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Olfactory illusions

Laure Mazzola, François Mauguière, Jean Isnard
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...
July 2017: Journal of Clinical Neurophysiology: Official Publication of the American Electroencephalographic Society
Frédéric Blanc, Marc Verny
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...
June 1, 2017: Gériatrie et Psychologie Neuropsychiatrie du Vieillissement
Catherine R Jutzeler, Freda M Warner, Johann Wanek, Armin Curt, John L K Kramer
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)...
January 12, 2017: Scientific Reports
Clare Batty
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...
2014: Frontiers in Psychology
Richard J Stevenson, Mehmet K Mahmut
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...
June 2013: Consciousness and Cognition
Richard J Stevenson, Anina Rich, Alex Russell
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...
2012: Perception
Dana M Small
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...
November 5, 2012: Physiology & Behavior
Maya Shankar, Christopher Simons, Baba Shiv, Samuel McClure, Carmel A Levitan, Charles Spence
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...
October 2010: Attention, Perception & Psychophysics
Dennis Bellmann, Arnd Richardt, Robert Freyberger, Nidhi Nuwal, Martin Schwärzel, André Fiala, Klemens F Störtkuhl
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...
2010: Frontiers in Behavioral Neuroscience
B S Kasper, E M Kasper, E Pauli, H Stefan
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...
May 2010: Epilepsy & Behavior: E&B
I Rodríguez-Constenla, I Cabo-López, P Bellas-Lamas, E Cebrián
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...
February 8, 2010: Revista de Neurologia
Gilles Fénelon, Guido Alves
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%...
February 15, 2010: Journal of the Neurological Sciences
Deborah I Friedman, Timothy De ver Dye
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...
June 2009: Headache
Thomas Hassenklöver, Peter Schwartz, Detlev Schild, Ivan Manzini
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...
August 2009: Stem Cells
Nico J Diederich, Gilles Fénelon, Glenn Stebbins, Christopher G Goetz
Patients with Parkinson disease (PD) can experience hallucinations (spontaneous aberrant perceptions) and illusions (misinterpretations of real perceptual stimuli). Of such phenomena, visual hallucinations (VHs) and illusions are the most frequently encountered, although auditory, olfactory and tactile hallucinations can also occur. In cross-sectional studies, VHs occur in approximately one-third of patients, but up to three-quarters of patients might develop VHs during a 20-year period. Hallucinations can have substantial psychosocial effects and, historically, were the main reason for placing patients in nursing homes...
June 2009: Nature Reviews. Neurology
Brent Elliott, Eileen Joyce, Simon Shorvon
The purpose of this paper and its pair is to provide a comprehensive review, from the different perspectives of neurology and neuropsychiatry, of the phenomenology and mechanisms of hallucinatory experience in epilepsy. We emphasise the clinical and electrophysiological features, and make comparisons with the primary psychoses. In this paper, we consider definitions and elementary hallucinatory phenomena. Regarding definition, there is a clearly divergent evolution in meaning of the terms delusion, illusion and hallucination in the separate traditions of neurology and psychiatry...
August 2009: Epilepsy Research
Edmund T Rolls
Top-down perceptual influences can bias (or pre-empt) perception. In natural scenes, the receptive fields of neurons in the inferior temporal visual cortex (IT) shrink to become close to the size of objects. This facilitates the read-out of information from the ventral visual system, because the information is primarily about the object at the fovea. Top-down attentional influences are much less evident in natural scenes than when objects are shown against blank backgrounds, though are still present. It is suggested that the reduced receptive-field size in natural scenes, and the effects of top-down attention contribute to change blindness...
2008: Perception
Jelena Djordjevic, Johan N Lundstrom, Francis Clément, Julie A Boyle, Sandra Pouliot, Marilyn Jones-Gotman
We examined whether presenting an odor with a positive, neutral, or negative name would influence how people perceive it. In experiment 1, 40 participants rated 15 odors for their pleasantness, intensity, and arousal. In experiment 2, 30 participants passively smelled 10 odors while their skin conductance (SC), heart rate (HR), and sniffing were recorded. We found significant overall effects of odor names on perceived pleasantness, intensity, and arousal. Pleasantness showed the most robust effect of odor names: the same odors were perceived as more pleasant when presented with positive than with neutral and negative names and when presented with neutral than with negative names...
January 2008: Journal of Neurophysiology
Ryuichiro Hayashi
No abstract text is available yet for this article.
2004: European Neurology
G Morrot, F Brochet, D Dubourdieu
The interaction between the vision of colors and odor determination is investigated through lexical analysis of experts' wine tasting comments. The analysis shows that the odors of a wine are, for the most part, represented by objects that have the color of the wine. The assumption of the existence of a perceptual illusion between odor and color is confirmed by a psychophysical experiment. A white wine artificially colored red with an odorless dye was olfactory described as a red wine by a panel of 54 tasters...
November 2001: Brain and Language
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