The stress experience dependent long-term depression disassociated with stress effect on spatial memory task

Behavioral stress can either block or facilitate memory and affect the induction of long-term potentiation (LTP) and long-term depression (LTD). However, the relevance of the stress experience-dependent long-term depression (SLTD) to spatial memory task is unknown. Here we have investigated the effects of acute and sub-acute elevated platform (EP) and foot shock (FS) stress on LTD induction in CA1 region of the hippocampus of anesthetized rats and spatial memory in Morris water maze. We found that LTD was facilitated by acute EP stress, but not by sub-acute EP stress that may be due to the fast adaptation of the animals to this naturalistic mild stress. However, FS stress, an inadaptable strong stress, facilitated LTD induction both in acute and sub-acute treatment. In addition, with the same stress protocols, acute EP stress impaired spatial memory but the sub-acute EP stressed animals performed the spatial memory task as well as the controls, may due to the same reason of adaptation. However, acute FS stress slightly impaired learning but sub-acute FS even enhanced memory retrieval. Our results showed that SLTD was disassociated with the effect of stress on memory task but might be related to stress experience-dependent form of aberrant memory. (C) 2003 Elsevier Science Ireland Ltd. and the Japan Neuroscience Society. All rights reserved.

汉语婴儿对早期词汇的理解与表达

Whether Mandarin is a verb-friendly language for young word learners or not is a hotly debated issue. Researches on children's word learning were either naturalistic study or experimental study, and they were from cross-cultural perspective. This study tries to examine the noun/verb proportion in Mandarin infants, from a longitudinal perspective; it also examines how Mandarin infants understand their first nouns and verbs using both naturalistic study and experimental study. The results of this research are: 1） According to the results of CDI test, Mandarin infants of 18 month old could say more verbs than nouns significantly; while 24 month-olds could say more nouns than verbs significantly. 2） According to the results of CDI test, Mandarin infants’ verb/noun proportion was higher in 18 month old than in 24 month old. This means that the relative advantage of verb learning may be easier to show up in infants younger than 2 years old. 3） The total vocabulary of 18 month-olds was positively correlated with the Mean Length of Utterances(MLU) of 24 month-olds. The MLU of 24 month olds was positively correlated with the verbs of 18 month-olds. 4） Only 24 month-old could succeed in our IPLP study and showed “true” understanding to their familiar words. 14- and 18- month-olds watch the target side and non-target side randomly. 5） According to the results of IPLP study, the infants could understand nouns better than verbs. Both female and male infants understood nouns better than verbs, but females seemed to have stronger tendency to watch the object-same side in both noun and verb condition. 6） According to the results of parents’ reports, all the infants in 3 age groups could understand verbs as well as nouns, and they are quite familiar with those words. However, IPLP study results showed that these infants understood nouns better than verbs. 7） In IPLP study, less than 50% of the Mandarin infants watch the target side of verbs longer than the non-target side (action-same response). However, the AS responses appear more frequently in verb condition than in noun condition among 24-month-olds.