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Biomedical subjects

J M Warren

Publications and source records attributed to J M Warren.

At least 19 recordsLinked to original sources
PubMed1989

Selective sparing after lesions of visual cortex in newborn kittens.

Previous findings are discordant regarding the effects of perinatal lesions of Cortical Areas 17 and 18 on visual discrimination learning in cats. Three potential determinants of such sparing were investigated: age at lesion (4 or 181 days), age at testing (3 or 9 months), and stimulus complexity. Age at testing was not significant, but performance varied with stimulus complexity and cortical damage, and there was an interaction between stimulus complexity and age at lesion. Both operated groups were transiently impaired in discriminating objects and subsequently learned to discriminate simple 2-dimensional patterns as well as done by controls, but the lesion groups were permanently impaired in discriminating similar patterns circumscribed by irrelevant lines. The age-at-lesion groups differed, however, in discriminating patterns masked by superimposed lines. The group lesioned at 181 days was severely impaired at both acquisition and subsequent intercurrent performance; the group lesioned at 4 days was impaired only at intercurrent performance. This study suggests that sparing after early postnatal damage of Areas 17 and 18 occurs only under limited circumstances.

Animals↗
PubMed1986

Appetitive learning by old mice.

Groups of C57BL/6J (B6) and DBA/2J (D2) mice, aged 100 to 700 days, were trained on 7 appetitive learning tasks in order to determine which tasks might be suitable for studies of learning by old mice. Old B6 and D2 mice were both deficient in learning a discrimination reversal and two complex maze tasks; age did not affect performance on a simple spatial discrimination by subjects from either strain. Three tasks yielded strain-specific results. Old B6, but not old D2, animals were impaired on a visual discrimination problem. On a test of latent learning, old B6 animals were superior to younger mice, but the reverse trend characterized the D2 mice. Older D2 mice were retarded on a food-seeking task; B6 mice of all ages failed this test. The deficits observed in learning by old mice are thus strain- as well as task-specific. However, the deprivation procedures of this experiment resulted in excessive mortality in the oldest groups of mice, indicating that appetitive learning is contraindicated as a method for investigating learning by old mice.

Aging↗
PubMed1982

Effects of environmental enrichment on old mice.

Fifteen male C57BL/6J mice, exposed to an enriched environment from age 600 to 750 days, were compared with 15 matched controls on 4 learning problems and an activity test. The enriched mice were significantly superior on an incidental learning and a food-seeking task, but did not differ significantly from controls on a brightness discrimination task, the Lashley III maze and an activity test. The relative abundance of high and low ribonucleic acid-containing cerebrocortical cells differed significantly between groups; the enriched mice had more cells with very high levels of RNA. The mammalian brain appears to remain responsive to environmental enrichment well into advanced age.

Age Factors↗
PubMed1976

Florid and subclinical rickets among immigrant children in Glasgow.

200 Asian 300 African, Chinese, or Scottish children were examined for clinical, biochemical, and radiological evidence of vitamin-D deficiency. Among the Asians there were 10 with florid rickets and 15 with subclinical rickets. Among the African, Chinese, and Scottish children there were no cases of florid rickets and only 7 cases of subclinical rickets (3 African, 3 Chinese, and 1 Scottish). Loss of metaphyseal definition is considered to be the radiological pattern of minimal active rickets and metaphyseal bands to represent the healing stage. Serum 25-hydroxycholecalciferol concentrations were low in clinical and subclinical minimal active rickets although there was some overlap with the wide range found in the "normal" group. Elevated serum-alkaline-phosphatase levels alone should not be regarded as indicating vitamin-D deficiency. The continuing prevalence of rickets in Asian children and in particular among schoolchildren warrants immediate action, which is long overdue.

Africa↗
PubMed1976

Marginal and extramarginal cortical lesions and visual discrimination by cats.

Seventy-five cats learned a shape discrimination with zero, one, or two irrelevant cues. They were then subjected to sham operations (n = 34), ablation of the marginal and splenial gyri (n = 9), or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised four groups, three with small (EM1, n = 9), intermediate (EM2, n = 10), and large (EM3, n = 9) decortications, and a fourth group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN, n = 4). The cats with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Two lines of evidence indicate that their behavioral defects resulted from different neural dysfunctions. (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Cats with extramarginal ablations and strong LGN degeneration were no more severely impaired than were subjects with comparable extramarginal damage and little or no LGN degeneration. While the nature of the two kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys.

Animals↗
PubMed1976

The search for cerebral dominance in monkeys.

Twelve monkeys with statistically significant and consistent manual preferences on three handedness tests were subjected to unilateral ablations in the association cortex. Eight received lesions in the foveal prestriate cortex, and four lesions in the dorsolateral frontal cortex; half the subjects in each group were operated on the dominant, and half on the nondominant hemisphere for handedness. The unilateral posterior preparations were significantly inferior to the control group of four unilateral frontals and five sham operated monkeys on three series of visual pattern discrimination problems. No evidence was obtained that lesions in the nondominant hemisphere. The results of this and four other experiments indicate that there is no cerebral dominance for problem-solving in monkeys. Recent research indicates that handedness in rhesus monkeys is only superficially similar to handedness in humans; thus, monkeys appear to lack cerebral dominance for handedness as well as for cognitive behavior.

Animals↗
PubMed1976

Metabolic balances of strontium in man.

Stable strontium balances were determined in man under strictly controlled dietary conditions in control studies and during both oral and intravenous administration of stable strontium. The diet contained about 1 mg strontium per day and most of this (88%) was excreted in stool while 17.5 per cent was excreted in urine, so that the balance was very slightly negative. During the oral intake of 1536 mg strontium per day, given as the lactate, the urinary and the fecal strontium excretions increased markedly and the balance became strongly positive. During the 6-day periods of intravenous infusions of stable strontium as the gluconate, 30-40 per cent of the infused amount was excreted in the urine and 5-10 per cent in stool. A high percentage of the strontium retained during both oral and intravenous administration was excreted in 30 days after the discontinuation of the strontium administration and there was no evidence of long term retention. The administration of stable strontium, given either orally or intravenously, was associated with an increase of the urinary calcium excretion.

Administration, Oral↗