Susan Fahrbach - Academia.edu (original) (raw)

Papers by Susan Fahrbach

The FASEB Journal

The honey bee, Apis mellifera, has long been a focus of researchers interested in pollination, be... more The honey bee, Apis mellifera, has long been a focus of researchers interested in pollination, behavioral ecology, and evolution of sociality. A distinct academic tradition rooted in the work of ethologist Karl von Frisch used the honey bee to explore learning, memory, and social communication. Humans have engaged in beekeeping for thousands of years. The separate perspectives of ecology, ethology, and apiculture provide a sturdy foundation for contemporary honey bee neurobiology. The first comprehensive study of the honey bee brain in English was published in 1896 by F.C. Kenyon. Studies in the early 1990s revealed that the brains of forager honey bees can be distinguished from those of nestmates working inside the hive by volume of neuropil associated with the protocerebral mushroom bodies. These neuropils are organized around the axons and dendrites of neurons called Kenyon cells. Subsequent studies of mushroom body plasticity documented that foraging experience drives growth of ...

PLOS ONE, Jun 6, 2012

A restrained honey bee can be trained to extend its proboscis in response to the pairing of an od... more A restrained honey bee can be trained to extend its proboscis in response to the pairing of an odor with a sucrose reward, a form of olfactory associative learning referred to as the proboscis extension response (PER). Although the ability of flying honey bees to respond to visual cues is well-established, associative visual learning in restrained honey bees has been challenging to demonstrate. Those few groups that have documented vision-based PER have reported that removing the antennae prior to training is a prerequisite for learning. Here we report, for a simple visual learning task, the first successful performance by restrained honey bees with intact antennae. Honey bee foragers were trained on a differential visual association task by pairing the presentation of a blue light with a sucrose reward and leaving the presentation of a green light unrewarded. A negative correlation was found between age of foragers and their performance in the visual PER task. Using the adaptations to the traditional PER task outlined here, future studies can exploit pharmacological and physiological techniques to explore the neural circuit basis of visual learning in the honey bee.

Arthropod Structure & Development, Sep 1, 2011

The experience of foraging under natural conditions increases the volume of mushroom body neuropi... more The experience of foraging under natural conditions increases the volume of mushroom body neuropil in worker honey bees. A comparable increase in neuropil volume results from treatment of worker honey bees with pilocarpine, an agonist for muscarinic-type cholinergic receptors. A component of the neuropil growth induced by foraging experience is growth of dendrites in the collar region of the calyces. We show here, via analysis of Golgi-impregnated collar Kenyon cells with wedge arborizations, that significant increases in standard measures of dendritic complexity were also found in worker honey bees treated with pilocarpine. This result suggests that signaling via muscarinic-type receptors promotes the increase in Kenyon cell dendritic complexity associated with foraging. Treatment of worker honey bees with scopolamine, a muscarinic inhibitor, inhibited some aspects of dendritic growth. Spine density on the Kenyon cell dendrites varied with sampling location, with the distal portion of the dendritic field having greater total spine density than either the proximal or medial section. This observation may be functionally significant because of the stratified organization of projections from visual centers to the dendritic arborizations of the collar Kenyon cells. Pilocarpine treatment had no effect on the distribution of spines on dendrites of the collar Kenyon cells.

Fahrbach SE (2023) Specialty grand challenge-Building a 21 st century community of bee physiologi... more Fahrbach SE (2023) Specialty grand challenge-Building a 21 st century community of bee physiologists to tackle 21 st century challenges to bee thriving.

Proceedings of the National Academy of Sciences of the United States of America, Mar 9, 2004

Springer eBooks, 1982

This chapter will survey current ideas on the physiological bases of maternal behavior in the rat... more This chapter will survey current ideas on the physiological bases of maternal behavior in the rat. Maternal behavior is, of course, a characteristic of all mammals, and ethological descriptions of maternal care are on record for many species (Lehrman, 1961; Klopfer, McGeorge, & Barnett, 1973). However, only a few species have been the subjects of laboratory investigations of mother-young interactions. Included among these are the rat, mouse, hamster, gerbil, rabbit, and sheep, with the rat being the best studied in terms of physiological mechanisms. This fact has determined this chapter’s emphasis, but one should not assume that the rat can serve as a general model for the regulation of maternal behavior in mammals. Striking interspecies differences, both in behavior and hormone profiles, have already been described; the significance of these differences is not yet clear.

Developmental Neurobiology, Jan 10, 2012

Enriched environmental conditions induce neuroanatomical plasticity in a variety of vertebrate an... more Enriched environmental conditions induce neuroanatomical plasticity in a variety of vertebrate and invertebrate species. We explored the molecular processes associated with experience-induced plasticity, using naturally occurring foraging behavior in adult worker honey bees (Apis mellifera). In honey bees, the mushroom bodies exhibit neuroanatomical plasticity that is dependent on accumulated foraging experience. To investigate molecular processes associated with foraging experience, we performed a time-course microarray study to examine gene expression changes in the mushroom bodies as a function of days foraged. We found almost 500 genes that were regulated by duration of foraging experience. Bioinformatic analyses of these genes suggest that foraging experience is associated with multiple molecular processes in the mushroom bodies, including some that may contribute directly to neuropil growth, and others that could potentially protect the brain from the effects of aging and physiological stress.

Journal of Neurobiology, Nov 1, 1987

The emergence of the adult Manduca sexta moth is followed by the loss of almost half of this inse... more The emergence of the adult Manduca sexta moth is followed by the loss of almost half of this insect's abdominal motoneurons and interneurons (Truman, 1983). This programmed cell death completes the transformation of the nervous system of the caterpillar into that of the moth. The death of these neurons has been previously shown to be a response to an endocrine signal: the decline in ecdysteroids that occurs at the end of metamorphosis (Truman and Schwartz, 1984). Our current research is focussed on the regulation of the fate of a pair of identified motoneurons, the MN‐12 cells, in the third abdominal ganglion. Isolation of this ganglion from anterior parts of the nervous system can prevent the death of these cells at the time when they would normally die in response to the decline in ecdysteroids. Transection of the ventral nerve cord at various levels revealed that the source of this regulatory „death signal”︁ is the fused pterothoracic ganglion and that it is transmitted via the interganglionic connectives. We hypothesize that the factors mediating this effect may act in concert with the ecdysteroid decline to specify the exact time of death for individual neurons.

Experimental Brain Research, Sep 1, 1989

The afferent neural connections of the ventromedial nucleus of the rat hypothalamus (VMH) have be... more The afferent neural connections of the ventromedial nucleus of the rat hypothalamus (VMH) have been studied in detail using three horseradish peroxidase (HRP) application methods: HRP crystal implants, HRP-gel implants, and iontophoretic deposition of the enzyme. Examination of the cases in which the retrograde tracer was best confined to various subdivisions of the nucleus revealed that the septal area projects only to the ventrolateral VMH, and that the medial preoptic area, rostral lateral hypothalamus, and the ventral subiculum project mainly to the ventrolateral VMH. Thus, the subdivision of the VMH that contains the highest density of estradiol-concentrating neurons (Morrell et al. 1986) receives a larger set of inputs than the rostral and central parts of the nucleus. The central subdivision receives a more restricted set of projections than either the medial or the lateral regions. These studies suggest that there may be partial anatomical segregation of neural inputs to the various subdivisions of the VMH.

Journal of Neurobiology, Oct 6, 2003

The behavioral maturation of adult worker honey bees is influenced by a rising titer of juvenile ... more The behavioral maturation of adult worker honey bees is influenced by a rising titer of juvenile hormone (JH), and is temporally correlated with an increase in the volume of the neuropil of the mushroom bodies, a brain region involved in learning and memory. We explored the stability of this neuropil expansion and its possible dependence on JH. We studied the volume of the mushroom bodies in adult bees deprived of JH by surgical removal of the source glands, the corpora allata. We also asked if the neuropil expansion detected in foragers persists when bees no longer engage in foraging, either because of the onset of winter or because colony social structure was experimentally manipulated to cause some bees to revert from foraging to tending brood (nursing). Results show that adult exposure to JH is not necessary for growth of the mushroom body neuropil, and that the volume of the mushroom body neuropil in adult bees is not reduced if foraging stops. These results are interpreted in the context of a qualitative model that posits that mushroom body neuropil volume enlargement in the honey bee has both experience‐independent and experience‐dependent components. © 2003 Wiley Periodicals, Inc. J Neurobiol 57:141–151, 2003

The Journal of Neuroscience, Aug 15, 2001

A worker honeybee performs tasks within the hive for approximately the first 3 weeks of adult lif... more A worker honeybee performs tasks within the hive for approximately the first 3 weeks of adult life. After this time, it becomes a forager, flying repeatedly to collect food outside of the hive for the remainder of its 5-6 week life. Previous studies have shown that foragers have an increased volume of neuropil associated with the mushroom bodies, a brain region involved in learning, memory, and sensory integration. We report here that growth of the mushroom body neuropil in adult bees occurs throughout adult life and continues after bees begin to forage. Studies using Golgi impregnation asked whether the growth of the collar region of the mushroom body neuropil was a result of growth of the dendritic processes of the mushroom body intrinsic neurons, the Kenyon cells. Branching and length of dendrites in the collar region of the calyces were strongly correlated with worker age, but when age-matched bees were directly compared, those with foraging experience had longer, more branched dendrites than bees that had foraged less or not at all. The density of Kenyon cell dendritic spines remained constant regardless of age or behavioral state. Older and more experienced foragers therefore have a greater total number of dendritic spines in the mushroom body neuropil. Our findings indicate that, under natural conditions, the cytoarchitectural complexity of neurons in the mushroom bodies of adult honeybees increases as a function of increasing age, but that foraging experience promotes additional dendritic branching and growth.

PLOS ONE, Dec 26, 2023

Organic volatiles produced by fruits can result in overestimation of sweetness by humans, but it ... more Organic volatiles produced by fruits can result in overestimation of sweetness by humans, but it is unknown if a comparable phenomenon occurs in other species. Honey bees collect nectar of varying sweetness at different flowering plants. Bees discriminate sugar concentration and generally prefer higher concentrations; they encounter floral volatiles as they collect nectar, suggesting that they, like humans, could be susceptible to sweetness enhancement by odorant. In this study, limonene, linalool, geraniol, and 6-methyl-5-hepten-2-ol were tested for their ability to alter behaviors related to perception of sweetness by honey bees. Honey bees were tested in the laboratory using proboscis extension responsebased assays and in the field using feeder-based assays. In the laboratory assays, 6methyl-5-hepten-2-ol and geraniol, but neither linalool nor limonene, significantly increased responses to low concentrations of sucrose compared with no odorant conditions in 15-day and 25-day-old adult worker honey bees, but not in 35-day-old bees. Limonene reduced responding in 15-day-old bees, but not in the older bees. There was no odorant-based difference in performance in field assays comparing geraniol and limonene with a no odorant control. The interaction of the tested plant volatiles with sucrose concentration revealed in laboratory testing is therefore unlikely to be a major determinant of nectar choice by honey bees foraging under natural conditions. Because geraniol is a component of honey bee Nasonov gland pheromone as well as a floral volatile, its impact on responses in the laboratory may reflect conveyance of different information than the other odorants tested.

Journal of the Acoustical Society of America, Jun 1, 1977

S29 93rd Meeting: Acoustical Society of America S29 ground noise, L1, and that of the high-passed... more S29 93rd Meeting: Acoustical Society of America S29 ground noise, L1, and that of the high-passed masker. Lh. The performance of each of three listeners was vii•tually identical in a 4 IFC adaptive psychophysical procedureø Whenf s <>fc masking was influenced only by Lb. However, whenfs •f½ masking appeared to be related to the sum of the sound pr,essures contributed by L 1 and L• within a critical band, CB. Variation in L• yielded no change in the shape of the masking function as long as L•-L 1 was constant. The frequency region belowf½ within which Ln influenced masking increased as L 1 decreased relative to Lh. This could be interpreted as a widening of the CB or perhaps a manifestation of Greenwood's [J. Acoust. Soc. Am. 50, 502-543 (1971)] combinational aggregate. 3:0O 05. Binaural critical masking bands. J.C. Sever, Jr. (Department of Speech, Arts and Sciences Bldg. 461. University

University of Chicago Press eBooks, 2009

... Coss et al. 1980; Brandon and Coss 1982; G. Robinson et al. 1989; G. Robinson 1992). The 1993... more ... Coss et al. 1980; Brandon and Coss 1982; G. Robinson et al. 1989; G. Robinson 1992). The 1993 and 1994 papers inspired numerous follow-up studies. Another region ... Winnington et al. 1996; Sigg et al. 1997). Other studies ...

Seminars in Neuroscience, Dec 1, 1991

Changes in the structure and function of identified neurons during insect metamorphosis that are ... more Changes in the structure and function of identified neurons during insect metamorphosis that are linked to the gain or loss of specific elements of behavior are controlled by the steroid hormone, 20-hydroxyecdysone. Three approaches are being used to determine which cells are primary targets for steroid hormones: localized hormone manipulations, direct exposure of identified neurons to ecdysteroids in vitro and steroid hormone autoradiography. Identified neurons display an array of responses to steroids, which may have different thresholds and be subject to other regulatory influences. The current challenge is to link our understanding of the hormonally dependent cellular changes in identified neurons to emerging information about the molecular basis of ecdysteroid action and the regulation of cell fate in insects .

Journal of insect science, Jul 1, 2011

Journal of Insect Physiology, May 1, 2009

Large bumblebee (Bombus terrestris) workers typically visit flowers to collect pollen and nectar ... more Large bumblebee (Bombus terrestris) workers typically visit flowers to collect pollen and nectar during the day and rest in the nest at night. Small workers are less likely to forage, but instead stay in the nest and tend brood around the clock. Because Pigment Dispersing Factor (PDF) has been identified as a neuromodulator in the circadian network of insects, we used an antiserum that recognizes this peptide to compare patterns of PDF-immunoreactivity (PDF-ir) in the brains of large and small workers. Our study provides the first description of PDF distribution in the bumblebee brain, and shows a pattern that is overall similar to that of the honey bee, Apis mellifera. The brains of large bumblebee workers contained a slightly but significantly higher number of PDF-ir neurons than did the brains of small sister bees. Body size was positively correlated with area of the PDF-ir somata and negatively correlated with the maximal staining intensity. These results provide a neuronal correlate to the previously reported body sizeassociated variation in behavioral circadian rhythmicity. These differences in PDF-ir are consistent with the hypothesis that body size-based division of labor in bumblebees is associated with adaptations of the morphology and function of the brain circadian system.

Neuroscience Letters, Nov 1, 1997

The mushroom bodies (MB), the insect brain structures most often associated with learning, have p... more The mushroom bodies (MB), the insect brain structures most often associated with learning, have previously been shown to exhibit structural plasticity during the adult behavioral development of female worker and queen honey bees. We now show that comparable morphological changes occur in the brains of male honey bees (drones). The volume of the MB in the brains of drones was estimated from tissue sections using the Cavalieri method. Brains were obtained from six groups of drones that differed in age and flight experience. Circulating levels of juvenile hormone (JH) in these drones were determined by radioimmunoassay (RIA). There was an expansion of the neuropil of the MB that was temporally associated with drone behavioral development, as in female queens and workers. The observed changes in drones were maintained in the presence of low levels of JH, also as in females. These results suggest that expansion of the neuropil of the MB in honey bees is associated with learning the location of the nest, because this learning is the most prominent aspect of behavioral development common to all members (workers, drones, queen) of the honey bee colony.