Dynamics of absolute and relative disparity processing in human visual cortex

Cortical processing of binocular disparity is believed to begin in V1 where cells are sensitive to absolute disparity, followed by the extraction of relative disparity in higher visual areas. While much is known about the cortical distribution and spatial tuning of disparity-selective neurons, the relationship between their spatial and temporal properties is less well understood. Here, we use steady-state Visual Evoked Potentials and dynamic random dot stereograms to characterize the temporal dynamics of spatial mechanisms in human visual cortex that are primarily sensitive to either absolute or relative disparity. Stereograms alternated between disparate and non-disparate states at 2 Hz. By varying the spatial frequency content of the disparate fields from a planar surface to corrugated ones, we biased responses towards absolute vs. relative disparities. Reliable Components Analysis was used to derive two dominant sources from the 128 channel EEG records. The first component (RC1) was maximal over the occipital pole while the second component (RC2) was maximal over right lateral occipital electrodes. In RC1, first harmonic responses were sustained, tuned for corrugation frequency, and sensitive to the presence of disparity references, consistent with prior psychophysical sensitivity measurements. By contrast, the second harmonic, associated with transient processing, was not spatially tuned and was indifferent to references, consistent with it being generated by an absolute disparity mechanism. In RC2, the sustained response component showed similar tuning and sensitivity to references. However, sensitivity for absolute disparity dropped off, and transient signals were mainly driven by the lowest corrugation frequencies.

Download Full-text

Eccentricity Mapping of the Human Visual Cortex to Evaluate Temporal Dynamics of Functional T1ρ Mapping

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2015.94 ◽

2015 ◽

Vol 35 (7) ◽

pp. 1213-1219 ◽

Cited By ~ 10

Author(s):

Hye-Young Heo ◽

John A Wemmie ◽

Casey P Johnson ◽

Daniel R Thedens ◽

Vincent A Magnotta

Keyword(s):

Blood Flow ◽

Visual Cortex ◽

Temporal Dynamics ◽

Occipital Cortex ◽

Hemodynamic Response ◽

Proton Exchange ◽

Blood Oxygenation ◽

Human Visual Cortex ◽

Tissue Metabolism ◽

Oxygenation Level

Recent experiments suggest that T1 relaxation in the rotating frame ( T1ρ) is sensitive to metabolism and can detect localized activity-dependent changes in the human visual cortex. Current functional magnetic resonance imaging (fMRI) methods have poor temporal resolution due to delays in the hemodynamic response resulting from neurovascular coupling. Because T1ρ is sensitive to factors that can be derived from tissue metabolism, such as pH and glucose concentration via proton exchange, we hypothesized that activity-evoked T1ρ changes in visual cortex may occur before the hemodynamic response measured by blood oxygenation level-dependent (BOLD) and arterial spin labeling (ASL) contrast. To test this hypothesis, functional imaging was performed using BOLD, and ASL in human participants viewing an expanding ring stimulus. We calculated eccentricity phase maps across the occipital cortex for each functional signal and compared the temporal dynamics of T1ρ versus BOLD and ASL. The results suggest that T1ρ changes precede changes in the two blood flow-dependent measures. These observations indicate that T1ρ detects a signal distinct from traditional fMRI contrast methods. In addition, these findings support previous evidence that T1ρ is sensitive to factors other than blood flow, volume, or oxygenation. Furthermore, they suggest that tissue metabolism may be driving activity-evoked T1ρ changes.

Download Full-text

Dynamics of the cerebral blood flow response to brief neural activity in human visual cortex

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x19869034 ◽

2019 ◽

Vol 40 (9) ◽

pp. 1823-1837 ◽

Cited By ~ 1

Author(s):

Jung Hwan Kim ◽

Amanda J Taylor ◽

Danny JJ Wang ◽

Xiaowei Zou ◽

David Ress

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Visual Cortex ◽

Temporal Dynamics ◽

Oxygen Metabolism ◽

Late Time ◽

Neural Activation ◽

Hemodynamic Response Function ◽

Time Dynamics ◽

Human Visual Cortex

The blood oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signal depends on an interplay of cerebral blood flow (CBF), oxygen metabolism, and cerebral blood volume. Despite wide usage of BOLD fMRI, it is not clear how these physiological components create the BOLD signal. Here, baseline CBF and its dynamics evoked by a brief stimulus (2 s) in human visual cortex were measured at 3T. We found a stereotypical CBF response: immediate increase, rising to a peak a few second after the stimulus, followed by a significant undershoot. The BOLD hemodynamic response function (HRF) was also measured in the same session. Strong correlations between HRF and CBF peak responses indicate that the flow responses evoked by neural activation in nearby gray matter drive the early HRF. Remarkably, peak CBF and HRF were also strongly modulated by baseline perfusion. The CBF undershoot was reliable and significantly correlated with the HRF undershoot. However, late-time dynamics of the HRF and CBF suggest that oxygen metabolism can also contribute to the HRF undershoot. Combined measurement of the CBF and HRF for brief neural activation is a useful tool to understand the temporal dynamics of neurovascular and neurometabolic coupling.

Download Full-text

Temporal Dynamics of Corticocortical Inhibition in Human Visual Cortex: A TMS Study

Neuroscience ◽

10.1016/j.neuroscience.2019.10.003 ◽

2019 ◽

Vol 421 ◽

pp. 31-38

Author(s):

Dalia Khammash ◽

Molly Simmonite ◽

Thad A. Polk ◽

Stephan F. Taylor ◽

Sean K. Meehan

Keyword(s):

Visual Cortex ◽

Temporal Dynamics ◽

Human Visual Cortex

Download Full-text

THE RELATIONSHIP BETWEEN STIMULUS PARAMETERS AND PHOSPHENE THRESHOLD/BRIGHTNESS, DURING STIMULATION OF HUMAN VISUAL CORTEX

ASAIO Journal ◽

10.1097/00002480-197902500-00070 ◽

1979 ◽

Vol 25 (1) ◽

pp. 367-371 ◽

Cited By ~ 9

Author(s):

D. C. Henderson ◽

J. R. Evans ◽

W. H. Dobelle

Keyword(s):

Visual Cortex ◽

Human Visual Cortex ◽

Stimulus Parameters ◽

Phosphene Threshold ◽

The Relationship ◽

Stimulation Of

Download Full-text

The Relationship between Cortical Magnification Factor and Population Receptive Field Size in Human Visual Cortex: Constancies in Cortical Architecture

Journal of Neuroscience ◽

10.1523/jneurosci.2572-11.2011 ◽

2011 ◽

Vol 31 (38) ◽

pp. 13604-13612 ◽

Cited By ~ 138

Author(s):

B. M. Harvey ◽

S. O. Dumoulin

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Field Size ◽

Magnification Factor ◽

Receptive Field Size ◽

Human Visual Cortex ◽

Cortical Magnification ◽

Cortical Magnification Factor ◽

The Relationship ◽

Cortical Architecture

Download Full-text

The temporal dynamics of implicit processing of non-letter, letter, and word-forms in the human visual cortex

Frontiers in Human Neuroscience ◽

10.3389/neuro.09.056.2009 ◽

2009 ◽

Vol 3 ◽

Cited By ~ 21

Author(s):

Lawrence Appelbaum

Keyword(s):

Visual Cortex ◽

Temporal Dynamics ◽

Implicit Processing ◽

Human Visual Cortex ◽

Word Forms

Download Full-text

Unifying Temporal Phenomena in Human Visual Cortex

10.1101/108639 ◽

2017 ◽

Cited By ~ 1

Author(s):

Jingyang Zhou ◽

Noah C. Benson ◽

Kendrick Kay ◽

Jonathan Winawer

Keyword(s):

Visual Cortex ◽

Receptive Field ◽

Temporal Dynamics ◽

Gain Control ◽

Spatial Vision ◽

Research Area ◽

Neuronal Responses ◽

Stimulus Contrast ◽

Temporal Properties ◽

Cortical Responses

AbstractNeuronal responses in visual cortex show a diversity of complex temporal properties. These properties include sub-additive temporal summation, response reduction with repeated or sustained stimuli (adaptation), and slower dynamics at low stimulus contrast. Here, we hypothesize that these seemingly disparate effects can be explained by a single, shared computational mechanism. We propose a model consisting of a linear stage, followed by history-dependent gain control. The model accounts for these various temporal phenomena, tested against an unusually diverse set of measurements - intracranial electrodes in patients, fMRI, and macaque single unit spiking. The model further enables us to uncover a systematic and rich variety of temporal encoding strategies across visual cortex: First, temporal receptive field shape differs both across and within visual field maps. Second, later visual areas show more rapid and pronounced adaptation. Our study provides a new framework to understand the transformation between visual input and dynamical cortical responses.Author SummaryThe nervous system extracts meaning from the distribution of light over space and time. Spatial vision has been a highly successful research area, and the spatial receptive field has served as a fundamental and unifying concept that spans perception, computation, and physiology. While there has also been a large interest in temporal vision, the temporal domain has lagged the spatial domain in terms of quantitative models of how signals are transformed across the visual hierarchy. Here we present a model of temporal dynamics of neuronal responses in human cerebral cortex. We show that the model can accurately predict responses at the millisecond scale using intracortical electrodes in patient volunteers, and that the same model generalizes to multiple types of other measurements, including functional MRI and action potentials from monkey cortex. Further, we show that a single model can account for a variety of temporal phenomena, including short-term adaptation and slower dynamics at low stimulus contrast. By developing a computational model and showing that it successfully generalizes across measurement types, cortical areas, and stimuli, we provide new insights into how time-varying images are encoded and transformed into dynamic cortical responses.

Download Full-text

Temporal Properties of Disparity Processing Revealed by Dynamic Random-Dot Stereograms

Perception ◽

10.1068/p5404 ◽

2005 ◽

Vol 34 (10) ◽

pp. 1205-1219 ◽

Cited By ~ 6

Author(s):

Elena Gheorghiu ◽

Casper J Erkelens

Keyword(s):

Depth Perception ◽

Temporal Integration ◽

Temporal Properties ◽

Different Types ◽

Temporal Flexibility ◽

Random Dot Stereograms ◽

Integration Mechanisms ◽

Stereoscopic System ◽

Random Dot Patterns ◽

The Relationship

In studies of the temporal flexibility of the stereoscopic system, it has been suggested that two different processes of binocular depth perception could be responsible for the flexibility: tolerance for interocular delays and temporal integration of correlation. None has investigated the relationship between tolerance for delays and temporal integration mechanisms and none has revealed which mechanism is responsible for depth perception in dynamic random-dot stereograms. We address these questions in the present study. Across five experiments, we investigated the temporal properties of stereopsis by varying interocular correlation as a function of time in controlled ways. We presented different types of dynamic random-dot stereograms, each consisting of two pairs of alternating random-dot patterns. Our experimental results demonstrate that (i) disparities from simultaneous monocular inputs dominate those from interocular delayed inputs; (ii) stereopsis is limited by temporal properties of monocular luminance mechanisms; and (iii) depth perception in dynamic random-dot stereograms results from cross-correlation-like operation on two simultaneous monocular inputs that represent the retinal images after having been subjected to a process of monocular temporal integration of luminance.

Download Full-text