Peppermint Odor Research Articles

Wolbachia-Driven Memory Loss in a Parasitic Wasp Increases Superparasitism to Enhance Horizontal Transmission.

Horizontal transmission of the endosymbiont, Wolbachia, may occur during superparasitism when parasitoid females deposit a second clutch of eggs on a host. Wolbachia may increase the superparasitism tendency of Trichogramma wasps by depriving their memory. To test this hypothesis, we investigated the effects of conditioning experience and memory inhibitors (actinomycin D [ACD] and anisomycin [ANI]) on memory capacity, and expressions of memory-related genes (CREB1 and PKA), and superparasitism frequency of Wolbachia-infected (TDW) and uninfected (TD) lines of Trichogramma dendrolimi after conditioning with lemon or peppermint odor. We detected the presence of Wolbachia in eggs, larvae, pre-pupae, pupae, and adults of Trichogramma by using fluorescence in situ hybridization. The results showed that TDW females had a more reduced memory capacity than TD females after conditioning. Compared with TD females, TDW females showed a higher proportion of superparasitism and a downregulation of CREB1 and PKA genes after conditioning. TD females fed ACD or ANI showed a higher tendency for superparasitism and a downregulation of CREB1 and PKA, along with memory loss after conditioning than TD females fed honey solution only. The presence of Wolbachia was detected in the anterior region of the larva, pre-pupa, and pupa, but was not found in the head of the adult. The results provide evidence of host behavioral manipulation of Wolbachia by depriving memory of host Trichogramma wasps based on Poulin' s criteria. These host behavioral changes led by Wolbachia may be caused by the virulence of Wolbachia on the nervous system of the host. IMPORTANCE The endosymbiotic bacteria, Wolbachia, live widely within cells of arthropods. Wolbachia are not only transmitted vertically from host mother to offspring, but are also transmitted horizontally among host individuals. Horizontal transmission is expected to occur during superparasitism when host parasitoid females deposit a clutch of eggs on a host previously parasitized by the same parasitoid species. Thus, a question is proposed regarding whether superparasitism behavior is a behavior modification induced by the symbiont to favor symbiont transmission. This study highlights behavioral mechanisms of Wolbachia-induced superparasitism in Trichogramma wasps and the manipulation of symbionts on host parasitoids.

Cues Associated with Social Defeat Stress Recruit CRF in the Nucleus Accumbens and Invigorate Drug‐Seeking following Abstinence from Cocaine

Cocaine‐dependent individuals experience intense drug cravings in anticipation of imminent drug availability. Notably, acute stressors can further exacerbate the heightened state of arousal produced by drug‐related stimuli and increase propensity to seek and consume drug – rendering individuals highly susceptible to relapse. The present studies extend ongoing work examining the stress peptide corticotropin releasing factor (CRF) as a candidate mechanism for maladaptive arousal evoked by drug‐predictive stimuli. In rats, CRF enhances instrumental behavior directed towards gaining access to cocaine, in part through local control of DA transmission in the nucleus accumbens (NAc). Because CRF modulates motivational states in both appetitive and aversive contexts, we explored the extent to which an ecologically relevant stressor (ie social defeat) augments cocaine self‐administration under a chained operant response sequence (ie seeking‐taking), and whether NAc‐CRF is recruited. On alternating days, male Long‐Evans rats were exposed to acute social defeat in the presence of a compound stimulus (CS+: peppermint odor + 3kHz tone) or placed in an empty cage (CS‐: almond odor + 25kHz tone) for 4 sessions each. Microdialysis conducted in the presence of the conditioned cues revealed that the stress‐CS+ produced a rapid increase in both CRF and DA in the NAc, which was temporally distinct from a delayed rise in corticosterone. Separate rats were trained to self‐administer cocaine under a chained schedule of reinforcement (FI‐FR) in order to dissociate anticipatory (‘drug‐seeking’) from consummatory (‘drug‐taking’) behavior. Completion of a fixed‐interval (5m) produced access to continuous cocaine reinforcement (FR1) on a separate lever (5m). Here, accelerating responding across the FI captures an index of arousal in anticipation of impending drug‐availability – ostensibly, when craving is heightened. After a 7d drug‐free (ABST) period, rats were reintroduced to the drug context to self‐administer cocaine in the presence of either the stress‐paired stimuli (CS+) or neutral cues (CS‐) in a counterbalanced manner. Compared to pre‐ABST baseline, responding during the FI was elevated under both stimulus conditions, presumably reflecting an “incubation”‐like enhancement of behavior. Critically, CS+ exposure produced significantly higher anticipatory responding for cocaine than the neutral condition (CS+> CS‐ > Baseline), suggesting that stress stimuli augmented the effects of ABST. Cocaine intake was unaffected by either condition. These data support the concept that environmental stressors can amplify the impact of being re‐exposed to a drug‐context after a period of abstinence, such to invigorate putative “drug‐seeking” behavior. Anticipation of threat may engage common motivational salience circuits that generate arousal during cocaine expectation, whereas the unconditioned aspects of drug‐reward are differentially controlled. Ongoing studies seek to further clarify the functional role of stress‐evoked NAc‐CRF in cocaine‐related behavior.

Frontal medial cortex and angular gyrus functional connectivity is related to sex and age differences in odor sensitivity

Odor preference is one of the key factors for the rehabilitation of the swallowing function. On the other hand, sensitivity to odor differs between sexes and decreases with age. These factors rely on brain neuronal circuits. However, it remains not fully clarified which neuronal circuit determines the sex and age differences in odor sensitivity. In this study, we carried out both the odor sensitivity test and functional MRI (fMRI) to find the key neuronal circuits determining sex and age differences in odor sensitivity. Healthy volunteers (28 males, aged 27-62 years, and 30 females, aged 21-59 years) participated in this study. Some of them (seven males and seven females) underwent fMRI. We prepared five odorous test substances and presented each substance at 1 minute intervals. After 5 minutes of questioning about food intake, the subjects were asked to recall each of the test substances presented from the list. In the fMRI study, all the subjects underwent 15 minutes of the prestimulation, stimulation with peppermint odor, and poststimulation sessions. The odor test score was significantly higher in females than in males and showed an age-dependent decrease. We found four functional connectivities whose degrees were significantly different between males and females. One of them, the functional connectivity between the frontal medial cortex (MedFC) and the left angular gyrus (AG. l), showed an age-dependent change. The functional MedFC-AG.l connectivity is one of the important neuronal circuits that affect the sex- and age-dependent odor sensitivity.

Major Sensory Attributes and Volatile Compounds of Korean Rice Liquor (yakju) Affecting Overall Acceptance by Young Consumers.

The sensory characteristics and volatile compounds that affect consumers’ acceptance of rice liquors were investigated. A total of 80 consumers evaluated 12 yakju samples and descriptive analysis by 11 trained panelists was conducted. Solvent-assisted flavor evaporation-gas chromatography-mass spectrometry analysis also was conducted revealing 120 volatile compounds in the yakju samples. Sensory attributes (n = 31) except appearance attributes were used for principal component analysis (PCA). As results, fruit odor (apple, hawthorn, omija, and pineapple odor) and flower odor (chrysanthemum, pine, and peppermint odor) were placed on the positive side of PC1 whereas persimmon vinegar odor, bitter taste, alcohol flavor, stinging and coating mouthfeel were located on the negative side of PC1. The yakju samples were mainly characterized by their alcohol content and supplementary ingredients. Sensory descriptors (n = 31; except appearance attributes and p > 0.05) and volatile compounds (n = 30; p > 0.5 correlation coefficient with overall acceptance) were chosen for multiple factor analysis (MFA). The MFA correlation map showed that ethyl propanoate, ethyl-2-hydroxy-2-methylbutanoate, methyl 2-furoate, γ-butyrolactone, 4-ethoxycarbonyl-γ-butyrolactone, hawthorn odor, apple flavor, grape flavor, and sweet taste were positively correlated with young consumers’ overall acceptance. Additionally, negative correlation with overall acceptance was found in 1,3-butanediol, 2,3-butanediol, and 1,1-diethoxy-3-methylbutane.

Olfactory Facilitation of Takeover Performance in Highly Automated Driving

This study aims to quantify the impact of olfactory stimulation and takeover modality on the performance of takeovers in conditionally automated driving. Takeover requests are important for the safety of automated vehicles. The reaction time and subsequent performance of drivers in the takeover process are crucial for safety. In this study, peppermint was adopted as an auxiliary modality to the tactile and auditory design of takeover requests. Sixty participants took part in the experiment, which required participants to avoid a stalled vehicle after they were awoken from a state of light sleep by a takeover request. Takeover modality (tactile, auditory, and combined) was the within-subjects factor. In the between-subjects design, half of the participants received a peppermint odor stimulation when the takeover request occurred, and the other half received a placebo (air). The presence of peppermint odor did not influence the reaction time, but participants did show signs of being more alert afterwards. For the moment of takeover, use of the auditory modality had a significant positive effect on reaction time compared to the tactile conditions. Peppermint odor had a positive impact on drivers' takeover quality when engaged in nondriving-related activities such as light sleep, and the takeover request modalities were shown to be crucial for a safe and successful takeover. The results will be useful as a reference for developers of automated driving systems to design human-machine interfaces, shorten the driver's reaction time, and improve takeover quality.

Peppermint Ambient Odor Affects Cortisol Secretion And Task Performance In Selected Tests In School Children

Federation There is a growing set of evidences that ambient odors of essential oils have various effects on human mood, behavior and physiological state. A very little published about the impact of odors on behavior and physiology of children though it is known that children surpass adults in the ability to detect and recognize odors, describe their perceptions and preferences. The aim of our study: to evaluate the effect of low concentrations (~ 0.13 mg/m3) of peppermint oil (Sigma‐ Aldrich) on the performance of school ‐ children (age 10–11) in the course of ordinary lessons and investigate possible mechanisms underlying the effects. Among different school tests we selected arithmetic dictationtest which mainly relies on memory retrieval process. During 15 minutes the teacher dictates with pauses 8 short math exercises, adapted to the student's grade. Students write down only the answers in the corresponding order. Each experiment was set as a series of control tests with no odor alternated with tests accompanied by exposures to peppermint oil. We recorded number of errors and self‐corrections. Saliva cortisol was monitored using an ELISA technique (EIA Can‐C‐290, DBC). Individual saliva samples were taken every 15 minutes during control lesson (no odor, 45 min) and during experimental lesson (peppermint, 45 min). For the reference we also collected in identical manner individual saliva samples from adult students (age 18–21 years, n=20). All samples were kept frozen (‐30°C) until analyzed. All experiments were performed at the same time of the day. Peppermint improved performance in children (age 10–11) in arithmetic dictation test causing a significant decrease in number of mistakes as well as in number of self‐corrections. This effect was highly significant (p < 0.001, n=51) and confirmed by observations in different independent groups: students of 5‐th grade (p < 0.001, n= 25) and students of 6‐th grade (p < 0.001, n=30) as well as by repeated observations (n=3) in the same group. In our previous research (Rodionova, Minor, 2017) peppermint odor also improved performance of children (8–9 years old) in another test ‐ word dictation but not in text copying test. Word dictation and arithmetic dictation tests depend both on memory retrieval process while text copying test relies mostly on the attention. Saliva cortisol was significantly lowered by peppermint odor in children of both sexes (p< 0.001, n=14) while in adults we observed significant drop of cortisol only in female students (p< 0.01, n=10). In adult male students we did not observe changes of cortisol secretion under peppermint exposure (p>0.05, n=10). Stressful events are very common in educational settings. Stress markedly impairs memory retrieval (Vogel, Schwabe, 2016). We hypothesize that peppermint odor may facilitate memory retrieval by lowering cortisol which results in improved performance in word dictation and arithmetic dictation tests.Support or Funding InformationSupported by Russian Science Foundation 16‐15‐10312This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Epigenetic Modifications in the Rat Neonate Olfactory Bulb and Anterior Piriform Cortex Associated with Olfactory and Tactile Experiences

Rodents are macrosmatic; they depend heavily on the olfactory system, which includes the olfactory bulb and anterior piriform cortex, to navigate their environment. The olfactory system is key to the survival of neonatal pups in order to learn the scents of the dam, which aid in nipple attachment and overall attachment to the caregiver. This attachment‐based learning was mimicked in rodents using a laboratory‐based experimental design in which neonatal pups were classically conditioned to associate the novel scent of peppermint with stroking, an action that mimics sensory cues associated with caregiving. The effects of attachment‐based learning on mRNA levels of epigenetic regulators, as well as epigenetic modifications of Bdnf and Reln, genes involved in neuroplasticity, are unknown.We investigated changes in gene expression of Bdnf, Reln, and epigenetic regulators (DNMT1, DNMT3a, DNMT3b, HDAC1, HDAC2, HDAC5, TET1, Gadd45B, and MeCP2) following infant olfactory learning. Using an odor‐stroke paradigm, Long‐Evans rat pups (postnatal days 6 or 7) (n=46) were assigned to either a paired (simultaneous peppermint odor and stroking), unpaired (non‐simultaneous peppermint odor and stroking), or odor‐/stroke‐only condition. Brains were harvested 30 minutes after conditioning. Using Real‐time PCR, we found experience‐induced changes in gene expression profiles in both brain regions. For example, Bdnf exon IV gene expression in the olfactory bulb significantly increased in rats that received contiguous presentation of both stimuli; however, gene expression of HDAC2, HDAC5, TET1, and Gadd45B significantly decreased in the same subjects. In the anterior piriform cortex, there were significant increases in gene expression of Bdnf exons I and IV, DNMT3b, and Gadd45B in both paired and unpaired subjects. Understanding the unknown epigenetic modifications involved in attachment‐based learning may elucidate the mechanisms of the emotional connection an infant learns for the caregiver and its profound influence on neurological development.Support or Funding InformationSpecial thanks to Dr. Roth and Tiffany Doherty for their support and guidance along with Lauren Webb's and Tiffany's completion of odor‐stroke conditioning. This research is funded through grants P20GM103653, R01HD087509, and private donation funds to Dr. Roth.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Histone deacetylase inhibition induces odor preference memory extension and maintains enhanced AMPA receptor expression in the rat pup model.

Histone deacetylase (HDAC) plays a role in synaptic plasticity and long-term memory formation. We hypothesized that trichostatin-A (TSA), an HDAC inhibitor, would promote long-term odor preference memory and maintain enhanced GluA1 receptor levels that have been hypothesized to support memory. We used an early odor preference learning model in neonate rat pups that normally produces only 24-h memory to test behavior and examine receptor protein expression. Our behavioral studies showed that intrabulbar infusion of TSA, prior to pairing of the conditioned stimulus (peppermint odor) with the unconditioned stimulus (tactile stimulation), prolonged 24-h odor preference memory for at least 9 d. The prolonged odor preference memory was selective for the paired odor and was also observed using a specific HDAC6 inhibitor, tubacin, supporting a role for histone acetylation in associative memory. Immunoblot analysis showed that GluA1 receptor membrane expression in the olfactory bulbs of the TSA-treated group was significantly increased at 48 h unlike control rats without TSA. Immunohistochemistry revealed significant increase of GluA1 expression in olfactory bulb glomeruli 5 d after training. These results extend previous evidence for a close relationship between enhanced GluA1 receptor membrane expression and memory expression. Together, these findings provide a new single-trial appetitive model for understanding the support and maintenance of memories of varying duration.

Effect of ambient odor on cognitive functions in children

We studied the effect of the peppermint ambient odor on the performance of routine Russian school language tests by primary-school students in a standard classroom, where a noiseless source of odor provided scenting the air by means of free evaporation of the essential oil at a constant low concentration. It is shown that in the presence of peppermint odor the marks for a word dictation test that is based on the longterm memory are significantly higher than in the absence of the odor, whereas the performance of text copying test (based mainly on attention) is not influenced by the presence of peppermint odor.

Effects of Peppermint Odor on Performance and Fatigue in a Simulated Air Traffic Control Task

Effects of Peppermint Odor on Performance and Fatigue in a Simulated Air Traffic Control Task

Odor-induced modulation of electroencephalogram waves in healthy controls

Background: It has been found in some of the electrophysiological studies that odor does affect the rhythm of brain waves. However, there is a lot of inconsistency in terms of the reported findings. Some have reported an increase in alpha activity, whereas others observed increase in theta activity and no change in alpha. Aims and Objectives: The purpose of this study is to observe what changes occur in electroencephalogram (EEG) in healthy participants on administration of two types of odor (lavender and peppermint). Materials and Methods: This study was conducted on 25 healthy, right-handed male and female volunteers. Baseline EEG for 20 min was recorded, followed by test recording for 9 min comprising inhalation of odor 1 (lavender) for 3 min, no odor (for 3 min), and odor 2 (peppermint) for 3 min. Odors were administered through an odor delivery system, which comprised an inlet and outlet rubber tubes connected to a container for placing odoriferous substance. Results: EEG was inspected qualitatively for abnormalities in prominent locations and hemisphere. Both the odors elicited significant EEG abnormalities when compared to baseline recording, which served as control. Odor 1 and 2 both elicited diffuse slowing, focal slowing, and sharp waves mainly in temporal region and partly in centro-parietal and frontotemporal region, with more right hemispherical involvement, and increased theta rhythm. Odor 2 also produced left hemisphere dominant asymmetry. Conclusions: Both lavender and peppermint odor inhalation produces EEG abnormalities which are transient, predominantly affect right hemisphere, and temporal region. Lavender has relatively more relaxing effect on brain compared to peppermint.

Humans, Rodents Pay Close Attention to Fear, Anxiety Expressed by Parents

Back to table of contents Previous article Next article Clinical and Research NewsFull AccessHumans, Rodents Pay Close Attention to Fear, Anxiety Expressed by ParentsAaron LevinAaron LevinSearch for more papers by this authorPublished Online:4 Jun 2015https://doi.org/10.1176/appi.pn.2015.6a3AbstractThe neurobiology of intergenerational transmission of emotional trauma suggests a social, and not genetic, mechanism.“Fear is a social phenomenon, especially among humans, and social context affects fear acquisition,” Jacek Debiec, M.D., Ph.D., a professor of psychiatry at the University of Michigan, told attendees of the 10th Annual Amygdala, Stress, and PTSD Conference at the Uniformed Services University in Bethesda, Md., in April.Rats and humans both use social referencing to learn fear and safety, basing their response on that of a trusted caretaker, says Jacek Debiec, M.D., Ph.D., a professor of psychiatry at the University of Michigan.Aaron LevinDebiec, who treats children and mothers with anxiety and other conditions and studies the neurobiological mechanisms of emotional learning in rodents, described how his research into fear transmission in rodents suggests that infants pick up on their mother’s fear response early in life. Similar findings have been found in humans, Debiec noted, pointing to the recent study of human twins in Sweden that suggested that children and adolescents learn anxious behavior from their parents .The interest in intergenerational transmission of fear and anxiety began many decades ago with Holocaust studies, said Debiec.“Psychiatrists recognized that the children of Holocaust survivors exhibited symptoms of what is now called PTSD,” he said. “The children did not meet all the criteria, but there was something dysfunctional going on.”While there are many possible mechanisms for such transmission of fear, Debiec’s recent experiments using smell to look at fear conditioning in rats highlight the role of the social transmission of fear from a mother to her pups. Like many species (including humans), rats regulate their behavior by observing their caregivers’ emotional expression during novel situations. In a study published August 19, 2014, in the Proceedings of the National Academy of Sciences (PNAS), Debiec and colleagues described how they taught female rats to fear the smell of peppermint—an odor that is typically neutral for rats—by linking it with an electric foot shock before the animals became pregnant. After the animals gave birth, the researchers once again exposed the mothers to peppermint, but without the shocks, in order to provoke the fear response.If the mother was not re-exposed to the peppermint or had not been conditioned to fear the odor, infant rats did not exhibit avoidance to the peppermint odor. However, when the pups were exposed to the freezing reactions of their fear-conditioned mothers to the peppermint scent, the pups also learned to avoid the smell. The fear-conditioned mothers were later less nurturing to the pups than control animals as well.The pups did not even need to be around their mother when she smelled the peppermint odor—simply catching a whiff of the scent of their mother reacting to the odor was enough to make them fear the same thing. According to the researchers, the pups’ fear response continued through adolescence.Further investigation showed that both the olfactory bulb and the amygdala play a role in this process. Inactivating the amygdala with the GABA-A receptor agonist muscimol prevented the transmission of fear from the mother to the pup; noradrinergic blockade with propanolol did the same.Similar to Debiec’s findings of the social transmission of fear from mothers to pups, a twin study published April 23 in AJP in Advance suggests that children model the anxious behavior of their parents.“The association between parental and offspring anxiety largely arises because of a direct association between parents and their children independent of genetic confounds,” concluded Thalia Eley, Ph.D., a professor of developmental behavioral genetics in the Institute of Psychiatry at King’s College London, and colleagues.During his talk, Debiec described how powerful social fear learning is, how early on in life it occurs, and how long it lasts. “Babies learn from parents about threats before they can even fully express fear to these threats,” he said. “The young organism has to rely on emotion conveyed by caretakers when young to learn about what is safe and not safe about the world, but in situations where the caretaker is traumatized, the perspective is distorted, the response is not adaptive.” ■“Intergenerational Transmission of Emotional Trauma Through Amygdala-Dependent Mother-to-Infant Transfer of Specific Fear” can be accessed here. “The Intergenerational Transmission of Anxiety: A Children-of-Twins Study” is available here. ISSUES NewArchived

Why Do Children Wish to Stay with Their Abusers? A Translational Study

Abused children often choose, counterintuitively, to stay with their abusing parents even during court proceedings offering placement outside the home. To study the pathophysiology of this phenomenon, investigators used an animal model in which infant rats are introduced to and bond with a peppermint odor (an established substitute for maternal odor) …

Visualizing the engram: learning stabilizes odor representations in the olfactory network.

The nature of memory is a central issue in neuroscience. How does our representation of the world change with learning and experience? Here we use the transcription of Arc mRNA, which permits probing the neural representations of temporally separated events, to address this in a well characterized odor learning model. Rat pups readily associate odor with maternal care. In pups, the lateralized olfactory networks are independent, permitting separate training and within-subject control. We use multiday training to create an enduring memory of peppermint odor. Training stabilized rewarded, but not nonrewarded, odor representations in both mitral cells and associated granule cells of the olfactory bulb and in the pyramidal cells of the anterior piriform cortex. An enlarged core of stable, likely highly active neurons represent rewarded odor at both stages of the olfactory network. Odor representations in anterior piriform cortex were sparser than typical in adult rat and did not enlarge with learning. This sparser representation of odor is congruent with the maturation of lateral olfactory tract input in rat pups. Cortical representations elsewhere have been shown to be highly variable in electrophysiological experiments, suggesting brains operate normally using dynamic and network-modulated representations. The olfactory cortical representations here are consistent with the generalized associative model of sparse variable cortical representation, as normal responses to repeated odors were highly variable (∼70% of the cells change as indexed by Arc). Learning and memory modified rewarded odor ensembles to increase stability in a core representational component.

Intergenerational transmission of emotional trauma through amygdala-dependent mother-to-infant transfer of specific fear.

Emotional trauma is transmitted across generations. For example, children witnessing their parent expressing fear to specific sounds or images begin to express fear to those cues. Within normal range, this is adaptive, although pathological fear, such as occurs in posttraumatic stress disorder or specific phobias, is also socially transmitted to children and is thus of clinical concern. Here, using a rodent model, we report a mother-to-infant transfer of fear to a novel peppermint odor, which is dependent on the mother expressing fear to that smell in pups' presence. Examination of pups' neural activity using c-Fos early gene expression and (14)C 2-deoxyglucose autoradiography during mother-to-infant fear transmission revealed lateral and basal amygdala nuclei activity, with a causal role highlighted by pharmacological inactivation of pups' amygdala preventing the fear transmission. Maternal presence was not needed for fear transmission, because an elevation of pups' corticosterone induced by the odor of the frightened mother along with a novel peppermint odor was sufficient to produce pups' subsequent aversion to that odor. Disruption of axonal tracts from the Grueneberg ganglion, a structure implicated in alarm chemosignaling, or blockade of pups' alarm odor-induced corticosterone increase prevented transfer of fear. These memories are acquired at younger ages compared with amygdala-dependent odor-shock conditioning and are more enduring following minimal conditioning. Our results provide clues to understanding transmission of specific fears across generations and its dependence upon maternal induction of pups' stress response paired with the cue to induce amygdala-dependent learning plasticity. Results are discussed within the context of caregiver emotional responses and adaptive vs. pathological fears social transmission.

Unlearning: NMDA Receptor-Mediated Metaplasticity in the Anterior Piriform Cortex Following Early Odor Preference Training in Rats

Here we demonstrate metaplastic effect of a change in NMDA receptor (NMDAR) number in the anterior piriform cortex (aPC) in rat induced by a 10 min pairing of peppermint odor + stroking, which significantly modifies later learning and memory. Using isolated synaptoneurosomes, we found NR1 receptor downregulation 3 h after training and upregulation at 24 h. Consistent with the NR1 pattern, the NMDAR-mediated EPSP was smaller at 3 h and larger at 24 h. Subunit composition was unchanged. Whereas LTP was reduced at both times by training, LTD was facilitated only at 3 h. Behaviorally, pups, given a pairing of peppermint + stroking 3 h after an initial peppermint + stroking training, lost the normally acquired peppermint preference 24 h later. To probe the pathway specificity of this unlearning effect, pups were trained first with peppermint and then, at 3 h, given a second training with peppermint or vanillin. Pups given peppermint training at both times lost the learned peppermint preference. Pups given vanillin retraining at 3 h had normal peppermint preference. Downregulating NR1 with siRNA prevented odor preference learning. Finally, the NMDAR antagonist MK-801 blocked the LTD facilitation seen 3 h after training, and giving MK-801 before the second peppermint training trial eliminated the loss of peppermint odor preference. A training-associated reduction in NMDARs facilitates LTD 3 h later; training at the time of LTD facilitation reverses an LTP-dependent odor preference. Experience-dependent, pathway-specific metaplastic effects in a cortical structure have broad implications for the optimal spacing of learning experiences.

Neurobiology of secure infant attachment and attachment despite adversity: a mouse model

Attachment to an abusive caregiver has wide phylogenetic representation, suggesting that animal models are useful in understanding the neural basis underlying this phenomenon and subsequent behavioral outcomes. We previously developed a rat model, in which we use classical conditioning to parallel learning processes evoked during secure attachment (odor-stroke, with stroke mimicking tactile stimulation from the caregiver) or attachment despite adversity (odor-shock, with shock mimicking maltreatment). Here we extend this model to mice. We conditioned infant mice (postnatal day (PN) 7-9 or 13-14) with presentations of peppermint odor and either stroking or shock. We used (14) C 2-deoxyglucose (2-DG) to assess olfactory bulb and amygdala metabolic changes following learning. PN7-9 mice learned to prefer an odor following either odor-stroke or shock conditioning, whereas odor-shock conditioning at PN13-14 resulted in aversion/fear learning. 2-DG data indicated enhanced bulbar activity in PN7-9 preference learning, whereas significant amygdala activity was present following aversion learning at PN13-14. Overall, the mouse results parallel behavioral and neural results in the rat model of attachment, and provide the foundation for the use of transgenic and knockout models to assess the impact of both genetic (biological vulnerabilities) and environmental factors (abusive) on attachment-related behaviors and behavioral development.

Neural processing of a cocaine-associated odor cue revealed by functional MRI in awake rats

Using an olfactory conditioning procedure, brain stimulation reward threshold measurements, and functional magnetic resonance imaging (fMRI), we investigated brain stimulation reward threshold change and fMRI neural activation in response to a cocaine-associated odor cue. In the first brain stimulation experiment, over 10 days of rate–frequency curve-shift testing, rats were administered intravenous cocaine (1.0mg/kg) paired with a contextual cue of peppermint odor previously placed in the operant chamber or they were given vehicle treatment (no cocaine) in the presence of no olfactory cue. Following a 14-day drug-free rest period, rats were again given the rate–frequency curve-shift threshold test with or without the odor cue. In a second experiment, rats were similarly conditioned with a peppermint odor but with intraperitoneally delivered cocaine (10mg/kg). After a 14 day rest period, rats were imaged on a 7-T MRI for their blood oxygen level dependent (BOLD) in response to the cocaine-paired peppermint odor versus an unpaired neutral lemon odor. In the brain stimulation experiment, expected significant reward threshold shifts were produced by cocaine and, importantly, about half that level of shift was produced by the paired contextual olfactory cue. In the fMRI experiment, the insular cortex showed a significantly greater BOLD activation in cocaine-treated versus saline-treated animals to the olfactory cue, but not with the unpaired lemon scent. These data are in agreement with previous studies suggesting a role of the insular cortex in attributing reward value (positive or negative) to conditioned odor stimuli.

Context-dependent olfactory learning monitored by activities of salivary neurons in cockroaches

Context-dependent discrimination learning, a sophisticated form of nonelemental associative learning, has been found in many animals, including insects. The major purpose of this research is to establish a method for monitoring this form of nonelemental learning in rigidly restrained insects for investigation of underlying neural mechanisms. We report context-dependent olfactory learning (occasion-setting problem solving) of salivation, which can be monitored as activity changes of salivary neurons in immobilized cockroaches, Periplaneta americana. A group of cockroaches was trained to associate peppermint odor (conditioned stimulus, CS) with sucrose solution reward (unconditioned stimulus, US) while vanilla odor was presented alone without pairing with the US under a flickering light condition (1.0Hz) and also trained to associate vanilla odor with sucrose reward while peppermint odor was presented alone under a steady light condition. After training, the responses of salivary neurons to the rewarded peppermint odor were significantly greater than those to the unrewarded vanilla odor under steady illumination and those to the rewarded vanilla odor was significantly greater than those to the unrewarded peppermint odor in the presence of flickering light. Similar context-dependent responses were observed in another group of cockroaches trained with the opposite stimulus arrangement. This study demonstrates context-dependent olfactory learning of salivation for the first time in any vertebrate and invertebrate species, which can be monitored by activity changes of salivary neurons in restrained cockroaches.

Olfactory Effects on Attention Allocation and Perception of Exertion

The aim of the current study was to test the effectiveness of pleasant odors on perception of exertion and attention allocation. A secondary purpose was to employ a placebo-control design and measure perceived smell intensity during task performance; methods that have been overlooked in previous olfaction studies in the sport and exercise domain. Seventy-six college students (35 females, 41 males) were recruited to perform a handgrip task. They were randomly assigned to one of 4 groups: control, placebo, lavender odor, and peppermint odor. Adhesive strips were placed under the noses of those in the latter three groups. The placebo group had a strip with no odor. The lavender and peppermint odor groups had a drop of concentration on the strip. After establishing a maximal voluntary contraction (MVC) level, participants performed at 30% of their MVC level for as long as they could tolerate, during which they provided ratings of perceived exertion (or effort; RPE), attention, and smell intensity at 30s intervals, and affect every 60s. MANOVA procedures failed to reveal significant differences among the treatment and nontreatment groups on rate of perceived exertion, attention allocation, and total time duration on the task. However, statistical differences were found between both odor groups and the placebo group on perceived attention diversion. The lavender group reported that the odor diverted attention to a higher degree than both the peppermint and placebo groups. Although nonsignificant, findings revealed a trend suggesting that odors may have an effect on cognitive processes, and on performance. There is a need for additional research to better capture these effects. Directions for further research, with an emphasis on methodological issues are outlined.