A5076389348- Visual perception and processing mechanisms
- Neural dynamics and brain function
- Neurobiology and Insect Physiology Research
- EEG and Brain-Computer Interfaces
- Color Science and Applications
- Retinal Development and Disorders
- Olfactory and Sensory Function Studies
- Visual Attention and Saliency Detection
- Biochemical Analysis and Sensing Techniques
- Neuroscience and Neuropharmacology Research
- Neural Networks and Applications
- Traumatic Brain Injury Research
- Neuroscience and Neural Engineering
- Aesthetic Perception and Analysis
- Photoreceptor and optogenetics research
- Advanced Vision and Imaging
- Blind Source Separation Techniques
- Gaze Tracking and Assistive Technology
- Functional Brain Connectivity Studies
- Advanced Fluorescence Microscopy Techniques
- Cardiac Arrest and Resuscitation
- Traumatic Brain Injury and Neurovascular Disturbances
- Color perception and design
- stochastic dynamics and bifurcation
- Industrial Vision Systems and Defect Detection
Cornell University
2016-2025
MIND Research Institute
2016-2025
JDSU (United States)
2025
Weill Cornell Medicine
2020-2025
Christian Medical College & Hospital
2025
Christian Medical College
2025
Athinoula A. Martinos Center for Biomedical Imaging
2024
Harvard University
2024
Spaulding Rehabilitation Hospital
2024
Massachusetts General Hospital
2024
1. We recorded single-unit and multi-unit activity in response to transient presentation of texture grating patterns at 25 sites within the parafoveal representation V1, V2, V3 two awake monkeys trained perform a fixation task. In experiments, stimuli varied orientation, spatial frequency, or both. contrast, check size, type, pairs these attributes. 2. To examine nature precision temporal coding, we compared individual responses elicited by each set terms families metrics. One family...
1. Variation in stimulus contrast produces a marked effect on the dynamics of cat retina. This was investigated by measurement responses X and Y ganglion cells. The stimuli were sine gratings or rectangular spots modulated temporal signal which sum sinusoids. Fourier analysis neural response to such allowed us calculate first order second frequency kernels. 2. kernel both cells became more sharply tuned at higher contrasts. peak amplitude also shifted Responses low frequencies modulation...
We present the mathematical basis of a new approach to analysis temporal coding. The foundation is construction several families novel distances (metrics) between neuronal impulse trains. In contrast most previous approaches coding, does not attempt embed trains in vector space, and assume Euclidean notion distance. Rather, proposed metrics formalize physiologically based hypotheses for those aspects firing pattern that might be stimulus dependent, make essential use point-process nature...
Patients with brain injury who are unresponsive to commands may perform cognitive tasks that detected on functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). This phenomenon, known as motor dissociation, has not been systematically studied in a large cohort of persons disorders consciousness.
Steady-state evoked potentials are often characterized by the amplitude and phase of Fourier component at one or more frequencies interest. We introduce a new statistic for evaluation these components. This statistic, denoted T2circ, is based on same physiologic assumptions concerning sources variability that made in use Rayleigh phase-coherence as well standard T2 (Hotelling 1931) multivariate data. However, T2circ also exploits relationship between real imaginary components estimates,...
In the primary visual cortex (V1), nearby neurons are tuned to similar stimulus features, and, depending on manner and time scale over which neuronal signals analyzed, resulting redundancy may mitigate deleterious effects of response variability. We estimated information rates in short–time responses clusters up six simultaneously recorded monkey V1. Responses were almost independent if we kept track neuron fired each spike but redundant summed cluster. Redundancy was cluster size. Summing...
To evaluate an integrated battery of preoperative functional magnetic resonance imaging (fMRI) tasks developed to identify cortical areas associated with tactile, motor, language, and visual functions.Sensitivity each task was determined by the probability that a targeted region activated for both healthy volunteers (n = 63) surgical patients lesions in these critical 125). Accuracy correspondence between fMRI maps intraoperative electrophysiological measurements, including somatosensory...
We present an approach to estimate information carried by experimentally observed neural spike trains elicited known stimuli. This makes use of embedding the into a set vector spaces, and entropy estimates based on nearest-neighbor Euclidean distances within these spaces [L. F. Kozachenko N. Leonenko, Probl. Peredachi Inf. 23, 9 (1987)]. Using numerical examples, we show that this can be dramatically more efficient than standard bin-based approaches such as ``direct'' method [S. P. Strong,...
We have used Sutter's (1987) spatiotemporal m-sequence method to map the receptive fields of neurons in visual system cat. The stimulus consisted a grid 16 x square regions, each which was modulated time by pseudorandom binary signal, known as an m-sequence. Several strategies for displaying are presented. results illustrated with two examples. For both geniculate and cortical simple cells, measurement first-order response properties provided detailed characterization classical...
1. The dynamics of the centre mechanism individual cat X retinal ganglion cells is investigated. visual stimuli consist temporal contrast modulation stationary patterns. In order to study response mechanism, patterns were either sine gratings high spatial frequency or small circular spots positioned over receptive‐field centre. 2. Responses reversal are approximately linear. However, as depth stimulus increases, responses become more transient. Ganglion cell show this phenomenon at moderate...
We report that neuronal spike trains can exhibit high, stimulus-dependent temporal precision even while the trial-to-trial response variability, measured in several traditional ways, remains substantially independent of stimulus. show retinal ganglion cells and neurons lateral geniculate nucleus (LGN) cats vivo display both these aspects firing behavior, which have previously been reported to be contradictory. develop a simple model treats as "leaky" integrate-and-fire devices it, too,...
How do neurons in the primary visual cortex (V1) encode contrast of a stimulus? In this paper, information that V1 responses convey about static stimuli is explicitly calculated. These often contain several easily distinguished temporal components, which will be called latency, transient, tonic, and off. Calculating conveyed each component groups components makes it possible to delineate aspects structure may relevant for encoding. The results indicate as much or more contrast-related...
The neural basis for perceptual grouping operations in the human visual system, including processes which generate illusory contours, is fundamental to understanding vision. We have employed functional magnetic resonance imaging investigate these noninvasively. Images were acquired on a GE Signa 1.5T scanner equipped echo planar with an in-plane resolution of 1.5 x mm and slice thicknesses 3.0 or 5.0 mm. Visual stimuli included nonaligned inducers (pacmen) that created no similar at corners...
1. A model is proposed for the effect of contrast on first‐order frequency responses cat retinal ganglion cells. The consists several cascaded low pass filters ('leaky integrators') followed by a single stage negative feed‐back. 2. Values time constants and gain components in this were chosen to approximate (with least‐squared deviation) experimentally measured responses. In experiments used analysis, visual stimulus was sine grating modulated sum sinusoids. 3. For both X cells Y cells,...
Retinal ganglion cells of the Y type in cat retina produce two different types response: linear and nonlinear. The nonlinear responses are generated by a separate independent pathway. functional connectivity this pathway is analyzed here comparing observed second-order frequency with predictions "sandwich model" which static stage sandwiched between filters. model agrees well qualitative quantitative features responses. prefilter may be bipolar nonlinearity postfilter probably associated...