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Henk Spekreijse - One of the best experts on this subject based on the ideXlab platform.
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the dynamic characteristics of the Feedback Signal from horizontal cells to cones in the goldfish retina
The Journal of Physiology, 2001Co-Authors: Maarten Kamermans, Dick Kraaij, Henk SpekreijseAbstract:1The dynamic properties of the microcircuitry formed by cones and horizontal cells in the isolated goldfish retina were studied. Cones project to horizontal cells and horizontal cells feed back to cones via a relatively slow negative Feedback pathway. 2The time constant of the Feedback Signal in cones and of the effect this Feedback Signal had on the responses of second-order neurons was determined using whole-cell patch clamp and intracellular recording techniques. 3It was found that the Feedback Signal in cones had a time constant of around 80 ms, whereas the time constant of the effect this Feedback Signal had on the second-order neurons ranged from 36 to 116 ms. This range of time constants can be accounted for by the non-linearity of the Ca2+ current in the cones. In depolarized cones, the Feedback-mediated response in second-order neurons had a similar time constant to that of the direct light response of the cone, whereas in hyperpolarized cones, the time constant of the Feedback-mediated response in second-order neurons was considerably larger. 4Further, it was shown that there was no delay in the Feedback pathway. This is in contrast to what has been deduced from the response properties of second-order neurons. In one type of horizontal cell, the responses to red light were delayed relative to the responses to green light. This delay in the second-order neurons can be accounted for by the interaction of the direct light response of the medium-wavelength-sensitive cones (M-cones) with the Feedback response of the M-cones received from the horizontal cells.
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spectral sensitivity of the Feedback Signal from horizontal cells to cones in goldfish retina
Visual Neuroscience, 1998Co-Authors: Dick Kraaij, Maarten Kamermans, Henk SpekreijseAbstract:The spectral sensitivity of cones in isolated goldfish retina was determined with whole-cell recording techniques. Three spectral classes of cones were found with maximal sensitivities around 620 nm, 540 nm, and 460 nm. UV-cones were not found because our stimulator did not allow effective stimulation in the UV range. The spectral sensitivity of the cones closely matched the cone photopigment absorption spectra at the long wavelength side of the spectrum, but deviated significantly at shorter wavelengths. Surround stimulation induced an inward current in cones due to Feedback from horizontal cells. The spectral sensitivity of this Feedback Signal was determined in all three cone classes and found to be broader than the spectral sensitivity of the cones recorded from, and to be spectrally nonopponent. These data are consistent with a connectivity scheme between cones and horizontal cells in which the three horizontal cell systems feed back to all cone systems and in which all horizontal cell systems receive input from more than one cone system.
Clifford R Weir - One of the best experts on this subject based on the ideXlab platform.
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modification of smooth pursuit initiation by a nonvisual afferent Feedback Signal
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Clifford R Weir, Paul C KnoxAbstract:PURPOSE: To investigate the role of extraocular muscle afferent Signals in the initiation and early maintenance of smooth-pursuit eye movements. METHODS: A suction scleral contact lens was used to impede the movements of the right eye while subjects tracked small targets in a step-ramp pursuit paradigm. Movements of the left eye were measured by infrared oculography. Pursuit latency, eye acceleration, and velocity were analyzed trial-by-trial and compared before, while, and after the right eye was impeded. RESULTS: When the right eye was impeded, initial acceleration and eye velocity were reduced. Pursuit latency was unchanged. The velocity effect had a rapid onset and offset; there was no evidence that the effects built up over a number of trials. Detailed analysis suggested that the reduction in velocity occurred approximately 40 msec after pursuit was initiated. CONCLUSIONS: These results are consistent with the hypothesis that extraocular muscle afferent Signals provide a Feedback Signal of the movements of the eyes that may be used to modify the initiation and early maintenance of smooth pursuit on-line. It appears that for pursuit, as with saccades, the priority in these conditions is to maintain conjugacy.
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modification of visually guided saccades by a nonvisual afferent Feedback Signal
Investigative Ophthalmology & Visual Science, 2000Co-Authors: Paul C Knox, Clifford R Weir, Paul J MurphyAbstract:PURPOSE. To investigate the role of extraocular muscle afferent Signals in the control of saccadic eye movements. METHODS. A suction scleral contact lens was used to impede the movements of the right eye while subjects executed visually guided saccades to briefly presented targets. Movements of the left eye were measured using infrared oculography. Saccade amplitude, peak velocity, and duration were analyzed trial by trial and compared before, during, and after the right eye was impeded. RESULTS. When the right eye was impeded, the amplitudes of saccades executed by the left eye were reduced. There was no alteration in the main sequence relationships. The amplitude effect had a rapid onset and offset. There was no evidence that the effects built up over a number of trials, nor was there evidence that individual saccades were modified on-line. CONCLUSIONS. These results are consistent with the hypothesis that extraocular muscle afferent Signals provide a Feedback Signal of the movements of the eyes that is used to produce rapid adjustments of oculomotor output when required.
Paul C Knox - One of the best experts on this subject based on the ideXlab platform.
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modification of smooth pursuit initiation by a nonvisual afferent Feedback Signal
Investigative Ophthalmology & Visual Science, 2001Co-Authors: Clifford R Weir, Paul C KnoxAbstract:PURPOSE: To investigate the role of extraocular muscle afferent Signals in the initiation and early maintenance of smooth-pursuit eye movements. METHODS: A suction scleral contact lens was used to impede the movements of the right eye while subjects tracked small targets in a step-ramp pursuit paradigm. Movements of the left eye were measured by infrared oculography. Pursuit latency, eye acceleration, and velocity were analyzed trial-by-trial and compared before, while, and after the right eye was impeded. RESULTS: When the right eye was impeded, initial acceleration and eye velocity were reduced. Pursuit latency was unchanged. The velocity effect had a rapid onset and offset; there was no evidence that the effects built up over a number of trials. Detailed analysis suggested that the reduction in velocity occurred approximately 40 msec after pursuit was initiated. CONCLUSIONS: These results are consistent with the hypothesis that extraocular muscle afferent Signals provide a Feedback Signal of the movements of the eyes that may be used to modify the initiation and early maintenance of smooth pursuit on-line. It appears that for pursuit, as with saccades, the priority in these conditions is to maintain conjugacy.
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modification of visually guided saccades by a nonvisual afferent Feedback Signal
Investigative Ophthalmology & Visual Science, 2000Co-Authors: Paul C Knox, Clifford R Weir, Paul J MurphyAbstract:PURPOSE. To investigate the role of extraocular muscle afferent Signals in the control of saccadic eye movements. METHODS. A suction scleral contact lens was used to impede the movements of the right eye while subjects executed visually guided saccades to briefly presented targets. Movements of the left eye were measured using infrared oculography. Saccade amplitude, peak velocity, and duration were analyzed trial by trial and compared before, during, and after the right eye was impeded. RESULTS. When the right eye was impeded, the amplitudes of saccades executed by the left eye were reduced. There was no alteration in the main sequence relationships. The amplitude effect had a rapid onset and offset. There was no evidence that the effects built up over a number of trials, nor was there evidence that individual saccades were modified on-line. CONCLUSIONS. These results are consistent with the hypothesis that extraocular muscle afferent Signals provide a Feedback Signal of the movements of the eyes that is used to produce rapid adjustments of oculomotor output when required.
Maarten Kamermans - One of the best experts on this subject based on the ideXlab platform.
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the dynamic characteristics of the Feedback Signal from horizontal cells to cones in the goldfish retina
The Journal of Physiology, 2001Co-Authors: Maarten Kamermans, Dick Kraaij, Henk SpekreijseAbstract:1The dynamic properties of the microcircuitry formed by cones and horizontal cells in the isolated goldfish retina were studied. Cones project to horizontal cells and horizontal cells feed back to cones via a relatively slow negative Feedback pathway. 2The time constant of the Feedback Signal in cones and of the effect this Feedback Signal had on the responses of second-order neurons was determined using whole-cell patch clamp and intracellular recording techniques. 3It was found that the Feedback Signal in cones had a time constant of around 80 ms, whereas the time constant of the effect this Feedback Signal had on the second-order neurons ranged from 36 to 116 ms. This range of time constants can be accounted for by the non-linearity of the Ca2+ current in the cones. In depolarized cones, the Feedback-mediated response in second-order neurons had a similar time constant to that of the direct light response of the cone, whereas in hyperpolarized cones, the time constant of the Feedback-mediated response in second-order neurons was considerably larger. 4Further, it was shown that there was no delay in the Feedback pathway. This is in contrast to what has been deduced from the response properties of second-order neurons. In one type of horizontal cell, the responses to red light were delayed relative to the responses to green light. This delay in the second-order neurons can be accounted for by the interaction of the direct light response of the medium-wavelength-sensitive cones (M-cones) with the Feedback response of the M-cones received from the horizontal cells.
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spectral sensitivity of the Feedback Signal from horizontal cells to cones in goldfish retina
Visual Neuroscience, 1998Co-Authors: Dick Kraaij, Maarten Kamermans, Henk SpekreijseAbstract:The spectral sensitivity of cones in isolated goldfish retina was determined with whole-cell recording techniques. Three spectral classes of cones were found with maximal sensitivities around 620 nm, 540 nm, and 460 nm. UV-cones were not found because our stimulator did not allow effective stimulation in the UV range. The spectral sensitivity of the cones closely matched the cone photopigment absorption spectra at the long wavelength side of the spectrum, but deviated significantly at shorter wavelengths. Surround stimulation induced an inward current in cones due to Feedback from horizontal cells. The spectral sensitivity of this Feedback Signal was determined in all three cone classes and found to be broader than the spectral sensitivity of the cones recorded from, and to be spectrally nonopponent. These data are consistent with a connectivity scheme between cones and horizontal cells in which the three horizontal cell systems feed back to all cone systems and in which all horizontal cell systems receive input from more than one cone system.
Dick Kraaij - One of the best experts on this subject based on the ideXlab platform.
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the dynamic characteristics of the Feedback Signal from horizontal cells to cones in the goldfish retina
The Journal of Physiology, 2001Co-Authors: Maarten Kamermans, Dick Kraaij, Henk SpekreijseAbstract:1The dynamic properties of the microcircuitry formed by cones and horizontal cells in the isolated goldfish retina were studied. Cones project to horizontal cells and horizontal cells feed back to cones via a relatively slow negative Feedback pathway. 2The time constant of the Feedback Signal in cones and of the effect this Feedback Signal had on the responses of second-order neurons was determined using whole-cell patch clamp and intracellular recording techniques. 3It was found that the Feedback Signal in cones had a time constant of around 80 ms, whereas the time constant of the effect this Feedback Signal had on the second-order neurons ranged from 36 to 116 ms. This range of time constants can be accounted for by the non-linearity of the Ca2+ current in the cones. In depolarized cones, the Feedback-mediated response in second-order neurons had a similar time constant to that of the direct light response of the cone, whereas in hyperpolarized cones, the time constant of the Feedback-mediated response in second-order neurons was considerably larger. 4Further, it was shown that there was no delay in the Feedback pathway. This is in contrast to what has been deduced from the response properties of second-order neurons. In one type of horizontal cell, the responses to red light were delayed relative to the responses to green light. This delay in the second-order neurons can be accounted for by the interaction of the direct light response of the medium-wavelength-sensitive cones (M-cones) with the Feedback response of the M-cones received from the horizontal cells.
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spectral sensitivity of the Feedback Signal from horizontal cells to cones in goldfish retina
Visual Neuroscience, 1998Co-Authors: Dick Kraaij, Maarten Kamermans, Henk SpekreijseAbstract:The spectral sensitivity of cones in isolated goldfish retina was determined with whole-cell recording techniques. Three spectral classes of cones were found with maximal sensitivities around 620 nm, 540 nm, and 460 nm. UV-cones were not found because our stimulator did not allow effective stimulation in the UV range. The spectral sensitivity of the cones closely matched the cone photopigment absorption spectra at the long wavelength side of the spectrum, but deviated significantly at shorter wavelengths. Surround stimulation induced an inward current in cones due to Feedback from horizontal cells. The spectral sensitivity of this Feedback Signal was determined in all three cone classes and found to be broader than the spectral sensitivity of the cones recorded from, and to be spectrally nonopponent. These data are consistent with a connectivity scheme between cones and horizontal cells in which the three horizontal cell systems feed back to all cone systems and in which all horizontal cell systems receive input from more than one cone system.
