Abstract: We measured brain activities with a whole head magnetoencephalograph (MEG) to investigate the influence of a background odor on alphabetical encoding of words in 20 healthy volunteers (10 females). Odor stimulation and control air stimulation were both accomplished with a computer controlled olfactometer by providing permanent stimulation conditions. Behaioral data revealed significantly prolonged reaction times in men under the influence of phenylethyl alcohol (PEA) compared to the control condition. Women did not show a change in reaction time during stimulation with PEA. A comparison of men and women revealed significantly shorter reaction times in women for both the odor condition as well as for the control condition. Analysis of performance accuracy showed no significant differences between the odor and the control condition neither within nor across gender. Analysis of grand-averaged event-related fields and localisation of the underlying equivalent current dipoles (ECD) revealed higher dipole strength in the odor compared to the control condition in the right hemisphere over temporo-parietal brain areas in the time range between 200ms and 500ms after word-onset only in male subjects. Within this time range the gender-specific effect is interpreted to reflect odor related modulation of word processing. The findings suggest gender-specific processing strategies in the present task with implications for differences in hemisphaeric laterality.

Change detection related to peripheral facial expression: an electroencephalography (EEG) study. Khittl, B., Bauer, H., and Walla, P. (2009). Journal of Neural Transmission, in press.

Abstract: Electroencephalography and change detection of emotion expression. A visual letter task was combined with two neutral faces. After a short break another letter task occurred while the peripheral faces remained or randomly changed to joy, anger or disgust. Study participants responded whether they had perceived a change in emotion expression or not. Explicit change detection elicited more positive going EEG amplitudes than change blindness between 750-900ms. A change to disgust elicited largest effects. Furthermore, evidence for implicit change detection occurred.

Multiple aspects related to self-awareness

Multiple aspects related to self-awareness and the awareness of others: an electroencephalography study. Walla, P et al. (2008). Journal of Neural Transmission, 115(7): 983-992.

Abstract: The effect of possessive pronouns on the encoding of pronoun-noun associations (e.g., my garden) was investigated using the electroencephalography (EEG). Following an alphabetical, semantic and a contextual encoding instruction depth of noun processing was varied within three separate experiments in order to manipulate the grade of awareness related to verbal information processing. Only for the semantic encoding task (lexical decision) response time was significantly longer for nouns associated with the pronoun “mein” (German for “my”) than for nouns associated with the pronoun “ein” (German for “a”) although pronouns were not to be consciously processed at all. Following recognition tests related to nouns (without their previously associated pronouns) revealed no significant differences related to the number of correctly identified repeated nouns (hits) depending on the kind of previously associated pronoun. The analysis of neurophysiological data revealed a time range between about 250 ms and 400 ms after stimulus onset within which significant pronoun × electrode interactions occurred. No interaction with depth of word processing was found. Overlaid EEG curves, t maps and low resolution brain electromagnetic tomography (LORETA) demonstrate that in this time range “mein” and “sein” associated conditions elicit similar brain activity, both more negative, compared to the “ein” associated condition over occipital electrodes. On the other hand, at left temporal sites the “mein” condition elicited more negative potentials than both other conditions. It is interpreted that EEG recordings reveal two relevant areas, which are sensitive to the concept of a person (as represented by a personal pronoun) between about 250 ms and 400 ms after stimulus onset. One area is located in the occipital region and can distinguish between personal engagement and a neutral condition and the other area is located in the temporal region and is able to distinguish between oneself and somebody else. Together with our previous MEG results (Walla et al. in Neuropsychologia 45:796–09, 2007) we want to combine the inferences in the frame of the “multiple aspects” hypothesis related to research on self-awareness and the awareness of others.

The dynamic influence of odors

Olfaction and its dynamic influences on word and face processing: Cross-modal integration. Walla, P. (2008), Progress in Neurobiology, 84: 192-209).

Abstract: The article specifies several important aspects related to the sense of smell in vertebrates. The idea that odors exert effects in the human brain though being not consciously perceived is introduced. Functional aspects related to cross-modal sensory interaction between olfaction and vision are highlighted. In particular, studies making use of electrophysiological methods providing high temporal resolution reveal an early processing stage around 300 ms and a later stage around 700 ms after stimulus onset. The early stage has been associated with subconscious olfactory information processing, whereas the later stage most likely reflects conscious odor perception. Specific interactions are described between olfaction and language and between olfaction and face processing in correlation with both stages of olfactory information processing. A consciously perceived odor can negatively affect language and face processing if these stimuli are presented and associated simultaneously, whereas simultaneous subconscious odor processing has the potential to improve memory formation in other stimulus modalities. Strikingly, the subconscious effect seems not to depend on odor valence. Besides a better understanding of the sense of olfaction itself, these findings on cross-modal integration support the idea that neural representations exist for semantic contents (object meaning) independent from particular sensory modalities. These representations can be referred to as meta representations because the information they contain is derived from a great variety of sensory information integrated into a semantic representation of an object. It is suggested that such meta representations represent the basic units for cognition and that they provide inputs during dreaming.

Brain activity evidence of a subconscious self

Self awareness and the subconscious effect of personal pronouns on word encoding: A Magentoencephalography (MEG) study: published in the journal "Neuropsychologia" (Walla et al., 2007, 45: 796-809).

Abstract: The effect of personal pronouns such as "ein" (German for "a"), "mein" (German for "my") and "sein" (german for "his") on the processing of associated nouns was investigated using MEG. Three different encoding strategies were provided in order to vary the level of consciousness involved in verbal information processing. A shallow (alphabetic), a deep (semantic) and a very deep (contextual) encoding instruction related to visual word presentation were given to all study participants. After the encoding of pronoun-noun pairs, recognition performances of nouns only were tested. The number of correctly recognised nouns previously associated with "sein" was significantly lower than the number of correctly recognised nouns previously associated with "ein" in the shallow encoding condition. The same trend was found for "mein" associated nouns which were also less accurately recognised compared to "ein" associated nouns. Magnetic field distributions recorded during the encoding phases revealed two significant effects, one between about 200ms and 400ms after stimulus onset and the other between about 500ms and 800ms. The earlier effect was found over occipito-parietal sensors whereas the later effect occurred over left frontal sensors. Within both time ranges, brain activation varied significantly as a function of associated pronoun independent of depth of word processing. In the respective areas of both time ranges, conditions including personal pronouns ("mein" and "sein") showed higher magnetic field components compared to the control condition of no personal pronouns ("ein"). Evidence is shown that early stage processing is able to distinguish between no personal and personal information whereas later stage processing is able to distinguish between information related to oneself and to another person (self and non-self). Along with other previous reports our MEG findings support the notion that particular human brain functions involved in processing neurophysiological correlates of self and non-self can be identified.