Minimizing the number of observations: A generalization of the spearman-brown formula

A new method for determining the minimum number of observations per subject needed to achieve a specific generalizability coefficient is presented. This method, which consists of a branch-and-bound algorithm, allows for the employment of constraints specified by the investigator.     

A note on natural numbers objects in monoidal categories

The internal language of a monoidal category yields simple proofs of results about a natural numbers object therein.     

School adjustment, school performance and peer relations among first-graders in a Swedish suburban area

A study of 95 first-graders in one school management area used teacher ratings of problems and sociometric ratings to assess school adjustment and peer relations; 14% of the children had difficulties in reading/writing, motor skill, concentration and psychosocial function. Behavioural problems did not generally coincide with poor scholastic performance, but a small group (6.3%) exhibited problems in both reading/writing, concentration, gross and fine motor skill and psychosocial functions. Sociometric results showed only moderate agreement with teacher ratings. Extremely popular boys had no teacher-rated problems, but children with teacher-rated problems did not to any high degree tend to be isolated. Poor gross motor skill did distinguish isolated boys from others, a relationship that was not evident among the girls. The need to study the validity of teacher ratings as well as the prognostic value of school adjustment in first grade was stressed.     

Microinjections of leupeptin in the frontal cortex or dorsal hippocampus block spatial learning in the rat

Adult male Long-Evans hooded rats were given bilateral microinjections of 18 mM leupeptin or saline through cannulae implanted with tips aimed at the frontal cortex or CA1 or CA3 hippocampal cell fields. Five minutes following injections animals were allowed to complete an eight-arm radial maze. The acquisition criterion required that the animal make 7 correct choices of the first 8, and 8 correct choices of the first 10, for five consecutive sessions. Leupeptin slowed acquisition of the eight-arm radial maze task when injected into the CA1 and CA3 hippocampal fields or the frontal cortex, but did not influence spontaneous activity. These results suggest that earlier reports of the amnestic effect of leupeptin when administered into the lateral cerebral ventricle may have been due to effects within the cortex and hippocampus. The present experiment represents the first attempt to identify behaviorally those brain areas in which leupeptin acts to alter learning.     

ACTH 4-9 analog can retard spatial alternation learning in brain damaged and normal rats

Thirty adult male hooded rats (Long-Evans strain) were assigned randomly to one of three lesion groups (n = 10) and prepared with medial frontal, posterior parietal, or sham neocortical injuries. Following a recovery interval of 10-12 days, access to water was limited to 30 min per day and the rats were shaped to traverse a T-maze for a reward of sweetened water. After a pretraining criterion was attained, osmotic minipumps (Alzet 2002) were installed subcutaneously. The minipumps delivered chronically for the next 14 to 15 days either 0 or 1.2 micrograms of ACTH 4-9 dissolved in bacteriostatic saline per day while the rats were trained on a reinforced spatial alternation task. Analysis of the number of errors made to a criterion of at least 80% correct alternations in two consecutive training sessions, or a ceiling of 62 errors (attained by two rats with parietal lesions), revealed that learning was impaired in the rats with parietal injuries. Contrary to our hypothesis, animals receiving ACTH 4-9 committed more errors than their counterparts receiving only saline.     

Context effects in stroop-like word and picture processing

Presents a series of 6 experiments in which Stroop-like effects were generated by modally pure color-color, picture-picture, and word-word stimuli instead of the usual modally mixed color-word or picture-word stimuli. Naming, reading, and categorization tasks were applied. The Stroop inhibition was preserved with these stimuli but unexpectedly showed a semantic gradient only in the naming and not in the reading task. Word categorizing was slower and more interference prone than picture categorizing. These and other results can be captured by a model with two main assumptions: (a) semantic memory and the lexicon are separate, and (b) words have privileged access to the lexicon, whereas pictures and colors have privileged access to the semantic network. Such a model is developed and put to an initial test.     

Video-task assessment of learning and memory in macaques (Macaca mulatta): effects of stimulus movement on performance

Effects of stimulus movement on learning, transfer, matching, and short-term memory performance were assessed with 2 monkeys using a video-task paradigm in which the animals responded to computer-generated images by manipulating a joystick. Performance on tests of learning set, transfer index, matching to sample, and delayed matching to sample in the video-task paradigm was comparable to that obtained in previous investigations using the Wisconsin General Testing Apparatus. Additionally, learning, transfer, and matching were reliably and significantly better when the stimuli or discriminanda moved than when the stimuli were stationary. External manipulations such as stimulus movement may increase attention to the demands of a task, which in turn should increase the efficiency of learning. These findings have implications for the investigation of learning in other populations, as well as for the application of the video-task paradigm to comparative study.     

The Y chromosome, social signals, and offense in mice

Offense is one type of aggression in mice (Mus musculus/Mus domesticus). Offense was measured in a panel of testers design for two congenic strains of mice. The two congenic strains were DBA1Bg and DBA1. C57BL10-YBg. These differ in the Y chromosome. Offense was measured for the following dyadic pairs: Group 1 (DBA1 tested against a DBA1 opponent); Group 2 (DBA1 tested against a DBA1.C57BL10-Y opponent); Group 3 (DBA1.C57BL10-Y tested against a DBA1.C57BL10-Y opponent); and Group 4 (DBA1.C57BL10-Y tested against a DBA1 opponent). Group 1 was more aggressive than Group 3, whereas Group 2 was no more aggressive than Group 4. Thus, when the experimental and opponent pairs have the same Y chromosome, the congenics differ in offense, whereas when the experimental and opponent pairs have different Y chromosomes, the congenics do not differ in offense. These findings are consistent with the hypothesis that these Y chromosomes affect the display of and response to social or other stimuli for offense of mice. These stimuli may be individual recognition chemosignals in urine.     

Attenuation of amphetamine-stereotypy by mesostriatal dopamine depletion enhances plasma corticosterone: implications for stereotypy as a coping response

The relationship between amphetamine-induced stereotyped behavior and a neuroendocrine index of arousal, plasma corticosterone (CCS), was investigated. 6-Hydroxydopamine lesions of the caudate-putamen, which produced dopamine depletions of 60%, blocked stereotypy and prolonged the elevation in corticosterone associated with d-amphetamine treatment (5 mg/kg). Similar dopamine depleting lesions of the nucleus accumbens, which attenuated the locomotor, but not the stereotypic, response to AMPH did not have this effect on CCS. This pattern of results supports the hypothesis that stereotypy has a coping function which may serve to alter arousal and further suggests important differences between the nigrostriatal and mesolimbic dopamine projections in modulating the responsiveness of the neuroendocrine system. These results have implications for understanding the function of behavioral stereotypies common to a number of psychopathological conditions, including schizophrenia and childhood autism.