Ontogeny of spontaneous locomotor activity in rabbit, rat, and guinea pig.

Postnatal locomotor activity was investigated in rabbit, rat, and guinea pig. A peak was found in this behavior at 5 days of age in the rabbit and, in confirmation of earlier studies, at 15-20 days in the rat. Neonatal guinea pigs showed no variation in activity levels due to age. The guinea pig is born at an advanced stage of neural maturation in comparison with the rat, and the rabbit is born at an intermediate stage. This difference accounts for the observed variations in postnatal activity profiles if it is assumed that the behavioral peak coincides with the transition from a stage of primarily mesencephalic arousal system maturation to a stage of primarily diencephalic and telencephalic inhibitory system maturation.     

Arousal as an explanation for differences in rats selectively bred for differential alcohol sensitivity

A common error made by behavior genetics researchers is breeding two lines for differences in central arousal rather than for a specific behavioral feature. Two lines of rats (Riley, Freed, & Lester, 1976) were selectively bred for locomotor impairment in response to a subhypnotic dose (1.5 g/kg) of ethanol. These lines (designated "most affected" and "least affected") were compared in a variety of tests and showed differences in a number of phenotypic traits in addition to locomotor impairment to ethanol. The published findings have been interpreted in light of a hypothesis suggesting adventitiously selected differences in central arousal between the two lines. This interpretation showed that their usefulness as animal models of alcoholism is seriously compromised.     

Spatiotemporal dynamics of long-term potentiation in rat insular cortex revealed by optical imaging

Long-term potentiation (LTP) of the gustatory cortex (GC), a part of the insular cortex (IC) around the middle cerebral artery, is a key process of gustatory learning and memory, including conditioned taste aversion learning. The rostral (rGC) and caudal GC (cGC) process different tastes; the rGC responds to hedonic and the cGC responds to aversive tastes. However, plastic changes of spatial interaction of excitatory propagation between the rGC and cGC remain unknown. The present study aimed to elucidate spatiotemporal profiles of excitatory propagation, induced by electrical stimulation (five train pulses) of the rGC/cGC before and after LTP induction, using in vivo optical imaging with a voltage-sensitive dye. We demonstrated that tetanic stimulation of the cGC induced long-lasting expansion of the excitation responding to five train stimulation of the cGC, and an increase in amplitude of optical signals in the IC. Excitatory propagation after LTP induction spread preferentially toward the rostral IC: the length constant (λ) of excitation, obtained by fitting optical signals with a monoexponential curve, was increased to 121.9% in the rostral direction, whereas λ for the caudal, dorsal, and ventral directions were 48.9%, 44.2%, and 62.5%, respectively. LTP induction was prevented by pre-application of D-APV, an NMDA receptor antagonist, or atropine, a muscarinic receptor antagonist, to the cortical surface. In contrast, rGC stimulation induced only slight LTP without direction preference. Considering the different roles of the rGC and cGC in gustatory processing, these characteristic patterns of LTP in the GC may be involved in a mechanism underlying conversion of palatability.     

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.     

On yawning and its functions

The forms and behavioral correlates of yawning are described, and the phylogenetic and ontogenetic aspects of the act are examined with particular attention to its possible functions. Much evidence supports the view that yawning is an important mediator of behavioral arousal levels, a view that is further strengthened by a review of endocrine, neurotransmitter, and pharmacological mechanisms of yawning: A major function of yawning appears to involve maintenance or increase of arousal when environments provide relatively little stimulation.     

Neural basis of individual differences in impulsivity: contributions of corticolimbic circuits for behavioral arousal and control

The objective of the current study was to analyze the neural correlates of behavioral arousal and inhibitory control as they relate to individual differences in impulsivity via well-established functional MRI amygdala reactivity and prefrontal inhibitory control paradigms in healthy adult subjects. Impulsivity correlated positively with activity of the bilateral ventral amygdala, parahippocampal gyrus, dorsal anterior cingulate gyrus (BA 32), and bilateral caudate. Conversely, impulsivity correlated negatively with activity of the dorsal amygdala and ventral prefrontal cortex (BA 47). Together, these findings suggest that dispositional impulsivity is influenced by the functional interplay of corticolimbic behavioral arousal and control circuits.     

Sensitization as a mechanism for multiple chemical sensitivity: relationship to evolutionary theory

Multiple chemical sensitivity (MCS) is a disorder in humans attributed to prior chemical exposure. Sensitization is an amplification of neuronal responsiveness that elicits increased behavioral responding to stimuli, and occurs in a recently developed rat model of MCS. Rats were exposed to repeated formaldehyde (Form) and their response in three behavioral tests, including locomotor activity after a cocaine challenge, conditioned fear, and behavioral avoidance of Form, was assessed. In all three tests, rats demonstrated sensitized behaviors, implicating amplified responding within specific limbic brain regions. Evolutionary theory in the context of MCS specifies how the behavioral strategies of those with MCS are consistent with the notion that their self-perceived sense of survival and reproductive fitness may be threatened by chemical exposures. This behavior may be mediated by the same limbic brain regions that become sensitized after repeated chemical exposure in animals.     

Effects of Action Video Game Experience on Change Detection

Reflected sounds are often treated as an acoustic problem because they produce false localization cues and decrease speech intelligibility. However, their properties are shaped by the acoustic properties of the environment and therefore are a potential source of information about that environment. The objective of this study was to determine whether information carried by reflected sounds can be used by listeners to enhance their awareness of their auditory environment. Twelve listeners participated in two auditory training tasks in which they learned to identify three environments based on a limited subset of sounds and then were tested to determine whether they could transfer that learning to new, unfamiliar sounds. Results showed that significant learning occurred despite the task difficulty. An analysis of stimulus attributes suggests that it is easiest to learn to identify reflected sound when it occurs in sounds with longer decay times and broadly distributed dominant spectral components.     

Rats’ novel object interaction as a measure of environmental familiarity

Environmental familiarization is a learning phenomenon embedded within most tasks used to study learning and motivation. Given its prevalence there is surprisingly little systematic behavioral research on factors affecting familiarization. The six experiments reported in the present report used rats’ tendency to interact more with a novel object in a familiar than in a novel environment as a measure of environmental familiarization. We found that 3 min of exposure to the environment was sufficient to increase object interaction above unfamiliar controls even when testing occurred up to 48 h after initial exposure to the environment; 1 or 1.5 min of exposure was not sufficient. Also, in the brief 2 min test, 10 min of environment exposure did not appear to increase object interaction above the 3-min condition. The 3-min of environment exposure was sufficient for familiarization whether environment exposure occurred in one 3 min placement or two 1.5 min placements. Environmental familiarization as measured by object interaction was also sensitive to ‘interference’ manipulations. That is, a distinct object present during initial exposure to the environment produced a level of object interaction in testing comparable to an unfamiliar control. Similarly, exposure to a second distinct alternate environment immediately after, but not before, initial exposure to the test environment partially disrupted environmental familiarization. In sum, object interaction might serve as a useful measure for studying processes mediating environmental familiarity.     

No effects of transcranial direct current stimulation on visual evoked potential and peak gamma frequency

Cognitive Processing - Evidence suggests that the visual evoked potential (VEP) and gamma oscillations elicited by visual stimuli reflect the balance of excitatory and inhibitory (E-I) cortical...     

Sensation seeking and arousal systems

This article discusses the overgeneralized construct of ‘arousal’, pointing out some of the problems of speaking of it as mediated by a single system. The literature and current studies of the orienting and defensive reflexes, and augmenting-reducing of the cortical evoked potential in relation to the sensation-seeking (SS) trait are discussed. The data relating platelet MAO and CSF, plasma and urinary measures of bioamines, their metabolites and enzymes, to SS, extraversion and behavioral indices are also treated. Relationships between arousal measured in different systems are pointed out. Personality theory is seen as a vehicle for understanding the organization of arousal systems in adaptation to environmental stimulation.     

Specific modes of anxiety and arousal

Although it may be oversimplistic to regard the cognitive and behavioral effects of anxiety as simply being due to associated increases in arousal, this is essentially what many theories of anxiety do. Indeed, some theorists go so far as to equate anxiety with arousal. This experiment questions the appropriateness of this assumption by showing that increases in arousal do not necessarily accompany increases in anxiety. First, a 14-item arousal questionnaire was validated using factor analytic and multivariate analysis of variance techniques. Two factors were identified: cognitive activation and somatic activation. The validated questionnaire was then administered to eight very experienced rock-climbers in six different environments, together with a cognitive-somatic anxiety questionnaire. Heartrate and oral temperature were also measured. The six environments were: morning and evening; during a prolonged “bouldering” session; and immediately prior to leading pitches at two grade, one grade and zero grades below their leading capacity. The experimental hypothesis that activation would be increasingly impaired in the latter two conditions while anxiety would continue to increase, was confirmed by a multivariate analysis of variance (p<0.001). The results are interpreted as supporting the sort of two-factor theory of arousal that has been proposed by Gray.     

Prefrontal cortex regulates inhibition and excitation in distributed neural networks.

Prefrontal cortex provides both inhibitory and excitatory input to distributed neural circuits required to support performance in diverse tasks. Neurological patients with prefrontal damage are impaired in their ability to inhibit task-irrelevant information during behavioral tasks requiring performance over a delay. The observed enhancements of primary auditory and somatosensory cortical responses to task-irrelevant distractors suggest that prefrontal damage disrupts inhibitory modulation of inputs to primary sensory cortex, perhaps through abnormalities in a prefrontal-thalamic sensory gating system. Failure to suppress irrelevant sensory information results in increased neural noise, contributing to the deficits in decision making routinely observed in these patients. In addition to a critical role in inhibitory control of sensory flow to primary cortical regions, and tertiary prefrontal cortex also exerts excitatory input to activity in multiple sub-regions of secondary association cortex. Unilateral prefrontal damage results in multi-modal decreases in neural activity in posterior association cortex in the hemisphere ipsilateral to damage. This excitatory modulation is necessary to sustain neural activity during working memory. Thus, prefrontal cortex is able to sculpt behavior through parallel inhibitory and excitatory regulation of neural activity in distributed neural networks.     

Genetic and environmental etiology of emotional and social behaviors in 5-month-old infant twins: influence of the social context

The study investigated the genetic and environmental contributions to individual differences in measures of socioemotional reactivity and emotion regulation with a sample of 115 monozygotic (MZ) and 156 dizygotic (DZ) 5-month-old twin pairs. Twins' zygosity was determined by a combination of DNA typing and physical similarity. Twins' behaviors (motor activity level, social gaze, gaze aversion, positive expression, negative expression, and self-comfort) were videotaped in a laboratory while infants were presented televised sequences of neutral and happy emotional expressions posed by their mother (familiar condition) and a female stranger (unfamiliar condition). Regardless of the social context, the findings based on model-fitting analyses indicated that nonshared environmental influences explained most of the variance of behavioral data. However, there was evidence that motor activity level (an index of emotional arousal) and the latency and frequency of gaze aversion (an index of emotional regulation) were best represented by a model incorporating both additive genetic and nonshared environmental (i.e., AE) influences when infants were exposed to the unfamiliar adult (heritability estimates ranging from 19% to 31%). The results suggest the importance of nonshared environmental influences during early infancy and stress the role of social context for revealing moderate genetic contributions to individual differences in emotional arousal and emotion regulation.     

Incidental learning as a function of anticipated task difficulty

Three experiments were conducted to demonstrate the effects of motivational arousal, due to anticipated task difficulty, on retention of familiar and unfamiliar incidental materials. Brehm, Wright, Solomon, Silka, and Greenberg (1983) have provided evidence that motivational arousal in immediate anticipation of a task is a nonmonotonic function of task difficulty, with difficult tasks producing a relatively higher level of motivational arousal than easy or impossible tasks. It was predicted that increased motivational arousal would facilitate retention of incidentally presented familiar materials (presumably more easily retained) and interfere with retention of incidentally presented unfamiliar materials (presumably less easily retained). In Study 1, subjects anticipating either an easy or a difficult task were exposed to familiar and unfamiliar first names. The predicted interaction between task difficulty and familiarity on recall of the first names was reliably supported. In Study 2, an impossible task condition was added. The results indicated that an effective impossible condition had not been created. In a third study designed as a procedural modification of Study 2, the predicted nonmonotonic interaction was found. Theoretical implications are discussed.These experiments were ably conducted by Ralph Young, whose help is gratefuly acknowledged. We would like to express our gratitude to Jack Brehm for invaluable suggestions concerning this research.     

Stepping up the pressure: arousal can be associated with a reduction in male aggression

The attentional myopia model of behavioral control [Mann and Ward, 2007] was tested in an experiment investigating the relationship between physiological arousal and aggression. Drawing on previous work linking arousal and narrowed attentional focus, the model predicts that arousal will lead to behavior that is relatively disinhibited in situations in which promoting pressures to aggress are highly salient. In situations in which inhibitory pressures are more salient, the model predicts behavior that is relatively restrained. In the experiment, 81 male undergraduates delivered noise-blasts against a provoking confederate while experiencing either high or low levels of physiological arousal and, at the same time, being exposed to cues that served either to promote or inhibit aggression. In addition to supporting the predictions of the model, this experiment provided some of the first evidence for enhanced control of aggression under conditions of heightened physiological arousal. Implications for interventions designed to reduce aggression are discussed.     

Attenuation of amphetamine-stereotypy by mesostriatal dopamine depletion enhances plasma corticosterone: implications for stereotypy as a coping response

The relationship between amphetamine-induced stereotyped behavior and a neuroendocrine index of arousal, plasma corticosterone (CCS), was investigated. 6-Hydroxydopamine lesions of the caudate-putamen, which produced dopamine depletions of 60%, blocked stereotypy and prolonged the elevation in corticosterone associated with d-amphetamine treatment (5 mg/kg). Similar dopamine depleting lesions of the nucleus accumbens, which attenuated the locomotor, but not the stereotypic, response to AMPH did not have this effect on CCS. This pattern of results supports the hypothesis that stereotypy has a coping function which may serve to alter arousal and further suggests important differences between the nigrostriatal and mesolimbic dopamine projections in modulating the responsiveness of the neuroendocrine system. These results have implications for understanding the function of behavioral stereotypies common to a number of psychopathological conditions, including schizophrenia and childhood autism.     

Neuropeptide S: a novel modulator of stress and arousal

Neuropeptide S (NPS) is a recently identified bioactive peptide that modulates stress and arousal. NPS is expressed in a few discrete nuclei in the brainstem, such as the pericoerulear (locus coeruleus (LC)) area and the parabrachial nucleus. NPS activates its cognate G protein-coupled receptor at low nanomolar agonist concentrations and induces elevation of intracellular Ca2+ and cAMP, therefore acting as an excitatory transmitter. The NPS receptor is widely expressed in the brain, including regions known to regulate stress responses such as hypothalamus, thalamus, amygdala and limbic cortex. We have recently reported that the NPS system can modulate stress responses and induce wakefulness based on a battery of behavioral tests. Activation of NPS receptors induces arousal and reduces all sleep stages. At the same time, NPS produces anxiolytic-like effects in rodents. These studies indicate that the NPS system has a unique pharmacological profile to promote both anxiolytic and arousal effects. NPS might interact with other hypothalamic neuropeptide systems that are known to be involved in stress and appetite control and thus might be a valuable target for development of a new class of drugs to treat anxiety disorders.     

Hippocampal EEG and Unit Activity Responses to Modulation of Serotonergic Median Raphe Neurons in the Freely Behaving Rat

Hippocampal EEG, GABAergic interneurons, and principal cells were recorded simultaneously as rats foraged within one of three environments both before and after modulation of serotonergic inputs to the hippocampus. Median raphe microinjections of the 5-HT1a receptor agonist 8-OH-DPAT were made to produce inhibition of serotonergic neurons in this region. Such microinjections produced behavioral arousal and increases in the amplitude of hippocampal EEG theta. Consistent with the pattern of serotonergic innervation of the hippocampus, the GABAergic interneuron population was affected differentially by the microinjections. Principal cells were generally unaffected by the manipulation and maintained robust spatial firing correlates within the foraging environment. The results provide basic data on the relationship between serotonergic median raphe neurons and hippocampal activity in a behaving animal. The data suggest that behavioral responses to manipulation of the serotonergic system are mediated by brain regions other than the hippocampus or are mediated through changes in the activity of hippocampal interneurons.     

Preschoolers' inhibition in their home: relation to temperament

Researchers assessed 58 preschoolers' reactions to an unfamiliar person and unfamiliar objects in their familiar home environment. Children participated in a 30-min procedure designed to elicit behavioral inhibition, including (a) a free-play period with a stranger present, (b) a structured interaction with the stranger, and (c) uncertainty-eliciting tasks. Behaviors representing the child's reactions toward the mother, stranger, and novel objects were coded. Mothers completed a temperament scale. Preschoolers exhibited behaviors indicative of inhibition toward unfamiliar social and nonsocial stimuli; behaviors remained stable across increasingly intrusive episodes. The approach/withdrawal component of temperament was related to behavioral inhibition. Individual differences in mood did not appear to be related to differences in inhibition. Parent reported temperament was related to researcher-observed behaviors.