Activity of neurons in monkey superior colliculus during interrupted saccades

1996 ◽  
Vol 75 (6) ◽  
pp. 2562-2580 ◽  
Author(s):  
D. P. Munoz ◽  
D. M. Waitzman ◽  
R. H. Wurtz
Keyword(s):  
Superior Colliculus ◽  
High Frequency ◽  
Time Course ◽  
Main Sequence ◽  
Total Duration ◽  
Low Frequency ◽  
Saccade Target ◽  
Velocity Amplitude ◽  
Burst Neurons ◽  
Frequency Burst

1. Recent studies of the monkey superior colliculus (SC) have identified several types of cells in the intermediate layers (including burst, buildup, and fixation neurons) and the sequence of changes in their activity during the generation of saccadic eye movements. On the basis of these observations, several hypotheses about the organization of the SC leading to saccade generation have placed the SC in a feedback loop controlling the amplitude and direction of the impending saccade. We tested these hypotheses about the organization of the SC by perturbing the system while recording the activity of neurons within the SC. 2. We applied a brief high-frequency train of electrical stimulation among the fixation cells in the rostral pole of the SC. This momentarily interrupted the saccade in midflight: after the initial eye acceleration, the eye velocity decreased (frequently to 0) and then again accelerated. Despite the break in the saccade, these interrupted saccades were of about the same amplitude as normal saccades. The postinterruption saccades were usually initiated immediately after the termination of stimulation and occurred regardless of whether the saccade target was visible or not. The velocity-amplitude relationship of the preinterruption component of the saccade fell slightly above the main sequence for control saccades of that amplitude, whereas postinterruption saccades fell near the main sequence. 3. Collicular burst neurons are silent during fixation and discharge a robust burst of action potentials for saccades to a restricted region of the visual field that define a closed movement field. During the stimulation-induced saccadic interruption, these burst neurons all showed a pause in their high-frequency discharge. During an interrupted saccade to a visual target, the typical saccade-related burst was broken into two parts: the first part of the burst began before the initial preinterruption saccade; the second burst began before the postinterruption saccade. 4. We quantified three aspects of the resumption of activity of burst neurons following saccade interruption: 1) the total number of spikes in the pre- and postinterruption bursts, was very similar to the total number of spikes in the control saccade burst; 2) the increase in total duration of the burst (preinterruption period + interruption + postinterruption period) was highly correlated with the increase in total saccade duration (preinterruption saccade + interruption + postinterruption saccade); and 3) the time course of the postinterruption saccade and the resumed cell discharge both followed the same monotonic trajectory as the control saccade in most cells. 5. The same population of burst neurons was active for both the preinterruption and the postinterruption saccades, provided that the stimulation was brief enough to allow the postinterruption saccade to occur immediately. If the postinterruption saccade was delayed by > 100 ms, then burst neurons at a new and more rostral locus related to such smaller saccades became active in association with the smaller remaining saccade. We interpret this shift in active locations within the SC as a termination of the initial saccadic error command and the triggering of a new one. 6. Buildup neurons usually had two aspects to their discharge: a high-frequency burst for saccades of the optimal amplitude and direction (similar to burst neurons), and a low-frequency discharge for saccades of optimal direction whose amplitudes were equal to or greater than the optimal (different from burst neurons). The stimulation-induced interruption in saccade trajectory differentially affected these two components of buildup neuron discharge. The high-frequency burst component was affected in a manner very similar to the burst neurons.(ABSTRACT TRUNCATED)

Effects of low-frequency stimulation of the superior colliculus on spontaneous and visually guided saccades

1993 ◽  
Vol 69 (3) ◽  
pp. 953-964 ◽  
Author(s):  
P. W. Glimcher ◽  
D. L. Sparks
Keyword(s):  
Superior Colliculus ◽  
Time Course ◽  
Low Frequency ◽  
Arbitrary Point ◽  
Visually Guided ◽  
Spontaneous Movements ◽  
Low Frequency Stimulation ◽  
Frequency Stimulation ◽  
Stimulation Current ◽  
Stimulation Of

1. The first experiment of this study determined the effects of low-frequency stimulation of the monkey superior colliculus on spontaneous saccades in the dark. Stimulation trains, subthreshold for eliciting short-latency fixed-vector saccades, were highly effective at biasing the metrics (direction and amplitude) of spontaneous movements. During low-frequency stimulation, the distribution of saccade metrics was biased toward the direction and amplitude of movements induced by suprathreshold stimulation of the same collicular location. 2. Low-frequency stimulation biased the distribution of saccade metrics but did not initiate movements. The distribution of intervals between stimulation onset and the onset of the next saccade did not differ significantly from the distribution of intervals between an arbitrary point in time and the onset of the next saccade under unstimulated conditions. 3. Results of our second experiment indicate that low-frequency stimulation also influenced the metrics of visually guided saccades. The magnitude of the stimulation-induced bias increased as stimulation current or frequency was increased. 4. The time course of these effects was analyzed by terminating stimulation immediately before, during, or after visually guided saccades. Stimulation trains terminated at the onset of a movement were as effective as stimulation trains that continued throughout the movement. No effects were observed if stimulation ended 40–60 ms before the movement began. 5. These results show that low-frequency collicular stimulation can influence the direction and amplitude of spontaneous or visually guided saccades without initiating a movement. These data are compatible with the hypothesis that the collicular activity responsible for specifying the horizontal and vertical amplitude of a saccade differs from the type of collicular activity that initiates a saccade.

scholarly journals Blink-Perturbed Saccades in Monkey. II. Superior Colliculus Activity

2000 ◽  
Vol 83 (6) ◽  
pp. 3430-3452 ◽  
Author(s):  
H.H.L.M. Goossens ◽  
A. J. Van Opstal
Keyword(s):  
Superior Colliculus ◽  
Firing Rate ◽  
High Frequency ◽  
Displacement Vector ◽  
Neural Mechanism ◽  
Fixed Number ◽  
Deep Layers ◽  
The Mean ◽  
Reflex Blinks ◽  
Frequency Burst

Trigeminal reflex blinks evoked near the onset of a saccade cause profound spatial-temporal perturbations of the saccade that are typically compensated in mid-flight. This paper investigates the influence of reflex blinks on the discharge properties of saccade-related burst neurons (SRBNs) in intermediate and deep layers of the monkey superior colliculus (SC). Twenty-nine SRBNs, recorded in three monkeys, were tested in the blink-perturbation paradigm. We report that the air puff stimuli, used to elicit blinks, resulted in a short-latency (∼10 ms) transient suppression of saccade-related SRBN activity. Shortly after this suppression (within 10–30 ms), all neurons resumed their activity, and their burst discharge then continued until the perturbed saccade ended near the extinguished target. This was found regardless whether the compensatory movement was into the cell's movement field or not. In the limited number of trials where no compensation occurred, the neurons typically stopped firing well before the end of the eye movement. Several aspects of the saccade-related activity could be further quantified for 25 SRBNs. It appeared that 1) the increase in duration of the high-frequency burst was well correlated with the (two- to threefold) increase in duration of the perturbed movement. 2) The number of spikes in the burst for control and perturbed saccades was quite similar. On average, the number of spikes increased only 14%, whereas the mean firing rate in the burst decreased by 52%. 3) An identical number of spikes were obtained between control and perturbed responses when burst and postsaccadic activity were both included in the spike count. 4) The decrease of the mean firing rate in the burst was well correlated with the decrease in the velocity of perturbed saccades. 5) Monotonic relations between instantaneous firing rate and dynamic motor error were obtained for control responses but not for perturbed responses. And 6) the high-frequency burst of SRBNs with short-lead and long-lead presaccadic activity (also referred to as burst and buildup neurons, respectively) showed very similar features. Our findings show that blinking interacts with the saccade premotor system already at the level of the SC. The data also indicate that a neural mechanism, rather than passive elastic restoring forces within the oculomotor plant, underlies the compensation for blink-related perturbations. We propose that these interactions occur downstream from the motor SC and that the latter may encode the desired displacement vector of the eyes by sending an approximately fixed number of spikes to the brainstem saccadic burst generator.

Dissociating early and late visual processing via the Ebbinghaus illusion

2016 ◽  
Vol 33 ◽  
Author(s):  
FILIPP SCHMIDT ◽  
ANDREAS WEBER ◽  
ANKE HABERKAMP
Keyword(s):  
Visual Processing ◽  
High Frequency ◽  
Time Course ◽  
Temporal Dynamics ◽  
Low Frequency ◽  
Response Speed ◽  
Ebbinghaus Illusion ◽  
Priming Effects ◽  
Parvocellular Pathway ◽  
The Difference

AbstractVisual perception is not instantaneous; the perceptual representation of our environment builds up over time. This can strongly affect our responses to visual stimuli. Here, we study the temporal dynamics of visual processing by analyzing the time course of priming effects induced by the well-known Ebbinghaus illusion. In slower responses, Ebbinghaus primes produce effects in accordance with their perceptual appearance. However, in fast responses, these effects are reversed. We argue that this dissociation originates from the difference between early feedforward-mediated gist of the scene processing and later feedback-mediated more elaborate processing. Indeed, our findings are well explained by the differences between low-frequency representations mediated by the fast magnocellular pathway and high-frequency representations mediated by the slower parvocellular pathway. Our results demonstrate the potentially dramatic effect of response speed on the perception of visual illusions specifically and on our actions in response to objects in our visual environment generally.

Saccade-related activity in monkey superior colliculus. I. Characteristics of burst and buildup cells

1995 ◽  
Vol 73 (6) ◽  
pp. 2313-2333 ◽  
Author(s):  
D. P. Munoz ◽  
R. H. Wurtz
Keyword(s):  
Superior Colliculus ◽  
High Frequency ◽  
Low Frequency ◽  
Striking Difference ◽  
Related Activity ◽  
Slow Increase ◽  
High Frequency Discharge ◽  
Optimal Direction ◽  
Saccade Onset ◽  
Increased Activity

1. In the monkey superior colliculus (SC), the activity of most saccade-related neurons studied so far consists of a burst of activity in a population of cells at one place on the SC movement map. In contrast, recent experiments in the cat have described saccade-related activity as a slow increase in discharge before saccades followed by a hill of activity moving across the SC map. In order to explore this striking difference in the distribution of activity across the SC, we recorded from all saccade-related neurons that we encountered in microelectrode penetrations through the monkey SC and placed them in categories according to their activity during the generation of saccades. 2. When we considered the activity preceding the onset of the saccade, we could divide the cells into two categories. Cells with burst activity had a high-frequency discharge just before saccade onset but little activity between the signal to make a saccade and saccade onset. About two thirds of the saccade-related cells had only a burst of activity. Cells with a buildup of activity began to discharge at a low frequency after the signal to make a saccade and the discharge continued until generation of the saccade. About one third of the saccade-related cells studied had a buildup of activity, and about three fourths of these cells also gave a burst of activity with the saccade in addition to the slow buildup of activity. 3. The buildup of activity seemed to be more closely related to preparation to make a saccade than to the generation of the saccade. The buildup developed even in cases when no saccade occurred. 4. The falling phase of the discharge of these saccade-related cells stopped with the end of the saccade (a clipped discharge), shortly after the end of the saccade (partially clipped), or long after the end of the saccade (unclipped). 5. Some cells had closed movement fields in which saccades that were substantially smaller or larger than the optimal amplitude were not associated with increased activity. Other cells tended to have open-ended movement fields without any peripheral border; they were active for all saccades of optimal direction whose amplitudes were equal to or greater than a given amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The Intervention Effect of SMS Delivery on Chinese Adolescent’s Physical Activity

2019 ◽  
Vol 16 (5) ◽  
pp. 787 ◽  
Author(s):  
Patrick Lau ◽  
Amanda Pitkethly ◽  
Beeto Leung ◽  
Erica Lau ◽  
Jing-Jing Wang
Keyword(s):  
Hong Kong ◽  
High Frequency ◽  
Total Duration ◽  
Low Frequency ◽  
Chinese Adolescents ◽  
Hong Kong Chinese ◽  
Control Group ◽  
Growth Trend ◽  
Intervention Effects ◽  
Sms Intervention

To examine the effects of short messaging service (SMS) frequency and timing on the efficacy of an SMS-intervention for Hong Kong Chinese adolescents, sixty nine students aged between 12 and 16 (mean age 13.75 ± 0.90) were recruited from five schools in Hong Kong. Participants were randomly assigned into one of five groups: high-frequency + self-selected timing (HST), low-frequency + self-selected timing (LST), high-frequency + assigned timing (HAT), low-frequency + assigned timing (LAT) and the control group. The total duration of the intervention was four weeks. No significant intervention effects were detected in adolescent’s PA among the five groups (F = 1.14, p = 0.346). No significant differences were observed in the stage movement among the five groups (χ2 = 6.18, p = 0.627). No significant differences appeared in the exercise benefits, barriers and benefits/barriers differential scores. However, a growth trend in the exercise benefits score in the LST and HAT groups was found in contrast to the downswing in the control group. The exercise barriers score in the HST group showed the largest reduction after intervention. The benefits/barriers differential score in all the intervention groups increased, whereas it decreased in the control group. Although an increase is demonstrated in the high dosage SMS frequency and timing, no significant intervention effects were found among the five groups in PA behavior, stage of change and exercise benefits and barriers among Hong Kong Chinese adolescents.

Effect of Sublethal DDT on the Lateral Line of Brook Trout, Salvelinus fontinalis

1968 ◽  
Vol 25 (12) ◽  
pp. 2677-2682 ◽  
Author(s):  
John M. Anderson
Keyword(s):  
Temperature Coefficient ◽  
Lateral Line ◽  
High Frequency ◽  
Brook Trout ◽  
Negative Temperature Coefficient ◽  
Low Frequency ◽  
Negative Temperature ◽  
Lateral Line Nerve ◽  
General Terms ◽  
Frequency Burst

The lateral line nerve of brook trout responds to an abrupt low-frequency pressure wave, generated by a falling drop of water hitting the water surface, by a relatively short high-frequency burst of large spikes. The burst duration has a negative temperature coefficient. Exposure of trout for 24 hr to DDT, ranging from 0.1 to 0.3 ppm, renders the lateral line nerve hypersensitive to the experimental stimulus; in particular there is a marked increase, especially at the colder temperatures, in the negativity of the temperature coefficient of the burst durations. The results are discussed in general terms, as well as specifically in relation to other laboratory work which shows that sublethal DDT affects behavioural responses of fish to temperature.

Seeing the Same Words Differently: The Time Course of Automaticity and Top–Down Intention in Reading

2015 ◽  
Vol 27 (8) ◽  
pp. 1542-1551 ◽  
Author(s):  
Kristof Strijkers ◽  
Daisy Bertrand ◽  
Jonathan Grainger
Keyword(s):  
Language Processing ◽  
High Frequency ◽  
Time Course ◽  
Lexical Processing ◽  
Low Frequency ◽  
Stimulus Onset ◽  
Top Down ◽  
Electrophysiological Response ◽  
The Brain

We investigated how linguistic intention affects the time course of visual word recognition by comparing the brain's electrophysiological response to a word's lexical frequency, a well-established psycholinguistic marker of lexical access, when participants actively retrieve the meaning of the written input (semantic categorization) versus a situation where no language processing is necessary (ink color categorization). In the semantic task, the ERPs elicited by high-frequency words started to diverge from those elicited by low-frequency words as early as 120 msec after stimulus onset. On the other hand, when categorizing the colored font of the very same words in the color task, word frequency did not modulate ERPs until some 100 msec later (220 msec poststimulus onset) and did so for a shorter period and with a smaller scalp distribution. The results demonstrate that, although written words indeed elicit automatic recognition processes in the brain, the speed and quality of lexical processing critically depends on the top–down intention to engage in a linguistic task.

Frequency Effects on Spelling Error Recognition: An ERP Study

2022 ◽  
Author(s):  
Ekaterina Larionova ◽  
Olga Martynova
Keyword(s):  
Word Frequency ◽  
High Frequency ◽  
Word Processing ◽  
Time Course ◽  
Time Window ◽  
Low Frequency ◽  
Spelling Error ◽  
Spelling Errors ◽  
Error Recognition ◽  
High Frequency Words

Spelling errors are ubiquitous in all writing systems. Most studies exploring spelling errors focused on the phonological plausibility of errors. However, unlike typical pseudohomophones, spelling errors occur in naturally produced written language with variable frequencies. We investigated the time course of recognition of the most frequent orthographic errors in Russian (error in an unstressed vowel at the root) and the effect of word frequency on this process. During ERP recording, 26 native Russian speakers silently read high-frequency correctly spelled words, low-frequency correctly spelled words, high-frequency words with errors, and low-frequency words with errors. The amplitude of P200 was more positive for correctly spelled words than for misspelled words and did not depend on the frequency of the words. Word frequency affected spelling recognition in the later stages of word processing (350-700 ms): high-frequency misspelled words elicited a greater P300 than high-frequency correctly spelled words, and low-frequency misspelled words elicited a greater N400 than low-frequency correctly spelled words. We observe spelling effects in the same time window for both the P300 and N400, which may reflect temporal overlap between mainly categorization processes based on orthographic properties for high-frequency words and phonological processes for low-frequency words. We concluded that two independent pathways can be active simultaneously during spelling recognition: one reflects mainly orthographic processing of high-frequency words and the other is the phonological processing of low-frequency words. Our findings suggest that these pathways are associated with different ERP components. Therefore, our results complement existing reading models and demonstrate that the neuronal underpinnings of spelling error recognition during reading depend on word frequency.

A neural correlate for the gap effect on saccadic reaction times in monkey

1995 ◽  
Vol 73 (6) ◽  
pp. 2558-2562 ◽  
Author(s):  
M. C. Dorris ◽  
D. P. Munoz
Keyword(s):  
Superior Colliculus ◽  
Time Course ◽  
Discharge Rate ◽  
Reaction Times ◽  
Gap Effect ◽  
Saccade Target ◽  
Neural Correlate ◽  
Similar Time ◽  
Initial Fixation ◽  
Saccadic Reaction Times

1. The reduction in saccadic reaction time associated with the introduction of a period of darkness between the disappearance of an initial fixation point and the appearance of a new peripheral saccade target is known as the gap effect. Fixation cells in the rostral pole of the monkey superior colliculus have been implicated in the control of active visual fixation and suppressing saccadic eye movements. To determine whether specific variations of fixation cell discharge was correlated to the gap effect, we recorded the activity of fixation cells while a monkey generated visually guided saccades with various temporal gaps between the disappearance of the initial fixation point and the appearance of a peripheral saccade target. 2. The saccadic reaction times of the monkey were shortest with gap durations of 200-300 ms and increased with shorter or longer gap durations. The activity of fixation cells followed a similar time course, having a minimum discharge rate 200-300 ms into the gap, and increased activity at the time of target appearance with smaller or larger gap durations. 3. We propose that the activity of fixation cells in the monkey superior colliculus provide a neural correlate of the gap effect. The decrease in activity of fixation cells 200-300 ms into the gap weakens the powerful state of inhibition which they normally exert upon the saccade generating system, allowing targets to be acquired at shorter reaction times.

scholarly journals Activity of long-lead burst neurons in pontine reticular formation during head-unrestrained gaze shifts

2014 ◽  
Vol 111 (2) ◽  
pp. 300-312 ◽  
Author(s):  
Mark M. G. Walton ◽  
Edward G. Freedman
Keyword(s):  
Reticular Formation ◽  
Head Movement ◽  
High Frequency ◽  
Low Frequency ◽  
Pontine Reticular Formation ◽  
Gaze Shifts ◽  
Gaze Shift ◽  
Burst Neurons ◽  
Saccade Onset ◽  
Neurophysiological Studies

Primates explore a visual scene through a succession of saccades. Much of what is known about the neural circuitry that generates these movements has come from neurophysiological studies using subjects with their heads restrained. Horizontal saccades and the horizontal components of oblique saccades are associated with high-frequency bursts of spikes in medium-lead burst neurons (MLBs) and long-lead burst neurons (LLBNs) in the paramedian pontine reticular formation. For LLBNs, the high-frequency burst is preceded by a low-frequency prelude that begins 12–150 ms before saccade onset. In terms of the lead time between the onset of prelude activity and saccade onset, the anatomical projections, and the movement field characteristics, LLBNs are a heterogeneous group of neurons. Whether this heterogeneity is endemic of multiple functional subclasses is an open question. One possibility is that some may carry signals related to head movement. We recorded from LLBNs while monkeys performed head-unrestrained gaze shifts, during which the kinematics of the eye and head components were dissociable. Many cells had peak firing rates that never exceeded 200 spikes/s for gaze shifts of any vector. The activity of these low-frequency cells often persisted beyond the end of the gaze shift and was usually related to head-movement kinematics. A subset was tested during head-unrestrained pursuit and showed clear modulation in the absence of saccades. These “low-frequency” cells were intermingled with MLBs and traditional LLBNs and may represent a separate functional class carrying signals related to head movement.

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