Cognitive facilitation following intentional odor exposure

This paper reviews evidence that, in addition to incidental olfactory pollutants, intentional odor delivery can impact cognitive operations both positively and negatively. Evidence for cognitive facilitation/interference is reviewed alongside four potential explanations for odor-induced effects. It is concluded that the pharmacological properties of odors can induce changes in cognition. However, these effects can be accentuated/attenuated by the shift in mood following odor exposure, expectancy of cognitive effects, and cues to behavior via the contextual association with the odor. It is proposed that greater consideration is required in the intentional utilization of odors within both industrial and private locations, since differential effects are observed for odors with positive hedonic qualities

“What smell?” Temporarily loading visual attention induces a prolonged loss of olfactory awareness

The human sense of smell is highly sensitive, often conveying important biological signals. Yet, anecdotal evidence suggests that we commonly fail to notice supra-threshold environmental olfactory stimuli. The determinants of olfactory awareness are, as yet, unknown. Here, we adapted the ‘inattentional blindness’ paradigm, to test whether olfactory awareness is dependent on attention. Across three experiments, participants performed a visual search task with either a high or low perceptual load (a well-established attentional manipulation) while exposed to an ambient coffee aroma. Consistent with our hypothesis, task load modulated olfactory awareness: 42.5% fewer participants in the high (vs. low) load condition reported noticing the coffee aroma. Our final experiment demonstrates that, due to unique characteristics of olfactory habituation, the consequences of inattentional anosmia can persist even once attention becomes available. These findings establish the phenomenon of inattentional anosmia, and have applied implications for predicting when people may miss potentially important olfactory information

The effects of neonatal manganese exposure on impulsivity, unlearned motoric function, and reward

This study examined the effects of low to moderate doses of manganese (0, 250, or 750 _g per day from PD 1-21) on a comprehensive battery of behaviors in rats during the neonatal period, preweanling period, and in adulthood

The Role of the Hippocampus in Representations of Emotional Memory

Although the hippocampus has long been implicated in contextual fear learning, the exact function of this brain structure is unclear. It is generally thought to encode a spatial context with which a fear memory can be associated, but how it may accomplish this and whether it plays a role in emotional memory is largely unknown. It is also unclear whether the hippocampus acts as a single unitary structure, or whether the dorsal and ventral poles, which exhibit differential connectivity to other brain regions, function independently. This dissertation examines the involvement of the hippocampus in emotional learning. A contextual fear conditioning paradigm using a predator odor as an ethologically relevant fearful stimulus was developed and lesions and immunohistochemistry were used to examine differential involvement of the dorsal and ventral hippocampus in response to fear learning. Long-term physiological recordings of dorsal place cells were then conducted to determine the effects of fear conditioning and also fear extinction on contextual representations in the hippocampus. Additionally, cells in the ventral hippocampus were assessed for responses to visuospatial manipulations and changing odor cues of varying emotional valence. It was found that the dorsal and ventral hippocampal regions are both independently required for contextual fear conditioning, and neurons in each region are differentially activated in response to fear learning. Furthermore, place cells in the dorsal hippocampus remapped in response to fear conditioning and stabilized those new fields in the long term. Extinction training caused many place cells to remap once again, suggesting that the dorsal hippocampus encodes varying representations of `fearful\u27 and `safe\u27 contexts. Finally, cells in the ventral hippocampus exhibited stronger responses to anxiogenic contextual cues compared to dorsal cells. In conclusion, these data suggest that the hippocampus is involved in emotional learning and that its function may vary along its longitudinal axis

The Demands of Episodic Memory on Hippocampal Function in Rats and Humans

This thesis sought to explore episodic memory, interference caused by similar events and its demands on hippocampal function by using different methodological and practical approaches in humans and rodents. Overall, this thesis focused on three aims, which included methodological approaches to testing episodic memory, using this approach to investigate cholinergic depletion of the hippocampus, and linking animal and human behavioural research. The recent development of spontaneous recognition tasks in rats to assess multiple trials consecutively in one testing session allow an opportunity to assess the role of contextual changes and interference in episodic memory. In a series of studies, it was shown that a new continuous trials apparatus can be used in behavioural as well as lesion studies to further explore the role of acetylcholine involved in episodic memory in rats without causing any proactive interference. Furthermore, the behavioural tasks in this thesis emphasise that context, which can take various forms, plays a profound role in segmenting memory of events. Whereas increasing the number of trials happening consecutively normally did not produce interference between events remembered, contextual representation within those trials was crucial. Chapters 2-7 demonstrated that depending on the context’s nature it enhances the segmentation of similar episodes and avoids interference, but it can also hinder recollection of events. Chapter 8 supplemented these findings by providing evidence in humans, where a clear deficit in recollection was found when a spatial change in a virtual environment was encountered, revealing a location updating effect. However, further validation of the human episodic memory task is necessary to make it a useful method in assessing different forms of hippocampal mechanisms involved in episodic memory

Validating non-motivated methods and equipment for studying mouse olfactory behavior

Mouse olfactory behavior has traditionally been difficult to assess due, in part, to the expensive nature of behavioral equipment and the lengthy process of training animals. The present study aims to validate a new behavioral paradigm requiring no prior animal training using existing liquid dilution behavioral olfactometers. We also aim to validate Triton-100x, a detergent, as a new anosmia inducing agent, as well as self-built, Do-it-yourself (DIY) behavioral olfactometers. Equipment and methods were tested using a variety of common-discrimination and detectionthreshold assays. Difficulties maintaining stimulus control arose during testing as mice routinely detected volume-to-volume concentrations of amyl acetate diluted in mineral oil below reported thresholds (1x10-8: n = 8, p \u3c 0.05). Stimulus control was corrected by using individual vials for each odor presentation. These results demonstrate that non-motivated behavior using existing equipment is an effective alternative to traditional training methods when stimulus control is properly accounted for. Furthermore, intranasal irrigation with 0.1% Triton successfully induced recoverable anosmia in mice (Day 6: p \u3e 0.05, n = 6; Day 7: p \u3c 0.05, n = 6; PBS: p \u3c 0.05, n = 6). Finally, a behavioral olfactometer was successfully constructed from Arduino microcontrollers for ~$750. At a fraction of the cost, our DIY behavioral olfactometer produced behavioral data comparable to commercial equipment in common olfactory assays. We hope this cost-effective, easy-to-use equipment will be used for both research and teaching purposes

Behavioral, Pharmacological and Neuroanatomical Analysis of Serotonin 2C Receptor Agonism on Maternal Behavior in Rats

As a highly motivated social behavior, maternal behavior in rats has been routinely used to study psychoactive drugs for clinical, neuroscience and pharmacological purposes. Recent evidence indicates that acute activation of serotonin 2C (5-HT2C) receptors causes a disruption of rat maternal behavior. The present study was designed to elucidate the behavioral, pharmacological mechanisms and neuroanatomical basis of this 5-HT2C effect. First, we replicated the finding that acute MK212 injection (2.0 mg/kg, a highly selective 5-HT2C agonist) disrupts maternal behavior, especially on pup retrieval. Interestingly, this disruption was significantly attenuated by 4-h pup separation (a procedure putatively increased maternal motivation). MK212 also suppressed food retrieval, indicating that it has a general effect on motivated behaviors. Second, we showed that MK212 disrupts maternal behavior by specifically activating 5-HT2C receptor, as pretreatment with a 5-HT2C receptor antagonist SB242084 (0.6 and 1.0 mg/kg) alleviated MK212-induced disruption on pup retrieval. Third, we microinjected MK212 into various brain regions implicated in the regulation of maternal behavior: nucleus accumbens shell (25, 75, 250 ng/0.5μl/side), medial prefrontal cortex (25 and 250 ng, 1, 2 and 5 μg/0.5μl/side), and medial preoptic area (MPOA, 75 ng, 1 and 5 μg/0.5μl/side). Pup retrieval and other maternal responses were not affected by any of these manipulations. Finally, we used c-Fos immunohistochemistry to identify the central mechanisms of the acute and repeated MK212 effects on maternal behavior. Acute MK212 (2.0 mg/kg) disrupted pup retrieval and concurrently decreased c-Fos expression in the ventral part of lateral septal nucleus (LSv), MPOA, dentate gyrus (DG) and dorsal raphe (DR), but increased it in the central amygdala (CeA). Five days of repeated MK212 (2.0 mg/kg) treatment produced a persistent disruption of pup retrieval and only decreased c-Fos expression in the DR. These findings not only confirm a role of 5-HT2C receptor in rat maternal behavior, but also suggest that the coordinated 5-HT2C activity in various limbic (e.g., LSv, DG, CeA), hypothalamic regions (e.g., MPOA) and brainstem areas (e.g. DR), is likely involved in the mediation of important psychological processes (e.g. motor function, motivation) necessary for the normal expression of maternal behavior

Involvement of dopamine in the nucleus accumbens and prefrontal cortex in cocaine-associative learning

textStimuli formerly associated with cocaine-taking behavior are known to elicit physiological changes and craving in cocaine-dependent individuals. This is a result of learned associations between an environmental stimulus and the effects of cocaine, and is believed to be a major factor that leads to relapse in recovering cocaine addicts. A precise neural mechanism underlying how cocaine-paired stimuli produce craving and drug-taking behavior is currently unknown. Synaptic plasticity is known as a neural basis for associative learning. A modulatory role of a neurotransmitter, dopamine (DA), in synaptic plasticity has been implicated. Moreover, recent studies indicate that DA is particularly important during acquisition of associative learning, but less important as learning progresses. Yet, this notion has not been fully investigated using cocaine as a reinforcer. The nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC) brain regions, are both largely implicated in drug addiction. Using an animal model of drug- taking behavior in conjunction with an in vivo microdialysis technique, the dissertation experiments determined the involvement of DA in during distinctive stages of cocaine associative learning. Results from the experiments showed that NAcc DA was responsive to cocaine-paired stimuli during early, but not the late stages of cocaine associative learning while responsiveness of mPFC DA to cocaine-paired stimuli was enhanced with extended conditioning experience. The results indicate that brain areas responsive to conditioned stimuli transfers as associative learning progresses. These findings suggest that a dynamic role of DA in distinctive brain regions should be taken into account during treatment and relapse prevention of cocaine addiction.Pharmac

D-cycloserine in the basolateral amygdala prevents extinction and enhances reconsolidation of odor-reward associative learning in rats

It is well established that D-cycloserine (DCS), a partial agonist of the NMDA receptor glycine site, enhances learning and memory processes. Although the effects of DCS have been especially elucidated in the extinction and reconsolidation of aversive behavioral paradigms or drug-related behaviors, they have not been clearly determined in appetitive tasks using natural reinforcers. The current study examined the effects of pre-retrieval intra-basolateral amygdala (BLA) infusions of DCS on the extinction and reconsolidation of an appetitive odor discrimination task. Rats were trained to discriminate between three odors, one of which was associated with a palatable food reward, and, 20 min prior to extinction learning (experiment 1) or reactivation (experiment 2), they received bilateral intra-BLA infusions of DCS or vehicle. In experiment 1, DCS infusion reduced the rate of extinction learning, weakened extinction retention in a post-extinction test and enhanced reacquisition of the ODT task. In experiment 2, DCS improved subsequent memory expression in the reconsolidation test performed one day after the reactivation session. Such results indicate the involvement of BLA NMDA receptors in odor-food reward associative memory and suggest that DCS may potentiate the persistence or strength of the original memory trace