What drives bias?: an investigation into the anatomy of extra-oculomotor proprioception and its role in spatial neglect

Abstract

Spatial attention is used to selectively navigate to objects within our environment that are salient or deemed important. Successful allocation of attention in space requires a combination of positional, visual and spatial information and extra-retinal signals are a key component in integrating visual information with perceived body position in space (Dijkerman et al., 2006; Donaldson, 2000; Guthrie, Porter, & Sparks, 1983; Roll & Roll, 1987; von Holst, 1954). In particular, extra-ocular motor (EOM) proprioception has been linked to the allocation of attention in space (Balslev, Newman, & Knox, 2012; Odoj & Balslev, 2016). In this thesis, I investigate the mechanism of EOM proprioception and how changes to this mechanism might cause biases to spatial attention. In particular, a population of patients who present with an extreme right-ward bias to attention; spatial neglect. This thesis describes five studies (one in Part I, four in Part II) that assess EOM proprioception and spatial attention. The experiment in Part I (chapter 2) used functional neuroimaging to map a subcortical pathway for EOM proprioception. Here, we found that the superior colliculus is a likely candidate for the processing of oculosensory information. Part II investigates biases to spatial attention, chapters 5-7 assess the possibility that maladaptive proprioception contributes to spatial neglect by changing the attention priority map. This was achieved by directly investigating the pattern of spatial attention in patients with spatial neglect (experiment 2), and using treatment for spatial neglect to assess sensorimotor and attention changes in healthy individuals. Finally, chapter 8 assessed the reliability of a spatial bias in the general population, pseudoneglect (Bowers & Heilman, 1980). The results of these experiments showed that EOM proprioception is a likely contributor to biases in spatial attention, as well as highlighting the possibility that there are many different contributions to spatial attention, and changes to either of these mechanisms can influence the allocation of attention in space.