ABSTRACT
The ability to identify safety and danger is critical to survival. However, not much is known about human somatic body reactions in these contexts. We performed a posturographic study comparing body reactions to the sight of pictures of smiling babies and families (affiliative) versus matched neutral people, and to pictures depicting body envelope violations (mutilation) versus matched neutral people. The participants stood on a force platform and heart rate and displacement of the center of pressure were recorded while the pictures were presented. Pictures of mutilation induced a freezing-like reaction consisting of a medial-lateral (M-L) decrease in the amplitude of sway (immobility) and increase of the mean power frequency (rigidity), associated with bradycardia. Affiliative stimuli also induced an immobility and rigidity behavior but in the anterior-posterior (A-P) axis. This resembles the "immobility-without-fear reaction" proposed to occur when, upon detection of safety cues, mammals including humans are involved in pro-social activities. We conclude that the sight of visual cues of affiliation and danger produce distinct body somatic reactions.
Subject(s)
Emotions/physiology , Postural Balance/physiology , Posture/physiology , Visual Perception/physiology , Adolescent , Adult , Electroencephalography/methods , Female , Humans , Male , Photic Stimulation/methodsABSTRACT
A emoçäo pode ser funcionalmente considerada como uma disposiçäo à açäo que prepara o organismo para comportamentos relacionados à aproximaçäo e esquiva. Para preparar uma saída motora apropriada, o organismo tem que ser eficiente na codificaçäo de estímulos relevantes. Neste trabalho, apresentamos evidências a partir de estudos de neuroimagem que revelam que a visualizaçäo de imagens emocionais promove uma maior ativaçäo do córtex visual do que a observaçäo de figuras neutras. Além desta facilitaçäo do processamento sensorial, os estímulos emocionais desencadeiam reaçöes somáticas e vegetativas. Registros da dinâmica postural e da freqüência cardíaca enquanto voluntários assistiam a um bloco de figuras desagradáveis revelou uma reduçäo significativa na oscilaçäo corporal e bradicardia. Uma investigaçäo paralela mostrou que o tempo de reaçäo também lentifica após a visualizaçäo de figuras negativas. Este conjunto de respostas - imobilidade, bradicardia e tempo de reaçäo mais lento - pode refletir o engajamento do sistema defensivo, similar às reaçöes defensivas desencadeadas em ambiente natural por estímulos ameaçadores distantes. Em resumo, o sistema afetivo influencia um nível precoce de codificaçäo sensorial e a saída motora favorecendo, portanto, disposiçöes para as açöes apropriadas
Subject(s)
Humans , Visual Cortex/physiology , Emotions/physiology , Arousal/physiology , Visual Perception/physiology , Immobility Response, Tonic/physiology , Reaction Time/physiologyABSTRACT
Emotion can be functionally considered as action dispositions preparing the organism for either avoidance- or approach- related behaviors. In order to prepare an appropriate behavioral output, the organism has to be efficient in the encoding of relevant stimuli. We herein present evidence from neuroimaging studies that seeing emotional and arousing pictures leads to greater activation in visual cortex than seeing neutral ones. In addition to this facilitation of sensory processing, emotional stimuli prompt somatic and vegetative reactions. Recordings of postural oscillations and heart rate while participants visualized a block of unpleasant pictures, revealed a significant reduction of body sway and bradycardia. A parallel investigation showed that reaction time also slows down after the visualization of negative pictures. Taken together, immobility, bradycardia and slower reaction time in the laboratory experimental set may reflect the engagement of the defensive system, resembling the defensive reactions to distant threatening stimuli in natural contexts. In summary, the affective system operates at an early level of sensory encoding and at the motor output favoring dispositions for appropriate actions.
