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)

Competition Between Saccade Goals in the Superior Colliculus Produces Saccade Curvature

2003 ◽  
Vol 89 (5) ◽  
pp. 2577-2590 ◽  
Author(s):  
Robert M. McPeek ◽  
Jae H. Han ◽  
Edward L. Keller
Keyword(s):  
Superior Colliculus ◽  
Search Task ◽  
Visual Target ◽  
Temporal Structure ◽  
Saccade Target ◽  
Stimulation Site ◽  
Electrical Microstimulation ◽  
Saccade Onset ◽  
Significant Difference ◽  
Increased Activity

When saccadic eye movements are made in a search task that requires selecting a target from distractors, the movements show greater curvature in their trajectories than similar saccades made to single stimuli. To test the hypothesis that this increase in curvature arises from competitive interactions between saccade goals occurring near the time of movement onset, we performed single-unit recording and microstimulation experiments in the superior colliculus (SC). We found that saccades that ended near the target but curved toward a distractor were accompanied by increased presaccadic activity of SC neurons coding the distractor site. This increased activity occurred ∼30 ms before saccade onset and was abruptly quenched on saccade initiation. The magnitude of increased activity at the distractor site was correlated with the amount of curvature toward the distractor. In contrast, neurons coding the target location did not show any significant difference in discharge for curved versus straight saccades. To determine whether this pattern of SC discharge is causally related to saccade curvature, we performed a second series of experiments using electrical microstimulation. Monkeys made saccades to single visual stimuli presented without distractors, and we stimulated sites in the SC that would have corresponded to distractor sites in the search task. The stimulation was subthreshold for evoking saccades, but when its temporal structure mimicked the activity recorded for curved saccades in search, the subsequent saccades to the visual target showed curvature toward the location coded by the stimulation site. The effect was larger for higher stimulation frequencies and when the stimulation site was in the same colliculus as the representation of the visual target. These results support the hypothesis that the increased saccade curvature observed in search arises from rivalry between target and distractor goals and are consistent with the idea that the SC is involved in the competitive neural interactions underlying saccade target selection.

scholarly journals Activity in the human superior colliculus relating to endogenous saccade preparation and execution

2015 ◽  
Vol 114 (2) ◽  
pp. 1048-1058 ◽  
Author(s):  
Michele Furlan ◽  
Andrew T. Smith ◽  
Robin Walker
Keyword(s):  
Superior Colliculus ◽  
Small Amplitude ◽  
Nonhuman Primates ◽  
Imaging Techniques ◽  
Saccadic Eye Movements ◽  
Visual Responses ◽  
Related Activity ◽  
Preparatory Activity ◽  
Saccade Preparation ◽  
Increased Activity

In recent years a small number of studies have applied functional imaging techniques to investigate visual responses in the human superior colliculus (SC), but few have investigated its oculomotor functions. Here, in two experiments, we examined activity associated with endogenous saccade preparation. We used 3-T fMRI to record the hemodynamic activity in the SC while participants were either preparing or executing saccadic eye movements. Our results showed that not only executing a saccade (as previously shown) but also preparing a saccade produced an increase in the SC hemodynamic activity. The saccade-related activity was observed in the contralateral and to a lesser extent the ipsilateral SC. A second experiment further examined the contralateral mapping of saccade-related activity with a larger range of saccade amplitudes. Increased activity was again observed in both the contralateral and ipsilateral SC that was evident for large as well as small saccades. This suggests that the ipsilateral component of the increase in BOLD is not due simply to small-amplitude saccades producing bilateral activity in the foveal fixation zone. These studies provide the first evidence of presaccadic preparatory activity in the human SC and reveal that fMRI can detect activity consistent with that of buildup neurons found in the deeper layers of the SC in studies of nonhuman primates.

scholarly journals Independent Distractor Frequency and Age-of-Acquisition Effects in Picture–Word Interference: fMRI Evidence for Post-lexical and Lexical Accounts according to Distractor Type

2012 ◽  
Vol 24 (2) ◽  
pp. 482-495 ◽  
Author(s):  
Greig I. de Zubicaray ◽  
Michele Miozzo ◽  
Kori Johnson ◽  
Niels O. Schiller ◽  
Katie L. McMahon
Keyword(s):  
High Frequency ◽  
Temporal Cortex ◽  
Low Frequency ◽  
Age Of Acquisition ◽  
Frequency Effect ◽  
Self Monitoring ◽  
Phonological Word ◽  
Increased Activity ◽  
Effect Experiment ◽  
Left Middle

In two fMRI experiments, participants named pictures with superimposed distractors that were high or low in frequency or varied in terms of age of acquisition. Pictures superimposed with low-frequency words were named more slowly than those superimposed with high-frequency words, and late-acquired words interfered with picture naming to a greater extent than early-acquired words. The distractor frequency effect (Experiment 1) was associated with increased activity in left premotor and posterior superior temporal cortices, consistent with the operation of an articulatory response buffer and verbal self-monitoring system. Conversely, the distractor age-of-acquisition effect (Experiment 2) was associated with increased activity in the left middle and posterior middle temporal cortex, consistent with the operation of lexical level processes such as lemma and phonological word form retrieval. The spatially dissociated patterns of activity across the two experiments indicate that distractor effects in picture–word interference may occur at lexical or postlexical levels of processing in speech production.

scholarly journals Functional Parameters of Prestin Are Not Correlated With the Best Hearing Frequency

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhongying Wang ◽  
Qingping Ma ◽  
Jiawen Lu ◽  
Xiaochen Cui ◽  
Haifeng Chen ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Outer Hair Cells ◽  
Amino Acid Sequences ◽  
Striking Difference ◽  
Functional Parameters ◽  
Leading Role ◽  
Frequency Detection ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent

Among the vertebrate lineages with different hearing frequency ranges, humans lie between the low-frequency hearing (1 kHz) of fish and amphibians and the high-frequency hearing (100 kHz) of bats and dolphins. Little is known about the mechanism underlying such a striking difference in the limits of hearing frequency. Prestin, responsible for cochlear amplification and frequency selectivity in mammals, seems to be the only candidate to date. Mammalian prestin is densely expressed in the lateral plasma membrane of the outer hair cells (OHCs) and functions as a voltage-dependent motor protein. To explore the molecular basis for the contribution of prestin in hearing frequency detection, we collected audiogram data from humans, dogs, gerbils, bats, and dolphins because their average hearing frequency rises in steps. We generated stable cell lines transfected with human, dog, gerbil, bat, and dolphin prestins (hPres, dPres, gPres, bPres, and nPres, respectively). The non-linear capacitance (NLC) of different prestins was measured using a whole-cell patch clamp. We found that the Qmax/Clin of bPres and nPres was significantly higher than that of humans. The V1/2 of hPres was more hyperpolarized than that of nPres. The z values of hPres and bPres were higher than that of nPres. We further analyzed the relationship between the high-frequency hearing limit (Fmax) and the functional parameters (V1/2, z, and Qmax/Clin) of NLC among five prestins. Interestingly, no significant correlation was found between the functional parameters and Fmax. Additionally, a comparative study showed that the amino acid sequences and tertiary structures of five prestins were quite similar. There might be a common fundamental mechanism driving the function of prestins. These findings call for a reconsideration of the leading role of prestin in hearing frequency perception. Other intriguing kinetics underlying the hearing frequency response of auditory organs might exist.

scholarly journals Tenors Not Sopranos: Bio-Mechanical Constraints on Calling Song Frequencies in the Mediterranean Field-Cricket

2021 ◽  
Vol 9 ◽  
Author(s):  
Thorin Jonsson ◽  
Fernando Montealegre-Z ◽  
Carl D. Soulsbury ◽  
Daniel Robert
Keyword(s):  
High Frequency ◽  
Sound Production ◽  
Low Frequency ◽  
Field Cricket ◽  
Striking Difference ◽  
Destructive Interference ◽  
Coupled Resonators ◽  
Mechanical Constraints ◽  
Close Relatives ◽  
Bush Crickets

Male crickets and their close relatives bush-crickets (Gryllidae and Tettigoniidae, respectively; Orthoptera and Ensifera) attract distant females by producing loud calling songs. In both families, sound is produced by stridulation, the rubbing together of their forewings, whereby the plectrum of one wing is rapidly passed over a serrated file on the opposite wing. The resulting oscillations are amplified by resonating wing regions. A striking difference between Gryllids and Tettigoniids lies in wing morphology and composition of song frequency: Crickets produce mostly low-frequency (2–8 kHz), pure tone signals with highly bilaterally symmetric wings, while bush-crickets use asymmetric wings for high-frequency (10–150 kHz) calls. The evolutionary reasons for this acoustic divergence are unknown. Here, we study the wings of actively stridulating male field-crickets (Gryllus bimaculatus) and present vibro-acoustic data suggesting a biophysical restriction to low-frequency song. Using laser Doppler vibrometry (LDV) and brain-injections of the neuroactivator eserine to elicit singing, we recorded the topography of wing vibrations during active sound production. In freely vibrating wings, each wing region resonated differently. When wings coupled during stridulation, these differences vanished and all wing regions resonated at an identical frequency, that of the narrow-band song (∼5 kHz). However, imperfections in wing-coupling caused phase shifts between both resonators, introducing destructive interference with increasing phase differences. The effect of destructive interference (amplitude reduction) was observed to be minimal at the typical low frequency calls of crickets, and by maintaining the vibration phase difference below 80°. We show that, with the imperfect coupling observed, cricket song production with two symmetric resonators becomes acoustically inefficient above ∼8 kHz. This evidence reveals a bio-mechanical constraint on the production of high-frequency song whilst using two coupled resonators and provides an explanation as to why crickets, unlike bush-crickets, have not evolved to exploit ultrasonic calling songs.

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)

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.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

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