Long-term Habituation Research Articles

Some properties of habituation of siphon withdrawal in the slimy clam (Ruditapes decussatus)

A first approximation to the study of learning processes in bivalves is presented. A habituation procedure was developed using the slimy clam Ruditapes decussatus. The percentage of siphon withdrawal when they were exposed to a white light was measured. In Experiment 1, a habituation-discrimination procedure was used to study the stimulus intensity effect (350-lm vs 806 lm). Clams exposed to 350-lm showed a faster habituation than those exposed to 806-lm. Experiment 2 studied the effect of stimulus and intertrial interval (ITI) duration using a 2×2 design. Trials lasted 20 or 180 seconds, and the ITI lasted 5 or 10 minutes. A combined effect of these two parameters was obtained. Habituation was faster in clams exposed to 180-sec trials with a 5-min ITI. Finally, in Experiment 3 clams were trained with five blocks of five trials with a 5-min ITI. Groups differed on trial duration (20 or 180 s). The results showed a general spontaneous recovery effect that was more pronounced for the 180 s group. Also, it was found in this experimental condition a reduced response 24 hours after finishing training (long-term habituation). Altogether, this series of experiments constitutes a first systematic demonstration of habituation in bivalves.

Aging in zebrafish is associated with reduced locomotor activity and strain dependent changes in bottom dwelling and thigmotaxis.

Aging is associated with a wide range of physiological and behavioral changes in many species. Zebrafish, like humans, rodents, and birds, exhibits gradual senescence, and thus may be a useful model organism for identifying evolutionarily conserved mechanisms related to aging. Here, we compared behavior in the novel tank test of young (6-month-old) and middle aged (12-month-old) zebrafish from two strains (TL and TU) and both sexes. We find that this modest age difference results in a reduction in locomotor activity in male fish. We also found that background strain modulated the effects of age on predator avoidance behaviors related to anxiety: older female TL fish increased bottom dwelling whereas older male TU fish decreased thigmotaxis. Although there were no consistent effects of age on either short-term (within session) or long-term (next day) habituation to the novel tank, strain affected the habituation response. TL fish tended to increase their distance from the bottom of the tank whereas TU fish had no changes in bottom distance but instead tended to increase thigmotaxis. Our findings support the use of zebrafish for the study of how age affects locomotion and how genetics interacts with age and sex to alter exploratory and emotional behaviors in response to novelty.

Long-term disgust habituation with limited generalisation in care home workers.

Countless workers handle bodily effluvia and body envelope violations every working day, and consequentially face deeply unpleasant levels of disgust. Understanding if and how they adapt can help inform policies to improve worker satisfaction and reduce staff turnover. So far, limited evidence exist that self-reported disgust is reduced (or lower to begin with) among those employed in high-disgust environments. However, it is unclear if this is due to demand effects or translates into real behavioural changes. Here, we tested healthcare assistants (N = 32) employed in UK care homes and a control sample (N = 50). We replicated reduced self-reported pathogen disgust sensitivity in healthcare workers compared to controls. We also found it negatively correlated with career duration, suggesting long-term habituation. Furthermore, we found that healthcare assistants showed no behavioural disgust avoidance on a web-based preferential looking task (equivalent to eye tracking). Surprisingly, this extended to disgust elicitors found outside care homes, suggesting generalisation of disgust habituation. While we found no difference between bodily effluvia (core disgust) and body envelope violations (gore disgust), generalisation did not extend to other domains: self-reported sexual and moral disgust sensitivity were not different between healthcare assistants and the control group, nor was there a correlation with career duration. In sum, our work confirms that people in high-frequency disgust employment are less sensitive to pathogen disgust. Crucially, we provide preliminary evidence that this is due to a process of long-term habituation with generalisation to disgust-elicitors within the pathogen domain, but not beyond it.

Paradoxical Exception to Island Tameness: Increased Defensiveness in an Insular Population of Rattlesnakes.

Island tameness results largely from a lack of natural predators. Because some insular rattlesnake populations lack functional rattles, presumably the consequence of relaxed selection from reduced predation, we hypothesized that the Santa Catalina Island, California, USA, population of the southern Pacific rattlesnake (Crotalus helleri, which possesses a functional rattle), would exhibit a decrement in defensive behavior relative to their mainland counterparts. Contrary to our prediction, rattlesnakes from the island not only lacked tameness compared to mainland snakes, but instead exhibited measurably greater levels of defensiveness. Island snakes attempted to bite 4.7 times more frequently as we endeavored to secure them by hand, and required 2.1-fold more time to be pinned and captured. When induced to bite a beaker after being grasped, the island snakes also delivered 2.1-fold greater quantities of venom when controlling for body size. The additional venom resulted from 2.1-fold larger pulses of venom ejected from the fangs. We found no effects of duration in captivity (2-36 months), which suggests an absence of long-term habituation of antipredator behaviors. Breeding bird surveys and Christmas bird counts indicated reduced population densities of avian predators on Catalina compared to the mainland. However, historical estimates confirmed that populations of foxes and introduced mammalian predators (cats and pigs) and antagonists (herbivorous ungulates) substantially exceeded those on the mainland in recent centuries, and therefore best explain the paradoxically exaggerated defensive behaviors exhibited by Catalina's rattlesnakes. These findings augment our understanding of anthropogenic effects on the behaviors of island animals and underscore how these effects can negatively affect human safety.

Semi-Automated Assessment of Long-Term Olfactory Habituation in Drosophila melanogaster Using the Olfactory Arena.

Long-lasting memories are a core aspect of an animal's life. Such memories are characterized by unique molecular mechanisms and often unique circuitry, neither of which are completely understood in vivo. The deep knowledge of the identity and connectivity of neurons of the fruit fly Drosophila melanogaster, as well as the sophisticated genetic tools that allow in vivo perturbations and physiology monitoring, make it a remarkably useful organism in which to investigate the molecular mechanisms of long-term memories. In this protocol, we focus on habituation, a non-associative form of learning, and describe a reliable, semi-automated technique to induce and assess long-term olfactory habituation (LTH) in Drosophila using the olfactory arena, thus providing a method aligned with recent technological progress in behavioral measurement. Prior work has shown that LTH is induced by a 4-day exposure to an odorant and is characterized by a long-lasting (> 24 h) reduction in behavioral response to the exposed odorant, measured using a manual and skill-intensive Y-maze assay. Here, we present a semi-automated protocol for obtaining quantifiable measures of LTH, at the level of detail required for other investigators in the field. Unlike previously described methods, the protocol presented here provides quantitative and detailed behavioral measurements obtained by video recording that can be shared with the scientific community and allows sophisticated forms of offline analysis. We suggest that this procedure has the potential to advance our understanding of molecular and circuit mechanisms of olfactory habituation, its control via neuromodulation, and its interactions with other forms of memory. Key features • A protocol to induce olfactory aversive long-term habituation in Drosophila melanogaster. • Video recording and analysis of Drosophila in an olfactory arena.

Mental but no bio-physiological long-term habituation to repeated social stress: A study on soldiers and the influence of mission abroad.

Soldiers regularly participate in missions abroad and subjectively adapt to this situation. However, they have an increased lifetime cardiovascular risk compared to other occupational groups. To test the hypothesis that foreign deployment results in different stress habituation patterns, we investigated long-term psychological and bio-physiological stress responses to a repeated social stress task in healthy soldiers with and without foreign deployment. Ninety-one female and male soldiers from the BEST study (German armed forces deployment and stress) participated three times in the Trier Social Stress Test for groups (TSST-G) prior to, 6-8 weeks after and 1 year after the mission abroad and were compared to a control group without foreign deployment during the study period. They completed the State-Trait-Anxiety Inventory scale (STAI), the Primary Appraisal Secondary Appraisal questionnaire (PASA) and the Multidimensional Mood State Questionnaire (MDBF). Salivary cortisol and α-amylase, blood pressure, heart rate and heart rate variability were determined. Soldiers showed mental habituation over the three times with a significant decrease after the TSST-G in anxiousness (STAI) and cognitive stress appraisal (PASA), they were calmer and reported better mood (MDBF). Prior to the social stress part, the mood (MDBF) declined significantly. None of the biological and physiological markers showed any adaptation to the TSST-G. Mission abroad did not significantly influence any measured psychobiological marker when compared to soldiers without foreign deployment. Foreign deployment does not result in alterations in psychobiological social stress response patterns over 1 year after mission abroad which indicates that adaptation to acute social stress is highly maintained in healthy soldiers. The discrepancy between subjective perception and objective stress response has numerous clinical implications and should receive more attention.

Neuroligin Plays a Role in Ethanol-Induced Disruption of Memory and Corresponding Modulation of Glutamate Receptor Expression

Exposure to alcohol causes deficits in long-term memory formation across species. Using a long-term habituation memory assay in Caenorhabditis elegans, the effects of ethanol on long-term memory (> 24 h) for habituation were investigated. An impairment in long-term memory was observed when animals were trained in the presence of ethanol. Cues of internal state or training context during testing did not restore memory. Ethanol exposure during training also interfered with the downregulation of AMPA/KA-type glutamate receptor subunit (GLR-1) punctal expression previously associated with long-term memory for habituation in C. elegans. Interestingly, ethanol exposure alone had the opposite effect, increasing GLR-1::GFP punctal expression. Worms with a mutation in the C. elegans ortholog of vertebrate neuroligins (nlg-1) were resistant to the effects of ethanol on memory, as they displayed both GLR-1::GFP downregulation and long-term memory for habituation after training in the presence of ethanol. These findings provide insights into the molecular mechanisms through which alcohol consumption impacts memory.

Prenatal ethanol exposure impairs sensory processing and habituation to visual stimuli, effects normalized by enrichment of postnatal environmental.

Individuals with fetal alcohol spectrum disorders (FASD) often show processing deficits in all sensory modalities. Using an operant light reinforcement model, we tested whether prenatal ethanol exposure (PE) alters operant responding to elicit a contingent sensory stimulus-light onset (turning on the light) and habituation to this behavior in rats. We also explored whether postnatal environmental enrichment could ameliorate PE-induced deficits. Pregnant Sprague Dawley rats were gavaged twice/day with 0 or 3g/kg/treatment ethanol (15% w/v) during gestational days 8-20, mimicking second-trimester heavy PE in humans. The offspring were reared in a standard housing condition or an enriched condition. Adult male and female offspring underwent an operant light reinforcement experiment with either a short-access or a long-access procedure. A dishabituation test was also conducted to characterize the habituation process. In the short-access procedure, PE led to increased operant responding to the contingent light onset in both sexes reared in the standard housing condition. Such an effect was not observed in rats reared in enriched conditions due to an overall decrease in responding. Moreover, rats reared in enriched conditions showed greater short-term habituation. In the long access procedure, PE rats showed increased responding and impaired long-term habituation. The long-access procedure facilitated both short-term and long-term habituation in control and PE rats. Prenatal ethanol exposure increases responding to contingent light onset and impairs the long-term habituation process. The PE-induced deficits were ameliorated by rearing in the enriched environment and increasing the duration and frequency of exposure to light onset. The PE-induced effects are like increased sensation-seeking, a subtype of sensory-processing deficit that is often observed in individuals with FASD. Our findings could inform a suitable animal model for investigating the underlying mechanisms and possible intervention strategies for sensory deficits in FASD.

Shark habituation to a food-related olfactory cue

Learning is a process that allows animals to develop adaptive behavioural responses to novel situations within an individual's lifetime. The simplest form of learning, habituation, acts a fundamental filter mechanism, which allows animals to ignore irrelevant recurring stimuli, thereby freeing up fitness-related resources, such as time and energy, as well as neural capacity. Although earlier studies have demonstrated that habituation occurs in a variety of taxa ranging from insects to mammals, our knowledge of this process in elasmobranchs is limited. Sharks and rays face an increasingly popular shark-diving industry, so it is important to understand how sharks respond to attractants used by tourism operators. Our study investigated whether sharks habituate to the smell of a potential food source, which has been proposed as a sustainable alternative to actively feeding sharks. We exposed 11 captive juvenile sharks individually to the smell of squid for 4 min, three times per day for 21 days in the absence of a food reward. We found declining responses to the stimulus within and across daily exposure sessions, indicating both short- and long-term habituation. Our findings suggest that sharks learn to avoid wasting time and energy on inaccessible food sources. Given the decreasing response observed in our study, the use of olfactory cues only may have limitations in its efficacy to attract sharks for tourism purposes. Habituation may act as a driver of optimal foraging strategies, enabling sharks to quickly abandon low-yielding foraging patches in search of more productive sites. • We tested whether sharks habituate to olfactory cues. • Shark response to olfactory cues decreased over time. • Sharks showed both short- and long-term habituation. • Habituation may help optimize foraging strategies in sharks. • Olfactory cues alone may not suffice for shark tourism purposes.

An increase in spontaneous activity mediates visual habituation.

SUMMARYThe cerebral cortex is spontaneously active, but the function of this ongoing activity remains unclear. To test whether spontaneous activity encodes learned experiences, we measured the response of neuronal populations in mouse primary visual cortex with chronic two-photon calcium imaging during visual habituation to a specific oriented stimulus. We find that, during habituation, spontaneous activity increases in neurons across the full range of orientation selectivity, eventually matching that of evoked levels. This increase in spontaneous activity robustly correlates with the degree of habituation. Moreover, boosting spontaneous activity with two-photon optogenetic stimulation to the levels of visually evoked activity accelerates habituation. Our study shows that cortical spontaneous activity is linked to habituation, and we propose that habituation unfolds by minimizing the difference between spontaneous and stimulus-evoked activity levels. We conclude that baseline spontaneous activity could gate incoming sensory information to the cortex based on the learned experience of the animal.

ERPs Studies of Short- and Long-Term Habituation in Humans: A Systematic Review

Habituation is a type of learning that consists of a decrease in the response to a repetitive stimulus. The traditional view is that habituation comprises two processes: a transitory one called short-term habituation (STH), promoted by stimulus presentations at short intervals, and a more durable one called long-term habituation (LTH), promoted by more spaced repetitions. Due to the importance of time in this distinction and in an attempt to elucidate its underlying mechanisms, several studies have sought to relate habituation to brain activity through the analysis of event-related potentials (ERPs). We performed a systematic review of studies on habituation of ERPs in humans using the PRISMA methodology. A total of 175 articles were evaluated for eligibility and 145 were included. Most of the studies focused on short-term effects, demonstrating habituation in a range of ERP components such as P50, P1, N1, P2, N2, and P3. These studies revealed that STH occurs with intervals ranging from 75 ms to 4 s with an optimal of 500 ms, but it does not with intervals greater than 10 s. There are also some studies showing that the P1, N1, P2, N2, and P3 components exhibit LTH with inter-stimulus intervals between 3 and 10 seconds, but the evidence is yet insufficient to establish a secure conclusion with respect to LTH. We propose that future studies should use a wider range of inter-stimulus intervals with tests of both short-and long-term habituation so that the specific neurophysiological components of each type of habituation could be determined.

The Sometimes Context-Specific Habituation: Theoretical Challenges to Associative Accounts.

Simple SummaryWhen a stimulus occurs repeatedly without significant consequences, animals tend to decrease their responses to that stimulus. This phenomenon, known as habituation, can be explained by a class of theories that posit that expected events are less effective in provoking their responses than unexpected events. According to Allan Wagner’s priming theory, one of the ways this expectation might happen is via associative learning between the stimulus and the context in which stimulation occurred. In this article, we summarize a few theoretical complexities that derive from this approach along with some relevant empirical questions that remain open to further research.A substantial corpus of experimental research indicates that in many species, long-term habituation appears to depend on context–stimulus associations. Some authors have recently emphasized that this type of outcome supports Wagner’s priming theory, which affirms that responding is diminished when the eliciting stimulus is predicted by the context where the animal encountered that stimulus in the past. Although we agree with both the empirical reality of the phenomenon as well as the principled adequacy of the theory, we think that the available evidence is more provocative than conclusive and that there are a few nontrivial empirical and theoretical issues that need to be worked out by researchers in the future. In this paper, we comment on these issues within the framework of a quantitative version of priming theory, the SOP model.

The spatiotemporal organization of experience dictates hippocampal involvement in primary visual cortical plasticity

The hippocampus and neocortex are theorized to be crucial partners in the formation of long-term memories. Here, we assess hippocampal involvement in two related forms of experience-dependent plasticity in the primary visual cortex (V1) of mice. Like control animals, those with hippocampal lesions exhibit potentiation of visually evoked potentials after passive daily exposure to a phase-reversing oriented grating stimulus, which is accompanied by long-term habituation of a reflexive behavioral response. Thus, low-level recognition memory is formed independently of the hippocampus. However, response potentiation resulting from daily exposure to a fixed sequence of four oriented gratings is severely impaired in mice with hippocampal damage. A feature of sequence plasticity in V1 of controls, which is absent in lesioned mice, is the generation of predictive responses to an anticipated stimulus element when it is withheld or delayed. Thus, the hippocampus is involved in encoding temporally structured experience, even within the primary sensory cortex.

Environmental habituation and sexual composition affect juveniles' shoaling activity in a cichlid fish (Pelvicachromis taeniatus).

Group living is widespread in animals, and many fishes form shoals. Examining within-group interactions in fishes may contribute to the general understanding of dynamic social structures in animals. The sex ratio of a group has been shown to influence grouping decisions of fishes and can be expected to affect behaviour at group level. Behavioural experiments usually involve relatively short acclimatisation times, although the establishment of environmental habituation in fishes is understudied. This study tests whether the sex ratio and long-term habituation to experimental conditions influence general shoal performance (activity parameters, density) and responses of shoals to an acoustic-mechanical disturbance cue in juveniles of the cichlid fish Pelvicachromis taeniatus via individual tracking. The disturbance consisted of a defined hit against the experimental tank, which caused sudden noise and water movement. We found that a higher proportion of females increases shoal activity (swimming speed and distance covered), suggesting that female P. taeniatus are more active than males. Furthermore, shoal activity declined when shoals habituated to the experimental settings and with the time that the shoals were grouped together, which may reflect intensified group member familiarity. Moreover, behavioural changes after disturbance were weaker when individuals were kept with their group longer and more familiar to the experimental conditions. For prey species, lower activity might be beneficial under natural conditions due to lower conspicuousness of the group. We did not find any significant effects of the investigated factors on shoal density (mean interindividual distance) and speed synchronisation. The results indicate that sexual composition, familiarity between shoal members and habituation to the experimental environment affect shoal performance in a cichlid fish.

First attempt at rehabilitation of Asiatic Black Bear cubs to the wild in Thailand

Returning orphan bear cubs to the wild can benefit bear welfare and conservation but is hindered in Asia by the scarcity of documented experience. We experimented with rehabilitation of two Asiatic Black Bear cubs in Thailand using the assisted method of soft-release. We raised the 5-month old cubs for 11 months with minimal human contact in a remote enclosure in high quality habitat, letting cubs out periodically to walk with caretakers in the forest. The caretakers acted as surrogate mothers, allowing cubs to safely acquire foraging skills and familiarity with the forest. Supplementary feeding resulted in the cubs’ rapid weight gain (average 157g/day), faster than would occur in the wild. Faster growth allowed the cubs to be released sooner, reducing the likelihood of long-term habituation. After three months of rehabilitation, the bear cubs started showing signs of being wary of the caretakers (e.g., cautious when we approached their enclosure) and their focus during walks switched from play to foraging. After seven months they began to spend nights away from their enclosure, thus declining the supplemental food. This sequence and timing of increasing separation and independence from people matched other assisted soft releases in the region. The cubs went missing in month 12, shortly before planned collaring and release. They were seen together 2.5 months later on a fruiting tree and ran away when approached. Assisted soft releases might be a promising option for bear rehabilitation in Asia but more data are needed to evaluate their effectiveness relative to other methods. This method affords direct observations of bears in the wild that can augment our knowledge of bear behavior and ecology.

Correction to: 'How do developmental and parental exposures to predation affect personality and immediate behavioural plasticity in the snail Physa acuta?'

Correction to: 'How do developmental and parental exposures to predation affect personality and immediate behavioural plasticity in the snail Physa acuta?'

Assessing the survival and sublethal injury kinetics of Listeria monocytogenes under different food processing-related stresses

The foodborne pathogen L. monocytogenes can be present in food processing environments where it is exposed to various stressors. These antimicrobial factors, which aim to eliminate the pathogen, can induce sub-lethal injury to the bacterial cells. In the present study, we investigated the efficacy of different treatments (stresses) relevant to food processing and preservation as well as sanitation methods, in generating sub-lethal injury at 4 °C and 20 °C to two L. monocytogenes strains, ScottA and EGDe. Additionally, we evaluated the survival and extent of L. monocytogenes injury after exposure to commonly used disinfectants (peracetic acid and benzalkonium chloride), following habituation in nutrient-deprived, high-salinity medium. Each stress had a different impact on the survival and injury kinetics of L. monocytogenes. The highest injury levels were caused by peracetic acid which, at 4 °C, generated high populations of injured cells without loss of viability. Other injury-inducing stresses were lactic acid and heating. Long-term habituation in nutrient-limited and high salinity medium (4 °C) and subsequent exposure to disinfectants resulted in higher survival and injury in benzalkonium chloride and increased survival, yet with lower injury levels, in peracetic acid at 20 °C. Taken together, these results highlight the potential food safety risk emerging from the occurrence of injured cells by commonly used food processing methods. Consequently, in order to accurately assess the impact of an antimicrobial method, its potential of inducing sublethal injury needs to be considered along with lethality.

Early Long-Term Memory Impairment and Changes in the Expression of Synaptic Plasticity-Associated Genes, in the McGill-R-Thy1-APP Rat Model of Alzheimer's-Like Brain Amyloidosis.

Accruing evidence supports the hypothesis that memory deficits in early Alzheimer Disease (AD) might be due to synaptic failure caused by accumulation of intracellular amyloid beta (Aβ) oligomers, then secreted to the extracellular media. Transgenic mouse AD models provide valuable information on AD pathology. However, the failure to translate these findings to humans calls for models that better recapitulate the human pathology. McGill-R-Thy1-APP transgenic (Tg) rat expresses the human amyloid precursor protein (APP751) with the Swedish and Indiana mutations (of familial AD), leading to an AD-like slow-progressing brain amyloid pathology. Therefore, it offers a unique opportunity to investigate learning and memory abilities at early stages of AD, when Aβ accumulation is restricted to the intracellular compartment, prior to plaque deposition. Our goal was to further investigate early deficits in memory, particularly long-term memory in McGill-R-Thy1-APP heterozygous (Tg+/–) rats. Short-term- and long-term habituation to an open field were preserved in 3-, 4-, and 6-month-old (Tg+/–). However, long-term memory of inhibitory avoidance to a foot-shock, novel object-recognition and social approaching behavior were seriously impaired in 4-month-old (Tg+/–) male rats, suggesting that they are unable to either consolidate and/or evoke such associative and discriminative memories with aversive, emotional and spatial components. The long-term memory deficits were accompanied by increased transcript levels of genes relevant to synaptic plasticity, learning and memory processing in the hippocampus, such as Grin2b, Dlg4, Camk2b, and Syn1. Our findings indicate that in addition to the previously well-documented deficits in learning and memory, McGill-R-Thy1-APP rats display particular long-term-memory deficits and deep social behavior alterations at pre-plaque early stages of the pathology. This highlights the importance of Aβ oligomers and emphasizes the validity of the model to study AD-like early processes, with potentially predictive value.

The Spatiotemporal Organization of Experience Dictates Hippocampal Involvement in Primary Visual Cortical Plasticity

The hippocampus and neocortex are theorized to be crucial partners in the formation of long-term memories. Here, we assess hippocampal involvement in two related forms of experience-dependent plasticity in the primary visual cortex (V1) of mice. Like control animals, those with hippocampal lesions exhibit potentiation of visually evoked potentials following passive daily exposure to a phase reversing oriented grating stimulus, which is accompanied by long-term habituation of a reflexive behavioral response. Thus, low-level recognition memory is formed independently of the hippocampus. However, response potentiation resulting from daily exposure to a fixed sequence of four oriented gratings is severely impaired in mice with hippocampal damage. A feature of sequence plasticity in V1 of controls, but absent in lesioned mice, is generation of predictive responses to an anticipated stimulus element when it is withheld or delayed. Thus, hippocampus is involved in encoding temporally structured experience, even within primary sensory cortex.

Older and Young Adults Experience Similar Long-Term Olfactory Habituation.

Olfactory habituation corresponds to a decreased behavioral or perceptual response to an odor after a prolonged exposure to this odor. Our aim was to investigate whether long-term olfactory habituation and its recovery are similar in young (<35 years old) and older adults (>50). Fifty-seven participants were recruited for a 5-week longitudinal study. They were exposed to one of the two odors (manzanate alpha [MA], irone alpha [IA]) for 2 weeks at home. Olfactory detection thresholds for both odors were measured before and after exposure. Results showed that the two age groups behaved similarly. The long-term exposure to an odor led to a temporary increase of its detection threshold (lower sensitivity to the odor). IA thresholds were more sensitive to the duration of exposure with the odor than MA thresholds. One week after termination of exposure, participants fully recovered and even became more sensitive to both odors. No cross-habituation was found between the two odors. Our findings highlight that long-term habituation is specific to the odor exposed, behaves the same in young and older adults, and is fully reversible in both age groups after 1 week.