Comparison of behaviors elicited by electrical brain stimulation in dorsal brain stem and hypothalamus of rats.

Four brain-stimulation phenomena elicited from both dorsal brain stem and hypothalamic sites were investigated with the following results: (a) intracranial self-stimulation rate-intensity functions for dorsal brain stem and hypothalamic sites yielded very high (over 1,000 responses/15 min.) to moderate (201-500 responses/15 min.) response rates; (b) d-amphetamine produced higher response rates than either l-amphetamine or saline at both dorsal brain stem and hypothalamic sites, indicating that noradrenergic dorsal brain stem fibers (or cell bodies) support intracranial self-stimulation; (c) dorsal brain stem and hypothalamic self-stimulation sites reliably produced escape behavior; (d) simultaneous stimulation of dorsal brain stem and hypothalamic sites at subthreshold intensities interacted to produce suprathreshold response rates.     

Problems in the topographic diagnosis of bilateral abducens pareses

It is not possible to exactly differentiate bilateral abducent paralysis case topographically into those arising peripherally and those from the brain stem by means of clinical data. The application of electrophysiological methods, especially the acoustically evoked brain stem potentials and the oculo-auricular phenomena, greatly increases the accuracy of topographical diagnosis. If the oculo-auricular reaction can be triggered in the normal way, a lesion of the brain stem may be practically excluded, whereas changed acoustically evoked potentials at an early point may indicate a disturbance of function in the core region of the 6th cranial nerve.     

脑内移植发展的回顾和展望

脑内移植是神经系统疾病的一种新的治疗措施。它适应临床实践的需要而产生,历经脑内组织移植和脑内干细胞移植两个重要发展阶段,其中脑内干细胞移植的研究主要有神经干细胞移植、胚胎干细胞移植、骨髓和脐血间充质干细胞移植。脑内干细胞移植是目前国内外医学研究的热点,具有广阔的临床应用前景,但也存在许多有待解决的问题,还需要经过一个艰难曲折的探索过程,最终使之成为治疗神经系统疾病的有效方法。它的产生和发展遵循着认识论和辩证法的客观规律,体现了科学认识的实践性、深刻性和创造性。     

Brain stem evoked response suppression during speech production

Auditory brain stem evoked responses (BSERs) to repetitive clicks were recorded in subjects engaged in overt speech, whispering, silent articulation, and covert verbal rehearsal tasks and during a control condition of attending to the clicks. Overt speech and whispering resulted in a significant amplitude reduction of the fifth peak of BSERs without affecting the amplitudes or the latencies of the earlier peaks. These data strongly suggest efferent inhibition of irrelevant auditory input at the level of the upper brain stem.     

Sleep and dream suppression following a lateral medullary infarct: a first-person account

Consciousness can be studied only if subjective experience is documented and quantified, yet first-person accounts of the effects of brain injury on conscious experience are as rare as they are potentially useful. This report documents the alterations in waking, sleeping, and dreaming caused by a lateral medullary infarct. Total insomnia and the initial suppression of dreaming was followed by the gradual recovery of both functions. A visual hallucinosis during waking that was associated with the initial period of sleep and dream suppression is described in detail. Since the changes in sleep and their recovery are comparable to results of animal experiments, it can be concluded that damage to the medullary brain stem causes extreme but short-lived alterations in conscious state and that substantial recovery occurs even though the damage to the brain stem endures.     

Neuropsychological findings of extrapontine myelinolysis without central pontine myelinolysis

Central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM) are well recognized syndromes related to the rapid correction of hyponatremia, which are reported to show brain stem signs and various movement disorders. Cognitive dysfunction and neuropsychological findings, however, have seldom been reported. Cognitive manifestations in osmotic myelinolysis may have been underestimated due to the prominent brain stem symptoms and movement disorders. We report a case of EPM without CPM and describe the neuropsychological findings of EPM. The absence of CPM in this case made it possible to test neuropsychological function in the acute stage. Neuropsychological testing showed severe impairment of attention, verbal and visual memory, visuospatial function, and frontal/executive function. Language and language-related functions were normal except naming.     

Role of monoamines in the control by hormones of sexual receptivity in the female rat.

The involvement of indole- and catecholamines in the hormonal regulation of sexual receptivity has been investigated in ovariectomized female rats. Drugs that reduce 5-hydroxytryptamine, dopamine, and adrenaline or increase noradrenaline neurotransmission tended to facilitate the occurrence of estrous behavior in estrogen-treated females, and drugs having opposite effects tended to inhibit receptivity induced by estrogen and progesterone. Estrogen decreased noradrenaline turnover in cortex and brain stem; progesterone enhanced this effect in brain stem but prevented it in cortex. Both hormones tended to block noradrenaline uptake in hypothalamus in vitro. In a schedule used to induce receptivity, estrogen accelerated serotonin turnover, an effect prevented by progesterone. Thus a number of monoamines may be involved in the control by hormones of estrous behavior. Furthermore, hormones affect both amine turnover and uptake mechanisms.     

Changes in plasma corticosterone and cerebral biogenic amines and their catabolites during training and testing of mice in passive avoidance behavior

Concentrations of cerebral biogenic amines and their catabolites, and of plasma corticosterone were determined 10 min after training and testing of passive avoidance behavior in mice. Training and testing of mice that had acquired the task well resulted in statistically significant increases of plasma corticosterone, of the DOPAC:DA ratio [an index of dopamine (DA) metabolism] in prefrontal cortex, and of MHPG:NE ratios [an index of norepinephrine (NE) metabolism] in hypothalamus and brain stem. There were also decreases of NE in hypothalamus and brain stem, and an increase of 5-HIAA:5-HT [an index of serotonin (5-HT) metabolism] and of tryptophan in brain stem. Some of these changes also occurred in mice merely exposed to the apparatus but not trained. Plasma corticosterone concentrations were significantly higher in mice that performed the task well compared to those that did not, and there were significant correlations between this measure and the avoidance performance. Although there was only one statistically significant correlation between a cerebral metabolite and the avoidance performance (a decrease in hypothalamic NE), there were indications of relationships between cerebral biogenic amine metabolism and the performance. The patterns of neurochemical and endocrine changes closely resemble those previously observed in response to various stressors. Thus, the changes could reflect stress responses, which may or may not be related directly to the performance of the avoidance task.     

Stem allomorphy in the Spanish mental lexicon: evidence from behavioral and ERP experiments

This study presents results from a nonce-word elicited production task and a reading experiment using event-related brain potentials (ERPs) investigating finite forms of Spanish verbs which consist of marked stems and regular person and number agreement suffixes. The first experiment showed that unmarked stems are productively extended to nonce words, whereas marked stems generalize more restrictively to nonce words, based on lexical similarity to existing stem forms. The second experiment yielded a lexical ERP signature for stem violations and an ERP pattern signaling morpho-syntactic (rule-based) processing for suffix violations. We argue that stem allomorphy is lexically represented in the Spanish mental lexicon, with marked stems forming subnodes of structured lexical entries.     

Septal influences on operant responding in the rat.

The afferent and efferent connections of the septum with the hippocampus (fornix) of with the hypothalamus and lower brain stem (medial forebrain bundle) were transected by means of an encephalotome near the point where these pathways enter or leave the septal area. A transection of the fornix that produced minimal direct damage to cellular components of the septum of hippocampus reproduced the effects of large septal lesions on responding in several temporally defined paradigms that involve periods of response suppression (differential reinforcement of low rates, discriminated Sidman avoidance, fixed interval). Transection of the medial forebrain bundle fibers that interconnect the septum with the hypothalamus and lower brain stem did not affect behavior in any of these paradigms. These observations should be veiwed in the context of the results of earlier investigations which demonstrated that transection of the medial forebrain bundle reproduces several other components of the septal lesion syndrome.     

Tyrosine hydroxylase activities in the brains of wild Norway rats and silver foxes selected for reduced aggressiveness towards humans

Tyrosine hydroxylase (TH) activity was measured in brains from Norway rats and silver foxes showing wild type aggressiveness and from their counterparts selected over 20-25 generations for reduced aggressiveness towards humans (tameness). TH activity in the brain stem and cortex was increased in tame animals of both species compared with aggressive counterparts. Selection increased hypothalamic TH activity in foxes, but decreased it in rats. There was no difference in TH activity in corpus striatum between the tame and aggressive animals. Fetal TH activity in the posterior part of the brain was higher in tame than aggressive rats at day 20 of embryogensis. Increased TH activity in the brain stem and cortex of adult aggressive rats was observed after treatment of their mothers with hydrocortisone on the days 16 and 18 of pregnancy. This elevation in TH activity was associated with attenuation of the defense behavior of aggressive rats. The data suggested that alterations in neural TH activity in tame rats and foxes may be part of the neurochemical basis of their behavioral phenotype which is developed by selection. © 1994 Wiley-Liss, Inc.     

Personal identity and brain death: a critical response

The authors contend that there are logical inconsistencies in a theory put forth by Michael Green and Daniel Wikler ("Brain death and personal identity," Philosophy and Public Affairs 1980 Winter; 9(2): 105-133) to justify the brain death concept of death. Green and Wikler had asserted that individuals cease to exist and are dead when the criteria for continuity in their personal identity are not met. Having argued that the theory of personal identity is misguided, Agich and Jones suggest that further research into the ontological foundation of brain death concepts should begin, not by rejecting medical or moral considerations, but by carefully defining the main competing concepts of brain death as brain stem death, cerebral death, death of the brain as a whole, and whole brain death, and then by relating these concepts to the ontological conditions for being a live individual or person.     

An object-oriented simulation of anorexia based on brain structure interaction

A computer simulation using an object-oriented strategy was developed to model brain mechanisms that underlie eating disorders. The simulation was based on neuroanatomical and neurochemical evidence from published literature. Testing of the simulation required that the activity levels of the raphe nuclei of the brain stem be altered and the resulting activity levels of associated brain structures be compared with results from human and animal data. The results supported the serotonin hypothesis of anorexia that increasing the activity level of the raphe nuclei would result in dramatic changes in the activity level of the paraventricular nucleus. The findings are discussed with respect to the feasibility of computer simulations to test theories of brain-based disorders.     

Developing human-nonhuman chimeras in human stem cell research: ethical issues and boundaries

The transplantation of adult human neural stem cells into prenatal non-humans offers an avenue for studying human neural cell development without direct use of human embryos. However, such experiments raise significant ethical concerns about mixing human and nonhuman materials in ways that could result in the development of human-nonhuman chimeras. This paper examines four arguments against such research, the moral taboo, species integrity, "unnaturalness," and human dignity arguments, and finds the last plausible. It argues that the transfer of human brain or retinal stem cells to nonhuman embryos would not result in the development of human-nonhuman chimeras that denigrate human dignity, provided such stem cells are dissociated. The article provides guidelines that set ethical boundaries for conducting such research that are consonant with the requirements of human dignity.     

The anencephalic as organ donor: Whose baby is it anyway?

Should an anencephalic newborn, lacking cerebral hemispheres but possessing a functional brain stem, be eligible for organ donation? The dialectical method is used here to envision how a protagonist and an antagonist might debate the ethics of the issue.     

Changes of visual fields in intracranial tumors outside the cerebral hemispheres]

Based on neurosurgical material of 1,746 brain tumours, the changes of the visual field determined by isopteric perimetry are discussed with their significe with regard to tumours of corpus callosum, lateral ventricles, brain stem ganglia, IIIrd ventricle, region of the sella and adjacent areas as well as posterior fossa. The proportion of unilateral blindness with primary opticus atrophy and of skotomas is strinkingly high, so that in cases of loss of vision, not readily explicable by ophthalmology, as well as in unilateral defects of the visual field, intracranial processes must be thought of.     

State dependent modification of auditory brain stem potentials

It is well known, amplitudes and latencies of auditory brain stem potentials are almost independent of viligance state. Contrary to that, simple cognitive requirements effect amplitude changes (enhancement of variance, amplitude reduction) in a part 2/3) of the subjects.     

The square search test in connection with acoustic evoked brain stem potentials

A random sample of 15 patients suffering from multiple sclerosis without acute episodes and at least partially able to work, shows to a high degree of statistical certainty that reduction in amplitude of acoustically evoked brain stem potentials (BAEP) is closely linked with beta-weighted performance value of the square search test (QSP).     

Facial myokomias in brain stem tumors]

Four cases of brain-stem tumor were described, in which myokymias were electromyographically derived from the region of several cerebral nerves. An attempt is made to interpret the effects of twitching by reference to the electromyogram. Myokymias are a positive indication of organic brain stem damage. The use subtle techniques of electromyographic examination shows that this muscular hyperkinesis is not so infrequent a symptom as is generally believed.     

The tortuous route from genes to behavior: A neuroconstructivist approach

In their excitement at using the human genome project to uncover the functions of specific genes, researchers have often ignored one fundamental factor: the gradual process of ontogenetic development. The view that there might be a gene for spatial cognition or language has emanated from a focus on the structure of the adult brain in neuropsychological patients whose brains were fully and normally developed until their brain insult. The developing brain is very different. It starts out highly interconnected across regions and is neither localized nor specialized at birth, allowing interaction with the environment to play an important role in gene expression and the ultimate cognitive phenotype. This article takes a neuro constructivist perspective, arguing that domain-specific end states can stem from more domain-general start states, that associations may turn out to be as informative as dissociations, and that genetic mutations that alter the trajectory of ontogenetic development can inform nature/nurture debates.