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The adult brain constantly adapts to changes in stimuli, and this plasticity is manifest not only as learning and memory but also as dynamic changes in information transmission and processing. Using interactively multimodal imaging (fMRI, MEG) and psychophysics, the Neurology of Vision Laboratory's (NOVI) goal is to understand the mechanisms mediating visual perception in healthy and damaged human brains, and long-term plasticity and short-term dynamics in networks of the adult normal and stroke-damaged cortex.
Our research is translational, conducted hand in hand with several neurologists, physiatrists, and other clinicians. We are developing psychophysical tests for the diagnosis of cognitive and higher visual function deficits, and use fMRI, MEG and behavioral tasks to develop a physiological marker for prognosis of recovery of such deficits in stroke patients, and for determining programs of targeted rehabilitation of such deficits.

Research Projects

Dynamic Granger Causality Applied to Perception of a Complex Visual Motion Search Task

Perception and perceptual decisions arise from the spatiotemporal orchestration of activity distributed across brain networks. In an MEG study, we used dynamic Granger Causality and corresponding summary network measures to understand the critical cortical interactions involved in solving a complex visual-motion search task (VS).

Cortical dynamics of perception and decision in sensory tasks: An MEG study

Perception and perceptual decisions arise from the spatiotemporal orchestration of activity distributed across brain networks. Functional MRI (fMRI) studies have shown that discrete networks mediate the sensory processing and the representation of visual search task (VSS2011 C&V). However, fMRI does not have the temporal precision required for revealing the neuronal mechanisms that integrate sensory information and coordinate the decision-making process during perceptual tasks. View poster

Deficit of temporal dynamics of detection of a moving object during egomotion in a stroke patient: An MEG study

Using anatomically constrained MEG in conjunction with Granger causality in the time domain (DGC)1 and PLV in the frequency domain and  bands) we compared in a patient and 6 healthy controls the direction and dynamics of connectivity between the functional areas involved in detection of a moving object by a moving observer in two experimental conditions: visual only (unimodal) and cross-modal, visual augmented by an auditory cue co-localized and congruent to the moving object. Our previous psychophysical study of these tasks demonstrated that in healthy observers, this specific auditory cue significantly enhanced task performance. View poster

Detection of object motion during self-motion: Psychophysics and neuronal substrate

During self-motion, the separation of the motion flow field into self- and  object-motion components is critical to safe navigation. “Flow-parsing”, a visual-only implementation, has been proposed based on the subtraction of induced selfmotion from the perceived flow field1,2. Is object detection during forward observer translation consistent with the low-parsing hypothesis? What brain networks mediate the detection of object motion by a moving observer? View poster

Direction of motion in depth: dissociation of perception 114 of self-motion and object motion

Accurately estimating direction of self-motion through the environment (heading) and detecting possibility of collision with a moving object (collision detection) are fundamental tasks of visually guided navigation. Do heading estimation and collision with a moving object share the same motion mechanisms? Is performance on collision detection affected differently by a static or moving observer? Why? What do fMRI studies tell us about the neural substrate of the collision detection task (static observer)? View poster

Functional Stealing: Reorganization of the Retinotopic Map After Occipital Lobe Infarction

While neuroplasticity after stroke has been amply demonstrated using functional magnetic resonance imaging (fMRI) in the motor (1-4) and language (5) systems, there is a dearth of human studies examining neuroplasticity in the cortical visual system. This is in stark contrast with the extensive knowledge of visual mechanisms and their neural substrate in non-human primates and humans. View poster

Research Positions

Medical Student Research Project Opportunities

The signature of brain networks after ischemic stroke in humans

In order to understand pathological states after stroke, the projects involves using fMRI data, both from rest states and from quantitative computerized psychophysical tasks, to determine changes in functional brain networks in patients compared with healthy subjects. Students will learn fMRI data analysis (Free Surfer), and models of brain connectivity analysis and graph theory concepts that are used to quantitatively characterize the human connectome at the behavioral level. The projects may be done as a mini-project, in a few months, or as a full projects over a few years.

The project can be split into 3-4 related subprojects to be carried out by multiple students. All projects are carried out at Mass General Neurology Department and the Martinos Center for Biomedical Imaging, under the supervision of Drs. Vaina and Buonanno.

Prerequisites (desired but not obligatory): Matlab, fluent in basic statistics and signal processing, good with computers, good knowledge of human brain anatomy. But most important, energy and enthusiasm!

Professional Research Opportunities

All applicants should register with the Mass General Careers website.


View Dr. Vaina’s Publications on PubMed

View Dr. Buonanno’s Publications on PubMed