positive effect, most clearly in low-level auditory cortex. We conclude that smoothing seems to have a minor positive effect on MVPA results, thus researchers should be mindful about the choices they make regarding the level of smoothing.

Exploring the Use of Sensorial LTP/LTD-Like Stimulation to Modulate Human Performance for Complex Visual Stimuli.

Is it possible to passively induce visual learning/unlearning in humans for complex stimuli such as faces? We addressed this question in a series of behavioral studies using passive visual stimulation (flickering of faces at specific temporal frequencies) inspired by well-known synaptic mechanisms of learning: long-term potentiation (LTP) vs long-term depression (LTD). We administered a face identity change detection task before and after a passive stimulation protocol to test for potential changes in visual performance. First, with bilateral stimulation, subjects undergoing high-frequency LTP-like stimulation outperformed those submitted to low-frequency LTD-like stimulation despite equivalent baseline performance (exp. 1). Second, unilateral stimulation replicated the differential modulation of performance, but in a hemifield-specific way (exp. 2). Third, for both stimulation groups, a sudden temporary drop in performance on the stimulated side immediately after the stimulation, followed by progressive recovering, can suggest either 'visual fatigue' or 'face adaptation' effects due to the stimulation. Fourth, we tested the life-time of these modulatory effects, revealing they vanish after one hour delay (exp. 3). Fifth, a control study (exp. 4) using low-level visual stimuli also failed to show longer-term effects of sensory stimulation, despite reports of strong effects in the literature. Future studies should determine the necessary and sufficient conditions enabling robust long-term modulation of visual performance using this technique. This step is required to consider further use in fundamental research (e.g., to study neural circuits involved in selective visual processing) and potential educational or clinical applications (e.g., inhibiting socially-irrelevant aspects of face processing in autism).

The Search for the Face of the Visual Homunculus.

The functional organization within face-sensitive regions in the brain is largely unknown. A new fMRI study provided evidence that a face-selective region contains neighboring patches of cortex that encode physically neighboring face features. We suggest that multiple mechanisms should be considered for a full understanding of the functional maps in face-selective cortex.

Timing the impact of literacy on visual processing.

Learning to read requires the acquisition of an efficient visual procedure for quickly recognizing fine print. Thus, reading practice could induce a perceptual learning effect in early vision. Using functional magnetic resonance imaging (fMRI) in literate and illiterate adults, we previously demonstrated an impact of reading acquisition on both high- and low-level occipitotemporal visual areas, but could not resolve the time course of these effects. To clarify whether literacy affects early vs. late stages of visual processing, we measured event-related potentials to various categories of visual stimuli in healthy adults with variable levels of literacy, including completely illiterate subjects, early-schooled literate subjects, and subjects who learned to read in adulthood (ex-illiterates). The stimuli included written letter strings forming pseudowords, on which literacy is expected to have a major impact, as well as faces, houses, tools, checkerboards, and false fonts. To evaluate the precision with which these stimuli were encoded, we studied repetition effects by presenting the stimuli in pairs composed of repeated, mirrored, or unrelated pictures from the same category. The results indicate that reading ability is correlated with a broad enhancement of early visual processing, including increased repetition suppression, suggesting better exemplar discrimination, and increased mirror discrimination, as early as ∼ 100-150 ms in the left occipitotemporal region. These effects were found with letter strings and false fonts, but also were partially generalized to other visual categories. Thus, learning to read affects the magnitude, precision, and invariance of early visual processing.

Literacy breaks mirror invariance for visual stimuli: a behavioral study with adult illiterates.

The ability to recognize 2 mirror images as the same picture across left-right inversions exists early on in humans and other primates. In order to learn to read, however, one must discriminate the left-right orientation of letters and distinguish, for instance, b from d. We therefore reasoned that literacy may entail a loss of mirror invariance. To evaluate this hypothesis, we asked adult literates, illiterates, and ex-illiterates to perform a speeded same-different task with letter strings, false fonts, and pictures regardless of their orientation (i.e., they had to respond "same" to mirror pairs such as "iblo oldi"). Literates presented clear difficulties with mirror invariance. This "mirror cost" effect was strongest with letter strings, but crucially, it was also observed with false fonts and even with pictures. In contrast, illiterates did not present any cost for mirror pairs. Interestingly, subjects who learned to read as adults also exhibited a mirror cost, suggesting that modest reading practice, late in life, can suffice to break mirror invariance.

Universal brain systems for recognizing word shapes and handwriting gestures during reading.

Do the neural circuits for reading vary across culture? Reading of visually complex writing systems such as Chinese has been proposed to rely on areas outside the classical left-hemisphere network for alphabetic reading. Here, however, we show that, once potential confounds in cross-cultural comparisons are controlled for by presenting handwritten stimuli to both Chinese and French readers, the underlying network for visual word recognition may be more universal than previously suspected. Using functional magnetic resonance imaging in a semantic task with words written in cursive font, we demonstrate that two universal circuits, a shape recognition system (reading by eye) and a gesture recognition system (reading by hand), are similarly activated and show identical patterns of activation and repetition priming in the two language groups. These activations cover most of the brain regions previously associated with culture-specific tuning. Our results point to an extended reading network that invariably comprises the occipitotemporal visual word-form system, which is sensitive to well-formed static letter strings, and a distinct left premotor region, Exner's area, which is sensitive to the forward or backward direction with which cursive letters are dynamically presented. These findings suggest that cultural effects in reading merely modulate a fixed set of invariant macroscopic brain circuits, depending on surface features of orthographies.