Research Projects

Neuroplasticity and Compensatory Behaviors Associated with Ocular Blindness

 

Image of brain and gears. GenericIt is generally believed that individuals who are blind develop compensatory behavioral strategies through the use of their remaining senses. Studies have shown that some blind individuals possess superior sensory abilities compared to their sighted peers (e.g. localizing sounds, discriminating tactile patterns, identifying smells, and verbal memory recall). Scientific evidence suggests that the development of these adaptive behaviors is intimately related to dramatic structural and functional changes occurring within the brain; termed “neuroplasticity”. Given that the brain is highly specialized and that different regions of the brain are responsible for the processing of different sensory modalities, this begs the question: what is the fate of regions of the brain normally associated with the processing of visual information in an individual who is blind? To help answer this question, we conduct behavioral sensory testing employing a variety of specially designed stimulus presentation devices combined with advanced structural and functional brain imaging (magnetic resonance imaging, or MRI). This allows us to uncover the contribution of different regions of the brain to non-visual forms of sensory processing and how the brain “re-wires” itself in response to blindness.

 

 

Neuroplasticity Associated With Cortical/Cerebral Visual Impairment

 

Cartoon of man constructing a brainIn developed countries including the United States, cortical/cerebral visual impairment (CVI) is the leading cause of permanent visual impairment in children, and is characterized by visual dysfunction primarily associated with damage to central brain structures as opposed to the eyes. Despite this significant public health concern, the neurophysiology of this condition remains poorly understood, and more research is needed to fully understand how the developing brain reorganizes itself in response to early damage. The goal of this investigation is to establish a conceptual framework relating sensory function with structural and functional brain reorganization in CVI. In this effort, we use high resolution structural reconstruction and characterization of the white matter pathways of the brain using diffusion based imaging (specifically, High Angular Resolution Imaging, or HARDI). We employ behavioral assessments integrating virtual reality (VR), psychometric sequences, and eye/gesture tracking technology. These novel techniques allow us to characterize visual dysfunctions beyond what is done in the standard clinical settings using scenarios that more closely approximate real world situations.

Rotating 3D view of standard structural magnetic resonance imaging (MRI; grey matter rendering), then whole brain High Angular Resolution  Diffusion Imaging (HARDI) showing white matter connections, and then virtual dissection revealing visual pathways originating from the occipital pole  (dorsal and ventral visual processing streams). Images are taken from an age matched control subject with neurotypical visual development (left) and an  individual with cerebral/cortical visual impairment (CVI) associated with periventricular leukomalacia (PVL) (right). 
This video demonstrates all the options for the Visual Perception Testing: Object Crowding experiment to conducted at the Laboratory for Visual Neuroplasticity at Massachusettes Eye and Ear Infirmary/Harvard Medical School Department of Opthalmology. It shows the virtual reality environment designed to test the effect of object crowding. The task is to locate the presence of a target toy hidden amongst other toys. Eye and hand movements are recorded using tracking devices. The stimulus was created using Unity. ©2017 Laboratory for Visual Neuroplasticity.
This video demonstrates all the options for the Visual Perception Testing: Human Crowding experiment to be conducted at the Laboratory for Visual Neuroplasticity at Massachusettes Eye and Ear Infirmary/Harvard Medical School Department of Opthalmology. The virtual reality environment designed to test the effect of human crowding. The task is to locate the presence of a target individual walking in a crowded hallway. Eye movements are recorded using an eye tracker. The stimulus was created using Unity. ©2017 Laboratory for Visual Neuroplasticity.

 

 

Spatial Cognition Related to Navigation and Video Game Based Learning in the Blind

 

For a blind individual, learning to navigate independently and safely is a very important skill to master. Considerable interest has arisen in developing virtual reality and computer based video games as a means to motivate and improve contextual learning. In this direction, we have developed a user-centered, computer-based navigation software designed with the purpose of developing navigation skills in the blind through immersive virtual navigation. The software is called Audio-based Environmental Simulator (AbES). Using auditory spectral cues, a user navigates through a simulated virtual environment based on the spatial layout of a building for which they are previously unfamiliar. Following exploration during game play, the user is able to transfer the knowledge gained regarding the spatial layout and navigate their way in the physical building modeled in the software. Associated studies using functional MRI (fMRI) and wireless electro-encephalography (EEG) allow us to study how the brain navigates in the absence of sight.

  • Blind participant using the Audio-based Environment Simulator (AbES) while an investigator watches on.

    Blind participant using the Audio-based Environment Simulator (AbES) while an investigator watches on.

  • Individual laying in an MRI  scanner playing the AbES game

    Individual laying in an MRI scanner playing the AbES game

  • Brain activation in a blind individual revealed by  functional MRI (fMRI) in response to playing the AbES game

    Brain activation in a blind individual revealed by functional MRI (fMRI) in response to playing the AbES game

    Note the activation of numerous brain areas including areas normally associated with the processing of visual information. CITE

  • Example of subject using mobile wireless electroencephalogram (EEG) allows recording of brain signals during navigation.

    Example of subject using mobile wireless electroencephalogram (EEG) that allows recording of brain signals during navigation.

  • EEG analysis revealing scalp activation patterns associated with navigation.

    EEG analysis revealing scalp activation patterns associated with navigation.

Video of game play using AbES. A blind participant is able to navigate through the building (based on the floor plan of an existing building) using only sounds presented in the game. Following game play, the participant is able to navigate in the real building represented in the game.  ©2012 Laboratory for Visual Neuroplasticity. For more information, see Merabet et al, 2012.