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PubMedDate not supplied

Soft tissue restraints to lateral patellar translation in the human knee.

The purpose of this investigation was to identify and quantify the soft tissue restraints, both medially and laterally, to lateral patellar translation. These restraints to lateral patellar translation at 20 degrees of knee flexion were tested biomechanically on a universal testing instrument in nine fresh-frozen cadaveric knees. After preconditioning the tissues, the patella of each intact knee was translated laterally to a distance at which a force of 200 N was recorded. This distance was used to translate the patella for the remaining structures to be sectioned. The contribution of each structure to the total restraining force was determined as the percent of the force to restrain the intact specimen by sectioning the restraints in a predetermined order. The contribution of each structure to the restraining force was defined as the difference between the restraining force before and after its sectioning. The medial patellofemoral ligament was found to be the primary restraint to lateral patellar translation at 20 degrees of flexion, contributing 60% of the total restraining force. The medial patellomeniscal ligament contributed 13% of the total force, and the lateral retinaculum contributed 10%. The medial patellotibial ligament and superficial fibers of the medial retinaculum were not functionally important in preventing lateral translation. The previously unrecognized contribution of the lateral retinaculum as a restraint to lateral patellar translation may shed new light on the failures of isolated lateral release for acute lateral dislocation of the patella.

Adult↗
PubMed2006

The use of standing lateral tibial-calcaneal angle as a quantitative measurement of Achilles tendon contracture in adult acquired flatfoot.

BACKGROUND: To quantitate the association of Achilles tendon contracture (ATC) with adult acquired flatfoot, the authors hypothesized that the standing lateral tibial-calcaneal angle increases because of ATC. METHODS: The standing lateral tibial-calcaneal angle, talo-first metatarsal angle, lateral talocalcaneal angle, lateral standing medial cuneiform, arch height, and anteroposterior talonavicular coverage angle were measured in 21 patients (25 feet) with clinical diagnoses of ATC and adult acquired flatfoot (AAF) and compared to the same measurements in a control group of 15 patients (30 feet) with no foot deformities or previous foot surgeries. RESULTS: The mean lateral tibial-calcaneal angle in the control group was 64.43 degrees and in the AAF group 71.24 degrees (p < 0.001). The mean lateral talo-first metatarsal angle in the control group was 11.77 degrees, and in the AAF group with ATC it was 25.80 degrees (p < 0.001). The mean arch height in the control group was 17.90 mm and in the AAF group, 8.48 mm (p < 0.001). In the ATC and AAF group an increasing standing lateral tibial-calcaneal angle was correlated with a decreasing lateral talo-calcaneal angle (p = 0.044), and a decreasing arch height was correlated to an increasing lateral talo-first metatarsal angle (p < 0.001). CONCLUSION: Adults with flatfeet and Achilles tendon contracture may have a statistically significant increase in the standing lateral tibial-calcaneal angle. This angle may be a reproducible measure of ATC. An increase in the standing lateral tibial-calcaneal angle may confirm and quantitate the clinical diagnosis of Achilles tendon contracture. Further studies with more patients are needed.

Achilles Tendon↗
PubMed1997

Test-retest reliability of the lateral step-up test in young adult healthy subjects.

The lateral step-up test is often utilized by clinicians to assess lower extremity performance capabilities. Reliability of the lateral step-up test, however, is not available. Therefore, the purpose of this study was to determine the test-retest reliability of a 15-sec and a 50-repetition lateral step-up test on a .15-m (6-inch) and .2-m (8-inch) step. For each of the 15-sec lateral step-up tests, subjects were asked to perform as many repetitions as possible during the 15-sec time frame, while for each of the 50-repetition lateral step-up tests, subjects were asked to perform 50 repetitions as quickly as possible. Eighteen healthy subjects were studied. Data were analyzed through a repeated measures analysis of variance, intraclass correlation coefficients (ICC) (2, 1), and standard errors of measurement. The ICC values were .90 and .94 for the .15-m and .2-m 15-sec lateral step-up tests and .91 and .96 for the .15-m and .2-m 50-repetition lateral step-up tests, respectively, revealing test-retest reliability to be high for each of the tests. Significant differences, however, were noted between the testing days for each of the 50-repetition lateral step-up tests, indicating that the measures may not be stable. No significant differences were seen between testing days for either of the 15-sec lateral step-up tests. While the results support the use of each of the 15-sec lateral step-up tests as reliable, stable measures of lower extremity performance, caution should be used when interpreting the results of either of the 50-repetition lateral step-up tests if used as demonstrated in this study.

Adult↗
PubMed2003

Cervical stability with lateral mass plating: unicortical versus bicortical screw purchase.

STUDY DESIGN: A biomechanical study using human cadaveric cervical spines was conducted. OBJECTIVE: To determine whether the cervical stability achieved with lateral mass fixation using unicortical screw purchase is comparable with that obtained with lateral mass fixation using bicortical screw purchase. SUMMARY OF BACKGROUND DATA: Cervical lateral mass fixation has traditionally required bicortical screw fixation, which is associated with potential injury to the vertebral vessels and cervical nerve roots. Unicortical fixation eliminates these possible complications. Limited stability studies suggest that unicortical fixation in the lateral masses provides stability comparable with that of bicortical fixation. However, no comprehensive biomechanical study has compared the cervical stability between bicortical and unicortical lateral mass fixations. METHODS: A total of 11 human cadaveric cervical spinal sections between C3 and C5 were tested in flexion-extension, torsion, and lateral bending modes, both with and without laminectomy, on an MTS machine. The lateral masses were plated and tested with bicortical screws in all 11 specimens. Long (14 mm) unicortical screws were used in 8, and short (10 mm) screws were used in 6 of the 11 specimens. Displacement then was determined in millimeters (of flexion-extension and lateral bending) and degrees (of torsion) for each value of applied torque (0.45, 0.9, 1.35, 1.8 Nm). Two-way analysis of variance using unequal data sets then was applied. RESULTS: Analysis demonstrates that bicortical constructs were, on the average, stiffer than unicortical constructs in most bending modes. No significant differences were found, however, between bicortical constructs and long unicortical constructs without laminectomy. In the presence of a destabilizing laminectomy, a difference was found in the lateral bending mode. More differences were found between bicortical and short unicortical constructs both with and without laminectomy. CONCLUSIONS: Cervical lateral mass fixation with "long" (up to but not through the anterior lateral mass cortex) unicortical Magerl screws may provide an acceptable and safe alternative to bicortical screw fixation.

Biomechanical Phenomena↗
PubMed1989

Interlaminar and lateral excitatory amino acid connections in the striate cortex of monkey.

The intrinsic excitatory amino acid pathways within the striate cortex of monkeys were studied by autoradiographic detection of retrogradely labeled somata following microinjections of D-3H-aspartate (D-3H-Asp) into different layers. The labeled amino acid was selectively accumulated by subpopulations of neurons and, to a small extent, by glial cells, the latter mainly in the supragranular layers. Immunocytochemical detection of neurons containing GABA showed that, apart from a few cells exclusively in layer I, GABAergic neurons do not accumulate D-3H-Asp. Several lines of evidence suggest that D-3H-Asp uptake occurred only at nerve terminals; thus, the pattern of perikaryal labeling allowed the delineation of interlaminar and lateral projections. Neurons in layer I probably project laterally, and layer I receives wide-ranging projections from layer IVB and layer V from cells up to 1300 microns laterally. Some neurons in layer II send a focused projection to lower layer VI. Some neurons in layers II/III project up to 1 mm laterally within their own layer, but relatively few neurons can be labeled in these projections. Similarly, in layers II/III few neurons can be retrogradely labeled from layers V and upper VI, and this projection is organized such that cells closer to the pia project deeper in layer V/VI. The connections of layer IVA could not be revealed separately because of the difficulty of confining injections to this thin sublamina. Neurons in layer IVB project up to 1300 microns within IVB itself. A small number of cells from IVB also project to layers III, IVC-alpha, V, and VI with much more restricted lateral spread. Neurons in upper IVC-alpha send axons to layer IVB with at least 600-800 microns lateral spread. Neurons in lower IVC-alpha/upper IVC-beta project to layer III with at least 300-500 microns lateral spread. The bottom 50-80 microns of layer IVC-beta contains neurons with a very focused projection, apparently exclusively to the layer III/IVA border region. Both layers IVC alpha and beta have rich connections within themselves, the beta sublayer having more restricted lateral connections. Some neurons in layer IVC-beta give a laterally restricted small input to layers IVC-alpha and IVB. Both IVC-alpha and -beta project to layers V and VI, and these projections are spread at least 400 microns laterally. Neurons in layer V project to all layers, but the projection to layers I-III and within layer V itself spread much further laterally than the projections to layers IV and VI.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1995

The role of the lateral line in active drag reduction by clupeoid fishes.

The lateral-line canals, confined in clupeoid fishes to the two sides of the head, are centred on the two lateral recesses, where thin membranes separate the sea water in the lateral-line system from another fluid (perilymph) in that subcerebral canal which passes through the head between the two lateral recesses. Any pressure difference between the recesses can accelerate fluid in the subcerebral canal, but it is only the effective acceleration of that fluid (i.e. relative to the lateral acceleration of the head) which can tend to generate motions--sensed by neuromasts--in lateral-line canals near the lateral recesses. Furthermore, it is the same effective lateral acceleration (relative to that of the head) that is experienced by water in the thin boundary layer on the surface of the head, where it tends to generate 'crossflows' that may act to increase hydrodynamic resistance (i.e. drag) to the fish's normal swimming movements. These regular swimming movements produce oscillatory sideslip of the fish's head which, by itself, would give such substantial values to the effective acceleration that lateral-line sensors near the lateral recesses would be saturated during normal swimming movements. Any such permanent state of saturation seems rather unlikely. An alternative hypothesis is that the fish actively produces an oscillatory turning of the head, controlled by the sensory output of those same neuromasts in such a way that this output is kept to a minimum. Then that effective pressure difference, which is responsible for the effective lateral acceleration both of perilymph in the subcerebral canal and of sea water in the boundary layer on the head, would be minimised--with advantageous drag-reduction consequences. In order to test this hypothesis, a detailed hydrodynamic analysis was carried out. It suggested that, in order to minimise the effective pressure difference, the yaw angle (in radians) of the fish's head would need to be kept in phase with the sideslip velocity, their magnitudes being in a ratio of about 0.87 U-1 (where U is the swimming speed). Experiments on a swimming clupeoid fish confirmed these conclusions, both about phases and about magnitudes. By contrast, a purely passive response of the head to oscillatory sideforce on the caudal fin would be expected to give the yaw angle a substantial lag behind sideslip, along with a ratio of magnitudes much smaller than 0.87 U-1. Thus, the experiments seems to support the hypothesis regarding active control of drag reduction.

Animals↗
PubMed2006

Hip and knee joint rotations differ between patients with medial and lateral knee osteoarthritis: gait analysis of 30 patients and 15 controls.

The motions and moments in the hip and knee in female patients on the waiting list for knee prosthesis surgery with medial (n = 15) or lateral (n = 15) osteoarthritis (OA) were compared with a control group (n = 15). We hypothesized that not only the kinematics and kinetics of the knee but also of the hip would differ between patients the medial and lateral groups. At midstance, patients with lateral OA showed slightly (2 degrees) more maximal (peak) adduction (p = 0.015) of the hip joint and patients with medial OA had 7 degrees more abduction (p < 0.001) than did controls. In patients with lateral OA, the femur was positioned in about 7 degrees more maximum external rotation (p = 0.001), but femur position did not differ between medial OA and controls (p > or = 0.8). There was a tendency to higher internal hip rotation moment in lateral OA compared to controls (p = 0.021). The maximum values of the internal knee abduction moments were 52% higher in medial OA (p = 0.005) and 63% lower in lateral OA (p < 0.001) compared to controls. Cases with medial OA had 9 degrees more, whereas those with lateral OA had 6 degrees less external tibial rotation than controls (medial vs. lateral OA, p = 0.001). We found an association between presence of lateral OA of the knee and the biomechanics of the hip joint. It remains to be evaluated if the changed biomechanics of the hip joint is a reason for development of lateral OA or an observation that is a result of this disease.

Aged↗
PubMed1996

The degree of lateralization of paw usage (handedness) in the mouse is defined by three major phenotypes.

Lateralization of paw usage in the laboratory mouse may be a useful model system in which to assess the genetic and developmental cause of asymmetry of hand usage. With a set number of paw reaches from a centrally placed food tube, individual mice from an inbred strain will exhibit a reliable number of left and right paw reaches. For a single inbred strain, there are approximately equal numbers of left-pawed and right-pawed mice, but strain differences have been reported in the degree of lateralization of paw preference. We reported a preliminary strain survey in which the strains appeared to fall into two groups of highly lateralized and weakly lateralized paw preference (Biddle et al., 1993). We review here our expanded survey of genetically different strains and stocks of the laboratory mouse, including different species and subspecies. The major genetic trait is the degree of lateralization of paw preference and the strain differences appear to fall into three major classes of highly lateralized, weakly lateralized, and ambilateral preference. The trait exhibits both additivity and dominance in preliminary reciprocal crosses, depending on which strain pairs are used. The wide difference between strains that have highly lateralized and ambilateral paw preference suggests specific genetic tools that could be used to begin a genetic dissection of the causes of this trait. Preliminary assessment of the size of the corpus callosum in three strains with significantly different degrees of lateralization suggests that genetically determined deficiencies and absence of this structure are not the direct cause of the strain differences in the trait of degree of lateralization. In the expanded survey, some strains appear to exhibit a directional deviation from equal numbers of mice with left and right paw usage. Therefore, direction of paw usage may not be a genetically neutral trait, but replicate assessments and genetic tests are needed to confirm this.

Animals↗
PubMed2005

Lateralization of event-related beta desynchronization in the EEG during pre-cued reaction time tasks.

OBJECTIVE: Here, we investigate whether the event-related desynchronization (ERD) of spectral components of the cortical EEG in the beta (13-30 Hz) frequency range may, in part, index motor selection processes. Specifically, we sought evidence for a contralaterally dominant component of the beta ERD that is limited to trials in which motor selection is possible prior to any imperative cue to move, with attendant behavioural advantage. METHODS: We measured reaction time and assessed the lateralization of beta ERD in 12 healthy volunteers as they performed pre-cued choice reaction time tasks, in which warning S1 cues were either fully predictive about the laterality of a subsequent imperative S2 signal or provided no laterality information. We calculated 'lateralized ERD index' (LERDI), a parallel measure to the lateralized readiness potential in the time domain. RESULTS: Trials with 100% S1-S2 congruency produced significantly shorter reaction times than trials with 50% S1-S2 congruency, where laterality information was unreliable. Beta LERDI indicated significantly greater lateralisation of the ERD in the warning-go interval and of event-related synchronization (ERS) following movement in the 100% condition than in the 50% condition. The lateralization of the beta ERD with respect to hand persisted, even when subjects were instructed to make movements of opposite laterality to those prompted. CONCLUSIONS: Lateralized EEG changes occur in the beta band in the S1-S2 interval prior to movement, but only when informative warning cues allow early motor selection, as suggested by the shortening of reaction time. Furthermore, the enhanced contralateral ERS with 100% S1-S2 congruency suggests that this phenomenon is at least partly independent of afferent feedback, as the same movement was made in the 100 and 50% conditions. SIGNIFICANCE: Lateralized suppression of beta power prior to externally generated movements is associated with motor selection.

Adult↗
PubMed1998

The origins of cerebral asymmetry: a review of evidence of behavioural and brain lateralization in fishes, reptiles and amphibians.

Early evidence for lateralization at a population and/or individual level in 'lower' vertebrates is reviewed. The lateralities include structural asymmetries in the epithalamus of several species of fish and amphibians, asymmetries in the location of both eyes on the same side of the head and of the dorsal/ventral crossing at optic-chiasma in flatfish, asymmetries in copulatory organs of several species of fishes, asymmetries in lung size and direction of coiling in reptiles, and asymmetrical distribution of scarring in whitefish. More recent data on functional lateralization at population level in lower vertebrates are also reviewed. These include: lateral asymmetries in the direction of turning during escape behaviour and in eye use in poeciliid fish; lateralization of pectoral stridulation sounds in catfish; neural lateralization for control of vocalization in the frogs; pawedness in toads; lateralization of courtship behaviour in newts; and lateralization of aggressive responses in lizards. Several cases of behavioural asymmetries at the individual level are also described, and possible relationships between lateralization at the individual level and fluctuating asymmetries arising from reduced heterozygosity are discussed. It is argued that the overall evidence now available supports the hypothesis of an early origin of brain lateralization in vertebrates.

Amphibians↗
PubMed1990

Lateral bias in infant chimpanzees (Pan troglodytes).

This study documents the presence, strength, and direction of lateralization in chimpanzees (Pan troglodytes) over the first 3 months of life. Nursery-reared chimpanzees (7 males and 5 females) were repeatedly assessed on a behavioral scale. Lateral bias was measured for 4 behaviors: hand-to-mouth, hand-to-hand, defensive grasp, and first step. Hand-to-mouth was significantly lateralized for the sample. Eight of the 10 chimpanzees that showed hand-to-mouth used the right hand. Lateral bias for defensive grasp was positively related to lateral bias both of first step and of hand-to-mouth. Lateral bias in hand-to-mouth was inversely related to lateral bias in hand-to-hand. Strength of lateralization increased as chimpanzees matured. These laterality effects in infant chimpanzees were expressed under conditions of emotional arousal. Moreover, degree of laterality may be a predictor of responsivity to stress.

Animals↗
PubMedDate not supplied

Temporal lobectomy and independent bitemporal interictal activity: what degree of lateralization is sufficient?

We attempted to determine whether the degree of lateralization of independent bitemporal interictal spikes and sharp waves (ISSW) is correlated with good results after temporal lobectomy. Three observers independently counted ISSW in the scalp EEGs of 59 candidates for temporal lobectomy to determine the degree of lateralization of ISSW. Interobserver correlation in percentage of lateralization was excellent (r = 0.92). Thirty-one candidates were also evaluated with depth EEG (DEEG). Operative success was graded by the number of seizures reported in the second postoperative year. There was a significant progressive decrease in the number of good operative results as the degree of lateralization of ISSW lessened (p = 0.0142). Ninety-two percent of patients with greater than 90% lateralization had a good surgical outcome, whereas only 50% with less than 90% lateralization had a good outcome. Even when all DEEG-recorded seizures emerged from the side of the lobectomy, patients with greater than 90% lateralization appeared to have better outcomes than patients with less than 90% lateralization. We conclude that greater than 90% lateralization of temporal ISSW is associated with good surgical outcome, and DEEG may not be necessary in these patients. Less than 90% lateralization is associated with poor surgical outcome and the additional information provided by DEEG may be especially useful in such patients.

Adolescent↗
PubMed2002

Spike-dependent GABA inputs to bipolar cell axon terminals contribute to lateral inhibition of retinal ganglion cells.

The inhibitory surround signal in retinal ganglion cells is usually attributed to lateral horizontal cell signaling in the outer plexiform layer (OPL). However, recent evidence suggests that lateral inhibition at the inner plexiform layer (IPL) also contributes to the ganglion cell receptive field surround. Although amacrine cell input to ganglion cells mediates a component of this lateral inhibition, it is not known if presynaptic inhibition to bipolar cell terminals also contributes to surround signaling. We investigated the role of presynaptic inhibition by recording from bipolar cells in the salamander retinal slice. TTX reduced light-evoked GABAergic inhibitory postsynaptic currents (IPSCs) in bipolar cells, indicating that presynaptic pathways mediate lateral inhibition in the IPL. Photoreceptor and bipolar cell synaptic transmission were unaffected by TTX, indicating that its main effect was in the IPL. To rule out indirect actions of TTX, we bypassed lateral signaling in the outer retina by either electrically stimulating bipolar cells or by puffing kainate (KA) directly onto amacrine cell processes lateral to the recorded cell. In bipolar and ganglion cells, TTX suppressed laterally evoked IPSCs, demonstrating that both pre- and postsynaptic lateral signaling in the IPL depended on action potentials. By contrast, locally evoked IPSCs in both cell types were only weakly suppressed by TTX, indicating that local inhibition was not as dependent on action potentials. Our results show a TTX-sensitive lateral inhibitory input to bipolar cell terminals, which acts in concert with direct lateral inhibition to give rise to the GABAergic surround in ganglion cells.

Action Potentials↗
PubMed1998

Clinical seizure lateralization in mesial temporal lobe epilepsy: differences between patients with unitemporal and bitemporal interictal spikes.

OBJECTIVE: To compare the reliability of clinical seizure lateralization in temporal lobe epilepsy patients with unitemporal and bitemporal independent interictal spikes and unilateral hippocampal atrophy or sclerosis (HA/HS) on MRI scan. PATIENTS AND METHODS: We studied 11 patients with unitemporal and 10 patients with bitemporal interictal spikes. We calculated a spike ratio by dividing the number of spikes ipsilateral to the side of HA/HS by those occurring contralaterally. RESULTS: Clinical seizure lateralization was correct, i.e., ipsilateral to the side of HA/HS, significantly more often in the unitemporal group. Spike ratios were significantly higher in seizures that were lateralized correctly as compared with both incorrectly and nonlateralized seizures. Within the individual patients, a significant positive correlation between spike ratios and the proportion of correctly lateralized seizures was found. We identified three categories of symptoms according to lateralization accuracy. Category 1 symptoms (version, postictal paresis, and early ictal vomiting/retching) lateralized to the side of HA/HS in 100% of patients in the uni- and bitemporal groups. Category 2 symptoms (dystonic posturing, mouth deviation, postictal dysnomia/dysphasia, and ictal speech) provided a 100% correct lateralization in the unitemporal but not in the bitemporal patients. Category 3 symptoms (nonversive early head turning and unilateral upper extremity automatisms) yielded erroneous lateralization in both patient groups. CONCLUSIONS: We conclude that reliable clinical seizure lateralization in mesial temporal lobe epilepsy can only be achieved in patients with unitemporal interictal spikes, whereas clinical lateralization in patients with bitemporal spikes must be viewed cautiously.

Adult↗
PubMed2005

[Lateralized distribution of motor areas involved in voluntary movement].

OBJECTIVE: To investigate the brain functional laterality in motor areas during motor execution systematically. METHODS: Functional magnetic resonance imaging (fMRI) was employed combined with right hand sequential finger movement task to investigate brain activation pattern and laterality in 8 right-handed subjects. 3dDeconvolve program of AFNI was used to estimate the hemodynamic response function and to generate activation maps. Then the laterality index (LI) was calculated and tested statistically. RESULT: All motor areas including the areas which were previously considered to be engage in movement preparation only were activated in movement execution. In the activation map, it appeared left lateralization in cerebra and right lateralization in cerebella. After further statistical test, it was found that in primary motor area (M1), supplementary motor area (SMA) and posterior parietal cortex (PPC), there were left lateralization. While in premotor cortex (PMC), cingulate gyrus and basal ganglia (BG), the lateralization tendency was not obvious. The activation in cerebella is characterized with right lateralization. CONCLUSION: Though there are tiny differences among subjects, most of the motor areas appear lateralized activation. Past studies only observed laterality in several motor areas. It may be due to the difficulty of the task or the experimental design.

Adult↗
PubMed1998

Organization of the intrinsic connections of the monkey amygdaloid complex: projections originating in the lateral nucleus.

We have used the anterograde tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L) to study the intrinsic projections of the lateral nucleus of the Macaca fascicularis monkey amygdaloid complex. A reanalysis of the monkey lateral nucleus indicated that there are at least four distinct cytoarchitectonic divisions: dorsal, dorsal intermediate, ventral intermediate, and ventral. The major projections within the lateral nucleus originate in the dorsal, dorsal intermediate, and ventral intermediate divisions and terminate in the ventral division. The ventral division also projects to itself but does not project significantly to the other divisions of the lateral nucleus. Thus, the ventral division appears to be a site of convergence for information entering all other portions of the lateral nucleus. There are substantial regional and topographic differences in the projections from each of the lateral nucleus divisions to other amygdaloid nuclei. The dorsal division projects to all divisions of the basal and accessory basal nuclei, to the periamygdaloid cortex, the nucleus of the lateral olfactory tract, the dorsal division of the amygdalohippocampal area, and the lateral capsular nuclei. The dorsal intermediate division projects to the intermediate and parvicellular divisions of the basal nucleus, to the parvicellular division of the accessory basal nucleus, and to the periamygdaloid cortex. The ventral intermediate division projects to the magnocellular division of the accessory basal nucleus and to the parvicellular division of the basal nucleus. The major projections from the ventral division are directed to the parvicellular division of the basal nucleus, the parvicellular division of the accessory basal nucleus, the medial nucleus, and the periamygdaloid cortex. Projections from all portions of the lateral nucleus to the central nucleus are generally very light. It appears, therefore, that each division of the lateral nucleus originates topographically organized projections to the other amygdaloid areas that terminate in distinct portions of the target regions. The topographic organization of intrinsic amygdaloid projections raises the possibility that serial and parallel sensory processing may take place within the amygdaloid complex.

Amygdala↗
PubMed1983

The acoustic and lateral line nuclei are distinct in the premetamorphic frog, Rana catesbeiana.

The transition from aquatic to terrestrial hearing in the frog occurs during metamorphosis and during the disappearance of the lateral line system. The coincidence in time of these two processes and morphological similarities between the acoustic and lateral line systems has led to the suggestion (Larsell, '34) that the lateral line nuclei are transformed into the acoustic nuclei. The relation between the acoustic and lateral line systems was investigated by studying the distribution of primary afferents, the dendritic patterns of the cells in the primary nuclei, and the development of the nuclei in the premetamorphic bullfrog, Rana catesbeiana. The posterior and anterior lateral line roots distribute to a neuropil located medial to the dorsal medullary nucleus. Horseradish peroxidase (HRP) injections into the contralateral tegmentum fill cells in the periventricular region whose dendrites ramify within the neuropil. These cells constitute the lateral line nuclei. The amphibian and basilar papillary roots of the acoustic system distribute to the more lateral nuclear region. The dendrites of these cells arborize within the nucleus and not in the lateral line neuropil. The dorsal medullary nucleus is, therefore, the acoustic nucleus (AcN). [3H]-thymidine labeling reveals that newly generated cells occupy the AcN within a few hours of their formation throughout the period when anatomical analysis shows the parallel growth and diminution of the lateral line neuropil and nuclei. This study indicates that the lateral line and acoustic systems are morphologically independent at the level of the primary afferents and primary nuclei throughout early development.

Animals↗
PubMed1984

The lateral suprasylvian corticotectal projection in cats.

The projection from the lateral suprasylvian visual areas to the superior colliculus was investigated in cats using both anterograde and retrograde tracing techniques. The retrograde transport of horseradish peroxidase (HRP) or wheat germ agglutinin-HRP (WGA-HRP) from their site of deposit in the superior colliculus indicates that all divisions of the lateral suprasylvian visual areas project to both the superficial and deep layers of the superior colliculus. However, following tracer deposits in the superior colliculus that are confined to the layers below the stratum opticum (deep layers), more neurons are labeled along the lateral bank than along the medial bank of the middle suprasylvian sulcus. Conversely, tracer deposits in the superior colliculus dorsal to and including the stratum opticum label more cells in the medial than the lateral bank. These retrograde experiments also confirm that the visual cortex along the lateral gyrus (areas 17 and 18) projects to the superficial, but apparently not to the deep layers. The visual area in the cortex surrounding the caudal two-thirds of the anterior ectosylvian sulcus projects to the deep, but not to the superficial layers. The laminar and areal patterns of anterograde axon labeling in the superior colliculus were examined after single deposits of 3H-amino acids (autoradiography), HRP, or WGA-HRP in the lateral suprasylvian cortical regions, or combined isotope and WGA-HRP deposits. Axon labeling in the superior colliculus is generally densest in the stratum opticum and extends either dorsally into the superficial layers or ventrally into the intermediate gray layer. Specifically, the anterior divisions of the lateral suprasylvian cortex project primarily to the lateral portion of the superior colliculus, with the projection from the medial bank biased toward the superficial layers and axons from the lateral bank aimed mainly at the intermediate gray layer with some axons even reaching the deepest gray layer of the superior colliculus. Both the posteromedial and posterolateral divisions of the lateral suprasylvian cortex project to more extensive portions of the mediolateral and rostrocaudal dimensions of the superior colliculus than the anterior divisions. However, the posterolateral division projects more heavily to the intermediate gray layer than the posteromedial division; from the latter, axons distribute more superficially in the superior colliculus. Finally, the cortex surrounding the posterior suprasylvian sulcus projects primarily to the medial part of the superficial layers of the superior colliculus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗