Spatiotemporal structure of depolarization spread in cortical pyramidal cell populations evoked by diffuse retinal light flashes

1999 ◽  
Vol 16 (1) ◽  
pp. 65-79 ◽  
Author(s):  
DAVID M. SENSEMAN
Keyword(s):  
Visual Cortex ◽  
Pyramidal Cell ◽  
Spatiotemporal Structure ◽  
Retinal Stimulation ◽  
Medial Cortex ◽  
Photodiode Array ◽  
Initial Activation ◽  
Cortical Pyramidal Cell ◽  
Light Flashes ◽  
Stimulation Of

The spatiotemporal structure of cortical activity evoked by diffuse light flashes was investigated in an isolated eyecup-brain preparation of the pond turtle, Pseudemys scripta. By combining a photomicroscopic image of the preparation with voltage-sensitive dye signals recorded by a 464-element photodiode array, the spread of depolarization within different cortical areas could be directly visualized with millisecond temporal resolution. Diffuse stimulation of the contralateral eyecup initially depolarized the visual cortex at the junction between its lateral and medial divisions in a small area rostral of the ventricular eminence. From this point, the depolarization spread at different velocities (10–100 μm/ms) depending upon the direction of travel. Since the initial depolarization was always in the rostral pole, the largest spread invariably occurred in a rostral → caudal direction. Within the confines of the medial visual cortex, depolarization spread at a constant velocity but slowed after entering the adjoining medial cortex. Increasing the stimulus illuminance increased the velocity of spread. Rostrocaudal spread of depolarization was also observed in response to electrical stimulation of the geniculocortical pathway and by direct focal stimulation of the cortical sheet. These data suggest that excitatory connections between pyramidal cell clusters play a prominent role in the initial activation of the cortex by diffuse retinal stimulation.

Phosphene perceptions and safety of chronic visual cortex stimulation in a blind subject

2020 ◽  
Vol 132 (6) ◽  
pp. 2000-2007 ◽  
Author(s):  
Soroush Niketeghad ◽  
Abirami Muralidharan ◽  
Uday Patel ◽  
Jessy D. Dorn ◽  
Laura Bonelli ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Adverse Events ◽  
Clinical Intervention ◽  
Occipital Cortex ◽  
Neuronal Population ◽  
Serious Adverse Events ◽  
Stimulation Parameters ◽  
The Right ◽  
Visual Cortical ◽  
Stimulation Of

Stimulation of primary visual cortices has the potential to restore some degree of vision to blind individuals. Developing safe and reliable visual cortical prostheses requires assessment of the long-term stability, feasibility, and safety of generating stimulation-evoked perceptions.A NeuroPace responsive neurostimulation system was implanted in a blind individual with an 8-year history of bare light perception, and stimulation-evoked phosphenes were evaluated over 19 months (41 test sessions). Electrical stimulation was delivered via two four-contact subdural electrode strips implanted over the right medial occipital cortex. Current and charge thresholds for eliciting visual perception (phosphenes) were measured, as were the shape, size, location, and intensity of the phosphenes. Adverse events were also assessed.Stimulation of all contacts resulted in phosphene perception. Phosphenes appeared completely or partially in the left hemifield. Stimulation of the electrodes below the calcarine sulcus elicited phosphenes in the superior hemifield and vice versa. Changing the stimulation parameters of frequency, pulse width, and burst duration affected current thresholds for eliciting phosphenes, and increasing the amplitude or frequency of stimulation resulted in brighter perceptions. While stimulation thresholds decreased between an average of 5% and 12% after 19 months, spatial mapping of phosphenes remained consistent over time. Although no serious adverse events were observed, the subject experienced mild headaches and dizziness in three instances, symptoms that did not persist for more than a few hours and for which no clinical intervention was required.Using an off-the-shelf neurostimulator, the authors were able to reliably generate phosphenes in different areas of the visual field over 19 months with no serious adverse events, providing preliminary proof of feasibility and safety to proceed with visual epicortical prosthetic clinical trials. Moreover, they systematically explored the relationship between stimulation parameters and phosphene thresholds and discovered the direct relation of perception thresholds based on primary visual cortex (V1) neuronal population excitation thresholds.

scholarly journals Electrical Stimulation of the Human Visual Cortex Preliminary Report

1974 ◽  
Vol 1 (4) ◽  
pp. 236-238 ◽  
Author(s):  
Andrew Talalla ◽  
Leo Bullara ◽  
Robert Pudenz
Keyword(s):  
Electrical Stimulation ◽  
Visual Cortex ◽  
Feasibility Study ◽  
Preliminary Report ◽  
Visual Prosthesis ◽  
Human Visual Cortex ◽  
Stimulation Of

SUMMARY:A feasibility study for the development of a human visual prosthesis has led several workers to observe the effects of electrical stimulation of the human visual cortex. Experience with such stimulations of three normal-sighted patients is reported. The results confirm some of the findings of other workers, but do not show that multiple phosphenes were experienced by our patients, using strictly limited parameters of stimulation.

Force relaxes before the fall of cytosolic calcium in the photomechanical response of rat sphincter pupillae

2000 ◽  
Vol 279 (1) ◽  
pp. C274-C280 ◽  
Author(s):  
Andrew P. Krivoshik ◽  
Lloyd Barr
Keyword(s):  
Myosin Light Chain ◽  
Smooth Muscles ◽  
Cytosolic Calcium ◽  
Myosin Phosphorylation ◽  
Primary Signal ◽  
Intracellular Ca ◽  
Phosphorylation Cascade ◽  
Muscle Myosin ◽  
Light Flashes ◽  
Stimulation Of

In the rat sphincter pupillae, as in other smooth muscles, the primary signal transduction cascade for agonist activation is receptor → G protein → phospholipase C → inositol trisphosphate → intracellular Ca2+concentration ([Ca2+]i) → calmodulin → myosin light chain kinase → phosphorylated myosin → force development. Light stimulation of isolated sphincters pupillae can be very precisely controlled, and precise reproducible photomechanical responses (PMRs) result. This precision makes the PMR ideal for testing models of regulation of smooth muscle myosin phosphorylation. We measured force and [Ca2+]iconcurrently in sphincter pupillae following stimulation by light flashes of varying duration and intensity. We sampled at unusually short (0.01–0.02 s) intervals to adequately test a PMR model based on the myosin phosphorylation cascade. We found, surprisingly, contrary to the behavior of intestinal muscle and predictions of the phosphorylation model, that during PMRs force begins to decay while [Ca2+]iis still rising. We conclude that control of contraction in the sphincter pupillae probably involves an inhibitory process as well as activation by [Ca2+]i.

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 Right hemispheric dominance of visual phenomena evoked by intracerebral stimulation of the human visual cortex

2013 ◽  
Vol 35 (7) ◽  
pp. 3360-3371 ◽  
Author(s):  
Jacques Jonas ◽  
Solène Frismand ◽  
Jean-Pierre Vignal ◽  
Sophie Colnat-Coulbois ◽  
Laurent Koessler ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Hemispheric Dominance ◽  
Human Visual Cortex ◽  
Visual Phenomena ◽  
Stimulation Of

Replicating the Role of the Human Retina for a Cortical Visual Neuroprosthesis

2013 ◽  
pp. 1532-1551
Author(s):  
Samuel Romero ◽  
Christian Morillas ◽  
Antonio Martínez ◽  
Begoña del Pino ◽  
Francisco Pelayo ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Significant Degree ◽  
Research Field ◽  
Human Retina ◽  
Direct Stimulation ◽  
Biologically Inspired ◽  
Visual Inputs ◽  
Response Modeling ◽  
Stimulation Of

Neuroengineering is an emerging research field combining the latest findings from neuroscience with developments in a variety of engineering disciplines to create artificial devices, mainly for therapeutical purposes. In this chapter, an application of this field to the development of a visual neuroprosthesis for the blind is described. Electrical stimulation of the visual cortex in blind subjects elicits the perception of visual sensations called phosphenes, a finding that encourages the development of future electronic visual prostheses. However, direct stimulation of the visual cortex would miss a significant degree of image processing that is carried out by the retina. The authors describe a biologically-inspired retina-like processor designed to drive the implanted stimulator using visual inputs from one or two cameras. This includes dynamic response modeling with minimal latency. The outputs of the retina-like processor are comparable to those recorded in biological retinas that are exposed to the same stimuli and allow estimation of the original scene.

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