Suppressive Modulation of the Chick Forebrain Network for Imprinting by Thyroid Hormone: An in Vitro Study.

The thyroid hormone 3,5,3'-triiodothyronine (T3) is considered to act acutely in the chick forebrain because focal infusion of T3 to the intermediate medial mesopallium (IMM) causes 4 to 6-day-old hatchlings to become imprintable approximately 30 min after the infusion. To understand the mechanism of this acute T3 action, we examined synaptic responses of IMM neurons in slice preparations in vitro. Extracellular field potential responses to local electrical stimulation were pharmacologically dissociated to synaptic components mediated by AMPA and NMDA receptors, as well as GABA-A and -B receptors. Bath-applied T3 (20-40 µM) enhanced the positive peak amplitude of the field potential, which represented the GABA-A component. Bicuculline induced spontaneous epileptic bursts by NMDA receptor activation, and subsequent application of T3 suppressed the bursting frequency. Pretreatment of slices with T3 failed to influence the synaptic potentiation caused by tetanic stimulation. Intracellular whole-cell recording using a patch electrode confirmed the T3 actions on the GABA-A and NMDA components. T3 enhanced the GABA-A response and suppressed the NMDA plateau potential without changes in the resting membrane potential or the threshold of action potentials. Contrary to our initial expectation, T3 suppressed the synaptic drives of IMM neurons, and did not influence activity-dependent synaptic potentiation. Imprinting-associated T3 influx may act as an acute suppressor of the IMM network.

Human brain activity reflecting facial attractiveness from skin reflection.

Facial attraction has a great influence on our daily social interactions. Previous studies have mainly focused on the attraction from facial shape and expression. We recently found that faces with radiant skin appear to be more attractive than those with oily-shiny or matte skin. In the present study, we conducted functional magnetic resonance imaging (fMRI) and psychological experiments to determine the human brain activity that reflects facial attractiveness modulated by these skin reflection types. In the fMRI experiment, female subjects were shown successive images of unfamiliar female faces with matte, oily-shiny, or radiant skin. The subjects compared each face with the immediately preceding face in terms of attractiveness, age, and skin reflection, all based on the skin. The medial part of the orbitofrontal cortex (mOFC) was significantly more active when comparing attractiveness than when comparing skin reflection, suggesting that the mOFC is involved in processing facial attractiveness from skin reflection. In the psychological experiment, attractiveness rating was highest for radiant skin, followed by oily-shiny, and then matte skin. Comparison of the results of these experiments showed that mOFC activation level increased with attractiveness rating. These results suggest that the activation level of the mOFC reflects facial attractiveness from skin reflection.

Facial radiance influences facial attractiveness and affective impressions of faces.

OBJECTIVE: Facial attractiveness has been reported to be influenced by visual features such as facial shape and the colour and texture of the skin. However, no empirical studies have examined the effects of facial skin radiance on facial attractiveness. The present study investigated whether types of skin reflection (i.e. radiant, oily and shiny, and matte) and the position of the reflection on the face influence facial attractiveness and other affective impressions. METHODS: A total of 160 female participants (1) estimated the ages and (2) evaluated attractiveness and other impressions of unfamiliar female faces in a total of seven skin reflection conditions. These conditions incorporated three types of reflection (i.e. radiant, oily and shiny, and matte) and three positions of the reflection on the face (i.e. entire facial skin, only cheeks, and only T-zone). RESULTS: The facial images of radiance on entire faces were rated as appearing younger than the facial images of oily shine on entire faces and the matte faces. Attractiveness ratings and other positive impressions increased in the order of the matte (ranked lowest), the oily shine on entire face, and the radiance on entire face (ranked highest) conditions. The reflection position also influenced facial attractiveness: attractiveness ratings and other positive impressions were higher in the radiance on entire face condition than in the radiant cheeks and the radiant T-zone conditions. Interestingly, the radiant cheek faces were rated more radiant and healthier but less feminine and less bright than the radiant T-zone faces. CONCLUSION: These results suggest that facial radiance enhances facial attractiveness and conveys a wide variety of positive impressions on the observer. The magnitude of the effects of cheek radiance and T-zone radiance differs across various affective impressions. Nevertheless, the results demonstrate that cheek and the T-zone radiance both contribute to higher attractiveness and other positive impressions of the radiance on entire faces. We believe that our findings can contribute as a guide to the enhancement of positive facial impressions by means of skin radiance, thereby leading to a better understanding of the value of skincare and base makeup.

OBJECTIF: Selon certaines études, l'attractivité du visage viendrait de caractéristiques visuelles telles que la forme du visage ainsi que la couleur et la texture de la peau. Cependant, aucune étude empirique n'a examiné les effets de l'éclat de la peau sur l'attractivité du visage. La présente étude s'est intéressée aux divers types de reflets de la peau (par exemple une peau lumineuse, une peau grasse et luisante ou une peau mate) et à leur position sur le visage, et a cherché à savoir s'ils influençaient l'attractivité du visage et d'autres impressions d'ordre affectif. MÉTHODES: Au total, 160 participantes 1) ont estimé l'âge et 2) ont évalué l'attractivité et d'autres impressions de visages féminins inconnus sur sept types de reflets de la peau au total. Ces états comprenaient trois types de reflets (lumineux, gras et mat) et trois positions des reflets sur le visage (toute la peau du visage, joues uniquement et partie yeux-nez [« zone T ¼] uniquement). RÉSULTATS: Les photos de visages caractérisées par un éclat sur tout le visage ont été considérées comme étant plus jeunes que celles dont la peau était grasse-luisante sur l'ensemble du visage et que les visages à peau mate. Les notes attribuées pour l'attractivité et les autres impressions positives augmentent dans l'ordre suivant : peau mate (note la plus basse), peau grasse-luisante sur tout le visage et luminosité sur tout le visage (note la plus haute). La position du reflet a elle aussi joué un rôle sur les notes attribuées à l'attractivité des visages, et les autres impressions positives ont obtenu des scores plus élevés pour une luminosité de tout le visage que pour des joues lumineuses et une zone T lumineuse. Il est intéressant de noter que les visages aux joues lumineuses ont été jugés plus lumineux et plus sains, mais moins féminins et moins éclatants que les visages présentant une zone T lumineuse. CONCLUSION: Ces résultats suggèrent que l'éclat du visage améliore l'attractivité du visage et communique toutes sortes d'impressions positives à l'observateur. L'ampleur des effets de l'éclat sur les joues et sur la zone T diffère selon les différentes impressions d'ordre affectif. Néanmoins, les résultats démontrent que la luminosité des joues et de la zone T contribue à rendre le visage plus séduisant ainsi qu'à d'autres impressions positives suscitées par la luminosité de l'ensemble du visage. Nous sommes convaincus que nos résultats peuvent servir à guider la façon de renforcer l'impression positive produite par un visage en faisant ressortir la luminosité de la peau, et amener ainsi à mieux comprendre la valeur des soins de la peau et des bases de maquillage.