scholarly journals Target luminance modulates saccadic behavior and visual sensory responses in the superior colliculus

2010 ◽  
Vol 7 (9) ◽  
pp. 244-244
Author(s):  
R. Marino ◽  
R. Levy ◽  
D. Munoz
Keyword(s):  
Superior Colliculus ◽  
Target Luminance ◽  
Sensory Responses

Importance of NMDA receptors for multimodal integration in the deep layers of the cat superior colliculus

1996 ◽  
Vol 75 (2) ◽  
pp. 920-930 ◽  
Author(s):  
K. E. Binns ◽  
T. E. Salt
Keyword(s):  
Nmda Receptor ◽  
Superior Colliculus ◽  
Nmda Receptors ◽  
Nmda Receptor Antagonist ◽  
Multimodal Integration ◽  
Nonlinear Properties ◽  
Somatosensory Information ◽  
Deep Layers ◽  
Sensory Responses ◽  
Single Modality

1. Many sensory events contain multimodal information, yet most sensory nuclei are devoted to the analysis of single-modality information. In the deep superior colliculus (DSC), visual, auditory, and somatosensory information converges on individual multimodal neurons. The responses of multimodal neurons are determined by the temporal and spatial correspondence properties of the converging inputs such that stimuli arising from the same event elicit a facilitated multimodal response. 2. N-methyl-D-aspartate (NMDA) receptors may underlie the detection of spatial and temporal coincidence and could be involved in the generation of multimodal facilitatory responses because of the nonlinear properties of NMDA-receptor-mediated events. To assess the role of NMDA receptors in multimodal integration, we made extracellular recordings from single multisensory neurons in the DSC of the cat. 3. The responses to visual, auditory, and somatosensory stimuli alone and to multimodal combinations of stimuli were challenged with iontophoretically applied D-2-amino-5-phosphonovalerate (AP5), an NMDA receptor antagonist. All responses to visual stimuli presented alone (n = 9) were greatly reduced. Somatosensory responses (n = 25) were usually decreased. In contrast, the responses to auditory stimulation were decreased (n = 9), unaffected (n = 3), or enhanced (n = 5). 4. Responses to multimodal stimulus presentations were consistently reduced during iontophoretic application of AP5, irrespective of the modalities that made up the stimulus. The reductions of multimodal responses were significantly greater than the sum of the reductions of responses to single-modality stimuli. 5. The data suggest that for unimodal stimuli, the importance of NMDA receptors in synaptic transmission of sensory responses in DSC may be dependent on the stimulus modality. Furthermore, NMDA receptors are of major importance in the integration of input from different modalities for the generation of multimodal responses.

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.

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.

Saccades to somatosensory targets. III. eye-position-dependent somatosensory activity in primate superior colliculus

1996 ◽  
Vol 75 (1) ◽  
pp. 439-453 ◽  
Author(s):  
J. M. Groh ◽  
D. L. Sparks
Keyword(s):  
Motor Activity ◽  
Superior Colliculus ◽  
Body Surface ◽  
Body Position ◽  
Frame Of Reference ◽  
The Body ◽  
Eye Position ◽  
Limited Region ◽  
Somatosensory Responses ◽  
Sensory Responses

1. We recorded from cells with sensory responses to somatosensory stimuli in the superior colliculus (SC) of awake monkeys. Our goal was to determine the frame of reference of collicular somatosensory signals by seeing whether the positions of the eyes influenced the responses of cells to a given tactile stimulus. Somatosensory targets consisted of vibrotactile stimuli delivered to the hands, which were held in fixed spatial positions. Monkeys performed a delayed saccade task from different initial fixation positions to the locations of these tactile stimuli or to visual stimuli at approximately the same location. 2. The responses of a majority of somatosensory cells (25 of 34 or 74%) were significantly affected by eye position. Nearly all somatosensory cells also responded to visual targets (28 of 30, 93%). Cells whose somatosensory responses depended on eye position responded to visual and somatosensory targets located at approximately the same direction in space with respect to the eyes. 3. The activity of these cells exhibited both sensory and motor qualities. The discharge was more closely linked in time to stimulus onset than to the movement. Sensory features of the stimulus were reflected in the responses: the discharge of a number of cells was phase-locked to the pulses of vibration. The sensory responses occurred even if the animal's next saccade was not directed into the response field of the cell. However, two thirds of the cells also exhibited a burst of motor activity in conjunction with the saccade to the somatosensory target. Sensory and motor activity were not always spatially coextensive. When different, the tuning of motor activity was broader. 4. Cells with somatosensory responses to vibratory stimulation of the hands were found in a wide region of the SC, spanning a 40 degrees range of movement amplitudes. 5. These data show that somatosensory signals in the SC are not purely somatotopic but are dependent on eye position. For stimuli at a fixed location, this eye position dependence allows somatosensory and visual signals to be in register and share a premotor circuitry for guiding saccadic eye movements. 6. The dependence of the somatosensory responses on eye position suggests that the somatosensory receptive fields may either shift on the body surface or they may be restricted to a limited region of the body surface but be gated by eye (and body) position. Future experiments varying body position and the location of the stimulus on the body surface are needed to determine which of these alternatives is correct. Cells with either type of receptive field could provide an unambiguous signal of the location of somatosensory saccade targets with respect to the eyes. The transformation of somatosensory signals from a body-centered frame of reference to a frame of reference that depends on the position of the stimulus with respect to the eyes is necessary for the correct activation of collicular neurons with motor activity, because this activity encodes saccades as desired changes in eye position.

Ultrastructure of developing visual cortical synapses in the cat superior colliculus

1991 ◽  
Vol 49 ◽  
pp. 156-157
Author(s):  
Caroline A. Miller ◽  
Laura L. Bruce
Keyword(s):  
Superior Colliculus ◽  
Phosphate Buffer ◽  
Receptive Fields ◽  
Visual Cortical Area ◽  
Cortical Synapses ◽  
Visual Cortical ◽  
And Function ◽  
Phosphate Buffered Saline ◽  
The Brain ◽  
Cat Superior Colliculus

The first visual cortical axons arrive in the cat superior colliculus by the time of birth. Adultlike receptive fields develop slowly over several weeks following birth. The developing cortical axons go through a sequence of changes before acquiring their adultlike morphology and function. To determine how these axons interact with neurons in the colliculus, cortico-collicular axons were labeled with biocytin (an anterograde neuronal tracer) and studied with electron microscopy.Deeply anesthetized animals received 200-500 nl injections of biocytin (Sigma; 5% in phosphate buffer) in the lateral suprasylvian visual cortical area. After a 24 hr survival time, the animals were deeply anesthetized and perfused with 0.9% phosphate buffered saline followed by fixation with a solution of 1.25% glutaraldehyde and 1.0% paraformaldehyde in 0.1M phosphate buffer. The brain was sectioned transversely on a vibratome at 50 μm. The tissue was processed immediately to visualize the biocytin.

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