Medial Sector Research Articles

Activity-Dependent Synaptic Plasticity in the Central Nucleus of the Amygdala

Much evidence indicates that fear conditioning involves potentiation of some thalamic inputs to the lateral amygdala (LA). In turn, the LA would excite more neurons in the central nucleus (CE), leading to the generation of fear responses via their brainstem and hypothalamic projections. However, the posterior thalamus not only projects to LA but also to the medial sector of CE (CEm), suggesting that CEm might also be a site of plasticity. To test whether CEm also exhibits activity-dependent synaptic plasticity, we performed whole-cell recordings of CEm neurons in amygdala slices and stimulated thalamic axons coursing through the internal capsule and, as a control, the basolateral (BL) nucleus. High-frequency stimulation of thalamic inputs led to a long-lasting potentiation of thalamic responses, whereas BL-evoked responses remained unchanged. This thalamic long-term potentiation (LTP) developed even when slices were prepared with a cut severing the connections between the LA and CEm but was greatly reduced when an NMDA receptor antagonist was added to the perfusate shortly before and during LTP induction. Yet, intracellular dialysis with the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate did not prevent induction of the thalamic LTP, suggesting that presynaptic NMDA receptors are required for its induction. Consistent with this, the thalamic LTP also developed when the cells were dialyzed with a calcium chelator or kept hyperpolarized during induction. Finally, this thalamic LTP was associated with reduced amounts of paired-pulse facilitation, suggesting that it is expressed presynaptically. These results are consistent with the idea that the CEm plays an active role in fear conditioning.

Long-term ovariectomy decreases ovine compact bone viscoelasticity

Changes in bone mineral density associated with estrogen depletion in humans do not account for all of the associated change in fracture risk, and it is possible that some of this variation may lie in changes of other aspects of bone quality. The purpose of this study was to investigate changes in viscoelastic behavior of compact bone that may be associated with estrogen depletion. Changes in compact bone viscoelastic properties associated with three years of ovariectomy were investigated with dynamic mechanical analysis (low-amplitude 3-point bending at frequencies of 1–20 Hz) using beams milled from the diaphysis of the ovine radius. The viscoelastic storage modulus was significantly (5.2%) lower at the higher frequencies for the ovariectomized animals. The general anatomic variation in storage modulus, in which cranial sectors had higher values than caudal sectors, did not change with ovariectomy. The loss tangent (tan δ, a measure of damping) was also greatly decreased (up to 83%) at high frequencies in the ovariectomized animals. Anatomic variation in tan δ at low (6–12 Hz) frequencies (cranial and caudal sectors having higher values than lateral or medial sectors) was enhanced with ovariectomy. Changes in viscoelastic properties associated with long-term estrogen depletion could be responsible for a significant reduction in the toughness or strength of a bone without concomitant changes in screening modalities used to evaluate bone quality (e.g., DXA, QCT, QUA).

てんかん外科におけるＯｐｔｉｃ Ｔｒａｃｔｏｇｒａｐｈｙの役割

Diffusion tensor tractography is a newly developed method for tracing tracts in white matter using combination of diffusion tensor images. We evaluate the degree of impairment of optic tracts in the cases with visual field defect after temporal lobectomy using diffusion tensor tractography. We examined 8 cases after temporal lobectomy for temporal lobe epilepsy. Visual field defect in medial sector and lateral sector of upper 1/4 visual field were evaluated. Diffusion tensor tractography of optic radiation was made from 6 axes diffusion tensor images. We evaluated the correlation between the degree of visual field defect and visualization of Meyer's loop on tractographies. Medial sector field tends to be impaired after temporallobectomy. Diffusion tensor tractography showed incomplete to no visualization of Meyer's loop in the cases with severe visual field defect. While, visualization of optic radiation was almost complete in cases with mild visual field defect. Diffusion tensor tractography was useful in evaluating post surgical changes in optic radiation. Potential usefulness of tractography in surgical planning was also suggested.

Amelioration of hippocampal neuronal damage after transient forebrain ischemia in cyclooxygenase-2-deficient mice.

Several studies have suggested that cyclooxygenase-2 (COX-2) plays a role in ischemic neuronal death. Genetic disruption of COX-2 has been shown to reduce susceptibility to focal ischemic injury and N-methyl-d-aspartate-mediated neurotoxicity. The purpose of this study was to examine the effects of COX-2 deficiency on neuronal vulnerability after transient forebrain ischemia. Marked upregulation of COX-2 immunostaining in neurons was observed at the early stage and prominent COX-2 staining persisted in the CA1 medial sector and CA2 sector over 3 days after ischemia. The immunohistologic pattern of COX-2 staining in these sectors gradually condensed to a perinuclear location. The degree of hippocampal neuronal injury produced by global ischemia in COX-2-deficient mice was less than that in wild-type mice, coincident with attenuation of DNA fragmentation in the hippocampus. Also, treatment with a selective COX-2 inhibitor, nimesulide, after ischemia decreased hippocampal neuronal damages. These results of genetic disruption and chemical inhibition of cyclooxygenase-2 show that inhibition of COX-2 ameliorates selective neuronal death after transient forebrain ischemia in mice.

Determinants of Quality of Life in Dimapur Nagaland (India)

This study is an attempt to identify the determinant factors of quality of life in Dimapur and its periphery. Dimapur town is the most important and cosmopolitan commercial centre of Nagaland, India. We delineate the township into five concentric rings around the CBD and every ring into several sectors. Then twenty one sites have been chosen randomly from these sectors; four each from the first and the second sectors, five each from the third and the fourth sectors, and three from the fifth sector (control). From each site, we have selected eleven households randomly to collect information on the scheduled variables - 113 in number - reflecting various aspects of quality of life (e.g. education, housing, utilities and amenities, accessibility, waste disposal and environment, income & expenditure, entertainment, health condition, etc.). In total, we have surveyed two hundred thirty one (231) households. Factor analysis is used for resolving the multivariate complex of data into a handful of composite variables identified as: (1) High-End Consumption, (2) Low-End Consumption; (3) Consumption of Public Goods, Commons and Negative Spillovers, (4) Supplementary Consumption, and (5) Health-related Attributes. A regression analysis of spatial distribution of mean factor scores over the sectors of the township reveals that mean scores of factors #1, #2, and #4 (that are closely related with standard of living) are lower in the CBD and rise as we move away to sectors #2 and #3. They attain their peak in sector #3 and after that the experience a decline as we move away further to sectors #4 and #5. On the other hand, factor #3, monotonically decreases as we move away from the central business district (CBD) to the periphery. The CBD is more crowded and polluted. It caters to the largest floating population who over-use the public facilities there. Factor #5 (related with poor health conditions) scores higher in the CBD and as we move away to sectors # 3 and #4, a decline is observed. Health conditions are poorer in the CBD and better in sectors #3 and #4. But due to poor conditions of living, health in the rural areas scores poorer. We conclude that standard of living and consumption of public goods/services including negative spillover determine quality of life. The QOL in the medial sector between the CBD and the periphery is better than that in other sectors mainly due to higher standard of living but QOL due to consumption of public goods/externalities monotonically improves as we move away from the CBD. The overall index of quality of life has a weak relationship with the nature of employment of the respondents. The advance Nagas (Semas, Angamis, Aos and Lothas) score favourably on the Factors of QOL relating to the standard of living, but they also share the negative spillovers of urban living more in proportion. Zeliangs and Kukis score unfavourably on the standard of living but they share the urban externalities and negative spillover of urban living lesser in proportion.

Quality of Life in Dimapur Nagaland (India)

This study deals with several issues relating to an investigation into conceptualization, definition, measurement, spatial and community-wise distribution, asymmetry, inequality and a few other related aspects of quality of life in a commercial township of a developing tribal-abundant state located in a less developed, hilly and frontier region of India. Unlike many studies on the assessment of quality of life at a macro level wherein certain gross indicators (mortality rates, per capita income or literacy rate, etc. at the national or the regional level) have conventionally been used to measure QOL, in this investigation we measure QOL by means of 135 micro-level indicators - at the household and his neighbourhood level. Four facets of QOL are visualized - those related to housing, economic aspects and high consumption, which are singularly dominant and positive. They together contribute over 97 percent to the Composite Index of QOL. The fourth facet relates to accessibility. It contributes but only a little to the Index. The distribution of sample households according to the value of the Composite Index of QOL is asymmetric around the mean value. Overall, the sample households are closer to the Hell point and farther from the Bliss point. Asymmetry is the least in sector 3 followed by sector 4, and the most in sector 5 followed by the sectors 2 and 1. Average Quality of Life improves as one moves away from the core of the city, attains it peak at the medial sector and sharply declines afterwards. There are a number of destitute households in the sample. Most of them are in the rural outskirts of Dimapur, but scarcely a few in the sectors 2 and 3, where average quality of life is better. Perhaps, a residence in sector 2 or 3 is economically inaccessible to them. Construction of the facet indices as well as the composite index based on full matrix of inter-correlation among the indicators of QOL yields better results than if the indices are constructed by using block-diagonal partial information. A perusal of the table containing loadings of pooled object variables (indicators) suggests that about one-fourth of the loadings (absolute value) are less than 0.10. Exclusion of such variables from the object set would not affect the composite index of QOL adversely, but only add to the parsimony. However, retaining them does not have any undesirable affect. We avoid pruning them out. An advice to exclude such 'weaklings' from the set of object variables in order to enhance the explanatory power of the index is rather usual. We hold that such an advice is naive and its practice illusive. An inference based on partial information can never outperform the inference based on full information.

Sulfated proteoglycans as modulators of neuronal migration and axonal decussation in the developing midbrain.

Proteoglycans are abundant in the developing brain and there is much circumstantial evidence for their roles in directional neuronal movements such as cell body migration and axonal growth. We have developed an in vitro model of astrocyte cultures of the lateral and medial sectors of the embryonic mouse midbrain, that differ in their ability to support neuritic growth of young midbrain neurons, and we have searched for the role of interactive proteins and proteoglycans in this model. Neurite production in co-cultures reveals that, irrespective of the previous location of neurons in the midbrain, medial astrocytes exert an inhibitory or nonpermissive effect on neuritic growth that is correlated to a higher content of both heparan and chondroitin sulfates (HS and CS). Treatment of astrocytes with chondroitinase ABC revealed a growth-promoting effect of CS on lateral glia but treatment with exogenous CS-4 indicated a U-shaped dose-response curve for CS. In contrast, the growth-inhibitory action of medial astrocytes was reversed by exogenous CS-4. Treatment of astrocytes with heparitinase indicated that the growth-inhibitory action of medial astrocytes may depend heavily on HS by an as yet unknown mechanism. The results are discussed in terms of available knowledge on the binding of HS proteoglycans to interactive proteins, with emphasis on the importance of unraveling the physiological functions of glial glycoconjugates for a better understanding of neuron-glial interactions.

The ‘Seamless Web’: The Development of the Electronic Patient Record in Aarhus Region, Denmark

The article surveys the organization of the current project to develop an electronic patient record in the Aarhus Region, Denmark. The article is based on various policy documents and reports as well as a number of semi-structured interviews with project managers from the EPR organization in Aarhus County and with participants in the development process at local hospitals. This material is used to present and discuss the framing of the project in a 'discourse coalition'. The stabilization of a specific discourse coalition has been an important factor in ensuring the success of the development project up to the present moment. This coalition became relatively stable by integrating a diverse set of actors in a story-line about the relationships between co-operation, management and technology in the medial sector, and has influenced the modular organization of the project. The successful maintenance of the discourse coalition allows the project to appear 'seamless' from the outside. Conversely, the project is likely to be continually reviewed as successful only to the extent that it is able to flexibly keep the fluctuating set of relevant actors in alignment. If the practical work of keeping a coalition in place remains invisible it becomes easy to imagine an ideal way of planning large socio-technical projects, like developing an ECR. But practical success is more likely to be achieved if one takes seriously the thorough intertwining of discursive, organizational and technical aspects of development projects.

Modulators of axonal growth and guidance at the brain midline with special reference to glial heparan sulfate proteoglycans.

Bilaterally symmetric organisms need to exchange information between the left and right sides of their bodies to integrate sensory input and to coordinate motor control. Thus, an important choice point for developing axons is the Central Nervous System (CNS) midline. Crossing of this choice point is influenced by highly conserved, soluble or membrane-bound molecules such as the L1 subfamily, laminin, netrins, slits, semaphorins, Eph-receptors and ephrins, etc. Furthermore, there is much circumstantial evidence for a role of proteoglycans (PGs) or their glycosaminoglycan (GAG) moieties on axonal growth and guidance, most of which was derived from simplified models. A model of intermediate complexity is that of cocultures of young neurons and astroglial carpets (confluent cultures) obtained from medial and lateral sectors of the embryonic rodent midbrain soon after formation of its commissures. Neurite production in these cocultures reveals that, irrespective of the previous location of neurons in the midbrain, medial astrocytes exerted an inhibitory or non-permissive effect on neuritic growth that was correlated to a higher content of both heparan and chondroitin sulfates (HS and CS). Treatment with GAG lyases shows minor effects of CS and discloses a major inhibitory or non-permissive role for HS. The results are discussed in terms of available knowledge on the binding of HSPGs to interative proteins and underscore the importance of understanding glial polysaccharide arrays in addition to its protein complement for a better understanding of neuron-glial interactions.

Limits of Couinaud's liver segment classification: a quantitative computer-based three-dimensional analysis.

Traditionally, liver surgery relies on Couinaud's liver segment classification. As the position and shape of these segments are variable and their borders are hidden within the homogeneous liver mass, the accuracy of segment identification methods needs computer-aided reevaluation. The segmental liver anatomy of 23 patients receiving diagnostic helical CT scans because of suspected intrahepatic lesion was analyzed with the aid of a computer-based operation-planning system. We compared the standard Couinaud classification, which depends particularly on the main stems of portal and hepatic veins, with a method that calculates the segment borders by analyzing the complete portal venous tree. Volume, shape, and position of the liver segments found by each method were compared. With reference to the portal vein-based method, segmental volumes were overestimated by the classic Couinaud method by up to 24% and underestimated to 13%. Volumes of Couinaud segments 4a, 7, and 8 were generally larger compared with those obtained by the portal vein-based method, whereas segments 3 and 6 were smaller. Gross variations were found in segments 5, 7, and 8. When shape and position were considered, poor correlation was found for five segments (median kappa = 0.35-0.45). Only segments 2, 7, and 8 had kappa values clearly above 0.45 in the majority of cases. The plane that divides the two hemilivers along the middle hepatic vein and the border between the left sector (segments 2 and 3) and the medial sector (4a and 4b) were found in both methods with very good conformity (kappa > 0.75). Couinaud's method of dividing the liver into eight autonomous liver segments has to be accepted as a good approximation. Nevertheless, the volume, position, and shape of these segments and their segmental borders show significant variability.

The Neural Correlates of Moral Sensitivity: A Functional Magnetic Resonance Imaging Investigation of Basic and Moral Emotions

Humans are endowed with a natural sense of fairness that permeates social perceptions and interactions. This moral stance is so ubiquitous that we may not notice it as a fundamental component of daily decision making and in the workings of many legal, political, and social systems. Emotion plays a pivotal role in moral experience by assigning human values to events, objects, and actions. Although the brain correlates of basic emotions have been explored, the neural organization of “moral emotions” in the human brain remains poorly understood. Using functional magnetic resonance imaging and a passive visual task, we show that both basic and moral emotions activate the amygdala, thalamus, and upper midbrain. The orbital and medial prefrontal cortex and the superior temporal sulcus are also recruited by viewing scenes evocative of moral emotions. Our results indicate that the orbital and medial sectors of the prefrontal cortex and the superior temporal sulcus region, which are critical regions for social behavior and perception, play a central role in moral appraisals. We suggest that the automatic tagging of ordinary social events with moral values may be an important mechanism for implicit social behaviors in humans.

Organization of corticostriatal projections from the vibrissal representations in the primary motor and somatosensory cortical areas of rodents.

To characterize corticostriatal projections from rodent sensorimotor cortex, the anterograde tracers biotinylated dextran amine (BDA) and fluororuby (FR) were injected into the whisker representations of the primary motor (MI) and somatosensory (SI) cortices. Reconstructions of labeled terminals and their beaded varicosities in the neostriatum and thalamus were analyzed quantitatively to determine the degree of labeled overlap in both of these subcortical structures. Corticostriatal projections from the vibrissal representation in MI were more extensive than corresponding projections from SI. Both cortical areas sent dense projections to the dorsolateral neostriatum, but the MI vibrissal representation also projected to regions located more rostrally and medially. Despite these differences, both MI and SI projected to overlapping parts of the dorsolateral neostriatum. Tracer injections in both cortical areas also produced dense anterograde and retrograde labeling in the medial sector of the posterior complex of the thalamus (POm). Because POm is somatotopically organized and has reciprocal connections with both SI and MI cortices, the amount of labeled overlap in POm was used to indicate whether the tracers were injected into corresponding whisker representations of MI and SI. We found that the proportion of labeled overlap in the neostriatum was highly correlated with the amount of labeled overlap in POm. These results indicate that the rodent neostriatum receives convergent projections from corresponding regions in MI and SI cortex. Furthermore, the thalamocortical projections of the POm indicate that it may modulate corticostriatal outputs from corresponding representations in MI and SI.

Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans.

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and beta-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted approximately 2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of beta-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth.

Superior colliculus projections to midline and intralaminar thalamic nuclei of the rat.

The superior colliculus (SC) projections to the midline and intralaminar thalamic nuclei were examined in the rat. The retrograde tracer cholera toxin beta (CTb) was injected into one of the midline thalamic nuclei-paraventricular, intermediodorsal, rhomboid, reuniens, submedius, mediodorsal, paratenial, anteroventral, caudal ventromedial, or parvicellular part of the ventral posteriomedial nucleus-or into one of the intralaminar thalamic nuclei-medial parafascicular, lateral parafascicular, central medial, paracentral, oval paracentral, or central lateral nucleus. After 10-14 days, the brains from these animals were processed histochemically, and the retrogradely labeled neurons in the SC were mapped. The lateral sector of the intermediate gray and white layers of the SC send axonal projections to the medial and lateral parafascicular, central lateral, paracentral, central medial, rhomboid, reuniens, and submedius nuclei. The medial sector of the intermediate and deep SC layers project to the parafascicular and central lateral thalamic nuclei. The paraventricular thalamic nucleus is innervated almost exclusively by the medial sectors of the deep SC layers. The superficial gray and optic layers of the SC do not project to any of these thalamic areas. The discussion focuses on the role these SC-thalamic inputs may have on forebrain circuits controlling orienting and defense (i.e., fight-or-flight) reactions.

Tomografía SPECT con F18-fluorodeoxiglucosa en infarto reciente del miocardio.: Caso clínico

We report a 50-year-old woman with a recent myocardial infarction in whom a myocardial perfusion single photon emission computed tomography (SPECT) with Thallium201 was done simultaneously with a F18-fluorodeoxyglucose (FDG) SPECT to study glucose metabolism. Myocardial infarction was located in the anteroseptal and apical regions and an echocardiography, done at the second day of evolution, showed a septo-apical hypokinesia. On the tenth day, a coronary angiography showed a critical lesion of the anterior descending coronary artery and an angioplasty with stent placement was performed on the next day. On the twelfth day, a resting, redistribution 201Tl SPECT to study viability and a FDG-SPECT with a dual head high-energy collimator camera were done. Images, acquired 45 min after injection, were analyzed visually. In anterior and medial apical sectors, discordance between flux and metabolism, considered a classical mismatch, was observed. Echocardiographic hypokinesia disappeared three month after revascularization.

The anatomical connections of the macaque monkey orbitofrontal cortex. A review.

The orbitofrontal cortex (OfC) is a heterogeneous prefrontal sector selectively connected with a wide constellation of other prefrontal, limbic, sensory and premotor areas. Among the limbic cortical connections, the ones with the hippocampus and parahippocampal cortex are particularly salient. Sensory cortices connected with the OfC include areas involved in olfactory, gustatory, somatosensory, auditory and visual processing. Subcortical structures with prominent OfC connections include the amygdala, numerous thalamic nuclei, the striatum, hypothalamus, periaqueductal gray matter, and biochemically specific cell groups in the basal forebrain and brainstem. Architectonic and connectional evidence supports parcellation of the OfC. The rostrally placed isocortical sector is mainly connected with isocortical areas, including sensory areas of the auditory, somatic and visual modalities, whereas the caudal non-isocortical sector is principally connected with non-isocortical areas, and, in the sensory domain, with olfactory and gustatory areas. The connections of the isocortical and non-isocortical orbital sectors with the amygdala, thalamus, striatum, hypothalamus and periaqueductal gray matter are also specific. The medial sector of the OfC is selectively connected with the hippocampus, posterior parahippocampal cortex, posterior cingulate and retrosplenial areas, and area prostriata, while the lateral orbitofrontal sector is the most heavily connected with sensory areas of the gustatory, somatic and visual modalities, with premotor regions, and with the amygdala.

An Inhibitory Interface Gates Impulse Traffic between the Input and Output Stations of the Amygdala

The central amygdaloid nucleus projects to brainstem and hypothalamic nuclei mediating fear responses and receives convergent sensory inputs from the basolateral amygdaloid complex. However, interposed between the basolateral complex and central nucleus is a string of interconnected GABAergic cell clusters, the intercalated cell masses. Here, we analyzed how intercalated neurons influence impulse traffic between the basolateral complex and central nucleus using whole-cell recordings, microstimulation, and local application of glutamate receptor antagonists in brain slices. Our results suggest that intercalated neurons receive glutamatergic inputs from the basolateral complex and generate feedforward inhibition in neurons of the central nucleus. As the position of the recording site was shifted medially, intercalated cells projected to gradually more medial sectors of the central nucleus and were maximally responsive to progressively more medial stimulation sites in the basolateral complex. Thus, there is a lateromedial correspondence between the position of intercalated cells, their projection site in the central nucleus, and the source of their excitatory afferents in the basolateral complex. In addition, basolateral stimulation sites eliciting maximal excitatory responses in intercalated neurons were flanked laterally by sites eliciting prevalently inhibitory responses via the activation of intercalated cells located more laterally. As a result, the feedforward inhibition generated by intercalated neurons and, indirectly, the amplitude of the responses of central neurons could be increased or decreased depending on which combination of amygdala nuclei are activated and in what sequence. Thus, the output of the central nucleus depends not only on the nature and intensity of sensory inputs but also on their timing and origin.

Exacerbation of cortical and hippocampal CA1 damage due to posttraumatic hypoxia following moderate fluid-percussion brain injury in rats.

Patients with head injuries often experience respiratory distress that results in a secondary hypoxic insult. The present experiment was designed to assess the histopathological consequences of a secondary hypoxic insult by using an established rodent model of traumatic brain injury (TBI). Intubated anesthetized rats were subjected to moderate (1.94-2.18 atm) parasagittal fluid-percussion injury (FPI) to the brain. Following the TBI, the animals were maintained for 30 minutes by using either hypoxic (TBI-HY group, nine animals) or normoxic (TBI-NO, 10 animals) gas levels. Sham-operated animals also underwent all manipulations except for the FPI (sham-HY group, seven animals; and sham-NO group, seven animals). Three days after TBI the rats were killed, and quantitative histopathological evaluation was undertaken. Cortical contusion volumes were dramatically increased in the TBI-HY group compared with the TBI-NO group (p < 0.03). Qualitative assessment of cortical and subcortical structures demonstrated significant damage within the hippocampal areas, CA1 and CA2, of TBI-HY animals compared with the TBI-NO animals (both p < 0.03). There was also a significant increase in the frequency of damaged neuronal profiles within the middle and medial sectors of the CA1 hippocampus (p < 0.03) due to the hypoxic insult. The results of this study demonstrate that a secondary hypoxic insult following parasagittal FPI exacerbates contusion and neuronal pathological conditions. These findings emphasize the need to control for secondary hypoxic insults after experimental and human head injury.

Diversity of connections of the temporal neocortex with amygdaloid nuclei in the dog (Canis familiaris).

Reciprocal connections of amygdaloid nuclei with the temporal neocortex in the dog were investigated. Injections of fluorescent tracers and BDA into particular temporal areas were made in eleven dogs. The topographical arrangement of connections and variations in their density differentiate the temporal neocortex in the dog into a few regions. Among them, the cortex involving the anterior part of the ectosylvian gyrus did not send any amygdalopetal projection. The middle ectosylvian, dorsal zone of the posterior ectosylvian and the anterior part of the Sylvian gyrus were weakly connected with the amygdala. The cortical region involving the ventral zone of the posterior ectosylvian and composite posterior areas, as well as posterior Sylvian gyrus, was characterized by profuse connections with the amygdaloid complex. Cortico-amygdaloid connections originate in the wide cortical area of the auditory cortex of the middle and dorsal part of the posterior ectosylvian gyrus as well as in the auditory association cortex located in the ventral ectosylvian, composite posterior and posterior Sylvian gyri. The connections showed a dorso-ventral gradient of increasing density, in the direction of association fields. The most substantial projection taking rise from the ectosylvian posterior and posterior composite gyri terminated preferentially in the pericapsular sector of the lateral amygdaloid nucleus and, to a lesser degree, in its medial sector. Terminals of connections originating in the Sylvian gyrus occupied preferentially the intermediate part of the lateral nucleus, slightly more medially than that from the ectosylvian and posterior composite areas. Additionally, axonal terminals derived from the composite posterior and Sylvian posterior areas were observed in the basal parvocellular and magnocellular nuclei. Neocortical projections were reciprocated by amygdalofugal connections with two exceptions: the basal magnocellular nucleus was distinguished by a substantial amygdalofugal projection to the temporal neocortex focused on the dorsal Sylvian gyrus, and the central nucleus of the amygdala, in contrast, received an exclusively corticofugal projection.

Corticothalamic connections of extrastriate visual areas in rhesus monkeys

Corticothalamic connections of extrastriate visual areas were studied by using the autoradiographic anterograde tracing technique. The results show that the medial extrastriate region above the calcarine sulcus projects mainly to the lateral pulvinar (PL), medial pulvinar (PM), and lateral posterior (LP) nuclei. In addition, the dorsal portion of the medial region has connections to the lateral dorsal (LD) as well as to intralaminar nuclei. The dorsolateral extrastriate region projects strongly to the PL and LP nuclei, to the PM and inferior pulvinar (PI) nuclei, and to the LD and intralaminar nuclei. The lateral extrastriate region above the inferior occipital sulcus (IOS) has strong connections to both the PL and PI nuclei and has minor projections to the PM and oral pulvinar nuclei. The ventrolateral extrastriate region below the IOS projects mainly to the PI nucleus and to the caudal portion of the PL nucleus and has some projections to the PM nucleus. The ventromedial extrastriate region medial to the occipitotemporal sulcus has strong connections with the ventral and medial sectors of the PI nucleus. This region also projects to the caudal portion of the PL nucleus and has minor connections to the LP nucleus. Finally, the annectant gyrus projects to the PL nucleus and to the rostral portion of the PI nucleus and has minor connections to the PM nucleus. Thus, the medial and dorsolateral extrastriate regions are related mainly to the PL and LP nuclei as well as to intralaminar nuclei. In contrast, the ventrolateral and ventromedial regions are connected strongly with the PI nucleus. This connectional organization appears to reflect functional differentiation at the cortical level. J. Comp. Neurol. 378:562–585, 1997. © 1997 Wiley-Liss, Inc.