scholarly journals Cues to move increase information in superior colliculus tuning curves

2011 ◽  
Vol 106 (2) ◽  
pp. 690-703 ◽  
Author(s):  
Xiaobing Li ◽  
Michele A. Basso
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Tuning Curve ◽  
Discharge Rate ◽  
Saccadic Eye Movements ◽  
Theoretical Work ◽  
Sensory Stimuli ◽  
Tuning Curves ◽  
Sensory Responses ◽  
And Shifts

Shifts in the location of spatial attention produce increases in the gain and sensitivity of neuronal responses to sensory stimuli. Cues to shift the line of sight have the same effect on sensory responses in a motor area involved in the control of eye movements, the superior colliculus. Evidence has shown that shifts of gaze and shifts of attention are linked, suggesting there may be similar underlying mechanisms. Here, we report on a novel way in which cues to move the eyes (top-down signals) can influence sensory responses of neurons by altering the variability of their discharge rate. We measured the spatial tuning of superior colliculus neuronal activity in trials with cues to either make or withhold saccadic eye movements. We found that tuning curve widths both increased and decreased, but that the information conveyed by the neuronal discharge about the stimulus increased with a cue to make a saccade. The increase in information resulted partly from a decrease in trial-to-trial variability of neuronal discharges for stimuli located at the flanks of the tuning curves rather than from increases in the discharge rate for stimuli located at the peak of the tuning curves. This result is consistent with theoretical work and provides a novel way for cognitive signals to influence sensory responses within motor regions of the brain.

Discharge Properties of Neurons in the Rostral Superior Colliculus of the Monkey During Smooth-Pursuit Eye Movements

2000 ◽  
Vol 84 (2) ◽  
pp. 876-891 ◽  
Author(s):  
Richard J. Krauzlis ◽  
Michele A. Basso ◽  
Robert H. Wurtz
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Smooth Pursuit ◽  
Discharge Rate ◽  
Motor Command ◽  
Contralateral Side ◽  
Position Error ◽  
Related Activity ◽  
Tuning Curves ◽  
Pursuit Eye Movements

The intermediate and deep layers of the monkey superior colliculus (SC) comprise a retinotopically organized map for eye movements. The rostral end of this map, corresponding to the representation of the fovea, contains neurons that have been referred to as “fixation cells” because they discharge tonically during active fixation and pause during the generation of most saccades. These neurons also possess movement fields and are most active for targets close to the fixation point. Because the parafoveal locations encoded by these neurons are also important for guiding pursuit eye movements, we studied these neurons in two monkeys as they generated smooth pursuit. We found that fixation cells exhibit the same directional preferences during pursuit as during small saccades—they increase their discharge during movements toward the contralateral side and decrease their discharge during movements toward the ipsilateral side. This pursuit-related activity could be observed during saccade-free pursuit and was not predictive of small saccades that often accompanied pursuit. When we plotted the discharge rate from individual neurons during pursuit as a function of the position error associated with the moving target, we found tuning curves with peaks within a few degrees contralateral of the fovea. We compared these pursuit-related tuning curves from each neuron to the tuning curves for a saccade task from which we separately measured the visual, delay, and peri-saccadic activity. We found the highest and most consistent correlation with the delay activity recorded while the monkey viewed parafoveal stimuli during fixation. The directional preferences exhibited during pursuit can therefore be attributed to the tuning of these neurons for contralateral locations near the fovea. These results support the idea that fixation cells are the rostral extension of the buildup neurons found in the more caudal colliculus and that their activity conveys information about the size of the mismatch between a parafoveal stimulus and the currently foveated location. Because the generation of pursuit requires a break from fixation, the pursuit-related activity indicates that these neurons are not strictly involved with maintaining fixation. Conversely, because activity during the delay period was found for many neurons even when no eye movement was made, these neurons are also not obligatorily related to the generation of a movement. Thus the tonic activity of these rostral neurons provides a potential position-error signal rather than a motor command—a principle that may be applicable to buildup neurons elsewhere in the SC.

Sensorimotor integration in the primate superior colliculus. I. Motor convergence

1987 ◽  
Vol 57 (1) ◽  
pp. 22-34 ◽  
Author(s):  
M. F. Jay ◽  
D. L. Sparks
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Visual Stimuli ◽  
Saccadic Eye Movements ◽  
Visual Signals ◽  
M Cells ◽  
Efferent Pathway ◽  
Saccadic Velocity ◽  
Visual Targets ◽  
Sensory Responses

Orienting movements of the eyes and head are made to both auditory and visual stimuli even though in the primary sensory pathways the locations of auditory and visual stimuli are encoded in different coordinates. This study was designed to differentiate between two possible mechanisms for sensory-to-motor transformation. Auditory and visual signals could be translated into common coordinates in order to share a single motor pathway or they could maintain anatomically separate sensory and motor routes for the initiation and guidance of orienting eye movements. The primary purpose of the study was to determine whether neurons in the superior colliculus (SC) that discharge before saccades to visual targets also discharge before saccades directed toward auditory targets. If they do, this would indicate that auditory and visual signals, originally encoded in different coordinates, have been converted into a single coordinate system and are sharing a motor circuit. Trained monkeys made saccadic eye movements to auditory or visual targets while the activity of visual-motor (V-M) cells and saccade-related burst (SRB) cells was monitored. The pattern of spike activity observed during trials in which saccades were made to visual targets was compared with that observed when comparable saccades were made to auditory targets. For most (57 of 59) V-M cells, sensory responses were observed only on visual trials. Auditory stimuli originating from the same region of space did not activate these cells. Yet, of the 72 V-M and SRB cells studied, 79% showed motor bursts prior to saccades to either auditory or visual targets. This finding indicates that visual and auditory signals, originally encoded in retinal and head-centered coordinates, respectively, have undergone a transformation that allows them to share a common efferent pathway for the generation of saccadic eye movements. Saccades to auditory targets usually have lower velocities than saccades of the same amplitude and direction made to acquire visual targets. Since fewer collicular cells are active prior to saccades to auditory targets, one determinant of saccadic velocity may be the number of collicular neurons discharging before a particular saccade.

Saccade-related neurons in cat superior colliculus: pandirectional movement cells with postsaccadic responses

1984 ◽  
Vol 52 (6) ◽  
pp. 1154-1168 ◽  
Author(s):  
C. K. Peck
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Eye Movement ◽  
Visual Stimulation ◽  
Discharge Rate ◽  
Abrupt Onset ◽  
Corollary Discharge ◽  
Temporal Association ◽  
Modular Organization ◽  
Sensory Stimuli

The superior colliculus is known to contain cells discharging before saccadic eye movements as well as cells responding to sensory stimuli. In this study extracellular single unit recordings were made in the alert trained cat with the head fixed. A novel type of eye movement-related response was found in 9% (32/344) of the cells recorded. These cells differ from previously reported eye movement-related neurons in the timing of their discharge, which accompanies but does not precede saccades. The timing of discharge varies across units from less than 10 ms after the onset of eye movement to as much as 80 ms. Comparable latencies were found regardless of whether saccades were directed contralateral or ipsilateral to the recording site. Most units have an abrupt onset of discharge, but some show a very gradual increase in discharge rate. Most cells (69% or 22/32) discharged with equal vigor for all saccades, regardless of direction. The remainder tended to show higher-frequency bursts when saccades were directed contralaterally, but even these units were not encoding saccade direction by their pattern of discharge. Thus the discharge pattern could be summarized as an omnidirectional burst. For the vast majority of cells (81% or 26/32) the duration of discharge did not correlate with the duration of eye movement. The same pattern of firing was seen with saccades in light and in complete darkness. Thus the saccade-related discharge was not due to changes in visual stimulation during saccades. A minority of the units (15% or 5 of 32) that discharged with but not before saccades also responded to visual stimuli in the absence of eye movements. Saccade-related activity was dependent on alertness of the cat, as measured by behavioral performance and EEG. The close temporal association between saccades and unit discharge disappeared during drowsiness. These units could be reflecting either proprioceptive or corollary discharge signals to the superior colliculus. However, their response properties differ somewhat from those found in previous studies of proprioceptive inputs to the colliculus. Such differences could be due to the effects of the anesthetics that were used in studies of proprioceptive responses. Alternatively, the cells reported here could be conveying a corollary discharge signal. These cells occurred in patches or clusters. This is consistent with a wealth of anatomic data indicating a modular organization of the colliculus.

scholarly journals A test of spatial temporal decoding mechanisms in the superior colliculus

2012 ◽  
Vol 107 (9) ◽  
pp. 2442-2452 ◽  
Author(s):  
Husam A. Katnani ◽  
A. J. Van Opstal ◽  
Neeraj J. Gandhi
Keyword(s):  
Nervous System ◽  
Motor Control ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Motor Behavior ◽  
Saccadic Eye Movements ◽  
Population Coding ◽  
Population Activity ◽  
Low Levels

Population coding is a ubiquitous principle in the nervous system for the proper control of motor behavior. A significant amount of research is dedicated to studying population activity in the superior colliculus (SC) to investigate the motor control of saccadic eye movements. Vector summation with saturation (VSS) has been proposed as a mechanism for how population activity in the SC can be decoded to generate saccades. Interestingly, the model produces different predictions when decoding two simultaneous populations at high vs. low levels of activity. We tested these predictions by generating two simultaneous populations in the SC with high or low levels of dual microstimulation. We also combined varying levels of stimulation with visually induced activity. We found that our results did not perfectly conform to the predictions of the VSS scheme and conclude that the simplest implementation of the model is incomplete. We propose that additional parameters to the model might account for the results of this investigation.

scholarly journals Statistical assessment of the stability of neural movement representations

2011 ◽  
Vol 106 (2) ◽  
pp. 764-774 ◽  
Author(s):  
Ian H. Stevenson ◽  
Anil Cherian ◽  
Brian M. London ◽  
Nicholas A. Sachs ◽  
Eric Lindberg ◽  
...  
Keyword(s):  
Primary Motor Cortex ◽  
Tuning Curve ◽  
Modulation Depth ◽  
Measurement Noise ◽  
Neural Representation ◽  
Experimental Conditions ◽  
Sensory Stimuli ◽  
Tuning Curves ◽  
Dynamic Tuning ◽  
Preferred Direction

In systems neuroscience, neural activity that represents movements or sensory stimuli is often characterized by spatial tuning curves that may change in response to training, attention, altered mechanics, or the passage of time. A vital step in determining whether tuning curves change is accounting for estimation uncertainty due to measurement noise. In this study, we address the issue of tuning curve stability using methods that take uncertainty directly into account. We analyze data recorded from neurons in primary motor cortex using chronically implanted, multielectrode arrays in four monkeys performing center-out reaching. With the use of simulations, we demonstrate that under typical experimental conditions, the effect of neuronal noise on estimated preferred direction can be quite large and is affected by both the amount of data and the modulation depth of the neurons. In experimental data, we find that after taking uncertainty into account using bootstrapping techniques, the majority of neurons appears to be very stable on a timescale of minutes to hours. Lastly, we introduce adaptive filtering methods to explicitly model dynamic tuning curves. In contrast to several previous findings suggesting that tuning curves may be in constant flux, we conclude that the neural representation of limb movement is, on average, quite stable and that impressions to the contrary may be largely the result of measurement noise.

Distributed spatial coding in the superior colliculus: A review

1991 ◽  
Vol 6 (1) ◽  
pp. 3-13 ◽  
Author(s):  
James T. McIlwain
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Receptive Fields ◽  
Saccadic Eye Movements ◽  
Visual Direction ◽  
Saccade Amplitude ◽  
Spatial Coding ◽  
Distributed Coding

AbstractThis paper reviews evidence that the superior colliculus (SC) of the midbrain represents visual direction and certain aspects of saccadic eye movements in the distribution of activity across a population of cells. Accurate and precise eye movements appear to be mediated, in part at least, by cells of the SC that have large sensory receptive fields and/or discharge in association with a range of saccades. This implies that visual points or saccade targets are represented by patches rather than points of activity in the SC. Perturbation of the pattern of collicular discharge by focal inactivation modifies saccade amplitude and direction in a way consistent with distributed coding. Several models have been advanced to explain how such a code might be implemented in the colliculus. Evidence related to these hypotheses is examined and continuing uncertainties are identified.

scholarly journals Normal correspondence of tectal maps for saccadic eye movements in strabismus

2016 ◽  
Vol 116 (6) ◽  
pp. 2541-2549 ◽  
Author(s):  
John R. Economides ◽  
Daniel L. Adams ◽  
Jonathan C. Horton
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Superior Colliculus ◽  
Saccadic Eye Movements ◽  
Systematic Change ◽  
Free Viewing ◽  
Pattern Deviation ◽  
Ocular Deviation ◽  
The Right ◽  
Stem Structure

The superior colliculus is a major brain stem structure for the production of saccadic eye movements. Electrical stimulation at any given point in the motor map generates saccades of defined amplitude and direction. It is unknown how this saccade map is affected by strabismus. Three macaques were raised with exotropia, an outwards ocular deviation, by detaching the medial rectus tendon in each eye at age 1 mo. The animals were able to make saccades to targets with either eye and appeared to alternate fixation freely. To probe the organization of the superior colliculus, microstimulation was applied at multiple sites, with the animals either free-viewing or fixating a target. On average, microstimulation drove nearly conjugate saccades, similar in both amplitude and direction but separated by the ocular deviation. Two monkeys showed a pattern deviation, characterized by a systematic change in the relative position of the two eyes with certain changes in gaze angle. These animals' saccades were slightly different for the right eye and left eye in their amplitude or direction. The differences were consistent with the animals' underlying pattern deviation, measured during static fixation and smooth pursuit. The tectal map for saccade generation appears to be normal in strabismus, but saccades may be affected by changes in the strabismic deviation that occur with different gaze angles.

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