Using visual feedback to modulate motor performance and its neural correlates

Abstract

Visual feedback is important for perceiving, planning and executing goal directed movements in humans. Visual feedback may influence motor performance via guiding motor control and learning or via other brain mechanisms relating visual information to motor output. However, the interactions between feedback and motor performance are currently poorly understood on both the behavioural and brain activation levels. An understanding of these interactions would have a wide range of applications, e.g. in training for human motor performance enhancement and rehabilitation. This thesis presents four studies investigating different aspects of feedback – performance interactions: motor control and learning induced by visual feedback scaling, influences of visual hand representations on behaviour, and brain activation, and application of visual feedback scaling for motor function training. To study these processes, virtual reality augmented tasks were used, incorporating movement sensors to animate virtual hands in real-time. Multi-modal neuroimaging techniques (fMRI, fNIRS) were used to record brain activations, as well as camerabased systems to measure eye movements. Amplification of visual movement feedback has been used to modulate task performance in human motor function training. However, knowledge about the underlying brain processes is currently missing and would be needed if such paradigms are to be used to systematically modulate human motor performance. Study One of this thesis investigated the behavioural and neural correlates of adjustments to increasing and decreasing visual feedback amplitudes. The results revealed brain processes associated with motor control and motor learning. These processes were identified by analysing relationships between brain activation and behaviour in response to adjustments to increased and decreased visual feedback amplitudes. Study Two investigated how knowledge of the brain areas involved in visual feedback scaling can be applied in a system using light-weight portable neuroimaging sensors to assess brain activations during motor function training in real-time. In addition to manipulations via feedback scaling, human motor performance may also be modulated by intrinsic features of visual feedback. Studies Three and Four investigated how different hand feedback can affect motor performance and related brain activations during visually-guided finger movements. Study Three found that the presence of an image of the human hand in feedback was associated with faster reaction times of the executed movements. Study Four revealed the brain regions that mediated these feedback – performance interactions. In combination these results showed that visual images of the hand in feedback can affect motor performance and related brain activations. In summary, this thesis shows how human motor performance can be modulated via visual feedback. The experiments found distinct behavioural and neural correlates for adjustments to visual feedback scaling, the first ever report of performance and brain activation effects related to the characteristics of visual hand feedback, and strategies to modulate motor performance via visual feedback in practice. The new understanding of visual feedback effects on motor performance elucidated in these studies may find applications in new paradigms for human motor training and rehabilitation.