Improving balance by performing a secondary cognitive task

Contrary to general findings in the attention and memory literature, some studies have shown that performing a secondary cognitive task produces an improvement in balance performance. The purpose of the present experiment was to investigate under what condition such an improvement would occur. Young and older adults were asked to hold as still as possible on a platform that measured sway while performing or not performing the encoding phase of the Brooks' (1967) spatial or non‐spatial memory task. The difficulty of maintaining balance was manipulated by varying the availability of visual input and sway‐referenced motion of the platform. Sway scores were computed based on the distance between the individual pressure centres and the average centre of pressure during each 20‐s trial. The results indicated that both the spatial and non‐spatial memory tasks improved balance for older adults under the most difficult balance condition.     

Effects of anxiety sensitivity on emotional response to a stress task

The purpose of this investigation was to further define the role of anxiety sensitivity, in relation to physiological arousal and the cognitive perception of anxiousness, as a determinant of anxiety. One hundred and thirty-two undergraduates at an urban university served as subjects. Two physiological measures of arousal and two cognitive measures of anxiety were used following an anxiety inducing task (mental arithmetic). The general expectation, which was supported, was that individual differences in anxiety sensitivity levels are more closely related to subjects' reported anxiousness in stressful conditions than are the actual physiological changes. Additionally, anxiety sensitivity was related to poststress levels of anxiety whereas trait anxiety was only related to pre- and postrelaxation levels of anxiety. Implications of the findings are addressed.     

Directional learning,but no spatial mapping by rats performing a navigational task in an inverted orientation

Previous studies have identified neurons throughout the rat limbic system that fire as a function of the animal’s head direction (HD). This HD signal is particularly robust when rats locomote in the horizontal and vertical planes, but is severely attenuated when locomoting upside-down (Calton & Taube, 2005). Given the hypothesis that the HD signal represents an animal’s sense of directional heading, we evaluated whether rats could accurately navigate in an inverted (upside-down) orientation. The task required the animals to find an escape hole while locomoting inverted on a circular platform suspended from the ceiling. In Experiment 1, Long-Evans rats were trained to navigate to the escape hole by locomoting from either one or four start points. Interestingly, no animals from the 4-start point group reached criterion, even after 29 days of training. Animals in the 1-start point group reached criterion after about six training sessions. In Experiment 2, probe tests revealed that animals navigating from either 1- or 2-start points utilized distal visual landmarks for accurate orientation. However, subsequent probe tests revealed that their performance was markedly attenuated when navigating to the escape hole from a novel start point. This absence of flexibility while navigating upside-down was confirmed in Experiment 3 where we show that the rats do not learn to reach a place, but instead learn separate trajectories to the target hole(s). Based on these results we argue that inverted navigation primarily involves a simple directional strategy based on visual landmarks.     

Bimanual interference in children performing a dual motor task

The present study addressed the development of bimanual interference in children performing a dual motor task, in which each hand executes a different task simultaneously. Forty right-handed children (aged 4, 5-6, 7-8 and 9-11years, ten in each age group) were asked to perform a bimanual task in which they had to tap with a pen using the non-preferred hand and simultaneously trace a circle or a square with a pen using the preferred hand as quickly as possible. Tapping and tracing were also performed unimanually. Differences between unimanual and bimanual performance were assessed for number of taps, length of tap trace and mean tracing velocity. It was assumed that with increasing age, better bimanual coordination would result in better performance on the dual task showing less intermanual interference. The results showed that tapping and tracing performance increased with age, unimanually as well as bimanually, consistent with developmental advancement. However, the percentage of intermanual interference due to bimanual performance was not significantly different in the four age groups. Although performing the dual task resulted in mutual intermanual interference, all groups showed a significant effect of tracing shape. More specifically, all age groups showed a larger percentage decrease in tracing velocity when performing the circle compared to the square in the dual task. The present study reveals that children as young as four years are able to coordinate both hands when tapping and tracing bimanually.     

Effects of glucose on scopolamine-induced learning deficits in rats performing the Morris water maze task

In order to assess the effects of glucose on drug-induced spatial learning deficits, three experiments were conducted using the Morris water maze. Scopolamine and glucose were injected ip at various stages of training. Rats of Wistar strain served as subjects. In Experiment 1, scopolamine (0.4 mg/kg) and 10, 100, or 500 mg/kg of glucose were administered every day from the start of training, and the effect on acquisition was evaluated. In Experiment 2, scopolamine and 100 or 500 mg/kg of glucose were administered after 6 days of training, and the effect on performance was assessed. In Experiment 3, scopolamine and 500 mg/kg of glucose were injected after 2 days of training, and the effect on the following trial was tested. In all experiments, scopolamine impaired acquisition/performance of the task. Glucose at 500 mg/kg showed a significant enhancing effect on acquisition regardless of scopolamine injection only when injected daily from the start of training (Experiment 1). Glucose injected after the performance has reached asymptote (Experiment 2) did not affect performance, and glucose in the middle of training showed a slight but insignificant enhancing effect (Experiment 3). These results may suggest that the effect of glucose changes as a function of the degree of learning of the spatial learning task. The possibility of task specificity of the glucose effect was also discussed in relation to the cholinergic systems and local cerebral glucose utilization.     

Effects of varying the amount of preexposure to spatial cues on a subsequent navigation task

In each of two experiments rats were preexposed to four compound landmarks (AX, BX, CX, and DX) one at a time; they were then trained to find a submerged platform located in a fixed position in a swimming pool using these same landmarks. When the preexposure was SHORT (4 sessions) it facilitated subsequent learning (a perceptual learning effect), whereas when rats were given a LONG preexposure phase (8 sessions) this facilitatory effect disappeared. EXTRA-LONG preexposure (16 sessions) reversed the facilitatory effect-that is to say, we observed retarded learning. The results show that rats' ability to navigate towards an invisible goal is affected by the length of their preexposure to the spatial cues that signal the location of the goal. These data are consistent with an associative analysis of the swimming pool navigation task.     

Effects of environmental enrichment on cognitive performance of pigs in a spatial holeboard discrimination task

This study investigated the effects of environmental enrichment on the cognitive performance of female conventional farm (growing) pigs in a spatial holeboard task. Ten pairs of littermates matched for weight were used. From each litter, one piglet was randomly assigned to a barren environment; the other was assigned to an enriched environment from 4 weeks of age. The enriched environment was double the size of the barren environment, had a floor covered with straw, a rooting area filled with peat, and one of the four different enrichment toys which were exchanged daily. Starting at 11 weeks of age, all pigs were tested in a spatial holeboard discrimination task in which 4 out of 16 holes were baited. Furthermore, basal salivary cortisol levels of all pigs were determined after the end of all testing. All pigs were able to acquire the pattern of baited holes (acquisition phase, 40 trials) and the diagonally mirrored pattern (reversal phase, 20 trials). During the acquisition phase, the reference memory performance of the enriched-housed pigs was better than that of their barren-housed littermates, i.e. they reduced visits to the unbaited set of holes. During the reversal phase, enriched-housed pigs had a better general working memory performance than the barren-housed pigs as indicated by reduced revisits to holes already visited during a trial, irrespective of whether they were of the baited or the unbaited set. The enriched-housed pigs also searched for the hidden bait faster during both phases. The environments did not affect basal salivary cortisol levels. In conclusion, environmental enrichment slightly improved the cognitive performance of pigs in a spatial learning task. We hypothesise that the long period of habituation to and testing in the holeboard acted as enrichment that partially reduced the effects of barren housing.     

Influence of motivation and task difficulty on gender discrimination judgements

A study is reported examining how motivation to detect salary discrimination influences its detection depending on the difficulty of the detection task. Subjects were presented with information about the qualifications and salaries of female and male managers in 10 departments of a hypothetical company. This information was created so that female managers were undercompensated relative to their qualifications. The main dependent variable was subjects' ratings of gender discrimination. Independent variables were motivation and task difficulty. Based on Hull's drive theory an interaction effect was predicted and found: when the judgement task was easy, more gender discrimination was detected when motivation to detect discrimination was high rather than low, whereas when the judgement task was difficult, more gender discrimination was detected when motivation to detect discrimination was low rather than high. © 1998 John Wiley & Sons, Ltd.     

A facilitative role for corticosterone in the acquisition of a spatial task under moderate stress

Emotionally charged experiences alter memory storage via the activation of hormonal systems. Previously, we have shown that compared with rats trained for a massed spatial learning task in the water maze in warm water (25°C), animals that were trained in cold water (19°C) performed better and showed higher levels of the stress hormone corticosterone. Here, we examined whether manipulating the levels of corticosterone can determine the strength of spatial information acquisition and retention. Rats were injected with metyrapone (25, 50, and 75 mg/kg, i.p.) or with corticosterone (10 and 25 mg/kg, i.p.) and trained in a massed spatial task in either cold (19°C) or warm (25°C) water. We found that whereas animals injected with vehicle performed well in the spatial task in cold water (moderate stress), rats injected with the intermediate metyrapone dose showed impairment in performance. Moreover, whereas animals injected with vehicle on average did not perform well in warm water (mild stress), rats injected with the lower corticosterone dose showed improvement in performance in warm water. These two mirror experiments of corticosterone blockade and enhancement strongly suggest that corticosterone is instrumental in the acquisition and retention of the spatial learning task.     

The impact of task difficulty expectations on intrinsic motivation

Two studies investigated expectations of task difficulty induced prior to task involvement and their impact upon an individual's subsequent intrinsic interest. Expectations of task difficulty were manipulated through easy/hard instructions by the experimenters. Interest, but not performance, varied as function of expected task difficulty, with “easy” eliciting greater interest than “hard” instructions. The generality of this finding was supported by its demonstration in studies utilizing different experimenters (male, female), subject populations (children, college), and tasks (perceptual-motor, cognitive).