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Neurotransmitter imaging

Conscious-nonconscious interaction

Images:
o Implicit and explicit memory and their interaction
o Cross modality priming and the effect of divided attention
o Within modality auditory priming and the effect of change in voice

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My research is primarily focused on the study of brain networks involved in conscious and nonconscious information processing. To understand these networks I use a single-scan dynamic molecular imaging technique, which we recently developed to detect, map and measure dopamine released in the human brain during cognitive, emotional and behavioral processing. The technique uses positron emission tomography (PET) and provides a unique opportunity to study neurochemical changes associated with the brain processing. In addition to this technique, I use functional MRI to localize brain areas involved in processing of various aspects of human conscious and nonconscious experiences. Further, I exploit the ability of dynamic molecular imaging to detect acute changes in the brain neurotransmission to study neuropathology of psychiatric and neuropsychiatric conditions. 

To understand the neural network involved in processing of conscious experiences I studied conscious and nonconscious memory in a series of neuroimaging experiments. These experiments characterized the nature of processing and indicated that the area V3A, located at the parieto-occipital junction is a critical component of the neural network that allows us to become consciously aware of a stimulus. To further characterize the nature of processing in this area I conducted neuroimaging studies of the auditory and cross modal priming and found that the processing in the area V3A is independent of the sensory modality. Further, my experiments on subliminal stimuli demonstrated that conscious perception of stimuli is not necessary for initiation of cognitive processing. This finding provides important objective data to help resolve the debate on the nature of stimuli that elicit cognitive processing.

In another series of experiments I demonstrated simultaneous activation of multiple areas of the cingulate cortex during processing of different components of executive functions. The finding for the first time suggested that different aspects of the executive function are processed at distinct specialized neuronal clusters within the anterior cingulate. Based on this finding I formulated a neural model of the brain executive system. This model is a part of the curricula of a number of institutions.