Strain and gender specific effects in the forced swim test: effects of previous stress exposure

The chronic mild stress (CMS) procedure was developed in rodents to target anhedonia, the core symptom of depressive melancholia. Stress exposure has been shown to induce a variety of physiological, biochemical and behavioral alterations associated with depression, although its anhedonic consequences as indexed by either sucrose intake and preference or thresholds for brain stimulation reward are less reliably observed. In the present study, we assessed the effects of six weeks of CMS on the latter measure in two strains of male and female rats subsequently challenged with an acute psychophysical stressor, forced swimming; their behavior in the swimming cylinder was evaluated on two consecutive days. While brain stimulation reward thresholds and response rates were unchanged by CMS exposure, significant differences in forced swim behaviors were observed between male control and CMS groups. In particular, male Long Evans rats with a history of CMS showed the largest decrease in the duration of active behaviors on the second test day, a pattern less evident in the Sprague-Dawley strain of rats, or in any of the female groups. The results suggest that the effects of depressogenic manipulations are strain and gender dependent, with male Long Evans rats most susceptible, as demonstrated by the selective reduction of struggling behaviors. Inclusion of multiple measures, including the forced swim test, would provide a better understanding of the psychopathological profile engendered by chronic exposure to mild stressors and its genetic specificity.     

Satiation, capacity, and within-session responding

Responding may change substantially over the course of a session (McSweeney, Hinson, & Cannon, 1996). The role of satiation in this effect was investigated in three experiments. Experiment 1 showed that the capacity of pigeons to consume milo over a 1-hr period was relatively stable across three different methods of measurement. In Experiment 2, pigeons were divided into two groups that differed in their capacity based on one of those measures. Key pecking was then reinforced under a variable-interval 30-s schedule with hopper durations of 2 or 5 s. According to the satiation hypothesis, subjects with small capacities should satiate faster and therefore show greater decreases in food-reinforced responding than would subjects with larger capacities. The results confirmed this prediction and showed that the magnitudes of within-session decreases were better predicted by the amount an animal consumed relative to its capacity than by absolute amount alone. In Experiment 3, each pigeon was prefed 0, 5, 15, or 25 g of milo prior to each session. Consistent with the satiation hypothesis, increases in prefeeding produced lower overall response rates in the smaller capacity subjects than in the larger capacity subjects at each level of prefeeding. These experiments demonstrate the importance of a new variable in the control of behavior, and provide a recommended technique for its measurement.     

Manipulating smoking motivation: impact on an electrophysiological index of approach motivation.

A chief goal of this research was to determine whether stimuli and events known to enhance smoking motivation also influence a physiological variable with the potential to index approach motivation. Asymmetry of electroencephalographic (EEG) activity across the frontal regions of the 2 hemispheres (left minus right hemisphere activation) was used to index approach motivation. In theory, if EEG asymmetry sensitively indexes approach dispositions, it should be influenced by manipulations known to affect smoking motivation, that is, exposure to smoking cues and tobacco deprivation. Seventy-two smokers participated in this research and were selectively exposed to a smoking-anticipation condition (cigarettes plus expectation of imminent smoking) following either 24 hr of tobacco withdrawal or ad libitum smoking. Results indicated that EEG asymmetry was increased by smoking anticipation and that smoking itself reduced EEG asymmetry. Results also suggested that smoking anticipation increased overall (bihemispheric) EEG activation. Results were interpreted in terms of major theories of drug motivation.     

Capturing Entrepreneurial Values

This research was designed to identify entrepreneurial value orientations by comparing them with the value orientations of professional managers. The SYMLOG values measuring instrument was administered in Thailand to Thai entrepreneurs ( n = 55) and Thai professional managers ( n = 200). Results show that the value orientation of the entrepreneurs differed significantly from that of professional managers on several dimensions, particularly with regard to those elements that almost always contribute to teamwork effectiveness. Implications for training and staffing are discussed.     

The impact of empathy and reappraisal on emotional intensity recognition

Empathy represents a fundamental ability that allows for the creation and cultivation of social bonds. As part of the empathic process, individuals use their own emotional state to interpret the content and intensity of other people’s emotions. Therefore, the current study was designed to test two hypotheses: (1) empathy for the pain of another will result in biased emotional intensity judgment; and (2) changing one’s emotion via emotion regulation will modulate these biased judgments. To test these hypotheses, in experiment one we used a modified version of a well-known task that triggers an empathic reaction We found that empathy resulted in biased emotional intensity judgment. To the best of our knowledge, this is the first demonstration of a bias in the recognition of emotional facial expressions as a function of empathy for pain. In experiment two, we replicated these findings in an independent sample, and further found that this biased emotional intensity judgment can be moderated via reappraisal. Taken together, our findings suggest that the novel task used here can be employed to further explore the relation between emotion regulation and empathy.     

Reducing self-control by weakening belief in free will

Believing in free will may arise from a biological need for control. People induced to disbelieve in free will show impulsive and antisocial tendencies, suggesting a reduction of the willingness to exert self-control. We investigated whether undermining free will affects two aspects of self-control: intentional inhibition and perceived self-control. We exposed participants either to anti-free will or to neutral messages. The two groups (no-free will and control) then performed a task that required self-control to inhibit a prepotent response. No-free will participants showed less intentional inhibitions than controls, suggesting a reduction of self-control. We assessed perceived self-control by asking participants whether the response resulted from a deliberate intention or from an impulsive reaction. Perceived self-control was lower in the no-free will group than in control group. Our findings show that undermining free will can degrade self-control and provide insights into how disbelieving in free will leads to antisocial tendencies.     

Affect intensity in voice recognized by tree shrews (Tupaia belangeri)

Shared acoustic cues in speech, music, and nonverbal emotional expressions were postulated to code for emotion quality and intensity favoring the hypothesis of a prehuman origin of affective prosody in human emotional communication. To explore this hypothesis, we examined in playback experiments using a habituation-dishabituation paradigm whether a solitary foraging, highly vocal mammal, the tree shrew, is able to discriminate two behaviorally defined states of affect intensity (low vs. high) from the voice of conspecifics. Playback experiments with communication calls of two different types (chatter call and scream call) given in the state of low affect intensity revealed that habituated tree shrews dishabituated to one call type (the chatter call) and showed a tendency to do so for the other one (the scream call), both given in the state of high affect intensity. Findings suggest that listeners perceive the acoustic variation linked to defined states of affect intensity as different within the same call type. Our findings in tree shrews provide first evidence that acoustically conveyed affect intensity is biologically relevant without any other sensory cue, even for solitary foragers. Thus, the perception of affect intensity in voice conveyed in stressful contexts represents a shared trait of mammals, independent of the complexity of social systems. Findings support the hypothesis that affective prosody in human emotional communication has deep-reaching phylogenetic roots, deriving from precursors already present and relevant in the vocal communication system of early mammals.     

Exploring the role of primary and supplementary motor areas in simple motor tasks with fNIRS

Studies employing functional magnetic resonance imaging (fMRI) have highlighted a covariation between the amplitude of hemodynamic responses recorded in primary and supplementary motor areas (M1 and SMA) and the duration of a motor task. A subset of these studies have hinted to a possible functional dissociation between processing carried out in these areas, with SMA primarily involved in action preparation, while M1 involved in action execution. This proposed functional dissociation was explored in the present study using a different technique—functional near-infrared spectroscopy—which enabled a finer-grained monitoring of the temporal characteristics of the hemodynamic response compared to fMRI. Here, hemodynamic responses in M1 and SMA were recorded in 7 participants during a right-finger-tapping task of short (1 s) or long (3 s) duration. Hemodynamic responses of larger amplitude were recorded from both contralateral M1 and SMA during long-duration than short-duration tapping. Furthermore, the analysis of the temporal profiles of these responses revealed a more sustained and prolonged activity for long-duration versus short-duration tapping in M1, but not in SMA. Rather than functionally dissociable areas, the present results are more compatible with the hypothesis that M1 and SMA subserve different, though strongly interacting, functional subroutines subtended in motor task preparation and execution.     

A test of the circumvention-of-limits hypothesis in scientific problem solving: the case of geological bedrock mapping

Sources of individual differences in scientific problem solving were investigated. Participants representing a wide range of experience in geology completed tests of visuospatial ability and geological knowledge, and performed a geological bedrock mapping task, in which they attempted to infer the geological structure of an area in the Tobacco Root Mountains of Montana. A Visuospatial Ability × Geological Knowledge interaction was found, such that visuospatial ability positively predicted mapping performance at low, but not high, levels of geological knowledge. This finding suggests that high levels of domain knowledge may sometimes enable circumvention of performance limitations associated with cognitive abilities.