Chlordiazepoxide impairs the performance of a learned discrimination

Chlordiazepoxide (CDP) (5 mg/kg) administered on four of eight sessions significantly impaired the performance of a previously learned, reinforcement-cued discrimination in male Sprague-Dawley rats. On four interspersed vehicle-injection sessions, the performance of subjects demonstrated immediate recovery and was indistinguishable from that of controls (0 mg/kg). An analysis of response components indicated that the impairment in discrimination performance was due to a "disinhibitory" effect of the drug on responding during "no-go" phases of the task. The results are discussed in the context of similarities and differences in the effect of CDP on performance and acquisition.     

Socially triggered negative affect impairs performance in simple cognitive tasks

The aim of this research was to investigate the influence of a social-evaluative context on simple cognitive tasks. While another person present in the room evaluated photographs of beautiful women or landscapes by beauty/attractiveness, female participants had to perform a combination of digit-categorization and spatial-compatibility task. There, before every trial, one of the women or landscape pictures was presented. Results showed selective performance impairments: the numerical distance effects increased on trials that followed women pictures but only, if another person concurrently evaluated these women pictures. In a second experiment, using the affective priming paradigm, the authors show that female pictures have a more negative connotation when they are concurrently evaluated by another person (social-evaluative context) than when they are not evaluated (neutral context). Together, these results suggest that the social-evaluative context triggers mild negative affective reactions to women pictures which then impair performance in an unrelated task.     

Scaling extrafoveal detection of distortion in a face and grating

Peripheral performance involving simple visual tasks and stimuli can be equated with foveal performance by spatial scaling, whilst more complex tasks and stimuli seem to need additional scaling of image contrast. We therefore determined whether the contrast manipulation needed to compensate for eccentricity-dependent performance changes is due to an increase in stimulus or task difficulty. We measured contrast sensitivities to determine foveal and peripheral ability to discriminate between an original and a distorted version of a polar-circular sinusoidal grating and a face image. Contrast sensitivities as a function of image size were spatially scaleable across eccentricities for both the face and grating. Furthermore, irrespective of stimulus, performance could be scaled with the same individual E2 value. Thus task simplicity overrides the nature of the stimulus in determining scaling requirements, suggesting that it is the complexity of the task, not of the stimulus, that makes contrast scaling necessary in complex tasks.     

Holistic processing improves change detection but impairs change identification

It has been just over a century since Gestalt psychologists described the factors that contribute to the holistic processing of visually presented stimuli. Recent research indicates that holistic processing may come at a cost; specifically, the perception of holistic forms may reduce the visibility of constituent parts. In the present experiment, we examined change detection and change identification accuracy with Kanizsa rectangle patterns that were arranged to either form a Gestalt whole or not. Results from an experiment with 62 participants support this trade-off in processing holistic forms. Holistic processing improved the detection of change but obstructed its identification. Results are discussed in terms of both their theoretical significance and their application in areas ranging from baggage screening and the detection of changes in radiological images to the systems that are used to generate composite images of perpetrators on the basis of eyewitness reports.     

Oral administration of guanosine impairs inhibitory avoidance performance in rats and mice

Extracellular guanine-based purines, mainly the nucleoside guanosine, have recently been shown to exert neuroprotective effects, which seem to be related to antagonism of the glutamatergic system. In this study, we investigated the effects of acute oral administration of guanosine on inhibitory avoidance task in rats and mice. We also studied its effects on locomotor activity, anxiety-related behaviors and mechanisms of action involving the purinergic system. Guanosine (2.0 and 7.5mg/kg, per os), administered 75min pretraining, dose-dependently impaired retention of the inhibitory avoidance task in rats and mice, an effect not prevented by the adenosine receptor antagonist caffeine. Guanosine presented no effects on locomotor activity and anxiety-related behaviors. This amnesic effect of guanosine may be compatible with inhibition of glutamatergic system and seems to be not mediated by adenosine.     

The perception of concurrent sound objects in harmonic complexes impairs gap detection

Since the introduction of the concept of auditory scene analysis, there has been a paucity of work focusing on the theoretical explanation of how attention is allocated within a complex auditory scene. Here we examined signal detection in situations that promote either the fusion of tonal elements into a single sound object or the segregation of a mistuned element (i.e., harmonic) that "popped out" as a separate individuated auditory object and yielded the perception of concurrent sound objects. On each trial, participants indicated whether the incoming complex sound contained a brief gap or not. The gap (i.e., signal) was always inserted in the middle of one of the tonal elements. Our findings were consistent with an object-based account in which perception of two simultaneous auditory objects interfered with signal detection. This effect was observed for a wide range of gap durations and was greater when the mistuned harmonic was perceived as a separate object. These results suggest that attention may be initially shared among concurrent sound objects thereby reducing listeners' ability to process acoustic details belonging to a particular sound object. These findings provide new theoretical insight for our understanding of auditory attention and auditory scene analysis.     

Chronic perchlorate exposure impairs stickleback reproductive behaviour and swimming performance

We describe behavioural changes in two generations of threespine stickleback (Gasterosteus aculeatus) exposed to environmentally relevant concentrations of perchlorate. The first generation (G(0,2002)) was exposed as two-year-old adults to perchlorate in experimental groups ranging in concentration from less than the method detection limit (<1.1 ppb) to 18.6 ppm for up to 22 days during their courtship, spawning, egg guarding, and first five days of fry guarding. No differences were noted in the behaviour or reproductive output of these fish that were exposed as adults. However, perchlorate exposure throughout development caused widespread effects in the second generation (G(1,2003)), which was spawned and raised through sexual maturity in one of four nominal experimental groups (0, 30 and 100 ppm, and a 'variable' treatment that progressively increased from <1.1 ppb to approximately 60 ppm perchlorate). Dose-dependent effects were found during the G(1,2003)'s swimming and behavioural evaluations, including higher mortality rates among treated fish following stressful events. Perchlorate-exposed fish had higher failure rates during swimming trials and failed at lower flow rates than control fish. A number of treated fish exhibited seizures. Progressively fewer males completed benchmark metrics, such as nest building, spawning, nursery formation, or fry production, in a dose-dependent manner. Fewer males from higher treatments courted females, and those that did initiated courtship later and had a reduced behavioural repertoire compared to fish from lower treatments. The lowest observed adverse effect level (LOAEL) for swimming performance, reproductive behaviour, survivorship and recruitment was 30 ppm perchlorate (our lowest G(1,2003) treatment), and near complete inhibition of reproductive activity was noted among males raised in 100 ppm perchlorate. A small number of treated G(1,2003) females were isolated in aquaria, and some performed reproductive behaviour typical of males, such as biting, leading and zig-zagging in the presence of gravid females. These findings have profound implications for recruitment in wild fish populations exposed to perchlorate, and suggest that perchlorate may disrupt behaviour in other vertebrates as well.     

Motivation and performance: Uncertainty regulation in Canada and Japan

In a field study involving university students from Canada and Japan, we tested hypotheses from the theory of uncertainty orientation (Sorrentino and Roney in The uncertain mind: Individual differences in facing the unknown. Psychology Press, Philadelphia 2000). Consistent with previous research, those possessing an uncertainty orientation that matched their culture’s predominant style of uncertainty regulation perceived a better student-classroom fit than those who did not match their culture’s predominant style of uncertainty regulation. More importantly, we predicted and found that actual course grades varied as a function of the culture’s style of uncertainty regulation in interaction with the participant’s uncertainty orientation and achievement-related motives. Implications of these findings and applied relevance are discussed.     

The minimum temporal thresholds for motion detection of grating patterns

The minimum temporal thresholds for absolute motion detection were measured for sinusoidal grating patterns in foveal vision. Test patterns of relatively low temporal frequencies and low velocities were examined. The thresholds clearly decreased with test velocities rather than with test temporal frequencies. Modified velocity-time reciprocity was observed (i.e. the relationship between test velocity and temporal thresholds was described by a simple equation including two constants which indicate temporal and spatial limits). The temporal constant was about 35 ms and the spatial constant was about 1 min of arc. These constants are thought to provide the basic constraints on motion detection.     

Lightening the load: perceptual load impairs visual detection in typical adults but not in autism

Autism spectrum disorder (ASD) research portrays a mixed picture of attentional abilities with demonstrations of enhancements (e.g., superior visual search) and deficits (e.g., higher distractibility). Here we test a potential resolution derived from the Load Theory of Attention (e.g., Lavie, 2005). In Load Theory, distractor processing depends on the perceptual load of the task and as such can only be eliminated under high load that engages full capacity. We hypothesize that ASD involves enhanced perceptual capacity, leading to the superior performance and increased distractor processing previously reported. Using a signal-detection paradigm, we test this directly and demonstrate that, under higher levels of load, perceptual sensitivity was reduced in typical adults but not in adults with ASD. These findings confirm our hypothesis and offer a promising solution to the previous discrepancies by suggesting that increased distractor processing in ASD results not from a filtering deficit but from enhanced perceptual capacity.     

Four hours of paradoxical sleep deprivation impairs alternation performance in a water maze in the rat

Sixteen rats were deprived of paradoxical sleep (PS) for 4 h using the "flower pot" technique and 16 other served as yoked controls. PS-deprived and control rats then had to learn a water maze using either a standard allocentric configuration (i.e., finding the submerged platform using external cues; n = 6/group) or an alternation version (goal platform alternating between two locations; n 10/group). Rats were submitted to six trials with a cutoff time of 60 s and an intertrial interval of 5 min. Criterion was set as two consecutive successful completions. PS-deprived rats made more quadrant entries and took more time to reach criterion on the alternation task than control rats while both groups were equal on the allocentric task. Based on lesion studies (Ethier et al., this issue) we propose that tasks that require an intact medial prefrontal cortex are particularly sensitive to PS deprivation.     

Working-memory and auditory localization: Demand for central resources impairs performance

Four experiments explored possible roles for working memory in sound localization. In each experiment, the angular error of localization was assessed when performed alone, or concurrently with a working-memory task. The role of the phonological slave systems in auditory localization was ruled out by Experiments 1 and 2, while an engagement of central resources was suggested by the results of Experiment 3. Experiment 4 examined the involvement of visuo-spatial systems in auditory localization and revealed impairment of localization by the concurrent spatial working-memory task. A comparison of dual-task decrement across all four studies suggests that localization places greater demand on central than on spatial resources.     

Reversible inactivation of the nucleus of the solitary tract impairs retention performance in an inhibitory avoidance task.

Several peripherally acting hormones and drugs are known to modulate memory storage processes, yet the mechanisms which permit these agents to influence memory is not well understood since they do not freely enter the brain. The nucleus of the solitary tract (NTS) is one brainstem structure which receives important neural input from the periphery. Therefore, the objective of this experiment was to determine whether the NTS is involved in modulating processes contributing to memory formation. Male Sprague-Dawley rats were trained in a one-trial inhibitory avoidance task (0.35 mA, 0.5 s footshock). Immediately or 2 h after training microinjections of 2% lidocaine hydrochloride (20 mg/kg) or a phosphate buffer solution were administered bilaterally into the NTS. Two other groups received microinjections of lidocaine into the fourth ventricle or cerebellum. On retention tests given 48 h after training the latency to reenter the dark compartment of the apparatus was recorded. The retention latencies of rats receiving bilateral microinjections of 0.5 microliter of lidocaine hydrochloride into the NTS were significantly shorter than those of animals given injections of a buffer solution (0.5 microliter), delayed injections of buffer or lidocaine, or control injections of lidocaine into the cerebellum or fourth ventricle. These findings suggest that memory storage processes are impaired by reversible inactivation of the NTS after training. The implications of these findings in terms of a possible role of the NTS in modulating brain processes involved in memory storage are discussed.     

Walking impairs cognitive performance among people with multiple sclerosis but not controls

People with multiple sclerosis (MS) complain of problems completing two tasks simultaneously; sometimes called ‘dual-tasking’ (DT). Previous research in DT among people with MS has focused on how adding a cognitive task interferes with gait and few have measured how adding a motor task could interfere with cognition. We aimed to determine the extent to which walking affects a concurrent working memory task in people with MS compared to healthy controls. We recruited MS participants (n = 13) and controls (n = 10) matched by age (±3 years), education (±3 years) and gender. Participants first completed the cognitive task (subtracting 7’s from the previous number) and then again while walking on an instrumented walkway. Although there were no baseline differences in cognition or walking between MS participants and controls, MS participants demonstrated a 52% decrease in number of correct answers during DT (p < 0.001). Mental Tracking Rate (% correct answers/min) correlated strongly with MS-related disability measured using the Expanded Disability Status Scale (EDSS; r(11) = −0.68, p < 0.01). We propose that compromised mental tracking during walking could be related to limited neural resource capacity and could be a potentially useful outcome measure to detect ecologically valid dual tasking impairments.     

Transient overexpression of the 5-HT1A receptor impairs water-maze but not hole-board performance

Previously, we showed that mice that overexpress the 5-HT(1A) receptor transiently from embryonic to perinatal stages show reduced anxiety and changes in brain serotonin turnover as adults. Here, we investigated the long-term effects of the temporary overexpression of the 5-HT(1A) receptor during early embryonic and perinatal development on the performance in two memory tasks. In the hole-board test mice that were homozygous for the transgene showed similar behavioral habituation but increased locomotion compared to heterozygous mice. In contrast water-maze performance of homozygous mice was impaired compared to heterozygous mice. These results suggest that a transient overexpression of 5-HT(1A) receptor during embryonic and perinatal development has detrimental effects on water-maze performance at adult stages.     

Performance of blind and sighted humans on a tactile grating detection task

We compared the abilities of blind and sighted humans to distinguish grooved from smooth surfaces pressed against the stationary index fingertip. Ranging in age from 20 to 72 years, 37 blind and 47 sighted subjects participated in an automated two-alternative forced-choice tactile grating detection task. The tactile acuity of blind and sighted subjects declined with age at equivalent rates (0.011-mm threshold increase per year), but the blind subjects were able to perceive significantly thinner grooves than were their sighted peers (the average difference between blind and sighted subjects of the same age and gender was 0.267 mm). The blind Braille readers performed no better than the blind nonreaders, and the congenitally blind subjects performed equivalently to those with adult-onset blindness. The superior tactile acuity of blind persons may result from the involvement of normally visually responsive cerebrocortical areas in tactile processing, as shown by functional-imaging studies.     

Alcohol impairs visual presence/absence detection more for females than for males

Ninety subjects (45 males, 45 females) were given 0.0, 0.5, or 1.0 ml/kg body weight of 190-proof ethanol and tested for chance-level presence/absence detection thresholds with energy-masked presentations of traffic signs and blank inputs. Alcohol produced higher blood alcohol concentration (BAC) levels, and higher detection threshold durations, for females than for males. These results indicate that alcohol influences precortical visual processing and that the influence is greater for females than for males. The higher bioavailability of alcohol in women is likely due to less gastric oxidation of ethanol in women than in men.