Developmental language disorder and neurodiversity: Surfacing contradictions, tensions and unanswered questions.

BACKGROUND: Neurodiversity is increasingly discussed in relation to autism research and practice. However, there is a lack of scholarship concerning the neurodevelopmental condition of Developmental Language Disorder (DLD) and the neurodiversity movement. While this movement may hold opportunities for the DLD community, the application of the concept of neurodiversity to DLD research and practice needs consideration, as DLD and autism have very different levels of public and professional awareness and understanding. AIMS: In this article, we discuss what the concept of neurodiversity and the associated neurodiversity movement could mean for DLD research and practice. We aim to critique some assumptions that may arise from the application of neurodiversity principles (or assumed principles) to the field of DLD. METHODS: This is a discussion paper, drawing on the personal experiences and reflections of the author team. MAIN CONTRIBUTIONS: We make the case for why DLD should be included in discussions about neurodivergence and outline considerations for doing so, and why some issues and applications may be particular to DLD. We outline points of similarity and contrast with autism in relation to our understanding of neurodiversity. We consider the issues around diagnosis and terminology and urge practitioners to continue to diagnose DLD using currently agreed terminology, so as not to undermine recent awareness efforts. We note that a neurodiversity-informed perspective challenges us to offer interventions that operate at the level of our environments, not just at the level of an individual. Indeed, neurodiversity offers a platform to argue for better rights and more inclusive spaces in mental health settings, education and work for children and adults with DLD. CONCLUSIONS: DLD should be considered from a neurodiversity-informed perspective, and it is our hope that this will lead to neurodiversity-affirming practice that will afford young people with DLD better understanding from members of the public and the professionals who work with them. Further work is needed to better support children, young people and adults with DLD to have a voice in the neurodiversity movement. WHAT THIS PAPER ADDS: What is already known on the subject Neurodiversity approaches are increasingly being taken up in research and practice in relation to autism, meaning that our understanding of autism and how autistic people are supported is increasingly drawing on the principles of neurodiversity. However, autism is not the only neurodivergent population. Developmental Language Disorder (DLD) is another neurodevelopmental condition; however, relative to autism, DLD has lower awareness amongst professionals and the public. There has been no scholarship that has examined DLD through the lens of neurodiversity, or considered the application of neurodiversity-affirming approaches to DLD. What this paper adds to existing knowledge In this paper, we examine what the neurodiversity movement means for DLD research and practice. In particular, we consider what neurodiversity in the field of autism might teach us about the application of neurodiversity in the field of DLD, and highlight where we believe there are important differences between the two populations. We reflect on what neurodiversity means for intervention, diagnosis, terminology and championing the need for accessibility, especially with regard to mental health support, education and employment. What are the potential or actual clinical implications of this work? Neurodiversity highlights the need to consider interventions at the level of an individual's environment (e.g., how can we make this space more inclusive?) as well as interventions operating at the level of the individual themselves (e.g., interventions focusing on an individual's language skills). We challenge the notion that neurodiversity-affirming approaches mean not diagnosing DLD or changing DLD's terminology: we argue that this is not in the spirit of the original neurodiversity movement, but also that for a condition with such low public awareness, these actions could do more harm than good for families affected by DLD. We call for more in-depth scholarship and discussion around the application of neurodiversity approaches to DLD and argue that the neurodiversity movement offers an important opportunity to raise better awareness and understanding of DLD in multiple sectors, including (but not limited to) mental health, education and employment.

Temporal dynamics of normalization reweighting.

For decades, neural suppression in early visual cortex has been thought to be fixed. But recent work has challenged this assumption by showing that suppression can be reweighted based on recent history; when pairs of stimuli are repeatedly presented together, suppression between them strengthens. Here we investigate the temporal dynamics of this process using a steady-state visual evoked potential (SSVEP) paradigm that provides a time-resolved, direct index of suppression between pairs of stimuli flickering at different frequencies (5 and 7 Hz). Our initial analysis of an existing electroencephalography (EEG) dataset (N = 100) indicated that suppression increases substantially during the first 2-5 seconds of stimulus presentation (with some variation across stimulation frequency). We then collected new EEG data (N = 100) replicating this finding for both monocular and dichoptic mask arrangements in a preregistered study designed to measure reweighting. A third experiment (N = 20) used source-localized magnetoencephalography and found that these effects are apparent in primary visual cortex (V1), consistent with results from neurophysiological work. Because long-standing theories propose inhibition/excitation differences in autism, we also compared reweighting between individuals with high versus low autistic traits, and with and without an autism diagnosis, across our three datasets (total N = 220). We find no compelling differences in reweighting that are associated with autism. Our results support the normalization reweighting model and indicate that for prolonged stimulation, increases in suppression occur on the order of 2-5 seconds after stimulus onset.

Camouflaging in Developmental Language Disorder: The Views of Speech and Language Pathologists and Parents.

The term camouflaging describes behaviors that cover up neurodivergent difficulties. While researched in autism, camouflaging has received no systematic study in other conditions affecting communication, including developmental language disorder (DLD). This study explored camouflaging in DLD, drawing on the experience and expertise of speech and language pathologists and parents of children with DLD. Using a qualitative descriptive design, we interviewed six speech and language pathologists and six parents of children with DLD. The inductive thematic analysis considered three broad topic areas: What camouflaging behaviors do children with DLD do, the impacts of camouflaging, and what factors are associated with camouflaging. Camouflaging took a range of forms, with eight common presentations identified. Camouflaging reportedly delayed recognition of children's language needs and affected interventions. Camouflaging reportedly impacted children's exhaustion, mental health, self-esteem, personality, friendships, and how others view them. Research characterizing camouflaging in DLD could help reduce the underdetection of children's language needs.

The interpretation of mu suppression as an index of mirror neuron activity: past, present and future.

Mu suppression studies have been widely used to infer the activity of the human mirror neuron system (MNS) in a number of processes, ranging from action understanding, language, empathy and the development of autism spectrum disorders (ASDs). Although mu suppression is enjoying a resurgence of interest, it has a long history. This review aimed to revisit mu's past, and examine its recent use to investigate MNS involvement in language, social processes and ASDs. Mu suppression studies have largely failed to produce robust evidence for the role of the MNS in these domains. Several key potential shortcomings with the use and interpretation of mu suppression, documented in the older literature and highlighted by more recent reports, are explored here.

Mu suppression - A good measure of the human mirror neuron system?

Mu suppression has been proposed as a signature of the activity of the human mirror neuron system (MNS). However the mu frequency band (8-13 Hz) overlaps with the alpha frequency band, which is sensitive to attentional fluctuation, and thus mu suppression could potentially be confounded by changes in attentional engagement. The specific baseline against which mu suppression is assessed may be crucial, yet there is little consistency in how this is defined. We examined mu suppression in 61 typical adults, the largest mu suppression study so far conducted. We compared different methods of baselining, and examined activity at central and occipital electrodes, to both biological (hands) and non-biological (kaleidoscope) moving stimuli, to investigate the involvement of attention and alpha activity in mu suppression. We also examined changes in beta power, another candidate index of MNS engagement. We observed strong mu suppression restricted to central electrodes when participants performed hand movements, demonstrating that mu is indeed responsive to the activity of the motor cortex. However, when we looked for a similar signature of mu suppression to passively observed stimuli, the baselining method proved to be crucial. Selective suppression for biological versus non-biological stimuli was seen at central electrodes only when we used a within-trial baseline based on a static stimulus: this method greatly reduced trial-by-trial variation in the suppression measure compared with baselines based on blank trials presented in separate blocks. Even in this optimal condition, 16-21% of participants showed no mu suppression. Changes in beta power also did not match our predicted pattern for MNS engagement, and did not seem to offer a better measure than mu. Our conclusions are in contrast to those of a recent meta-analysis, which concluded that mu suppression is a valid means to examine mirror neuron activity. We argue that mu suppression can be used to index the human MNS, but the effect is weak and unreliable and easily confounded with alpha suppression.