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PubMed2005

A connection rule for alpha-carbon coarse-grained elastic network models using chemical bond information.

A sparser but more efficient connection rule (called a bond-cutoff method) for a simplified alpha-carbon coarse-grained elastic network model is presented. One of conventional connection rules for elastic network models is the distance-cutoff method, where virtual springs connect an alpha-carbon with all neighbor alpha-carbons within predefined distance-cutoff value. However, though the maximum interaction distance between alpha-carbons is reported as 7 angstroms, this cutoff value can make the elastic network unstable in many cases of protein structures. Thus, a larger cutoff value (>11 angstroms) is often used to establish a stable elastic network model in previous researches. To overcome this problem, a connection rule for backbone model is proposed, which satisfies the minimum condition to stabilize an elastic network. Based on the backbone connections, each type of chemical interactions is considered and added to the elastic network model: disulfide bonds, hydrogen bonds, and salt-bridges. In addition, the van der Waals forces between alpha-carbons are modeled by using the distance-cutoff method. With the proposed connection rule, one can make an elastic network model with less than 7 angstroms distance cutoff, which can reveal protein flexibility more sharply. Moreover, the normal modes from the new elastic network model can reflect conformational changes of a given protein better than ones by the distance-cutoff method. This method can save the computational cost when calculating normal modes of a given protein structure, because it can reduce the total number of connections. As a validation, six example proteins are tested. Computational times and the overlap values between the conformational change and infinitesimal motion calculated by normal mode analysis are presented. Those animations are also available at UMass Morph Server (http://biomechanics.ecs.umass.edu/umms.html).

Carbon↗
PubMed2005

Mechanical support of total cavopulmonary connection with an axial flow pump.

OBJECTIVE: Even under optimal circumstances, total cavopulmonary connection is associated with a continuous late risk of death. Hemodynamics are distinctly abnormal, with increased systemic venous pressures and frequent low cardiac output. Our study uses a sheep model of total cavopulmonary connection to test the response to axial flow pump (Thoratec HeartMate II; Thoratec Corporation (Pleasanton, Calif)) support of total cavopulmonary connection, which might be suitable to treat patients with failing Fontan circulation. METHODS: Eight sheep (42-48 kg) were studied. After pilot studies in 3 animals, 5 underwent both pump-supported and nonsupported total cavopulmonary connection in alternating sequence for up to 2 hours. This was achieved with a 12-mm polytetrafluoroethylene graft from the (distally ligated) superior vena cava to the main pulmonary artery and a cannula placed in the inferior vena cava with an attached 16-mm Dacron graft to the main pulmonary artery. Pressures (arterial, inferior vena cava, left atrium, and pulmonary artery) and flows (ascending aorta and inferior vena cava) were recorded over 1 hour both with unsupported total cavopulmonary connection and after placing an axial flow pump (Thoratec HeartMate II) between the inferior vena caval inflow cannula and the main pulmonary artery. RESULTS: Under nonsupported total cavopulmonary connection circulation, inferior vena caval and aortic blood flow decreased by nearly 50%. Inferior vena caval pressure nearly doubled, whereas arterial pressure decreased by one third. Pulmonary artery pressure became nonpulsatile; however, mean pulmonary artery pressure and left atrial pressure did not change significantly. With pump-supported Fontan circulation, cardiac output, inferior vena caval flow, and arterial pressure returned to baseline. Inferior vena caval pressure decreased to below baseline levels. Mean pulmonary artery pressure and left atrial pressure again remained unchanged. CONCLUSIONS: Axial flow pump support from the inferior vena cava to the pulmonary artery can prevent the substantial decrease of aortic flow and pressure associated with total cavopulmonary connection and can reverse its poor hemodynamics. This is a simple model that can be used to further evaluate the potential of mechanical support as a treatment option in failing Fontan circulation.

Animals↗
PubMed2006

Flow study of an extracardiac connection with persistent left superior vena cava.

BACKGROUND: Numerous studies have sought to optimize the design of total cavopulmonary connections with a single superior vena cava. This study was directed to the 2% to 4.5% of the population with dual superior venae cavae, investigating the flow fields associated with such total cavopulmonary connection anatomies. Additionally, it demonstrates the potential use of computational designs and simulations as surgical planning tools. METHODS: A 3-dimensional model of a total cavopulmonary connection with bilateral superior venae cavae was reconstructed from a patient's magnetic resonance images and investigated experimentally and numerically to assess the power losses and flow structures within the connection. On the basis of these results, a virtual operation was performed in the computer to improve the original connection design. The modified anatomy was studied numerically. RESULTS: Because of a smooth connection with an extracardiac conduit and no major dimension mismatch between the baffle and the connecting vessels, the original anatomy yielded smooth flow fields, low power losses, and few disturbances. However, a large offset between the inferior vena cava and the left superior vena cava resulted in flow stasis and unbalanced hepatic flow distribution. Shifting the inferior vena cava and positioning it between the 2 superior venae cavae resulted in a 7% decrease in power losses and eliminated the associated flow stasis regions in the main pulmonary artery segment. CONCLUSIONS: This study demonstrates the potential use of computer-aided design and numeric simulations for surgical planning. It shows that locating the inferior vena cava between the superior venae cavae may lead to better-balanced lung perfusion. This may require suturing the right and left superior venae cavae closer to each other during the hemi-Fontan or Glenn stage.

Anastomosis, Surgical↗
PubMed2007

Morphologic features of the uniatrial but biventricular atrioventricular connection.

OBJECTIVES: Hearts with an absent atrioventricular connection and a straddling of the solitary atrioventricular valve are rare but significant lesions. They are suitable only for Fontan-like palliation, in which atrioventricular valvar abnormalities play a significant role in determining the outcome. We studied the segmental arrangements in such lesions and clarified the valvar morphology, particularly its surgical implications. METHODS: We made a macroscopic review of all specimens with an absent atrioventricular connection and a straddling atrioventricular valve that were held in the collections of 3 institutes. We included only those specimens with the straddling valve supported exclusively by either the right-sided or left-sided atrioventricular junction and excluded those with a common atrioventricular junction. RESULTS: We found 11 hearts with an absent right atrioventricular connection and a straddling left atrioventricular valve, and 3 with an absent left atrioventricular connection and a straddling right atrioventricular valve. Most had right-hand ventricular topology and discordant ventriculoarterial connections. We found multiple valvar abnormalities, including dysplastic leaflets, short cords, abnormal attachments, and abnormal papillary muscles. The most consistent features were a line of maximal coaptation between the bridging leaflets always perpendicular to the plane of the ventricular septum and a free-floating bridging anterosuperior leaflet. CONCLUSIONS: Straddling of a solitary atrioventricular valve with an absent atrioventricular connection produces a uniatrial but biventricular connection. In this setting, the valve guarding the abnormal solitary atrioventricular junction cannot be classified morphologically as mitral or tricuspid. The markedly variable valvar morphology likely makes these valves prone to insufficiency in the long term.

Heart Defects, Congenital↗
PubMed2005

Sex-related differences in amygdala functional connectivity during resting conditions.

Recent neuroimaging studies have established a sex-related hemispheric lateralization of amygdala involvement in memory for emotionally arousing material. Here, we examine the possibility that sex-related differences in amygdala involvement in memory for emotional material develop from differential patterns of amygdala functional connectivity evident in the resting brain. Seed voxel partial least square analyses of regional cerebral blood flow data revealed significant sex-related differences in amygdala functional connectivity during resting conditions. The right amygdala was associated with greater functional connectivity in men than in women. In contrast, the left amygdala was associated with greater functional connectivity in women than in men. Furthermore, the regions displaying stronger functional connectivity with the right amygdala in males (sensorimotor cortex, striatum, pulvinar) differed from those displaying stronger functional connectivity with the left amygdala in females (subgenual cortex, hypothalamus). These differences in functional connectivity at rest may link to sex-related differences in medical and psychiatric disorders.

Adult↗
PubMed2006

Aging is associated with contrasting changes in local and distant cortical connectivity in the human motor system.

Pathophysiological changes in neurological and neuropsychiatric diseases are increasingly described in terms of abnormal network connectivity. However, the anatomical integrity and efficacy of connections among multiple brain regions change with aging, even in healthy adults. We combined low-frequency transcranial magnetic stimulation and positron emission tomography to study the age-related changes in regional activation and effective connectivity, associated with voluntary action by healthy adults between 22 and 68 years old. Contrasting effects of aging on the motor network were seen using analyses of regional activation, effective connectivity mediating task-related neuronal activation and effective connectivity in response to transcranial magnetic stimulation. Low-frequency rTMS reduced cerebral blood flow during both movement and resting conditions, at the site of stimulation and neighboring frontal cortex. Aging was associated with increased movement-related activation in premotor cortex, bilaterally. Increasing age also increased the susceptibility of the cortex to the inhibitory effects of rTMS, at the site of stimulation and its contralateral homologue. Moreover, older subjects showed enhanced local effective connectivity, centered on the left premotor cortex, but reduced effective connectivity between distant motor-related cortical areas. We discuss these results in relation to the HAROLD model of aging and propose that there are differential effects of aging on local and distributed neuronal subpopulations in the motor network. This differential effect of aging has important implications for the study of neurodegenerative and cerebrovascular diseases that primarily affect older people, as well as our understanding of the normal aging process.

Adult↗
PubMed2005

The bed nucleus of the stria terminalis in the Syrian hamster: subnuclei and connections of the posterior division.

The bed nucleus of the stria terminalis is a key part of a ring of cells extending between the centromedial amygdala and bed nucleus of the stria terminalis referred to as the extended amygdala. The present study describes the architecture of the bed nucleus of the stria terminalis and the connections of subnuclei in posterior bed nucleus of the stria terminalis. The hamster bed nucleus of the stria terminalis is readily allotted to anterior and posterior divisions separated by the fibers of the body of the anterior commissure. The anterior division has four subnuclei: anteromedial, anterointermediate, anterolateral, and anteroventral. Within the posterior division, there are three distinct regions: posteromedial, posterointermediate, and posterolateral. In hamsters, the posterior bed nucleus of the stria terminalis contributes to male sexual behavior, particularly chemoinvestigation. Moreover, the posterior bed nucleus of the stria terminalis is part of a neural circuit essential for mating, including the medial amygdaloid nucleus and medial preoptic area. The connections of bed nucleus of the stria terminalis, posteromedial part, bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posterolateral part were visualized by co-injection of anterograde (Phaseolus vulgaris leucoagglutinin) and retrograde (cholera toxin B) tract tracers. The bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part have dense bidirectional connections with medial amygdaloid nucleus and cortical amygdala via the stria terminalis and ventral amygdalofugal pathway. These subnuclei also maintain bidirectional connections with steroid-concentrating areas including lateral septum, medial preoptic area, hypothalamus, and periaqueductal gray. The bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part receive projections from the subiculum and send projections to deep mesencephalic nuclei. By contrast, the bed nucleus of the stria terminalis, posterolateral part is connected with the central amygdala, lateral hypothalamus, subthalamic nucleus, nucleus accumbens, substantia innominata, substantia nigra and thalamus. Thus, the bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part have similar connections with areas involved in social behaviors. The bed nucleus of the stria terminalis, posterolateral part maintains connections with areas involved in motivational circuits. This supports the concept of distinct circuits within the extended amygdala which differentially link the centromedial amygdala and bed nucleus of the stria terminalis.

Animals↗
PubMed2005

Abnormal effective connectivity of dopamine D2 receptor binding in schizophrenia.

Receptor binding has been examined region by region in both in vitro and in vivo studies, but less attention has been paid to the connectivity of regional receptor binding despite the fact that neurophysiological studies have indicated an extensive inter-regional connectivity. In this study, we investigated the connectivity of regional dopamine D2 receptor binding in positron emission tomography data from 10 drug-naive patients with schizophrenia and 19 healthy controls. We applied a structural equation method to regional receptor binding. The results indicated that the network models of the patients and normal subjects were significantly different. As to the individual path coefficients, (a) connectivity between cortical regions was different between groups; (b) connectivity from the prefrontal cortex, parietal cortex, and thalamus to the anterior cingulate differed from that in controls; and (c) connectivity from the prefrontal cortex to the anterior cingulate and thalamus via the hippocampus was observed in normal subjects but not in patients. These results suggest that a systems-level change reflected in the connectivity of D2 receptor binding is present in schizophrenia.

Adult↗
PubMed1999

Topographic organization of the striatal and thalamic connections of rat medial agranular cortex.

The rostral and caudal portions of rat medial agranular cortex (AGm) play different functional roles. To refine the anatomical framework for understanding these differences, axonal tracers were used to map the topography of the connections of AGm with the striatum and thalamus. The striatal projections follow mediolateral and rostrocaudal gradients that correspond to the locations of the neurons of origin within AGm. Projections from rostral AGm are widespread and dense rostrally, then coalesce into a circumscribed dorsocentral region at the level of the pre-commissural septal nuclei. Projections from mid and caudal AGm are less widespread and less dense, and are focused more caudally. Striatal projections from the adjacent anterior cingulate and lateral agranular areas overlap those of AGm but are concentrated more medially and laterally, respectively. Thalamic connections of AGm are organized so that more caudal portions of AGm have connections with progressively more lateral and caudal regions of the thalamus, and the full extent of AGm is connected with the ventrolateral (VL) nucleus. Rostral AGm is interconnected with the lateral portion of the mediodorsal nucleus (MD1), VL, and the central lateral (CL), paracentral (PC), central medial, rhomboid and ventromedial nuclei. Caudal AGm has robust connections with VL, the posterior, lateral posterior and lateral dorsal nuclei, but little or none with MD1, CL/PC and VM. These differences in the subcortical connections of rostral and caudal AGm parallel their known differences in corticocortical connections, and represent another basis for experimental explorations of the functional roles of these cortical territories.

Animals↗
PubMed1994

Memory T waves after radiofrequency catheter ablation of accessory atrioventricular connections in Wolff-Parkinson-White syndrome.

Generalized, extensive electrical repolarization abnormalities, represented by negative or abnormally peaked T waves, are frequently observed after radiofrequency catheter ablation of overt accessory atrioventricular (AV) connections in Wolff-Parkinson-White (WPW) syndrome. Two mechanisms have been proposed to explain these changes: subendocardial injury, secondary to the application of radiofrequency lesions, and memory T waves. The purpose of this study is to evaluate the electrocardiographic (ECG) changes in patients with overt and concealed accessory AV connections after ablation. Fifty-one patients with accessory AV connections who underwent successful radiofrequency ablation were included in the study. Twenty-four patients with clear, manifest, and permanent preexcitation (group 1) were compared with 27 patients with concealed accessory AV connections (group 2). Electrocardiograms were obtained in all patients before ablation, shortly after ablation (within 4 hours), and late after ablation (6 weeks). The frontal and horizontal QRS-T angles in the ECGs, number of lesions, total Joules applied, total peak creatine kinase, and total peak creatine kinase-MB units were compared in both groups. Of the 24 patients with overt accessory AV connections, 23 (95.8%) demonstrated repolarization abnormalities in the ECG shortly after the procedure that reverted almost completely at 6 weeks. Of the 27 patients with concealed accessory AV connections, only 2 (7.4%) demonstrated repolarization abnormalities after the ablation (P < .0001). The persistence of an abnormal QRS-T angle immediately after ablation in patients with overt accessory AV connections is caused by an abnormality in the T wave axis, opposite to the direction of the normal QRS axis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2006

Contribution of feedforward, lateral and feedback connections to the classical receptive field center and extra-classical receptive field surround of primate V1 neurons.

A central question in visual neuroscience is what circuits generate the responses of neurons in the primary visual cortex (V1). V1 neurons respond best to oriented stimuli of optimal size within their receptive field (RF) center. This size tuning is contrast dependent, i.e. a neuron's optimal stimulus size measured at high contrast (the high-contrast summation RF, or hsRF) is smaller than when measured using low-contrast stimuli (the low-contrast summation RF, or lsRF). Responses to stimuli in the RF center are usually suppressed by iso-oriented stimuli in the extra-classical RF surround. Iso-orientation surround suppression is fast and long range, extending well beyond the size of V1 cells' lsRF. Geniculocortical feedforward (FF), V1 lateral and extrastriate feedback (FB) connections to V1 could all contribute to generating the RF center and surround of V1 neurons. Studies on the spatio-temporal properties and functional organization of these connections can help disclose their specific contributions to the responses of V1 cells. These studies, reviewed in this chapter, have shown that FF afferents to V1 integrate signals within the hsRF of V1 cells; V1 lateral connections are commensurate with the size of the lsRF and may, thus, underlie contrast-dependent changes in spatial summation, and modulatory effects arising from the surround region closer to the RF center (the "near" surround). The spatial and temporal properties of lateral connections cannot account for the dimensions and onset latency of modulation arising from more distant regions of the surround (the "far" surround). Inter-areal FB connections to V1, instead, are commensurate with the full spatial range of center and surround responses, and show fast conduction velocity consistent with the short onset latency of modulation arising from the "far" surround. We review data showing that a subset of FB connections terminate in a patchy fashion in V1, and show modular and orientation specificity, consistent with their proposed role in orientation-specific center-surround interactions. We propose specific mechanisms by which each connection type contributes to the RF center and surround of V1 neurons, and implement these hypotheses into a recurrent network model. We show physiological data in support of the model's predictions, revealing that modulation from the "far" surround is not always suppressive, but can be facilitatory under specific stimulus conditions.

Animals↗
PubMedDate not supplied

Intra- and interganglionic synaptic connections in the CNS of Aplysia.

Synaptic connections were found between two groups of neurons in the CNS of Aplysia, the cerebral ganglion A and B cluster neurons which are involved in the control of pedal and parapodial movements and neurons in the pleural ganglion which has been shown to modulate locomotion. The A and B neurons made synaptic connections in both the cerebral and pleural ganglia. Pleural neurons had synaptic connections among themselves and with A and B neurons. The A neurons made excitatory monosynaptic connections with the B neurons and a minimum of 6 pleural neurons including the left giant cell (LGC). All of the A neuron synapses found were excitatory. The B neurons received excitatory synaptic input from two other groups of neurons in the cerebral ganglion and both excitatory and inhibitory input from pleural neurons. The latter were identified on the basis of their synaptic connections with the LGC and A neurons. The B neurons and LGC had several common synaptic inputs. The A neurons received monosynaptic input from only 2 pleural neurons. Complex synaptic circuits between A and B neurons and pleural neurons were found. These included recurrent inhibition of B neurons by A neurons via a pleural interneuron, feedforward summation of A neuron synaptic input to the LGC, and reciprocal excitatory synaptic connections between B and the pleural neurons. The activity of the B neurons was modulated by direct inhibitory and excitatory synaptic connections from pleural neurons. The A neurons were modulated primarily by a polysynaptic pathway through the B neurons. The modulation of cerebral A and B neurons by pleural neurons is consistent with behavioral results obtained studying locomotion.

Animals↗
PubMed2000

Combining independent component analysis and correlation analysis to probe interregional connectivity in fMRI task activation datasets.

A new approach in studying interregional functional connectivity using functional magnetic resonance imaging (fMRI) is presented. Functional connectivity may be detected by means of cross correlating time course data from functionally related brain regions. These data exhibit high temporal coherence of low frequency fluctuations due to synchronized blood flow changes. In the past, this fMRI technique for studying functional connectivity has been applied to subjects that performed no prescribed task ("resting" state). This paper presents the results of applying the same method to task-related activation datasets. Functional connectivity analysis is first performed in areas not involved with the task. Then a method is devised to remove the effects of activation from the data using independent component analysis (ICA) and functional connectivity analysis is repeated. Functional connectivity, which is demonstrated in the "resting brain," is not affected by tasks which activate unrelated brain regions. In addition, ICA effectively removes activation from the data and may allow us to study functional connectivity even in the activated regions.

Adult↗
PubMed1999

Connectivity and the elastic properties of cancellous bone.

This study addresses the possible significance of trabecular connectivity for the mechanical quality of cancellous bone. A total of 141 cubic trabecular bone specimens collected from autopsy material from 56 individuals without any known bone or metastatic diseases were used. Age variation was in the range of 14-91 years and a wide range of trabecular architecture was found. Each specimen was three-dimensionally reconstructed with a voxel size of either 20 or 25 microm. Using the detailed three-dimensional reconstructions as input for microstructural finite-element models, the complete elastic properties of the trabecular architecture were obtained and maximum and mean stiffness could be calculated. Volume fraction and true three-dimensional architectural measurements of connectivity density and surface density were determined. Connectivity density was determined in an unbiased manner by the Euler number, which is a topological property. Using multiple regression analysis it was found that volume fraction explained by far the greatest part (84%-94%) of the variation in both mean and maximum stiffness. When connectivity density and surface density were included, the correlations increased marginally to 89%-95%. Noticeably negative regression coefficients were found for connectivity density. The results suggest that, in normal cancellous bone, the connectivity density has very limited value for assessment of elastic properties by morphological variables, but if a relation exists then stiffness decreases with increasing connectivity.

Adolescent↗
PubMed1990

Cortical connections of MT in four species of primates: areal, modular, and retinotopic patterns.

Cortical connections were investigated by restricting injections of WGA-HRP to different parts of the middle temporal visual area, MT, in squirrel monkeys, owl monkeys, marmosets, and galagos. Cortex was flattened and sectioned tangentially to facilitate an analysis of the areal patterns of connections. In the experimental cases, brain sections reacted for cytochrome oxidase (CO) or stained for myelin were used to delimit visual areas of occipital and temporal cortex and visuomotor areas of the frontal lobe. Major findings are as follows: (1) The architectonic analysis suggests that in addition to the commonly recognized visual fields, area 17 (V-I), area 18 (V-II), and MT, all three New World monkeys and prosimian galagos have visual areas DL, DI, DM, MST, and FST. (2) Measurements of the size of these areas indicate that about a third of the neocortex in these primates is occupied by the eight visual areas, but they occupy a somewhat larger proportion of neocortex in the diurnal marmosets and squirrel monkeys than the nocturnal owl monkeys and galagos. The diurnal primates also have proportionally more neocortex devoted to areas 17, 18, and DL and less to MT. These differences are compatible with the view that diurnal primates are more specialized for detailed object and color vision. (3) In all four primates, restricted locations in MT receive major inputs from short meandering rows of neurons in area 17 and several bands of neurons in area 18. (4) Major feedforward projections of MT are to two visual areas adjoining the rostral half of MT, areas MST and FST. Other ipsilateral connections are with DL, DI, and in some cases DM, parts of inferotemporal (IT) cortex, and posterior parietal cortex. (5) In squirrel monkeys, where injection sites varied from caudal to rostral MT, caudal parts of MT representing central vision connect more densely to DL and IT than other parts. Both DL and IT cortex emphasize central vision. (6) In the frontal lobe, MT has dense connections with the frontal ventral area (FV), but not with the frontal eye field (FEF). (7) Callosal connections of MT are most dense with matched locations in MT of the other hemisphere, rather than with the outer boundary of MT representing the vertical meridian. Targets of sparser callosal connections include FST, MST, and DL.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Subcortical connections of subdivisions of inferior temporal cortex in squirrel monkeys.

On the basis of cortical connections and architectonics, inferior temporal (IT) cortex of squirrel monkeys consists of a caudal, prestriate-recipient region, ITC; a rostral region, ITR; and possibly an intermediate region along the border of ITC and ITR, "ITI" (Weller & Steele, 1992). ITC contains dorsal (ITCd) and ventral (ITCV) areas. The subcortical connections of these subdivisions of IT cortex were determined in the present study from the results of cortical injections of wheat-germ agglutinin conjugated to horseradish peroxidase, [3H]-amino acids and fast blue. ITC and ITR receive afferents from the locus coeruleus, dorsal raphe, nucleus annularis, central superior nucleus, pontine reticular formation, lateral hypothalamus, paracentral nucleus, and central medial nucleus; send efferents to the superior colliculus, reticular nucleus, and striatum; and have both afferent and efferent connections with the pretectum, pulvinar, claustrum, amygdala, and basal nucleus of Meynert. ITC and ITR have different patterns of connections with a number of subcortical structures, including the pulvinar and amygdala. Injections in ITC strongly label multiple nuclei of the inferior pulvinar and the medial division of the lateral pulvinar (PLM), and moderately label the medial pulvinar (PM), whereas injections in ITR strongly label PM and moderately label PLM. Injections in ITC label sparse projections to the lateral nucleus of the amygdala, in contrast to injections in ITR that label strong projections to the lateral and basal nuclei of the amygdala. Injections in "ITI" produce a pattern of subcortical label that has some features of that observed from injections in ITC and that observed from injections in ITR. Although most of the connections of ITCd and ITCv appear similar, only injections involving ITCd label the middle nucleus of the inferior pulvinar (PIM). Comparison of the subcortical connections of subdivisions of IT cortex in squirrel monkeys and what is presently known of the subcortical connections of subdivisions of IT cortex in macaque monkeys supports the previous suggestion that ITC of squirrel monkeys may be comparable to area TEO of macaques, ITI may be comparable to posterior area TE, and ITR may be comparable to anterior area TE (Weller & Steele, 1992).

Afferent Pathways↗
PubMed1991

Visuotopic organization of the lateral suprasylvian area and of an adjacent area of the ectosylvian gyrus of cat cortex: a physiological and connectional study.

We have explored the visuotopic organization of the territory surrounding the middle suprasylvian sulcus (MSS) of cat cerebral cortex by electrophysiological mapping, and by tracing the topography of its cortical and subcortical connections using wheatgerm-agglutinin horseradish peroxidase (WGA-HRP). Observations from the two approaches were concordant, and confirmed the presence of two separate visual areas in the MSS that approximate, but do not exactly correspond, to the location and internal organization of the posterior medial and posterior lateral lateral suprasylvian (PMLS, PLLS) areas of Palmer et al. (1978). We define as part of the lateral suprasylvian (LS) area the territory on the medial bank and caudal end of the lateral bank of the MSS that receives a topographically organized projection from the region of area 17 representing the lower visual quadrant. This territory is connected with other structures that are themselves striate-recipient (cortical areas 18 and 19, and the lateral division of the lateral posterior (LPl) nucleus), and with a variety of nuclei that receive direct retinal input, such as the C-laminae of the LGd, the medial interlaminar nucleus (MIN), and the superficial layers of the superior colliculus (SC). Its connections with the LPl, LGd, MIN, and SC correspond topographically with the input from area 17. Revised maps of area LS were produced from the physiological and connectional data: its rostral border is formed by a representation of lower visual elevations with the horizontal meridian represented caudally, and its lateral border is formed by the vertical meridian; area LS shares a representation of the center of gaze with the visual area of the lateral bank at its caudal end. The adjacent lateral bank area has larger receptive fields than area LS, and very different connectivity. It receives no input from area 17 and little input from striate-recipient structures, including area LS, but instead is connected to more remote extrastriate visual areas, such as the anterior ectosylvian visual (AEV) area in insular cortex, and to zones of the thalamus in receipt of tectal input (LPm and the lateromedial-suprageniculate nuclear complex). According to both mapping approaches, the lateral bank area contains representations of both the upper and lower visual quadrants but a rather limited degree of visuotopic order. We refer to it as the posterior ectosylvian visual (PEV) area, because it appears to be functionally and connectionally dissociated from area LS, but is possibly a functional antecedent of area AEV.

Animals↗
PubMedDate not supplied

3D connectivity indices in QSPR/QSAR studies.

Topographic (3D) molecular connectivity indices based on molecular graphs weighted with quantum chemical parameters are used in QSPR and QSAR studies. These descriptors were compared to 2D connectivity indices (vertex and edge ones) and to quantum chemical descriptors in modeling partition coefficient (log P) and antibacterial activity of 2-furylethylene derivatives. In describing log P the 3D connectivity indices produced a significant improvement (more than 29%) in the predictive capacity of the model compared to those derived with topological and quantum chemical descriptors. The best linear discriminant model for classifying antibacterial activity of these compounds was also obtained with the use of 3D connectivity indices. The global percent of good classification obtained with 3D and 2D connectivity as well as quantum chemical descriptors were 94.1, 91.2, and 88.2, respectively. In general, all these models predict correctly the antibacterial activity of a set of nine new 2-furylethylene derivatives. The best result is obtained with 3D connectivity indices that classified correctly 100% of these compounds versus 88.9% obtained with 2D connectivity or quantum chemical descriptors.

Journal Article↗