Article Index

 

VISUAL

Early visual attention: a diagnostic measure for deficits after brain injuries

Ahmed Hisham Gardoh (Project 4)

Hemispatial neglect is a frequent disorder following stroke. Patients with hemispatial neglect fail to attend towards the sensory stimuli on the contralesional side of space. Importantly, the visual cortex in stroke patients with pure visual neglect is intact and the early visual processing is usually preserved. Strokes frequently damage the connection between the intact visual cortex and the higher level processing areas. Consequently, the sensory stimuli on one side of space fail to receive enough attention to exceed the threshold needed to reach awareness. We hypothesize that training voluntary control of attention using synchronous multisensory cues improves the functional outcome during rehabilitation of neglect patients. Information from multiple senses can circumvent the damaged routes so that the intact visual cortex can be functionally reengaged. Multisensory stimulation might induce enough attentional modulation of the activity in primary sensory cortex to reach awareness. The aim of my project is to test this hypothesis and perform some fundamental laboratory studies to investigate multisensory interactions and its interplay with the mechanisms of attentional control over perceptual selection. This provides a framework within which we are planning to devise multisensory stimulation-based rehabilitation tools to facilitate high-level sensory processing (e.g., attentional control) that can be used for hemispatial neglect patients in clinical settings.

Cognitive assessment and rehabilitation of visual-impaired patients

Leslie Guadron (Project 5)

Our study will employ computational modeling and behavioral studies to predict and examine the visuo-motor characteristics of visually impaired patients. It is believed that visual input plays an important role in determining an optimal saccade trajectory and generating the neural command that produces this movement. We aim to investigate the changes in saccade generation when visual information is lacking or incomplete, as is the case in patients with tunnel vision, foveal scotomas, or peripheral blind spots. We hope to determine precisely how visual input affects saccade planning and execution. What we learn can be applied for the early diagnosis of those at risk for vision loss and possibly for the improvement and/or assessment of retinal implants.

Visual rehabilitation after stroke

Anna Geuzebroek (Project 6)

Within the HealthPAC project, I am working on the rehabilitation of visual field defects after stroke. Our patients suffer from these visual field defects on a daily bases and until recently there is no effective rehabilitation offered. Visual restorative treatment is a new development within this field, where patients are training their visual field defect by repetitive visual stimulation. However, this treatment unfortunately is not able to help all patients. My project focuses on the development of new ways to improve this treatment and find new ways to help this patients.  In this light I am working on several projects. In the first project we use a saccadic target-selection task to assess the capabilities of the recovered visual field after the restorative treatment to compete with the healthy visual field.  We found that the patients show an abnormal behavior pattern in their 'unaffected' visual field. Hence, we further studied the saccadic parameters, specifically the reaction times, to find a possible explanation. Our results show that this abnormal behavior might indicated the adoption of a new decision-making strategy. In this new choice strategy, patients seem to trade off accuracy with the urgency to make a choice. In the second project I work on a new treatment in cooperation with Philips. Therefore, we are using a multimodal approach by combining visual stimulation with haptic stimulation to try to induce plasticity.

Top-down attention in health and disease

Andrea Bertana (Project 11)

Visual perceptual learning refers to a reliable improvement in performance on a visual perceptual task, due to experience with that task. Many studies have show how this type of learning is task and feature (orientation, motion direction, spatial frequency) specific. A recent study in our lab has also shown that perceptual learning can improve our ability to sample relevant portions of the stimuli, by increase our attentional window. In my current project I am interested to investigate the underlying neuronal properties linked to this type of learning. I am investigating that by using functional magnetic resonance imaging (fMRI) and focusing my attention on primary visual cortex. Data analysis involved standard and canonical fMRI analysis together with the use of ad­-hoc models in order to estimate attentional modulations.

 

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