scholarly journals Multifocal VEP recordings can be used to identify the onset of cortical activity after visual stimulation for different parts of the visual field

2010 ◽  
Vol 5 (8) ◽  
pp. 434-434
Author(s):  
T. Meigen ◽  
M. Kramer
Keyword(s):  
Visual Field ◽  
Visual Stimulation ◽  
Cortical Activity ◽  
Multifocal Vep ◽  
Different Parts

scholarly journals A machine-learning algorithm correctly classifies cortical evoked potentials from both natural retinal stimulation and electrical stimulation of the optic nerve

2021 ◽  
Author(s):  
Vivien Gaillet ◽  
Elodie Geneviève Zollinger ◽  
Diego Ghezzi
Keyword(s):  
Electrical Stimulation ◽  
Visual Cortex ◽  
Optic Nerve ◽  
Visual Field ◽  
Primary Visual Cortex ◽  
Nerve Stimulation ◽  
Visual Stimulation ◽  
Cortical Activity ◽  
Artificial Vision ◽  
Optic Nerve Stimulation

AbstractObjectiveOptic nerve’s intraneural stimulation is an emerging neuroprosthetic approach to provide artificial vision to totally blind patients. An open question is the possibility to evoke individual non-overlapping phosphenes via selective intraneural optic nerve stimulation. To begin answering this question, first, we aim at showing in preclinical experiments with animals that each intraneural electrode could evoke a distinguishable activity pattern in the primary visual cortex.ApproachWe performed both patterned visual stimulation and patterned electrical stimulation in healthy rabbits while recording evoked cortical activity with an electrocorticogram array in the primary visual cortex. Electrical stimulation was delivered to the optic nerve with the intraneural array OpticSELINE. We used a support vector machine algorithm paired to a linear regression model to classify cortical responses originating from visual stimuli located in different portions of the visual field and electrical stimuli from the different electrodes of the OpticSELINE.Main resultsCortical activity induced by visual and electrical stimulation could be classified with nearly 100% accuracy relative to the specific location in the visual field or electrode in the array from which it originated. For visual stimulation, the accuracy increased with the separation of the stimuli and reached 100% for separation higher than 7 degrees. For electrical stimulation, at low current amplitudes, the accuracy increased with the distance between electrodes, while at higher current amplitudes, the accuracy was nearly 100% already for the shortest separation.SignificanceOptic nerve’s intraneural stimulation with the OpticSELINE induced discernible cortical activity patterns. These results represent a leap forward for intraneural optic nerve stimulation towards artificial vision.

Effect of temporal sparseness and dichoptic presentation on multifocal visual evoked potentials

2005 ◽  
Vol 22 (1) ◽  
pp. 45-54 ◽  
Author(s):  
ANDREW C. JAMES ◽  
RASA RUSECKAITE ◽  
TED MADDESS
Keyword(s):  
Visual Field ◽  
Human Subjects ◽  
Signal To Noise ◽  
Recording Time ◽  
Contrast Gain ◽  
Upper Visual Field ◽  
Multifocal Vep ◽  
Normal Human ◽  
Time Decomposition ◽  
Peak Value

Multifocal VEP (mfVEP) responses were obtained from 13 normal human subjects for nine test conditions, covering three viewing conditions (dichoptic and left and right monocular), and three different temporal stimulation forms (rapid contrast reversal, rapid pattern pulse presentation, and slow pattern pulse presentation). The rapid contrast reversal stimulus had pseudorandomized reversals of checkerboards in each visual field region at a mean rate of 25 reversals/s, similar to most mfVEP studies to date. The rapid pattern pulse presentation had pseudorandomized presentations of a checkerboard for one frame, interspersed with uniform grey frames, with a mean rate of 25 presentations/s per region per eye. The slow pattern pulse stimulus had six presentations/s per region per eye. Recording time was 5.3 min/condition. For dichoptic presentation slow pattern pulse responses were 4.6 times larger in amplitude than the contrast reversal responses. Binocular suppression was greatest for the contrast reversal stimulus. Consideration of the signal-to-noise ratios indicated that to achieve a given level of reliability, slow pattern pulse stimuli would require half the recording time of contrast reversal stimuli for monocular viewing, and 0.4 times the recording time for dichoptically presented stimuli. About half the responses to the slow pattern pulse stimuli had peak value exceeding five times their estimated standard error. Responses were about 20% smaller in the upper visual field locations. Space–time decomposition showed that responses to slow pattern pulse were more consistent across visual field locations. We conclude that the pattern pulse stimuli, which we term temporally sparse, maintain the visual system in a high contrast gain state. This more than compensates for the smaller number of presentations in the run, and provides signal-to-noise advantages that may be valuable in clinical application.

Visual and sensorimotor cortices mapping during awake resection of lesion on the right periatrium: a case report on brainwaves and their peculiar patterns

2014 ◽  
Vol 2 (1-4) ◽  
Author(s):  
Zamzuri Idris ◽  
Ch’ng Chee How ◽  
Jafri Malin Abdullah
Keyword(s):  
Visual Field ◽  
Brain Mapping ◽  
New Technologies ◽  
Visual Stimulation ◽  
Brain Atlas ◽  
Brain Functions ◽  
Eloquent Areas ◽  
Neurosurgical Planning ◽  
Visual Field Deficits ◽  
Visual Evoked

AbstractAdvances in neurosurgery have allowed for more sophisticated mapping of various eloquent neural structures including the visual cortex. Applications of various modalities of new technologies allow accurate brain mapping for neurosurgical planning and preservation of functions in patients with lesions involving the eloquent cortex. The authors demonstrate the use of various new technologies for accurate presurgical planning, preservation of brain functions, and depiction of patterns of cortical brainwaves, which relate to motor networks and continuous visual stimuli.A patient with a right periatrial lesion involving the optic radiation with no visual field deficits was operated under an awake state and under continuous contralateral electrocorticography and visual monitoring. Presurgically, extra-operative brain mapping for visual-, sensory-, and motor-evoked magnetic fields were completed using magnetoencephalography (MEG). The dipole areas were identified, and the images were fused with a 116-region cortical brain atlas. The ideal trajectory was planned based on these images and diffusion tensor imaging (tractography). The trans-sulcal approachA good agreement for eloquent areas was identified based on extra-operative MEG and intra-operative neurostimulation mappings. The patient had no new neurological or visual-field deficits after the surgery. Certain patterns of brainwaves for motor cortex and visual stimulation were obtained: (a) spikes at the contralateral sensorimotor area when the motor strip was stimulated and (b) up-down and dense-loose continuous visual-evoked brainwaves at the occipital pole toward flashing checkerboard visual stimulation.A combination of extra- and intra-operative brain mappings should ideally be done in patients harboring lesions near eloquent areas. The continuous visual-evoked potential monitoring, using a grid electrode and flashing checkerboard and contralateral sensorimotor responses, observed in our case is interesting and needs further studies.

Induced Roll Vection from Stimulation of the Central Visual Field

1987 ◽  
Vol 31 (2) ◽  
pp. 263-265 ◽  
Author(s):  
George J. Andersen ◽  
Brian P. Dyre
Keyword(s):  
Visual Field ◽  
Visual Information ◽  
Visual Stimulation ◽  
Postural Instability ◽  
Flight Simulation ◽  
Limited Area ◽  
Central Visual Field ◽  
Forward Motion ◽  
Self Motion ◽  
Stimulation Of

An important consideration for some types of flight simulation is that sufficient visual information be provided for a perception of self-motion. A general conclusion of earlier research is that peripheral stimulation (outside a 30 deg. diameter area of the central visual field) is necessary for perceived self-motion to occur. More recently Andersen and Braunstein (1985) demonstrated that induced self-motion could occur when visual information simulating forward motion of the observer was presented to a limited area of the central visual field. In the present study, the perception of induced roll vection (rotation about the line of sight) from visual stimulation of the central visual field was examined. Subjects viewed computer generated displays that simulated observer motion relative to a volume of randomly positioned points. Two variables were examined: 1) the presence or absence of a simulated forward motion, and 2) the presence of a 15 deg. or 30 deg. sinusoidal roll motion. It was found that: 1) induced roll vection occurred with stimulation restricted to a 10 deg. diameter area of the central visual field; 2) greater postural instability occurred for displays with a 30 deg. roll as compared to a 15 deg. roll; and 3) significantly greater postural instability occurred along the X-axis (left/right) as compared to the Y-axis (front/back). The implications of this research for flight simulation will be discussed.

scholarly journals Mapping Visual Field Defects With fMRI – Impact of Approach and Experimental Conditions

2021 ◽  
Vol 15 ◽  
Author(s):  
Gokulraj T. Prabhakaran ◽  
Khaldoon O. Al-Nosairy ◽  
Claus Tempelmann ◽  
Hagen Thieme ◽  
Michael B. Hoffmann
Keyword(s):  
Visual Field ◽  
Sensitivity And Specificity ◽  
Color Change ◽  
Visual Stimulation ◽  
Block Design ◽  
Visual Field Defects ◽  
Automated Perimetry ◽  
Standard Automated Perimetry ◽  
Experimental Conditions ◽  
The Impact

Current initiatives to restore vision emphasize the need for objective assessments of visual field (VF) defects as pursued with functional magnetic resonance imaging (fMRI) approaches. Here, we compared population receptive field (pRF) mapping-based VF reconstructions to an fMRI method that uses more robust visual stimulation (on-off block design) in combination with individualized anatomy-driven retinotopic atlas-information (atlas-based VF). We investigated participants with sizable peripheral VF-deficits due to advanced glaucoma (n = 4) or retinitis pigmentosa (RP; n = 2) and controls (n = 6) with simulated scotoma. We obtained (1) standard automated perimetry (SAP) data as reference VFs and 3T fMRI data for (2) pRF-mapping [8-direction bar stimulus, fixation color change task] and (3) block-design full-field stimulation [8-direction drifting contrast patterns during (a) passive viewing (PV) and (b) one-back-task (OBT; reporting successions of identical motion directions) to probe the impact of previously reported task-related unspecific visual cortex activations]. Correspondence measures between the SAP and fMRI-based VFs were accuracy, assisted by sensitivity and specificity. We found an accuracy of pRF-based VF from V1 in patients [median: 0.62] that was similar to previous reports and increased by adding V2 and V3 to the analysis [0.74]. In comparison to the pRF-based VF, equivalent accuracies were obtained for the atlas-based VF for both PV [0.67] and, unexpectedly, the OBT [0.59], where, however, unspecific cortical activations were reflected by a reduction in sensitivity [0.71 (PV) and 0.35 (OBT)]. In conclusion, in patients with peripheral VF-defects, we demonstrate that previous fMRI procedures to obtain VF-estimates might be enhanced by: (1) pooling V1-V3 to enhance accuracy; (2) reporting sensitivity and specificity measures to increase transparency of the VF-reconstruction metric; (3) applying atlas-based procedures, if pRF-based VFs are not available or difficult to obtain; and (4) giving, counter-intuitively, preference to PV. These findings are expected to provide guidance to overcome current limitations of translating fMRI-based methods to a clinical work-up.

Visual Stimulus–Dependent Changes in Interhemispheric EEG Coherence in Ferrets

1999 ◽  
Vol 82 (6) ◽  
pp. 3082-3094 ◽  
Author(s):  
D. C. Kiper ◽  
M. G. Knyazeva ◽  
L. Tettoni ◽  
G. M. Innocenti
Keyword(s):  
Visual Field ◽  
Corpus Callosum ◽  
Experimental Validation ◽  
Visual Stimulation ◽  
Eeg Coherence ◽  
Vertical Meridian ◽  
Callosal Connections ◽  
Interhemispheric Coherence ◽  
Cortical Connections ◽  
Visual Areas

In recent years, the analysis of the coherence between signals recorded from the scalp [electroencephalographic (EEG) coherence] has been used to assess the functional properties of cortico-cortical connections, both in animal models and in humans. However, the experimental validation of this technique is still scarce. Therefore we applied it to the study of the callosal connections between the visual areas of the two hemispheres, because this particular set of cortico-cortical connections can be activated in a selective way by visual stimuli. Indeed, in primary and in low-order secondary visual areas, callosal axons interconnect selectively regions, which represent a narrow portion of the visual field straddling the vertical meridian and, within these regions, neurons that prefer the same stimulus orientation. Thus only isooriented stimuli located near the vertical meridian are expected to change interhemispheric coherence by activating callosal connections. Finally, if such changes are found and are indeed mediated by callosal connections, they should disappear after transection of the corpus callosum. We perfomed experiments on seven paralyzed and anesthetized ferrets, recording their cortical activity with epidural electrodes on areas 17/18, 19, and lateral suprasylvian, during different forms of visual stimulation. As expected, we found that bilateral iso-oriented stimuli near the vertical meridian, or extending across it, caused a significant increase in interhemispheric coherence in the EEG beta-gamma band. Stimuli with different orientations, stimuli located far from the vertical meridian, as well as unilateral stimuli failed to affect interhemispheric EEG coherence. The stimulus-induced increase in coherence disappeared after surgical transection of the corpus callosum. The results suggest that the activation of cortico-cortical connections can indeed be revealed as a change in EEG coherence. The latter can therefore be validly used to investigate the functionality of cortico-cortical connections.

PS-16-7 Visual evoked cortical magnetic responses: effects of visual field and visual stimulation

1995 ◽  
Vol 97 (4) ◽  
pp. S124-S125 ◽  
Author(s):  
Hiroshi Shigeto ◽  
Shozo Tobimatsu ◽  
Tomoya Yamamoto ◽  
Takuro Kobayashi ◽  
Motohiro Kato
Keyword(s):  
Visual Field ◽  
Visual Stimulation ◽  
Visual Evoked

Cueing Attention by Relative Motion in the Periphery of the Visual Field

Perception ◽  
10.1068/p5752 ◽  
2007 ◽  
Vol 36 (7) ◽  
pp. 955-970 ◽  
Author(s):  
Dorothe A Poggel ◽  
Hans Strasburger ◽  
Manfred MacKeben
Keyword(s):  
Visual Field ◽  
Flow Field ◽  
Relative Motion ◽  
Visual Stimulation ◽  
Discrimination Performance ◽  
Body Motion ◽  
Practical Relevance ◽  
Visual Objects ◽  
Field Patterns ◽  
Contrast Thresholds

Sudden changes of visual stimulation attract attention. The observer's body motion generates retinal-flow field patterns containing information about his/her own speed and trajectory and relative motion of other objects. We investigated the effectiveness of relative motion as an attentional cue and compared it with conventional cueing by appearance of a frame in the far periphery of the visual field. In a group of ten subjects, contrast thresholds for the perception of static Gabor grating orientation [four alternative non-forced-choice (4ANFC)] task were determined at 20°, 30°, 40°, and 60° eccentricity. Subsequently, near-threshold discrimination performance of Gabor pattern orientation without versus with a ring-shaped cue was measured at the same positions. The same Gabor patterns were then presented embedded in a random-dot flow field, and uncued discrimination performance was compared with performance after presentation of a relative-motion cue (RMC), ie a small random-dot field with motion in the opposite direction of the flow field. Both the conventional ring cue and the RMC induced significantly increased discrimination performance at all test locations. With the parameters chosen for this study, the RMC was slightly less effective than the conventional cue, but its effects were somewhat more pronounced in the far periphery of the visual field. Thus, relative motion is a powerful cue to attract attention to peripheral visual objects and improves performance as effectively as a conventional ring cue. The findings have practical relevance for everyday life, in particular for tasks like driving and navigation.

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