Direction-Selective Neurons in the Optokinetic System With Long-Lasting After-Responses

2002 ◽  
Vol 88 (5) ◽  
pp. 2224-2231 ◽  
Author(s):  
Nicholas S. C. Price ◽  
Michael R. Ibbotson
Keyword(s):  
Temporal Frequency ◽  
Optic Tract ◽  
Movement Control ◽  
Oscillatory Behavior ◽  
Head Movements ◽  
Functional Roles ◽  
Preferred Direction ◽  
Spatial Frequencies ◽  
Pretectal Nucleus ◽  
Motion Detectors

We describe the responses during and after motion of slow cells, which are a class of direction-selective neurons in the pretectal nucleus of the optic tract (NOT) of the wallaby. Neurons in the NOT respond to optic flow generated by head movements and drive compensatory optokinetic eye movements. Motion in the preferred direction produces increased firing rates in the cells, whereas motion in the opposite direction inhibits their high spontaneous activities. Neurons were stimulated with moving spatial sinusoidal gratings through a range of temporal and spatial frequencies. The slow cells were maximally stimulated at temporal frequencies <1 Hz and spatial frequencies of 0.13–1 cpd. During motion, the responses oscillate at the fundamental temporal frequency of the grating but not at higher-order harmonics. There is prolonged excitation after preferred direction motion and prolonged inhibition after anti-preferred direction motion, which are referred to as same-sign after-responses (SSARs). This is the first time that the response properties of neurons with SSARs have been reported and modeled in detail for neurons in the NOT. Slow cell responses during and after motion are modeled using an array of Reichardt-type motion detectors that include band-pass temporal prefilters. The oscillatory behavior during motion and the SSARs can be simulated accurately with the model by manipulating time constants associated with temporal filtering in the prefilters and motion detectors. The SSARs of slow cells are compared with those of previously described direction-selective neurons, which usually show transient inhibition or excitation after preferred or anti-preferred direction motion, respectively. Possible functional roles for slow cells are discussed in the context of eye movement control.

An adaptive Reichardt detector model of motion adaptation in insects and mammals

1997 ◽  
Vol 14 (4) ◽  
pp. 741-749 ◽  
Author(s):  
Colin W.G. Clifford ◽  
Michael R. Ibbotson ◽  
Keith Langley
Keyword(s):  
Dynamic Range ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Optic Tract ◽  
Intrinsic Property ◽  
Wide Field ◽  
Motion Adaptation ◽  
Motion Sensitivity ◽  
Differential Motion ◽  
Motion Detectors

AbstractThere are marked similarities in the adaptation to motion observed in wide-field directional neurons found in the mammalian nucleus of the optic tract and cells in the insect lobula plate. However, while the form and time scale of adaptation is comparable in the two systems, there is a difference in the directional properties of the effect. A model based on the Reichardt detector is proposed to describe adaptation in mammals and insects, with only minor modifications required to account for the differences in directionality. Temporal-frequency response functions of the neurons and the model are shifted laterally and compressed by motion adaptation. The lateral shift enhances dynamic range and differential motion sensitivity. The compression is not caused by fatigue, but is an intrinsic property of the adaptive process resulting from interdependence of temporal-frequency tuning and gain in the temporal filters of the motion detectors.

Visual receptive field properties in kitten pretectal nucleus of the optic tract and dorsal terminal nucleus of the accessory optic tract

1993 ◽  
Vol 70 (2) ◽  
pp. 814-827 ◽  
Author(s):  
C. Distler ◽  
K. P. Hoffmann
Keyword(s):  
Discharge Rate ◽  
Age Groups ◽  
Optic Tract ◽  
Visual Response ◽  
Stimulus Movement ◽  
Cortical Input ◽  
Preferred Direction ◽  
Pretectal Nucleus ◽  
Adult Cats ◽  
Contralateral Eye

1. Neurons in the pretectal nucleus of the optic tract (NOT) and dorsal terminal nucleus of the accessory optic tract (DTN) were recorded in anesthetized and paralyzed kittens on postnatal days 18 to 48 (P18-P48) as well as in adult cats. 2. Spontaneous as well as stimulus driven discharge rates of NOT-DTN neurons in the youngest kittens (P18-P23) are significantly lower than in older kittens (P27-P33) or adult cats. 3. Visual latencies of NOT-DTN neurons in P18-P23 kittens are significantly longer than in P27-P33 kittens. They further decrease as the animals reach adulthood. 4. Already in the youngest animals recorded in this experimental series (P18) NOT-DTN neurons were selective for ipsiversive horizontal stimulus movement. When expressed as the difference between response strength during stimulation in the preferred and the nonpreferred direction, P18-P23 NOT-DTN neurons are less direction selective than NOT-DTN cells in older animals. However, the normalized directional tuning expressed as percent change in discharge rate per degree change in stimulus direction away from the preferred direction (where discharge rate is set 100%) is about equal in all age groups. 5. NOT-DTN neurons in P18-P23 kittens respond to a rather limited range of stimulus speeds with an optimum at approximately 10 degrees/s. In P27-P33 kittens, NOT-DTN neurons increase their responsive range to higher stimulus speeds. As the animals approach adulthood, the range of effective stimulus speeds further broadens to include very low ones. 6. In P18-P23 kittens, the majority of NOT-DTN neurons is exclusively activated by the contralateral eye; only a few neurons receive an additional input from the ipsilateral eye. In P27-P48 kittens, the influence of the ipsilateral eye has significantly increased but with the majority of NOT-DTN cells still being dominated by the contralateral eye. Finally, in adults, a further strengthening of the ipsilateral input leads to a more binocularly balanced input to NOT-DTN cells. 7. Electrical stimulation in areas 17 and 18 did not elicit orthodromic action potentials in NOT-DTN neurons before P27. Thus the cortical input to the NOT-DTN in kittens becomes functional only at 4 wk of age. 8. In conclusion, the significant changes of visual response properties of NOT-DTN neurons coincide with the time when the cortical input to the NOT-DTN becomes functional.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Spatiotemporal Properties of Fast and Slow Neurons in the Pretectal Nucleus Lentiformis Mesencephali in Pigeons

2000 ◽  
Vol 84 (5) ◽  
pp. 2529-2540 ◽  
Author(s):  
Douglas R. W. Wylie ◽  
Nathan A. Crowder
Keyword(s):  
Temporal Frequency ◽  
Receptive Fields ◽  
Sine Wave ◽  
Accessory Optic System ◽  
Stimulus Velocity ◽  
Preferred Direction ◽  
Pretectal Nucleus ◽  
Contralateral Eye ◽  
Sine Wave Gratings ◽  
Self Motion

Neurons in the pretectal nucleus lentiformis mesencephali (LM) are involved in the analysis of optic flow that results from self-motion. Previous studies have shown that LM neurons have large receptive fields in the contralateral eye, are excited in response to largefield stimuli moving in a particular (preferred) direction, and are inhibited in response to motion in the opposite (anti-preferred) direction. We investigated the responses of LM neurons to sine wave gratings of varying spatial and temporal frequency drifting in the preferred and anti-preferred directions. The LM neurons fell into two categories. “Fast” neurons were maximally excited by gratings of low spatial [0.03–0.25 cycles/° (cpd)] and mid-high temporal frequencies (0.5–16 Hz). “Slow” neurons were maximally excited by gratings of high spatial (0.35–2 cpd) and low-mid temporal frequencies (0.125–2 Hz). Of the slow neurons, all but one preferred forward (temporal to nasal) motion. The fast group included neurons that preferred forward, backward, upward, and downward motion. For most cells (81%), the spatial and temporal frequency that elicited maximal excitation to motion in the preferred direction did not coincide with the spatial and temporal frequency that elicited maximal inhibition to gratings moving in the anti-preferred direction. With respect to motion in the anti-preferred direction, a substantial proportion of the LM neurons (32%) showed bi-directional responses. That is, the spatiotemporal plots contained domains of excitation in addition to the region of inhibition. Neurons tuned to stimulus velocity across different spatial frequency were rare (5%), but some neurons (39%) were tuned to temporal frequency. These results are discussed in relation to previous studies of the responses of neurons in the accessory optic system and pretectum to drifting gratings and other largefield stimuli.

Interactions Between on and off Signals in Directional Motion Detectors Feeding the NOT of the Wallaby

2001 ◽  
Vol 86 (2) ◽  
pp. 997-1005 ◽  
Author(s):  
M. R. Ibbotson ◽  
C.W.G. Clifford
Keyword(s):  
Apparent Motion ◽  
Optic Tract ◽  
Image Motion ◽  
Firing Rates ◽  
Preferred Direction ◽  
Motion Stimulus ◽  
Directional Motion ◽  
Time Courses ◽  
Vertical Bars ◽  
Motion Detectors

An apparent motion stimulus is used to probe the interactions between signals representing brightness increments (on stimuli) and decrements (off stimuli) in the directional motion detectors forming the input to the nucleus of the optic tract (NOT) of the wallaby, Macropus eugenii. Direction-selective NOT neurons increase their firing rates during image motion from temporal-to-nasal over the contralateral eye (preferred direction) and their spontaneous activities are inhibited by motion in the opposite, anti-preferred direction. An apparent motion stimulus, consisting of neighboring vertical bars, where the brightness can be manipulated independently, also produces directional responses. Preferred direction sequences of brightness changes of like polarities (on-onor off-off) produce increased firing rates while sequences of opposite polarities (on-offor off-on) in the same direction produce relatively small excitatory responses or inhibit the spontaneous rate. For apparent motion in the anti-preferred direction, these directional properties are reversed, showing that signals for brightness increments and decrements provide inputs to the same motion detectors. There is no evidence for segregation of motion detectors into those receiving only half-wave rectified inputs. Interactions between on andoff signals utilize the sign of the incoming signals. An array of Reichardt-type motion detectors receiving inputs represented as positive and negative values for on and offstimuli, respectively, are used to simulate the NOT responses. The brightness signals enter band-pass temporal filters prior to motion detection. By altering the time constants of these prefilters, it was possible to accurately simulate the time courses of each cell's responses.

On the elementary mechanism underlying secondary motion processing

1996 ◽  
Vol 351 (1348) ◽  
pp. 1725-1736 ◽  
Keyword(s):  
Temporal Frequency ◽  
Motion Processing ◽  
Local Contrast ◽  
Modulation Function ◽  
Motion Signal ◽  
Spatial Frequencies ◽  
Secondary Motion ◽  
Dot Motion ◽  
Complex Features ◽  
Motion Detectors

The movement of luminance-defined targets can be easily extracted by elementary motion detectors (EMDs) of the correlation type which often are referred to as Reichardt-detectors. In contrast to such ‘primary motion’, in ‘secondary motion’ the moving target is defined by more complex features, like changes in texture, flicker, or local contrast. Such stimulus attributes have to be extracted from the retinal intensity distribution by some nonlinear preprocessing, before they are fed into motion detectors. An intriguing case is the perception of the movement of the motion signal, as is present in theta motion, where an object moves in a different direction than the texture on its surface. A two-layer model of hierarchically organised EMDs has been postulated to account for such motion extraction. Other than for the first layer, the computational nature of the mechanism underlying motion processing in the second layer so far is a matter of speculation, and is therefore characterized here by means of computer simulations and psychophysical experiments. Random dot kinematograms were generated in which sinusoidally m odulated vertical dot motion defined gratings, and coherence thresholds were measured for the direction discrimination of a horizontally travelling modulation function. This was done for a variety of spatial frequencies and speeds of the modulation sinusoid. Thresholds turn out to be lowest not for a particular speed, but for a fixed temporal frequency of the modulation function (about 1 cycle per second), when various combinations of fine and coarse, and fast and slow secondary gratings are tested. This result favours a correlation-type mechanism over a gradient-type scheme which should lead to a speed-optimum independent of spatial frequency.

Adaptation to Visual Motion in Directional Neurons of the Nucleus of the Optic Tract

1998 ◽  
Vol 79 (3) ◽  
pp. 1481-1493 ◽  
Author(s):  
Michael R. Ibbotson ◽  
Colin W. G. Clifford ◽  
Richard F. Mark
Keyword(s):  
Receptive Field ◽  
Spatial Frequency ◽  
Firing Rate ◽  
Visual Motion ◽  
Temporal Frequency ◽  
Optic Tract ◽  
Resolving Power ◽  
Adaptation Period ◽  
Time Constants ◽  
Preferred Direction

Ibbotson, Michael R., Colin W. G. Clifford, and Richard F. Mark. Adaptation to visual motion in directional neurons of the nucleus of the optic tract. J. Neurophysiol. 79: 1481–1493, 1998. Extracellular recordings of action potentials were made from directional neurons in the nucleus of the optic tract (NOT) of the wallaby, Macropus eugenii, while stimulating with moving sine-wave gratings. When a grating was moved at a constant velocity in the preferred direction through a neuron's receptive field, the firing rate increased rapidly and then declined exponentially until reaching a steady-state level. The decline in response is called motion adaptation. The rate of adaptation increased as the temporal frequency of the drifting grating increased, up to the frequency that elicited the maximum firing rate. Beyond this frequency, the adaptation rate decreased. When the adapting grating's spatial frequency was varied, such that response magnitudes were significantly different, the maximum adaptation rate occurred at similar temporal frequencies. Hence the temporal frequency of the stimulus is a major parameter controlling the rate of adaptation. In most neurons, the temporal frequency response functions measured after adaptation were shifted to the right when compared with those obtained in the unadapted state. Further insight into the adaptation process was obtained by measuring the responses of the cells to grating displacements within one frame (10.23 ms). Such impulsive stimulus movements of less than a one-quarter cycle elicited a response that rose rapidly to a maximum and then declined exponentially to the spontaneous firing rate in several seconds. The level of adaptation was demonstrated by observing how the time constants of the exponentials varied as a function of the temporal frequency of a previously presented moving grating. When plotted as functions of adapting frequency, time constants formed a U-shaped curve. The shortest time constants occurred at similar temporal frequencies, regardless of changes in spatial frequency, even when the change in spatial frequency resulted in large differences in response magnitude during the adaptation period. The strongest adaptation occurred when the adapting stimulus moved in the neuron's preferred direction. Stimuli that moved in the antipreferred direction or flickered had an adapting influence on the responses to subsequent impulsive movements, but the effect was far smaller than that elicited by preferred direction adaptation. Adaptation in one region of the receptive field did not affect the responses elicited by subsequent stimulation in nonoverlapping regions of the field. Adaptation is a significant property of NOT neurons and probably acts to expand their temporal resolving power.

The Role of Reafference in Recalibration of Limb Movement Control and Locomotion

1997 ◽  
Vol 7 (4) ◽  
pp. 303-310
Author(s):  
James R. Lackner ◽  
Paul DiZio
Keyword(s):  
Movement Control ◽  
Mirror Image ◽  
The Body ◽  
Head Movements ◽  
Reaching Movements ◽  
Optomotor Response ◽  
Coriolis Forces ◽  
Effects Of Rotation ◽  
Centripetal Forces

The reafference model has frequently been used to explain spatial constancy during eye and head movements. We have found that its basic concepts also form part of the information processing necessary for the control and recalibration of reaching movements. Reaching was studied in a novel force environment–a rotating room that creates centripetal forces of the type that could someday substitute for gravity in space flight, and Coriolis forces which are side effects of rotation. We found that inertial, noncontacting Coriolis forces deviate the path and endpoint of reaching movements, a finding that shows the inadequacy of equilibrium position models of movement control. Repeated movements in the rotating room quickly lead to normal movement patterns and to a failure to perceive the perturbing forces. The first movements made after rotation stops, without Coriolis forces present, show mirror-image deviations and evoke perception of a perturbing force even though none is present. These patterns of sensorimotor control and adaptation can largely be explained on the basis of comparisons of efference copy, reafferent muscle spindle, and cutaneous mechanoreceptor signals. We also describe experiments on human iocomotion using an apparatus similar to that which Mittelstaedt used to study the optomotor response of the Eristalis fly. These results show that the reafference principle relates as well to the perception of the forces acting on and exerted by the body during voluntary locomotion.

Evidence for a supplementary eye field

1987 ◽  
Vol 57 (1) ◽  
pp. 179-200 ◽  
Author(s):  
J. Schlag ◽  
M. Schlag-Rey
Keyword(s):  
Unit Activity ◽  
Cortical Neurons ◽  
Cortical Area ◽  
Head Movements ◽  
Frontal Eye Field ◽  
Unit Recording ◽  
Electrical Microstimulation ◽  
Preferred Direction ◽  
Supplementary Eye Field ◽  
Eye Field

Electrical microstimulation and unit recording were performed in dorsomedial frontal cortex of four alert monkeys to identify an oculomotor area whose existence had been postulated rostral to the supplementary motor area. Contraversive saccades were evoked from 129 sites by stimulation. Threshold currents were lower than 20 microA in half the tests. Response latencies were usually longer than 50 ms (minimum: 30 ms). Eye movements were occasionally accompanied by blinks, ear, or neck movements. The cortical area yielding these movements was at the superior edge of the frontal lobe just rostral to the region from which limb movements could be elicited. Depending on the site of stimulation, saccades varied between two extremes: from having rather uniform direction and size, to converging toward a goal defined in space. The transition between these extremes was gradual with no evidence that these two types were fundamentally different. From surface to depth of cortex, direction and amplitude of evoked saccades were similar or changed progressively. No clear systematization was found depending on location along rostrocaudal or mediolateral axes of the cortex. The dorsomedial oculomotor area mapped was approximately 7 mm long and 6 mm wide. Combined eye and head movements were elicited from one of ten sites stimulated when the head was unrestrained. In the other nine cases, saccades were not accompanied by head rotation, even when higher currents or longer stimulus trains were applied. Presaccadic unit activity was recorded from 62 cells. Each of these cells had a preferred direction that corresponded to the direction of the movement evoked by local microstimulation. Presaccadic activity occurred with self-initiated as well as visually triggered saccades. It often led self-initiated saccades by more than 300 ms. Recordings made with the head free showed that the firing could not be interpreted as due to attempted head movements. Many dorsomedial cortical neurons responded to photic stimuli, either phasically or tonically. Sustained responses (activation or inhibition) were observed during target fixation. Twenty-one presaccadic units showed tonic changes of activity with fixation. Justification is given for considering the cortical area studied as a supplementary eye field. It shares many common properties with the arcuate frontal eye field. Differences noted in this study include: longer latency of response to electrical stimulation, possibility to evoke saccades converging apparently toward a goal, and long-lead unit activity with spontaneous saccades.

Response Properties of Pretectal Omnidirectional Pause Neurons in the Behaving Primate

1997 ◽  
Vol 77 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Michael J. Mustari ◽  
Albert F. Fuchs ◽  
Milton Pong
Keyword(s):  
Rhesus Monkeys ◽  
Optic Tract ◽  
Complete Darkness ◽  
Response Properties ◽  
Efferent Connections ◽  
Saccade Onset ◽  
Pretectal Nucleus ◽  
Contingent Response ◽  
Catch Up ◽  
Anterior Posterior

Mustari, Michael J., Albert F. Fuchs, and Milton Pong. Response properties of pretectal omnidirectional pause neurons in the behaving primate. J. Neurophysiol. 77: 116–125, 1997. We have identified a region in the pretectum of rhesus monkeys ( Macaca mulatta) that contains units that evince a complete cessation in firing immediately after saccades. The pause occurs for saccades to target steps and catch up saccades during smooth pursuit, spontaneously in complete darkness or after quick phases of nystagmus. Because the pause in unit firing always follows saccade onset, we call these neurons following omnidirectional pause neurons (FOPNs). Because the pause also occurs with saccades in the dark, it is related to the saccade per se and is not a visually contingent response. The duration of the pause in firing exceeded the duration of all saccades up to 40 deg. For targeting saccades, the start of the pause was locked rather tightly to the beginning of the saccade but began an average of 51 ms after the saccade did. The end of the pause was linked only loosely to either the beginning or end of the saccade. About half (54%) of our 59 FOPNs also discharged a distinct burst of firing that preceded the pause. In different units, the burst preceded saccade onset by from 0 to 20 ms with an average of 11 ms and therefore could signal the occurrence of an impending saccade. The presaccadic burst was not correlated with any parameter of the saccade. Most FOPNs were found 278 μm, on average, dorsal to the direction-selective units characteristic of the pretectal nucleus of the optic tract (NOT) and occasionally slightly beyond the anterior-posterior and medial-lateral borders of the NOT. The FOPN region does not coincide with any known anatomically or functionally delineated pretectal nucleus. Because the characteristics of the FOPN pause are not reflected in the characteristics of the saccade and the FOPN pause occurs well after the saccade is over, it is unlikely that the pause in pretectal FOPNs is involved with saccade generation. On the other hand, the leading burst exhibited by the majority of FOPNs reliably signals that a saccade is occurring but neither its size nor direction. Perhaps this signal indicating the occurrence of all saccades is routed to visual relay neurons to effect saccadic modification of visual pathways. The substantial efferent connections of the FOPN/NOT region to the pregeniculate nucleus and the saccadic discharge of pregeniculate cells are discussed in the context of this suggestion.

Temporal and Spatial Frequency Tuning of the Flicker Motion Aftereffect

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 12-12
Author(s):  
P J Bex ◽  
F A J Verstraten ◽  
I Mareschal
Keyword(s):  
Spatial Frequency ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Motion Aftereffect ◽  
Sine Wave ◽  
Test Grating ◽  
Spatial Frequency Tuning ◽  
Spatial Frequencies ◽  
Low Pass ◽  
Sine Wave Gratings

The motion aftereffect (MAE) was used to study the temporal-frequency and spatial-frequency selectivity of the visual system at suprathreshold contrasts. Observers adapted to drifting sine-wave gratings of a range of spatial and temporal frequencies. The magnitude of the MAE induced by the adaptation was measured with counterphasing test gratings of a variety of spatial and temporal frequencies. Independently of the spatial or temporal frequency of the adapting grating, the largest MAE was found with slowly counterphasing test gratings (∼0.125 – 0.25 Hz). For slowly counterphasing test gratings (<∼2 Hz), the largest MAEs were found when the test grating was of similar spatial frequency to that of the adapting grating, even at very low spatial frequencies (0.125 cycle deg−1). However, such narrow spatial frequency tuning was lost when the temporal frequency of the test grating was increased. The data suggest that MAEs are dominated by a single, low-pass temporal-frequency mechanism and by a series of band-pass spatial-frequency mechanisms at low temporal frequencies. At higher test temporal frequencies, the loss of spatial-frequency tuning implicates separate mechanisms with broader spatial frequency tuning.

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