A5039167346- Visual perception and processing mechanisms
- Neural dynamics and brain function
- Ophthalmology and Visual Impairment Studies
- Functional Brain Connectivity Studies
- Advanced Vision and Imaging
- Spatial Neglect and Hemispheric Dysfunction
- Neural and Behavioral Psychology Studies
- Motor Control and Adaptation
- Vestibular and auditory disorders
- Face Recognition and Perception
- EEG and Brain-Computer Interfaces
- Multisensory perception and integration
- Action Observation and Synchronization
- Neurobiology and Insect Physiology Research
- Tactile and Sensory Interactions
- Retinal Development and Disorders
- Neural Networks and Applications
- Medical Image Segmentation Techniques
- Stroke Rehabilitation and Recovery
- Retinal Imaging and Analysis
- Glaucoma and retinal disorders
- Advanced Neuroimaging Techniques and Applications
- Digital Image Processing Techniques
- Advanced MRI Techniques and Applications
- Multi-Criteria Decision Making
Athinoula A. Martinos Center for Biomedical Imaging
2009-2022
Boston University
2013-2022
Harvard University
2012-2022
Massachusetts Institute of Technology
1984-2022
Institute of Cognitive and Brain Sciences
2022
Massachusetts General Hospital
2011-2021
Brigham and Women's Hospital
1994-2021
Kingston University
2013
Brain (Germany)
2011
RELX Group (United Kingdom)
2004
We used whole brain functional MRI to investigate the neural network specifically engaged in recognition of “biological motion” defined by point-lights attached major joints and head a human walker. To examine specificity regions responsive biological motion, activations obtained during “walker vs. non-walker” discrimination task were compared with those elicited two other tasks: ( i ) non-rigid motion (NRM), involving overall direction same “point-lights” display, ii face-gender...
Abstract Although magnetoencephalography (MEG) and electroencephalography (EEG) have been available for decades, their relative merits are still debated. We examined regional differences in signal‐to‐noise‐ratios (SNRs) of cortical sources MEG EEG. Data from four subjects were used to simulate focal extended located on the surface reconstructed high‐resolution magnetic resonance images. The SNR maps EEG found be complementary. deep was larger than MEG, whereas opposite typically case...
The problems posed by the representation and recognition of movements 3-D shapes are analysed. A is proposed for that lie within scope Marr & Nishihara (1978) model static shapes. basic problem how to segment a stream movement into pieces, each which can be described separately. here based upon segmenting at moments when component axis, e. g. an arm, starts move relative its local coordinate frame (here torso). For example, walking divided stationary states between swing arms legs,...
Unlike first order motion, which is based on spatiotemporal variations in luminance, second-order motion relies variation of attributes derived from such as contrast. Here we show that a patient with small unilateral cortical lesion adjacent to human area MT (V5) has an apparently permanent disorder perceiving several forms but not first-order his contralateral visual field. This result indicates separate pathways for perception exist, either divergent or even primary cortex, subcortical...
We demonstrate performance-related changes in cortical and cerebellar activity. The largest learning-dependent were observed the anterior lateral cerebellum, where extent intensity of activation correlated inversely with psychophysical performance. After learning had occurred (a few minutes), almost disappeared; however, it was restored when subjects presented a novel, untrained direction motion for which performance also reverted to chance level. Similar reductions brain activations...
We used a psychophysical summation technique to study the properties of detectors tuned radial, circular and translational motion, determine spatial extent their receptive fields. Signal-to-noise motion thresholds were measured for patterns curtailed spatially in various ways. Sensitivity increased with stimulus area at rate predicted by an ideal integrator. When sectors noise added stimulus, sensitivity decreased consistent Summation was tested large annular stimuli, shown hold up 70° some...
Anatomical and physiological investigations indicate two major distinct functional streams within the extrastriate visual cortex of macaque monkey, behavioral observations suggest that ventral (occipitotemporal) pathway is cornerstone for object recognition whereas dorsal (occipitoparietal) primarily involved in visuospatial perception visuomotor performance. In context this dichotomy we conducted a psychophysical neuropsychological study perceptual abilities stroke patients, each with...
The perception of biological motion combines the analysis form and motion. However, patient observations by Vaina et al. psychophysical experiments Beintema Lappe showed that humans could perceive human movements (a walker) without local image information. Here, we examine specificity brain regions responsive to a stimulus motion, using functional magnetic resonance imaging. We used from compared activity with point-light display does contain information was often in previous studies. Recent...
This study sought to evaluate the long-term effect of transcatheter patent foramen ovale (PFO) closure on migraineurs with and without aura examine residual right-to-left shunt.
First-order (Fourier) motion consists of stable spatiotemporal luminance variations. Second-order (non-Fourier) instead modulation contrast, flicker, or spatial frequency. In spite extensive psychophysical and computational analysis the nature relationship these two types motion, it remains unclear whether they are detected by same mechanism separate mechanisms involved. Here we report selective impairment first-order on a range local global tasks, in contralateral visual hemifield patient...
Abstract Amyloid positron emission tomography (PET) imaging is a valuable tool for research and diagnosis in Alzheimer’s disease (AD). Partial volume effects caused by the limited spatial resolution of PET scanners degrades quantitative accuracy image. In this study, we have applied method to evaluate impact joint-entropy based partial correction (PVC) technique on brain networks learned from clinical dataset AV-45 image compare network properties both uncorrected corrected image-based...
We used a psychophysical task to measure sensitivity motion direction in 50 stroke patients with unilateral brain lesions and 85 control subjects. Subjects were asked discriminate the overall of dynamic stochastic random dot displays which only variable proportion spots moved single while remainder randomly. Behavioural neurophysiological evidence shows that middle temporal (MT/V5) superior (MST) areas macaque monkey are indispensably involved perception this type motion. In human subjects...
An unresolved issue in visual motion perception is how distinct are the processes underlying "first-order" and "second-order" motion. The former defined by spatiotemporal variations of luminance latter other image attributes, such as contrast or depth. Here we describe two neurological patients with focal unilateral lesions whose contrasting perceptual deficits on psychophysical tasks related to maps human brain established functional neuroimaging gross anatomical features. We used a...
“Biological motion” may be defined by the pattern of movement a small number lights attached to major joints human performing simple actions. Normal observers watching such displays immediately recognize person and his or her In present study, we investigated effects lesions anterior cortical regions on perception biological motion. We measured performance psychophysical static motion tasks object action recognition tests in four stroke patients who presented with disorder relate our results...
The effects of practice on the discrimination direction motion in briefly presented noisy dynamic random dot patterns are investigated several forced-choice psychophysical tasks. We found that percentage correct responses any specific task increases linearly with repetition trials within roughly 200 from about chance to a performance 90% or better. level remained constant improved over days, and most instances it did not transfer when stimulus parameters changed. used modified Radial Basis...
Random dot kinematograms were used to simulate radial, rotational and spiral optic flow. The stimuli designed so that, while speed increased linearly with distance from the centre of display, density dots remained uniform throughout their presentation. In two experiments, subjects required perform a temporal 2AFC discrimination task. Experiment 1 measured perceived range flow patterns against comparison stimulus. Radial motions found appear faster than rotations by approximately 10%, smaller...
For an intelligent entity to carry out tasks in the real world, perceived three-dimensional shapes are transformed into objects identified by their functional category which makes explicit roles or uses of actions. This study describes approach recognition functions that combines ideas about representations shapes, concepts, and object categories, with goal requirements A particular conceptual model compatibility between actions is introduced, outline solution given, experimental domain hand...