Uncertainty about old information results in differential predator memory in tadpoles

As information ages, it may become less accurate, resulting in increased uncertainty for decision makers. For example, chemical alarm cues (AC) are a source of public information about a nearby predator attack, and these cues can become spatially inaccurate through time. These cues can also degrade quickly under natural conditions, and cue receivers are sensitive to such degradation. Although numerous studies have documented predator-recognition learning from fresh AC, no studies have explored learning from aged AC and whether the uncertainty associated with this older information contributes to shortening the retention of learned responses (i.e. the 'memory window'). Here, we found that wood frog tadpoles, Lithobates sylvaticus, learned to recognize a novel odour as a predator when paired with AC aged under natural conditions for up to 1 h. However, only tadpoles conditioned with fresh AC were found to retain this learned response when tested 9 days after conditioning. These results support the hypothesis that the memory window is shortened by the uncertainty associated with older information, preventing the long-term costs of a learned association that was based on potentially outdated information.

Early-life and parental predation risk shape fear acquisition in adult minnows

Exposure to predation risk can induce a fearful baseline state, as well as fear reactions toward novel situations (i.e., neophobia). Some research indicates that risk exposure during sensitive periods makes adults more prone to acquiring long-term fearful phenotypes. However, chronic risk can also lead to ignoring threats in order to maintain other activities. We sought to assess how a relatively long period of low risk, experienced either early in life or by the previous generation, influences fear behaviour acquired from a short period of high risk as adults. We used fathead minnows as study subjects and simulated predation risk with repeated exposures to conspecific chemical alarm cues. The period of high risk experienced by adults induced typical fear behaviour (baseline freezing and neophobia), whereas the early-life low-risk period 1 year prior caused only a reduction in baseline foraging. We found no evidence that the early-life risk significantly altered the fear acquired from the adult-risk period. However, in a second experiment, a low-risk period during the parental generation interacted with a high-risk period experienced by the adult offspring. The combination of both risk periods heightened baseline freezing despite parental risk having little effect independently. Hence, our study provides evidence that parental risk exposure can lead to an additive intergenerational effect on fear acquisition in minnows.

A profile of low vision among the blind school students in Lumbini Zone of Nepal

INTRODUCTION

There is an increasing awareness about the needs of students with low vision, particularly in developing countries where programs of integrated education are being developed. However, the appropriate low vision services are usually neither available, nor affordable.

OBJECTIVES

To study the profile of students with low vision in Lumbini Zone of Nepal.

MATERIALS AND METHODS

A cross-sectional study included students with low vision from 8 integrated schools. The reading performance was measured using their own text-books with optical low vision devices prescribed for near reading. The reading rates were measured on a range of print sizes. The Standard Clinical Low Vision Assessment Form and the National Low Vision Program protocol were used. SPSS software was used in data analysis.

RESULTS

Of 46 students enrolled, 23 had a mild visual impairment, 18 had severe visual impairment and 5 were blind. Spectacles were needed for 29 (63 %) students. Of the 11 students who had been wearing glasses, the visual acuity improved in 4 with a change in prescription. 91 % of the students had near vision better or equal to 1.5 M with optical low vision services for near reading. The reading rate was 24 WPM at the age of 5 years, whereas at the age of 21 years, it was 55 WPM.

CONCLUSION

The majority of the students with low vision need optical low vision services. Accurate refraction is important in these students. The reading rate increases significantly with improved near visual acuity.