Graphomotor memory in Exner\u2019s area enhances word learning in the blind

Tomomi Mizuochi-Endo,Kimihiro Nakamura,Kazuhisa Ikeda,Michiru Makuuchi,Kazuyuki Itou,Baku Kato

doi:10.1038/s42003-021-01971-z

Tomomi Mizuochi-Endo, Kimihiro Nakamura + Show 4 more

Open Access

https://doi.org/10.1038/s42003-021-01971-z

Copy DOI

Abstract

Handwriting is thought to impede vocabulary learning in sighted adults because the motor execution of writing interferes with efficient audiovisual processing during encoding. However, the motor memory of writing may facilitate adult word learning when visual sensory inputs are severely restricted. Using functional MRI, we show that late-blind participants, but not sighted participants, learned novel words by recruiting the left dorsal premotor cortex known as Exner’s writing area and its functional coupling with the left hippocampus. During later recall, the phonological and semantic contents of these words are represented in the activation patterns of the left hippocampus as well as in those of left frontotemporal language areas. These findings suggest that motor codes of handwriting help blind participants maintain word-form representations during learning and retrieval. We propose that such reliance on the motor system reflects a broad architecture of the cerebral language network which encompasses the limb motor system as a hardwired component.

Highlights

Handwriting is thought to impede vocabulary learning in sighted adults because the motor execution of writing interferes with efficient audiovisual processing during encoding
Such reliance on the motor system may reflect specific compensatory change in the dyslexic brain and a more universal and intrinsic architecture of the human language network, because the same left PMd is shown to mediate novel word learning in normal adults via motor memory[24] and play a role in sign language processing[25,26]
While the crossmodal interaction between the visual and phonological systems is thought to play a primary role in adult word learning[27,28], such learning mechanism enhanced by literacy should be compromised by the long-term deprivation of visual inputs in the late-blind, which can attenuate visual memory retrieval[29,30] but may allow more cognitive resources for exploiting motor codes during word learning

Summary

Introduction

Handwriting is thought to impede vocabulary learning in sighted adults because the motor execution of writing interferes with efficient audiovisual processing during encoding. Neuroimaging data with dyslexic children suggest that reading difficulties are partially compensated by relying on Exner’s area[22] or a left dorsal premotor region (PMd) known to represent the motor memory for handwriting[23] Such reliance on the motor system may reflect specific compensatory change in the dyslexic brain and a more universal and intrinsic architecture of the human language network, because the same left PMd is shown to mediate novel word learning in normal adults via motor memory[24] and play a role in sign language processing[25,26]. We performed representational similarity analysis (RSA, see Fig. 1B)[31] to identify the representational content of those brain regions that emerged during the test period

Methods

Results

Conclusion