Neural correlates of frog calling

Summary A tissue bath incorporating a screen for support of the specimen and an air-lift pump to circulate saline across the screen was designed to provide maximum exposure of isolated frog brainstems ofRana pipiens pipiens to oxygenated saline (Fig. 1). Normal neural correlates of electrically-evoked mating calling were recorded from the region of the pretrigeminal nucleus and the laryngeal nerve in the isolated brainstem (Fig. 3A) and isolated hemi-brainstem (Fig. 2) of the Northern leopard frog. Conspicuous slow-wave activity in the region of the pretrigeminal nucleus supports the possibility that this may be an important integrative area for calling. It appears that the pretrigeminal region is not able, independently, to generate the pulses of the vocal phase of calling. Synchronizing and reinforcing inter-connections between the calling mechanisms of the two sides were identified. The data are summarized in a revised model of mating calling (Fig. 7).This work was supported by NINDS grant NS-06673. The electronic equipment was set up and maintained by Mr. Wayne R. Hudson. I am grateful to Dr. William Van Meter for suggesting the Sylgard for the pinning block and to Dr. Patricia Gallagher for suggesting the saline solution of Phillis and Tebcis.     

Do Male White-Lipped Frogs Use Seismic Signals for Intraspecific Communication?

Modern frogs and toads possess a structurally unique saccule,endowing them with seismic sensitivity greater than that observedso far in any other group of terrestrial vertebrates. In synchronywith their advertisement calls, approximately half of the callingmales of one frog species, the Puerto-Rican white-lipped frog(Leptodactylus albilabris), produce impulsive seismic signals(thumps). The spectral distribution of power in these seismicsignals matches precisely the spectral sensitivity of the frog'ssaccule. The signals have sufficient amplitude to be sensedeasily by the frog's saccule up to several meters from the source—wellbeyond the typical spacing when these frogs are calling in agroup. This circumstantial evidence suggests that white-lippedfrogs may use the seismic channel in intraspecific communication,possibly as an alternative to the airborne channel, which oftenis cluttered with noise and interference. Using the frog's vocalizationsas our assay, we set out to test that proposition. In responseto playback calls, the male white-lipped frog adjusts severalof its own calling parameters. The most conspicuous of theseinvolves call timing—specifically the tendency for a gapin the distribution of call onsets, precisely timed with respectto the onsets of the playback calls. When the airborne componentis unavailable (e.g., masked by noise), approximately one infive animals produces the calling gap in response to the seismicsignals alone.     

Intracellular location regulates calcium-calmodulin-dependent activation of organelle-restricted eNOS

Mislocalization of endothelial nitric oxide (NO) synthase (eNOS) in response to oxidized low-density lipoprotein, cholesterol depletion, elevated blood pressure, and bound eNOS interacting protein/NOS traffic inducer is associated with reduced NO release via unknown mechanisms. The proper targeting of eNOS to the plasma membrane or intracellular organelles is an important regulatory step controlling enzyme activity. Previous studies have shown that plasma membrane eNOS is constitutively phosphorylated on serine 1179 and highly active. In contrast, the activity of eNOS targeted to intracellular organelles is more complex. The cis-Golgi eNOS is fully activated by Akt-dependent phosphorylation. However, eNOS targeted to the trans-Golgi is decidedly less active in response to all modes of activation, including mutation to the phosphomimetic aspartic acid. In this study, we establish that when expressed within other intracellular organelles, such as the mitochondria and nucleus, the activity of eNOS is also greatly reduced. To address the mechanisms underlying the impaired catalytic activity of eNOS within these locations, we generated subcellular-targeted constructs that express a calcium-independent NOS isoform, iNOS. With the use of organelle specific (plasma membrane, cis- vs. trans-Golgi, plasma membrane, and Golgi, nucleus, and mitochondria) targeting motifs fused to the wild-type iNOS, we measured NO release from intact cells. With the exception of the Golgi lumen, our results showed no impairment in the ability of targeted iNOS to synthesize NO. Confirmation of correct targeting was obtained through confocal microscopy using identical constructs fused to the green fluorescent protein. We conclude that the reduced activation of eNOS within discrete cytoplasmic regions of the Golgi, the mitochondria and the nucleus is primarily due to insufficient access to calcium-calmodulin. nitric oxide; Akt; Golgi     

迷走神经背核的研究进展

迷走神经背核（ＤＭＶ）是一个重要的内脏运动核团和内脏感觉核团。ＤＭＶ与中枢及外周存在广泛的纤维联系。ＤＭＶ和孤束核、最后区一起构成了“迷走感觉运动中枢”。ＤＭＶ存在神经－体液回路,使ＤＭＶ神经元可以直接感受外周血及脑脊液中的信息。ＤＭＶ含乙酰胆碱、儿茶酚胺、神经肽类等多种递质及相应受体。ＤＭＶ参与中枢调节胃肠、心血管及内分泌等生理功能。     

Some Aspects of Ontogeny of the Shoot Apices of Solanum melongena L. and Capsicum annuum L.

The ontogeny of the vegetative shoot apices of two importantvegetable plants, Solanum melongena L. and Capsicum annuum L.is described. Each shoot apex is studied at different stagesof seed germination. The relationship between time of germinationand (i) area of vacuoles in the cell, (ii) total area of thecell, (iii) area of the nucleus in the cell, and (iv) ratioof area of vacuoles in the cell to the total area of the cellin each apex is examined. The differentiation of cytohistologicalzonation in both apices is distinct only after one or two leavesare initiated and developed. At a certain stage heterogeneityin staining in the peripheral region of the shoot apex of S.melongena is found. The zonation in both plants differentiatesgradually in histological and cytological features. Vacuolationincreases or decreases in all the cells of the shoot apex orin the cells of a particular region of the shoot apex at differentstages of its ontogeny.     

Localization of functional regions of human mesial cortex by somatosensory evoked potential recording and by cortical stimulation

We describe methods of localizing functional regions of the mesial wall, based on 47 patients studied intraoperatively or following chronic implantation of subdural electrodes. Somatosensory evoked potentials were recorded to stimulation of posterior tibial, dorsal pudendal, median, and trigeminal nerves. Bipolar cortical stimulation was performed, and in 4 cases movement-related potentials were recorded.The cingulate and marginal sulci formed the inferior and posterior borders of the sensorimotor areas and the supplementary motor area (SMA). The foot sensory area occupied the posterior paracentral lobule, while the genitalia were represented anterior to the foot sensory area, near the cingulate sulcus. The foot motor area was anterior and superior to the sensory areas, but there was overlap in these representations. There was a rough somatotopic organization within the SMA, with the face represented anterior to the hand. However, there was little evidence of the “pre-SMA” region described in monkeys. Complex movements involving more than one extremity were elicited by stimulation of much of the SMA. The region comprising the supplementary sensory area was not clearly identified, but may involve much of the precuneus. Movement-related potentials did not provide additional localizing information, although in some recordings readiness potentials were recorded from the SMA that appeared to be locally generated.     

Acoustic preferences and localization performance of blood-sucking flies (Corethrella Coquillett) to tungara frog calls

Mating signals that increase attractiveness of males to femalescan also increase conspicuousness of the signaler to predatorsand parasites. We investigated the acoustic preference of speciesof blood-sucking flies of the genus Corethrella (Diptera: Corethrellidae),which eavesdrop on the sexual advertisement signals of túngarafrogs (Physalaemus pustulosus). Male frogs of this species facultativelyproduce 2 types of mating calls: simple (whines alone) and complex(whines and chucks). We tested the acoustic preference of theflies and their ability to locate their host when the frogsproduce simple or complex calls. The flies exhibited phonotaxisto both types of calls but were preferentially attracted tocomplex calls. We show that acoustic information alone is sufficientfor the flies' accurate localization of calling frogs. Complexcalls, however, were not approached at closer distance or withdecreased landing error (i.e., proportion of landings outsidethe target) than simple calls, suggesting that call structuredoes not influence localization performance. Female túngarafrogs and frog-eating bats (Trachops cirrhosus) also prefercomplex to simple túngara frog calls. Thus, intendedand unintended receivers with different ear morphologies exhibitthe same preference for a specific túngara frog calltype. This result is discussed in the context of the evolutionof call attractiveness in a communication network.     

Organization of diencephalon of the sturgeons. Posterior tubercular area. Periventricular and rostral parts

Cytoarchitectonics of periventricular and rostral parts of the posterior tubercular area of diencephalon was studied in four species of the cartilaginous ganoids by using routine Nissl staining and Bielschowski impregnation technique in Viktorov’s modification. The posterior tubercular area in the giant sturgeon Huso huso L., the Kura sturgeon Acipenser güldenstädtii persicus n. Kurensis Belyaeff, the stellate sturgeon Ac. stellatus Pall., and the barbel sturgeon Ac. nudiventris Lov. was shown to have similar structure. Six structures were identified in these areas: the periventricular nucleus, paraventricular organ, nucleus of the paraventricular organ, and posterior tuberal nucleus in the periventricular region and preglomerular medial and lateral nuclei in the rostral region. Both nuclei of the rostral zone are migrated nuclei. Out of nuclei of the posterior tubercle regions, the posterior tuberal and medial preglomerular nuclei are characterized by polymorphism of cellular elements. A conclusion is made that these parts of the posterior tubercular area in the sturgeons considered to be the lower ray-finned fish are comparable with those of the higher teleosts, and even are more differentiated according to some parameters.     

Evolutionary divergence in developmental strategies and neuromodulatory control systems of two amphibian locomotor networks

Attempts to understand the neural mechanisms which produce behaviourmust consider both prevailing sensory cues and the central cellularand synaptic changes they direct. At each level, neuromodulationcan additionally shape the final output. We have investigatedneuromodulation in the developing spinal motor networks in hatchlingtadpoles of two closely related amphibians, Xenopus laevis andRana temporaria to examine the subtle differences in their behavioursthat could be attributed to their evolutionary divergence. At the point of hatching, both species can swim in responseto a mechanosensory stimulus, however Rana embryos often displaya more forceful, non-locomotory coiling behaviour. Whilst thesynaptic drive that underlies these behaviours appears similar,subtle inter-specific differences in neuronal properties shapemotor outputs in different ways. For example, Rana neurons expressN-methyl-D-aspartate (NMDA)/serotonin (5-HT)-dependent oscillations,not present in hatchling Xenopus and many also exhibit a prominentslow spike after-hyperpolarisation. Such properties may endowthe spinal circuitry of Rana with the ability to produce a moreflexible range of outputs. Finally, we compare the roles of the neuromodulators 5-HT, noradrenaline(NA) and nitric oxide (NO) in shaping motor outputs. 5-HT increasesburst durations during swimming in both Xenopus and Rana, but5-HT dramatically slows the cycle period in Rana with littleeffect in Xenopus. Three distinct, but presumably homologousNO-containing brainstem clusters of neurons have been described,yet the effects of NO differ between species. In Xenopus, NOslows and shortens swimming in a manner similar to NA, yet inRana NO and NA elicit the non-rhythmic coiling pattern.     

SPERMOGENESIS AND SPERM STRUCTURE IN THREE SPECIES OF PATELLOIDA AND ONE SPECIES OF NIPPONACMAEA (PATELLOGASTROPODA: ACMAEOIDEA)

The spermatozoa of Patelloida profunda albonotata, P. saccharina,P. pygmaea and Nipponacmaea schrenkii (Lottiidae) are describedby transmission electron microscopy. All have ect-aquasperm,typical of invertebrates using external fertilization. The spermof all four species have a cylindrical nucleus (length: breadth> 4: 1 in P. p. albonotata and P. saccharina; <4: 1 inP. pygmaea and N. schrenkii) which tapers towards the roundedanterior end. All have an acrosome with a posterior acrosomallobe which extends into the centre of the subacrosomal space.In P. p. albonotata and P. saccharina the acrosomal contentsare undifferentiated and the posterior lobe extends to the nucleus,being separated from it by flocculent material. In P. pygmaeathe acrosomal contents are differentiated, the lobe is relativelyshort and the subacrosomal space is filled with material witha fibrous appearance. The acrosome of N. schrenkii is undifferentiatedand the posterior lobe is no more than a bulge. The sperm ofP. p. albonotata and N. sacchrina have a small (0.25 µmlong) cytoplasmic collar which surrounds the axoneme anteriorlywhereas in P. pygmaea and N. schrenkii the cytoplasmic collaris longer (1 µm) and is swollen by an electron-dense vesicle.The composition and function of this vesicle is unknown. Thespermatozoa of Patelloida and Nipponacmaea have structural featureswhich are similar to sperm of the Lottiidae providing some supportfor the placement of these genera in the Lottiidae as proposedby Lindberg & Hedegaard (1996) and Sasaki & Okutani(1993) respectively. The similarities of the sperm of P. pygmaeato N.schrenkii raise some doubts about the tax-onomic statusof the former species. Spermiogenesis in all four species issimilar to that described for other Acmaeoidea and Patelloidea.In P. pygmaea and N. schrenkii, however, in addition to theacrosomal vesicle, the Golgi body produces a number of electron-densevesicles which fuse and eventually form a single vesicle inthe collar of the mid-piece. (Received 24 October 1996; accepted 10 February 1997)     

In Situ Localization of Parental Genomes in a Wide Hybrid

In situ hybridization enabled DNA originating from the two parentalgenomes to be distinguished in plant hybrids. A probe of biotinylatedtotal genomic DNA from Secale africanum labelled the chromosomesof S. africanum origin but not those from Hordeum chilense inroot-tip chromosome spreads of the sexual hybrid between thetwo species. Hybridization of total genomic DNA from S. africanumto DNA on filters (dot blots) confirmed the distinction betweenDNA from Hordeum and Secale. The total genomic probe hybridizedto the whole length of the chromosomes from S. africanum remarkablyuniformly, labelling both euchromatin and heterochromatin, exceptat the centromeric region. The probe binding was visualizedas a yellow colour by the fluorescein-coupled detection systemwhich contrasted with the red fluorescing counterstain of theunlabelled chromatin. The chromosomes originating from bothparents could be seen and distinguished as red and yellow fluorescenceat all stages of the cell cycle. At interphase and prophase,the chromatin originating from the two parental genomes didnot mix. Chromosomes or groups of chromosomes occupied distinctdomains and also tended to be arranged in a Rabl configurationwith the centromeres clustered at one end of the nucleus. Wepropose calling the technique using total genomic DNA as a probe‘genomic in situ hybridization.’ Hordeum chilense, Secale africanum, hybrids, genomic in situ hybridization, DNA, repetitive sequences, chromosomes, chromosome disposition, nuclear order     

Mating call phonotaxis in female American toad: lesions of anterior preoptic nucleus

Lesions of the preoptic area and immediately adjacent septal area were made in female American toads, Bufo americanus. The ability to show mating call phonotaxis (MCP) was then tested for. The intensity of MCP was found to decrease as the degree of damage to the anterior tip of the anterior preoptic nucleus (APON) increased. The APON is known to concentrate androgens and to be essential for mating calling by male anurans. Perhaps the APON is involved also in the detection of the elevated levels of prostaglandin associated with MCP. Even in lesioned toads in which phonotaxis was nearly absent, there was an occasional MCP response that seemed entirely normal. Therefore, the APON is not involved in generating or guiding the motor mechanisms of phonotaxis.     

Comparison of melatonin-binding sites in the brain of two amphibians: an autoradiographic study

Neuroanatomic comparison of the binding capability of 2-[¹²⁵I] iodomelatonin in the crested newt Triturus carnifex Laur. and the green frog Rana esculenta, using quantitative autoradiographic techniques, revealed a heterogeneous distribution pattern. The highest and relatively high binding activities were shown to occur in the optic tracts and in the suprachiasmatic area of the hypothalamus and the optic tectum, respectively, of both species. Low or no 2-[¹²⁵I] iodomelatonin binding values were obtained in the preoptic nucleus, the tuberal hypothalamus, the medulla oblongata, the septum and the dorsal pallium. A differential binding pattern was observed in the amygdaloid nucleus pars lateralis, the striatum and the hindbrain of these amphibians. Indeed, notably high binding levels were shown to occur in the former two brain areas of the crested newt, whereas high levels were displayed in the latter brain region of the green frog. On the basis of elevated quantities of melatonin receptors in mesencephalic, hypothalamic and telencephalic sites, it seems plausible to ascribe some important sensory functions to this receptor system in both species. The remarkably different binding activities in the brain of the two amphibians could be correlated with the simpler cytoarchitectonic brain structure of urodeles and with species-specific variations.     

Male sperm expenditure under sperm competition risk and intensity in quacking frogs

In the frog Crinia georgiana, reproductive behavior comprisesa "guarding tactic," in which males defend spawn sites and attractfemales by calling, and a "sneak tactic," in which males joinspawning pairs. The aims of the present study were to (1) relateejaculate expenditure by "guarding" and "sneak" males to theirprobability of mating with other males present (sperm-competitionrisk), and (2) determine if males adjust their ejaculate expenditureaccording to the number of males involved in a spawning (sperm-competitionintensity). Theory predicts that because sneak males alwaysmate with other males present, they will experience a highersperm-competition risk and should release larger ejaculatesrelative to that of guarding males. However, as the proportionof sneaks in a population increases so does the risk of spermcompetition to guarders, so expenditure by each tactic shouldmove toward equality. Given that the incidence of sneak behavioris high in C. georgiana, guarders and sneaks were expected toexperience similar risks of sperm competition and show similarinvestment in spermatogenesis. Comparison of testes size andejaculate size showed no difference between tactics. Modelsof sperm-competition intensity predict that males should increasetheir ejaculate size when spawning in the presence of one othermale but decrease their ejaculate size when spawning in thepresence of multiple males. Here, males maintained a constantsperm number irrespective of whether a mating involved one,two, or three males. This result suggests that male C. georgianado not facultatively adjust ejaculate investment in responseto fluctuating intensities of sperm competition.     

Pattern of afferents to the lateral septum in the guinea pig

Summary The septal region represents an important telencephalic center integrating neuronal activity of cortical areas with autonomous processes. To support the functional analysis of this brain area in the guinea pig, the afferent connections to the lateral septal nucleus were investigated by the use of iontophoretically applied horseradish peroxidase (HRP). Retrogradely labeled perikarya were located in telencephalic, diencephalic, mesencephalic and metencephalic sites. The subnuclei of the lateral septum (pars dorsalis, intermedia, ventralis, posterior) receive afferents from the (i) medial septal nucleus, diagonal band of Broca (pars horizontalis and pars ventralis), and the principal nucleus of the stria terminalis, the hippocampus, and amygdala (nucleus medialis); (ii) the medial habenular nucleus, and the para- (peri-) ventricular, parataenial and reuniens nuclei of the thalamus; the anterior, lateral and posterior hypothalamic areas in particular, the medial and lateral preoptic, suprachiasmatic, periventricular, paraventricular, arcuate, premammillary, and supramammillary nuclei; (iii) the periaquaeductal grey, ventral tegmental area, nucleus interfascicularis, nucleus reticularis linearis, central linear nucleus, interpeduncular nucleus; (iv) dorsal and medial raphe complex, and locus coeruleus. Each subnucleus of the lateral septum displays an individual, differing pattern of afferents from the above-described regions. Based on a double-labeling method, the vasopressinergic and serotonergic afferents to the lateral septum were found to originate in the nucleus paraventricularis hypothalami and the raphe nuclei, respectively.Abbreviations ARC arcuate nucleus - BNST bed nucleus of the stria terminalis - CL central linear nucleus - DBBh diagonal band of Broca (pars horizontalis) - DBBv diagonal band of Broca (pars ventralis) - DR dorsal raphe nucleus - HC hippocampus - IF interfascicular nucleus - IP interpeduncular nucleus - LC locus coeruleus - LDT laterodorsal tegmental nucleus - LHA lateral hypothalamic area - LPO lateral preoptic area - LSN lateral septal nucleus - MA medial amygdaloid nucleus - MH medial habenular nucleus - MPO medial preoptic region - MR medial raphe nucleus - MSN medial septal nucleus - PAG periaquaeductal grey - PEN periventricular nucleus - PHA posterior hypothalamic area - PMd premammillary region (pars dorsalis) - PMv premammillary region (pars ventralis) - PT parataenial nucleus - PVN paraventricular hypothalamic nucleus - PVT paraventricular thalamic nucleus - RE nucl. reuniens - RL nucl. reticularis linearis - SCN suprachiasmatic nucleus - SMl supramammillary region (pars lateralis) - SMm supramammillary region (pars medialis) - SUB subiculum - TS triangular septal nucleus - VTA ventral tegmental area - ac anterior commissure - bc brachium conjunctivum - bp brachium pontis - cc corpus callosum - fr fasciculus retroflexus - fx fornix - ml medial lemniscus - mlf fasciculus longitudinalis medialis - mp mammillary peduncle - mt mammillary tract - oc optic chiasm - on optic nerve - pc posterior commissure - pt pyramidal tract - sm stria medullaris - st stria terminalis - vhc ventral hippocampal commissure Supported by the Deutsche Forschungsgemeinschaft (Nu 36/2-1)     

The mixed-species chorus as public information: tungara frogs eavesdrop on a heterospecific

Multispecies choruses represent a promising but uninvestigatedforum for public information. Although frogs exposed to a potentialpredator call more readily in the presence of conspecific callsthan in their absence, none are known to make comparable useof heterospecific calls. To test for heterospecific eavesdropping,we isolated calling male túngara frogs (Physalaemus pustulosus),presented them with a potential predator, and recorded theirresponses to playbacks of 1 of 4 stimuli: calls of a conspecific,a sympatric heterospecific (Leptodactylus labialis), an allopatriccongener (Physalaemus enesefae), or silence. We found that malescalled more in response to the L. labialis call than to eitherthe silent stimulus or the P. enesefae call. In contrast, theP. enesefae call did not result in significantly more callingthan the silent stimulus. The conspecific call was the mosteffective at promoting calling. The data indicate that túngarafrogs selectively attend to the call of a heterospecific. Wehypothesize that such heterospecific eavesdropping contributesto the emergent behavior of mixed-species choruses.     

粘虫的胚胎发育

粘虫(Mythimna separata)胚胎发育经过卵裂及胚盘形成、胚带及原肠发生、胚带分节及附肢形成、体壁形成及背向闭合、胚胎反转和器官发生与形成6个时期。粘虫卵在25℃,胚胎发育至12h,胚带呈新月形或“C”字形。随着原肠发生,首先出现口陷与肛陷,与此同时,胚带逐渐伸长并开始分节。胚胎发育至32h,胚带头尾相接并呈波浪形弯曲,在胚胎反转前,胚胎发育至42h,前肠、后肠及马氏管已经形成。胚胎发育至54h时,胚动完成之 后,中肠才明显可见。同时将大量卵黄包围起来。神经系统的发生与气管形成始于原肠发生之后,至胚胎反转之前,神经节索才出现,随着胚动发生,神经节体积不断增大,腹神经索逐渐形成,纵走气管明显可见。     

Multimodal cues improve prey localization under complex environmental conditions

Predators often eavesdrop on sexual displays of their prey. These displays can provide multimodal cues that aid predators, but the benefits in attending to them should depend on the environmental sensory conditions under which they forage. We assessed whether bats hunting for frogs use multimodal cues to locate their prey and whether their use varies with ambient conditions. We used a robotic set-up mimicking the sexual display of a male túngara frog (Physalaemus pustulosus) to test prey assessment by fringe-lipped bats (Trachops cirrhosus). These predatory bats primarily use sound of the frog''s call to find their prey, but the bats also use echolocation cues returning from the frog''s dynamically moving vocal sac. In the first experiment, we show that multimodal cues affect attack behaviour: bats made narrower flank attack angles on multimodal trials compared with unimodal trials during which they could only rely on the sound of the frog. In the second experiment, we explored the bat''s use of prey cues in an acoustically more complex environment. Túngara frogs often form mixed-species choruses with other frogs, including the hourglass frog (Dendropsophus ebraccatus). Using a multi-speaker set-up, we tested bat approaches and attacks on the robofrog under three different levels of acoustic complexity: no calling D. ebraccatus males, two calling D. ebraccatus males and five D. ebraccatus males. We found that bats are more directional in their approach to the robofrog when more D. ebraccatus males were calling. Thus, bats seemed to benefit more from multimodal cues when confronted with increased levels of acoustic complexity in their foraging environments. Our data have important consequences for our understanding of the evolution of multimodal sexual displays as they reveal how environmental conditions can alter the natural selection pressures acting on them.     

Aggressive Behavior Evoked by Radio Stimulation in Monkey Colonies

Macaca mulatta with multilead electrodes permanently implantedin the brain were electrically stimulated, either under restraint,or by radio while moving freely as part of a colony, in whichcase individual and social behavior were recorded, analyzed,and quantified with the aid of time-lapse photography. Somecerebral radio stimulations evoked complex sequences of wellorganized responses. Increase in running and in offensive behaviorwas produced by excitation of midline thalamus, while even fasterrunning without changes in aggressiveness was produced by stimulationof the fimbria of the fornix. Conditioning was absent in thefirst case, but it was easily established in the latter. Increasein aggressive behavior was also produced by stimulation of Forel'sfield, the nucleus ventralis posterior lateralis of the thalamus,and the central gray matter. Increase in aggressiveness wasoriented by the animal according to past experience, likes anddislikes, and was adapted to the changing strategies of itsopponent, indicating an excellent processing of sensory information,and demonstrating that brain stimulation had induced a "drive"and not a stereotyped motor response. As a working hypothesis it is proposed that cerebral mechanismsfor perception of pain and for aggressive behavior have differentanatomical and physiological systems closely interrelated byuse, disuse, and conditioning.     

The morphology of the cerebellar nuclei of Galago and Tupaia

The cerebellar nuclei of the lesser bushbaby (Galago senegalensis) and the tree shrew (Tupaia glis) were studied. The cerebellar nuclear grey of Galago is divisible into a medial nucleus, a nucleus interpositus anterior, a nucleus interpositus posterior, and a lateral nucleus. The lateral nucleus is slightly concave medially suggestive of a primitive hilus. The interpositus nucleus is divided into anterior and posterior portions by a delicate lamina of fibers. The medial cerebellar nucleus is an irregular mass of cells located dorsal to the fourth ventricle. The cerebellar nuclear grey of Tupaia is also divisible into a medial nucleus, a nucleus interpositus anterior, a nucleus interpositus posterior, and a lateral cerebellar nucleus. The medial cerebellar nucleus is located dorsal to the fourth ventricle. The nucleus interpositus anterior and nucleus interpositus posterior are joined together and with the lateral nucleus in the caudo-ventral region. The NIA and NIP have an anterior-posterior relationship to each other and the lateral nucleus has no apparent undulations suggestive of early sacculations. The configuration of the cerebellar nuclei of Tupaia more closely resembles the more primitive patterns of the rat, hedgehog, and mole than those of Galago or other primates.