# Discrete movements in ASD children: comparison between the isochrony principle and Fitts' law

Aurélie Benchekri, Laetitia Fradet, Romain Tisserand, Éric Lemonnier, Anouck Amestoy, Christel Bidet-Ildei

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Aurélie Benchekri, Laetitia Fradet, Romain Tisserand, Éric Lemonnier, Anouck Amestoy, et al. Discrete movements in ASD children: comparison between the isochrony principle and Fitts' law. 22nd Conference of the European Society for Cognitive Psychology (ESCOP 2022), Aug 2022, Lille, France. hal-04122363

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Submitted on 8 Jun 2023

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# Discrete movements in ASD children: comparison between the isochrony principle and Fitts' law

Aurélie Benchekri 1, 2, Laetitia Fradet 2, Romain Tisserand 1, 2, Éric Lemonnier 3, Anouck Amestoy 4, Christel Bidet-Ildei 1

1: CERCA, Equipe Interactions, Université de Poitiers, Université de Tours, Centre National de la Recherche Scientifique: UMR 7295

2: Institut PPRIME, Equipe RoBioSS, Université de Poitiers, Centre National de la Recherche Scientifique: UPR 3346

3: Centre Ressource Autisme, Hôpital Le Cluzeau, Centre Hospitalier Universitaire Limoges

4: INCIA, Equipe Neuroimagerie et cognition humaine, Université de Bordeaux, Centre National de la Recherche Scientifique: UMR 5287

## Introduction

- **Autism Spectrum Disorder (ASD)** is a neurodevelopmental psychiatric condition characterized by 1) difficulties with social interactions and communication and 2) repeated and stereotypical movements or restricted interests.

- ASD children also display **altered motor control** (Kanner, 1943) which remains poorly understood.

- Altered motor control was observed in ASD animal models and related to **cerebellum disorders** (Jaber, 2017).

- The cerebellum is involved in the control of both morphocinetic (evaluated by the **Isochrony task**; Habas et al., 2020) and topocinetic movements (evaluated by the **Fitts' task**; Boyd et al., 2009).

### Isochrony task

Power relation between time and stimulus size : $MT=TO * A^γ$
$TO$ = baseline time; $0 < γ$ = isochrony coefficient < 1

Around 6 years old: $γ ≈ 0,4$ (Bidet-Ildei & Orliaguet, 2008)

### Fitts' task

Linear relation between time and ID : $MT= b \log_2(2A/W) + a$
$b$ = slope, $1/b$ reflects **motor capacities (MC)** (Bourgeois & Hay, 2003)

=> Can cerebellar deficits impact the motor control of discrete movements in ASD children ?

## Method

<figure><img src="image_1.png" /></figure>

<figure><img src="image_2.png" /></figure>

For each task : tablet recording movement duration (MT) and metric coordinates.

<figure><img src="image_3.png" /></figure>

### Isochrony task

5 "e" letters of 5 different sizes in cursive mode

<figure><img src="image_4.png" /></figure>

Variables extracted

$γ$ = slope
$TO$ = intercept

<figure><img src="image_5.png" /></figure>

Children (6-12 years)
17 ASD & 25 TD

<figure><img src="image_6.png" /></figure>

### Fitts' task

4*(1 target of 2 sizes : Small - Big + at 2 locations: Near - Far)

<figure><img src="image_7.png" /></figure>

Variables extracted
$b$ = slope
$1/b$

<figure><img src="image_8.png" /></figure>

Children (6-12 years)
18 ASD & 25 TD

## Results

<figure><img src="image_9.png" /></figure>

<figure><img src="image_10.png" /></figure>

<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /></figure>

## Discussion / Conclusion

- In ASD children : **topocinetic** motions appear affected but not morphocinetic ones.

- Topocinetic motions are relatively dependent on **sensory inputs used**.

- Further research is necessary to understand whether suspected cerebellum deficits may contribute to **sensory processing disorders** diagnosed in ASD.

<figure><img src="image_13.png" /></figure>

## References

- Bidet-Ildei C, Orliaguet JP. Developmental study of visual perception of handwriting movement: influence of motor competencies? Neurosci Lett. 2008 Jul 25;440(1):76-80.

- Bourgeois F, Hay L. Information processing and movement optimization during development: kinematics of cyclical pointing in 5- to 11-year-old children. J Mot Behav. 2003 Jun;35(2):183-95.

- Boyd LA, Vidoni ED, Siengsukon CF, Wessel BD. Manipulating time-to-plan alters patterns of brain activation during the Fitts' task. Exp Brain Res. 2009 Apr;194(4):527-39.

- Habas C, Berthoz A, Flash T, Bennequin D. Does the Cerebellum Implement or Select Geometries? A Speculative Note. Cerebellum. 2020 Apr;19(2):336-342.

- Jaber, M. (2017). Le cervelet comme acteur majeur dans les troubles moteurs des syndromes autistiques. *L'Encéphale, 43*(2), 170-175.

- Kanner, L. (1943). Autistic disturbances of affective contact. *Nervous child*, **2**(3), 217-250.

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