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PubMed1998

Limbic gamma rhythms. I. Phase-locked oscillations in hippocampal CA1 and subiculum.

Gamma oscillations (approximately 40 Hz) were induced in transverse hippocampal slices by tetanic stimulation of CA1 and/or subiculum. Tetanic stimulation of each site elicited population gamma oscillations in the surrounding tissue <400 micro(m) away. Stimulation of CA1 alone could evoke activity at both CA1 and subiculum. Subicular stimulation, however, did not transmit to CA1. When the rostral end of CA1 was stimulated, gamma oscillations transmitted across <1.5 mm of silent CA1 before reappearing in the subiculum. Tetanic stimulation of CA1 increased [K+]o to 8.2 +/- 1.5 mM (mean +/- SE). The location of the peak increase corresponded to the site of local gamma generation. Silent areas of CA1 experienced smaller [K+]o increases, to 4.9 +/- 0.7 mM. The subiculum, which generated gamma, remained at the baseline 3.0 mM. Although fluctuations in [K+]o may have an impact on the generation of gamma rhythms, they are not necessary for them. Gamma oscillations had similar frequencies in CA1 and subiculum (40.4 +/- 2.9 and 43.9 +/- 3.1 Hz, respectively). When present in both, the oscillations typically were phase locked with the subiculum lagging by 5.4 +/- 1.8 ms. When both CA1 and subiculum were stimulated the lag decreased by 28%. These delays approximate those expected for the conduction velocity of axons between the two regions, here estimated at 0.52 +/- 0.07 m/s. Transmission of gamma oscillations from CA1 to subiculum was blocked by the focal addition of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-receptor antagonist, 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione, to the subiculum. Oscillations induced in CA1 by local tetanic stimulation were blocked by focal application of the gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline, to CA1. Focal application of bicuculline to the subiculum blocked gamma due to subicular stimulation but not that due to CA1 stimulation. Bath-applied bicuculline disrupted subicular gamma evoked by subicular stimulation and led to a transient period of epileptiform responses before completely blocking responses. The further addition of the GABAB receptor antagonist, CGP 55845A, reversed this block, restoring the epileptic discharges evoked by tetanic stimulation. This suggests that the subiculum differs from hippocampal CA3 and neocortex, in having a powerful GABAB receptor-dependent mechanism to prevent epileptic discharges. The subiculum generates gamma rhythms both in response to local stimulation and to gamma rhythms evoked in CA1. Subicular gamma differs from that in CA1 in the presence of population spike doublets rather than singlets on many cycles. In both areas, generation of gamma by local stimulation depends on GABAA receptors, suggesting that the subiculum shares the interneuronal network mechanism we proposed for CA1.

Animals↗
PubMed1987

Increased prolactin binding and morphological changes in the wound epithelium of regenerating limbs of Notophthalmus viridescens.

Distribution of prolactin has been examined in regenerating forelimbs from the newt Notophthalmus viridescens. Specific prolactin binding was demonstrated in homogenates of unamputated tissue, and of regenerating limbs at from 3 to 21 days postamputation. Labeled prolactin that was injected intraperitoneally into animals with one regenerating limb accumulated in the most distal portion of the regenerate at 7 and 14 days postamputation. Light-microscopic autoradiography demonstrated that labeled prolactin was localized most heavily in the apical, outer layer of the wound epithelium. Scanning electron microscopy demonstrated that, in addition to changes in prolactin affinity following amputation, morphological changes occurred in the apical wound epithelium as well. Cell surfaces of the stump epidermis were characterized by periodic dispersion of papillae among a network of interconnecting structures 1-2 microns across. By contrast, the surfaces of cells from the area in which labeled prolactin was found to localize most intensely were characterized by lack of papillae and, depending on the stage of regeneration, a pattern of microvilli and microplicae. These morphological alterations appear to reflect functional and biochemical differences between stump epidermis and wound epithelium.

Animals↗
PubMed2004

Combinatorial codes in ventral temporal lobe for object recognition: Haxby (2001) revisited: is there a "face" area?

Haxby et al. [Science 293 (2001) 2425] recently argued that category-related responses in the ventral temporal (VT) lobe during visual object identification were overlapping and distributed in topography. This observation contrasts with prevailing views that object codes are focal and localized to specific areas such as the fusiform and parahippocampal gyri. We provide a critical test of Haxby's hypothesis using a neural network (NN) classifier that can detect more general topographic representations and achieves 83% correct generalization performance on patterns of voxel responses in out-of-sample tests. Using voxel-wise sensitivity analysis we show that substantially the same VT lobe voxels contribute to the classification of all object categories, suggesting the code is combinatorial. Moreover, we found no evidence for local single category representations. The neural network representations of the voxel codes were sensitive to both category and superordinate level features that were only available implicitly in the object categories.

Adult↗
PubMed2006

Microembolic flow disturbances in the cerebral microvasculature with an arcadal network: a numerical simulation.

Flow disturbance due to microembolism in the cerebral microvasculature with an arcadal network was studied by a numerical simulation. A mathematical model for flow in the arcadal network was developed, based on in vivo data of cat cerebral microvasculature and flow velocity. The network model consisted of 45 vessel segments, and 25 branching points. To simulate microvascular responses to blood flow, the following three types of responses to wall shear stress were considered; non-reactive (solid-like), cerebral arteriole, and skeletal muscle arteriole-like responses. The numerical calculation was carried out in the condition where a feeding arteriole was occlused. Flow changes in efferent vessels were evaluated for assessment of blood supply to the local area of cerebral tissue. The present simulation has demonstrated that blood flow in efferent vessels was influenced by the topology of the vascular network and the response pattern in single vessels. The arcadal structure of arterioles might be most effective in response to flow disturbances in efferent vessels.

Animals↗
PubMed2003

Verbal storage in a premotor-parietal network: evidence from fMRI-guided magnetic stimulation.

Phonological rehearsal helps to keep selected information consciously in mind for further processing. This part of short-term storage takes place during the delay period of verbal working memory tasks and involves a frontoparietal network as functional magnetic resonance imaging (fMRI) studies have shown. The involved cortical areas can be further investigated by interfering with the local information processing using transcranial magnetic stimulation (TMS). On a single subject level, we identified predominantly left-sided premotor, prefrontal, and parietal areas active during the delay period of a verbal working memory task using event-related fMRI. In a pilot approach, TMS was neuronavigated to the individually active areas by using a stereotaxic device. Then, TMS was applied during the delay period of similar tasks as in fMRI. Error rates increased significantly upon stimulating left premotor cortex, but not upon parietal or prefrontal stimulation. The contribution of the premotor cortex to storage and rehearsal is discussed as an active top-down storage process within the frontoparietal network.

Adult↗
PubMed2001

Network activity evoked by neocortical stimulation in area 36 of the guinea pig perirhinal cortex.

The perirhinal cortex is a key structure involved in memory consolidation and retrieval. In spite of the extensive anatomical studies that describe the intrinsic and extrinsic associative connections of the perirhinal cortex, the activity generated within such a network has been poorly investigated. We describe here the pattern of synaptic interactions that subtend the responses evoked in area 36 of the perirhinal cortex by neocortical and local stimulation. The experiments were carried out in the in vitro isolated guinea pig brain. The synaptic perirhinal circuit was reconstructed by integrating results obtained during intracellular recordings from layer II-III neurons with simultaneous current source density analysis of laminar profiles performed with 16-channel silicon probes. Both neocortical and local stimulation of area 36 determined a brief monosynaptic excitatory potential in layer II-III neurons, followed by a biphasic synaptic inhibitory potential possibly mediated by a feed-forward inhibitory circuit at sites close to the stimulation electrode and a late excitatory postsynaptic potential (EPSP) that propagated at distance within area 36 along the rhinal sulcus. During a paired-pulse stimulation test, the inhibitory postsynaptic potential (IPSP) and the late EPSP were abolished in the second conditioned response, suggesting that they are generated by poli-synaptic circuits. Current source density analysis of the field responses demonstrated that 1) the monosynaptic activity was generated in layers II-III and 2) the sink associated to the disynaptic responses was localized within the superficial layer of area 36. We conclude that the neocortical input induces a brief monosynaptic excitation in area 36 of the perirhinal cortex, that is curtailed by a prominent inhibition and generates a recurrent excitatory associative response that travels at distance within area 36 itself. The results suggest that the perirhinal cortex network has the potentials to integrate multimodal incoming neocortical information on its way to the hippocampus.

Animals↗
PubMed1999

[The ODEC (Organization for Development and Community Networks) and mental health: from networking to opening in the local community].

The Organisme de développement et d'entraide communautaire (ODEC) is a nonprofit mental health organization that was established in 1987 and offers mutual help and community development services in the Vallée-de-la-Lièvre region in the Outaouais area of Quebec. Starting with an individual accompaniment service for people living with mental health problems, ODEC has succeeded in establishing a significant mutual help network that now involves more than 100 people. This article comes out of an in-depth case study of ODEC. By analysing the major parameters of its journey over more than 10 years, it brings to the fore the impact in the mental health field of providing a network in close association with community involvement.

Community Mental Health Services↗
PubMedDate not supplied

The New Hampshire public health network: creating local public health infrastructure through community-driven partnerships.

In 1997, under the auspices of the Turning Point program, New Hampshire's public health stakeholders convened a strategic planning process to transform the state public health system. What emerged was a fundamental vision that the public health system could only be improved by strengthening the capacity of local communities to address local health issues. A plan was developed to create regional public health structures, in areas with no local health departments, to deliver essential public health services at the local level. Seven years later, that plan has become the New Hampshire Public Health Network. The network now covers 67% of the New Hampshire population and includes 113 (48%) cities and towns. Pre- and postevaluations to assess local public health infrastructure at the inception of the program and following 2 years of funding and technical assistance showed significant improvement in local public health capacity and performance. This article describes the development of local public health structures in New Hampshire where none had previously existed.

Community Health Planning↗
PubMed2006

Temporal shape error concealment by global motion compensation with local refinement.

This paper presents an original temporal shape error concealment technique based on a combination of global and local motion compensation. For this technique, which is especially useful for object-based video applications in error-prone environments (e.g., mobile networks), it is assumed that the shape of the corrupted object at hand is in the form of a binary alpha plane and some of the shape data is missing due to channel errors. To conceal the corrupted shape, the decoder first assumes that a global motion model can describe the shape changes in consecutive time instants. This way, based on locally estimated global motion parameters, the decoder attempts to conceal the corrupted alpha plane by global motion compensating the shape data from the previous time instant. Afterwards, since a global motion model cannot perfectly describe all alpha plane changes, a local motion refinement is applied to improve the concealment in areas of the object with significant local motion.

Algorithms↗
PubMed1996

Neuronal connections of orbital cortex in rats: topography of cortical and thalamic afferents.

The cortical and thalamic afferent connections of rat orbital cortex were investigated using fluorescent retrograde axonal tracers. Each of the four orbital areas has a distinct pattern of connections. Corticocortical connections involving the ventral and ventrolateral orbital areas are more extensive than those of the medial and lateral orbital areas. The medial orbital area has cortical connections with the cingulate, medial agranular (Fr2) and posterior parietal (PPC) cortices. The ventral orbital area has connections with the cingulate area, area Fr2, secondary somatic sensory area Par2, PPC, and visual areas Oc2M and Oc2L. The ventrolateral orbital area (VLO) receives cortical input from insular cortex, area Fr2, somatic sensory areas Par1 and Par2, PPC and Oc2L. The lateral orbital area has cortical connections limited to the agranular and granular insular areas, and Par2. Thalamic afferents to the four orbital fields are also topographically organized, and are focused in the submedial and mediodorsal nuclei. The ventrolateral orbital area receives input from the entirety of the submedial nucleus, whereas the other orbital areas receive input from its periphery only. Each orbital area is connected with a particular segment of the mediodorsal nucleus. The medial orbital area receives its principal thalamic afferents from the parataenial nucleus, the dorsocentral portion of the mediodorsal nucleus, and the ventromedial portion of the submedial nucleus. The ventral orbital area receives input from the lateral segment of the mediodorsal nucleus, the rostromedial portion of the submedial nucleus, and the central lateral nucleus. Thalamic afferents to the ventrolateral orbital area arise from the entirety of the submedial nucleus and from the lateral segment of the mediodorsal nucleus. The lateral orbital area receives thalamic afferents from the central segment of the mediodorsal nucleus, the ventral portion of the submedial nucleus, and the ventromedial nucleus. The paraventricular, ventromedial, rhomboid and reuniens nuclei also provide additional input to the four orbital areas. The connections of the ventrolateral orbital area are interpreted in the context of its role in directed attention and allocentric spatial localization. The present findings provide anatomical support for the view that areas Fr2, PPC and VLO comprise a cortical network mediating such functions.

Animals↗
PubMed2001

Medical mimics. Medical and neurological conditions simulating ADHD.

The medical and neurological conditions that simulate ADHD are reviewed, as well as those disorders frequently presenting as comorbidities with ADHD. The localization of ADHD has invoked multiple areas, including frontal lobes, nondominant parietal lobe, and basal ganglia, and the neural network theory of cortical-subcortical-cortical loops has been implicated in the pathogenesis of ADHD. The medical evaluation of patients presenting with ADHD should be comprehensive, with an emphasis on demonstrating chronic and permeating symptoms since early childhood without a better medical explanation. Associated thyroid disorders are reviewed, including the syndrome of resistance to thyroid hormone. Suggested laboratory studies are provided, depending on the clinical circumstances.

Attention Deficit Disorder with Hyperactivity↗
PubMed2005

Angina on the Palm: randomized controlled pilot trial of Palm PDA software for referrals for cardiac testing.

OBJECTIVE: Personal digital assistants (PDAs) are popular with physicians: in 2003, 33% of Canadian doctors reported using them in their practices. We do not know, however, whether using a PDA changes the behaviour of practising physicians. We studied the effectiveness of a PDA software application to help family physicians diagnose angina among patients with chest pain. DESIGN: Prospective randomized controlled pilot trial using a cluster design. SETTING: Primary care practices in the Toronto area. PARTICIPANTS: Eighteen family physicians belonging to the North Toronto Primary Care Research Network (Nortren) or recruited from a local hospital. INTERVENTIONS: We randomized physicians to receive a Palm PDA (which included the angina diagnosis software) or to continue conventional care. Physicians prospectively recorded the process of care for patients aged 30 to 75 presenting with suspected angina, over 7 months. MAIN OUTCOME MEASURES: Did the process of care for patients with suspected angina improve when their physicians had PDAs and software? The primary outcomes we looked at were frequency of cardiac stress test orders for suspected angina, and the appropriateness of referral for cardiac stress testing at presentation and for nuclear cardiology testing after cardiac stress testing. Secondary outcome was referrals to cardiologists. RESULTS: The software led to more overall use of cardiac stress testing (81% vs 50%). The absolute increase was 31% (P = .007, 95% confidence interval [CI] 8% to 58%). There was a trend toward more appropriate use of stress testing (48.6% with the PDA vs 28.6% control), an increase of 20% (P = .284, 95% CI -11.54% to 51.4%). There was also a trend toward more appropriate use of nuclear cardiology following cardiac stress testing (63.0% vs 45.5%), an absolute increase of 17.5% (P =.400, 95% CI -13.9% to 48.9%). Referrals to cardiologists did not increase (38.2% with the PDA vs 40.9%, P =.869). CONCLUSION: A PDA-based software application can lead to improved care for patients with suspected angina seen in family practices; this finding requires confirmation in a larger study.

Adult↗
PubMed1997

Extended telemedical consultation using Arden Syntax based decision support, hypertext and WWW technique.

There is an obvious need for geographic distribution of expert knowledge among several health care units without increasing the cost of on-site expertise in locations where health care is provided. This paper describes the design of a knowledge-based decision-support system for extended consultation in clinical medicine. The system is based on Arden Syntax for Medical Logic Modules and hypertext using World Wide Web technology. It provides advice and explanations regarding the given advice. The explanations are presented in a hypertext format allowing the user to browse related information and to verify the relevance of the given advice. The system is intended to be used in a closed local network. With special precautions regarding issues of safety and patient security, the system can be used over wider areas such as in rural medicine. A prototype has been developed in the field of clinical microbiology and infectious diseases regarding infective endocarditis.

Artificial Intelligence↗
PubMed2003

EMAP-II expression is associated with macrophage accumulation in primary uveal melanoma.

PURPOSE: Primary uveal melanoma may contain arcs, loops, and networks of periodic acid-Schiff (PAS)-positive patterns, along which numerous macrophages are present. Their recruitment into tumor tissue is mediated by chemotactic cytokines, for which vascular endothelial growth factor (VEGF)-C and endothelial monocyte-activating polypeptide ((EMAP)-II are candidates. In this study, the extent of VEGF-C and EMAP-II immunoreaction was related to infiltration of macrophages. METHODS: Serial sections of 25 primary uveal melanoma lesions were analyzed by immunohistochemistry. RESULTS: The analysis showed no correlation of VEGF-C immunoreaction and localization of macrophages. However, accumulation of macrophages occurred at sites of EMAP-II expression, especially in areas containing nests of tumor cells, surrounded by arcs, loops, and network patterns. In tumors with a strong EMAP-II immunoreaction, the adhesion molecule intracellular adhesion molecule (ICAM)-1 was strongly expressed on endothelial cells. EMAP-II-positive endothelial cells did not express VEGF receptor-2. However, extensive release of von Willebrand factor was observed. Signs of apoptosis were found neither in tumor cells nor endothelial cells. CONCLUSIONS: In uveal melanoma, macrophages accumulate at sites of EMAP-II expression. Based on the results, it may be hypothesized that this process of chemotaxis is facilitated by EMAP-II-dependent expression of ICAM-1 on vascular endothelial cells and concomitantly leads to localized vascular damage, as indicated by release of von Willebrand factor.

Apoptosis↗
PubMed1991

Analysis of an experimental cortical network: II). Connections of visual areas 17 and 18 after neonatal injections of ibotenic acid.

Lesions of cortical areas 17 and 18 were produced in newborn kittens by local injections of the excitotoxin ibotenic acid. In the adult this results in a microcortex which consists of superficial layers I, II and III, in the absence of granular and infragranular layers. Horseradish peroxidase, alone or wheat germ agglutinin conjugated, was injected in the microcortex or in the contralateral, intact areas 17 and 18. The microcortex maintains several connections characteristic of normal areas 17 and 18 of the cat. It receives afferents from the dLGN, and several visual areas of the ipsilateral and contralateral hemisphere. However, it has lost its projections to dLGN, superior colliculus, and, at least in part, those to contralateral visual areas. Thus some parts of the microcortex receive from, but do not project into, the corpus callosum. In addition, the microcortex maintains afferents from ipsilateral and contralateral auditory areas AI and AII which are normally eliminated in development.

Animals↗
PubMed1996

Identification, distribution, and developmental changes of a melatonin binding site in the song control system of the zebra finch.

In many avian species, singing is a circadian or seasonal behavior that appears to be widely dependent on gonadal steroid hormones. To explore the possibility of a further hormone-dependent vocal control mechanism driven by the action of melatonin, we examined the binding of iodinated melatonin (IMEL) in the vocal control network of adult and juvenile (22- and 40-day-old) zebra finches. IMEL binding areas of the zebra finch brain were localized and characterized by using quantitative in vitro autoradiography. In the vocal control system, dense IMEL binding sites were restricted to the nucleus hyperstriatalis ventrale, pars caudalis (HVC). The binding of IMEL to the HVC and to visual areas, e.g., the ectostriatum and the optic tectum, was saturable and showed a single class of high-affinity binding sites with binding affinities (Kds) in the range of 5-20 pM. Competition experiments with various indols and IMEL showed that the IMEL binding site in the zebra finch brain has properties similar to the high-affinity melatonin receptor described in the chicken, in the house sparrow, and in the mammalian brain and retina. Similar to the zebra finch HVC, the HVC of other songbirds, e.g., male canaries and male house sparrows, has the most intense IMEL binding of all areas of the vocal control network. The IMEL binding in the forebrain vocal control areas of the zebra finch, but not that in the visual processing areas, was sexually dimorphic in correlation with the sexually dimorphic neuroanatomy of the forebrain vocal control areas. In the HVC, there is a developmental increase in the maximal number of binding sites for IMEL and in the protein content, so that the adult phenotype of dense IMEL binding develops between day 40 and day 80. The distribution and developmental pattern of IMEL binding in the song system suggests that melatonin has a role in the motor control of singing. Melatonin binding sites in HVC could link HVC-based song control to circadian and circannual changes in the photoperiod independent of gonadal steroids.

Animals↗
PubMed2001

The attentional role of the left parietal cortex: the distinct lateralization and localization of motor attention in the human brain.

It is widely agreed that visuospatial orienting attention depends on a network of frontal and parietal areas in the right hemisphere. It is thought that the visuospatial orienting role of the right parietal lobe is related to its role in the production of overt eye movements. The experiments reported here test the possibility that other parietal regions may be important for directing attention in relation to response modalities other than eye movement. Specifically, we used positron emission tomography (PET) to test the hypothesis that a 'left' parietal area, the supramarginal gyrus, is important for attention in relation to limb movements (Rushworth et al., 1997; Rushworth, Ellison, & Walsh, in press). We have referred to this process as 'motor attention' to distinguish it from orienting attention. In one condition subjects spent most of the scanning period covertly attending to 'left' hand movements that they were about to make. Activity in this first condition was compared with a second condition with identical stimuli and movement responses but lacking motor attention periods. Comparison of the conditions revealed that motor attention-related activity was almost exclusively restricted to the 'left' hemisphere despite the fact that subjects only ever made ipsilateral, left-hand responses. Left parietal activity was prominent in this comparison, within the parietal lobe the critical region for motor attention was the supramarginal gyrus and the adjacent anterior intraparietal sulcus (AIP), a region anterior to the posterior parietal cortex identified with orienting attention. In a second part of the experiment we compared a condition in which subjects covertly rehearsed verbal responses with a condition in which they made verbal responses immediately without rehearsal. A comparison of the two conditions revealed verbal rehearsal-related activity in several anterior left hemisphere areas including Broca's area. The lack of verbal rehearsal-related activity in the left supra-marginal gyrus confirms that this area plays a direct role in motor attention that cannot be attributed to any strategy of verbal mediation. The results also provide evidence concerning the importance of ventral premotor (PMv) and Broca's area in motor attention and language processes.

Adult↗
PubMed2004

Scalable closed-boundary analog neural networks.

In many pattern-classification and recognition problems, separation of different swarms of class representatives is necessary. As well, in function-approximation problems, neurons with a local area of influence have demonstrated measurable success. In our previous work, we have shown how intrinsic quadratic characteristics of traditional metal-oxide-semiconductor (MOS) devices can be used to implement hyperspherical discriminating surfaces in hardware-implemented neurons. In this work, we further extend the concept from quadratic forms to more-arbitrary closed-boundary shapes. Accordingly, we demonstrate how intrinsic characteristics of submicron MOS devices can be utilized to implement efficient pattern discriminators for various applications and, through representative simulations, show their success in some typical function-approximation problems. Further, we offer two mathematical interpretations of possible roles for these networks: Geometrically, we show that our networks employ closed hypercone shapes as their discriminating surfaces; analytically, we show that a set of these synapses connected to a common integrating body calculates the distance between their inputs and weight vectors using a power norm. The feasibility of the idea is practically investigated by design, implementation, and test of a three-dimensional (3-D) closed-boundary pattern classifier, fabricated in 0.35-microm complimentary MOS, whose results are reflected in this work.

Computers, Analog↗