Ensemble cortical responses to rival visual stimuli: Effect of monocular transient

Binocular rivalry is a fascinating perceptual phenomenon that has been characterized extensively at the psychophysical level. However, the underlying neural mechanism remains poorly understood. In particular, the role of the early visual pathway remains controversial. In this study, we used voltage-sensitive dye imaging to measure the spatiotemporal activity patterns in cat area 18 evoked by dichoptic orthogonal grating stimuli. We found that after several seconds of monocular stimulation with an oriented grating, an orthogonal stimulus to the other eye evoked a reversal of the cortical response pattern, which may contribute to flash suppression in perception. Furthermore, after several seconds of rival binocular stimulation with unequal contrasts, transient increase in the contrast of the weak stimulus evoked a long-lasting cortical response. This transient-triggered response could contribute to the perceptual switch during binocular rivalry. Together, these results point to a significant contribution of early visual cortex to transient-triggered switch in perceptual dominance.     

A Combination of Chemosensory and Mechanosensory Stimuli Triggers the Male Mating Response in the Giant Rotifer Asplanchna sieboldi

The rotifer Asplanchna sieboldi performs several well-defined behavioural responses to external stimuli. Contact of male and female occasionally elicits a mating response in the male. The mating response is composed of a series of distinct behavioural elements. After the initial contact, the male stretches out its body wall outgrowths, arcs into a characteristic mating posture and glides along the surface of the female until the penis becomes attached to the female's body wall, through which the spermatozoa are injected. Under experimental conditions, the mating response could be evoked by stimulation with agar spheres that were impregnated with extracts prepared from females, while agar spheres prepared from buffer only did not cause any mating response. If the active substance was added directly to the suspending medium in the observation chamber, mating could be triggered just by mechanical stimulation. It is concluded that the mating response is triggered by a combination of chemical and mechanical stimuli. During the time course of the experiment there was no adaptation to the chemical stimulus. The receptor cells involved in the perception of the two stimuli remain to be identified. The mating response suppressed other behavioural responses that are usually triggered by tactile stimulation of the apical mechanosensors, suggesting that signal processing by the nervous system occurs.     

Noncholinergic Transmitter(s) Maintains Secretion of Catecholamines from Rat Adrenal Medulla for Several Hours of Continuous Stimulation of Splanchnic Neurons

The effect of continuous stimulation of splanchnic nerves at 1, 3, and 10 Hz on the secretion of catecholamines from the isolated rat adrenal gland was examined. Secretion evoked at 10 Hz declined over 60% in 1 h, and by the end of 4 h the secretion was only 10% of the initial value. The secretion evoked at 3 Hz was unchanged in the first hour, but showed a gradual decline in subsequent hours. In contrast, secretion evoked at 1 Hz was well maintained for several hours. Even after 6 h of continuous stimulation, the decline was only about 35%. Atropine plus hexamethonium reduced the secretion evoked at 10 Hz by over 80%, but that evoked at 1 Hz was reduced by about 35%; addition of naloxone reduced it to 75%. When the secretion declined to very low levels after continuous stimulation at 10 Hz for 100 min, a change in frequency to 3 Hz or 1 Hz caused a sharp rebound in the secretory response. Returning the frequency back to 10 Hz led to a sharp drop in the secretion, whereas reducing the frequency to 1 or 3 Hz once again increased the secretion. The rebound in the secretory response after switchover of frequencies was observed in the presence of atropine plus hexamethonium, but was abolished by naloxone. Extensive stimulations, which caused large amounts of catecholamine secretions at each frequency, were not associated with any loss in tissue catecholamine contents. The major conclusion is that secretion of catecholamines is maintained uninterrupted for several hours when splanchnic nerves are stimulated at low frequency.(ABSTRACT TRUNCATED AT 250 WORDS)     

Temporal coding in the guinea-pig auditory cortex as revealed by optical imaging and its pattern-time-series analysis

The neural network structure of a guinea-pig's primary auditory cortex is estimated by applying pattern-time-series analysis to the auditory evoked responses. Spatiotemporal patterns in click-evoked responses, observed by optical recording with voltage-sensitive dye, are analyzed by time series analysis using a multivariable autoregressive (MAR) model. Oscillatory neural activities with a distribution of about 10 40 Hz in the click-induced evoked responses are found in the cortical response field. The cortical regions where the distributed neural oscillations are generated are identified by pattern-time-series analysis. In addition, two types of cortico-cortical connections, unilateral and bilateral connections between the cortical points, are speculated to be the causes of oscillatory neural activity transfer. It can be said that the so-called synchronized neural oscillation, in the sense of coherency or correlation between the two evoked responses at the oscillatory frequency, does not necessarily represent real corticocortical neural connections at the evoked response points.     

Photoreceptor evoked potentials and phototactic behaviour in Cercaria caribbea LXXI cable

1. Transient potential changes evoked in response to light stimuli, and presumably arising from rhabdomeric eye-spots in the cercarial body, were recorded for the first time, to our knowledge, in helminth parasites. 2. Pigmented Cercaria caribbea LXXI gave a very slowly adapting response to maintained light stimulus, while a non-pigmented variety appeared to emit a stronger, rapidly adapting response to light onset. 3. Swimming towards a directional light source is disrupted by several neuropharmacological agents, which presumably disturb synaptic transmission in the nerve/muscle system. 4. The light evoked potentials were unaffected by these same agents and therefore, appeared to be directly recorded receptor potentials.     

Neuropeptide modification of chloride secretion in guinea pig distal colon

This study examined the effects of electrically stimulating submucosal neurons in the guinea pig isolated distal colonic mucosa and determined the effects of several peptides that are present in these neurons. Electrical field stimulation of muscle-stripped segments of guinea pig distal colonic mucosa, set up in Ussing flux chambers, evoked an increase in short-circuit current (Isc), of 371 +/- 31 MicroA.cm-2. The response to electrical stimulation was abolished by tetrodotoxin and significantly reduced by serosal furosemide. Atropine reduced, but did not abolish, the neurally evoked response. Addition of neuropeptide Y and galanin to the serosal bath had no effect on baseline Isc, but both evoked a concentration-dependent decrease in the neurally evoked secretory response. Vasoactive intestinal polypeptide evoked a concentration-dependent increase in basal (unstimulated) Isc that was reduced by furosemide and unaltered by tetrodotoxin. Neuropeptide Y, but not galanin, significantly reduced the secretory responses to vasoactive intestinal polypeptide and bethanechol. Somatostatin 201-995 and human calcitonin gene-related peptide had no effect on basal Isc nor did either alter the neurally evoked response. These results suggest that acetylcholine and non-cholinergic neurotransmitter(s) stimulate chloride secretion in the guinea pig distal colonic mucosa. This neurosecretory response may be modulated by neuropeptide Y and galanin that are found within submucosal neurons.     

Integrated mismatch negativity (MMNi): a noise-free representation of evoked responses allowing single-point distribution-free statistical tests

If the repeated presentation of a single (standard) auditory stimulus is randomly interspersed with a second acoustically different (deviant) stimulus, the cortical activity evoked by the deviant stimulus can contain a negative component known as the mismatch negativity (MMN). The MMN is derived by subtracting the averaged response evoked by the standard stimulus from that evoked by the deviant stimulus. When the magnitude of the response is small or the signal-to-noise ratio is poor, it is difficult to judge the presence or absence of the MMN simply by visual inspection, and statistical detection techniques become necessary. A method of analysis is proposed to quantify the magnitude and statistically evaluate the presence of the MMN based on time-integrated evoked responses. This paper demonstrates the use of this integrated mismatch negativity (MMN_i) analysis to detect the MMN evoked by stimulus contrasts near the perceptual threshold of two subjects. The MMN_i, by virtue of being equivalent to a low-pass filtered response, presents an almost noise-free estimate of MMN magnitude. A single measure of the integrated evoked response at a fixed time point is used in a distribution-free statistic that compares the magnitude of the averaged response evoked by the deviant stimulus with a magnitude distribution derived from 200 subaveraged responses to the standard stimulus (with the number of sweeps per average equal to that of the deviant stimulus). This allows a calculation of the exact probability for the null hypothesis that the negative magnitude of the response evoked by the deviant stimulus is drawn from the magnitude distribution of responses evoked by the standard stimulus. Rejection of this hypothesis provides objective evidence of the presence of the MMN.     

Event-related potentials in an auditory oddball situation in the rat

Evoked potentials were recorded from the auditory cortex of both freely moving and anesthetized rats when deviant sounds were presented in a homogenous series of standard sounds (oddball condition). A component of the evoked response to deviant sounds, the mismatch negativity (MMN), may underlie the ability to discriminate acoustic differences, a fundamental aspect of auditory perception. Whereas most MMN studies in animals have been done using simple sounds, this study involved a more complex set of sounds (synthesized vowels). The freely moving rats had previously undergone behavioral training in which they learned to respond differentially to these sounds. Although we found little evidence in this preparation for the typical, epidurally recorded, MMN response, a significant difference between deviant and standard evoked potentials was noted for the freely moving animals in the 100-200 ms range following stimulus onset. No such difference was found in the anesthetized animals.     

The stimulus-secretion coupling of amino acid-induced insulin release

Summary Aminooxyacetate, an inhibitor of cytosolic transamination reactions, inhibited insulin release evoked by either 2-ketoisocaproate or L-leucine in rat pancreatic islets incubated in the presence of L-glutamine or L-asparagine. As a rule, aminooxyacetate also inhibited the oxidation of these nutrient secretagogues and impaired the respiratory response of the islets to the combinations of nutrients. However, the oxidative and secretory response to the combination of L-leucine and L-glutamine was less severely affected by aminooxyacetate than that evoked by the three other combinations of exogenous nutrients. These findings reinforce the view that the stimulus-secretion coupling of insulin release in response to L-leucine and 2-ketoisocaproate in association with either L-glutamine or L-asparagine tightly depends on the oxidation of these nutrient secretagogues, on their effect upon O₂ uptake and, within limits, on the intracellular site of generation of reducing equivalents in the pancreatic islet cells.This paper is the 16th in a series.     

Reverberation of recent visual experience in spontaneous cortical waves

Spontaneous waves of activity propagating across large cortical areas may play important roles in sensory processing and circuit refinement. However, whether these waves are in turn shaped by sensory experience remains unclear. Here we report that visually evoked cortical activity reverberates in subsequent spontaneous waves. Voltage-sensitive dye imaging in rat visual cortex shows that following repetitive presentation of a given visual stimulus, spatiotemporal activity patterns resembling the evoked response appear more frequently in the spontaneous waves. This effect is specific to the response pattern evoked by the repeated stimulus, and it persists for several minutes without further visual stimulation. Such wave-mediated reverberation could contribute to short-term memory and help to consolidate the transient effects of recent sensory experience into long-lasting cortical modifications.     

论听觉诱发电位快成分中瞬态反应与稳态反应的相互关系

实验和计算表明,由短声串所引起的头皮诱发电位快成分中,前面的短声对后面短声所诱发的反应有掩蔽作用;短声串所诱发的整个反应,就是每个短声在它之前短声的掩蔽作用下所引起的反应之和.这一结论,看来也可推广到频率跟随反应以至更一般的听觉诱发电位快成分的情形中去.     

Evoked potentials to electrical stimulation of the facial nerve in the carp tectum mesencephali

Tectal evoked potentials to stimulation of the facial nerve, containing afferent fibers of nonolfactory chemoreception, in the carp are positive evoked potentials with a latent period of 5 to 25 msec which show no phase shift as the microelectrode is advanced to a depth of 600 µ. Depending on the amplitude and latency of evoked potentials seven active zones differing in one or both parameters were distinguished in the ipsilateral tectum mesencephali. The role of impulses from the medulla in the mechanism of tectal evoked potentials to facial nerve stimulation is proved by differences in latent periods and disappearance of the tectal response (although it is preserved in the primary center) after severance of connections between the two parts of the brain. Descending influences from the tectum on the primary center were found: its extirpation disturbs evoked potential generation in several parts of the medullla, so that they either disappear completely or their parameters are modified.A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 39–46, January–February, 1976.     

Membrane Potential and Catecholamine Secretion by Bovine Adrenal Chromaffin Cells: Use of Tetraphenylphosphonium Distribution and Carbocyanine Dye Fluorescence

Changes in plasma membrane potential of isolated bovine adrenal chromaffin cells were measured independently by two chemical probe methods and related to corresponding effects on catecholamine secretion. The lipophilic cation tetraphenylphosphonium (TPP+) and the carbocyanine dye 3,3'-dipropylthiadicarbocyanine [DiS-C3-(5)] were used. The necessity of evaluating the subcellular distribution of TPP+ among cytoplasmic, mitochondrial, secretory granule, and bound compartments was demonstrated and the resting plasma membrane potential determined to be -55 mV. The relationship between membrane potential and catecholamine secretion was determined in response to variations in extracellular K+ and to the presence of several secretagogues including cholinergic receptor ligands, veratridine, and ionophores for Na+ and K+. The dependence of potential on K+ concentration fit the Goldman constant field equation with a Na/K permeability ratio of 0.1. The dependence of both K+- and veratridine-evoked catecholamine secretion on membrane potential exhibited a potential threshold of about -40 mV before a significant rise in secretion occurred. This is likely related to the threshold for opening of voltage-sensitive Ca2+ channels. Acetylcholine and nicotine evoked a large secretory response without a sufficiently sustained depolarization to be detectable by the relatively slow potential sensitive chemical probes. Decamethonium induced a detectable depolarization of the chromaffin cells. Veratridine and gramicidin evoked both membrane depolarization and catecholamine release. By contrast the K ionophore valinomycin evoked significant levels of secretion without any depolarization. This is consistent with its utilization of an intracellular source of Ca2+ and the independence of its measured secretory response on extracellular Ca2+.     

Two Distinct Dynamic Modes Subtend the Detection of Unexpected Sounds

The brain response to auditory novelty comprises two main EEG components: an early mismatch negativity and a late P300. Whereas the former has been proposed to reflect a prediction error, the latter is often associated with working memory updating. Interestingly, these two proposals predict fundamentally different dynamics: prediction errors are thought to propagate serially through several distinct brain areas, while working memory supposes that activity is sustained over time within a stable set of brain areas. Here we test this temporal dissociation by showing how the generalization of brain activity patterns across time can characterize the dynamics of the underlying neural processes. This method is applied to magnetoencephalography (MEG) recordings acquired from healthy participants who were presented with two types of auditory novelty. Following our predictions, the results show that the mismatch evoked by a local novelty leads to the sequential recruitment of distinct and short-lived patterns of brain activity. In sharp contrast, the global novelty evoked by an unexpected sequence of five sounds elicits a sustained state of brain activity that lasts for several hundreds of milliseconds. The present results highlight how MEG combined with multivariate pattern analyses can characterize the dynamics of human cortical processes.     

Functional organization of projection zones of lateral line organs in the midbrain of Raja clavata

The character and distribution of evoked potentials in the midbrain during electrical stimulation of the lateral line nerves were investigated in acute experiments on the ray (Raja clavata). The clearest response was observed on the contralateral side of the dorsal surface. The evoked potentials consisted of several components. The initial high-frequency component is regarded as presynaptic. The principal slow component of the evoked potential corresponds to postsynaptic processes. The lateral line organs have spatially differentiated representation with partial overlapping of the projection zones.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 4, pp. 384–391, July–August, 1973.     

Electrical activities of a type of electroretinogram recorded from the ocellus of a jellyfish, Polyorchis penicillatus (Hydromedusae)

An electroretinogram (ERG), evoked by light stimuli, was recorded from ocelli of Polyorchis penicillatus (Hydromedusae). The ERG is a polyphasic response with a positive potential change at the onset of illumination followed by a slower biphasic pulse, and a positive deflection at the cessation of illumination which is followed by a series of high-frequency pulses. The most striking features of the initial pulse are its latency-log intensity relation and the gradation of pulse amplitude with respect to the intensity of the light stimulus and to different wavelengths. Maximum spectral sensitivity lies around 530 nm. Response patterns induced by shadowing and repeated stimulation of light- and dark-adapted ocelli are described. Morphological structures which could give rise to the mass response of the ocellus are discussed.     

Changes in visual evoked potentials after injection of tetanus toxin into the lateral geniculate body

Changes in visual evoked potentials were studied in rats at different stages of formation of experimental photogenic epilepsy induced by injection of tetanus toxin into the lateral geniculate body. The greatest change in evoked potentials in the lateral geniculate body consisted of the appearance of an aditional component in the series of waves of the primary response. Meanwhile in the ipsilateral visual cortex the amplitude of the first negative component of the evoked potential was considerably increased. Correlation was found between the changes in the amplitude of this component in the visual cortex and the change in steepness of the additional component of the evoked potential in the geniculate body, reflecting functional reorganization of that nucleus. The results are evidence of significant disturbances of the relay function of the lateral geniculate body when a generator of pathologically enhanced excitation is formed in it.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 2, pp. 142–149, March–April, 1978.     

Effects of Near-Threshold Stimulation of the Vestibular Apparatus on Postural Responses Evoked by Displacements of the Visualized Surrounding

In healthy subjects in the relaxed upward stance and perceiving a virtual visual environment (VVE), we recorded postural reactions to isolated visual and vestibular stimulations or their combinations. Lateral displacements of the visualized virtual scene were used as visual stimuli. The vestibular apparatus was stimulated by application of near-threshold galvanic current pulses to the proc. mastoidei of the temporal bones. Isolated VVE shifts evoked mild, nonetheless clear, body tilts readily distinguished in separate trials; at the same time, postural effects of isolated vestibular stimulation could be detected only after averaging of several trials synchronized with respect to the beginning of stimulation. Under conditions of simultaneous combined presentation of visual and vestibular stimuli, the direction of the resulting postural responses always corresponded to the direction of responses induced by VVE shifts. The contribution of an afferent volley from the vestibular organ depended on the coincidence/mismatch of the direction of motor response evoked by such a volley with the direction of response to visual stimulation. When both types of stimulations evoked unidirectional body tilts, postural responses were facilitated, and the resulting effect was greater than that of simple summation of the reactions to isolated actions of the above stimuli. In the case where isolated galvanic stimulation evoked a response opposite with respect to that induced by visual stimulation, the combined action of these stimuli of different modalities evoked postural responses identical in their magnitude, direction, and shape to those evoked by isolated visual stimulation. The above findings allow us to conclude that the effects of visual afferent input on the vertical posture under conditions of our experiments clearly dominate. In general, these results confirm the statement that neuronal structures involved in integrative processing of different afferent volleys preferably select certain type of afferentation carrying more significant or more detailed information on displacements (including oscillations) of the body in space.     

Effects of auditory stimulus timing in the respiratory cycle on the evoked cardiac response in man at rest

The present experiments were carried out in 21 healthy adults to study the effects of auditory stimulus timing within the respiratory cycle on evoked cardiac response. The stimulus (80 dB white noise) was started by the first and finished by the second R-wave after change in respiratory phase, and presented in different series in either early inspiration or early expiration. The spirogram and eight sequential interbeat intervals (IBI) after respiratory phase change were recorded. The mean of IBI and standard deviation (SD) were calculated separately for each IBI of 20 trials for each subject, during both the prestimulus and poststimulus phases. The stimulus effects were expressed as changes from prestimulus conditions, in terms of delta IBI and delta SD. The mean of each of the eight IBI and its SD were found to vary consistently in the same direction, i.e., SD increased with increasing mean IBI. Stimulation during early inspiration did not produce any effect during this respiratory phase. It was not before the beginning of the following expiration that a significant deceleration was evoked, which was associated with an enhanced delta SD, whereas stimulation during early expiration promptly evoked a biphasic cardiac response of the deceleration - acceleration pattern and an increase and decrease in delta SD, respectively. While SD was found to be a function of age, no such finding was obtained for delta IBI and delta SD. These results are discussed in terms of the "vagal gating" hypothesis.     

Interweaving and overlapping of evoked potentials

The refractory effect of one stimulus upon the response to a closely following stimulus in a different modality is much less than upon the response to a stimulus in the same modality. It is therefore far more efficient to record responses to stimuli in different modalities concurrently than to record each one separately. We evaluated 2 techniques for concurrent recording. Interweaving involves recording the response to one stimulus in the intervals between recording responses to other stimuli. Overlapping occurs when two or more responses are at times being simulateneously recorded. Interweaving and overlapping reduced the time required to record auditory brain-stem responses, short-latency somatosensory evoked potentials and pattern-reversal visual evoked potentials by a factor of 3 over the time required to record each response separately. Overlapping caused no significant change in the evoked potentials. Depending upon the actual timing schedule, interweaving may distort the evoked potentials if later parts of the response to one stimulus override the evoked potential to a following stimulus. Filtering and randomization of stimulus timing may attenuate the effects of these overriding potentials.