Abstract: Review about chemical information processing in insects. Integration between behavioral and neurophysiological studies to clarify in more detail the underlying mechanisms in insect olfaction

Abstract: Sensory transduction in taste and olfaction, the principal chemical senses, seems to be mediated by membrane-associated proteins on the apical surfaces of the respective receptor cells. The recent isolation and characterization of soluble 'odorant-binding proteins' secreted from the nasal glands of rat, cow and frog, led to the hypothesis that these proteins function as necessary cofactors in olfactory transduction by concentrating and delivering odorants to the receptors. The primary reception of taste stimuli occurs in specialized neuroepithelial receptor cells bundled in taste buds that are clustered in various types of papillae in the lingual epithelium of the tongue. Small tubulo-alveolar salivary glands, the von Ebner's glands, are located beneath the circumvallate and the foliate papillae. Their ducts open exclusively into the trough at the base of the papillae. Taste buds located in the medial and lateral walls of the papillae open with their taste pores into the trough and consequently are in direct contact with the secretions of von Ebner's glands. Here we report the molecular cloning and characterization of a protein of relative molecular mass 18,000 that is highly expressed in von Ebner's glands. Like the odorant-binding proteins, this protein shows similarity to members of a protein superfamily of hydrophobic molecule transporters, indicating that pre-receptor events could also be necessary for the concentration and delivery of sapid molecules in the gustatory system, and emphasizing the close relationship of taste and olfaction.

Abstract: Recent evidence shows that, despite earlier beliefs, many birds have a functional sense of smell. There is also considerable variation in olfactory-bulb size among bird species, yet the evolutionary significance of this variation has remained elusive. We argue that birds living under low-light conditions, where vision is less efficient, should have evolved or maintained an increased olfactory ability and, hence, larger olfactory bulbs. Using a family-level comparative analysis to control at least partially for taxonomic artifacts, we show that none of a series of ecological variables (diet, nest type, development, nest dispersion, and migratory behavior) accounts for variation in olfactory-bulb size once the effects of body size and brain size (measured by cerebral-hemisphere length) have been controlled. Activity timing, however, accounts for significant variation even after the removal of these other variables. We discovered 13 independent cases in which nocturnal or crepuscular lineages have evolved a diurnal habit, or vice versa, and compared relative olfactory-bulb sizes between each branch pair. In all but one case, nocturnal or crepuscular birds have larger olfactory bulbs than their diurnal counterparts. We therefore demonstrate a widespread relationship between ecology and the evolutionary development of a part of the brain.

Abstract: Within a 4-hr period after parturition, the ewe learns the odor of her lamb that will allow later recognition of her offspring from alien lamb. This study investigated the importance of the activation of olfactory bulb (OB) beta-noradrenergic receptors in establishing this olfactory memory. Pregnant ewes (n = 24) were cannulated bilaterally in the OB. Two days before parturition, OB were perfused continuously (10 microliters/hr) with either a solution containing the selective beta-noradrenergic antagonist propranolol (10(-3) M) or vehicle. The results showed that, although 8 of 9 control ewes were still able to bond selectively to their lambs, only 7 of 15 propranolol-treated animals were able to bond (p = .04). These results suggest that activation of beta-noradrenergic receptors in the OB during the period surrounding parturition is required to establish olfactory recognition of the lamb.

Abstract: Vision: Physiology, Functional Organization, Behavior and Developmental Models.- Primitive Vision Based on Sensing Change.- Pupil Control in Compound Eyes: More than One Mechanism in Moths.- Early Visual Processing in the Compound Eye: Physiology and Pharmacology of the Retina-Lamina Projection in the Fly.- Analysis of Sensory Spike Trains.- Signal Coding and Sensory Processing in the Peripheral Retina of the Compound Eye.- Dynamics of Second-Order Neurons of Cockroach Ocelli.- Processing of Movement Information in the Fly's Landing System: A Behavioral Analysis.- Motion Sensitivity in Insect Vision: Roles and Neural Mechanisms.- Response Behaviour of Elementary Movement Detectors in the Visual System of the Blowfly.- Spatial Vision in a Flat World: Optical and Neural Adaptations in Arthropods.- Search and Choice in Drosophila.- The Evolution of the Tiered Principal Retinae of Jumping Spiders (Araneae: Salticidae).- Developmental Studies on the Optic Lobe of Drosophila Using Structural Brain Mutants.- Developmental Genetic and Molecular Analyses of Lethal (1) Ogre, a Locus Affecting the Postembryonic Development of the Nervous System in Drosophila melanogaster.- Development and Fine Structure of the Nervous System of Lethal (1) Optic Ganglion Reduced Visual Mutants of Drosophila melanogaster.- Critical Developmental Phases in the Ontogeny of Human Lateral Geniculate Nucleus During Prenatal Life.- In Oculo Differentiation of Embryonic Neocortex into Retina in Adult Rat.- Axonal Outgrowth and Process Placement of Sensory Lumbar Neurons in the Nematode Caenorhabditis elegans.- Recent Progress in the Identification of Neurotransmitters Used by Vertebrate and Invertebrate Photoreceptors.- Colour Vision and Immunologically Identifiable Photoreceptor Subtypes.- Chemical Neuroanatomy of the Insect Visual System.- Olfaction and Taste: Comparisons with Other Senses, Anatomy, Physiology, Genetic Analysis, Ion Channel Models.- Insect Vision and Olfaction: Common Design Principles of Neuronal Organization.- Identified Glomeruli in the Antennal Lobes of Insects: In variance, Sexual Variation and Postembryonic Development.- Drosophila Chemoreceptors.- The Antennal Glomerulus as a Functional Unit of Odor Coding in Drosophila melanogaster.- Complex Chemical Messages in Drosophila melanogaster.- The Isolation of Antennal Mutants and Their Use in Drosophila Olfactory Genetics.- Isolation of Autosomal Behavioral Mutations in Drosophila.- Projections and Functional Implications of Labellar Neurons from Individual Sensilla of Drosophila melanogaster.- Cationic Acceptor Sites on the Labellar Chemosensory Neurons of Drosophila melanogaster.- Drosophila Homologs of Vertebrate Sodium Channel Genes.- Acoustic Perception, Mecanoreception and Nociception.- The Functional Organization of the Auditory Brainstem in the Mustache Bat and Mechanisms for Sound Localization.- Auditory Habituation and Evoked Potentials in a Learning Response.- Water Wave Analysis with the Lateral-Line System.- Functional Roles of Mechanosensory Afferents in Sequential Motor Acts During Copulation in Male Crickets.- Corrective Flight Steering in Locusts: Convergence of Extero- and Proprioceptive Inputs in Descending Deviation Detectors.- Sensory Control of Local Reflex Movements in Locusts.- Nociceptive Microcircuitry in Dorsal Horn.- Distribution and Innervation of Cuticular Sense Organs in the Scorpion, Heterometrus fulvipes.- Neural Organization of the Sensory Appendages of the Whip Scorpion Thelyphonus indicus Stoliczka (Arachnida, Uropygi).- Participants.- Glimpses of the Participants.

Abstract: 1. To determine the specificity of the goldfish (Carassius auratus) olfactory system to the reproductive pheromone 17α,20β-dihydroxy-4-pregnen-3-one (17α,20βP), and to determine if related sex steroids might also function as pheromones, electro-olfactogram (EOG) responses were recorded from mature male goldfish. 2. Of the 24 steroids tested, 17α,20βP was the most stimulatory. It had a detection threshold of 10−12M and at a concentration of 10−8M elicited an EOG response 3 times that elicited by 10−5M L-serine 3. 17α,20β,21-triol-4-pregnen-3-one, a metabolite of 17α,20βP, was the only other highly stimulatory steroid. Its threshold was 10−11M. 4. In cross-adaptation experiments EOG responses to all 21-carbon steroids were inhibited during adaptation to 17α,20βP: responses to this pheromone are transduced by a single receptor/transduction mechanism. 5. To verify the biological relevance of EOG recording whole animal responsiveness was determined by measuring blood gonadotropin. When goldfish were placed into homogeneous steroid solutions endocrine responsiveness strongly correlated with EOG recording. However, when steroids were added to aquaria containing fish, responses were less specific indicating that transient wisps of steroids trigger endocrine responses. 6. Although the extreme sensitivity and specificity of the goldfish olfactory system to 17α,20βP gives it the potential to serve as a highly specific cue, realization of this potential is probably determined by the dynamics of pheromone exposure.

Abstract: To assess the effects of low-level organic solvent exposure on olfactory function, a cross-sectional study in paint manufacturing workers was undertaken. Workers in two paint manufacturing facilities (N = 187) were tested using the University of Pennsylvania Smell Identification Test (UPSIT), a standardized, quantitative test of olfactory function. Industrial hygiene air samples over the past 13-15 years revealed that average solvent exposures in these plants were 2-40% of the existing threshold limit values for the three chemicals measured. Stratification by smoking status revealed evidence of dose-related decrements in olfactory function (p = .01) only in non-smokers. Furthermore, those nonsmoking workers in the highest exposure category had UPSIT scores below the fifth percentile for their age. These results suggest that solvents may cause nervous system dysfunction at lower levels than previously suspected, and that the olfactory system may be a critical target organ for the neurotoxic effects of solvents and other chemicals.

Abstract: The absolute olfactory sensitivity in a frui-teating bat, Carollia perspicillata, was investigated. Eighteen monomolecular food odor components from 3 substance classes were tested using a sniff rate analysis method. Detection thresholds (Table 1) ranged from 3.6 · 1013 to 2.7 · 1010 molecules/cm3 air. Interindividual variation (N = 4) for a substance did not exceed one order of magnitude. Significant correlations between olfactory performance and carbon chain length of the odor molecule were found for two substance classes: Sensitivity to the aliphatic iso-alcohols increased linearly from C2 to C5, and a nonlinear correlation was found for the acetic esters, with the C4- and C7-forms being clearly better perceived than the other homologues. In acetic esters, the sensitivity for the n-forms of the molecule was significantly higher than for the iso-forms. No such correlation between stereo-isomers and olfactory perception was found for the n- and iso-forms of carbon acids and aliphatic alcohols. Fruit-typical odor components like ethyl butyrate (5.4 · 1010), n-pentyl acetate (2.8 · 1010), or linalool (1.8 · 1011 molecules/cm3 air) were the most effective among all compounds tested, suggesting that the nutritional specialization of the bat may be associated with a specific spectrum of olfactory sensitivity.

Abstract: Eleclrophysiological recordings from single olfactory receptor cells were carried out in the male tobacco budworm moth,Heliothis virescens. Recordings were made primarily from the sensilla trichodea type 1, which are located in the characteristic circumferential rows on the antennae. They possess the longest sensilla hairs as revealed by scanning electron microscopy (SEM). The sensory cells of these sensilla responded specifically to pheromones. Only three types of receptor neurons were found, each tuned to one of the female-produced components. The majority (58%) of the neurons were tuned to the major component (Z)-11-hexadecenal (Z11-16:A1). Another large group (27%) responded specifically to stimulation with (Z)-9-tetradecenal (Z9-14: Al). These two compounds are the most important components of the pheromones as judged by their influence on the behavioral responses of the males. The third type of neurons responded specifically to (Z)-11-hexadecen-1-ol (Z11-16: OH), which may act either as a pheromone component or as an interspecific cue. None of the receptor neurons in the long sensilla trichodea responded specifically to the minor aldehyde components of the pheromone, which have subtle effects on behavior. Mixture experiments provided no evidence that minor components influence the receptor responses to the major components. Olfactory sensilla outside the crosswise rows were also characterized morphologically by SEM. Included in these were sensilla of different lengths, corresponding to a classification as s. basiconica and s. trichodea type 2. Electrophysiological recordings from these sensilla showed that they are involved primarily in host odor reception. However, a few of these neurons responded to pheromones.

Abstract: A passerine bird, the European Starling Sturnus vulgaris, demonstrated a seasonal ability to respond to odor cues. Cardiac conditioned responses were most evident when birds were in breeding condition. Once birds were in nonbreeding condition, responding to odors all but ceased. For birds in breeding condition, threshold sensitivity to the odor cyclohexanone was comparable to levels reported for nonpasserine birds (0.3% vapor saturation or 3.778 x 10(14) molecules/ml). In contrast, the threshold level during the postreproductive phase of the annual cycle was 10% vapor saturation (1.256 x 10(16) molecules/ml), a level high enough to implicate the trigeminal system as the modality mediating chemosensory perception. The strong cyclic responding pattern suggests links between photoperiodically controlled endocrine production, breeding behavior, and olfactory sensitivity.

Abstract: Two experiments investigated the effects of an actute alcohol prenatal experience during gestational Day 21 in the rat. At postnatal Days 8 and 9, this experience was sufficient to significantly increase ethanol odor preference as well as alcohol intake. Fetuses treated with a nonethanol stimulus (lemon) also exhibited changes suggesting increased lemon olfactory acceptance patterns (Exp. 1). Furthermore, when the olfactory component of the solutions experienced in utero were later paired with a novel tactile cue, responsiveness to such cue was strongly affected. Pups prenatally exposed to alcohol exhibited significantly lower tactile preference scores when texture was postnatally paired with ethanol odor when compared to specific controls. This effect was also observed in lemon-treated subjects after pairing defined by lemon-texture trials (Exp. 2). The results reported in alcohol-treated subjects appear no to be related with postabsorptive effects of the drug. It is suggested that sensory prenatal experience with alcohol is responsible for the reported changes in postnatal alcohol responsiveness patterns.

Abstract: In order to explore functional properties of the olfactory and common chemical senses as well as their relation to the total nasal sensation experienced, various concentrations of two pungent odorants were presented alone and in the presence of different backgrounds of the other irritant. Stimuli comprised formaldehyde (at 1.0, 3.5, 6.9, and 16.7 ppm), ammonia (at 210, 776, 1,172, and 1,716 ppm), and their 16 possible binary mixtures. Subjects were asked to estimate the total nasal perceived intensity, and then to assess the olfactory (odor) and common chemical (pungency) attributes of the evoked sensations. The results showed that stimulus-response functions for pungency are steeper than those for odor. Furthermore, odor was always hypoadditive in mixtures (i.e., mixtures were perceived as less intense than the sum of their components), whereas pungency was, mainly, additive, and even suggested hyperadditivity. Total perceived intensity of the stimuli, alone and in mixtures, followed the stimulus-response patterns for pungency, which, therefore, emerged as the dominating attribute used by subjects in scaling the explored range of concentrations. The relationship between total nasal perceived intensity of the mixtures and that of their components reflected hypoaddition, resembling the outcome for the odor attribute.

Abstract: It has been suggested that the olfactory bulb, the first processing center after the sensory cells in the olfactory pathway, plays a role in olfactory adaptation, odor sensitivity enhancement by motivation and other olfactory psychophysical phenomena. In a mathematical model based on the bulbar anatomy and physiology, the inputs from the higher olfactory centers to the inhibitory cells in the bulb are shown to be able to modulate the response, and thus the sensitivity of the bulb to specific odor inputs. It follows that the bulb can decrease its sensitivity to a pre-existing and detected odor (adaptation) while remaining sensitive to new odors, or increase its sensitivity to interested searching odors. Other olfactory psychophysical phenomena such as cross-adaptation etc. are discussed as well.

Abstract: As an initial effort to investigate possible inhibitory interactions in the olfactory system of the spiny lobster, studies were conducted to identify and localize the putative inhibitory neurotransmitters histamine and GABA in the olfactory lobe. Biochemical studies demonstrated that olfactory lobe tissue was capable of synthesizing histamine from radioactive histidine and GABA from glutamic acid. Immunohistochemistry was used to localize histamine and GABA in brain sections, by using either avidin-biotin conjugated peroxidase or fluorescein conjugated secondary antibody. Specific histamine-like and GABA-like immunoreactivity was found in soma clusters of olfactory interneurons, adjacent to the olfactory lobe. Small, putative glial cells displaying intense histamine-like immunoreactivity were found interspersed among the glomeruli of the lobe. The accessory lobe exhibited moderate immunostaining for both histamine and GABA. Positive immunostaining for histamine and GABA was also found in the olfactory lobes, with a predominance of staining in the outer caps of the glomeruli, which are thought to be the regions where the primary afferent terminals contact the processes of second-order olfactory neurons. These findings collectively implicate inhibition at the first synaptic level of the olfactory pathway in the spiny lobster.

Abstract: Homing behavior was tested in pigeons (Columba livia) after removing a portion of the ventrolateral telencephalon, which receives extensive projections from the olfactory bulb and is comparable with the mammalian pyriform cortex. Ablated pigeons show unaffected cardiac responses to odorous stimuli but altered homing behavior. After the operation, the birds were trained by repeated flock releases along with control birds from a site 40 km from the loft. After being released singly from this familiar site, the ablated birds turned out to be unaffected by the operation. In releases from two unfamiliar sites, ablated birds, unlike control birds, were not homeward oriented and were mostly lost. The ablation of the pyriform cortex has the same effect on homing behavior as olfactory deprivation. It can be concluded that the pyriform cortex plays an important role in the specific mechanisms linking olfactory inputs with the navigational response.

Abstract: The forebrain of primitive vertebrates is so heavily devoted to olfaction that for half a century investigators were misled into considering the function of the hippocampus as being exclusively olfactory. For example, the anterior third of the forebrain of the tiger salamander forms the bulb, the medial third is hippocampus, and the lateral third comprises the piriform and striato-amygdaloid complex (Herrick 1948). According to Herrick, a transitional zone in the mantel receives thalamic axons that convey input to the forebrain from all other sensory systems. He proposed that with the expansion and increasing dominance of these other systems, the brain expanded by adding new parts while preserving the topology of connections of those parts already existing. This view has survived to the present with modifications; it is as if, seeing that olfaction was a success, other systems moved in and co-opted the machinery of the forebrain. Olfaction remains the simplest among the sensory systems. For this reason, if for no other, the study of sensation and cognition might well begin with the sense of smell. But there are three other good reasons: the parallels that exist between olfaction and other senses in their psychophysics, in the dynamics of the masses of neurons comprising them, and in the types of neural activity that they generate.