摘要:

AbstractThe general theory of critical periods applies to organizational processes involved in the development of any living system on any level of organization and states that the time during which an organizational process is proceeding most rapidly is the time when the process may most easily be altered or modified. Complex organizational processes involving 2 or more interdependent subprocesses may show 1 to several critical periods, depending on the time relationships of the subprocesses. The nature of the relationships between interdependent processes operating on different levels is again dependent on time and is a more meaningful formulation than that of the old “innate‐acquired” dichotomy. These theoretical considerations lead to the conclusion that understanding a critical‐period phenomenon rests on analyzing the nature of the organizational process or processes involved. An example is given in a review of research on the critical period for primary socialization (social attachment) in the dog. Evidence that attachment has taken place consists of discriminative behavior in relation to familiar and unfamiliar objects and rests on a minimum of 3 processes: (1) organization of the separation distress response; (2) visual and auditory sensory capacities; and (3) long‐term associative memory capacities. Once these capacities are developed, the overall attachment process proceeds very rapidly (the critical period for such attachment). Thus the critical periods for the organizational subprocesses precede or slightly overlap that for the overall process. Deeper analyses of these processes must rest on neurophysiological research. The theory of critical periods is a general one that should apply to any developmental organizational process which proceeds at grossly different rates at differ

ISSN:0012-1630    

DOI:10.1002/dev.420070602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractRats exposed to environmental complexity (EC) for 4 days had heavier cerebra than controls maintained in an impoverished condition (IC). Such a difference did not occur when the EC‐IC pairs were given a subcutaneous injection of distilled water or an intracranial injection of saline on the 3rd day of treatment. Injecting animals in psycho‐biochemical experiments is therefore a procedure whose effects should be determined in every c

ISSN:0012-1630    

DOI:10.1002/dev.420070603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractHeart rate (HR) responses to 2 intensities (.2 and 2.0 mA) of electric shock were studied in preweaning rats at 5, 7, 9, 11, 13, 15, 17, 19, and 21 days. Both weak and strong shock elicited at least some HR acceleration at all ages. Beginning on Day 13, a deceleratory component was added to the response to weak shock. HR acceleration was significantly greater in response to strong shock on Days 5 and 7 and then again from Days 15‐21. Strong shock also elicited a relatively long‐latency bradycardia beginning with Day 11. Results are discussed in terms of the emergence of 3 response tendencies: (1) the orienting reflex; (2) the defensive reflex; and (3) a change in the state of the organism, and their possible implications for the study of preweaning shock on subsequent behav

ISSN:0012-1630    

DOI:10.1002/dev.420070604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractA classification of apparently normal neonatal EEG's into 4 classes (A‐D) on the basis of progressive maturity was devised and applied to 273 EEG's of 117 apparently normal newborns recorded between 24 and 50 weeks conceptional age (CA). Both the order in which the 4 classes of EEG's occurred for subjects upon whom more than 1 EEG was obtained, and the distributions of the ages over which the 4 classes were observed confirmed that the classes do indeed represent a maturational sequence of EEG pattern changes. Of the 81 original premature subjects, 46 underwent comprehensive clinical evaluation between 3 yr 9 months and 8 yr 7 months of age. Various features of their neonatal EEG's were evaluated in the light of clinical outcome. The results do not demonstrate the usefulness of the routine EEG as a prognostic indicator in neonates not displaying specific pathology at birth. They do offer some evidence of a relationship between immaturity of the EEG relative to CA in the neonatal period and the later manifestation of congenital disorders involving the brain, but the tendency, even if confirmed, may not prove strong enough to warrant prognostic decisions in individual

ISSN:0012-1630    

DOI:10.1002/dev.420070605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractAccumulation of protein and adenosine 2',3'‐cyclic phosphohydrolase activity have been found to increase with age in myelin isolated from human subjects. Notable alterations in the quantitative distribution of myelin proteins separated by disc polyacrylamide gel electrophoresis were seen in development. Proteolipid protein was found in myelin before the appearance of basic encephalitogenic protein. A myelin‐like fraction was also isolated from developing human brain. These chemical observations were correlated with ultrastructural changes in the isolated myelin during developm

ISSN:0012-1630    

DOI:10.1002/dev.420070606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractRepeated time‐lapse photographic observations were used to examine the maternal behavior and pup development of female Holtzman rats maintained on either a low‐protein (12% casein by weight) or a high‐protein (25% casein) diet throughout the period of lactation. Dams fed the low‐protein diet were observed to spend more time in the nesting area with their pups than dams fed the high‐protein diet. Locomotor activity of the dams did not differ between the 2 groups. The behavioral development of the pups suckling the dams receiving the low‐protein diet was markedly depressed as compared with the controls. Included in this latter observation were pup behaviors such as movement from the nesting area, feeding and drinking from available supplies, and rearing and climbing activity. The results indicate that feeding a low‐protein diet to a lactating dam results in behavioral changes in both the dam and pups that tend to minimize the exposure of the pups to the immediat

ISSN:0012-1630    

DOI:10.1002/dev.420070607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of early conditions of rearing on parental attention and on the heat exchanges of infant mice were examined: (1) Inbred migce 6 days old were exposed at 7.5 °C and returned to the nest. Mice which were rewarmed before return recieved more parental attention then cold mice or handled Controls. (2) Outbred mice 6 days old with injured ears were licked more by there mothers then uninjured litter mates. (3) Liking of genitalia alos occured but was unrelated to ear injury. (4) surface temperature of 6‐day old inbred mice declined at after artifical “licking” with a wet brush. (5) Surfarce temperature of inbred mice exposed at 22–28 °C for 2.5 min. declined at age 0–11 days and increased at age 15–20 days. Exposure at 15°C led to a declined in surface temperature at all ages. (6) Wild or laboratory mice 4 or 6 satge old were observe in their nests. Surface temperature decreased after parental licking or loss of contact with the litter and increased on contact with mother. Temperatures also increased rapidly if the mouse was held on the experimentor's hand.in work on the effects of early conditions of rearing, attention should be paid to the minute details of parental attention and the heat exchanges of the

ISSN:0012-1630    

DOI:10.1002/dev.1974.4200070608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

ISSN:0012-1630    

DOI:10.1002/dev.420070601

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY