Learning to (dis)like: The effect of evaluative conditioning with tastes and faces on odor valence assessed by implicit and explicit measurements.

Evaluative conditioning may be an important mechanism for learning food preferences and aversions; however, in both real life and experimental settings it has not been consistently successful. The current study aimed to gain more insight into which underlying factors may contribute to a successful outcome of olfactory evaluative conditioning. Two groups of 18 participants came in on three consecutive days, and were repeatedly exposed to four novel, neutral odors (CS) coupled to varying disliked, neutral, liked, or no stimuli (taste and/or pictures, US), following a 50% reinforcement schedule, leading to 40 odor presentations per session. Liking ratings, as well as changes in the autonomic nervous system were assessed before, during and after conditioning. We were able to induce negative, but not positive, affective changes by pairing neutral odors with tastes and pictures differing in valence. Negative as well as multimodal stimuli appear to be more potent US, since they may be considered more salient. Lastly, results of the current study imply that heart rate is responsive to changes in valence of olfactory stimuli, and perhaps even more sensitive than explicit ratings of liking.

Preliminary safety assessment of an arachidonic acid-enriched oil derived from Mortierella alpina: summary of toxicological data.

An arachidonic acid-enriched oil (AA-oil), derived from Mortierella alpina was subjected to a programme of studies to establish its preliminary safety for use in infant nutrition. This was addressed at two levels: (1) HPLC analysis of metabolites produced by the production strains at various conditions, and (2) an evaluation of the toxicity of the final product. The following studies were carried out on the AA-oil: gene mutation assays in bacteria and mammalian cells in vitro; chromosome aberration assays both in vitro and in vivo and acute and subacute (4-wk) oral toxicity in the rat. No known mycotoxins were produced by the production strains under the conditions tested. Further, the oil did not show mutagenic or clastogenic activity and the acute oral toxicity, expressed as the LD50 value, exceeded 20 ml/kg body weight, that is, 18.2 g/kg body weight. In the subacute oral toxicity study the AA-oil was tested as such and in combination with a docosahexaenoic-enriched oil (DHA-oil) derived from fish oil at a ratio of 2:1 (AA:DHA). This was done because high dose levels of AA may result in adverse effects; DHA can compensate for these effects. Furthermore, human milk contains both AA and DHA at a ratio of AA:DHA of 2 to 3:1. No obvious signs of toxicity were observed. Levels of phospholipids and triglycerides tended to be decreased in the highest dose groups. The no-observed-adverse-effect level of the AA-oil in the subacute 4-wk toxicity study was placed at the highest levels tested, namely 3000 mg AA-oil/kg body weight/day as such and in the combination of 3000 mg AA-oil and 1500 mg DHA-oil/kg body weight/day. This corresponds to an intake of 1000 mg AA/kg body weight/day, which represents approximately 37 times the infant intake of AA in human milk.