Olfactory illusions

BACKGROUND Many patients with dementia with Lewy bodies (DLB) experience cholinesterase inhibitor- and antipsychotic-resistant psychosis. The new second-generation antipsychotic pimavanserin has been used with some success in the treatment of psychosis in other forms of dementia, including Alzheimer disease and Parkinson disease dementia. It is possible that pimavanserin may also be useful in the treatment of psychosis in DLB. We sought to describe the disease course and treatment of psychosis in 4 patients with DLB who were prescribed pimavanserin after other medications failed to reduce the frequency or severity of hallucinations and delusions...

Conflicting multisensory signals may alter embodiment to produce self-identification with a foreign body, but the role of olfaction in this process has been overlooked. We studied in healthy participants how sex (male and female sweat odors) and gender (male and female cosmetic scents) olfactory stimuli contribute to embodiment. Participants saw, on a head mounted display, the first-person perspective of a sex mismatching person. Synchronous visuotactile stimulation was applied to enhance illusory embodiment...

To date, no studies have examined the ontogeny of susceptibility to visual illusions in nonhuman mammals. Our previous study on the perception of the Delboeuf illusion by adult cats suggested they perceive this illusion, and that the visual processing involved in size judgment differs in the presence or absence of a misleading surround. We therefore asked whether weanling kittens are susceptible to the Delboeuf visual illusion, as adult cats are. Like the adults, kittens were presented with a series of 2-way food choice tasks where same- or different-size food portions were presented on same- or different-size plates...

Olfactory perception is malleable and easily modulated by top-down processes such as those induced by visual and verbal information. A classic example of this is olfactory illusions where the perceived pleasantness of an odor is manipulated by the valence of a verbal label that is either visually or auditorily presented together with the odor. The mechanism behind this illusion is still unknown, and it is not clear if it is driven only by verbal information or if there is an interaction between language functions and visual mental imagery processes...

Background: Parkinson's disease psychosis (PDP) is a common, nonmotor symptom of Parkinson's disease (PD), which may affect up to 60% of patients and is associated with impaired quality of life, increased healthcare costs, and nursing home placement, among other adverse outcomes. Characteristic symptoms of PDP include illusions; visual, auditory, tactile, and olfactory hallucinations; and delusions. PDP symptoms typically progress over its course from being mild, infrequent, and often untroubling to complex, sometimes constant, and potentially highly disturbing...

Visual illusions from astronauts in space have been reported to be associated with the passage of high energy charged particles through visual structures (retina, optic nerve, brain). Similar effects have also been reported by patients under proton and heavy ion therapies. This prompted us to investigate whether protons at the Loma Linda University Proton Therapy and Research Center (PTRC) may also affect other sensory systems beside evoking similar perceptions on the visual system. A retrospective review of proton radiotherapy patient records at PTRC identified 29 sensory reports from 19 patients who spontaneously reported visual, olfactory, auditory and gustatory illusions during treatment...

INTRODUCTION: Stereotactic stimulations of the insular cortex through intracranial electrodes aim at characterizing the semiology of insular seizures. These stimulations, carried out in the context of Stereo-Electro-Encephalography (SEEG) during presurgical monitoring of epilepsy, reproduce the ictal symptoms observed during the development of insular seizures. METHODS: The authors reviewed the results of insular stimulations performed in 222 patients admitted between 1997 and 2015 for presurgical SEEG exploration of atypical temporal or perisylvian epilepsy...

Disease with Lewy bodies or dementia with Lewy bodies (DLB), particularly at the prodromal stage, is a complex disease to diagnose because of different clinical beginnings and variable paths in terms of clinical expression. Thus DLB can be entcountered in different input modes: mild cognitive impairment, depression, acute behavioral disorders, confusion and delirium, or sleep disorders. In the aim to better diagnose the disease, should be sought obviously to search for the key symptoms: fluctuations, hallucinations, extra-pyramidal syndrome, and REM sleep behavior disorder...

The 'thermal grill illusion' (TGI) is a unique cutaneous sensation of unpleasantness, induced through the application of interlacing warm and cool stimuli. While previous studies have investigated optimal parameters and subject characteristics to evoke the illusion, our aim was to examine the modulating effect as a conditioning stimulus. A total of 28 healthy control individuals underwent three testing sessions on separate days. Briefly, 15 contact heat stimuli were delivered to the right hand dorsum, while the left palmar side of the hand was being conditioned with either neutral (32 °C), cool (20 °C), warm (40 °C), or TGI (20/40 °C)...

In Batty (2010b), I argue that there are no olfactory illusions. Central to the traditional notions of illusion and hallucination is a notion of object-failure-the failure of an experience to represent particular objects. Because there are no presented objects in the case of olfactory experience, I argue that the traditional ways of categorizing non-veridical experience do not apply to the olfactory case. In their place, I propose a novel notion of non-veridical experience for the olfactory case. In his (2011), Stevenson responds to my claim that there are no olfactory illusions...

Olfactory rivalry can occur when a binary mixture is sniffed repeatedly, with one percept dominating then the other. Experiment 1 demonstrated olfactory rivalry using several new techniques. Experiments 2 and 3 examined whether participants can notice rivalry. Participants received trials composed of odor pairs: either a mixture followed by the same mixture; or a pure odor followed by the same pure odor. On some trials participants judged whether the two stimuli were the same or different, to see if they could detect rivalry...

Several studies have demonstrated reliable cross-modal associations between odours and various visual, auditory, taste, and somatosensory attributes. How these associations arise is not well understood. We examined whether cross-modal associations to odours themselves form distinct groups, and whether these groupings relate to semantic (nameability, familiarity) and perceptual (intensity, irritancy, and hedonics) olfactory attributes. Participants evaluated 20 odours, varying in all of the latter attributes, and reported their visual, auditory, gustatory, and somatosensory associations for each...

Flavor is perhaps the most multi-modal of all of our sensory experiences. Here flavor is defined as a perception that includes gustatory, oral-somatosensory, and retronasal olfactory signals that arise from the mouth as foods and beverages are consumed. Although the sights, sounds and smells of foods that occur just before, or in the absence of eating, can impact flavor perception, it is argued that these sensory signals exert their influence by creating expectations based upon prior associations. The primary aim of the paper is to review anatomical and neurophysiological data towards an understanding of how the core sensory signals combine in the central nervous system of humans...

In the present study, we explored the conditions under which color-generated expectations influence participants' identification of flavored drinks. Four experiments were conducted in which the degree of discrepancy between the expected identity of a flavor (derived from the color of a drink) and the actual identity of the flavor (derived from orthonasal olfactory cues) was examined. Using a novel experimental approach that controlled for individual differences in color-flavor associations, we first measured the flavor expectations held by each individual and only then examined whether the same individual's identification responses were influenced by his or her own expectations...

Olfactory stimulation induces an odor-guided crawling behavior of Drosophila melanogaster larvae characterized by either an attractive or a repellent reaction. In order to understand the underlying processes leading to these orientations we stimulated single olfactory receptor neurons (ORNs) through photo-activation within an intact neuronal network. Using the Gal4-UAS system two light inducible proteins, the light-sensitive cation channel channelrhodopsin-2 (ChR-2) or the light-sensitive adenylyl cyclase (Pacalpha) were expressed in all or in individual ORNs of the larval olfactory system...

In partial epilepsy, a localized hypersynchronous neuronal discharge evolving into a partial seizure affecting a particular cortical region or cerebral subsystem can give rise to subjective symptoms, which are perceived by the affected person only, that is, ictal hallucinations, illusions, or delusions. When forming the beginning of a symptom sequence leading to impairment of consciousness and/or a classic generalized seizure, these phenomena are referred to as an epileptic aura, but they also occur in isolation...

INTRODUCTION: In Parkinson's disease there are patients with isolated and multiple cognitive impairment, and their cognitive performance ranges from normal to an advanced degree of dementia. Most patients present an executive deficit, either in isolation or combined with other cognitive disorders, which is considered to be the most characteristic aspect of the disease, and 30-40% of those affected will end up with a clinically-defined dementia. DEVELOPMENT: The presence of a mild cognitive disorder in patients with Parkinson means that the risk of dementia appearing at some time during the development of the disease is high...

Psychotic symptoms are frequent and disabling in patients with Parkinson's disease (PD). Methodological issues in the epidemiology of PD associated psychosis (PDP) include differences in the symptoms assessed, the methods of assessment, and the selection of patients. Most studies are prospective clinic-based cross-sectional studies providing point prevalence rates in samples on dopaminergic treatment. Visual hallucinations are present in about one quarter to one third of the patients, auditory in up to 20%...

UNLABELLED: Migraineurs often describe environmental triggers of their headaches, such as barometric pressure change, bright sunlight, flickering lights, air quality, and odors. Environmental aspects of indoor space and workplaces are also implicated in migraine experience. Comprehensive migraine treatment programs emphasize awareness and avoidance of trigger factors as part of the therapeutic regimen. As migraine has a substantial economic impact, remediation of correctable environmental triggers may benefit employee attendance and productivity among migraineurs...

In the olfactory epithelium (OE) continuous neurogenesis is maintained throughout life. The OE is in direct contact with the external environment, and its cells are constantly exposed to pathogens and noxious substances. To maintain a functional sense of smell the OE has evolved the ability to permanently replenish olfactory receptor neurons and sustentacular cells lost during natural turnover. A cell population residing in the most basal part of the OE, the so-called basal cells (BCs), keep up this highly regulated genesis of new cells...