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C C Bell

Publications and source records attributed to C C Bell.

At least 37 records · Page 2Linked to original sources
PubMed1998

The mormyrid electrosensory lobe in vitro: physiology and pharmacology of cells and circuits.

This paper is concerned with the electrosensory lobe (ELL) of mormyrid electric fish as examined in in vitro slices. Intracellular recordings from morphologically identified cells and field potential recordings were used to characterize the physiology and pharmacology of ELL cells. Most intracellular recordings were from the Purkinje-like interneurons that are known as medium ganglion cells and from the two types of efferent neurons, large ganglion and large fusiform cells. Stimulation of primary afferent fibers elicits both excitatory and inhibitory effects in these cells, with the excitatory effects being mediated by both the AMPA and NMDA types of glutamate receptors and the inhibitory effects being mediated by both GABAA and glycine receptors. Parallel-fiber stimulation evokes an EPSP-IPSP sequence, with the EPSPs being mediated by both AMPA and NMDA receptors and the IPSPs being mediated by GABAA receptors only. The parallel fiber-evoked EPSPs and IPSPs show marked paired-pulse facilitation. A large and unusually broad spike is recorded inside medium ganglion cells, and field potential responses suggest that this spike is propagated into the apical dendrites. The results provide essential information for understanding how peripheral and central inputs are integrated in ELL.

Animals↗
PubMed1998

Adolescent suicide.

This article reviews the origin of youth suicide. Theoretic suicide risk factors and empirically observed suicide risk factors are discussed along with proposed resiliency factors that prevent suicide. Finally, suicide prevention and intervention strategies are covered, and a call for better studies on suicide prevention is heralded.

Adolescent↗
PubMed1998

The electric image in weakly electric fish: physical images of resistive objects in Gnathonemus petersii.

The present study describes a measurement-based model of electric image generation in the weakly electric mormyrid fish Gnathonemus petersii. Measurements of skin impedance, internal resistivity and fish body dimensions have been used to generate an electrical-equivalent model of the fish and to calculate electrical images and equivalent dipole sources for elementary resistive objects. These calculations allow us to understand how exafferent and reafferent signals are sensed by electroreceptors. An object's electric image consists of the modulation of the transcutaneous voltage profile generated by the fish's own discharge. The results suggest a set of rules for electrolocation: (1) the side of the fish where modulation is larger indicates the side on which the object is situated; (2) the object's position in the electroreceptive field is indicated by the point of maximum modulation of the transcutaneous voltage; (3) the degree of focus of the image indicates the distance to the object. In addition, center-surround opposition originating at pre-receptor level is proposed. Both experimental measurements and modeling indicate that fish skin impedance is relatively low (400-11 000 cm 2 ) and mainly resistive. This low skin impedance appears to enhance the local electric organ discharge modulation, the center-surround effect, the signal-to-noise ratio for electrolocation and the active space for electrocommunication.

Animals↗
PubMed1998

Using sports to strengthen resiliency in children. Training heart.

This article describes how sports can cultivate resiliency. Encouraging the development of heart in youth is highlighted. The concept is a simple one. By encouraging children and adolescents to go the extra mile in a sports context, youth practice calling up emotional reserves until they trust that they have a stockpile of conviction. The authors believe building heart in youth is a preventive public health strategy that can inoculate against the potentially negative effects of stress and trauma. It is hoped that heart will become an essential tool in the primary prevention of stress-related disorders in youth and a critical skill that promotes having an optimal life. In addition, the authors believe that heart can be developed after exposure to traumatic stress. Heart is critical to overcoming the sense of devastation and helplessness that develops from traumatic experiences.

Adaptation, Psychological↗
PubMed1997

Physiology and plasticity of morphologically identified cells in the mormyrid electrosensory lobe.

The electrosensory lobe (ELL) of mormyrid electric fish is the first stage in the central processing of sensory input from electroreceptors. The responses of cells in ELL to electrosensory input are strongly affected by corollary discharge signals associated with the motor command that drives the electric organ discharge (EOD). This study used intracellular recording and staining to describe the physiology of three major cell types in the mormyrid ELL: the medium ganglion cell, the large ganglion cell, and the large fusiform cell. The medium ganglion cell is a Purkinje-like interneuron, whereas the large ganglion and large fusiform cells are efferent neurons that convey electrosensory information to higher stages of the system. Clear differences were observed among the three cell types. Medium ganglion cells showed two types of spikes, a small narrow spike and a large broad spike that were probably of axonal and dendro-somatic origin, respectively, whereas the large ganglion and large fusiform cells showed only large narrow spikes. Most of the medium ganglion cells and all of the large ganglion cells were inhibited by electrosensory stimuli in the center of their receptive fields, whereas the large fusiform cells were excited by such stimuli. Responses to the EOD corollary discharge were different in the three cell types, and these responses underwent plastic changes after a few minutes of pairing with an electrosensory stimulus. Plastic changes were also observed in medium and large ganglion cells after the corollary discharge was paired with depolarizing, intracellular current pulses.

Animals↗
PubMed1997

Synaptic plasticity in a cerebellum-like structure depends on temporal order.

Cerebellum-like structures in fish appear to act as adaptive sensory processors, in which learned predictions about sensory input are generated and subtracted from actual sensory input, allowing unpredicted inputs to stand out. Pairing sensory input with centrally originating predictive signals, such as corollary discharge signals linked to motor commands, results in neural responses to the predictive signals alone that are 'negative images' of the previously paired sensory responses. Adding these 'negative images' to actual sensory inputs minimizes the neural response to predictable sensory features. At the cellular level, sensory input is relayed to the basal region of Purkinje-like cells, whereas predictive signals are relayed by parallel fibres to the apical dendrites of the same cells. The generation of negative images could be explained by plasticity at parallel fibre synapses. We show here that such plasticity exists in the electrosensory lobe of mormyrid electric fish and that it has the necessary properties for such a model: it is reversible, anti-hebbian (excitatory postsynaptic potentials (EPSPs) are depressed after pairing with a postsynaptic spike) and tightly dependent on the sequence of pre- and postsynaptic events, with depression occurring only if the postsynaptic spike follows EPSP onset within 60 ms.

Animals↗
PubMed1997

Stress-related disorders in African-American children.

Children exposed to traumatic stress are vulnerable to a variety of stress-related disorders other than classical post-traumatic stress disorder. Several case histories are presented to illustrate some of the diversity of how traumatic stress may manifest in children. African-American children are the main focus of this article as political, economic, social, and morbidity and mortality indicators suggest that African-American children are at high risk for exposure to potentially traumatic stressors. Different presentations of traumatic, stress are discussed in an effort to broaden our understanding of the outcome of traumatic stress to fully help traumatized children.

Adolescent↗
PubMed1997

Promotion of mental health through coaching competitive sports.

Competitive sports can have a negative or positive impact on an athlete's mental health, and an athlete's coach plays a large role in determining this. The coach's goal should be to help athletes realize that developing human potential is equally as important as winning. This article highlights guidelines to assist coaches in instructing and mentoring athletes.

Health Promotion↗
PubMed1997

Community violence: causes, prevention, and intervention.

This article presents some pragmatic schemata for understanding various types and motivations for violence. This understanding is essential to frame prevention, intervention, and postvention strategies designed to reduce the phenomena of violence in our society. Each category of violence lists examples of prevention, intervention, and postvention strategies. This article is intended to broaden the understanding of violence so that strategies to address violence will become more specific and measurable.

Adolescent↗
PubMed1996

Nucleus preeminentialis of mormyrid fish, a center for recurrent electrosensory feedback. I. Electrosensory and corollary discharge responses.

1. The nucleus preeminentialis (PE) is a large central structure that projects both directly and indirectly to the electrosensory lobe (ELL) where the primary afferents from electroreceptors terminate. PE receives electrosensory input directly from ELL and also from higher stages of the electrosensory pathway. PE is thus an important part of a central feedback loop that returns electrosensory information from higher stages of the system to the initial stage in ELL. 2. This study describes the field potentials and single-unit activity that are evoked in PE by electrosensory stimuli and by corollary discharge signals associated with the motor command that drives the electric organ to discharge. All recordings were extracellular in this study. 3. Two types of negative-going corollary discharge-evoked field potentials were found in PE: 1) a shallow, long-lasting negative wave with a latency at the peak of approximately 11 ms, and 2) a more sharply falling and larger negative wave with a shorter latency at the peak of approximately 9 ms. The long-latency wave was predominant in the dorsolateral and posterior parts of PE, whereas the short-latency wave was predominant in the medial and rostral regions. Both waves were only found in PE and thus can serve for its identification. 4. Electrosensory stimuli given either locally to a restricted skin region or symmetrically to the entire body evoked characteristic field potentials in both regions of PE. The mean latency between the stimulus and the peak of the response was 6.9 ms in the early negativity region and 12.2 ms in the late negative region. The responses to such stimuli were strongly facilitated by the electric organ corollary discharge. 5. Field potential responses to the electric organ corollary discharge were markedly plastic. Responses to the corollary discharge plus a paired electrosensory stimulus decreased over time and the response to the corollary discharge alone was markedly enhanced after a period of such pairing. 6. Local electrosensory stimulation of the skin showed that the caudal-rostral body axis is mapped from dorsal-medial to ventral-lateral in PE. The same somatotopy was found in the regions of the early and late negatives. The ventral and dorsal body appeared not to be separately mapped in PE. The areas representing the head and chin appendage ("Schnauzenorgan") are especially large in PE, due presumably to the high density of electroreceptors in these areas. 7. Two main types of units were recorded in PE: 1) inhibitory (I) cells with a corollary discharge response that was inhibited by an electrosensory stimulus to the center of their receptive fields; and 2) excitatory (E) cells with an excitatory response to electrosensory stimuli that was facilitated by the corollary discharge. Some of the E cells responded to the corollary discharge alone and some did not. Most cells appeared to be responding to input from mormyromast electroreceptors, but a few cells were driven by ampullary electroreceptors and a few by Knollenorgan electroreceptors. 8. The corollary discharge effects on I cells and E cells were plastic and depended on previous pairing with a sensory stimulus. The corollary discharge facilitation of E cells and inhibition of I cells decreased during pairing with a sensory stimulus, and the corollary discharge-driven excitation of I cells was much larger after pairing than before. 9. The results provide an initial overview of a major component in the control of electrosensory information processing by recurrent feedback from higher stages of the system.

Animals↗
PubMed1994

Response of emergency rooms to victims of interpersonal violence.

OBJECTIVE: This study explored whether emergency rooms in a metropolitan county had standard procedures or offered services that address the needs of victims of interpersonal violence. METHODS: Fifty hospital emergency rooms (75 percent of the facilities eligible to participate in the survey) responded to a 55-item questionnaire about their handling of victims of interpersonal violence. RESULTS: Emergency rooms generally relied on patient self-reports to determine whether a patient is a victim of violence. Standard operating procedures for reporting cases to state agencies and referrals for additional services were most likely to exist for areas in which hospitals' response is mandated by law, such as sexual assault and child abuse. In addition, three-fourths of the hospitals had procedures for dealing with elder abuse, an area in which reporting is strongly encouraged. Most direct services received by victims were not specifically targeted to them but were services offered to the general emergency room population. The most frequent referrals were to rape advocacy groups and battered women's groups. CONCLUSIONS: The hospitals were most likely to respond to victims in areas in which their actions were mandated by law, such as sexual assault and child abuse, or strongly recommended, such as elder abuse. The majority of emergency rooms do not conduct adequate epidemiological surveillance of injuries resulting from interpersonal violence. Protocols, services, and referrals for victims of family violence, peer violence, and other forms of interpersonal violence should be mandated by law or by standards of treatment.

Adult↗
PubMed1993

Storage of a sensory pattern by anti-Hebbian synaptic plasticity in an electric fish.

Synaptic plasticity occurs in several regions of the vertebrate brain and is believed to mediate the storage of behaviorally significant information during learning. Synaptic plasticity is well demonstrated in most cases, but the behavioral meaning of the relevant neural signals and the behavioral role of the plasticity are uncertain. In this paper we describe a case of synaptic plasticity which involves identifiable sensory and motor signals and which appears to mediate the storage of an image of past sensory input. Corollary discharge signals associated with the motor command that drives the electric organ are prominent in the electrosensory lobe of mormyrid electric fish. Some of these corollary discharge signals elicit a negative image or representation of the electrosensory input pattern that has followed recent motor commands. When the temporal and spatial pattern of sensory input changes, the corollary discharge effect also changes in a corresponding manner. The cellular mechanisms by which the corollary discharge-evoked representation is stored were investigated by intracellular recording from cells of the electrosensory lobe and pairing intracellular current pulses with the corollary discharge signal. The results indicate that the representation of recent sensory input is stored by means of anti-Hebbian plasticity at the synapses between corollary discharge-conveying fibers and cells of the electrosensory lobe. The results also suggest that dendritic spikes and plasticity at inhibitory synapses are involved in the phenomenon.

Animals↗
PubMed1993

Community violence and children on Chicago's southside.

This report summarizes a program of study on African-American children and violence conducted by a comprehensive community mental health center on the southside of Chicago. The research, which looked at exposure to violence, self-reports of aggression, and possible interventions, grew out of: (1) an awareness of the enormous amount of familial and extrafamilial violence in the black community; (2) clinical experiences that indicated that victimization and covictimization (i.e., victimization of close others) were often significant factors in the lives of the mentally ill; (3) a growing uneasiness, and indeed curiosity, over the extent to which children were witnessing these events and the impact of this witnessing, particularly on their own levels of aggression; and (4) a belief that the integrity of the black community was being threatened by the violence and that solutions must be sought.

Black or African American↗