Laurence Jacquot

Toxicity of Carbon Dioxide: A Review

The toxicity of carbon dioxide has been established for close to a century. A number of animal experiments have explored both acute and long-term toxicity with respect to the lungs, the cardiovascular system, and the bladder, showing inflammatory and possible carcinogenic effects. Carbon dioxide also induces multiple fetal malformations and probably reduces fertility in animals. The aim of the review is to recapitulate the physiological and metabolic mechanisms resulting from CO(2) inhalation. As smokers are exposed to a high level of carbon dioxide (13%) that is about 350 times the level in normal air, we propose the hypothesis that carbon dioxide plays a major role in the long term toxicity of tobacco smoke.

Ambient odors modulate visual attentional capture

Sudden visual events capture attention involuntarily because they may signal potential threats. Some theoretical accounts consider that the biological significance of these events is established through the limbic structures. Thus, the manipulation of the limbic activity would affect attentional capture. Since these structures are directly linked to the olfactory system, we have tended to modulate their activity with olfactory stimulations. We have examined behavioral performance in a task of attentional capture by luminance under conditions of ambient odors. Our results show that attentional capture is indeed modulated by ambient odors, and that this modulation may depend on the odors properties.

Quality of odor and olfactory lateralization processes in humans.

The study of olfactory lateralization processes in humans has given rise to many publications, but the resulting data have not been homogeneous. Sensorial cerebral asymmetry depends on several factors (nature of task, characteristics of subjects, etc.) and could also depend on the quality of the stimulus, especially in olfaction. This field appears to be widely unexplored and the quality of odor is a complex property. The aim of this study was to investigate variations in psychophysiological measurements (bilateral electrodermal recordings) related to the quality of odors. Electrodermal asymmetries were used as a function of differential hemispheric activation. Two major characteristics of odor were explored, the hedonic valence (pleasant/unpleasant) and the trigeminal component (irritant/non-irritant). The results obtained in a sample of 30 right-handed subjects (15 males and 15 females) showed a predominance of the right hemisphere in the treatment of olfactory information not depending on the quality of odor, except the trigeminal-nerve activation.

Unconscious odor detection could not be due to odor itself

Unconscious odor detection has been demonstrated but the mechanisms implied in this process have been poorly studied. In so far, most odorants activate both olfactory and trigeminal systems, it is relevant to explore how each system could be involved in the unconscious detection processes. This study used three methods to determine the detection thresholds for three odorants. The results showed that (1). psychophysical were lower than self-evaluated thresholds whatever the odorant; (2). an odorant with trigeminal component had the ability to produce an autonomic (skin conductance response-SCR) activation with lower concentrations than psychophysical and self-evaluated thresholds; on the contrary, an odorant, which stimulates only the olfactory system, induces an autonomic activation only with higher concentrations than psychophysical and self-evaluated thresholds. These findings suggest that unconscious odor detection could be due to the trigeminal component of odorants.

Comparison between low doses of TMT and cat odor exposure in anxiety- and fear-related behaviors in mice

Few comparisons were made between cat odor and synthetic fox odor (TMT) to study fear and anxiety in rodents. TMT is frequently used are at high concentration while the stimulus should be as possible closer to natural conditions. The aim of this work was to compare behavioral responses of mice exposed to cat odor and low doses of TMT (i.e. 10 μl of a solution containing 1%, 0.1% or 0.01% TMT). Behavioral parameters were recorded in elevated plus-maze and in open field. Results showed that 1% TMT and 0.1% TMT induced similar responses to cat odor, contrary to water and 0.01% TMT which failed to elicit fear or anxiety-related behaviors. Additionally, behavioral changes were more marked in EPM - e.g. time spent in open arms - than in open field - e.g. freezing. These findings are discussed in terms of a possible continuum of mild anxiety-like behaviors to strong fear-like behaviors linked to predator odor intensity.

Comparative fear-related behaviors to predator odors (TMT and natural fox feces) before and after intranasal ZnSO 4 treatment in mice

The possibility that synthetic 2,4,5-trimethylthiazoline (TMT), frequently used to induce unconditioned fear in rodents, could be more a pungent odor activating intranasal trigeminal nerve fibers rather than a predator odor index is currently discussed. In order to explore this question, the present study compared fear-related behaviors to predator odors (synthetic 10% TMT and natural fox feces) and toluene (as an irritant compound without ecological significance) before and after intranasal ZnSO4 perfusion which is known to provoke transient anosmia. Results show that natural fox feces could be consider as a pure olfactory (CN I) nerve stimulant while 10% TMT appeared to be a mixed olfactory (CN I) and trigeminal (CN V) nerves stimulant with a great olfactory power and a low trigeminal power. These findings suggest that behavioral neuroscience studies should use concentrations lower than 10% TMT to obtain fear-related behaviors similar to those obtained with natural fox feces odor.

Postnatal exposure to synthetic predator odor (TMT) induces quantitative modification in fear-related behaviors during adulthood without change in corticosterone levels

Environmental stimuli and adverse experiences in early life may result in behavioral and physiological changes in adulthood. In several animal species, the odors cues are crucial in the setting of adaptive behaviors, especially towards predators. However, little is known about the effects of postnatal exposure to predator odor on the later physiological and behavioral responses to this natural stressor. Thus, the aim of this study was to investigate the effects of a postnatal exposure to synthetic predator odor (TMT) in mice pups on later adult fear-related behaviors and corticosterone levels in response to this specific stimulus. Pups postnatally exposed to only water showed later in adult life behavioral responses when exposed to TMT that were statistically different from mice that were exposed as neonates to TMT. In addition, mice exposed as neonates to TMT showed a decrease of fear-related behaviors while no differences occurred in the corticosterone levels between both groups.

Just noticeable difference in olfaction: a discriminative tool between healthy elderly and patients with cognitive disorders associated with dementia.

Olfactory dysfunction appears to be one of the earliest signs of several age-related neurodegenerative disorders, including Alzheimer`s disease (AD) or Parkinson`s disease (PD). To rate performance and olfactory deficits in patients with cognitive disorders, various olfactory tasks have been used such as odor detection, discrimination, recognition memory, identification and naming but no study has been focused on just noticeable difference (JND), a sensitive tool of detection. The aim of this study was to investigate and compare variations in JNDs in healthy elderly and in patients with cognitive disorders associated with dementia. The results showed significantly higher olfactory JNDs in a population with cognitive disorders associated with dementia - i.e. a lower olfactory detection performance - compared to a control population paired in age, gender and education level. Additionally, the findings of the present study showed strong correlations between cognitive performances and JND scores in the control population contrary to the patient population. These findings are discussed in relation to the relevance of using olfactory JNDs in the diagnosis of dementias.

My heart is in my hands: The interoceptive nature of the spontaneous sensations felt on the hands

Somatic sensations may arise in the total absence of external stimuli, i.e., spontaneous sensations (SPSs). Because the background of body sensations has been mentioned as a possible contributor to interoceptive functions, such as the perception of the self and the conscious awareness of ones own body, a possible link between SPSs and interoception has been advocated. Yet, no study has provided direct evidence on such a relationship. The aim of the present study was to establish a link between SPSs and interoception. On the basis of the literature, the accuracy of heartbeat perception was taken as an index of general interoception across different bodily modalities. It was found that individuals with good heartbeat perception experienced more numerous and more intense SPSs. Furthermore, taken along with other individual characteristics, heartbeat perception accuracy predicted the perceived intensity of SPSs, their spatial extent, their variety, as well as confidence in their spatial characteristics. However, we also provide evidence that good vs. poor heartbeat perception is not just a matter of degree. We conclude that interoception definitely contributes to the perception of SPSs.

Postnatal exposure to predator odor (TMT) enhances spatial learning in mice adulthood.

Adult behavioral and physiological responses are partly dependent on neonatal experiences. In several animal species, enriched/aprovished environments and stressful/appeasing events are crucial in the setting of adaptative behaviors. However, little is known about the effects of postnatal exposure to predator odor (as unconditioned fear-related stimulus) on spatial learning at adulthood. Thus, the aim of the present study was to investigate the effects of a postnatal exposure to 2,4,5-trimethylthiazoline (TMT, as a predator odor) on radial arm maze (RAM), Tolman maze (TM) and Morris water maze (MWM) in mice at adulthood. The results showed that a TMT group constituted by mice exposed postnatally during 3 weeks to TMT presented significantly better spatial learning achievements in adulthood compared to a water group, postnatally exposed to water only, as well as compared to a butanol group (butanol used as an odor without ecological significance) exposed postnatally to butanol during 3 weeks.