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The aim of the present study was to identify synaptic contacts from axons originating in the superior colliculus with thalamic neurons projecting to the lateral nucleus of the amygdala. Axons from the superior colliculus were traced with the anterograde tracers Phaseolus vulgarisleucoagglutinin or the biotinylated and fluorescent dextran amine “Miniruby.” Thalamo‐amygdaloid projection neurons were identified with the retrograde tracer Fluoro‐Gold. Injections of Fluoro‐Gold into the lateral nucleus of the amygdala labeled neurons in nuclei of the posterior thalamus which surround the medial geniculate body, viz. the suprageniculate nucleus, the medial division of the medial geniculate body, the posterior intralaminar nucleus, and the peripeduncular nucleus. Anterogradely labeled axons from the superior colliculus terminated in the same regions of the thalamus. Tecto‐thalamic axons originating from superficial collicular layers were found predominantly in the suprageniculate nucleus, whereas axons from deep collicular layers were detected in equal density in all thalamic nuclei surrounding the medial geniculate body. Double‐labeling experiments revealed an overlap of projection areas in the above‐mentioned thalamic nuclei. Electron microscopy of areas of overlap confirmed synaptic contacts of anterogradely labeled presynaptic profiles originating in the superficial layers of the superior colliculus with retrogradely labeled postsynaptic profiles of thalamo‐amygdaloid projection neurons. These connections may represent a subcortical pathway for visual information transfer to the amygdala. J. Comp. Neurol. 403:158–170, 1999. © 1999 Wiley‐Liss, Inc.

Abstract: Early postnatal application of thyroid hormones to rats results in morphological changes of the septo-hippocampal cholinergic and the hippocampal mossy fiber systems. Modulation in the expression of either neurotrophins and/or their receptors is postulated to be involved in these effects. In a recent study, we showed that, after thyroxine application, the mRNA expression of neurotrophins of the nerve-growth-factor (NGF) family is significantly upregulated both in septum and hippocampus. To test whether the neurotrophin receptors (the low-affinity neurotrophin receptor p75 and the specific high-affinity receptors trkA, trkB, and trkC) were also affected by hormone administration, newborn rats were treated daily with subcutaneous injections of thyroxine until postnatal day 12 (P12) at latest. Control animals received corresponding injections of saline. The pups were sacrificed at defined intervals from P9 to P14. The septal areas and the hippocampi were analyzed using the reverse-transcription polymerase chain reaction (RT-PCR) method for quantification of p75, trkA, trkB, and trkC mRNA levels. Analysis of variance over the total investigation period revealed no significant general increases of the gene expressions of either neurotrophin receptor, neither in the septum nor in the hippocampus, although previous results have shown marked changes in neurotrophin levels. On particular postnatal days, significant upregulation could be observed in hippocampus for trkB and trkC. From these and recent data, we conclude that modulation of neurotrophin expression rather than neurotrophin-receptor expression contributes to the morphological modifications within the hippocampal mossy fiber system and the septo-hippocampal cholinergic system.

The Water-T-Maze was used to investigate the genetically determined apparatus-dependent behavior of mice. Special importance was attached to the mode of inheritance involved. For this purpose we used NMRI, C3H/HeJ, Balb/c, Balb/cN, DBA/2, C57Bl/6 inbred mouse strains, together with their offspring and the F2-hybrids of C3H/HeJ and DBA/2. Furthermore investigations were carried out to examine the effect of the environment on the expression of behavior. After these experiments had proved that there is a predominantly genetic derivation for behavioral expression, a possible relationship between the conditioning effect and the age of the animals was investigated. The animal's age has quantitative effects on the expression of behavior, but it does not lead to any qualitative behavioral changes. Nevertheless early conditioning of the animals apparently manifests itself in long-term memory. On the whole the mode of inheritance in Water-T-Maze learning appears to imply a polygene-dependent model in which clear dominant effects are present, as shown in the results of the F2-generation. No sex-related differences were observed. In general, the results demonstrate a definite involvement of genetic factors in the areas of conditioning and behavior.

The genetic basis of active avoidance learning was investigated with mice as model organisms by means of different test systems such as the Shuttle-Box with light and sound stimulation and the Skinner-Box with light stimulation. Six inbred strains of mice and their offspring (F1) as well as selected second and third generation progenies (F2 and F3 resp.) were used in this study. Furthermore we induced environmental modifications such as embryonic transplants in opposite behavioral phenotypes, crossfoster breeding as well as enriched and impoverished environment. The results enable us to postulate a monogenic inheritance of Shuttle-Box performance with codominant mode. The gene expression could not be disturbed by environmental manipulations. Therefore, the learning in the Shuttle-Box has a very simple genetic background which might underly a multiple allelic system.

A physico-chemical model of a self-maintaining unity or protocell is constructed on the basis of reaction and diffusion processes. The surface motion of the protocell is taken into account explicitly by a so-called Stefan condition, which leads to a nonlinear feedback to the reaction and diffusion processes. The spatio-temporal dynamics in the neighbourhood of the steady states is investigated in the framework of linear stability analysis with the use of an expansion in terms of spherical harmonicsYlm. It is shown that modes with l?2 become successively unstable with increasing nutrient supply. The leading instability with l=2 initiates a process of the nonlinear dynamics which is interpreted as the onset of division. A stabilizing effect of surface tension is also discussed.

In one short-term-experiment and one long-term-experiment spermatogonia of mice and Chinese hamsters were compared for their sensitivity of X-ray induced chromosome aberrations.

Previous investigations in mice revealed the existence of a set of genes that influence variations in hippocampal anatomy as well as variations in behavioral responses to novelty. In particular, a positive genetic correlation was found between the size of the intra- and infrapyramidal mossy fiber (iip-MF) projection and rearing frequency in an open-field. On the basis of these findings, we hypothesized that genetic selection for rearing would entail correlated changes in hippocampal morphology. This was tested in the inbred selection lines SRH (selection for rearing: high) and SRL (selection for rearing: low). As expected, the SRH mice appeared to possess iip-MF terminal fields that were larger than those of the SRL mice. Because the behavioral difference between the two lines is most probably caused by a single genetic unit, these animals represent valuable material for molecular-genetic investigations into the mechanisms that control behavioral and neuroanatomical variation.

To investigate substrain divergence in the highly inbred C3H strain, we studied the C3H/HeJ, C3H/HeJ//Bkl, C3H/He//Han, and C3H/HeJ//Hd strains. The Hd subline differed from the other three in its lower performance on a two-way active-avoidance learning task, larger infra- and intrapyramidal mossy fiber terminal fields, and rejection of skin grafts from other lines. There were no differences among the other three strains. This substrain divergence is explained by differences in animal husbandry techniques.

We studied mouse learning performance in a water-maze task in order to explore the relations between heritable structural variation in the hippocampus and spatial learning abilities. Based on previous findings we hypothesized a relation between spatial learning abilities and the size of the intra- and infrapyramidal mossy fiber (iip-MF) terminal field. Factor analysis revealed that learning in this water maze has two components: one related to apparatus-induced activity and one related to maze-learning ability. The size of the iip-MF terminal field covaried negatively with the activity-related component but positively with the spatial-learning component. These findings are in agreement with previous results obtained for shuttle-box learning.

A classical cross-breeding study involving the inbred mouse strains DBA/2 and C3H/HeJ revealed a rather complex mode of inheritance for the following hippocampal variables: size of stratum pyramidale, number of supra-, intra- and infrapyramidal mossy fiber synapses, and the size of terminal fields receiving entorhinal input. A polygenic mode of inheritance was inferred for these phenotypes. For the size of the regio inferior a model containing additive genetic effects only was sufficient to explain the variation between generations. The strain difference may be caused by one genetic factor only. In agreement with previous experiments a strong negative correlation between the number of intra- and infrapyramidal mossy fiber synapses and shuttle-box avoidance performance was found in the genetically heterogeneous F2 population.

Simulander is a feedforward neural network simulating the orientation movement of salamanders. The orientation movement is part of the prey capture behavior; it is performed with the head alone. Simulander is a network which consists of 300 neurons incorporating several cytoarchitectonic and electrophysiological features of the salamander brain. The network is trained by means of an evolution strategy. Although only 100 tectum neurons with fairly large receptive fields are used (“coarse coding”), Simulander is able to localize an irregularly moving prey precisely. It is demonstrated that large receptive field neurons are important for successful prey localization. The removal of a model tectum hemisphere leads to a network which accounts for investigations made in living monocular salamanders. The model also yields an understanding of electrical stimulation experiments in toads.

Abstract: Early postnatal application of thyroid hormones to rats results in morphological changes in septum and hippocampus. Modulation in the expression of either neurotrophins and/or their receptors is postulated to be responsible for these effects. In the present study we tested whether thyroxine administration leads to changes in the expression of neurotrophins of the nerve growth factor (NGF) family. Newborn rats were treated daily with subcutaneous injections of thyroxine until postnatal day (P) 12 at maximum. The pups were killed at defined intervals from P2 to 21. The septal area and the hippocampi were analyzed using the reverse transcriptase-PCR method for quantitation of NGF, brain-derived neurotrophic factor (BDNF), NT-3, and NT-4 messenger RNA (mRNA) levels. In hippocampus of hyperthyroid rats, as compared to controls, we found higher levels of BDNF and NT-3 mRNA over the total investigation period, whereas in the septum a thyroxine-dependent increase in NT-3 mRNA expression was observed. In addition, significant thyroxine-induced effects were found for all variables (except for NGF in the septum) at particular postnatal days. From these data we conclude that modulation of neurotrophin expression is a possible mechanism for the morphological modifications within the hippocampal mossy fiber system and the septohippocampal cholinergic system.

Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural ‘randomization’, 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning.

Acute and chronic treatment of Chinese hamsters and mice with 5, 25 and 125 mg/kg isoniazid (INH) given by oral intubation did not enhance the chromosomal aberration frequencies in spermatogonia. The structural and numerical aberration rates remained in the range of spontaneous events even after the chronic treatment over 12 weeks with 3×125 mg/kg INH per week. This dose is much higher than normally used for prevention and therapy in man (3–16 mg/kg).

Abstract.:  Organisms are often faced with sets of stimuli bearing specifiable relationships to each other. Experimental data suggest that even animals not suspected of being particularly rational can solve problems involving consistent linear relationships. We examine the information processing required to cope with these and related stimulus structures from a theoretical point of view. We show that both a parallel processing neural network model and a serially processing Turing machine model require minimal complexities to process linear hierarchical structures. When dealing with other relational stimulus structures, the models need differing, greater minimal complexities. Siemann and Delius (1994) report experimental results indicating that both pigeons and humans appear to operate according to the parallel, neural network model we propose here. Further experiments likely to be diagnostic are proposed.

Living systems are characterized as self-generating and self-maintaining systems. This type of characterization allows integration of a wide variety of detailed knowledge in biology.

Using the generalized Bloch equations of the preceding paper (II) transient and steady-state experiments in pure quadrupole resonance of spin 1 and spin 3/2 systems are discussed. A method of time averaging is employed to replace the use of auxiliary circular fields. The free induction signal after a short pulse of the radio frequency field as well as the quadrupole echo amplitude after a sequence of two pulses is calculated. For the case of a steady-state rf field the complex susceptibility in terms of relaxation coefficients is given.

The aim of the paper is the development of a complete macroscopic description (generalized Bloch equations) of multipole resonance and relaxation in terms of multipolarisations, which are the expectation values of normalized multipole operators. These operators are constructed with the help of the Wigner-Eckart theorem. Using a relation for their commutators the reversible part of the generalized Bloch equations is derived, the structure of which depends on the spin quantum numberI. The irreversible part was treated in an earlier paper (I).

Physical entropies SB are defined with respect to a certain set of variables, the observationlevel B. For all times in which B exists, SB is the uncertainty H of a density operator RB making H a maximum with respect to the experimental values of B. This definition is not restricted to the thermodynamic equilibrium. The entropies SB measure the vagueness of the description in Hilbert-space caused by the choice of B. The time dependence of the density operator RBis not governed by the von Neumann equation, but in the special case of a “self-consistent“ B it may be calculated with the help of this equation. An increasing SB is obtained.

The longitudinal susceptibility of a spin system in contact with a lattice is calculated from quantum statistics in the high temperature approximation. The method is based on the concept of time dependent temperatures describing the relaxation of several partial energies 〈þv〉(t). The result forχ∥(Ω) is a sum of Debye functions. Explicit formulas for the relaxation times and the coefficients of the Debye functions are given in terms of the Hamiltonians. Three cases are especially discussed: 1. A part of the spin system is strongly coupled to the Zeeman system. 2. The lattice is weakly coupled to the total spin system. It is shown that on certain conditions the total spin systems may be treated as isolated from the lattice. 3. A part of the spin system dependent on the static magnetic field is isolated from the rest. An example is discussed which explains recent measurements obtained in CeCl3· 7H2O.

Equations for time dependent temperatures describing relaxation phenomena are deduced from quantum statistics. The basic concept is the selfconsistency of an observation level formed by partial energies of a system which means that the values of energies at a given timetdetermine the values at a later timet′within macroscopic accuracy. The relaxation coefficients are expressed in terms of microscopic quantities.

A set of observables describing a macroscopic system — an observation level — defines a generalized canonical statistical operator R. The case is considered that parts þv of the Hamiltonian form the observation level; it leads to systems with several temperatures. Generally the Hamiltonians þv do not only operate in partsUv of a product space, so that the statistical operator R is not a product of operators Rv. In this case the observation level is called undivisible. Examples: a system with different Zeeman and interaction temperatures; several temperatures within a system of effective spins>1/2; a Fermi or Bose gas with different spin and orbital temperatures.

The multipole resonance and relaxation is discussed starting with a general consideration of the quantum mechanical dynamics of spinsystems with arbitrary spinI. The irreversible entropy production as a function of the multipolarisations is calculated from the density operator, expanded in terms of a complete set of orthonormal multipole operators. By use of the methods of thermodynamics of irreversible processes one obtains relaxation equations, which are a generalization of the Bloch equations of pure magnetic dipole relaxation. They connect the time derivatives of the multipolarisations with affinities, which are defined by the expansion of the logarithmus of the density operator; for small multipolarisations the affinities are equal to the multipolarisations themselves. Relations for the relaxation matrix are discussed, especially a derivation is given for reciprocal relations between the relaxation coefficients. In the special case of spinI=1 the equations of quadrupole relaxation are studied for axial symmetry.