Fine motor control in using pen for writing and copying, in the impaired and healthy brain

The central issue of the dissertation is to investigate the neural-cognitive basis of writing and copying figures focusing on fine motor abilities. The neuronal recycling hypothesis is used as the theoretical framework, assuming that the ability to use pen emerged from other closely related cognitive abilities. The thesis contained four independent studies with either ischemic stroke patients or healthy participants. Chapter 2 describe the general methods used in our study. Chapter 3 is a neuropsychological study that utilizes principle component analysis and voxel-based morphometry. It explores the neural-cognitive basis underlying complex figure copying (CFC). It demonstrates the involvement of different processing stages that supports figure copying along the dorsal pathway, from visual through eye-hand coordination to the motor associative cortex. Chapters 4-6 focus on writing abilities, across two different systems: phonological and logographic. Chapter 4, is a neuropsychological study that utilized machine learning to explore the latent relationship between writing with other cognitive tasks in English and Chinese. Across the two-writing systems impairment in writing skills could be reliably classified using the same features. These cognitive features were related to CFC, attention, reading, memory and age. Chapter 5 presents two neuropsychological studies that examine the neuro-cognitive makeup of the ability to write words (phonological) and numbers (logographic). The first study is a detail comorbidity analysis of writing deficits of words, numbers, language and motor deficits. It demonstrates that pure writing deficits are very rare, with the majority of writing deficits overlapping with motor (CFC) or language impairments. The second study in this chapter is a VBM study focus on writing numbers and words. We identified two dissociable networks that have been specifically evolved to support writing: a visual-manual motor ability to use pen mediated by right angular and middle frontal gyri; and an ability to transform symbolic representations grapheme to manual programs for use with the pen. Chapter 6 is an fMRI study with healthy participants investigating the neural substrates associated with writing English, Chinese and Pinyin. The study identifies different brain networks that support writing abilities across writing systems: visual information perception and visual motor transformation, semantic component. Chapter 7, summarize and compare the main finding of the four studies. Overall, the studies demonstrate the close relations between the sue of pen and other more basic cognitive functions, such as control of hand movement, language, attention. As predicted by the neuronal recycling hypothesis there were minimal pure deficits of writing or copying; and for proficient writers, the same neural structures supported different writing systems.