Event-related alpha suppression in response to facial motion

This article has been made available through the Brunel Open Access Publishing Fund.While biological motion refers to both face and body movements, little is known about the visual perception of facial motion. We therefore examined alpha wave suppression as a reduction in power is thought to reflect visual activity, in addition to attentional reorienting and memory processes. Nineteen neurologically healthy adults were tested on their ability to discriminate between successive facial motion captures. These animations exhibited both rigid and non-rigid facial motion, as well as speech expressions. The structural and surface appearance of these facial animations did not differ, thus participants decisions were based solely on differences in facial movements. Upright, orientation-inverted and luminance-inverted facial stimuli were compared. At occipital and parieto-occipital regions, upright facial motion evoked a transient increase in alpha which was then followed by a significant reduction. This finding is discussed in terms of neural efficiency, gating mechanisms and neural synchronization. Moreover, there was no difference in the amount of alpha suppression evoked by each facial stimulus at occipital regions, suggesting early visual processing remains unaffected by manipulation paradigms. However, upright facial motion evoked greater suppression at parieto-occipital sites, and did so in the shortest latency. Increased activity within this region may reflect higher attentional reorienting to natural facial motion but also involvement of areas associated with the visual control of body effectors. © 2014 Girges et al

Event-related potential indicators of the dynamic unconscious

The present study applies a new method for investigating dynamic unconscious processes. The method consists of (1) selection of words from patient interview and test protocols that in the clinicians' judgments capture the patients' conscious symptom experience (i.e. [phobia) and the hypothetical unconscious conflict related to the symptom, (2) subliminal and supraliminal presentation of these words, (3) signal analysis of event-related potentials (ERPs) obtained to the word presentations. Eight phobics and three patients suffering from pathological grief reactions served as subjects. A time-frequency (Williams & Joeng, 1989) ERP analysis revealed that subjects' ERPs classified the unconscious conflict words better subliminally than supraliminally, while the reverse was true for the conscious symptom words (t(20) = 2.82, P = .011). The relationship between frequency and latency revealed a similar mirror image pattern for the unconscious conflict and conscious symptom words (F(4/36) = 4.14, P = .007). This method demonstrated that objective, brain-based evidence for unconscious conflict can be obtained.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29875/1/0000225.pd

Conscious and nonconscious processes: An ERP index of an anticipatory response in a conditioning paradigm using visually masked stimuli

This study investigates the nonconscious elicitation of a previously conditioned response by using a differential conditioning paradigm with visually masked affectively valent facial schematics. Electrodermal (skin conductance response [SCR]) and brain (event-related potential [ERP]) activity were main dependent measures. Following a preconditioning phase in which subjects viewed energy masked pleasant and unpleasant facial schematics, conditioning with an aversive shock was established to unmasked presentations of an unpleasant face in a partial factorial design. A postconditioning phase of masked presentations, when compared with the preconditioning phase, revealed how the conditional effect within awareness might affect the same stimuli when presented outside awareness. An adaptive staircase technique was used to establish individual threshold levels, which represented a methodological advance over procedures typically used in visual masking research. The results revealed that responses to the CS+ (unpleasant face) changed significantly in predicted directions from preconditioning to postconditioning phase when compared with responses to the CS− (pleasant face). The SCR results systematically replicated recent Ohman, Dimberg, and Esteves (1988) findings, with the pattern of responses resembling a resistance to extinction effect. A new finding emerged for the brain responses. For the CS+, distinct slow wave activity occurred just before the point at which the shock had been delivered in the conditioning phase; no such activity was found for the CS−. This slow wave activity is similar to what has been described by others as an expectancy wave. The results indicate that an anticipatory process, as indexed by different physiological systems, can be elicited entirely outside awareness. Implications are discussed in regard to the nature of conscious and nonconscious processes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74457/1/j.1469-8986.1994.tb01028.x.pd