Young infants’ sensitivity to shading stimuli with radial motion1

Abstract: The purpose of this study was to examine 5‐month‐old infant's sensitivity to a shading cue with radial motion. Our stimuli were radially expanding or contracting circles with vertical or horizontal shadings. We tested infants’ preference for vertical (top‐ and bottom‐lit) and horizontal (left‐ and right‐lit) shadings. The results indicate that infants tested with the vertical shading showed significant preference for the top‐lit shading, whereas infants tested with the horizontal shading did not show any significant preference. The fact that the significant preference was observed only in the vertical shading condition suggests that 5‐month‐old infants might use shading information on the basis of the “light‐from‐above assumption.” We revealed that even 5‐month‐old infants are sensitive to shading information when they are exposed to shading stimuli with radial motion.     

Effect of Object and Task Properties on Bimanual Transport

The use of both hands simultaneously when manipulating objects is fairly commonplace, but it is not known what factors encourage people to use two hands as opposed to one during simple tasks such as transport. In particular, we are interested in three possible transport strategies: unimanual transport, handing off between hands, and symmetric bimanual transport. In this study, we investigate the effect of object size, weight, and starting and ending position (configuration) as well as the need to balance the object on the use of these three strategies in a bowl-moving task. We find that configuration and balance have a strong effect on choice of strategy, and size and weight have a weaker effect. Hand-offs are most often used when the task requires moving an object from left to right and vice versa, while the unimanual strategy was frequently used when passing front to back. The bimanual strategy is only weakly affected by configuration. The need to balance an object causes subjects to favor unimanual and bimanual strategies over the hand-off. In addition, an analysis of transport duration and body rotation suggests that strategy choice may be driven by the desire to minimize body rotation.     

Apodemus sylvaticus (LOXT) is a suitable mouse strain for testing spatial memory retention in the Morris water maze

Information on the difference in cognitive function between laboratory and wild-caught mice is anecdotal and this question has not been systematically studied. Moreover, studying a wild-caught mouse strain per se may add information to the repertoire of mouse strains available. We aimed to study spatial memory in a wild mouse strain (Apodemus sylvaticus, AS) as compared to two individual laboratory mouse strains.Male AS (n = 20), CD1 (n = 19) and C57BL/6J mice (n = 19), 12–14 weeks old, were used in the experiments. The Morris water maze (MWM) was used for determination of spatial memory and time spent in the target quadrant at time points 5 (D5) and 12 days (D12) was evaluated. During the acquisition phase latency to reach the platform and path length to reach the platform was evaluated.Following four training days on day 5 (D5), time spent in the target quadrant was highest in AS > CD1 > C57BL/6J (P < 0.006). On day 12 (D12), time spent in the target quadrant was significantly higher in AS than in both other strains (P < 0.001).All animals learned the task and during the acquisition phase, latency to reach the platform as well as path length decreased significantly in AS.It is concluded that the AS is the most suitable strain for the evaluation of spatial memory in the MWM and is presenting with memory retention superior to laboratory mouse strains CD1 and C57BL/6J.     

Anterior but not intralaminar thalamic nuclei support allocentric spatial memory

Medial thalamic damage is a common cause of severe memory disruption in humans. Both the anterior thalamic nuclei (ATN) and the intralaminar thalamic nuclei (ILN) have been suggested as primary sites of diencephalic injury underlying learning and memory deficits, but their respective roles have yet to be resolved. The present study explicitly compared two spatial memory tasks in male PVGc hooded rats with selective neurotoxic lesions to either (1) the ATN or (2) the rostral ILN (and adjacent lateral mediodorsal thalamic nuclei; ILN/LT lesions). As predicted, the ATN group, but not the ILN/LT group, exhibited clear deficits in the Morris water maze task for the initial acquisition of a fixed hidden platform and its reversal to a new position. The second task examined acquisition of egocentric spatial reference memory for a left or right body turn, using any three arms in an 8-arm water maze on any given trial; contrary to predictions, both lesion groups performed as well as the Sham group. The lack of deficits in ILN/LT rats on this second task contrasted with previous findings reporting a detrimental effect of ILN/LT lesions on egocentric working memory. The clear dissociation between the influence of ATN and ILN/LT lesions with respect to allocentric spatial reference memory in the Morris maze emphasizes that caution is required when interpreting the effects of non-ATN thalamic lesions on spatial memory when the lesions encroach substantial areas of the adjacent ATN region.     

Higher levels of estradiol replacement correlate with better spatial memory in surgically menopausal young and middle-aged rats

The current study investigated whether, for spatial reference memory, age impacts (1) sensitivity to surgical ovarian hormone loss (Ovx), (2) response to estradiol therapy (ET), and (3) the relation between circulating estradiol levels and memory scores in ovary-intact sham and Ovx plus ET rats. Young, middle-aged and aged Fischer-344 rats received sham, Ovx or Ovx plus ET treatments, and were then tested on the Morris maze. After the last test trial, a probe trial was given whereby the platform was removed. Circulating estradiol levels were then determined and correlated with performance. In Study 1, Ovx facilitated learning on day one, but impaired performance after day one, in young rats. Ovx did not influence performance in middle-aged rats. In young and middle-aged Ovx rats, ET enhanced performance with higher exogenous estradiol levels correlating with better performance during testing and the probe trial. There was no relationship between endogenous estradiol levels and performance in sham young or middle-aged rats. Study 2 showed that, like middle-aged rats, aged rats were not impacted by Ovx. Further, for aged Ovx rats, the ET regimen that was beneficial at earlier ages was no longer effective during test trials, and had only minor benefits for platform localization as assessed by the probe trial. Collectively, the findings suggest that the effects of Ovx as well as responsivity to the currently utilized ET regimen changes with age. Further, there appears to be a distinction between sensitivity to Ovx and responsiveness to ET after Ovx for spatial reference memory performance.     

Fatty acid amide hydrolase (FAAH) knockout mice exhibit enhanced acquisition of an aversive, but not of an appetitive, Barnes maze task

It is well established that genetic deletion or pharmacological inhibition of the CB₁ receptor disrupts extinction learning in aversive conditioning tasks, but not in appetitive tasks. Consistent with these findings is that genetic deletion or pharmacological inhibition of fatty acid amide hydrolase (FAAH), the primary catabolic enzyme of the endogenous cannabinoid anandamide (AEA), accelerates acquisition as well as extinction in aversive conditioning tasks. However, it is unknown whether FAAH blockade will affect acquisition in an appetitive conditioning task. Therefore, in the present study, we assessed FAAH (−/−) and (+/+) mice in appetitive and aversive Barnes maze conditioning procedures. Here we report that FAAH (−/−) mice displayed accelerated acquisition rates in an aversively-motivated, but not in the appetitively-motivated, Barnes maze task. The CB₁ receptor antagonist, rimonabant attenuated enhanced acquisition in the aversive procedure, consistent with the idea that elevated AEA levels mediate this apparent nootropic effect. These findings support the hypothesis that stimulation of the endocannabinoid system enhances learned behavior in aversive, but not appetitive, conditioning paradigms.     

An eight-alternative concurrent schedule: foraging in a radial maze.

In two experiments conducted in an eight-arm radial maze, food pellets were delivered when a photocell beam was broken at the end of each arm via a nose poke, according to either fixed-interval or random-interval schedules of reinforcement, with each arm providing a different frequency of reinforcement. The behavior of rats exposed to these procedures was well described by the generalized matching law; that is, the relationships between log behavior ratios and log pellet ratios were approximated by linear functions. The slopes of these log-log functions, an index of sensitivity to reinforcement frequency, were greatest for nose pokes, intermediate for time spent in an arm, and least for arm entries. Similar results were obtained with both fixed-interval and random-interval schedules. Addition of a 10-s changeover delay in both experiments eliminated the slope differentials between nose pokes and time spent in an arm by reducing the slopes of the nose-poke functions. These results suggest that different aspects of foraging may be differentially sensitive to reinforcement frequency. With concurrent fixed-interval schedules, the degree of temporal control exerted by individual fixed-interval schedules was directly related to reinforcement frequency.     

海马结构、前额皮层或尾-壳核损毁对大鼠空间认知能力的影响

本研究的目的是探讨海马结构(HF)、前额皮层(PFC)和尾-壳核(CP)在大鼠空间认知加工中的作用。实验观察到HP或PFC损毁大鼠Morris迷宫学习或记忆作业成绩显著低于CP损毁组和控制组(CG);HF损毁大鼠主要采用与其它各组不同的“非图类”搜索策略。搜索策略的差异提示:HF和PFC在大鼠图认知加工系统中处于不同的功能层次,HF起相对重要的作用。CP几乎不影响大鼠空间认知能力,表现出哺乳类与鸟类同源结构的功能分化倾向。     

Honeybee Memory: Navigation by Associative Grouping and Recall of Visual Stimuli

Studies of navigation in bees and ants are beginning to reveal that foraging insects traveling repeatedly to a food source navigate by using a series of visual images of the environment acquired en route (Collett, 1996; Collett et al., 1993; Judd & Collett, 1998; Wehner et al., 1990, 1996). By comparing the currently viewed scene with the appropriate stored image, the insect is able to ascertain whether or not it is on the correct path and make any necessary corrections. If a bee happens to forage at more than one site, then she needs not only to memorize a separate set of images for each route that she has learned but also to retrieve the set of images that is appropriate to each route. Here we examine the bee's capacity to learn and later retrieve from memory two different sets of visual stimuli. Bees were trained to fly through a compound Y-maze where they were presented alternately with two different sequences of visual stimuli on their route to a food reward. We find that bees can indeed store two different sequences of images simultaneously. Furthermore, the trained bees are able to classify the memorized images into two groups, one pertaining to each three-stimulus set. Exposure to any of the images pertaining to one set triggers recall of all of the other images associated with that set. Associative grouping and recall of visual stimuli, demonstrated here for the first time in honeybees, provide an effective means of retrieving the appropriate navigational information from memory.