Unravelling neurodevelopmental complexity of motor profiles and attention in developmental coordination disorder

This commentary is on the original article by Bonthrone et al. on pages 362–378 of this issue.

Developmental coordination disorder subtypes in children: An unsupervised clustering

AIM

To identify subtypes of developmental coordination disorder (DCD) in children.

METHOD

Children with DCD diagnosed through comprehensive evaluation at Robert-Debré Children's University Hospital (Paris, France) were consecutively enrolled from February 2017 to March 2020. We performed an unsupervised hierarchical clustering based on principal component analysis using a large set of variables encompassing cognitive, motor, and visuospatial scores (Wechsler Intelligence Scale for Children, Fifth Edition; Developmental Neuropsychological Assessment, Second Edition; Movement Assessment Battery for Children, Second Edition).

RESULTS

One hundred and sixty-four children with DCD were enrolled (median age 10 years 3 months; male:female ratio 5.56:1). We identified distinct subgroups with mixed visuospatial and gestural disorders, or with pure gestural disorders that predominantly impaired either speed or precision. Associated neurodevelopmental disorders, such as attention-deficit/hyperactivity disorder, did not influence the results of the clustering. Importantly, we identified a subgroup of children with marked visuospatial impairment with the lowest scores in almost all of the evaluated domains, and the poorest school performance.

INTERPRETATION

The classification of DCD into distinct subgroups could be indicative of prognosis and provide critical information to guide patient management, taking into account the child's neuropsychological profile. Beyond this clinical interest, our findings also provide a relevant framework with homogeneous subgroups of patients for research on the pathogenesis of DCD.

WHAT THIS PAPER ADDS

Unsupervised hierarchical clustering identified four subgroups of children with developmental coordination disorder. Two subgroups had combined visuospatial/gestural difficulties, and two had pure gestural disorders. Severe visuospatial impairment was associated with poor performance in most domains including school. Difficulties in the gestural-only clusters were predominantly either gestural precision or speed.

Subitizing and counting impairments in children with developmental coordination disorder

Developmental coordination disorder (DCD) interferes with academic achievement and daily life, and is associated with persistent academic difficulties, in particular within mathematical learning. In the present study, we aimed to study numerical cognition using an approach that taps very basic numerical processes such as subitizing and counting abilities in DCD. We used a counting task and a subitizing task in forty 7-10 years-old children with or without DCD. In both tasks, children were presented with arrays of one to eight dots and asked to name aloud the number of dots as accurately and quickly as possible. In the subitizing task, dots were presented during 250 ms whereas in the counting task they stayed on the screen until the participants gave a verbal response. The results showed that children with DCD were less accurate and slower in the two enumeration tasks (with and without a time limit), providing evidence that DCD impairs both counting and subitizing. These impairments might have a deleterious impact on the ability to improve the acuity of the Approximate Number System through counting, and thus could play a role in the underachievement of children with DCD in mathematics.

[Developmental coordination disorder]

Developmental coordination disorder. The diagnosis of dyspraxia or developmental coordination disorder is based on motor coordination skills significantly below the expected level for the age of the child, assessed by a validated and standardized motor skills scale. This deficit must have an impact on activities of daily life, leisure and academic achievement. It should not be secondary to a neurological condition. It is a common disorder with a prevalence around 5%. The diagnosis is based on questioning of the family and the child, a clinical examination and an evaluation with standardized tools of motor skills and writing. It requires the intervention of a doctor, if possible trained in neurodevelopmental disorders, and of an occupational therapist. Interventions should focus on activities that are essential to the child's daily and school life.

Numerical abilities of school-age children with Developmental Coordination Disorder (DCD): A behavioral and eye-tracking study

Developmental Coordination Disorder (DCD) is a disorder of motor coordination which interferes with academic achievement. Difficulties in mathematics have been reported. Performance in the number line task is very sensitive to atypical development of numerical cognition. We used a position-to-number task in which twenty 7-to-10years old children with DCD and 20 age-matched typically developing (TD) children had to estimate the number that corresponded to a hatch mark placed on a 0-100 number line. Eye movements were recorded. Children with DCD were less accurate and slower to respond than their peers. However, they were able to map numbers onto space linearly and used anchoring strategies as control. We suggest that the shift to a linear trend reflects the ability of DCD children to use efficient strategies to solve the task despite a possibly more imprecise underlying numerical acuity.

Mathematical difficulties in developmental coordination disorder: Symbolic and nonsymbolic number processing

At school, children with Developmental Coordination Disorder (DCD) struggle with mathematics. However, little attention has been paid to their numerical cognition abilities. The goal of this study was to better understand the cognitive basis for mathematical difficulties in children with DCD. Twenty 7-to-10 years-old children with DCD were compared to twenty age-matched typically developing children using dot and digit comparison tasks to assess symbolic and nonsymbolic number processing and in a task of single digits additions. Results showed that children with DCD had lower performance in nonsymbolic and symbolic number comparison tasks than typically developing children. They were also slower to solve simple addition problems. Moreover, correlational analyses showed that children with DCD who experienced greater impairments in the nonsymbolic task also performed more poorly in the symbolic tasks. These findings suggest that DCD impairs both nonsymbolic and symbolic number processing. A systematic assessment of numerical cognition in children with DCD could provide a more comprehensive picture of their deficits and help in proposing specific remediation.

Face recognition in schizophrenia: do individual and average ROCs tell the same story?

INTRODUCTION

Many studies have shown that recollection process is impaired in patients with schizophrenia, whereas familiarity is generally spared. However, in these studies, the Receiver Operating Characteristic (ROC) presented is average ROC likely to mask individual differences.

METHODS

In the present study using a face-recognition task, we computed the individual ROC of patients with schizophrenia and control participants. Each group was divided into two subgroups on the basis of the type of recognition processes implemented: recognition based on familiarity only and recognition based on familiarity and recollection.

RESULTS

The recognition performance of the schizophrenia patients was below that of the control participants only when recognition was based solely on familiarity. For the familiarity-alone patients, the score obtained on the Scale for the Assessment of Positive Symptoms (SAPS) was correlated with the variance of the old-face familiarity. For the familiarity-recollection patients, the score obtained on the Scale for the Assessment of Negative Symptoms (SANS) was correlated with the decision criterion and with the old-face recollection probability.

CONCLUSIONS

These results show that one cannot ascribe the impaired recognition observed in patients with schizophrenia to a recollection deficit alone. These results show that individual ROC can be used to distinguish between subtypes of schizophrenia and could serve as a basis for setting up specific cognitive remediation therapy for individuals with schizophrenia.

Chronic persecutory delusion and autobiographical memories in patients with schizophrenia: a diary study

BACKGROUND

While chronic persecutory delusions are typically anchored into patients' everyday life situations, no investigation has ever looked at how situations associated with a feeling of persecution are recorded and later retrieved.

METHOD

a diary methodology combined with a recognition task involving ten patients with schizophrenia who presented chronic persecutory delusions and ten control participants. Diaries of everyday persecutory events (Pe) and non-persecutory events (nPe) were kept.

RESULTS

in both groups, 1) Pe were associated with higher anxiety scores than nPe, 2) Pe were experienced as less distinctive and more stereotyped than nPe, 3) the frequency of incorrect recognition of altered descriptions of Pe was higher than that of nPe.

LIMITATIONS

because high levels of motivation are required of the diarists, our sample size was small.

CONCLUSION

Memories of persecutory events were highly emotional and semanticized. they were frequently incorrectly recognized, suggesting the existence of bias resulting from interactions between their processing and persecutory delusions.

Impairment not only in remembering but also in knowing previously seen faces and words in schizophrenia

Patients with schizophrenia have pronounced deficits in face recognition memory that severely hamper their social skills. The functional mechanisms of these impairments remain unknown. According to the dual-process theory, recognition memory comprises two distinct components: recollection and familiarity. Studies using the Remember/Know procedure in patients with schizophrenia showed impairments in conscious recollection as measured by remember responses, but not in familiarity as measured by know responses. Unfortunately, none of these studies used face material. We investigated both recognition memory components using words and faces and the 'Remember/Know' procedure in 25 patients with schizophrenia and 24 control participants. In the same task, size congruency of stimuli was manipulated between the study and test phases to have a selective impact on know responses for faces. Patients reported fewer remember responses than controls. Size changes between the study and the test affected know responses in controls but not in patients. These results reveal that patients with schizophrenia are impaired in terms of their ability to recollect details about previously seen faces as they are for words.

Episodic memory and impairment of an early encoding process in schizophrenia

Investigations of memory impairment in schizophrenia have frequently revealed a strategic processing deficit at encoding. The authors studied an early encoding process, refreshing (in this case, thinking of a stimulus that has just-previously been presented), and its impact on recognition memory in schizophrenia. Following simultaneous presentation of three words or a single word in the top, middle, or bottom position of the screen, 25 patients with schizophrenia and 25 control participants saw and read a new word (read condition), or a word presented on the previous screen (repeat condition), or saw a dot indicating that they should think of and say the last word to have appeared in that position (refresh condition). Later, on a surprise test, participants were asked to recognize words seen previously and give a Remember, Know, or Guess response according to whether they recognized each on the basis of conscious recollection, familiarity, or guessing. The cognitive operation of refreshing was impaired in schizophrenia: patients were slower on 1-word trials and less accurate on 3-word trials to refresh a word, and their Remember responses did not benefit from refreshing.

Comparing effects of perceptual and reflective repetition on subjective experience during later recognition memory

Using the Remember/Know procedure, we compared the impact of a reflective repetition by refreshing (i.e., briefly thinking of a just-seen item) and a perceptual repetition (i.e., seeing an item again) on subjective experience during recognition memory. Participants read aloud words as they appeared on a screen. Critical words were presented once (read condition), immediately repeated (repeat condition), or followed by a dot signalling the participants to think of and say the just-previous word (refresh condition). In Experiments 1 and 2, Remember responses benefited from refreshing a word (in comparison with reading it). In Experiment 2, this benefit disappeared when participants had to refresh one of three active items. Perceptual repetition increased Remember responses in Experiment 1, but not in Experiment 2 regardless of whether participants had just previously seen 1- or 3-items. These findings indicate that under some circumstances, reflective and perceptual repetition may have different consequences for later subjective experience during remembering, suggesting differences in their underlying functional mechanisms.

Functional mechanisms of episodic memory impairment in schizophrenia

OBJECTIVE

To achieve a better understanding of the functional mechanisms underlying episodic memory dysfunction in schizophrenia, which is a prerequisite for unravelling schizophrenia's neural correlates in neuroimaging studies and, more generally, for developing an integrated approach to the pathophysiology of schizophrenia. It is also crucial for developing cognitive remediation.

METHOD

This paper reviews empirical evidence of episodic memory dysfunction in schizophrenia obtained with reference to various theoretical models of episodic memory.

RESULTS

All the studies converge to show a significant impairment of the critical feature of episodic memory: conscious recollection. Schizophrenia is also associated with a defect of autobiographical memory. The episodic memory dysfunction results from a predominant failure of strategic processing at encoding, although an impairment of strategic processing at retrieval cannot be ruled out. The possibility that it is not the execution of the encoding strategies that is defective but, rather, their self-initiation by the patients is plausible.

CONCLUSIONS

These findings may explain some behavioural abnormalities associated with schizophrenia, notably, inadequate functional outcomes in everyday life. They may also have implications for cognitive remediation and better social and work functioning of patients with schizophrenia.

Directed forgetting in PTSD: a comparative study versus normal controls

The most characteristic feature of Post-Traumatic Stress Disorder (PTSD) is the reexperiencing syndrome. The patient's memory seems to be fixed on the traumatic event, which may be due to disturbance of the autobiographic memory. To retrieve memories, others have to be inhibited. These inhibition mechanisms have been studied using the Directed Forgetting Paradigm, which measures the capacity to forget recently processed information and to retain the relevant information. Our hypothesis is that during PTSD, the memory is saturated with traumatic memories, so that the patients are no longer able to use the inhibitory processes. Therefore, during a Directed Forgetting Task (DFT) in which words "to remember" and words "to forget" are given, PTSD patients cannot inhibit the words "to forget", and so recall more words than the controls. We studied 30 patients with PTSD and compared them with 30 healthy controls, using DFT. The results show that the patients remembered significantly fewer words overall, and fewer of the words "to remember" than the controls, both for immediate and final recall. Our results are in favor of a reduction in directed forgetting in patients suffering from PTSD, resulting in difficulty in inhibiting irrelevant information from the overall information. There seems to be a deficit in the inhibitory processes in the memory in PTSD.

Les phobies sociales en psychiatrie : caractéristiques cliniques et modalités de prise en charge (étude Phœnix)

Only few clinical epidemiologic studies have been conducted on social phobia in France to date. It is however a frequent disorder, with often severe alteration of social adaptation and quality of life, and for which effective treatments exist. Thus, it seems really important to further explore how these patients are nowadays identified and treated in psychiatry. It was the objective of the Phoenix study. In this observational multi-center study, 952 psychiatric in- or out-patients, with a primary diagnosis of social phobia according to DSM IV criteria, were included. Numerous diagnostic and psychometric evaluations were carried out, in order to evaluate the comorbidity (Mini International Neuropsychiatric Interview, Hospital Anxiety and Depression Scale), the intensity of social anxiety (Liebowitz Social Anxiety Scale), and various aspects of the functional and emotional impact (Various Impact of Social Anxiety scale, Sheehan Disability Scale, SF-36, Positive and Negative Emotionality scale). The patients were in majority females (57.6%), with a mean age 37.5 years, and with a mean duration of social anxiety disorder 12.5 years. The mean scores of social anxiety on Liebowitz scale was 40.3 +/- 12.6 for the fear factor, and 38.3 +/- 13.6 for the avoidance factor. The generalized social anxiety subtype (anxiety in most social situations) was present in 67.8% of the patients. A major depressive disorder was found in 47.7% of the sample, and the prevalence of agoraphobia was even higher (49.2%). As known in clinical practice and in other studies, the prevalence rates of current alcohol dependence and substances abuse were also important in this population (respectively 10.6% and 12.7%). Mean scores of the Hospital Anxiety and Depression (HAD) sub-scales were 13.9 +/-3.8 for anxiety and 9.1 +/-4.5 for depression. About 15% of the patients had a history of suicide attempt, and a suicidal risk was present in nearly 40% of the sample. The psychosocial impact and the alteration of quality of life (with especially a poor physical health perception) were very significant, in the family, educational or occupational and social domains. Mean scores of the Sheehan Disability Scale were 6.1 +/- 2.6 for professional impairment, 5.0 +/- 2.7 for familial impairment, and 6.6 +/- 2.3 for social life impairment. In addition to the disability due to social phobia intensity, an important part of the burden was due to depressive symptoms. Approximately 60% of the patients had already a psychiatric treatment at the time of the survey (since 1,7 years in average), but only 17% had a cognitive behavioral therapy (CBT), and 48% had an antidepressant treatment. These proportions increased in a significant way after the consultation during which the investigation was carried out: an antidepressant was prescribed to 72% of the patients, and a CBT is proposed to 48%. On the whole, this study confirmed the severity and the morbidity of social phobia in a very large sample of French psychiatric patients. The depressive disorders, suicidal risk, and social impairment associated with this condition should incite to more detect and treat it. Seeing the long duration of the disease in our sample, and the lack of specific therapies in many cases, the identification and the treatment of social phobia must be improved, and the role of the psychiatrists in this process seems very important.

Assessing a minimal executive operation in schizophrenia

The minimal cognitive operation of thinking of a just-seen stimulus (refreshing) was studied in 24 patients with schizophrenia and 24 normal controls. Verbal response times were measured when participants read a word, read a word immediately again, or refreshed a word just after it was no longer present. Patients showed equal priming as controls in reading a word for the second time and were slower than controls to say a word only in the refresh condition. On a surprise test, participants were asked to recognize the words they had seen previously and to give Remember, Know, or Guess responses according to whether they recognized words on the basis of conscious recollection, familiarity, or guessing. Although patients showed overall poorer recognition memory, the beneficial effect of refreshing on long-term memory accuracy and Remember responses was preserved, whereas they derived less benefit in familiarity from seeing an item twice than from refreshing it. These results suggest that although patients may have some difficulty engaging the refresh process, they show significant long-term memory benefits when induced to do so.

Conscious recollection in autobiographical memory: an investigation in schizophrenia

Whether or not conscious recollection in autobiographical memory is affected in schizophrenia is unknown. The aim of this study was to address this issue using an experiential approach. An autobiographical memory enquiry was used in combination with the Remember/Know procedure. Twenty-two patients with schizophrenia and 22 normal subjects were asked to recall specific autobiographical memories from four lifetime periods and to indicate the subjective states of awareness associated with the recall of what happened, when and where. They gave Remember, Know or Guess responses according to whether they recalled these aspects of the event on the basis of conscious recollection, simply knowing, or guessing. Results showed that the frequency and consistency of Remember responses was significantly lower in patients than in comparison subjects. In contrast, the frequency of Know responses was not significantly different, whereas the frequency of patients' Guess responses was significantly enhanced. It is concluded that the frequency and consistency of conscious recollection in autobiographical memory is reduced in patients with schizophrenia.

Do patients with schizophrenia consciously recollect emotional events better than neutral events?

OBJECTIVE

The influence of the emotional valence of words on conscious awareness was assessed in patients with schizophrenia.

METHOD

The remember/know procedure was used to test 24 patients with schizophrenia and 24 normal comparison subjects.

RESULTS

Patients' "remember" responses and conscious recollection were more frequent for emotional words than for neutral words. In contrast, the levels of "know" responses and familiarity were independent of emotional words.

CONCLUSIONS

Patients with schizophrenia consciously recollected emotional words better than neutral words.

Impaired strategic regulation of contents of conscious awareness in schizophrenia

Conscious awareness comprises two distinct states, autonoetic and noetic awareness. Schizophrenia impairs autonoetic, but not noetic, awareness. We investigated the strategic regulation of relevant and irrelevant contents of conscious awareness in schizophrenia using a directed forgetting paradigm. Twenty-one patients with schizophrenia and 21 normal controls were presented with words and told to learn some of them and forget others. In a subsequent test, they were asked to recognize all the words they had seen previously and give remember, know or guess responses according to whether they recognized words on the basis of autonoetic awareness, noetic awareness, or guessing. Overall, patients showed the same degree of a directed forgetting effect as normal subjects. However, whereas the effect was observed both for remember and know responses in normal subjects, it was observed for know, but not for remember, responses in patients. These results indicate that patients with schizophrenia exhibit an impaired strategic regulation of contents of autonetic awareness for relevant and irrelevant information.

Subjective qualities of memories associated with the picture superiority effect in schizophrenia

Patients with schizophrenia (n = 24) matched with 24 normal subjects were presented with both words and pictures. On a recognition memory task, they were asked to give remember, know, or guess responses to items that were recognized on the basis of conscious recollection, familiarity, or guessing, respectively. Compared with normal subjects, patients exhibited a lower picture superiority effect selectively related to remember responses. Unlike normal subjects, they did not exhibit any word superiority effect in relation to guess responses; this explains why the overall picture superiority effect appeared to be intact. These results emphasize the need to take into account the subjective states of awareness when analyzing memory impairments in schizophrenia.

Impairment of constructive memory in schizophrenia

Episodic memories are characterized by a specific state of awareness, conscious recollection, which allows subjects to mentally relive past events. They are not a literal reproduction of the past but instead depend on constructive processes. Patients with schizophrenia exhibit a specific impairment of conscious recollection. The aim of this study was to investigate the role of constructive processes into defective conscious recollection of patients with schizophrenia. An experiential approach to false recognition and related states of awareness was used. Thirty patients with schizophrenia, who were matched with 30 normal subjects, studied lists of words semantically related to a non-presented theme word (critical lure). On a recognition memory task with both previously presented words and non presented critical lures, they were asked to give Remember, Know or Guess responses to items that were recognized on the basis of conscious recollection, familiarity or guessing, respectively. Patients with schizophrenia recognized fewer studied words and critical lures than normal subjects. This deficit was restricted to memories associated with conscious recollection as indicated by a decrease in Remember responses, but not Know and Guess responses. Our results indicate that patients with schizophrenia exhibit an impaired conscious recollection, whether memories are true or false. They provide evidence that schizophrenia impairs the mere construction of conscious recollection.

Lorazepam, sedation, and conscious recollection: a dose-response study with healthy volunteers

The role of sedation in the benzodiazepine-induced impairment of conscious recollection is still subject to debate. The aim of this study was to investigate further the role of sedation using the Remember-Know procedure and a physiological measure of sedation based on pupillography in addition to standard measures of sedation and attention (digit-symbol substitution task, symbol cancellation task, self-rated sedation). Twelve subjects were tested after the intake of placebo, lorazepam 0.026 mg/kg and lorazepam 0.038 mg/kg, administered in a randomized order, with a minimum interval of 8 days between each administration. On a recognition memory task, they were asked to give 'Remember', 'Know' or 'Guess' responses to items that were recognized on the basis of conscious recollection, familiarity, or guessing, respectively. Lorazepam selectively impaired recognition based on 'Remember' responses. This impairment was greater in the lorazepam 0.038 mg/kg than in the lorazepam 0.026 mg/kg groups. Measures of sedation were not correlated with the proportion of 'Remember' responses. These results suggest that sedation alone cannot account for the impairment of conscious recollection induced by lorazepam.

Lorazepam and diazepam impair true, but not false, recognition in healthy volunteers

RATIONALE

The deleterious effects of benzodiazepine on memory are well documented. However, their effects on false memories are unknown.

OBJECTIVE

The aim of this study was to investigate the effects of lorazepam and diazepam on false memories and related states of awareness in healthy volunteers.

METHODS

The Deese/Roediger-McDermott procedure was used in 36 healthy volunteers randomly assigned to one of three parallel groups (placebo, diazepam 0.3 mg/kg, lorazepam 0.038 mg/kg). Subjects studied lists of words semantically related to a non-presented theme word (critical lure). On a recognition memory task with both previously presented words and non presented critical lures, they were asked to give Remember, Know or Guess responses to items that were recognized on the basis of conscious recollection, familiarity, or guessing, respectively.

RESULTS

The proportions of studied words correctly recognized and the proportions of Remember responses associated with true recognition were lower in the benzodiazepine groups than in the placebo group. In contrast, benzodiazepines did not significantly influence the proportions of critical lures falsely recognized or the proportions of Remember responses associated with false recognition.

CONCLUSION

These results indicate that diazepam and lorazepam impair conscious recollection associated with true, but not false, memories.

Impairment of recognition memory with, but not without, conscious recollection in schizophrenia

OBJECTIVE

To test the hypothesis that there is a link between the memory deficit associated with schizophrenia and an impairment of consciousness, an experiential approach was used to assess recognition memory and awareness in schizophrenic patients and normal subjects.

METHOD

On a recognition memory task with low- and high-frequency words, the schizophrenic (N = 30) and normal (N = 30) subjects gave "remember" responses to recognized items that were accompanied by conscious recollection and "know" responses to items that were recognized on the basis of familiarity without any recollective experience.

RESULTS

Schizophrenia selectively impaired recognition based on recollective experience, as measured by "remember" responses, but had no effects on "know" responses. In the comparison group, low-frequency words, relative to high-frequency words, enhanced conscious recollection but not familiarity. The schizophrenic patients did not display the same word-frequency effect.

CONCLUSIONS

These results indicate that schizophrenia affects differentially two means of access to the personal past: it impairs recognition memory with, but not without, conscious recollection. They suggest that the impairment of conscious recollection observed in schizophrenic patients could be due to a failure of elaborative processing of information.