Pharmacological isolation of visual cortical input to the cat accessory optic system: Effects of intravitreal tetrodotoxin on DTN unit responses

1991 ◽  
Vol 6 (2) ◽  
pp. 175-183 ◽  
Author(s):  
Keith L. Grasse
Keyword(s):  
Visual Cortex ◽  
Neural Mechanisms ◽  
Inhibitory Influence ◽  
Optic System ◽  
Accessory Optic System ◽  
Cortical Input ◽  
Before And After ◽  
Contralateral Eye ◽  
Visual Cortical ◽  
Stimulation Of

AbstractDirection-selective responses were recorded from neurons in the dorsal terminal nucleus (DTN) of the cat accessory optic system before and after intravitreal injections of tetrodotoxin (TTX) into the contralateral eye. After approximately 100 min, direction-selective responses driven through stimulation of the contralateral, injected eye were reduced on average by 90%, while direction-selective responses driven through stimulation of the ipsilateral, uninjected eye were not significantly reduced. By 200 min postinjection, ipsilateral direction-selective responses were either equal to or sometimes greater than control values. In the final stages of these experiments (i.e. between 390–830 min after contralateral eye injections), ipsilateral eye responses were on average 30% higher than control. The effects of retinal blockade of the contralateral eye by TTX show that input from the ipsilateral eye alone is sufficient to mediate direction-selective responses in DTN cells. These results and those observed following bicuculline eye injections reported previously (Grasse et al. 1990) demonstrate that direction-selective responses in the DTN driven through stimulation of the contralateral and ipsilateral eyes arise from independent neural mechanisms located in the retina and visual cortex, respectively. Moreover, these findings also suggest that the contralateral eye exerts an inhibitory influence over ipsilateral eye responses which is diminished by TTX injections into the contralateral eye.

Direction-selective responses of units in the dorsal terminal nucleus of cat following intravitreal injections of bicuculline

1990 ◽  
Vol 4 (6) ◽  
pp. 605-617 ◽  
Author(s):  
K.L. Grasse ◽  
M. Ariel ◽  
I.D. Smith
Keyword(s):  
Ganglion Cells ◽  
Intravitreal Injections ◽  
Retinal Ganglion ◽  
Optic System ◽  
Accessory Optic System ◽  
Before And After ◽  
Gaba Antagonist ◽  
Contralateral Eye ◽  
First Time ◽  
Stimulation Of

AbstractExtracellular recordings from single units in the dorsal terminal nucleus (DTN) of the cat accessory optic system (AOS) were before and after intravitreal injections of the GABA antagonist bicuculline methiodide (BMI). Direction-selective responses of DTN cells elicited through the contralateral, injected eye were aboloshed 7−12 h following the injection. For the concentrations tested, direction-selective responses through the contralateral (injected) eye did not recover within 26 h. Direction-selective responses through stimulation of the ipsilateral (uninjected) eye were also dramatically depressed for 1−9 h after contralateral eye injections. However, direction-selective responses through the ipsilateral eye eventually returned and were often more vigorous in the final stages. BMI injections into the ipsilateral eye failed to block direction-selective responses through the ipsilateral eye. The effects of intravitreal BMI on contralateral eye responses imply that DTN units receive input from direction-selective retinal ganglion cells. In addition, these results suggest that direction-selective input to the DTN from the visual cortex is independent of the retinal pathway. Using pharmacological methods described here, for the first time direction-selective responses of AOS units driven through the ipsilateral eye can be experimentally isolated.

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.

Excitatory amino acid receptor-mediated transmission in geniculocortical and intracortical pathways within visual cortex

1991 ◽  
Vol 66 (1) ◽  
pp. 293-306 ◽  
Author(s):  
L. J. Larson-Prior ◽  
P. S. Ulinski ◽  
N. T. Slater
Keyword(s):  
Visual Cortex ◽  
Amino Acid ◽  
Cortical Neurons ◽  
Excitatory Amino Acid ◽  
Nmda Antagonist ◽  
Receptor Subtypes ◽  
Excitatory Amino Acid Receptor ◽  
Visual Cortical ◽  
Stimulation Of

1. A preparation of turtle (Chrysemys picta and Pseudemys scripta) brain in which the integrity of the intracortical and geniculocortical pathways in visual cortex are maintained in vitro has been used to differentiate the excitatory amino acid (EAA) receptor subtypes involved in geniculocortical and intracortical synapses. 2. Stimulation of the geniculocortical fibers at subcortical loci produces monosynaptic excitatory postsynaptic potentials (EPSPs) in visual cortical neurons. These EPSPs are blocked by the broad-spectrum EAA receptor antagonist kynurenate (1-2 mM) and the non-N-methyl-D-aspartate (NMDA) antagonist 6, 7-dinitroquinoxaline-2,3-dione (DNQX, 10 microM), but not by the NMDA antagonist D,L-2-amino-5-phosphonovalerate (D,L-AP-5, 100 microM). These results indicate that the geniculocortical EPSP is mediated by EAAs that access principally, if not exclusively, EAA receptors of the non-NMDA subtypes. 3. Stimulation of intracortical fibers evokes compound EPSPs that could be resolved into three components differing in latency to peak. The component with the shortest latency was not affected by any of the EAA-receptor antagonists tested. The second component, of intermediate latency, was blocked by kyurenate and DNQX but not by D,L-AP-5. The component of longest latency was blocked by kynurenate and D,L-AP-5, but not by DNQX. These results indicate that the compound intracortical EPSP is comprised of three pharmacologically distinct components that are mediated by an unknown receptor, by quisqualate/kainate, and by NMDA receptors, respectively. 4. Repetitive stimulation of intracortical pathways at 0.33 Hz produces a dramatic potentiation of the late, D,L-AP-5-sensitive component of the intracortical EPSP. 5. These experiments lead to a hypothesis about the subtypes of EAA receptors that are accessed by the geniculocortical and intracortical pathways within visual cortex.

Renal prostanoids after unclipping the denervated one-kidney, one-clip hypertensive rat

1985 ◽  
Vol 249 (4) ◽  
pp. F542-F545 ◽  
Author(s):  
R. Vandongen ◽  
H. McGowan ◽  
H. Anderson ◽  
A. Barden
Keyword(s):  
Blood Pressure ◽  
Neural Mechanisms ◽  
Renal Nerves ◽  
Minor Role ◽  
Similar Extent ◽  
Before And After ◽  
Blood Pressures ◽  
A Minor ◽  
Prostanoid Synthesis ◽  
Stimulation Of

The contribution of the renal nerves in maintaining blood pressure and modulating renal prostanoid synthesis was examined in established (less than 8 wk in duration) one-kidney, one-clip (1K,1C) hypertension in the rat. Systolic blood pressure was measured for 7 days after renal denervation, at which time the renal artery clip was removed. Twenty-four-hour urinary excretion of PGE2 and 6-keto-PGF1 alpha (stable degradation product of PGI2) was determined before and after denervation and unclipping. Compared with sham-denervated rats, denervation (n = 15) resulted in a small but significant fall in blood pressure (from 216 +/- 4 to 182 +/- 4 mmHg after 48 h) and an increase in urinary 6-keto-PGF1 alpha (from 31 +/- 4 to 43 +/- 5 ng/24 h after 24 h). There was no change in PGE2 excretion. Seven days after surgery, blood pressures were similar in denervated (202 +/- 4 mmHg) and sham-denervated (211 +/- 5 mmHg) rats and fell to a similar extent 24 h after unclipping (142 +/- 3 and 147 +/- 4 mmHg, respectively). Urinary 6-keto-PGF1 alpha increased from 25 +/- 5 to 74 +/- 11 in denervated and 21 +/- 2 to 72 +/- 9 ng/24 h in sham-denervated rats in the 24 h after unclipping. PGE2 excretion increased approximately twofold over this period. These findings indicate that the renal nerves have only a minor role in established hypertension in the 1K,1C rat and that the reversal of hypertension and stimulation of renal prostanoid synthesis following unclipping is not dependent on neural mechanisms.

Visual telencephalon modulates directional selectivity of accessory optic neurons in pigeons

1990 ◽  
Vol 4 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Luiz R.G. Britto ◽  
Odival C. Gasparotto ◽  
Dânia E. Hamassaki
Keyword(s):  
Functional Organization ◽  
Visual Pathway ◽  
Directional Selectivity ◽  
Upward Motion ◽  
Optic System ◽  
Accessory Optic System ◽  
Before And After ◽  
Descending Systems ◽  
Best Responses

AbstractThe directional selectivity of units within the nucleus of the basal optic root (nBOR) of the accessory optic system (AOS) was studied before and after lesions of the visual telencephalon (visual Wulst) in urethane-anesthetized pigeons. In intact pigeons, most nBOR units preferred upward motion with a temporal component or downward motion with a nasal component. The ipsilateral and bilateral telencephalic lesions generated a dramatic reduction in the number of cells with optimal responses to upward motion. The overall distribution of preferred directions was still bimodal following ipsilateral or bilateral Wulst lesions, with most units showing best responses to a straight temporal or to downward-nasal directions. The contralateral Wulst lesions produced, instead, a marked reduction in downward preferences. The nBOR units which were studied in these cases showed mainly upward-temporal and upward-nasal responses. These data suggest an involvement of the visual Wulst in the determination of the dictional selectivity of nBOR neurons in the pigeon. Specifically, the responses of nBOR units to upward motion appeared to depend on the integrity of the telencephalic descending systems which impinge, in both direct and indirect ways, upon that AOS nucleus. Taken together with data for the mammalian AOS, the present results indicate that nonretinal afferents to AOS nuclei have an important role in the functional organization of that subcortical visual pathway.

Layer-specific serotonergic facilitation of IPSC in layer 2/3 pyramidal neurons of the visual cortex

2012 ◽  
Vol 107 (1) ◽  
pp. 407-416 ◽  
Author(s):  
Hyun-Jong Jang ◽  
Kwang-Hyun Cho ◽  
Sung-Won Park ◽  
Myung-Jun Kim ◽  
Shin Hee Yoon ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Visual Cortex ◽  
Pyramidal Neurons ◽  
Inhibitory Influence ◽  
Inhibitory Transmission ◽  
Layer 2 ◽  
Specific Manner ◽  
Intracellular Ca ◽  
Stimulation Of

Serotonin (5-hydroxytryptamine, 5-HT) inhibits the induction of long-term synaptic plasticity in layer 2/3 of the visual cortex at the end of its critical period in rats. However, the cellular and molecular mechanisms remain unclear. Since inhibitory influence is crucial in the induction of synaptic plasticity, the effect of 5-HT on inhibitory transmission was investigated in layer 2/3 pyramidal neurons of the primary visual cortex. The amplitude of inhibitory postsynaptic current (IPSC), but not excitatory postsynaptic current, evoked by stimulation of the underlying layer 4, was increased by ∼20% with a bath application of 5-HT. The amplitude of miniature IPSC was also increased by the application of 5-HT, while the paired-pulse ratio was not changed. The facilitating effect of 5-HT on IPSC was mediated by the activation of 5-HT2 receptors. An increase in intracellular Ca2+ via release from inositol 1,4,5-trisphosphate (IP3)-sensitive stores, which was confirmed by confocal Ca2+ imaging, and activation of Ca2+/calmodulin-dependent kinase II (CaMKII) were involved in the facilitation of IPSC by 5-HT. However, 5-HT failed to facilitate IPSC evoked by the stimulation of layer 1. These results suggest that activation of 5-HT2 receptors releases intracellular Ca2+ via IP3-sensitive stores, which facilitates GABAAergic transmission via the activation of CaMKII in layer 2/3 pyramidal neurons of the visual cortex in a layer-specific manner. Thus facilitation of inhibitory transmission by 5-HT might be involved in regulating the information flow and the induction of long-term synaptic plasticity, in a pathway-specific manner.

scholarly journals Dynamic Electrical Stimulation of Sites in Visual Cortex Produces Form Vision in Sighted and Blind Humans

2018 ◽  
Author(s):  
Michael S. Beauchamp ◽  
William Bosking ◽  
Ping Sun ◽  
Brett Foster ◽  
Soroush Niketeghad ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Visual Cortex ◽  
Visual Display ◽  
Current Steering ◽  
Form Vision ◽  
Visual Cortical ◽  
Stimulation Paradigm ◽  
Blind Humans ◽  
Field Location ◽  
Stimulation Of

AbstractVisual cortical prosthetics (VCPs) offer the promise of restoring sight to blind patients. Electrical stimulation of a single site in visual cortex can reliably produce a percept of a spot of light in a fixed visual field location, known as a phosphene. Researchers developing VCPs have assumed that multiple phosphenes produced by concurrent stimulation of multiple sites in visual cortex can combine to form a coherent form, like pixels in a visual display. However, existing data do not support this assumption. Therefore, we developed a novel stimulation paradigm for VCPs termed dynamic current steering in which the visual form to be conveyed is traced on the surface of visual cortex by electrically stimulating electrodes in a dynamic sequence. When tested in sighted and blind subjects, this method of stimulating visual cortex allowed for the immediate recognition of a variety of letter shapes without training and with high accuracy.One Sentence SummaryStimulating human visual cortex using dynamic patterns of activity allows both blind and sighted patients to perceive visual percepts of useful forms.

Recovery of binocular function in kitten visual cortex

1982 ◽  
Vol 48 (6) ◽  
pp. 1336-1346 ◽  
Author(s):  
F. B. Levitt ◽  
R. C. Van Sluyters
Keyword(s):  
Visual Cortex ◽  
Striate Cortex ◽  
Recovery Period ◽  
Receptive Fields ◽  
Cortical Input ◽  
Before And After ◽  
The Difference ◽  
Group 5 ◽  
Comparison Of The Results ◽  
The Relationship

1. This paper describes the results of an experiment designed to examine the ability of cells in the kitten's visual cortex to regain functional binocular connections following exposure to a brief period of visual deprivation. 2. Normal 4-wk-old kittens were exposed to a total of 12 h of optically induced strabismus over a period of 2 days, and single-unit recordings made the following day indicated that the proportion of striate cortex cells with binocular receptive fields had decreased sharply as a result of this episode of strabismic vision. 3. When these kittens were revived and allowed to experience a recovery period of normal binocular vision lasting either 3 or 7 wk, cortical binocularity returned to a normal level. 4. Statistical analysis revealed that the difference in the level of binocularity observed before and after the period of binocular recovery was highly significant, and comparison of the results from kittens allowed only a 3-wk recovery period with those from kittens allowed a 7-wk period indicated that a similar level of recovery was obtained in each group. 5. Histological reconstruction of electrode penetrations indicated that the recovery of binocular receptive fields occurred uniformly across all cortical laminae. 6. These data are discussed in terms of the results from previous recovery experiments, the relationship between cortical binocularity and the ability to maintain binocular fixation, and the possibility that subliminal cortical input plays a role in the recovery of functional binocular cells.

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