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PubMed1994

Frontal lobe dysfunction in secondary depression.

Depression is common in patients with neurological disease, particularly with diseases involving the basal ganglia. Although the mechanisms of mood disorders in these patients are poorly understood, selective neural pathways affected directly and indirectly by basal ganglia injury provide a strategy for examining these patients with functional imaging techniques. Studies of regional cerebral glucose metabolism by use of positron-emission tomography are reviewed. These studies demonstrate bilateral hypometabolism of orbital-inferior prefrontal cortex and anterior temporal cortex in depressed subjects, independent of disease etiology. This pattern is similar to that seen in patients with primary unipolar depression. These findings suggest that disruption of paralimbic pathways linking frontal cortex, temporal cortex, and striatum may contribute to both primary depression and depression associated with basal ganglia disease. The findings support the evolving concept of a neuroanatomical locus for mood regulation.

Basal Ganglia↗

PubMed2005

The brain and the biology of obesity.

Obesity has emerged as the dominant American public health problem of the 21st century. Because it stems from consuming more energy than is burned, understanding the role of appetite is central to understanding the causes of obesity. Appetite is fundamentally a biological process, based on a set of neurological signals sent from various organs and tissues to the brain; but it is also influenced by environmental and psychosocial factors. This paper outlines the biology of appetite, focusing on the multitude of hormonal and neural pathways that regulate food intake and lead to accumulation of excess body fat. It also briefly explores the effect of psychosocial and environmental factors on the brain and its signaling system, and how researchers are using this information to help control obesity.

Appetite↗

PubMed1996

Monitoring the integrity of somatosensory pathways with evoked electroencephalographic bursts.

During isoflurane-induced electroencephalographic (EEG) suppression, external stimuli evoke high-amplitude cortical responses (bursts). We tested whether bursts evoked by somatosensory stimuli would reliably distinguish intact somatosensory pathways from pathways in which peripheral nerve conduction had been blocked by local anesthetic. Ten subjects were anesthetized with isoflurane until burst suppression was achieved. During EEG suppression, they were given somatosensory stimulation, consisting of 3-s episodes of 60 electric pulses (20 mA, 0.2 ms), to the tips of the left and right fifth fingers alternately for 10 min. One finger was then anesthetized at the base of the proximal phalanx with prilocaine and the other finger was injected with saline in a double-blind manner. The stimulation was continued for 20 min. In nine patients, the disappearance of bursts in response to stimuli applied to the anesthetized finger clearly indicated the side of the conduction block. After the injection of local anesthetic, there was a predominance of offset bursts over onset bursts in response to stimuli applied to the anesthetized finger (P < 0.05) before the responses disappeared. We conclude that evoked bursts merit further investigation for potential use in monitoring the integrity of neural pathways.

Anesthesia, Inhalation↗

PubMed2006

The proximal neurovascular plate and the tri-zonal neural architecture around the prostate gland: importance in the athermal robotic technique of nerve-sparing prostatectomy.

OBJECTIVE: To review the neural architecture around the prostate gland, as it is relevant for nerve-sparing robotic prostatectomy, including in particular the anatomy of the proximal neurovascular tissue, the neurovascular bundle (NVB), and accessory neural pathways (ANPs). MATERIALS AND METHODS: The aims of this study were achieved in collaboration between the Cornell Institute of Robotic Surgery, New York, NY, USA and the Institute of Urology at the University of Innsbruck, Austria. The broad steps were: (i) anatomical studies of 10 fresh and two fixed male cadavers; and (ii) collection of videotape and still image data from 200 men undergoing radical prostatectomy by the athermal robotic technique at the Cornell Institute. RESULTS: From a surgical standpoint there was a tri-zonal neural architecture including the proximal neurovascular plate (PNP), the predominant NVB (PNB) and ANPs. The PNP was a mean (range) of 5 (3-10) mm lateral to the seminal vesicles, was 3 (2-7) mm thick, 7 (5-25) mm wide and 9 (4-30) mm long. It was within 6 (4-15) mm of the bladder neck, 5 (2-7) mm of the endopelvic fascia and overlapped 5 (0-7) mm of the proximal prostate. The PNB varied in shape and size from the proximal to distal end, was thickest at the base and most variable near the apex. In eight of 12 cases, there was a medial extension behind the prostate, which converged medially at the apex in four cases. ANPs were noted within the layers of levator fascia and/or lateral pelvic fascia on the anterolateral aspect in five cases and in three on the posterior aspect of the prostate. In nine cadavers, the proximal third of the prostate was covered by the PNP where these ANPs were most prominent. The ANPs formed a plexus on the posterolateral aspect of the apex in four cases. CONCLUSION: We have created an anatomical map of neurovascular tissue relevant to robotic prostatectomy. A tri-zonal neural architecture is described which has helped in standardizing the steps of robotic prostatectomy.

Adult↗

PubMed2005

Social circuits: peptidergic regulation of mammalian social behavior.

Mammals have developed patterns of social relationships that enhance the survival of individuals and maximize the reproductive success of species. Although social stimuli and social responses are highly complex, recent studies are providing substantial insights into their neural substrates. Neural pathways employing the nonapeptides vasopressin and oxytocin play a particularly prominent role both in social recognition and the expression of appropriate social responses. New insights into social neuroscience are discussed, along with the relevance of this rapidly developing field to human relationships and disease processes.

Animals↗

PubMed2003

Early-onset anorexia nervosa: is there evidence of limbic system imbalance?

OBJECTIVE: This study, part of a continuing effort to understand the pathophysiology of the brain in early-onset anorexia nervosa, attempts to validate findings from an earlier study of regional cerebral blood flow and to correlate any abnormalities in blood flow with eating disorder psychopathology. METHOD: Fifteen newly referred children and adolescents with a diagnosis of anorexia nervosa (AN) underwent regional cerebral blood flow (rCBF) examination using single-photon computerized tomography (SPECT) and the Eating Disorders Examination (EDE) for children. RESULTS: Mean age was 14 years 11 months (SD = 1.35). Mean weight for height ratio was 82.79 % (SD = 10.66). SPECT findings showed that 11 (73%) had asymmetry (hypoperfusion) of blood flow in at least one area. Regions of the brain showing hypoperfusion included the temporal lobe (n = 9), parietal lobe (n = 5), frontal lobe (n = 3), thalamus (n = 3), and the caudate nuclei (n = 1). The median EDE subscale scores were high for all four subscales. Those patients with hypoperfusion had higher median EDE subscale scores than those without hypoperfusion, although the differences were not statistically significant. CONCLUSIONS: Most patients in our study had abnormal rCBF, predominantly affecting the temporal lobe, confirming our previous findings. There was no association with the EDE scores. The findings support earlier suggestions of an imbalance in neural pathways or circuits, possibly within the limbic system. This hypothesis is considered within the context of current knowledge and suggestions made with regard to how it might be tested.

Adolescent↗

PubMed1985

The effects of paraventricular hypothalamic lesions on maternal behavior in rats.

The present study was undertaken to determine whether the disruptive effects of knife cuts which sever the lateral connections of the medial preoptic area (MPOA) on maternal behavior are mediated by interfering with the output of the paraventricular hypothalamic nucleus (PVN). Postpartum rats received one of the following: Knife cuts severing the lateral connections of the MPOA; knife cuts severing the lateral connections of the PVN; radiofrequency lesions of the PVN; sham lesions or knife cuts. Only females that received knife cuts severing the lateral connections of the MPOA showed severe deficits in maternal behavior. These results indicate that the influence of the MPOA on maternal behavior is not mediated by the output of the PVN. Since the PVN is the major source of oxytocin input to other brain regions, these results also suggest that oxytocinergic neural pathways are not critical for postpartum maternal behavior. Another important finding was that females with MPOA knife cuts that did not retrieve their young were capable of hoarding candy, suggesting that the retrieval deficit was not the result of a general oral motor deficit.

Animals↗

PubMed1999

Sensing of cadmium and copper ions by externally exposed ADL, ASE, and ASH neurons elicits avoidance response in Caenorhabditis elegans.

We developed a quantitative assay for Caenorhabditis elegans avoidance behavior. This was then used to demonstrate that the worm moved away from toxic concentrations of Cd2+ and Cu2+, but not Ni2+, all ions that prevented development from larval to adult stages. Mutants that have structural defects in ciliated neurons (che-2 and osm-3) as well as worms with three laser-operated neurons (ADL, ASE, and ASH), showed no avoidance behavior from Cd2+ and Cu2+. These results suggest that the avoidance from Cd2+ and Cu2+ are mediated through multiple neural pathways including ADL, ASE, and ASH neurons. We hypothesize that the three sensing neurons provide increased accuracy of the sensory response and a survival advantage in the natural environment of the worm.

Animals↗

PubMed2002

The rostral raphe pallidus nucleus mediates pyrogenic transmission from the preoptic area.

Fever is the widely known hallmark of disease and is induced by the action of the nervous system. It is generally accepted that prostaglandin (PG) E(2) is produced in response to immune signals and then acts on the preoptic area (POA), which triggers the stimulation of the sympathetic system, resulting in the production of fever. Actually, the EP3 subtype of PGE receptor, which is essential for the induction of fever, is known to be localized in POA neurons. However, the neural pathway mediating the pyrogenic transmission from the POA to the sympathetic system remains unknown. To identify the neuronal groups involved in the fever-inducing pathway, we first investigated Fos expression in medullary regions of rats after central administrations of PGE(2). PGE(2) application to the lateral ventricle or directly to the POA strikingly increased the number of Fos-positive neurons in the rostral part of the raphe pallidus nucleus (rRPa). Most of these neurons did not exhibit serotonin immunoreactivity. Microinjection of muscimol, a GABA(A) receptor agonist, into the rRPa blocked fever and thermogenesis in brown adipose tissue induced by intra-POA as well as by intracerebroventricular PGE(2) applications. Furthermore, neural tract tracing studies revealed a direct projection from EP3 receptor-expressing POA neurons to the rRPa. Our results demonstrate that the rRPa, which has never been associated with the fever mechanism, mediates the pyrogenic neurotransmission from the POA to the peripheral sympathetic effectors contributing to fever development.

Adipose Tissue, Brown↗

PubMed1993

Projections of nerve cells from the duodenum to the sphincter of Oddi and gallbladder of the Australian possum.

BACKGROUND: This study investigated the existence of direct neural connections between the duodenum and the biliary tract in the Australian possum. METHODS: Retrogradely transported neuronal dyes, Fast Blue and Dil, were injected into the wall of the gallbladder and the sphincter of Oddi. The duodenum, biliary tract, and sympathetic and sensory ganglia were examined for the presence of labeled cell bodies. RESULTS: Two to 3 weeks after gallbladder injection, labeled nerve cell bodies were found in the myenteric plexus of the proximal duodenum but were rare in the duodenum distal to the sphincter of Oddi. No neurons were found in the submucous plexus. Labeled nerve cells were also found in the sphincter of Oddi. After injection of the sphincter, labeled neurons were in both the submucous and myenteric plexuses of the duodenum, on either side. Approximately one third of labeled myenteric neurons were immunoreactive for enkephalin. Labeled cell bodies were also in the coeliaco-mesenteric, nodose, and dorsal root ganglia after both gallbladder and sphincter injection. After a myotomy on the proximal duodenum, no neurons were labeled on the pyloric side of the lesion by subsequent sphincter injection of dye. CONCLUSIONS: Direct neural pathways connect the duodenum with the gallbladder and the sphincter of Oddi, and the sphincter with the gallbladder; this implies that enteric nerve circuits participate in coordinating duodenal and biliary functions.

Animals↗

PubMed2006

[Mechanisms by which acute orofacial pain becomes chronic].

Pain is a complex, multidimensional experience encompassing sensory-discriminative, cognitive, emotional and motivational dimensions. These dimensions in the orofacial region have particular expression since the face and mouth have special biological, emotional and psychological meaning to each individual. Orofacial pain is frequent. Epidemiological studies reveal a high prevalence of severe pain in syndromes such as temporomandibular disorders (TMD), burning mouth syndrome and toothaches, as well as an important role of psychosocial influences, contributing to the persistence of these syndromes. Many of the difficulties experienced by clinicians with the diagnosis and management of acute and chronic orofacial pain stem from a lack of recognition and understanding of these complex conditions, the various intricate bio-psycho-social interactions and the neurobiology behind the chronicisation of acute pain. This text strives to review the important advances and insights into the peripheral processes by which noxious stimuli activates or modulates nociceptive afferent input into the brainstem, the neural pathways in the brainstem and higher levels of the trigeminal (V) somatosensory system and the mechanisms involved in the plasticity of nociceptive transmission. We shall link this knowledge to clinical correlates and suggest a therapeutic approach in acute orofacial pain, in the attempt to avoid the development of chronic pain.

Acute Disease↗

PubMed2002

A study of micturition inducing sites in the periaqueductal gray of the mesencephalon.

PURPOSE: The mesencephalon, especially the periaqueductal gray, is believed to integrate specific movement patterns of the somatic and autonomic nervous system, including those of vocalization, defensive behaviors and others. Fiber communications exist between the periaqueductal gray and the pontine micturition center, and many nerve fibers ascending from the sacral spinal cord project to the periaqueductal gray. We examined whether the mesencephalon is involved in micturition function using microstimulation and a neurotracer. MATERIALS AND METHODS: We decerebrated 28 adult cats under general anesthesia. An electrode that can be used for microinjection was positioned in stereotaxic fashion in the mesencephalon and pons. Subsequently electrical stimulation and chemical stimulation with DL-homocysteine acid were applied to search for micturition inducing sites. Blood pressure and respiration were monitored simultaneously. We also performed electrical microstimulation of pontine micturition center. The neurotracer 5% Fluoro-Gold (Denver, Colorado) was injected into these sites to identify neural pathways between the mesencephalon and pons. The brainstem was removed after 10 hours and the mesencephalon was examined by fluorescence microscopy. RESULTS: Bladder contraction was provoked by electrical and chemical stimulation applied mainly at the ventrolateral side of the periaqueductal gray. Blood pressure increased simultaneously with bladder contraction after periaqueductal gray stimulation. Neurotracer injected into the pontine micturition center was found mainly on the ventrolateral side of the periaqueductal gray, in agreement with the sites where micturition was provoked by microstimulation. CONCLUSIONS: Nerve cells on the ventrolateral side of the periaqueductal gray have neural communications with the pontine micturition center bilaterally and they regulate micturition.

Animals↗

PubMed2001

The neural mechanisms of oral and facial pain.

Pain is a complex and variable phenomenon that can be influenced by many factors. The neural pathways serving pain are not passive conduits, but are part of a dynamic system which can result in different levels of pain resulting from similar injuries under different circumstances. The passage of signals in these pathways may be inhibited or enhanced at almost any level, from the peripheral sensory receptors to the higher centres of the brain. This review will describe recent developments in our understanding of these mechanisms and how this knowledge may be used in controlling pain.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

Neurohormonal control of exocrine pancreas.

The exocrine pancreas is regulated by various hormonal factors derived from the gut through hormone-hormonal and neurohormonal interactions. Physiologic stimuli entering the upper small intestine elicit the release of intestinal hormones and activate sensory reflex mechanisms from the intestinal mucosa to stimulate or inhibit exocrine pancreatic secretion. In addition, the endocrine pancreas, intrapancreatic nerves, and some extrapancreatic neural pathways, with or without mediation by the vagus nerve, are known to participate in regulation of exocrine pancreatic secretion. It has been established that two key intestinal hormones, secretin and cholecystokinin (CCK), in physiologic doses, act through the vagal afferent pathway and interact with each other as well as with other gut hormones. The releases of these two hormones are mediated through the corresponding releasing peptides. In the past few years, the roles of secretin- and CCK-releasing peptides have become more clearly defined. The participation of several neurotransmitters and regulatory peptides in the regulation of exocrine pancreatic secretion has also been established. In addition, neurotransmitters and neuropeptides released from the central nervous system may participate in the regulation of pancreatic secretion. It is conceivable that a few neurotransmitters and neuropeptides are involved in each neural regulatory pathway. However, their roles and sites of action in each pathway remain to be determined.

Journal Article↗

PubMed1981

Central nervous system lesions: sprouting and unmasking in rehabilitation.

Recovery of function following a central nervous system lesion can continue for months or years following the injury. Considerable experimental evidence supports the conclusion that the plasticity of the brain is of importance to the functional recovery. A number of neural mechanisms may be involved in the functional recovery. Two of the mechanisms of neuroplasticity considered particularly likely to play a role, are the following: 1) Collateral sprouting from intact cells to a denervated region after some or all of its normal input has been destroyed, and 2) The unmasking of neural pathways and synapses which are not normally used for the particular function under study but which can be called upon when the ordinarily of dominant system fails. The process of unmasking is extensively discussed in the context of the role of rehabilitation in obtaining maximum recovery of function.

Age Factors↗

PubMed1996

Selective magnocellular damage in melanoma-associated retinopathy: comparison with congenital stationary nightblindness.

Psychophysical methods for isolating and evaluating the function of specific neural pathways are used to characterize the visual losses in patients with melanoma-associated retinopathy (MAR). These are compared with those of congenital stationary nightblindness (CSNB), a condition which displays a similar grossly abnormal ERG and loss of rod function. In MAR patients achromatic contrast sensitivity was greatly reduced in the low spatial frequency range. Stimuli chosen to isolate the magnocellular pathway were seen badly, whereas stimuli signalled primarily by the midget of the parvocellular pathway (isoluminant red/green or achromatic high spatial frequencies) were seen normally. This selective loss was not found in patients with CSNB. In MAR there is a selective loss of function subserved by magnocellular cells coupled with preservation of function subserved by the midget type 1 parvocellular cells.

Adult↗

PubMed2000

A mathematical analysis of the characteristics of the system connecting the cerebellar ventral paraflocculus and extraoculomotor nucleus of alert monkeys during upward ocular following responses.

Movements of the visual scene evoke short-latency ocular-following-responses (OFR). Many studies suggest that a neural pathway containing the cerebellar-ventral-paraflocculus (VPFL) mediates OFR. The relationship between eye movement and simple-spike firing in the VPFL during OFR has been studied in detail using an inverse dynamics approach. The relationship between eye movement and cell firing in the extraoculomotor nucleus (MN) has already been reported. However, no studies have examined the information transformation that occurs between the VPFL and the MN during OFR. In this paper, using an inverse dynamics approach, we derive a transfer function that represents the characteristics of the structure connecting the VPFL and the MN during upward OFR. This structure appears to contain a kind of neural integrator, which constructs eye-velocity-and-position information from eye-acceleration-and-velocity information. We propose a diagram for the neural integration commonly at work during all types of upward eye movement. This is a closed-loop circuit containing a low-pass filter. The low-pass filter can construct eye-velocity-and-position information from an eye-acceleration-velocity-position command similar to the final motor command used commonly for all upward eye movements. Anatomical and electrophysiological data suggest that the vestibular nuclei-interstitial nucleus of Cajal-vestibular nuclei loop might perform such neural integration.

Action Potentials↗

PubMed2002

Amygdala input promotes spread of excitatory neural activity from perirhinal cortex to the entorhinal-hippocampal circuit.

A number of sensory modalities most likely converge in the rat perirhinal cortex. The perirhinal cortex also interconnects with the amygdala, which plays an important role in various motivational and emotional behaviors. The neural pathway from the perirhinal cortex to the entorhinal cortex is considered one of the main paths into the entorhinal-hippocampal network, which has a crucial role in memory processes. To investigate the potential associative function of the perirhinal cortex with respect to sensory and motivational stimuli and the influence of the association on the perirhinal-entorhinal-hippocampal neurocircuit, we prepared rat brain slices including the perirhinal cortex, entorhinal cortex, hippocampal formation, and amygdala. We used an optical imaging technique with a voltage-sensitive dye to analyze 1) the spatial and functional distribution of inputs from the lateral nucleus of the amygdala to the perirhinal cortex; 2) the spread of neural activity in the perirhinal cortex after layers II/III stimulation, which mimics sensory input to the perirhinal cortex; and 3) the effect of associative inputs to the perirhinal cortex from both the lateral amygdaloid nucleus and layers II/III of the perirhinal cortex on the perirhinal-entorhinal-hippocampal neurocircuit. Following stimulation in the superficial layers of the perirhinal cortex, electrical activity only propagated into the entorhinal cortex when sufficient activation occurred in the deep layers of perirhinal area 35. We observed that single stimulation of either the perirhinal cortex or amygdala did not result in sufficient neural activation of the deep layers of areas 35 to provoke activity propagation into the entorhinal cortex. However, the deep layers of area 35 were depolarized much more strongly when the two stimuli were applied simultaneously, resulting in spreading activation in the entorhinal cortex. Our observations suggest that a functional neural basis for the association of higher-order sensory inputs and emotion-related inputs exists in the perirhinal cortex and that transfer of sensory information to the entorhinal-hippocampal circuitry might be affected by the association of that information with incoming information from the amygdala.

Amygdala↗