Excitation transfer in communication-mediated aggressive behavior

To test the effect of excitation produced during exposure to communication, both the excitatory potential and the degree of manifest aggressiveness of communications were assessed to select: (a) an aggressive communication associated with a particular excitatory potential; (b) a nonaggressive communication associated with an excitatory potential significantly below that of a; and (c) another nonaggressive communication associated with an excitatory potential significantly above that of a. A model of excitation transfer was advanced, based on the assumption that salient elements of excitation decay relatively slowly, and that interoception of excitation is nonspecific, permitting the integration of any residue with elements of the excitatory response to subsequent stimuli. If the postcommunication situation provides the individual with perception-cognitions enabling him to unambiguously interpret his emotional state, it is expected that this state is intensified by the magnitude of the excitational residue from the response to the communication. It was predicated that, quite independent of the degree of aggression manifest in the communication, postcommunication aggressive behavior would be facilitated mainly as a function of the communication's excitatory potential. The highly significant results obtained (b < a < c) were fully consistent with the predictions from the transfer paradigm.     

Neuron circuits: The self-exciting neuron

Conditions are determined under which a single self-exciting neuron can reach a state of permanent excitation, in the case that the neuron develops both an excitatory and an inhibitory substance as well as in the case that it develops only a single, excitatory substance. In case both substances are developed it is possible to have periodic solutions, a possibility which does not arise when the circuit consists of neurons, or of a neuron, developing only an excitatory substance.     

Irrelevance of mitigating circumstances in retaliatory behavior at high levels of excitation

Subjects were aggressively instigated by a provoker. They then performed either a nonstrenuous or a strenuous task in order to be placed in either a moderate or an extreme state of sympathetic arousal. Following the task, they either learned or did not learn about mitigating circumstances behind the provoker's behavior. This information was received prior to the provision of an opportunity to retaliate. Under conditions of moderate arousal, mitigating circumstances were found to reduce retaliation. In contrast, these circumstances failed to exert any appreciable effect on retaliation under conditions of extreme arousal. In addition, the induction of extreme arousal was observed to increase retaliatory behavior. The findings were considered to support a model of hostility and aggression that postulates a specific interdependency of cognitive and excitatory processes.     

Signaling in large-scale neural networks

We examine the recent finding that neurons in spinal motor circuits enter a high conductance state during functional network activity. The underlying concomitant increase in random inhibitory and excitatory synaptic activity leads to stochastic signal processing. The possible advantages of this metabolically costly organization are analyzed by comparing with synaptically less intense networks driven by the intrinsic response properties of the network neurons.     

A model of pavlovian conditioning: Variations in representations of the unconditional stimulus

We present a model of Pavlovian excitatory conditioning in which associative strength and malleable central representations of unconditional stimuli determine the strength of conditional responding. Presentation of a conditioned stimulus acts through an experientially determined associative bond to activate a representation of the unconditional stimulus. The activation of the representation produces a conditioned response. A striking feature of the model is its ability to describe changes in conditioned response magnitude in terms of alterations of representations of the unconditional stimulus. Another is its acknowledgement of the capacity of associative bonds to survive behavioral extinction. The model describes much of the data reported from excitatory conditioning experiments and predicts counterintuitive phenomena. This work was supported by Natural Sciences and Engineering Research Council grant #U0262 awarded to the first author.     

Signaling in large-scale neural networks

We examine the recent finding that neurons in spinal motor circuits enter a high conductance state during functional network activity. The underlying concomitant increase in random inhibitory and excitatory synaptic activity leads to stochastic signal processing. The possible advantages of this metabolically costly organization are analyzed by comparing with synaptically less intense networks driven by the intrinsic response properties of the network neurons.     

A dynamic extraversion model. The brain's response to a single dose of a stimulant drug

The aim of this paper is to present a mathematical dynamic modelling of the effect a stimulant drug has on different people which, at the same time, can be a useful tool for future brain studies. To this end, a dynamic model of the evolution of extraversion (considering its tonic and phasic aspects) has been constructed taking into account the unique personality trait theory and the general modelling methodology. This model consists of a delayed differential equation which, on one hand, considers that the active stimulus, a consequence of a single intake, is not constant; on the other hand, it contemplates that the state variable representing the phasic extraversion also represents the brain activation. The derivative of this state variable is calculated as the sum of the homeostatic control flow, the excitatory effect flow and the inhibitor effect flow. The solutions of this equation relate the tonic activation of an individual (that characterizes his or her personality) with his or her phasic activation level, whose evolution over time describes the organism's response to a single drug intake. These solutions quantitatively reproduce the predictions of current personality theories and anticipate vulnerability to drug misuse and addiction development.     

Effect of timing of information about mitigating circumstances on emotional responses to provocation and retaliatory behavior

To determine whether the reduction of retaliatory behavior by knowledge of mitigating circumstances is due to less motivation to retaliate or to an inhibition of motivated retaliation, subjects were provoked by a rude experimenter and informed of mitigating conditions (a) before provocation, (b) after provocation, or (c) not at all. Physiological data revealed that prior knowledge of mitigation prevented pronounced excitatory responses to prococation. In contrast, when mitigating conditions were not known, excitatory responses to provocation were intense. In addition, when mitigating information was supplied after provocation, excitatory responses decayed more rapidly than when no such information was supplied. Retaliatory behavior, as measured in complaints about the rude experimenter, was substantially lower in the condition in which mitigation preceded provocation than in the other two conditions. The retaliatory behavior of subjects who were informed of mitigation after being provoked did not differ significantly from that of subjects who were not informed of mitigation. The findings were interpreted as incompatible with the assumption that under mitigating conditions retaliation is motivated but inhibited and as generally supportive of the proposal that mitigation attenuates the response to provocation. In order to explain the failure of the reception of mitigating information after provocation to reduce retaliatory behavior in spite of the observed facilitation of excitatory decay, it was suggested that when subjects were experiencing high levels of anger, they formed a behavioral disposition to retaliate, which outlasted the state of elevated arousal.     

Cellular abnormalities and synaptic plasticity in seizure disorders of the immature nervous system

The nervous system has an enhanced capacity to generate seizures during a restricted phase of postnatal development. Studies in animals and particularly in in vitro brain slices from hippocampus and neocortex have been instrumental in furthering an understanding of the underlying processes. Developmental alterations in glutaminergic excitatory synaptic transmission appear to play a key role in the enhanced seizure susceptible of rodents during the second and third week of life. Prior to this period, the number of excitatory synapses is relatively low. The scarcity of connections and the inability of the existing synapses to release glutamate when activated at high frequencies likely contribute importantly to the resistance of neonates to seizures. However, at the beginning of week 2, a dramatic outgrowth of excitatory synapses occurs, and these synapses are able to faithfully follow activation at high frequencies. These changes, coupled with the prolonged nature of synaptic potentials in early life, likely contribute to the ease of seizure generation. After this time, seizure susceptibility declines, patterns of local synaptic connectivity remodel, and some synapses are pruned. Concurrently, the duration of excitatory postsynaptic potentials shortens due at least in part to a switch in the subunit composition of postsynaptic receptors. Other studies have examined the mechanisms underlying chronic epilepsy initiated in early life. Models of both cortical dysplasia and recurrent early-life seizures suggest that alterations in the normal development of excitatory synaptic transmission can contribute importantly to chronic epileptic conditions. In the recurrent early-life seizure model, abnormal use-dependent selection of subpopulations of excitatory synapses may play a role. In experimental cortical dysplasia, alterations in the molecular composition of postsynaptic receptor are observed that favor subunit combinations characteristic of infancy.     

Selection for conditionability in Drosophila melanogaster.

Successful bidirectional selective breeding of Drosophila melanogaster for excitatory conditionability is reported, using the reliable measures of individual differences (first described by Holliday & Hirsch, 1984, 1986a, 1986b) to test 1,324 animals. Bidirectional selective breeding for good and poor conditioning has produced, respectively, one population in which the percentage of animals showing good conditioning has increased over 25 generations from 19% to 77% and another in which it has decreased over 23 generations to 0%-4%. No increase in a measure of sensitization induced by an unconditioned stimulus (the central excitatory state) accompanied the increase in the percentage of good conditioners in the population selected for good conditioning, whose level of conditioned responding exceeds that of the sensitization measure.     

Conditioned inhibition is not the symmetrical opposite of conditioned excitation: A test of the Rescorla-Wagner model

Rescorla and Wagner's (1972) linear associative model of learning predicts that a neutral stimulus will become weakly excitatory if it is paired with a conditioned inhibitor and the compound is not reinforced. If the inhibitor is not allowed to extinguish during these pairings, the model predicts that the neutral stimulus will become strongly excitatory. Rescorla (1971) has presented some evidence to support the former prediction of a weak effect. Experiment I tested the latter prediction of a strong effect using rats in a conditioned emotional response paradigm, and found no evidence that the pairings made the neutral stimulus excitatory. Experiment II replicated Rescorla's results, but showed that even on a relearning test the experimental group learned no faster than a novel stimulus control group.     

Local intracortical circuitry not only for feature binding but also for rapid neuronal responses

Neurons of primary sensory cortices are known to have specific responsiveness to elemental features. To express more complex sensory attributes that are embedded in objects or events, the brain must integrate them. This is referred to as feature binding and is reflected in correlated neuronal activity. We investigated how local intracortical circuitry modulates ongoing-spontaneous neuronal activity, which would have a great impact on the processing of subsequent combinatorial input, namely, on the correlating (binding) of relevant features. We simulated a functional, minimal neural network model of primary visual cortex, in which lateral excitatory connections were made in a diffusive manner between cell assemblies that function as orientation columns. A pair of bars oriented at specific angles, expressing a visual corner, was applied to the network. The local intracortical circuitry contributed not only to inducing correlated neuronal activation and thus to binding the paired features but also to making membrane potentials oscillate at firing-subthreshold during an ongoing-spontaneous time period. This led to accelerating the reaction speed of principal cells to the input. If the lateral excitatory connections were selectively (instead of “diffusively”) made, hyperpolarization in ongoing membrane potential occurred and thus the reaction speed was decelerated. We suggest that the local intracortical circuitry with diffusive connections between cell assemblies might endow the network with an ongoing subthreshold neuronal state, by which it can send the information about combinations of elemental features rapidly to higher cortical stages for their full and precise analyses.     

Excitation and hedonic valence in the effect of erotica on motivated Intermale aggression

The excitatory potential (low, high), the hedonic valence (negative, positive), and the type of content (erotic, non-erotic) of visual stimuli were varied in a factorial design. Male subjects were provoked by a same-sex peer, exposed to communication or, in a no-exposure control, made to wait for a period of time equal to that of communication exposure, and then provided with an opportunity to retaliate against their annoyer. High excitatory potential and negative hedonic valence were found to combine additively in a facilitative effect on retaliatory aggression. No appreciable differences were found in the effect of excitationally and hedonically matched erotica and non-erotica. Exposure to either arousing and displeasing erotica or non-erotica produced levels of aggression significantly above the level associated with the no-exposure control. Exposure to comparatively non-arousing and pleasing erotica or non-erotica failed to reduce aggression, however. The findings were considered to support a model that projects the effect of erotica on retaliatory aggression as a joint function of their excitatory potential and their hedonic valence.     

Direction of gaze and emergence of speech in the second year

Orienting to the right member of a pair of identical pictures increased monotonically with age in a longitudinal sample of 14 infants seen monthly from 13 to 22 months. The magnitude of the correlation between this orientation bias and a measure of language development also rose with age reaching a peak at 20 months and then declining. It was suggested that the acceleration of vocabulary and maturational changes in the central nervous system that occur between 16 and 22 months are associated with a special excitatory state in the temporal cortex of the left hemisphere.     

Contingency bias in probability judgement may arise from ambiguity regarding additional causes

We tested whether preventive and generative reasoning processes are symmetrical by keeping the training and testing of preventive (inhibitory) and generative (excitatory) causal cues as similar as possible. In Experiment 1, we extinguished excitors and inhibitors in a blocking design, in which each extinguished cause was presented in compound with a novel cause, with the same outcome occurring following the compound and following the novel cause alone. With this novel extinction procedure, the inhibitory cues seemed more likely to lose their properties than the excitatory cues. In Experiment 2, we investigated blocking of excitatory and inhibitory causes and found similar blocking effects. Taken together, these results suggest that acquisition of excitation and inhibition is similar, but that inhibition is more liable to extinguish with our extinction procedure. In addition, we used a variable outcome, and this enabled us to test the predictions of an inferential reasoning account about what happens when the outcome level is at its minimum or maximum (De Houwer, Beckers, & Glautier, 2002). We discuss the predictions of this inferential account, Rescorla and Wagner's (1972) model, and a connectionist model—the auto-associator.     

Lithium-mediated disruptions of latent inhibition: Overshadowing by the unconditioned stimulus in flavor conditioning

In a series of experiments, the ability of a single lithium preexposure to disrupt CS effectiveness was assessed using a latent inhibition procedure. Lithium preexposure administered proximal (90 min) to a saccharin familiarization trial reduced latent inhibition whereas a similar administration more distal (360 min) to flavor familiarization failed to do so. Additional experiments demonstrated that this socalled “US overshadowing” effect was not attributable to sensitization (Experiment 2), excitatory backward conditioning (Experiment 3), or state dependency (Experiment 4). The implications of US overshadowing for proximal US-preexposure effects are discussed.     

Distributed memory and the representation of general and specific information

We describe a distributed model of information processing and memory and apply it to the representation of general and specific information. The model consists of a large number of simple processing elements which send excitatory and inhibitory signals to each other via modifiable connections. Information processing is thought of as the process whereby patterns of activation are formed over the units in the model through their excitatory and inhibitory interactions. The memory trace of a processing event is the change or increment to the strengths of the interconnections that results from the processing event. The traces of separate events are superimposed on each other in the values of the connection strengths that result from the entire set of traces stored in the memory. The model is applied to a number of findings related to the question of whether we store abstract representations or an enumeration of specific experiences in memory. The model simulates the results of a number of important experiments which have been taken as evidence for the enumeration of specific experiences. At the same time, it shows how the functional equivalent of abstract representations--prototypes, logogens, and even rules--can emerge from the superposition of traces of specific experiences, when the conditions are right for this to happen. In essence, the model captures the structure present in a set of input patterns; thus, it behaves as though it had learned prototypes or rules, to the extent that the structure of the environment it has learned about can be captured by describing it in terms of these abstractions.     

胼胝体调节大脑两半球相互作用的机制

胼胝体是哺乳动物脑内最大的白质结构,不仅可以在大脑两半球间传递信息,也能调节半球间的相互作用,“抑制模型”和“兴奋模型”是当前解释胼胝体调节机制的主要模型.前者假设,胼胝体对半球间的信息传递起抑制作用,表现为优势半球的功能增强,非优势半球的活动抑制,因而可以提高半球加工的独立性和功能不对称性;后者则认为,胼胝体对半球间信息传递起促进作用,导致两半球同时性活动,并增强其功能连接性,因而可以降低半球的功能不对称性,有利于半球间的信息共享与功能整合.近期的研究显示,胼胝体并不是一个结构与功能的单一体,而是包含了在空间与时间上既分离又互动的多通道信息加工复合体.抑制与兴奋信息可以通过胼胝体的不同空间通道以不同的速度在半球间进行传递,并受到任务计算类型与复杂性的调节,因此,胼胝体的抑制与兴奋的协同可以调节两半球的动态相互作用.     

Initial excitatory conditioning with the truly random control procedure in rats: The effects of density of the conditioned stimulus

The present experiments were designed to test whether initial excitatory conditioning to a stimulus was obtained, using a within-subject design of the truly random control (TRC) procedure, and to examine the effects of the density of the conditioned stimulus on it. In Experiment 1, the effect of the three levels of CS density (50%, 25%, 20%) was assessed at six different stages of training, using the conditioned suppression of licking in rats. Although all of the groups given the TRC procedure showed evidence of initial excitatory conditioning, it was more marked in the group with the highest CS density than in the other groups. Experiment 2 confirmed the results of Experiment 1, using a between-subject design. The findings are in line with predictions from the Rescorla-Wagner model, and are discussed with reference to other contemporary theories of associative learning.     

Stressor Controllability and Learned Helplessness Research in the United States: Sensitization and Fatigue Processes

Recent work in the learned helplessness paradigm suggests that neuronal sensitization and fatigue processes are critical to producing the behavioral impairment that follows prolonged exposure to an unsignaled inescapable stressor such as a series of electric tail shocks. Here we discuss how an interaction between serotonin (5-HT) and corticosterone (CORT) sensitizes GABA neurons early in the pretreatment session with inescapable shock. We propose that this process eventually depletes GABA, thus removing an important form of inhibition on excitatory glutamate transmission in the amygdala, hippocampus, and frontal cortex. When rats are re-exposed to shock during shuttle-escape testing 24 hrs later, the loss of inhibition (as well as other excitatory effects) results in unregulated excitation of glutamate neurons. This state of neuronal over-excitation rapidly compromises metabolic homeostasis. Metabolic fatigue results in compensatory inhibition by the nucleoside adenosine, which regulates neuronal excitation with respect to energy availability. The exceptionally potent form of inhibition associated with adenosine receptor activation yields important neuroprotective benefits under conditions of metabolic failure, but also precludes the processing of information in fatigued neurons. The substrates of adaptive behavior are removed; performance deficits ensue.