Neurophysiology and neuropsychology of the effects of olfactory contextual information on memory processes for words and faces

Research project P 13501 Smelling and memory for words and faces Wilfried LANG 28.06.1999 Sensory organs translate physical information about the individual environment of an organism into a common ,brain language". Associated sensory systems in the brain enable the integration of these different inputs, which then results in meaningful behavior. A major role within this set of processes is played by memory functions. Therefore, the investigation of memory functions is a fascinating field of research. A lot of enthusiastic researchers could augment the understanding of how such processes work in the human brain. First, different memory systems could be defined by psychological measures. Nowadays, modem brain imaging techniques provide the possibility to "look" into the human brain during memory performances and characterize memory functions on physiological and anatomical levels. Much work was done to investigate memory processes related to visual and acoustic information. Explicit (conscious) and implicit (unconscious) memory processes were described. Strikingly, the context of a stimulus during its information processing was found to have a great influence on the kind and the grade of storage into memory. However, less emphasis was placed on the investigation of olfactory information processing, although smelling is known to be the oldest sense concerning its evolutionary age. The close neuroanatomical connections of the olfactory system and systems involved in processes of memory reflect strong physiological associations. In the present project, olfactory stimuli are used as contextual information associated with words and faces, which have to be processed within distinct memory tasks (explicit and implicit memory). Odors are known to have a great influence on several human behaviors but a physiological investigation of the effect of the olfactory system on memory functions is missing. The present project is dealing with this question with the aim to provide a neurophysiological characterisation of odor information processing in relation to implicit (unconscious) and explicit (conscious) memory functions in the human brain.

Odors are subconsciously as well as consciously processed in the human brain. As a result of the present project these two functions can be distinguished with respect to temporal as well as spatial properties. Specifically, the conscious perception of odors was found to significantly affect word and face processing. In particular, high word and face processing is affected by a short simultaneously presented odor. The influence of permanent odor stimulation seems to be gender specific. Women show an increased recognition performance related to word information processing in case of permanent odor stimulation during both the study and the test phases. The results of the present project can be used for clinical investigations as well as for industrial interests. The neurophysiological investigation of interactions between visual and olfactory stimuli represents a new field of research which has the potential of becoming a more widespread topic within cognitive neuroscience. Words and faces are everyday stimuli. In the frame of the present project we investigated influences of odors on word and face processing in the human brain. Using the magnetoencephalography (MEG) brain activities were recorded during visual word and face processing under various olfactory conditions within several experiments. The participants had to follow different instructions by making simple "either/or" decisions related to each presented word or face. For example, one instruction was to decide whether each presented word was living or non living. Answers were given by button presses. The result was that odor influences vary as a function of word or face encoding instruction. In other words, depending on how verbal information is processed in the human brain a simultaneously presented odor does affect it or not. Deep, semantic word encoding is physiologically and psychologically affected by simultaneous conscious odor perception. Obviously, interactions occur at cortical levels of processing resulting in a reduced word recognition performance in case of prior olfactory stimulation during word encoding. Similar results were found during deep face encoding. The comparison of conscious and subconscious olfactory information processing and their separate influences on other information processing is a promising field of research. The present research idea and the results of our study can be used within the clinical field of Alzheimers disease. This is due to the fact that olfaction is impaired already at early stages of the disease. Since we can selectively describe olfactory interactions with language processing this research direction could contribute to an early diagnosis of the Alzheimers disease. A further interesting application of the present research idea is related to marketing concepts. The combination of visually presented products and odors could represent a new strategy in the economical world. However, in the frame of following research projects we want to investigate interactions between olfaction and emotion. A respective research application will be submitted soon.