Paediatric inflammatory multisystem syndrome in Canada: population-based surveillance and role of SARS-CoV-2 linkage

BACKGROUND

Paediatric inflammatory multisystem syndrome (PIMS) is a rare condition temporally associated with SARS-CoV-2 infection. Using national surveillance data, we compare presenting features and outcomes among children hospitalized with PIMS by SARS-CoV-2 linkage, and identify risk factors for intensive care (ICU).

METHODS

Cases were reported to the Canadian Paediatric Surveillance Program by a network of >2800 pediatricians between March 2020 and May 2021. Patients with positive versus negative SARS-CoV-2 linkages were compared, with positive linkage defined as any positive molecular or serologic test or close contact with confirmed COVID-19. ICU risk factors were identified with multivariable modified Poisson regression.

RESULTS

We identified 406 children hospitalized with PIMS, including 49.8% with positive SARS-CoV-2 linkages, 26.1% with negative linkages, and 24.1% with unknown linkages. The median age was 5.4 years (IQR 2.5-9.8), 60% were male, and 83% had no comorbidities. Compared to cases with negative linkages, children with positive linkages experienced more cardiac involvement (58.8% vs. 37.4%; p < 0.001), gastrointestinal symptoms (88.6% vs. 63.2%; p < 0.001), and shock (60.9% vs. 16.0%; p < 0.001). Children aged ≥6 years and those with positive linkages were more likely to require ICU.

CONCLUSIONS

Although rare, 30% of PIMS hospitalizations required ICU or respiratory/hemodynamic support, particularly those with positive SARS-CoV-2 linkages.

IMPACT

We describe 406 children hospitalized with paediatric inflammatory multisystem syndrome (PIMS) using nationwide surveillance data, the largest study of PIMS in Canada to date. Our surveillance case definition of PIMS did not require a history of SARS-CoV-2 exposure, and we therefore describe associations of SARS-CoV-2 linkages on clinical features and outcomes of children with PIMS. Children with positive SARS-CoV-2 linkages were older, had more gastrointestinal and cardiac involvement, and hyperinflammatory laboratory picture. Although PIMS is rare, one-third required admission to intensive care, with the greatest risk amongst those aged ≥6 years and those with a SARS-CoV-2 linkage.

Resource use and disease severity of children hospitalized for COVID-19 versus multisystem inflammatory syndrome in children (MIS-C) in Canada

Background

Direct comparisons of paediatric hospitalizations for acute coronavirus disease 2019 (COVID-19) and multisystem inflammatory syndrome in children (MIS-C) can inform health system planning. We describe the absolute and relative hospital burden of acute paediatric COVID-19 and MIS-C in Canada.

Methods

This national prospective study was conducted via the Canadian Paediatric Surveillance Program from March 2020-May 2021. Children younger than 18 years old and hospitalized for acute COVID-19 or MIS-C were included in the analysis. Outcomes included supplemental oxygen (low-flow oxygen or high-flow nasal cannula), ventilation (non-invasive or conventional mechanical), vasopressors, paediatric intensive care unit (PICU) admission, or death. Adjusted risk differences (aRD) and 95% confidence intervals (CI) were calculated to identify factors associated with each diagnosis.

Results

Overall, we identified 330 children hospitalized for acute COVID-19 (including five deaths) and 208 hospitalized for MIS-C (including zero deaths); PICU admission was required for 49.5% of MIS-C hospitalizations versus 18.2% of acute COVID-19 hospitalizations (aRD 20.3; 95% CI, 9.9-30.8). Resource use differed by age, with children younger than one year hospitalized more often for acute COVID-19 (aRD 43.4% versus MIS-C; 95% CI, 37.7-49.1) and more children 5-11 years hospitalized for MIS-C (aRD 38.9% vs. acute COVID-19; 95% CI, 31.0-46.9).

Conclusion

While there were more hospitalizations and deaths from acute paediatric COVID-19, MIS-C cases were more severe, requiring more intensive care and vasopressor support. Our findings suggest that both acute COVID-19 and MIS-C should be considered when assessing the overall burden of severe acute respiratory syndrome coronavirus 2 in hospitalized children.

Rates of and factors associated with exclusive and any breastfeeding at six months in Canada: an analysis of population-based cross-sectional data

BACKGROUND

Breastfeeding has many health, economic and environmental benefits for both the infant and pregnant individual. Due to these benefits, the World Health Organization and Health Canada recommend exclusive breastfeeding for the first six months of life. The purpose of this study is to examine the prevalence of exclusive and any breastfeeding in Canada for at least six months, and factors associated with breastfeeding cessation prior to six months.

METHODS

We performed a secondary analysis of breastfeeding-related questions asked on the cross-sectional 2017-2018 Canadian Community Health Survey. Our sample comprised 5,392 females aged 15-55 who had given birth in the five years preceding the survey. Descriptive statistics were carried out to assess the proportion of females exclusively breastfeeding and doing any breastfeeding for at least six months by demographic and behavioural factors. We also assessed, by baby's age, trends in the introduction of solids and liquids, breastfeeding cessation and the reasons females stopped breastfeeding. Multivariate log binominal regression was used to examine the association between breastfeeding at six months and selected maternal characteristics hypothesized a priori to be associated with breastfeeding behaviour.

RESULTS

Overall, for at least six months, 35.6% (95% confidence interval (CI): 33.3%-37.8%) of females breastfed exclusively and 62.2% (95% CI: 60.0%-64.4%) did any breastfeeding. The largest decline in exclusive breastfeeding occurred in the first month. Factors most strongly associated with breastfeeding for at least six months were having a bachelor's or higher degree, having a normal body mass index, being married and daily co-sleeping. Insufficient milk supply was given as the most common reason for breastfeeding cessation irrespective of when females stopped breastfeeding.

CONCLUSION

Six-month exclusive breastfeeding rates in Canada remain below targets set by the World Health Assembly. Continued efforts, including investment in monitoring of breastfeeding rates, are needed to promote and support exclusive breastfeeding, especially among females vulnerable to early cessation.

Prevalence and patterns of chronic disease multimorbidity and associated determinants in Canada

INTRODUCTION

Multimorbidity is increasingly recognized as a key issue in the prevention and management of chronic diseases. We examined the prevalence and correlates of chronic disease multimorbidity in the general adult Canadian population in relation to age and other key determinants.

METHODS

We extracted data from the Canadian Community Health Survey 2011/12 on 105 416 Canadian adults. We analysed the data according to the number of multimorbidities (defined as 2+ or 3+ diseases from a list of 9) and examined the determinants of multimorbidity using regression analyses.

RESULTS

Our findings show that 12.9% of Canadians report 2+ chronic diseases and 3.9% report 3+ chronic diseases. Those reporting 3 or more chronic diseases were more likely to be female, older, living in the lowest income quintile and to have not completed high school. In the overall population, social deprivation is associated with a 3.7 odds of multimorbidity, but when examined across age groups, the odds of multimorbidity were notably higher in middle age, 7.5 for those aged 35 to 49 years and 5.4 for those aged 50 to 64 years.

DISCUSSION

As the proportion of Canadians living with multiple chronic diseases increases, we need to assess chronic disease from a holistic perspective that captures multimorbidity and upstream factors, to facilitate broader and more context-appropriate associations with healthy living, quality of life, health care costs and mortality. Special consideration should be given to the role that social deprivation plays in the development of multimorbidity. Canadians living in the lowest socioeconomic group are not only more likely to develop multimorbidity, but the onset of multimorbidity is also likely to be significantly earlier.

Rehabilitation of visual processing deficits following brain injury

Visual processing deficits are a common sequelae in individuals who have sustained a brain injury, Visual processing includes the acquisition of visual information and the appropriate use and manipulation of that information based upon task or environmental demands, Following brain injury, visual processing deficits can manifest in various ways, and will likely interfere with the patient's progress and rehabilitation outcome, This article describes the importance of understanding and accurately identifying visual processing deficits and implementing specific rehabilitation strategies to maximize functional independence.

Developing a method to estimate practice denominators for a national Canadian electronic medical record database

BACKGROUND

Calculating disease prevalence requires both a numerator (number of persons with a disease) and a matching denominator (the 'population at risk' being studied). Determining primary care practice denominators is challenging.

OBJECTIVE

To develop and test a method to calculate primary care practice denominators.

METHODS

We compared a 'corrected yearly contact group', or practice population, with the number of patients enrolled with practices. The yearly contact group was the set of patients with a visit noted in the electronic medical records during the past year. The correction factor was the proportion of patients that reported contacting their physician in the past year. Eighty-one physicians from Toronto and Kingston, Ontario, provided data. The main outcome measure was the ratio of practice population to the number of enrolled patients. Other measures included the change in ratio over 2 years, differences between locations, and differences by provider, practice and patient characteristics.

RESULTS

The ratio of practice population to enrolled patients was 1.03 in 2010 (95% confidence interval 1.00 to 1.05) and 1.03 in 2011 (95% confidence interval 1.00 to 1.05). There was no change in the ratio over time. Ratios by location, provider or practice characteristics differed by less than 10%. There was a slight under-estimation of practice population for younger male patients and over-estimation for female patients.

CONCLUSION

This method provided a denominator that was reasonably similar to the enrolled population and was stable over time and by location, provider and practice characteristics. In regions without patient enrollment, this may provide an estimate of practice denominators.

Magnetographic assessment of fetal hiccups and their effect on fetal heart rhythm

Fetal hiccups emerge as early as nine weeks post-conception, being the predominant diaphragmatic movement before 26 weeks of gestation. They are considered as a programmed isometric inspiratory muscle exercise of the fetus in preparation for the post-natal respiratory function, or a manifestation of a reflex circuitry underlying the development of suckling and gasping patterns. The present paper provides the first evidence of non-invasive biomagnetic measurements of the diaphragm spasmodic contractions associated with fetal hiccups. The magnetic field patterns generated by fetal hiccups exhibit well-defined morphological features, consisting of an initial high frequency transient waveform followed by a more prolonged low frequency component. This pattern is consistent across recordings obtained from two fetal subjects, and it is confirmed by signals recorded in a neonatal subject. These results demonstrate that fetal biomagnetometry can provide insights into the electrophysiological mechanisms of diaphragm motor function in the fetus. Additionally, we study the correlation between hiccup events and fetal cardiac rhythm and provide evidence that hiccups may modulate the fetal heart rate during the last trimester of pregnancy.

Mild brain injury: an overview

This special issue of Applied Neuropsychology focuses on mild brain injury. This article provides an overview of mild brain injury, including its epidemiology, etiology, diagnostic criteria, and clinical symptoms. The contributing authors discuss various issues related to this topic, and divergent views are presented. Specifically, these include causes, symptoms, assessment, and recovery from mild brain injury. In addition, rehabilitation and forensic aspects of mild brain injury are discussed. Collectively, it is anticipated that this special issue will help to clarify the nature of mild brain injury and stimulate additional interest and research into this phenomenon.

Neuropsychological evaluation in rehabilitation planning and evaluation of functional skills

This paper focuses on the benefits of neuropsychological assessment for evaluating a brain-injured person's functional abilities and rehabilitation needs. The importance of early assessment in addressing these goals is discussed. Strengths and weaknesses of neuropsychological assessment for predicting a person's ability to participate in normal activities of daily living are considered. Test data taken alone often lack ecological validity, but nevertheless, specific test findings can be used to predict functional skills. The ecological validity of neuropsychological testing can be extended by observing the patient's approach to tasks in the assessment environment and by observing the patient in his or her normal activities. Evaluation information obtained by allied rehabilitation professionals, including occupational and speech and language therapies, can be integrated with neuropsychological test data to both extend the generalizability of our findings and to validate hypotheses generated from our test data. The use of neuropsychological test data in planning a cognitive rehabilitation program is also considered.

Simultaneous measurement of adenosine and hypoxanthine in human umbilical cord plasma using reversed-phase high-performance liquid chromatography with photodiode-array detection and on-line validation of peak purity

A new, robust and sensitive reversed-phase high-performance liquid chromatographic method was developed for concomitant measurement of plasma concentrations of the ATP catabolites adenosine and hypoxanthine in human umbilical cord blood. Deproteinized cord plasma was chromatographed on Hypersil C18 columns, using UV photodiode-array detection, spectral analysis of peaks and on-line confirmation of peak purity. Elution with a gradient of acetonitrile-tetrahydrofuran in ammonium dihydrogen phosphate buffer pH 4.7, yielded sharp, well-resolved peaks of adenosine and hypoxanthine within 16 min. Peak areas were quantified from external calibration curves and converted to plasma concentrations via cord blood hematocrits. In seven deliveries, gestational ages 32-40 weeks, adenosine (range, 0.1-2.1 microM) was less than hypoxanthine (range, 1.6-18.5 microM) in the same cord plasma sample. Arteriovenous levels of each purine were similar, except in an abruptio placenta delivery.

Emotional Consequences and Psychotherapy for Individuals With Mild Brain Injury

It is well documented that even mild brain injury can manifest with significant cognitive and emotional symptoms. Undoubtedly, these alterations may result in career, social, and personal consequences. In this article we discuss and summarize psychotherapeutic approaches to be used for individuals with mild brain injury. The primary focus is on providing education and assistance for developing coping strategies. Once an individual recognizes, accepts, and adjusts to the limitations resulting from the brain injury, then a more favorable level of adjustment can occur.

Efficacy of neuropsychological rehabilitation for mild-moderate traumatic brain injury

The growing literature on cognitive rehabilitation is increasingly demanding more evaluation related to the validity of such therapy. The current research addresses some of the criticisms of previous efficacy studies and provides support for the effectiveness of cognitive rehabilitation according to a specific treatment protocol employed at an outpatient rehabilitation program. Stringent subject selection criterion were utilized to maximize the validity of the statistical comparisons of selected pre- and post- rehabilitation neuropsychological test scores and cognitive level of functioning. Results supported improvement in performance on selected neuropsychological test scores and cognitive functioning following cognitive rehabilitation. Limited validating evidence for behavioral indicators of level of cognitive functioning were obtained through correlations of behavioral ratings to their corresponding neuropsychological test scores. Results suggest that traditional measures of efficacy of cognitive rehabilitation may be insensitive to the cognitive sequalae of mild head injury due, in part, to compensatory strategies invoked by the subjects.

Resolution of unilateral fetal hydrothorax with associated non-immune hydrops after intrauterine thoracentesis

Congenital hydrothorax has been successfully managed in utero by two different treatment modalities: thoracentesis and pleuroamniotic shunting. Unfortunately, there is a paucity of data as to which method is better for the management of this problem. This case report supports the use of thoracentesis as the initial procedure for primary fetal hydrothorax. We report a pregnancy complicated by primary fetal hydrothorax with non-immune hydrops that completely resolved after two thoracenteses in the early third trimester. Complete resolution was maintained throughout pregnancy without the need for further antenatal or neonatal intervention, i.e. further thoracentesis, pleuroamniotic shunt placement, intubation, or chest and/or abdominal tube placement. The child was delivered at 42 weeks and is doing well without problems at 1 year of age. We believe that intrauterine thoracentesis should be the initial procedure of choice for the treatment of primary fetal hydrothorax with mediastinal shift, and pleuroamniotic shunting should be reserved for cases that require repetitive thoracenteses.

Single versus composite score discriminative validity with the Halstead-Reitan Battery and the Stroop Test in mild brain injury

The predictive validity of single measures from the Halstead-Reitan Neuropsychological Test Battery and Stroop Neuropsychological Screening Test were evaluated in a sample of 25 mild traumatic brain-injured and 25 neurologically normal subjects and compared to the accuracy of composite score measures, specifically the General Neuropsychological Deficit Scale and the Halstead Impairment Index. Whereas several measures from the Halstead Impairment Index achieved significantly better than chance prediction, the two summary measures from the Halstead-Reitan Neuropsychological Test Battery predicted the neurological status of the subjects with the most accuracy. The Stroop Neuropsychological Screening Test did not perform well as a single predictor. Together, these results suggest that single-measure screening tests do not predict mild brain-injury as well as composite neuropsychological measures. The results also give credence to the argument of comprehensive testing for brain-injured patients whose injuries are deemed medically mild.

Laparoscopic cholecystectomy in the second trimester of pregnancy. A case report

Laparoscopic cholecystectomy was performed at 19 weeks' gestation for recurrent cholecystitis. The procedure was completed without complications, and the patient was discharged on the second postoperative day. Thereafter, the pregnancy progressed uneventfully.

Terminal deletion of 7q presenting in utero with a truncus arteriosus and nonimmune hydrops

Terminal deletion of 7q presents with variable anatomical and developmental findings. This case is the first reported in utero diagnosis based on cytogenetic findings and in utero demonstration of resolving congestive heart failure due to a truncus arteriosus.

Development of the Eagle-Barrett (prune belly) syndrome and a thickened, poorly functional bladder wall after early second-trimester decompression of fetal megacystis

The management of bladder outlet obstruction in the fetus remains a debated issue. Recent data suggest the use of cystocentesis for the possible relief of the bladder neck obstruction or for the opening of posterior urethral valves. This case report adds further support for the use of cystocentesis and observation prior to the placement of an indwelling bladder shunt. The case further demonstrates that relief of the megacystis may not prevent prune belly syndrome, bladder dysfunction or renal damage. Finally, the case demonstrates that severe oligohydramnios in the second trimester need not invariably result in pulmonary hypoplasia.

Cortisol effect on atrial natriuretic factor response to hypertonic saline in fetal sheep

Atrial natriuretic factor (ANF) is released following a variety of stimuli including hypertonicity in the fetus. To study the effect that cortisol has on fetal ANF release, seven chronically instrumented fetal sheep at gestational ages ranging from 110-132 days were studied in two experiments. In one experiment (CORTISOL), a continuous cortisol (with EtOH vehicle) infusion was maintained. In the other experiment (CONTROL), the vehicle was infused alone. Ninety minutes from the start of this infusion, a hypertonic saline bolus (12 meg/kg) was given. Osmolality, ANF, cortisol, pH, PO2, PCO2, mean arterial pressure (MAP), heart rate (HR), and hematocrit (HCT) were followed over a 120-min period. Following hypertonic saline, serum osmolality increased from 290.6 +/- 2.3 mOsm/kg to 310.4 +/- 2.5 mOsm/kg (P < 0.01). Baseline values for pH, PO2, and HCT were 7.37 +/- 0.01, 22.5 +/- 1.6 mmHg, and 33.9 +/- 1.2 respectively. Each of these variables fell following hypertonic saline infusion. MAP rose from 40.6 +/- 1.7 mmHg to 47.0 +/- 2.4 mmHg (P < 0.01). However, there were no differences between CONTROL and CORTISOL experiments in any of the above changes. Cortisol levels in the CONTROL group did not change during the course of the experiment, but in the CORTISOL group rose from 8.2 +/- 4.4 ng/ml to 33.0 +/- 9.9 ng/ml (P = 0.02). Plasma ANF levels prior to hypertonic saline were similar (124.8 +/- 17.7 pg/ml and 127.6 +/- 26.1 pg/ml) in the CONTROL and CORTISOL groups respectively and rose following hypertonic saline to a maximum of 155.3 +/- 16.6 pg/ml and 189.2 +/- 42.7 pg/ml (P = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor responses to volume expansion in pregnant and nonpregnant sheep

Isotonic volume expansion results in atrial natriuretic factor release by cardiac myocytes. Because pregnancy produces well-established alterations in fluid homeostasis and cardiovascular function, changes in atrial natriuretic factor responses may also occur. This study compares plasma atrial natriuretic factor responses to short-term volume expansion in pregnant and nonpregnant sheep. Seven pregnant and six nonpregnant ewes were chronically instrumented and subjected to a series of four experiments consisting of a control group (no infusion) and groups that received 10 ml/kg, 25 ml/kg, and 40 ml/kg isotonic saline infusion over a 30-minute period. The order of the experiments was random and separated by greater than or equal to 48 hours. Plasma atrial natriuretic factor, osmolality, right atrial pressure, blood pressure, and urine flow were measured over a 150-minute observation period. After volume expansion, plasma atrial natriuretic factor levels rose significantly from 39 +/- 4 pg/ml (mean +/- SEM) to 49 +/- 7 pg/ml, 36 +/- 4 pg/ml to 62 +/- 19 pg/ml, and 39 +/- 6 pg/ml to 67 +/- 14 pg/ml in the nonpregnant group 10 ml/kg, 25 ml/kg, and 40 ml/kg experiments, respectively. In the pregnant groups, plasma atrial natriuretic factor levels rose from 50 +/- 2 pg/ml to 75 +/- 20 pg/ml, 43 +/- 5 pg/ml to 57 +/- 5 pg/ml, and 46 +/- 4 pg/ml to 67 +/- 7 pg/ml, respectively. Differences in atrial natriuretic factor responses were not seen between pregnant and nonpregnant groups at any volume expansion level. As expected, atrial pressure and urine flow significantly increased after all volume expansion experiments. Pregnant and nonpregnant groups were similar with respect to atrial pressure and urine flow responses. Over various volume expansion levels significant associations were seen between atrial pressure, atrial natriuretic factor, and urine flow. These relationships were unaltered by pregnancy. In summary, atrial natriuretic factor responses to volume expansion do not appear to differ between pregnant and nonpregnant sheep.

Hypomandibular faciocranial dysostosis: report of an affected sib and follow-up

Hypomandibular faciocranial dysostosis is a condition heretofore described only in a single case. We report the birth of an affected sister along with follow-up information on the initial surviving patient. While a primary error in neural crest development was postulated in this syndrome, subsequently discovered anatomical abnormalities suggest a more complex pathogenesis.

Measurement of hypoxanthine and xanthine in late-gestation human amniotic fluid by reversed-phase high-performance liquid chromatography with photodiode-array detection

A robust analytical method was developed for measurement of hypoxanthine and xanthine in late-gestation human amniotic fluid by reversed-phase high-performance liquid chromatography using diodearray detection. Purity of analyte peaks was confirmed via on-line analysis of peak spectra utilizing the purity parameter treatment of spectral data. Amniotic fluid obtained by amniocentesis was deproteinized by centrifugal ultrafiltration and chromatographed on an octadecylsilica column using isocratic elution with 1% (v/v) acetonitrile in 0.05 M ammonium dihydrogenphosphate pH 6.0; hypoxanthine and xanthine were resolved, but the hypoxanthine peak was not pure. Chromatography on a column of polar endcapped octadecylsilica, using similar mobile phase conditions, yielded spectrally pure peaks of hypoxanthine xanthine. Hypoxanthine and xanthine levels in amniotic fluid from fourteen patients, gestational age 34-39 weeks, ranged from 0.56 to 2.74 microM and 1.62 to 5.52 microM, respectively.

Effect of cortisol on vasopressin response to hypertonic saline in fetal sheep

To determine the effect of cortisol on vasopressin responses to hyperosmolality, we infused hypertonic saline (HS) (12 meq/kg NaCl) into nine chronically cannulated fetal sheep ranging from 110 to 132 days of gestation. The experiment was performed twice on each fetus, once during a continuous cortisol infusion and once during a vehicle infusion. Administration of HS resulted in a prompt increase in serum osmolality from 292.1 +/- 1.8 to 310.4 +/- 2.5 mosmol/kg. Decreases were seen in pH, partial pressure of O2, and hematocrit from 7.37 +/- 0.01 to 7.31 +/- 0.01, from 22.5 +/- 1.6 to 20.0 +/- 2.0 mmHg, and from 35.6 +/- 1.7 to 32.6 +/- 1.6, respectively. Mean arterial pressure increased from 41.3 +/- 1.4 to 48.9 +/- 2.0 mmHg (P less than 0.01). Arginine vasopressin (AVP) rose from base line after HS (P = 0.11 vehicle experiments, P = 0.04 cortisol experiments), and AVP responses were greater in the cortisol experiments than in the vehicle experiments (delta AVP = 21.9 +/- 10.9 vs. 3.1 +/- 0.9 pg/ml, P = 0.05). Also there was a correlation noted between differences in AVP response and cortisol levels (P less than 0.04). We conclude that cortisol exerts a positive influence on the AVP response to HS in fetal sheep.

Transfer of perceptual learning: role of tactual-kinesthetic feedback reexamined

Albino rats were pre-exposed to stimuli in an otherwise visually sparse environment, with visibility and opportunity to manipulate the forms controlled during rearing. Analysis indicated that pre-exposing animals to stimuli which provided either tactual-kinesthetic feedback or highly visible forms significantly facilitated subsequent discrimination learning. The findings question the adequacy of either an attention-getting or tactual-kinesthetic feedback to account for differences in transfer effects in studies using two- and three-dimensional forms. It is suggested that the visibility of the forms and the opportunity to inspect the forms during pre-exposure is the important variable in studies of this type.

Early social isolation of the domestic cat: responses to separation from social and nonsocial rearing stimuli

The relative contributions of social-rearing stimuli (a mother and/or a littermate) and nonsocial-rearing stimuli (a brooder) to the formation and decline of infant kitten attachments were assessed by counting the frequency of distress cries produced by separation from the following rearing conditions: (1) mother-littermate; (2) mother-only; (3) brooder-littermate; and (4) brooder-only. Four male and 4 female kittens were reared in each condition. Each kitten was separated from its rearing condition once a week, from 2 until 5 weeks of age, and placed in open field for 15 min. The frequency of distress cries in both littermate-reared groups did not significantly differ throughout the experiment. The frequency was consistently high until 5 weeks of age when distress cries were significantly reduced. The frequency of distress cries consistently increased in the mother-only-reared kittens with repeated separations, but consistently decreased in the brooder-only-reared kittens. The results were interpreted as being commensurate with the social conditions at the time of separation.

The effects of social isolation on the behavior of juvenile domestic cats

The effects of social isolation on the behavior of juvenile domestic cats were assessed by rearing 4 male and 4 female infant kittens in each of the following rearing conditions: (1) mother-littermate; (2) mother-only; (3) brooder-littermate; and (4) brooder-only. They were then tested twice a week individually and twice a week socially from 2 to 6 1/2 months of age in a playroom, utilizing multiple categories of behavior. The mother-only-reared juveniles were hyperactive in both object play (when tested individually) and social play. The brooder-only-reared kittens displayed enhanced socially directed behavior and were generally hypergregarious, whereas the brooder-littermate-reared kittens displayed retarded social behavior. Observations indicated that littermate-deprived kittens did not learn social communication skills and that some prolonged separation effects existed for littermate-reared kittens. The results suggest that the determinants of social play are more complex than the determinants of object play.

Critical periods for early experience in transfer of perceptual learning

It has generally been found that early experience with stimuli enhances the subsequent discriminability of these forms. To determine if critical periods exist for yielding this early experience effect, albino rats were given either early (20 to 55 days of age) or late (55 to 90 days of age) stimulus experience. A third pre-exposure group received experience with the to-be-discriminated forms from 20 to 90 days of age. Control animals, with no stimulus pre-exposure, were run on the discrimination problem at either 55 or 90 days of age. The basic early experience effect was replicated in that early experience with stimuli facilitated their subsequent discriminability. However, no evidence for critical periods of early experience was obtained.

Effect of exposure to a single stimulus on transfer of perceptual learning

Albino rats reared in a visually sparse environment were pre-exposed to either both, one, or neither of the to-be-discriminated stimuli. Both groups which received early stimulus experience learned the discrimination task in significantly fewer trials than did the nonexposed control group, and the group which received early experience with both stimuli was superior to the group pre-exposed to only one of the to-be-discriminated stimuli. The results imply that greatest facilitation by early experience of later discrimination learning will occur if S is allowed to compare the to-be-discriminated stimuli in his rearing environment.

Role of tactual-kinesthetic feedback in transfer of perceptual learning for rats with pigmented irises

Hooded rats were pre-exposed to circles and triangles in an otherwise visually sparse environment where opportunity to manipulate the forms was varied for the early experience groups. Although early experience with these stimuli enhanced their later discriminability over that shown by control animals who received no early experience, opportunity to manipulate the forms produced no additional gain in perceptual learning relative to Ss not allowed to manipulate the pre-exposed shapes. The findings restrict the generality of the tactual-kinesthetic feedback hypothesis.

Hippocampal theta and learning: some further comments

Douglas' reply to Bennett's criticism is discussed. The author concluded that Douglas may be correct in questioning Adey's hypothesis that hippocampal theta activity reflects the role of this structure in mediating the learning process but not on the basis of many of the arguments Douglas has made.

Hippocampal theta activity and learning: a reply to Douglas

Adey and his associates have asserted that theta electrical activity recorded from the hippocampus during learning and performance reflects the role of this structure in information processing, decision making and memory consolidation. This notion was recently questioned by Douglas (1967) who concluded that the tasks employed by Adey and his associates to assess theta activity were tasks which the lesion literature indicated do not requite hippocampal functioning to be learned. The present paper questions Douglas' assertion by describing studies in the lesion literature which demonstrate that the tasks used by Adey and his co-workers may actually require hippocampal functioning to be learned.