Environmental complexity and central nervous system development and function

Environmental restriction or deprivation early in development can induce social, cognitive, affective, and motor abnormalities similar to those associated with autism. Conversely, rearing animals in larger, more complex environments results in enhanced brain structure and function, including increased brain weight, dendritic branching, neurogenesis, gene expression, and improved learning and memory. Moreover, in animal models of CNS insult (e.g., gene deletion), a more complex environment has attenuated or prevented the sequelae of the insult. Of relevance is the prevention of seizures and attenuation of their neuropathological sequelae as a consequence of exposure to a more complex environment. Relatively little attention, however, has been given to the issue of sensitive periods associated with such effects, the relative importance of social versus inanimate stimulation, or the unique contribution of exercise. Our studies have examined the effects of environmental complexity on the development of the restricted, repetitive behavior commonly observed in individuals with autism. In this model, a more complex environment substantially attenuates the development of the spontaneous and persistent stereotypies observed in deer mice reared in standard laboratory cages. Our findings support a sensitive period for such effects and suggest that early enrichment may have persistent neuroprotective effects after the animal is returned to a standard cage environment. Attenuation or prevention of repetitive behavior by environmental complexity was associated with increased neuronal metabolic activity, increased dendritic spine density, and elevated neurotrophin (BDNF) levels in brain regions that are part of cortical-basal ganglia circuitry. These effects were not observed in limbic areas such as the hippocampus.     

Hypertonic central nervous system complications from the viewpoint of the pathologist

Based on 2130 autopsies with a hypertension it is reported on the hypertensive CNS-lesions. The frequency of encephalomalacia was 12%. By 9.7% was founded brain haemorrhages. The relapse rate of haemorrhages was about 5%. The encephalomalacia existed by way of secondary finding in 24.7%, and the haemorrhage in 2.2%. The investigations showed an important arteriosclerosis by 39.8% in haemorrhages and by 51.6% in brain infarct. It was remarkable by the hypertensive brain haemorrhages a dominant right hemisphere.     

Language differences in verbal short-term memory do not exclusively originate in the process of subvocal rehearsal

Language differences in verbal short-term memory were investigated in two experiments. In Experiment 1, bilinguals with high competence in English and French and monolingual English adults with extremely limited knowledge of French were assessed on their serial recall of words and nonwords in both languages. In all cases recall accuracy was superior in the language with which individuals were most familiar, a first-language advantage that remained when variation due to differential rates of articulation in the two languages was taken into account. In Experiment 2, bilinguals recalled lists of English and French words with and without concurrent articulatory suppression. First-language superiority persisted under suppression, suggesting that the language differences in recall accuracy were not attributable to slower rates of subvocal rehearsal in the less familiar language. The findings indicate that language-specific differences in verbal short-term memory do not exclusively originate in the subvocal rehearsal process. It is suggested that one source of language-specific variation might relate to the use of long-term knowledge to support short-term memory performance.     

Height preferences in humans may not be universal: Evidence from the Datoga people of Tanzania

Many studies in Western societies have shown that women prefer relatively taller men as potential partners, whereas men prefer women who are slightly shorter than themselves. Here, we discuss possible limitations of previous results within the context of the stimuli used (i.e., differences in the perceived body size of female silhouettes). Our results show that, at least in a Polish sample (N = 231), modified stimuli did not essentially change the observed male-taller preferences. In contrast, we report height preferences in a traditional ethnic group, the Datoga people from Tanzania (N = 107), in which men and women preferred extreme sexual dimorphism in stature (SDS) sets (i.e., men and women chose women much taller or much shorter than themselves). Thus, our data do not accord with the suggestion of a universal preference for taller men, but rather suggests that height preferences may be influenced by cultural, environmental, and ecological conditions.     

Iatrogenic damage to the nervous system]

A survey is given of the most important findings in respect of iatrogenic damage to the nervous system on the basis of published reports and the author's own findings, taking special account of lumbar puncture and suboccipital puncture, myelography, contrast-medium encephalography, ventriculography and cerebral angiography. The possibility of damage such as the danger of embolism in diagnostic and therapeutic vascular puncture is referred to. Among the lesions caused in the course of therapy, the side-effects of treatment with drugs, effects of radiation, effects resulting from anesthesia, sequelae of neural therapy and of manual manipulations, sequelae of operations, and postvaccinal encephalopathies are discussed. The necessity of systematic morphological examinations for exact assessment of ioatrogenic lesions is stressed. Iatrogenic damage due to neglect of diagnostic and therapeutic measures is also considered.     

Sexual communication and domestication may give rise to the signal complexity necessary for the emergence of language: An indication from songbird studies

For language to be a vehicle of thought, protolanguage must develop a degree of complexity that allows for the syntactic manipulation of symbol sequences. Thus, before language emerged, a process in which signals became complex must have occurred. Here, we submit a scenario describing the process in which courtship songs gained in complexity during the course of domestication of Bengalese finches. By comparing domesticated Bengalese finches with their wild strain, white-rumped munias, we found that female preferences for complex songs were coupled with domesticated relaxed environments to give rise to song complexity. Furthermore, we found that the outcomes of domestication in Bengalese finches include decreased psychological and physiological stress reactions, decreased aggressiveness, and changed plumage colors. These characteristics are consistent with “domestication syndrome,” originally proposed for mammals but now possibly applicable to birds. Our finding that domestication was a cause of signal complexity might be helpful in considering the process of signal evolution in human language.     

Pigeons may not remember the stimuli that reinforced their recent behavior

In two experiments the conditioned reinforcing and delayed discriminative stimulus functions of stimuli that signal delays to reinforcement were studied. Pigeons' pecks to a center key produced delayed-matching-to-sample trials according to a variable-interval 60-s (or 30-s in 1 pigeon) schedule (Experiment 1) or a multiple variable-interval 20-s variable-interval 120-s schedule (Experiment 2). The trials consisted of a 2-s illumination of one of two sample key colors followed by delays ranging across phases from 0.1 to 27.0 s followed in turn by the presentation of matching and nonmatching comparison stimuli on the side keys. Pecks to the key color that matched the sample were reinforced with 4-s access to grain. Under some conditions of Experiment 1, pecks to nonmatching comparison stimuli produced a 4-s blackout and the start of the next interval. Under other conditions of Experiment 1 and each condition of Experiment 2, pecks to nonmatching stimuli had no effect and trials ended only when pigeons pecked the other, matching stimulus and received food. The functions relating pretrial response rates to delays differed markedly from those relating matching-to-sample accuracy to delays. Specifically, response rates remained relatively high until the longest delays (15.0 to 27.0 s) were arranged, at which point they fell to low levels. Matching accuracy was high at short delays, but fell to chance at delays between 3.0 and 9.0 s. In Experiment 2, both matching accuracy and response rates remained high over a wider range of delays in the variable-interval 120-s component relative to the variable-interval 20-s component. The difference in matching accuracy between the components was not due to an increased tendency in the variable-interval 20-s component toward proactive interference following short intervals. Thus, under these experimental conditions the conditioned reinforcing and the delayed discriminative functions of the sample stimulus depended on the same variables (delay and variable-interval value), but were nevertheless dissociated.     

Seeing the forest and not the trees: When impact uncertainty heightens causal complexity

This study attempts to isolate the effects of experiencing uncertainty on people's cognitive processes. I argue that people can believe that their actions affect the outcome (i.e. outcome control), but still face uncertainty regarding the extent to which actions will make a difference (i.e. impact uncertainty). To this end, I introduce a novel experimental paradigm which isolates the effects of impact uncertainty from outcome control. The findings revealed that after experiencing impact uncertainty, participants demonstrated greater causal complexity (i.e. more likely to make situational attributions and judge outcomes as having a “ripple effect”), but did not make fewer effort attributions for the outcomes. These findings demonstrate how the experience of impact uncertainty can affect cognitive processing, without compromising outcome control. Implications of these findings for developing more nuanced theories on control and uncertainty are discussed.     

Semantic priming from letter-searched primes occurs for low- but not high-frequency targets: automatic semantic access may not be a myth

Letter-search (LS) within a prime often eliminates semantic priming. In 2 lexical decision experiments, the authors found that priming from LS primes occurred for low-frequency (LF) but not high-frequency (HF) targets whether the target's word frequency was manipulated between or within participants and whether the prime-target pairs were associated symmetrically or forward asymmetrically. For the LF targets, LS priming was (a) equivalent for forward asymmetric and symmetric pairs and (b) equal to silent-read (SR) priming for forward asymmetric pairs but less than SR priming for symmetric pairs. The typical finding of greater SR priming for response times for LF than for HF targets occurred for symmetric priming but not for forward asymmetric priming, which showed the interaction for errors. The authors consider their findings' implications for various accounts of how LS affects priming and explain the findings within J. H. Neely and D. E. Keefe's (1989) 3-process model as follows: (a) LS eliminates expectancy and semantic matching but does not reduce semantic activation and (b) expectancy contributes to SR priming for HF targets but not for LF targets, whereas the opposite is so for semantic matching.     

Pigeons may not use dual coding in the radial maze analog task

Using a radial maze analog task, T. R. Zentall, J. N. Steirn, and P. Jackson-Smith (1990) found evidence that when a delay was interpolated early in a trial, pigeons coded locations retrospectively, but when the delay was interpolated late in the trial, they coded locations prospectively (support for a dual coding hypothesis). In Experiment 1 of the present study, the authors replicated the original finding of dual coding. In Experiments 2 and 3, they used a 2-alternative test procedure that does not require the assumption that pigeons' choice criterion, which changes over the course of the trial, is the same on delay and control trials. Under these conditions, the pigeons no longer showed evidence for dual coding. Instead, there was some evidence that they showed prospective coding, but a more parsimonious account of the results may be that the delay produced a relatively constant decrement in performance at all points of delay interpolation. The original finding of dual coding by Zentall et al. might have been biased by more impulsive choices early in control trials but not in delay trials and by a more stringent choice criterion late in delay trials.     

Stiff-person syndrome: autoimmunity and the central nervous system

Stiff-person syndrome (SPS) is a rare disease of severe progressive muscle stiffness in the spine and lower extremities with superimposed muscle spasms triggered by external stimuli. Patients with SPS are often referred for psychiatric evaluation and the psychiatrist may be the first to diagnosis SPS. Psychosocial stressors often precede the first manifestations of the disease; depression, anxiety, and alcohol abuse are comorbid illnesses. The identification of an association with antibodies to glutamic acid decarboxylase (GAD) was invaluable for definitively establishing a pathological basis for the disease; antibodies to amphiphysin and gephyrin are also found in cases of SPS but at much lower frequencies. Whether the antibodies inhibit GAD activity in vivo, target GAD-expressing neurons for immune-mediated destruction, are part of a wider immune process, or are merely a marker for destruction of GAD-expressing neurons by an independent neurodegenerative process is not yet clear. Both electromyography and the detection of GAD antibodies are useful in establishing a diagnosis of SPS. Treatment of SPS includes the use of immunomodulating therapies (plasmapheresis and intravenous immunoglobulins) and symptomatic treatment with benzodiazepines and baclofen. The use of tricyclic antidepressants and rapid withdrawal from therapy should be avoided.     

Adrenergic pharmacology: focus on the central nervous system

Norepinephrine and epinephrine are involved in the control of several important functions of the central nervous system (CNS), including sleep, arousal, mood, appetite, and autonomic outflow. Catecholamines control these functions through activation of a family of adrenergic receptors (ARs). The ARs are divided into three subfamilies (alpha1, alpha2, and beta) based on their pharmacologic properties, signaling mechanisms, and structure. ARs in the CNS are targets for several therapeutic agents used in the treatment of depression, obesity, hypertension, and other diseases. Not much is known, however, about the role of specific AR subtypes in the actions of these drugs. In this paper, we provide an overview of adrenergic pharmacology in the CNS, focusing on the pharmacologic properties of subtype-selective AR agonists and antagonists, the accessibility of these drugs to the CNS, and the distribution of ARs in different areas of the brain.     

Vigilance, personality and strength of the nervous system

Numerous attempts have been made to explain the overall level of performance and the change in performance over time in vigilance tasks in terms of the proposed inverted U relationship between performance and ‘arousal’. The present experiment investigated the effects on vigilance performance of the following variables: introversion, neuroticism, time of day, accessory sensory stimulation, ‘signal frequency’ and time on task. Some measures of subjective state and body temperature were also included. The behavioural measures of overall performance revealed interactions involving neuroticism and time of day, and between neuroticism and frequency. This may reflect the operation of response bias factors, though these may be influenced by ‘arousal’. There were also main effects for several of the factors which may have practical significance. There was a significant effect of time on task on all the behavioural measures but no clearcut effects of personality on the vigilance ‘decrement’. It is argued that the latter may not provide the most satisfactory test of the inverted U model and its relationship to personality. However, interactions between noise and time on task for some of the measures may have practical importance. Measures of subjective state showed a fall in the reported level of ‘arousal’ accompanied by a rise in reported ‘stress’ and ‘anxiety’ with time on task. Body temperature was higher after the task than before.     

Aspects of biochemical differentiation in the central nervous system

A demonstration of cell-specific patterns of development in the immature CNS is provided by examples of characteristic, cellspecific time-courses of enzyme development in different classes of brain cells isolated in highly purified form by bulk-separation from the cerebral and cerebellar cortex of the growing rat. The enzymatic analysis was carried out at the level of the nerve and glial cell lysosomes and mitochondria, two subcellular organelles crucial to the economy of all cells. The findings reveal rather similar developmental patterns for the lysosomal hydrolase N-acetyl-β-D-glucosaminidase in neurons and glial cells of the cerebral cortex as well as in two different cerebellar nerve cell types, the Purkinje and the granule cell. However, significant differences in the post-natal chronology of development of the mitochondrial enzyme α-glycerophosphate dehydrogenase were noted between cortical nerve and glial cells, the glial enzyme exhibiting 6-fold higher levels of activity than the neuronal one throughout the first month of postnatal life. The findings emphasize the feasibility as well as the necessity of studies aimed at the elucidation of the cell-specific aspects of the biochemistry of developing nerve and glial cells.