Biomedical subjects

Johann Lehrner

Publications and source records attributed to Johann Lehrner.

5 recordsLinked to original sources

PubMed2006

Does modification of olfacto-gustatory stimulation diminish sensory-specific satiety in humans?

UNLABELLED: Alimentary sensory pleasure is an important factor in ingestive behavior. Renewal of olfacto-gustatory pleasure by introducing new foods or through seasoning of previously consumed food might increase intake. OBJECTIVES: To explore whether sensory-specific satiety (SSS) for a food could be modulated, either by introducing a novel food or by a modification of sensory stimulation via seasoning the food just eaten. METHODS: 180 out of 242 subjects were distributed over 3 experiments involving ad libitum intake of one of 6 fresh foods (cucumber, tomato, pineapple, banana, peanut, pistachio). Blindfolded subjects reported their sensations for the foods on 3 parameters before and after intake of an olfactorily chosen food: Olfactory pleasure (OP), Specific appetite (SA) and Stimulus-Induced Salivation (SIS). EXP. 1: One chosen food was repeatedly presented orthonasally and rated before and after it was eaten. EXP. 2: A second food was olfactorily chosen and ingested after the first one. EXP. 3: The same food was offered again after seasoning. RESULTS: 2 min after ingestion, food intake was limited by SSS. OP, SA, SIS correlated with each other for eaten and non-eaten foods. OP for non-eaten foods increased (p<0.01) after ingestion of the chosen food to specific satiety. When the food just eaten was seasoned, OP increased (p<0.01) and led to additional intake (80% of first intake). CONCLUSION: A reduction in SSS after introduction of a new flavor or after seasoning an ingested food was observed. Such a reduction has not previously been reported. This could hint at how food sensory variation leads to over-consumption.

Adolescent↗

PubMed2005

Annual conversion to alzheimer disease among patients with memory complaints attending an outpatient memory clinic: the influence of amnestic mild cognitive impairment and the predictive value of neuropsychological testing.

OBJECTIVE: The goals of this study were to determine the annual conversion rate to Alzheimer disease (AD) among patients reporting memory problems, including a subgroup with amnestic mild cognitive impairment (aMCI), and to investigate the predictive value of neurocognitive testing for future dementia. METHODS: A prospective study was carried out in an outpatient memory clinic. One hundred and seven patients underwent a clinical examination and completed a battery of standard cognitive tests at study entry and two years later. The conversion rate to clinically manifested AD two years later was investigated and sensitivity, specificity, receiver operating characteristics (AUC), positive predictive value and negative predictive value for each neuropsychological test were determined. RESULTS: We found an annual rate of conversion to AD of 6.5% among patients reporting memory decline in the setting of our clinic. Specifically, patients with aMCI had an annual conversion rate of approximately 20%. The annual conversion rate for patients reporting memory problems but showing no memory deficit at memory testing was approximately 3%. Receiver operating characteristics (AUC) of the neuropsychological tests ranged from 0.60 to 0.94. CONCLUSIONS: Patients with aMCI have 8.6-fold higher odds of developing AD compared with patients without evident memory impairment on neuropsychological testing. Although the risk of developing AD among patients without objective memory decline is small, some patients in this group still convert to AD and therefore close clinical monitoring of patients is necessary.

Aged↗

PubMed2003

Olfaction and depth of word processing: a magnetoencephalographic study.

Using a whole-cortex magnetoencephalograph, magnetic field changes were recorded to describe brain activities related to simultaneous visual and olfactory processing and to detect odor-related influences on verbal information processing. Words had to be either shallowly (nonsemantic) or deeply (semantic) encoded by healthy young subjects, each of these tasks under two different kinds of olfactory stimulation. After each encoding phase, word recognition performance was tested. First, the odor was randomly associated with some of the study words (simultaneous stimulation; same duration as for words) for both depths of word processing conditions, and second, continuous olfactory stimulation (permanent stimulation) was provided during the whole study phases of both depths of word processing conditions. The statistical analysis of the physiological data revealed evidence of a specific odor-induced effect depending on depth of word processing and kind of olfactory stimulation. Brain activity between about 250 and 450 ms as well as between about 650 and 1000 ms after stimulus onset was found to vary as a function of odor delivery and depth of word processing. In addition, a significant effect of odor stimulation on subsequent word recognition performance occurred in case of simultaneous odor stimulation and semantic word encoding. It is interpreted that in this case, word recognition performance significantly decreased because of the presence of the odor during prior word encoding. Such a behavioral effect was missing in all other conditions. The present psychological and physiological findings support the idea that semantic word encoding is specifically affected by simultaneous olfactory information processing. It is concluded that this phenomenon is due to a competition with cortical regions related to language and olfactory information processing, as suggested by T. S. Lorig (1999, Neurosci. Biobehav. Rev. 23, 391-398).

Adult↗

PubMed2003

Olfaction and face encoding in humans: a magnetoencephalographic study.

Magnetic field changes were recorded while 20 healthy young participants performed a deep face encoding task. Some of the faces were randomly associated with a simultaneously presented odor. A recognition test, during which all faces were presented again together with the same number of new faces, followed. The task was to discriminate between repeated and new faces. During the recognition test no odor was presented. The recognition performance was significantly influenced by the simultaneously associated odor during the encoding phase. Faces associated with odor were less accurately recognized. In addition, we found significant physiological differences between 'encoded faces without odor' and 'encoded faces with odor'. In particular, two effects occurred. Between about 200 and 300 ms after stimulus onset 'encoded faces without odor' evoked higher brain activity than 'encoded faces with odor'. Between about 600 and 900 ms after stimulus onset 'encoded faces with odor' evoked higher brain activity than 'encoded faces without odor'. Whereas the latter effect is interpreted as reflecting conscious olfactory information processing, the earlier effect is suggested to reflect an odor influence on face encoding. We suggest that the simultaneous odor association distracted face encoding resulting in a significantly reduced recognition performance. These findings are suggested to represent evidence of multimodal sensoric interactions between visual face processing and olfactory information.

Adult↗

PubMed2002

Evidence of conscious and subconscious olfactory information processing during word encoding: a magnetoencephalographic (MEG) study.

The present study was meant to distinguish between unconscious and conscious olfactory information processing and to investigate the influence of olfaction on word information processing. Magnetic field changes were recorded in healthy young participants during deep encoding of visually presented words whereby some of the words were randomly associated with an odor. All recorded data were then split into two groups. One group consisted of participants who did not consciously perceive the odor during the whole experiment whereas the other group did report continuous conscious odor perception. The magnetic field changes related to the condition 'words without odor' were subtracted from the magnetic field changes related to the condition 'words with odor' for both groups. First, an odor-induced effect occurred between about 200 and 500 ms after stimulus onset which was similar in both groups. It is interpreted to reflect an activity reduction during word encoding related to the additional olfactory stimulation. Second, a later effect occurred between about 600 and 900 ms after stimulus onset which differed between the two groups. This effect was due to higher brain activity related to the additional olfactory stimulation. It was more pronounced in the group consisting of participants who consciously perceived the odor during the whole experiment as compared to the other group. These results are interpreted as evidence that the later effect is related to conscious odor perception whereas the earlier effect reflects unconscious olfactory information processing. Furthermore, our study provides evidence that only the conscious perception of an odor which is simultaneously presented to the visual presentation of a word reduces its chance to be subsequently recognized.

Adult↗