Search Results (16)

Background/Objectives: Approach-avoidance behavior is critical for adaptive behavior. The neural basis of these behaviors has been investigated extensively, but the effect of odor valence is unclear. This study tested how positive, negative, and neutral odors affect behavior and event-related potentials (ERPs) in the approach-avoidance task (AAT). Methods: Thirty-two healthy participants performed an AAT. We measured reaction time, accuracy, and ERP components (P1, N1, N2, P3) to understand the process of motivational processing over time. Results: Participants responded faster and more accurately when the direction and target type were congruent under all odor conditions. Odors did not change this core consistent pattern. In contrast, ERP results revealed stage-specific modulations. P1 and N1 components reflected odor-related changes in early sensory processing. The N2 effect present under the air condition was largely absent under positive and negative odors. This suggests reduced conflict monitoring. P3 amplitudes were consistently larger for avoidance than for approach responses, regardless of odor valence. Conclusions: The results demonstrate that odor valence reorganized the neural dynamics of the AAT without changing behavioral performance. This finding shows that olfactory valence modulates attention and control mechanisms and plays a unique role in regulating human motivation. Full article

Existing research shows that the human salivary response habituates to repeated presentation of visual, olfactory, or gustatory food cues in adults and children. The aim of this research is to examine the neurophysiological effects of attentional habituation within sessions toward repetition of the same high- and low-calorie food and non-food images. Participants’ event-related potential (ERP) responses were measured as they passively viewed the same food and non-food images repeatedly. The ERP analysis results from trial groups within a session over time indicated that repeated exposure to the same image has a distinct effect on the brain’s attentional responses to food and non-food images. The brain response modulated by motivation and attention decreases over time, and it is significant in the 170–300 ms onset time window for low-calorie images and 180–330 ms onset time window for non-food images in the parietal region of the brain. However, the modulation to high-calorie images remains sustained over time within the session. Furthermore, the ERP results show that high-calorie images have a slower rate of declination than low-calorie images, followed by non-food images. In conclusion, our ERP study showed that a habituation-like mechanism modulates attention to repeated low-calorie and non-food images, whereas high-calorie images have a negligible effect. High-energy foods have a larger reward value, which increases prolonged attention and reduces the process of habituation. This could be one of the reasons why a negligible neural attentional habituation and slow habituation rate to high-calorie diets could have negative health consequences. Full article

Background: Olfactory dysfunction (OD) is an underestimated symptom in multiple sclerosis (MS). Multiple factors may play a role in the OD reported by MS patients, such as ongoing inflammation in the central nervous system (CNS), damage to the olfactory bulbs due to demyelination, and the presence of plaques in brain areas associated with the olfactory system. Indeed, neuroimaging studies in MS have shown a clear association of the OD with the number and activity of MS-related plaques in frontal and temporal brain regions. However, these studies have used only psychophysical tests to evaluate the OD in MS patients. Olfactory Event-Related Potentials (OERPs) are a method to assess olfaction with the clear advantage of its objectivity in comparison with psychophysical tests. The aim of this study was to investigate the association between the parameters of OERP components (latency and amplitude) and the lesion load of the brain regions which are involved in olfaction in a cohort of relapsing-remitting (RR) MS patients. Methods: In this cross-sectional study, we enrolled 30 RRMS patients and 30 healthy controls. The parameters of OERP components and magnetic resonance imaging data (lesions in the CNS) were analyzed in RRMS patients. Results: The association found between the RRMS patient groups with and without OERPs and the number of lesions in the frontal area as well as the correlation between the lesion load in the temporal area and OERP parameters suggest how brain alterations may impact on olfactory performance in MS. In addition, the predictive value of the number of lesions in the frontal and parietal areas for P2 amplitude also highlights the potential for OERP measures to serve as markers for disease progression in MS. Conclusions: This approach to assess the olfaction in MS could improve our understanding of the disease’s neurological impact and contribute to the development of new targeted interventions to mitigate olfactory sensory deficits. Full article

Poor alertness levels and related changes in cognitive efficiency are common when performing monotonous tasks such as extended driving. Recent studies have investigated driver alertness decrement and possible strategies for modulating alertness with the goal of improving reaction times to safety critical events. However, most studies rely on subjective measures in assessing alertness changes, while the use of olfactory stimuli, which are known to be strong modulators of cognitive states, has not been commensurately explored in driving alertness settings. To address this gap, in the present study we investigated the effectiveness of olfactory stimuli in modulating the alertness state of drivers and explored the utility of electroencephalography (EEG) in developing objective brain-based tools for assessing the resulting changes in cortical activity. Olfactory stimulation induced a significant differential effect on braking reaction time. The corresponding effect to the cortical activity was characterized using EEG-derived metrics and the devised machine learning framework yielded a high discriminating accuracy (92.1%). Furthermore, neural activity in the alpha frequency band was found to be significantly associated with the observed drivers’ behavioral changes. Overall, our results demonstrate the potential of olfactory stimuli to modulate the alertness state and the efficiency of EEG in objectively assessing the resulting cognitive changes. Full article

Microglial activation often accompanies the plastic changes occurring in the brain of patients with neurodegenerative diseases. A_2A and A₃ adenosine receptors have been proposed as therapeutic targets to combat neurodegeneration. RNAseq was performed using samples isolated from lipopolysaccharide/interferon-γ activated microglia treated with SCH 58261, a selective A_2A receptor antagonist, and with both SCH 58261 and 2-Cl-IB-MECA, a selective A₃ receptor agonist. None of the treatments led to any clear microglial phenotype when gene expression for classical biomarkers of microglial polarization was assessed. However, many of the downregulated genes were directly or indirectly related to immune system-related events. Searching for genes whose expression was both significantly and synergistically affected when treated with the two adenosine receptor ligands, the AC122413.1 and Olfr56 were selected among those that were, respectively, upregulated and downregulated. We therefore propose that the products of these genes, olfactory receptor 56 and T-cell activation GTPase-activating protein 1, deserve attention as potential biomarkers of phenotypes that occur upon microglial activation. Full article

People affected by the Long COVID-19 (LC) syndrome often show clinical manifestations that are similar to those observed in patients with mild cognitive impairments (MCI), such as olfactory dysfunction (OD), brain fog, and cognitive and attentional diseases. This study aimed to investigate the chemosensory-evoked related potentials (CSERP) in LC and MCI to understand if there is a common pathway for the similarity of symptoms associated with these disorders. Eighteen LC patients (mean age 53; s.d. = 7), 12 patients diagnosed with MCI (mean age 67; s.d. = 6), and 10 healthy control subjects (mean age 66; s.d. = 5, 7) were recruited for this exploratory study. All of them performed a chemosensory event-related potentials (CSERP) task with the administration of trigeminal stimulations (e.g., the odorants cinnamaldehyde and eucalyptus). Study results highlighted that MCI and LC showed reduced N1 amplitude, particularly in the left frontoparietal network, involved in working memory and attentional deficits, and a reduction of P3 latency in LC. This study lays the foundations for evaluating aspects of LC as a process that could trigger long-term functional alterations, and CSERPs could be considered valid biomarkers for assessing the progress of OD and an indicator of other impairments (e.g., attentional and cognitive impairments), as they occur in MCI. Full article

The involvement of iron in the pathogenesis of Alzheimer’s disease (AD) may be multifaceted. Besides potentially inducing oxidative damage, the bioavailability of iron may be limited within the central nervous system, creating a functionally iron-deficient state. By comparing staining results from baseline and modified iron histochemical protocols, iron was found to be more tightly bound within cortical sections from patients with high levels of AD pathology compared to subjects with a diagnosis of something other than AD. To begin examining whether the bound iron could cause a functional iron deficiency, a protein-coding gene expression dataset of initial, middle, and advanced stages of AD from olfactory bulb tissue was analyzed for iron-related processes with an emphasis on anemia-related changes in initial AD to capture early pathogenic events. Indeed, anemia-related processes had statistically significant alterations, and the significance of these changes exceeded those for AD-related processes. Other changes in patients with initial AD included the expressions of transcripts with iron-responsive elements and for genes encoding proteins for iron transport and mitochondrial-related processes. In the latter category, there was a decreased expression for the gene encoding pitrilysin metallopeptidase 1 (PITRM1). Other studies have shown that PITRM1 has an altered activity in patients with AD and is associated with pathological changes in this disease. Analysis of a gene expression dataset from PITRM1-deficient or sufficient organoids also revealed statistically significant changes in anemia-like processes. These findings, together with supporting evidence from the literature, raise the possibility that a pathogenic mechanism of AD could be a functional deficiency of iron contributing to neurodegeneration. Full article

The subjective and demanding nature of olfactory testing means that it is often neglected in clinic despite loss of smell leading to significant limitations in everyday life. The list of diseases associated with loss of olfaction far exceeds the field of otorhinolaryngology and can also be seen in neurodegenerative disorders. Knowledge of possible clinical testing is essential to determine a proper differential diagnosis for the loss of olfactory sense. Causes of olfactory impairment can be divided into either failure in transferring odour to the organ of perception or damage to the olfactory pathway structure itself. Examination should therefore include methods evaluating cross-sectional area and patency of the nasal cavity as well as subjective or objective assessment of olfactory function. In this report we summarize several articles, studies, and our own experiences to provide a comprehensive review of their current clinical usage including their benefits, limitations, and possible outcomes. We also discuss the mechanism of olfaction step by step to provide a full understanding of the possible errors depending on the localization in the pathway and the methods designed for their detection. We discuss the correlation of the microbiome in nasal polyposis and chronic rhinitis with olfactory impairment using objective olfactometry. The topic of objective olfactometry and the examination of olfactory event-related potentials (OERP) is commented upon in detail. Full article

Neurotrauma injuries are notoriously difficult to deal with both clinically as well as experimentally, as the cellular and molecular events ensuing after injury complicate the neuroinflammatory processes. Spinal cord injuries are further complicated by the formation of scars at the injury sites, which can provide a physical barrier to repair. The lack of effective clinical therapy for spinal cord injury underscores the need for experimental approaches to generate effective therapies. To repair the injury, cell transplantation offers the potential to replace lost cells and create a permissive bridge to promote neural regeneration across the injury site. Olfactory ensheathing cells (OECs), which are the glia of the olfactory nerve, stand apart from other candidate cell types due to their innate natural abilities to manage nerve injury and promote repair and regeneration. This is evidenced by their physiological role in the daily repair and maintenance of the olfactory nerve. Here, we explain their properties in relation to their physiological role and their most relevant cellular attributes, including cellular interactions, phagocytosis, migration, axonal guidance and support, and modulation of neuroinflammation. We highlight some critical drawbacks in the current approaches and identify some ways to address them. Full article

The human sense of smell is important for many vital functions, but with the current state of the art, there is a lack of objective and non-invasive methods for smell disorder diagnostics. In recent years, increasing attention is being paid to olfactory event-related potentials (OERPs) of the brain, as a viable tool for the objective assessment of olfactory dysfunctions. The aim of this review is to describe the main features of OERPs signals, the most widely used recording and processing techniques, and the scientific progress and relevance in the use of OERPs in many important application fields. In particular, the innovative role of OERPs is exploited in olfactory disorders that can influence emotions and personality or can be potential indicators of the onset or progression of neurological disorders. For all these reasons, this review presents and analyzes the latest scientific results and future challenges in the use of OERPs signals as an attractive solution for the objective monitoring technique of olfactory disorders. Full article

Among millions of sufferers of chronic rhinosinusitis (CRS), the challenge is not only constantly coping with CRS-related symptoms, such as congested nose, sinus pain, and headaches, but also various complications, such as attention difficulties and possible depression. These complications suggest that neural activity in the central nervous system may be altered in those patients, leading to unexpected conditions, such as neurodegeneration in elderly patients. Recently, some studies linked the presence of CRS and cognitive impairments that could further develop into Alzheimer’s disease (AD). AD is the leading cause of dementia in the elderly and is characterised by progressive memory loss, cognitive behavioural deficits, and significant personality changes. The microbiome, especially those in the gut, has been recognised as a human organ and plays an important role in the development of various conditions, including AD. However, less attention has been paid to the microbiome in the nasal cavity. Increased nasal inflammatory responses due to CRS may be an initial event that changes local microbiome homeostasis, which may further affect neuronal integrity in the central nervous system resulting in AD. Evidence suggests a potential of β-amyloid deposition starting in olfactory neurons, which is then expanded from the nasal cavity to the central nervous system. In this paper, we reviewed currently available evidence that suggests this potential mechanism to advise the need to investigate the link between these two conditions. Full article

Recent reports have identified rare, biallelic damaging variants of the AGTPBP1 gene that cause a novel and documented human disease known as childhood-onset neurodegeneration with cerebellar atrophy (CONDCA), linking loss of function of the AGTPBP1 protein to human neurodegenerative diseases. CONDCA patients exhibit progressive cognitive decline, ataxia, hypotonia or muscle weakness among other clinical features that may be fatal. Loss of AGTPBP1 in humans recapitulates the neurodegenerative course reported in a well-characterised murine animal model harbouring loss-of-function mutations in the AGTPBP1 gene. In particular, in the Purkinje cell degeneration (pcd) mouse model, mutations in AGTPBP1 lead to early cerebellar ataxia, which correlates with the massive loss of cerebellar Purkinje cells. In addition, neurodegeneration in the olfactory bulb, retina, thalamus and spinal cord were also reported. In addition to neurodegeneration, pcd mice show behavioural deficits such as cognitive decline. Here, we provide an overview of what is currently known about the structure and functional role of AGTPBP1 and discuss the various alterations in AGTPBP1 that cause neurodegeneration in the pcd mutant mouse and humans with CONDCA. The sequence of neuropathological events that occur in pcd mice and the mechanisms governing these neurodegenerative processes are also reported. Finally, we describe the therapeutic strategies that were applied in pcd mice and focus on the potential usefulness of pcd mice as a promising model for the development of new therapeutic strategies for clinical trials in humans, which may offer potential beneficial options for patients with AGTPBP1 mutation-related CONDCA. Full article

3M syndrome is a rare disorder that involves the gene cullin-7 (CUL7). CUL7 modulates odour detection, conditions the olfactory response (OR) and plays a role in the development of the olfactory system. Despite this involvement, there are no direct studies on olfactory functional effects in 3M syndrome. The purpose of the present work was to analyse the cortical OR through chemosensory event-related potentials (CSERPs) and power spectra calculated by electroencephalogram (EEG) signals recorded in 3M infants: two twins (3M-N) and an additional subject (3M-O). The results suggest that olfactory processing is diversified. Comparison of N1 and Late Positive Component (LPC) indicated substantial differences in 3M syndrome that may be a consequence of a modified olfactory processing pattern. Moreover, the presence of delta rhythms in 3M-O and 3M-N clearly indicates their involvement with OR, since the delta rhythm is closely connected to chemosensory perception, in particular to olfactory perception. Full article

Various brain imaging techniques are available, but few are specifically designed to visualize chemical sensory and, in particular, olfactory processing. This review describes the results of quantitative and qualitative studies that have used electroencephalography (EEG) and magneto-encephalography (MEG) to evaluate responses to olfactory stimulation (OS). EEG and MEG are able to detect the components of chemosensory event-related potentials (CSERPs) and the cortical rhythms associated with different types of OS. Olfactory studies are filling the gaps in both the developmental field of the life cycle (from newborns to geriatric age) and the clinical and basic research fields, in a way that can be considered the modern “cognitive neuro-olfactometry”. Full article

Obesity has reached epidemic proportions, motivating research into the underlying mechanisms. Olfaction is a powerful mediator of food consumption, and obesity has been associated with altered olfactory sensitivity. The current study used an event-related functional magnetic resonance imaging (fMRI) to examine the central processing of odor in humans to gain insight into the effect of the body mass index (BMI) on the neural processes involved in rating the pleasantness of a food odor during a hunger state and in a satiety state. We hypothesized that, during the hedonic evaluation of food odor, BMI would be associated with differences in brain activation within olfactory and higher order processing areas important for perception, reward, and memory. We report novel findings of a dissociation between the relationship between BMI and activation in reward areas and in olfactory and odor memory areas, i.e., activation in reward areas decreased as BMI increased, whereas activation in primary olfactory and memory regions increased as BMI increased. A greater BMI is associated with decreased activation in the reward and frontal regions, supporting a blunted reward response in obesity. These findings have important potential implications for decision making, response inhibition, and reward-based behaviors that may play key roles as causal and maintenance factors in obesity. In contrast, a greater BMI is associated with an increased activation in the primary olfactory and memory areas, which was observed during a hunger state. These results raise the speculative hypothesis that high BMI may be associated with hyperactivation in the olfactory and memory areas, and that over time, the resulting excitotoxic effects may contribute to neurodegenerative changes in these areas. Full article