Difference of Spatial Summation Property between b and d Waves in Focal Electroretinogram of the Cat

1992 ◽  
Vol 205 (4) ◽  
pp. 204-210
Author(s):  
Tomoaki Usui
Keyword(s):  
Spatial Summation ◽  
Focal Electroretinogram

scholarly journals Contrast integration over area is extensive: A three-stage model of spatial summation

2011 ◽  
Vol 11 (14) ◽  
pp. 14 ◽  
Author(s):  
Daniel H. Baker ◽  
Tim S. Meese
Keyword(s):  
Spatial Summation ◽  
Stage Model

Spatial summation of perceived pressure, sharpness and mechanically evoked cutaneous pain

1997 ◽  
Vol 14 (2) ◽  
pp. 107-112 ◽  
Author(s):  
JOEL GREENSPAN1 ◽  
MARIA THOMADAKI ◽  
SANDRA McGILLIS
Keyword(s):  
Spatial Summation ◽  
Cutaneous Pain ◽  
Perceived Pressure

Spatial summation of heat-induced pain: influence of stimulus area and spatial separation of stimuli on perceived pain sensation intensity and unpleasantness

1989 ◽  
Vol 62 (6) ◽  
pp. 1270-1279 ◽  
Author(s):  
D. D. Price ◽  
J. G. McHaffie ◽  
M. A. Larson
Keyword(s):  
Spatial Summation ◽  
Stimulus Size ◽  
Experimental Series ◽  
Pain Sensation ◽  
Thermal Probe ◽  
Spinothalamic Tract ◽  
Nociceptive Neurons ◽  
Thermal Probes ◽  
Perceived Pain ◽  
Thermal Stimuli

1. Psychophysical experiments were initiated to determine the possible influence of increasing stimulus size on perceived pain intensity. Six trained human subjects (5 male, 1 female) made visual analogue scale (VAS) ratings for pain-sensation intensity and unpleasantness in response to nociceptive thermal stimuli. Test stimuli consisted of 5-s duration heat pulses (45-50 degrees C in 1 degrees increments) delivered by one, two, or three contact thermal probes (1 cm2 each) applied to the medial aspect of the anterior forearm. 2. The area of skin receiving noxious thermal stimuli was changed by randomly varying the number of thermodes activated. The effects of varying the distance between the thermal probes also were evaluated. In the first series of experiments, thermal-probe separation was kept close to 0; in subsequent experimental series, the thermodes were separated by either 5 or 10 cm. 3. In each experimental series, considerable spatial summation occurred in both pain-sensation intensity and unpleasantness dimensions of pain. This summation occurred throughout the nociceptive thermal range of 45-50 degrees C and was larger at suprathreshold temperatures (greater than or equal to 47 degrees C) than those near threshold (less than or equal to 46 degrees C). Unlike spatial summation of perceived warmth, that of pain was not characterized by systematic changes in power-function exponents but as approximately upward parallel displacements in double-logarithmic coordinates. 4. Thermal-probe separation over a range of 0-10 cm had no effects on spatial summation of pain-sensation intensity or pain unpleasantness. In contrast, increasing thermal-probe separation increased the subjects' ability to discriminate differences in stimulus size and their ability to detect correctly the number of thermal probes activated. 5. Because affective VAS ratings of unpleasantness were linearly related to, but distinctly and systematically less than, VAS ratings of pain-sensation intensity, it was clear that subjects responded quite differently to these two pain dimensions. Affective judgements were not additionally influenced by thermal probe separation and hence by the ability to perceive stimulus size or number of thermal probes activated. 6. The results indicate that powerful spatial-summation mechanisms exist for heat-induced pain. Spatial summation of pain is likely to be subserved both by local integration mechanisms at the level of single spinothalamic-tract neurons and by recruitment of central nociceptive neurons, because spatial summation of pain occurred to approximately equal extents under conditions of thermode separations over a distance of at least 20 cm.

scholarly journals Blindsight after Optic Nerve Injury Indicates Functionality of Spared Fibers

2002 ◽  
Vol 14 (2) ◽  
pp. 243-253 ◽  
Author(s):  
Stefan Wüst ◽  
Erich Kasten ◽  
Bernhard A. Sabel
Keyword(s):  
Visual Cortex ◽  
Optic Nerve ◽  
Nerve Injury ◽  
Visual Stimuli ◽  
Spatial Summation ◽  
Extrastriate Cortex ◽  
Lesion Site ◽  
Optic Nerve Injury ◽  
Stimulus Detection ◽  
Primary Damage

Some patients with lesions in the geniculostriate pathway (GSP) can respond to visual stimuli in the blind field without conscious acknowledgement. The substrate for this “blind-sight” is controversial: whether it is the uninjured extrastriate pathway (EXP), which bypasses the lesion site, or residual fibers within damaged visual cortex (“islands of vision”). Using stimulus detection, localization, and spatial summation tasks, we have found blindsight in patients with damage both in the optic nerve (ON) and EXP. The prevalence and functional characteristics of their blindsight are indistinguishable from that in patients with GSP lesions, so blindsight does not require a completely intact EXP. The present findings support the view that a few surviving ON axons within an area of primary damage are sufficient to mediate blindsight: Several combinations of partially intact pathways can transmit information to the extrastriate cortex and the sum of activation of all visual fibers surviving the injury determines if and to what extent blindsight occurs.

scholarly journals Behavioral Receptive Field for Ocular Following in Humans: Dynamics of Spatial Summation and Center-Surround Interactions

2006 ◽  
Vol 95 (6) ◽  
pp. 3712-3726 ◽  
Author(s):  
Frédéric V. Barthélemy ◽  
Ivo Vanzetta ◽  
Guillaume S. Masson
Keyword(s):  
Visual Field ◽  
Receptive Field ◽  
Visual Motion ◽  
Neuronal Response ◽  
Spatial Summation ◽  
Visuomotor Transformations ◽  
Ocular Following ◽  
Linear Integration ◽  
Response Onset ◽  
Linear Contrast

Visual neurons integrate information over a finite part of the visual field with high selectivity. This classical receptive field is modulated by peripheral inputs that play a role in both neuronal response normalization and contextual modulations. However, the consequences of these properties for visuomotor transformations are yet incompletely understood. To explore those, we recorded short-latency ocular following responses in humans to large center-only and center-surround stimuli. We found that eye movements are triggered by a mechanism that integrates motion over a restricted portion of the visual field, the size of which depends on stimulus contrast and increases as a function of time after response onset. We also found evidence for a strong nonisodirectional center-surround organization, responsible for normalizing the central, driving input so that motor responses are set to their most linear contrast dynamics. Such response normalization is delayed about 20 ms relative to tracking onset, gradually builds up over time, and is partly tuned for surround orientation/direction. These results outline the spatiotemporal organization of a behavioral receptive field, which might reflect a linear integration among subpopulations of cortical visual motion detectors.

scholarly journals Attention operates uniformly throughout the classical receptive field and the surround

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Bram-Ernst Verhoef ◽  
John HR Maunsell
Keyword(s):  
Receptive Field ◽  
Cortical Neurons ◽  
Receptive Fields ◽  
Spatial Summation ◽  
Field Structure ◽  
Neuronal Responses ◽  
Large Variability ◽  
Area V4 ◽  
Classical Receptive Field ◽  
Spatially Varying

Shifting attention among visual stimuli at different locations modulates neuronal responses in heterogeneous ways, depending on where those stimuli lie within the receptive fields of neurons. Yet how attention interacts with the receptive-field structure of cortical neurons remains unclear. We measured neuronal responses in area V4 while monkeys shifted their attention among stimuli placed in different locations within and around neuronal receptive fields. We found that attention interacts uniformly with the spatially-varying excitation and suppression associated with the receptive field. This interaction explained the large variability in attention modulation across neurons, and a non-additive relationship among stimulus selectivity, stimulus-induced suppression and attention modulation that has not been previously described. A spatially-tuned normalization model precisely accounted for all observed attention modulations and for the spatial summation properties of neurons. These results provide a unified account of spatial summation and attention-related modulation across both the classical receptive field and the surround.

Non-motile sensory cilia and neuromuscular junctions in a ctenophore independent effector organ

1965 ◽  
Vol 162 (988) ◽  
pp. 333-350 ◽  
Keyword(s):  
Neuromuscular Junctions ◽  
Ciliated Cell ◽  
Sensory Nerve ◽  
Spatial Summation ◽  
Muscle Cells ◽  
Sensory Cells ◽  
Muscle Fibres ◽  
Water Displacement ◽  
Single Finger ◽  
Effector Organ

Non-motile cilia of the (9 + 2) pattern, having a specialized onion-like root structure, act as sensitive receptors of water displacement and thereby detect vibrations of small objects in the water nearby. These receptors are situated on sensory nerve cells on finger-like processes up to 1 cm long, on the surface of the ctenophore Leucothea ( = Eucharis) multicornis . In response to vibration a single finger can shoot outwards as an independent effector by an extension of its mesogloeal hydrostatic skeleton, acted on by circular and transverse muscle fibres which run mainly through the mesogloea. A copepod which may be hit is immobilized, presumably by a poisonous secretion. Retraction is brought about by longitudinal ectodermal fibres. The neuromuscular junctions have presynaptic vesicles of 30 to 50 nm diameter, a cleft of 15 to 20 nm wide, and occur at discrete points far from each other on the muscle cells, suggesting that excitation is propagated along the muscle fibres. No direct connexion has been traced between a sensory ciliated cell and a muscle fibre, but sensory cells connect with nerve net neurons and these form synapses with each other and with muscle cells. There are numerous nerve fibres in the epithelium and synapses with vesicles on one side of a cleft 12 to 15 nm wide occur between them sufficiently closely for spatial summation to be possible. The separate co-ordination of movements of extension, retraction and bending requires that certain types of sensory cells be connected specifically, if in directly, with muscle fibres of a particular directionality. This provides a primitive example of specificity of connexions which must imply two overlapping nerve nets.

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