scholarly journals Validation of population receptive field estimates in human visual cortex

2019 ◽  
Author(s):  
D. Samuel Schwarzkopf ◽  
Christina Moutsiana ◽  
Gurmukh Panesar
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Brain Activity ◽  
Visual Space ◽  
Parameter Estimates ◽  
Back Projection ◽  
Position Preference ◽  
Mapping Data ◽  
Human Visual Cortex ◽  
Retinotopic Mapping

Population receptive field (pRF) analysis has become a popular method for non-invasively inferring the spatial tuning properties of the human visual system and for reconstructing brain activity in visual space. Yet few studies have sought to validate pRF parameter estimates or systematically compared them between different methods. Here we used pRF models to reconstruct the visual cortex response to pseudo-randomly placed ‘constellation’ stimuli. We present different methods for visualizing brain activity in visual space. Compared to typically used back-projection of pRF profiles, we show that a searchlight approach using only pRF location greatly improves the spatial precision of reconstructions. We further quantify the precision with which different pRF estimates distinguish between stimulated and unstimulated parts of the visual field. Both combined wedge-and-ring and more conventional sweeping-bar stimuli afford excellent localization of the presented test stimuli. Even a probabilistic pRF model based on cortical anatomy without any retinotopic mapping data performs well albeit with lower precision than empirical data. Our findings demonstrate that pRF analysis is an accurate and robust method for mapping the position preference of voxels in human visual cortex.

scholarly journals Orientation and color tuning of the human visual gamma rhythm

2021 ◽  
Author(s):  
Ye Li ◽  
William Bosking ◽  
Michael S Beauchamp ◽  
Sameer A Sheth ◽  
Daniel Yoshor ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Large Scale ◽  
Brain Activity ◽  
Population Level ◽  
Gamma Oscillations ◽  
Cell Orientation ◽  
Population Activity ◽  
Color Tuning ◽  
Human Visual Cortex ◽  
Gamma Rhythm

Narrowband gamma oscillations (NBG: ~20-60Hz) in visual cortex reflect rhythmic fluctuations in population activity generated by underlying circuits tuned for stimulus location, orientation, and color. Consequently, the amplitude and frequency of induced NBG activity is highly sensitive to these stimulus features. For example, in the non-human primate, NBG displays biases in orientation and color tuning at the population level. Such biases may relate to recent reports describing the large-scale organization of single-cell orientation and color tuning in visual cortex, thus providing a potential bridge between measurements made at different scales. Similar biases in NBG population tuning have been predicted to exist in the human visual cortex, but this has yet to be fully examined. Using intracranial recordings from human visual cortex, we investigated the tuning of NBG to orientation and color, both independently and in conjunction. NBG was shown to display a cardinal orientation bias (horizontal) and also an end- and mid-spectral color bias (red/blue and green). When jointly probed, the cardinal bias for orientation was attenuated and an end-spectral preference for red and blue predominated. These data both elaborate on the close, yet complex, link between the population dynamics driving NBG oscillations and known feature selectivity biases in visual cortex, adding to a growing set of stimulus dependencies associated with the genesis of NBG. Together, these two factors may provide a fruitful testing ground for examining multi-scale models of brain activity, and impose new constraints on the functional significance of the visual gamma rhythm.

scholarly journals The Effect of High-Level Illumination on Brain Activity in the Human Visual Cortex

2014 ◽  
Vol 98 (2) ◽  
pp. 87-91
Author(s):  
Yasuhiro Kawashima ◽  
Hiroyuki Yamashiro ◽  
Hiroki Yamamoto ◽  
Tomokazu Murase ◽  
Yoshikatsu Ichimura ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Brain Activity ◽  
Human Visual Cortex ◽  
High Level

Early effects of semantic meaning on electrical brain activity

1999 ◽  
Vol 22 (2) ◽  
pp. 301-302 ◽  
Author(s):  
Wolfgang Skrandies
Keyword(s):  
Visual Cortex ◽  
Brain Activity ◽  
Stimulus Presentation ◽  
Semantic Meaning ◽  
Human Visual Cortex ◽  
Neuronal Assemblies ◽  
Electrical Brain Activity ◽  
Early Effects

When words are read, the visual cortex is activated, independent of whether visual or motor associations are elicited. This word-evoked brain activity is significantly influenced by semantic meaning. Such effects occur very early after stimulus presentation (at latencies between 80 and 130 msec), indicating that semantic meaning activates different neuronal assemblies in the human visual cortex when words are processed.

Receptive field expansion in adult visual cortex is linked to dynamic changes in strength of cortical connections

1995 ◽  
Vol 74 (2) ◽  
pp. 779-792 ◽  
Author(s):  
A. Das ◽  
C. D. Gilbert
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Primary Visual Cortex ◽  
Visual Space ◽  
Final Analysis ◽  
Before And After ◽  
On Line ◽  
Adult Cats ◽  
Visual Cortex Neurons ◽  
Cortical Connection

1. Receptive field (RF) sizes of neurons in adult primary visual cortex are dynamic, expanding and contracting in response to alternate stimulation outside and within the RF over periods ranging from seconds to minutes. The substrate for this dynamic expansion was shown to lie in cortex, as opposed to subcortical parts of the visual pathway. The present study was designed to examine changes in cortical connection strengths that could underlie this observed plasticity by measuring the changes in cross-correlation histograms between pairs of primary visual cortex neurons that are induced to dynamically change their RF sizes. 2. Visually driven neural activity was recorded from single units in the superficial layers of primary visual cortex in adult cats, with two independent electrodes separated by 0.1–5 mm at their tips, and cross-correlated on-line. The neurons were then conditioned by stimulation with an “artificial scotoma,” a field of flashing random dots filling the region of visual space around a blank rectangle enclosing the RFs of the recorded neurons. The neuronal RFs were tested for expansion and their visually driven output again cross-correlated. After this, the neurons were stimulated vigorously through their RF centers to induce the field to collapse, and the visually driven output from the collapsed RFs was again cross-correlated. Cross-correlograms obtained before and after conditioning, and after RF collapse, were normalized by their flanks to control for changes in peak size due solely to fluctuations in spike rate. 3. A total of 37 pairs of neurons that showed distinct cross-correlogram peaks, and whose RF borders were clearly discernible both before and after conditioning, were used in the final analysis. Of these neuron pairs, conditioning led to a clear expansion of RF boundaries in 28 pairs, whereas in 9 pairs the RFs did not expand. RFs that did expand showed no significant shifts in their orientation preference, orientation selectivity, or ocularity. 4. When the RFs of a pair of neurons expanded with conditioning, the area of the associated flank-normalized cross-correlogram peaks also increased (by a factor ranging from 0.84 up to 3.5). Correlograms returned to their preconditioning values when RFs collapsed.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Retinotopic mapping of adult human visual cortex with high-density diffuse optical tomography

2007 ◽  
Vol 104 (29) ◽  
pp. 12169-12174 ◽  
Author(s):  
B. W. Zeff ◽  
B. R. White ◽  
H. Dehghani ◽  
B. L. Schlaggar ◽  
J. P. Culver
Keyword(s):  
Visual Cortex ◽  
Optical Tomography ◽  
Diffuse Optical Tomography ◽  
High Density ◽  
Human Visual Cortex ◽  
Retinotopic Mapping ◽  
Adult Human
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