scholarly journals Effects of checkerboard pattern stimulation on evoked cortical responses in relation to check size and visual field

1970 ◽  
Vol 21 (2) ◽  
pp. 113-115 ◽  
Author(s):  
Robert G. Eason ◽  
Carroll T. White ◽  
Neil Bartlett
Keyword(s):  
Visual Field ◽  
Checkerboard Pattern ◽  
Check Size ◽  
Cortical Responses ◽  
Pattern Stimulation

Early visual cortical responses produced by checkerboard pattern stimulation

NeuroImage ◽  
2016 ◽  
Vol 134 ◽  
pp. 532-539 ◽  
Author(s):  
Yoshihito Shigihara ◽  
Hideyuki Hoshi ◽  
Semir Zeki
Keyword(s):  
Checkerboard Pattern ◽  
Cortical Responses ◽  
Pattern Stimulation ◽  
Visual Cortical

scholarly journals Cortical responses to moderate- and high-speed gratings extending 60° in the peripheral visual field

2016 ◽  
Vol 16 (12) ◽  
pp. 1179
Author(s):  
Kyriaki Mikellidou ◽  
Francesca Frijia ◽  
Domenico Montanaro ◽  
Vincenzo Greco ◽  
David Burr ◽  
...  
Keyword(s):  
Visual Field ◽  
High Speed ◽  
Peripheral Visual Field ◽  
Cortical Responses

scholarly journals Cortical reorganization of the visual system in post-stroke hemianopia studied with fMRI

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 334-334
Author(s):  
Gereon Nelles ◽  
Guido Widmann ◽  
Joachim Esser ◽  
Anette Meistrowitz ◽  
Johannes Weber ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Visual Stimuli ◽  
Checkerboard Pattern ◽  
Partial Recovery ◽  
Area 18 ◽  
Area 19 ◽  
Stimulation Of

102 Introduction: Restitution of unilateral visual field defects following occipital cortex lesions occurs rarely. Partial recovery, however, can be observed in patients with incomplete lesion of the visual cortex. Our objective was to study the neuroplastic changes in the visual system that underlie such recovery. Methods and Results: Six patients with a left PCA-territory cortical stroke and 6 healthy control subjects were studied during rest and during visual stimulation using a 1.5 T fMRI with a 40 mT gradient. Visual stimuli were projected with a laptop computer onto a 154 x 115 cm screen, placed 90 cm in front of the gantry. Subjects were asked to fixate a red point in the center of the screen during both conditions. During stimulation, a black-and-white checkerboard pattern reversal was presented in each hemifield. For each side, 120 volumes of 48 contiguous axial fMRI images were obtained during rest and during hemifield stimulation in alternating order (60 volumes for each condition). Significant differences of rCBF between stimulation and rest were assessed as group analyses using statistical parametric mapping (SPM 99; p<0.01, corrected for multiple comparison). In controls, strong increases of rCBF (Z=7.6) occurred in the contralateral primary visual cortex V1 (area 17) and in V3a (area 18) and V5 (area 19). No differences were found between the right and left side in controls. During stimulation of the unaffected (left) visual field in hemianopic patients, activation occurred in contralateral V1, but the strongest increases of rCBF (Z>10) were seen in contralateral V3a (area 18) and V5 (area 19). During stimulation of the hemianopic (right) visual field, no activation was found in the primary visual cortex of either hemisphere. The most significant activation (Z=9.2) was seen in the ipsilateral V3a and V5 areas, and contralateral (left) V3a. Conclusions: Partial recovery from hemianopia is associated with strong ipsilateral activation of the visual system. Processing of visual stimuli in the hemianopic side spares the primary visual cortex and may involve recruitment of neurons in ipsilateral (contralesional) areas V3a and V5.

scholarly journals Spatiotemporal adaptation through corticothalamic loops: A hypothesis

2000 ◽  
Vol 17 (1) ◽  
pp. 107-118 ◽  
Author(s):  
ULRICH HILLENBRAND ◽  
J. LEO van HEMMEN
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Lateral Geniculate Nucleus ◽  
Sensory Processing ◽  
Object Segmentation ◽  
Receptive Fields ◽  
The Novel ◽  
Spatiotemporal Structure ◽  
Cortical Responses ◽  
Cortical Receptive Fields

The thalamus is the major gate to the cortex and its control over cortical responses is well established. Cortical feedback to the thalamus is, in turn, the anatomically dominant input to relay cells, yet its influence on thalamic processing has been difficult to interpret. For an understanding of complex sensory processing, detailed concepts of the corticothalamic interplay need yet to be established. Drawing on various physiological and anatomical data, we elaborate the novel hypothesis that the visual cortex controls the spatiotemporal structure of cortical receptive fields via feedback to the lateral geniculate nucleus. Furthermore, we present and analyze a model of corticogeniculate loops that implements this control, and exhibit its ability of object segmentation by statistical motion analysis in the visual field.

Non-Linear Interactions in Cortical Responses to Bilateral vs Unilateral Visual Field Stimulation

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 62-62
Author(s):  
S P Ahlfors ◽  
J J Foxe ◽  
R J Ilmoniemi ◽  
G V Simpson
Keyword(s):  
Visual Field ◽  
Evoked Potentials ◽  
Normal Subjects ◽  
Stimulus Onset ◽  
Current Dipole ◽  
Field Patterns ◽  
Cortical Responses ◽  
Bilateral Case ◽  
Multichannel Recordings ◽  
Onset Asynchrony

Stimuli in different parts of the visual field can be perceived as independent entities and as conjoined wholes. It is of interest to determine whether there are cortical representations of the left and right hemifields which remain as independent entities when both hemifields are stimulated simultaneously and/or whether they interact to form a conjoined representation. We examined whether cortical processing of visual stimuli depends on whether they occur in isolation in one hemifield (unilaterally) or simultaneously in both hemifields (bilaterally). Visual evoked potentials of six normal subjects were recorded from 128 scalp sites. Wedge-shaped chequerboard stimuli, extending 1 – 4 deg eccentricity, were presented to quadrants of the visual field. Stimulus duration was 250 ms; the stimulus onset asynchrony was random, 500 – 750 ms. The evoked potentials revealed multiple peaks of activity with different surface topography. Prominent deflections occurred around 80, 120 – 180, and 230 ms. The response to bilateral stimuli was compared with the sum of the responses to unilateral stimuli. On the basis of the multichannel recordings, nonlinear interactions were characterised as either (a) modulations (same generators, but different amplitude) or (b) interactions originating from different generators. Modulation occurred at 230 ms, the response being suppressed for the bilateral case. At 120 – 180 ms, the field patterns suggested that at least some of the sources of the interaction effect are different from the source of the bilateral response. Underlying generators of the evoked responses and the interaction effects were further explored with the use of an equivalent current dipole model.

scholarly journals Pattern reversal visual evoked potentials in adults: variability with age

2017 ◽  
Vol 40 (6) ◽  
pp. 252 ◽  
Author(s):  
Raja Sawaya ◽  
Helen Sawaya ◽  
Gilbert Youssef
Keyword(s):  
Linear Trend ◽  
Age Groups ◽  
Normal Subjects ◽  
Pattern Reversal ◽  
Checkerboard Pattern ◽  
Check Size ◽  
Band Pass ◽  
The Difference ◽  
And Gender ◽  
Visual Evoked

Purpose: Pattern reversal visual evoked potential (PRVEP) is an electrophysiological test for evaluating the visual pathway. This study measured the changes in the latencies and amplitudes of the PRVEP with age and gender in normal subjects. Methods: Healthy participants (n=81; 162 total eyes), between the ages of 20 and 92 years were recruited for the study. Stimulation was performed monocularly with a high-contrast (>50%) black-white checkerboard pattern with a check size of 30° at a reversal rate of 2 Hz, a band-pass of 1-100 Hz, a sweep of 250 msec and an average of 150 stimulations in a dark room. Mean and standard deviations for three latencies (N75, P100 and N145) and the amplitude (N75-P100) for each decade were measured. Results: There was a linear trend by age for all three latencies, indicating that the higher age groups had longer latencies. The latencies decreased in the 5th decade before increasing in the higher age groups. The amplitude of N75-P100 decreased with age. The P100 latencies were longer in males than females in all age groups and the difference increased with increasing age.

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