Mathematical-technical model of passive and active vibrations of the basilar membrane]

On the basis of the physiological measurements made by v. Békésy and Johnstone, we developed a mathematical model to describe passive and active displacement patterns of the basilar membrane. Approximation of the model functions to the measured values is achieved with the aid of the linear least squares method. Using frequency mapping, the distribution of the basilar membrane displacement is presented in three-dimensional graphic form. The resulting application possibilities of this approach, for example, to electronic simulation of inner ear functions and speech processing systems, are discussed.     

Cerebral activation to intranasal chemosensory trigeminal stimulation

Although numerous functional magnetic resonance imaging (FMRI) studies have been performed on the processing of olfactory information, the intranasal trigeminal system so far has not received much attention. In the present study, we sought to delineate the neural correlates of trigeminal stimulation using carbon dioxide (CO(2)) presented to the left or right nostril. Fifteen right-handed men underwent FMRI using single runs of 3 conditions (CO(2) in the right and the left nostrils and an olfactory stimulant-phenyl ethyl alcohol-in the right nostril). As expected, olfactory activations were located in the orbitofrontal cortex (OFC), amygdala, and rostral insula. For trigeminal stimulation, activations were found in "trigeminal" and "olfactory" regions including the pre- and postcentral gyrus, the cerebellum, the ventrolateral thalamus, the insula, the contralateral piriform cortex, and the OFC. Left compared with right side stimulations resulted in stronger cerebellar and brain stem activations; right versus left stimulation resulted in stronger activations of the superior temporal sulcus and OFC. These results suggest a trigeminal processing system that taps into similar cortical regions and yet is separate from that of the olfactory system. The overlapping pattern of cortical activation for trigeminal and olfactory stimuli is assumed to be due to the intimate connections in the processing of information from the 2 major intranasal chemosensory systems.     

Time Course and Action Spectrum of Vibrotactile Adaptation

In a series of experiments designed to explore the processes underlying adaptation of the sense of flutter-vibration, vibrotactile threshold was measured on the pad of the index finger, using Békésy tracking. Unadapted thresholds were first measured, for a number of frequencies (4-90 Hz) and contactor sizes (1-8 mm diameter). As expected, these measurements indicated the presence of (1) a Pacinian system possessing spatial summation and increasing in sensitivity, as frequency was raised, at the rate of 12 dB/octave; and (2) a non-Pacinian system showing little spatial summation, and with a frequency characteristic matching that of the NP I mechanism of Bolanowski et al. (1988). These baseline data of Experiment 1 guided the selection of stimulus parameters for subsequent experiments, in which threshold for a test stimulus was measured before, during, and after periods of vibrotactile adaptation.

In Experiment 2, test stimuli of 10 H_z and 50 H_z were combined factorially with 30-dB SL adapting stimuli of the same two frequencies. When the test stimulus was 10 Hz, the two adapting frequencies were equally effective in raising threshold; however, when the 50-Hz test stimulus was used, the 50-Hz adapting stimulus raised threshold by a greater amount than did the 10-Hz adapter. These results confirm on the finger the independence of adaptation in Pacinian and non-Pacinian channels, a result previously established on the thenar by other workers. For all four frequency combinations, threshold rose exponentially with a time constant of 1.5-2 min.

In Experiment 3, an action spectrum was determined, showing the adapting amplitude needed at each of a series of frequencies to raise the threshold of a 10-Hz stimulus by 10 dB; this spectrum was essentially flat from 30 to 90 Hz. The results, taken in conjunction with what is known about rapidly adapting cutaneous mechanoreceptors, imply that the effectiveness of an adapting stimulus is not determined solely by the amount of activity it generates in first-order afferents.     

Time course and action spectrum of vibrotactile adaptation

In a series of experiments designed to explore the processes underlying adaptation of the sense of flutter-vibration, vibrotactile threshold was measured on the pad of the index finger, using Békésy tracking. Unadapted thresholds were first measured, for a number of frequencies (4-90 Hz) and contactor sizes (1-8 mm diameter). As expected, these measurements indicated the presence of (1) a Pacinian system possessing spatial summation and increasing in sensitivity, as frequency was raised, at the rate of 12 dB/octave; and (2) a non-Pacinian system showing little spatial summation, and with a frequency characteristic matching that of the NP I mechanism of Bolanowski et al. (1988). These baseline data of Experiment 1 guided the selection of stimulus parameters for subsequent experiments, in which threshold for a test stimulus was measured before, during, and after periods of vibrotactile adaptation. In Experiment 2, test stimuli of 10 Hz and 50 Hz were combined factorially with 30-dB SL adapting stimuli of the same two frequencies. When the test stimulus was 10 Hz, the two adapting frequencies were equally effective in raising threshold; however, when the 50-Hz test stimulus was used, the 50-Hz adapting stimulus raised threshold by a greater amount than did the 10-Hz adapter. These results confirm on the finger the independence of adaptation in Pacinian and non-Pacinian channels, a result previously established on the thenar by other workers. For all four frequency combinations, threshold rose exponentially with a time constant of 1.5-2 min. In Experiment 3, an action spectrum was determined, showing the adapting amplitude needed at each of a series of frequencies to raise the threshold of a 10-Hz stimulus by 10 dB; this spectrum was essentially flat from 30 to 90 Hz. The results, taken in conjunction with what is known about rapidly adapting cutaneous mechanoreceptors, imply that the effectiveness of an adapting stimulus is not determined solely by the amount of activity it generates in first-order afferents.     

Norepinephrine Is Lateralized Within the Olfactory Bulbs of Male Mice

Abstract: Concentrations and in vitro release of norepinephrine were determined from left and right olfactory bulbs of adult male CD-1 mice. Norepinephrine concentrations from the left olfactory bulbs were significantly greater than those of the right ( p < 0.01). No statistically significant differences were obtained for dopamine, nor were there differences in tissue weights between the left and right olfactory bulb tissue samples. To verify further this asymmetry, release rates of norepinephrine were measured from superfused left and right olfactory bulbs. Norepinephrine output from the left olfactory bulb was significantly greater than that from the right ( p < 0.05). These results show that norepinephrine is lateralized within the olfactory bulbs of male mice. This asymmetry shows a clear catecholamine specificity with regard to concentrations and may be related to the lateralized olfactory processing that has been reported to occur in humans.     

Black Bear Predation on Salmon at Olsen Creek,Alaska

Das Verhalten des Baribal (Ursus americanus) wurde im Sommer 1967 in Alaska an einem Fluß beobachtet, in dem Ketalachs und Buckellachs ablaichen. Die Bären waren von der Morgendämmerung an 2 Std. aktiv und mehrere Stunden vor und nach Sonnenuntergang. In erster Linie fraßen sie Lachse, die andere Bären getötet und liegen gelassen hatten. Auf einen gefangenen Lachs kamen etwa 7 Versuche. Baribals bevorzugen den Rogen und lassen oft den Rest liegen; sie erkennen laichreife ♀♀. Obwohl sie gleich viele ♂♂ wie ♀♀ fingen, behielten sie doppelt so viele ♀♀; 65 % davon hatten beim Fang noch nicht abgelaicht. Insgesamt fangen die Bären 8 % der weiblichen Lachse, ehe sie ablaichen können. Fisch-Reviere scheinen die Bären nicht zu haben.     

A two year pollen calendar for traditionally produced honey types from Gaya,southern Niger

A pollen calendar of traditionally produced honeys in Gaya/southern Niger was established for a two year period. The region is situated in the transition zone from the sahelian to the sudanian savannas. In this area honey represents an appreciated source for further income for the cultivators. Palynological investigations of the honey samples showed that the bees regularly exploit a restricted number of trees and bushes, such as Combretum, Terminalia or Guiera throughout the whole year or Lannaea, Parkia and Bombax during the winter and spring. Other Sudanian trees and bushes are only occasionally visited in addition. During the dry season Gramineae are also exploited because of the sap provided by the Aphids. In their pollen spectra the honeys reflect both the vegetation types and the agrarian systems of the region as for as can be traced from their collection time and from observations on the flowering period of the trees and bushes visited.

Ein zweijähriger Pollenkalender konnte für die Region Gaya/Südniger mit Hilfe traditionell produzierter Honige aufgestellt werden. Die Region liegt im Übergang von den sahelischen zu den sudanischen Savannen. In dieser Region ist Honig eine willkommene zusätzliche Einkommensquelle für die Bauer. Die pollenanalytischen Untersuchungen zeigen, daß nur eine begrenzte Zahl von Bäumen und Stäuchern regelmäßig von den Bienen besucht wird, Combretum, Terminalia und Guiera über das ganze Jahr und Parkia, Lannaea und Bombax innerhalb der Wintersaison. Eine größere Zahl sudanischer Elemente wird nur zufällig genutzt. Während der Trockenzeit werden auch Gräser abgesammelt, hauptsächlich wegen des Honigsaftes, der von Aphiden produziert wird.

Die Honige spiegeln die Vegetationstypen der Region und deren Agrarsysteme in ihren Pollenspektrum und können auch durch den Vergleich mit den Blühperioden der entsprechenden Bäume und Sträucher in ihrer Produktionszeit bestimmt werden.

Les études de mélissopalynologie présentées portent sur la région de Gaya au Sud du Niger. A partir des spectres polliniques obtenus par l'analyse des miels de production traditionelle il a été possible d'établir un calendrier pollinique.

La région de Gaya est située dans une zone de transition entre les savanes sahéliennes et soudaniennes. C'est dans cette partie du Niger que la production de miel est la plus élevée et fournit un surplus économique notable pour les cultivateurs.

Les investigations palynologiques ont montré que les abeilles visitent régulièrement un nombre restreint d'arbres et d'arbustres tels Combretum, Terminalia et Guiera pendant toute l'anné, ainsi Parkia, Lannaea et Bombax durant la période hivernale. A la saison sèche, les graminées sont également exploitées pour Ieurs exsudats dus aux Aphides.

Les spectres polliniques reflètent parfaitement les principaux types de végétation et des systèmes agaires de la région durant la période de production mellifère, par comparaison avec la saison de floraison des arbres et des arbustres butinés.     

Antennal Asymmetry in Social Behavior of the Australian Stingless Bee, <Emphasis Type="Italic">Tetragonula carbonaria</Emphasis>

The left and right antennae of stingless bees have different roles in learning and recall of olfactory memory. Antennal asymmetry in social behavior is reported here. Approaches and physical contacts were scored in dyads of stingless bees (Tetragonula carbonaria): dyads in which both bees had only their right antennae (left antennae removed) made significantly more physical contacts with each other than dyads in which both bees had only their left antennae. In dyads of one left and one right, it was found, unexpectedly, that the bee with a left antenna approached the bee with the right antenna more often that the other way around, and the bee with the left antenna often attacked (by biting) its hive mate. Hence, the low number of contacts in dyads of bees using their left antennae appears to be due to mutual avoidance. Whereas use of the right antenna stimulates positive contact, the left stimulates avoidance or attack. Via such left-right asymmetries, intact bees may compute behavior directed towards friend and foe. Such antennal asymmetry may have evolved concomitantly with eusocial behavior. We found no evidence that it was associated with significant differences in the number of olfactory or non-olfactory sensilla on the left versus right antenna.     

Enhanced Assymetrical Noradrenergic Transmission in the Olfactory Bulb of Deoxycorticosterone Acetate-Salt Hypertensive Rats

The ablation of olfactory bulb induces critical changes in dopamine, and monoamine oxidase activity in the brain stem. Growing evidence supports the participation of this telencephalic region in the regulation blood pressure and cardiovascular activity but little is known about its contribution to hypertension. We have previously reported that in the olfactory bulb of normotensive rats endothelins enhance noradrenergic activity by increasing tyrosine hydroxylase activity and norepinephrine release. In the present study we sought to establish the status of noradrenergic activity in the olfactory bulb of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Different steps in norepinephrine transmission including tyrosine hydroxylase activity, neuronal norepinephrine release and uptake were assessed in the left and right olfactory bulb of DOCA-salt hypertensive rats. Increased tyrosine hydroxylase activity, and decreased neuronal norepinephrine uptake were observed in the olfactory bulb of DOCA-salt hypertensive rats. Furthermore the expression of tyrosine hydroxylase and its phosphorylated forms were also augmented. Intriguingly, asymmetrical responses between the right and left olfactory bulb of normotensive and hypertensive rats were observed. Neuronal norepinephrine release was increased in the right but not in the left olfactory bulb of DOCA-salt hypertensive rats, whereas non asymmetrical differences were observed in normotensive animals. Present findings indicate that the olfactory bulb of hypertensive rats show an asymmetrical increase in norepinephrine activity. The observed changes in noradrenergic transmission may likely contribute to the onset and/or progression of hypertension in this animal model.     

Role of the Right- and Left-Hemispheric Structures in Speech and Memory Formation in Children

The role of structures of the left and right cerebral hemispheres in formation of speech function and memory was studied on the basis of complex examination of children with developmental speech disorders. On the basis of EEG estimation of the functional state of the brain, children were classified in two groups depending on the side of localization of changes in electrical activity: those with local changes in electrical activity in the left hemisphere (group I) and those with changes in the right hemisphere (group II). The medical history suggested that the observed features of topography of local changes in electrical activity were linked with the character of prenatal and labor complications and their consequences leading to embryo- and ontogenetic disorders in development of different brain regions. Comparison of the results of neuropsychological examination of the two groups showed that different regions of the brain cortex of both the left and right hemispheres are involved in speech formation. However, a specific role of the right hemisphere in formation and actualization of automatic speech series was revealed. It was suggested that the integrity of gnostic functions of the right hemisphere and, primarily, the spatial organization of perception and movements is a necessary factor of development of auditory–speech and nominative memory.     

A multimodal approach for tracing lateralisation along the olfactory pathway in the honeybee through electrophysiological recordings,morpho-functional imaging,and behavioural studies

Recent studies have revealed asymmetries between the left and right sides of the brain in invertebrate species. Here we present a review of a series of recent studies from our laboratories, aimed at tracing asymmetries at different stages along the honeybee’s (Apis mellifera) olfactory pathway. These include estimates of the number of sensilla present on the two antennae, obtained by scanning electron microscopy, as well as electroantennography recordings of the left and right antennal responses to odorants. We describe investigative studies of the antennal lobes, where multi-photon microscopy was used to search for possible morphological asymmetries between the two brain sides. Moreover, we report on recently published results obtained by two-photon calcium imaging for functional mapping of the antennal lobe aimed at comparing patterns of activity evoked by different odours. Finally, possible links to the results of behavioural tests, measuring asymmetries in single-sided olfactory memory recall, are discussed.     

Besprechungen / Reviews

Book Reviewed in this article: Wallraff , H. G. (1970): Weitere Volierenversuche mit Brieftauben: Wahrscheinlicher Einfluß dynamischer Faktoren der Atmosphäre auf die Orientierung. Wallraff , H. G. (1974): Das Navigationssystem der Vögel. R. Oldenbourg Verlag, München — Wien. (Schriftenreihe Kybernetik, H. Marko und H. Mittelstaedt eds.) Papi , F., V. Fiaschi , S. Benvenuti und N. E. Baldaccini (1973): Pigeon homing: outward journey detours influence the initial orientation (Zum Heimfinden der Tauben: Umwege zum Auflaßplatz beeinflussen die Anfangsorientierung). Benvenuti , S., V. Fiaschi , L. Fiore und F. Papi (1973): Disturbances of homing behaviour in pigeons experimentally induced by olfactory stimuli (Durch Geruchsreize künstlich gestörtes Heimfinden von Tauben). Benvenuti , S., V. Fiaschi , L. Fiore und F. Papi (1973): Homing performances of inexperienced and directionally trained pigeons subjected to olfactory nerve section (Heimfinden richtungsdressierter und unerfahrener Tauben nach Durchtrennung des Riechnervs). Papi , F., L. Fiore , V. Fiaschi und S. Benvenuti (1973): An experiment for testing the hypothesis of olfactory navigation of homing pigeons (Experimentelle Prüfung der Annahme, daß Tauben nach dem Geruch heimfinden). Baldaccini , N. E., S. Benvenuti , V. Fiaschi , P. Ioalé und F. Papi (1974): Pigeon homing: Effects of manipulation of sensory experience at home site (Zum Heimfinden der Tauben: Wirkungen aufgezwungener Geruchserfahrung am Heimatort). Papi , F., P. Ioalé , V. Fiaschi , S. Benvenuti und N. E. Baldaccini (1974): Olfactory navigation of pigeons: the effect of treatment with odorous air currents (Geruchsorientierung von Tauben nach Gewöhnung an duftende Luftströme). Scherzinger , W. (1974): Zur Ethologie und Jugendentwicklung der Schnee-Eule (Nyctea scandiaca) nach Beobachtungen in Gefangenschaft. Jilka , A., und B. Leisler (1974): Die Einpassung dreier Rohrsängerarten (Acrocephalus schoenobaenus, A. scirpaceus, A. arundinaceus) in ihre Lebensräume in bezug auf das Frequenzspektrum ihrer Reviergesänge. J. Orn. Thielcke , G. (1974): Stabilität erlernter Singvogel-Gesänge trotz vollständiger geographischer Isolation. Frisch , K. von (1974): Tiere als Baumeister (unter Mitarbeit von O. von Frisch).     

Location coding by opponent neural populations in the auditory cortex

Although the auditory cortex plays a necessary role in sound localization, physiological investigations in the cortex reveal inhomogeneous sampling of auditory space that is difficult to reconcile with localization behavior under the assumption of local spatial coding. Most neurons respond maximally to sounds located far to the left or right side, with few neurons tuned to the frontal midline. Paradoxically, psychophysical studies show optimal spatial acuity across the frontal midline. In this paper, we revisit the problem of inhomogeneous spatial sampling in three fields of cat auditory cortex. In each field, we confirm that neural responses tend to be greatest for lateral positions, but show the greatest modulation for near-midline source locations. Moreover, identification of source locations based on cortical responses shows sharp discrimination of left from right but relatively inaccurate discrimination of locations within each half of space. Motivated by these findings, we explore an opponent-process theory in which sound-source locations are represented by differences in the activity of two broadly tuned channels formed by contra- and ipsilaterally preferring neurons. Finally, we demonstrate a simple model, based on spike-count differences across cortical populations, that provides bias-free, level-invariant localization—and thus also a solution to the “binding problem” of associating spatial information with other nonspatial attributes of sounds.     

Deviation of eyes and head in acute cerebral stroke

Background  

It is a well-known phenomenon that some patients with acute left or right hemisphere stroke show a deviation of the eyes (Prévost's sign) and head to one side. Here we investigated whether both right- and left-sided brain lesions may cause this deviation. Moreover, we studied the relationship between this phenomenon and spatial neglect. In contrast to previous studies, we determined not only the discrete presence or absence of eye deviation with the naked eye through clinical inspection, but actually measured the extent of horizontal eye-in-head and head-on-trunk deviation. In further contrast, measurements were performed early after stroke onset (1.5 days on average).     

Spatial frames of reference and somatosensory processing: a neuropsychological perspective.

In patients with lesions in the right hemisphere, frequently involving the posterior parietal regions, left-sided somatosensory (and visual and motor) deficits not only reflect a disorder of primary sensory processes, but also have a higher-order component related to a defective spatial representation of the body. This additional factor, related to right brain damage, is clinically relevant: contralesional hemianaesthesia (and hemianopia and hemiplegia) is more frequent in right brain-damaged patients than in patients with damage to the left side of the brain. Three main lines of investigation suggest the existence of this higher-order pathological factor. (i) Right brain-damaged patients with left hemineglect may show physiological evidence of preserved processing of somatosensory stimuli, of which they are not aware. Similar results have been obtained in the visual domain. (ii) Direction-specific vestibular, visual optokinetic and somatosensory or proprioceptive stimulations may displace spatial frames of reference in right brain-damaged patients with left hemineglect, reducing or increasing the extent of the patients'' ipsilesional rightward directional error, and bring about similar directional effects in normal subjects. These stimulations, which may improve or worsen a number of manifestations of the neglect syndrome (such as extrapersonal and personal hemineglect), have similar effects on the severity of left somatosensory deficits (defective detection of tactile stimuli, position sense disorders). However, visuospatial hemineglect and the somatosensory deficits improved by these stimulations are independent, albeit related, disorders. (iii) The severity of left somatosensory deficits is affected by the spatial position of body segments, with reference to the midsagittal plane of the trunk. A general implication of these observations is that spatial (non-somatotopic) levels of representation contribute to corporeal awareness. The neural basis of these spatial frames includes the posterior parietal and the premotor frontal regions. These spatial representations could provide perceptual-premotor interfaces for the organization of movements (e.g. pointing, locomotion) directed towards targets in personal and extrapersonal space. In line with this view, there is evidence that the sensory stimulations that modulate left somatosensory deficits affect left motor disorders in a similar, direction-specific, fashion.     

Motor and Linguistic Linking of Space and Time in the Cerebellum

Background

Recent literature documented the presence of spatial-temporal interactions in the human brain. The aim of the present study was to verify whether representation of past and future is also mapped onto spatial representations and whether the cerebellum may be a neural substrate for linking space and time in the linguistic domain. We asked whether processing of the tense of a verb is influenced by the space where response takes place and by the semantics of the verb.

Principal Findings

Responses to past tense were facilitated in the left space while responses to future tense were facilitated in the right space. Repetitive transcranial magnetic stimulation (rTMS) of the right cerebellum selectively slowed down responses to future tense of action verbs; rTMS of both cerebellar hemispheres decreased accuracy of responses to past tense in the left space and to future tense in the right space for non-verbs, and to future tense in the right space for state verbs.

Conclusions

The results suggest that representation of past and future is mapped onto spatial formats and that motor action could represent the link between spatial and temporal dimensions. Right cerebellar, left motor brain networks could be part of the prospective brain, whose primary function is to use past experiences to anticipate future events. Both cerebellar hemispheres could play a role in establishing the grammatical rules for verb conjugation.     

Lateralized ultradian rhythms of the right and left brain: temporal variations of tactile discrimination tested in German subjects.

Endogenous ultradian rhythms with a periodicity of 2-3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual-spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.     

Asymmetric neural coding revealed by in vivo calcium imaging in the honey bee brain

Left–right asymmetries are common properties of nervous systems. Although lateralized sensory processing has been well studied, information is lacking about how asymmetries are represented at the level of neural coding. Using in vivo functional imaging, we identified a population-level left–right asymmetry in the honey bee''s primary olfactory centre, the antennal lobe (AL). When both antennae were stimulated via a frontal odour source, the inter-odour distances between neural response patterns were higher in the right than in the left AL. Behavioural data correlated with the brain imaging results: bees with only their right antenna were better in discriminating a target odour in a cross-adaptation paradigm. We hypothesize that the differences in neural odour representations in the two brain sides serve to increase coding capacity by parallel processing.     

Hemispheric Asymmetry in the Auditory Facilitation Effect in Dual-Stream Rapid Serial Visual Presentation Tasks

Even though auditory stimuli do not directly convey information related to visual stimuli, they often improve visual detection and identification performance. Auditory stimuli often alter visual perception depending on the reliability of the sensory input, with visual and auditory information reciprocally compensating for ambiguity in the other sensory domain. Perceptual processing is characterized by hemispheric asymmetry. While the left hemisphere is more involved in linguistic processing, the right hemisphere dominates spatial processing. In this context, we hypothesized that an auditory facilitation effect in the right visual field for the target identification task, and a similar effect would be observed in the left visual field for the target localization task. In the present study, we conducted target identification and localization tasks using a dual-stream rapid serial visual presentation. When two targets are embedded in a rapid serial visual presentation stream, the target detection or discrimination performance for the second target is generally lower than for the first target; this deficit is well known as attentional blink. Our results indicate that auditory stimuli improved target identification performance for the second target within the stream when visual stimuli were presented in the right, but not the left visual field. In contrast, auditory stimuli improved second target localization performance when visual stimuli were presented in the left visual field. An auditory facilitation effect was observed in perceptual processing, depending on the hemispheric specialization. Our results demonstrate a dissociation between the lateral visual hemifield in which a stimulus is projected and the kind of visual judgment that may benefit from the presentation of an auditory cue.     

Developmental origin of wiring specificity in the olfactory system of Drosophila

In both insects and mammals, olfactory receptor neurons (ORNs) expressing specific olfactory receptors converge their axons onto specific glomeruli, creating a spatial map in the brain. We have previously shown that second order projection neurons (PNs) in Drosophila are prespecified by lineage and birth order to send their dendrites to one of approximately 50 glomeruli in the antennal lobe. How can a given class of ORN axons match up with a given class of PN dendrites? Here, we examine the cellular and developmental events that lead to this wiring specificity. We find that, before ORN axon arrival, PN dendrites have already created a prototypic map that resembles the adult glomerular map, by virtue of their selective dendritic localization. Positional cues that create this prototypic dendritic map do not appear to be either from the residual larval olfactory system or from glial processes within the antennal lobe. We propose instead that this prototypic map might originate from both patterning information external to the developing antennal lobe and interactions among PN dendrites.