Activity Changes in Monkey Superior Colliculus During Saccade Adaptation

2007 ◽  
Vol 97 (6) ◽  
pp. 4096-4107 ◽  
Author(s):  
Norihito Takeichi ◽  
Chris R. S. Kaneko ◽  
Albert F. Fuchs
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Brain Stem ◽  
Neuronal Activity ◽  
Great Majority ◽  
Behavioral Adaptation ◽  
Saccade Amplitude ◽  
Common Pathway ◽  
Movement Field ◽  
Saccade Adaptation

Saccades are eye movements that are used to foveate targets rapidly and accurately. Their amplitude must be adjusted continually, throughout life, to compensate for movement inaccuracies due to maturation, pathology, or aging. One possible locus for such saccade adaptation is the superior colliculus (SC), the relay for cortical commands to the premotor brain stem generator for saccades. However, previous stimulation and recording studies have disagreed as to whether saccade adaptation occurs up- or downstream of the SC. Therefore we have reexamined the behavior of SC burst neurons during saccade adaptation under conditions that were optimized to produce the biggest possible change in neuronal activity. We show that behavioral adaptation of saccade amplitude was associated with significant increases or decreases, in the number of spikes in the burst and/or changes in the shape of the movement field in 35 of 43 SC neurons tested. Of the 35, 29 had closed movement fields and 14 were classified indeterminate because the movement field could not be definitively diagnosed. Changes in the number of spikes occurred gradually during adaptation and resulted from correlated changes in burst lead and duration without consistent changes in peak burst rate. These data indicate that the great majority of SC neurons show a change in discharge in association with saccade amplitude adaptation. Based on these and previous results, we speculate that the site for saccade adaptation resides in the SC or that the SC is the final common pathway for adaptive changes that occur elsewhere in the saccade system.

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.

Single neurons in posterior cingulate cortex of behaving macaque: eye movement signals

1996 ◽  
Vol 76 (5) ◽  
pp. 3285-3300 ◽  
Author(s):  
C. R. Olson ◽  
S. Y. Musil ◽  
M. E. Goldberg
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
Neuronal Activity ◽  
Cingulate Cortex ◽  
Posterior Cingulate Cortex ◽  
Amplitude Dependence ◽  
Saccade Amplitude ◽  
Posterior Cingulate ◽  
Level Of Activity ◽  
Saccade Direction

1. Posterior cingulate cortex, although widely regarded as a part of the limbic system, is connected most strongly to parietal and frontal areas with sensory, motor, and cognitive functions. To gain insight into the functional nature of posterior cingulate cortex, we have recorded from its neurons in monkeys performing oculomotor tasks known to activate parietal and frontal neurons. We have found that posterior cingulate neurons fire during periods of ocular fixation at a rate determined by the angle of gaze and by the size and direction of the preceding eye movement. 2. The activity of 530 posterior cingulate neurons was monitored while rhesus macaque monkeys made visually guided eye movements to spots projected on a tangent screen. 3. In 150/530 neurons, a statistically significant shift in the rate of discharge occurred around the time of onset of saccadic eye movements. The preponderant form of response was an increase in activity (142/150 neurons). 4. In 142 neurons exhibiting significant excitation after saccades in at least one direction, the level of discharge was analyzed as a function of time relative to onset of the saccade. Across the neuronal population as a whole, activity increased sharply at the moment of onset of the saccade, rising to a maximum after 200 ms and then declining slowly. The net level of discharge remained well above presaccadic baseline even after > 1 s of postsaccadic fixation. 5. In 63 neurons, the postsaccadic rate of discharge was analyzed relative to the angle of the eye in the orbit by monitoring neuronal activity while the monkey executed saccades of uniform direction and amplitude to four targets spaced at 16-deg intervals along a line. The postsaccadic firing level was significantly dependent on orbital angle in 44/63 neurons. 6. In 45 neurons, the postsaccadic rate of discharge was analyzed relative to saccade direction by monitoring neuronal activity while the monkey executed 16-deg saccades to a constant target from diametrically opposed starting points. The postsaccadic level of activity was significantly dependent on saccade direction in 20/ 45 neurons. 7. In 58 neurons, the postsaccadic rate of discharge was analyzed relative to saccade amplitude by monitoring neuronal activity while the monkey executed saccades, which varied in amplitude (4, 8, 16, and 32 deg) but which were constant in direction and brought the eye to bear on a constant endpoint. The postsaccadic level of activity was significantly dependent on saccade amplitude in 24/58 neurons. In all neurons exhibiting significant amplitude-dependence, stronger firing accompanied larger saccades. 8. The activity of 10 neurons was monitored during smooth pursuit eye movements (20 deg/s upward, downward, leftward, and rightward). The level of firing varied as a function of both the position of the eye (9 neurons) and the velocity of the eye (6 neurons). 9. We conclude that posterior cingulate neurons monitor eye movements and eye position. It is unlikely that they participate in the generation of eye movements because their shifts of discharge follow the onset of the movements. Eye-movement-related signals in posterior cingulate cortex may reflect the participation of this area in assigning spatial coordinates to retinal images.

Target Selection for Saccadic Eye Movements: Prelude Activity in the Superior Colliculus During a Direction-Discrimination Task

2001 ◽  
Vol 86 (5) ◽  
pp. 2543-2558 ◽  
Author(s):  
Gregory D. Horwitz ◽  
William T. Newsome
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Discrimination Task ◽  
Target Selection ◽  
Saccadic Eye Movements ◽  
Saccade Target ◽  
Visual Responses ◽  
Direction Discrimination ◽  
Motion Signal ◽  
Movement Field

We investigated the role of the superior colliculus (SC) in saccade target selection while macaque monkeys performed a direction-discrimination task. The monkeys selected one of two possible saccade targets based on the direction of motion in a stochastic random-dot display; the difficulty of the task was varied by adjusting the strength of the motion signal in the display. One of the two saccade targets was positioned within the movement field of the SC neuron under study while the other target was positioned well outside the movement field. Approximately 30% of the neurons in the intermediate and deep layers of the SC discharged target-specific preludes of activity that “predicted” target choices well before execution of the saccadic eye movement. Across the population of neurons, the strength of the motion signal in the display influenced the intensity of this “predictive” prelude activity: SC activity signaled the impending saccade more reliably when the motion signal was strong than when it was weak. The dependence of neural activity on motion strength could not be explained by small variations in the metrics of the saccadic eye movements. Predictive activity was particularly strong in a subpopulation of neurons with directional visual responses that we have described previously. For a subset of SC neurons, therefore, prelude activity reflects the difficulty of the direction discrimination in addition to the target of the impending saccade. These results are consistent with the notion that a restricted network of SC neurons plays a role in the process of saccade target selection.

Modification of saccadic eye movements by GABA-related substances. I. Effect of muscimol and bicuculline in monkey superior colliculus

1985 ◽  
Vol 53 (1) ◽  
pp. 266-291 ◽  
Author(s):  
O. Hikosaka ◽  
R. H. Wurtz
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Injection Site ◽  
Saccadic Eye Movements ◽  
Contralateral Side ◽  
Slow Phase ◽  
Gamma Aminobutyric Acid ◽  
Affected Area ◽  
Related Substances ◽  
Movement Field

Our previous observations led to the hypothesis that cells in the substantia nigra pars reticulata (SNr) tonically inhibit saccade-related cells in the intermediate layers of the superior colliculus (SC). Before saccades to visual or remembered targets, cells in SNr briefly reduce that inhibition, allowing a burst of spikes of SC cells that, in turn, leads to the initiation of a saccadic eye movement. Since this inhibition is likely to be mediated by gamma-aminobutyric acid (GABA), we tested this hypothesis by injecting a GABA agonist (muscimol) or a GABA antagonist (bicuculline) into the superior colliculus and measured the effects on saccadic eye movements made to visual or remembered targets. An injection of muscimol selectively suppressed saccades to the movement field of the cells near the injection site. The affected area expanded over time, thus suggesting the diffusion of muscimol in the SC; the area never included the other hemifield, suggesting that the diffusion was limited to one SC. One of the monkeys became unable to make any saccades to the affected area. Saccades to visual targets following injection of muscimol had longer latency and slightly shorter amplitudes that were corrected by subsequent saccades. The most striking change was a decrease in the peak velocity of the saccade, frequently to less than half the preinjection value. Saccades to remembered targets following injection of muscimol also showed an increase in latency and decrease in velocity, but in addition, showed a striking decrease in the accuracy of the saccades. The trajectories of saccades became distorted as if they were deflected away from the affected area. After muscimol injection, the area over which spontaneous eye movements were made shifted toward the side ipsilateral to the injection. Saccades toward the contralateral side were less frequent and slower. In nystagmus, which developed later, the slow phase was toward the contralateral side. In contrast to muscimol, injection of bicuculline facilitated the initiation of saccades. Injection was followed almost immediately by stereotyped and apparently irrepressible saccades made toward the center of the movement field of the SC cells at the injection site. The monkeys became unable to fixate during the tasks; the fixation was interrupted by saccadic jerks made to the affected area of the visual field and then back to the fixation point.(ABSTRACT TRUNCATED AT 400 WORDS)

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