Marty G. Woldorff - US grants

DESCRIPTION(adapted from applicant's abstract): The ability to selectively focus attention on portions of our sensory input is a critical brain function that enables us to enhance the processing of high priority stimuli in the environment. For example, a person can listen selectively to one speaker's voice while tuning out several other simultaneous conversations. With vision, attending to a particular part of the visual field results in faster and better discrimination of stimuli in that region of space. The selective averaging capabilities and high temporal resolution of event-related potentials (ERPs) have provided considerable insight into the timing of attention-related brain mechanisms; however, it has proven difficult to precisely specify their anatomical sources. Studies of attention using positron emission tomography (PET) and block-design functional magnetic resonance imaging (fMRI), on the other hand, have identified a number of key brain regions that are part of the circuitry underlying attention, but these studies do not provide information on the timing of the neural activity in the identified brain regions. The present project combines ERPs with fMRI to study both the functional neuroanatomy and timing of visual and auditory attention mechanisms, including attentional filtering of sensory inputs in visual and auditory cortices, the relationship between voluntary attention and putatively automatic sensory-analysis processes, and the neural circuitry of top-down attentional control. Toward these goals, we will incorporate analytic methods that will permit the isolation of brain activity for different aspects of attention and task performance. Five studies -- two visual, two auditory, and one combined auditory and visual -- are proposed, in which normal subjects will perform attention tasks while fMRI scans and high-density ERPs of their brain activity are recorded. These functional imaging data sets will be combined and mapped onto the corresponding structural MM images to investigate the functional circuitry and mechanisms underlying visual and auditory attention in humans. This research has important implications for mental health problems, because disturbances in selective attention contribute to various clinical disorders, including schizophrenia, attention deficit disorder, Alzheimer's disease, hemineglect syndrome, and learning disabilities. The proposed experiments will enhance our understanding of the activation patterns and mechanisms underlying both normal and disordered attention.

The ability to focus attention on elements of our sensory environment is a critical cognitive function that enables one to enhance the processing of high priority stimuli. A classic auditory example is the "cocktail party effect," in which a person can focus selectively on a particular speaker while tuning out other conversations. In vision, attending to a particular region of the visual field results in faster and better discrimination of stimuli in that region. In recent years, both electrophysiological and functional brain imaging studies have suggested that a network of frontal and parietal brain areas enables selective attention by enhancing the responses in sensory cortices in favor of task-relevant stimuli. Almost all studies of attention, however, have been conducted within a single sensory modality. The real world is multisensory, numerous real objects have multisensory characteristics (e.g., both auditory and visual aspects) that need to be attended, perceived, and integrated. With funding from the National Science Foundation, Dr. Marty Woldorff is combining electrical and functional imaging measures of brain activity to study the mechanisms by which attention operates in a multisensory world. This includes the study of (1) whether there are separate attentional resources for processing stimuli in different sensory modalities, (2) how attention influences multisensory integration processes, and (3) how attention may spread from one sensory modality to another in a multisensory object. Recording both electrical and functional imaging measures of brain activity during the performance of multisensory attentional tasks will reveal the location, timing, and sequence of the brain mechanisms underlying multisensory attentional processes.

The broader impacts of this project relate to the fact that the real world is multisensory, but the mechanisms by which attention operates in multisensory circumstances are far from understood. As just one example, every day millions of motorists drive on streets and highways in the multisensory environment of a car, in which they must cope with a myriad of visual and auditory sensory inputs, including police sirens, car horns, radios, talking passengers and misbehaving children. Understanding processing limitations and how attention facilitates performance by influencing multisensory interactions is of fundamental importance for understanding the performance of such everyday real-life activities. Moreover, understanding these mechanisms could have a large, practical impact on matters ranging from the training of drivers to the design of cars and cockpits. The present work also has impact for understanding the mechanisms by which people integrate the auditory content of speech with the visual input of mouth and head movements, a function fundamental for human beings everywhere. Lastly, gaining basic scientific understanding concerning how attention operates in multisensory circumstances has impact not only for individuals with normal perceptual and attentional capabilities, but also for individuals in whom such capabilities have been impaired through injury or other causes.

Attention is a critical cognitive function that allows us to dynamically select and enhance the processing of the stimuli in our environment that are the most relevant or highest priority at each moment. Directing attention to a stimulus leads to lower perceptual thresholds, faster reaction times (RTs), and increased discrimination accuracy. In the previous grant period, this project used functional magnetic resonance imaging (fMRI) and scalp-recorded event-related potentials (ERPs) to investigate the neural mechanisms of attention. These included studies of the modulatory effects of attention on processing in the sensory pathways, the top-down control mechanisms that accomplish that modulation, executive and attentional processes related to stimulus conflict, and intermodal attentional processes. Another critical cognitive function is our ability to rapidly and correctly perceive stimuli and cues related to, and important for, successful social interactions. In previous work, we have also investigated the brain mechanisms underlying various aspects of social perception. This has included work focused on identifying the functions subserved by specific brain regions, including the role of the fusiform gyrus (FFG) and superior temporal sulcus (STS) regions in the processing of faces and eye gaze. In the currently proposed project, we aim to fully integrate these two lines of inquiry and investigate the neural and cognitive interactions between the systems involved in the control of visual spatial attention and those involved in social perception, particularly those related to the processing of faces, face emotion, and eye gaze. We will study these interactions both from a top-down standpoint (i.e., the influence and importance of attention on the processing of these socially relevant stimuli) and from a bottom-up standpoint (i.e., how these factors can attract, capture, and/or otherwise influence our attention). We will use both fMRI and scalp-recorded ERPs to investigate these interactions in order to delineate not only the brain areas involved in these interactions, but also the timing and sequence of their activations, thereby enhancing our understanding of the underlying mechanisms. A variety of neurological disorders, such as attention-deficit disorder, Alzheimer's disease, and autism, have adverse effects on both attentional and social perception capabilities. Traumatic brain injury following stroke can also result in dramatic impairments in attention, social perception, and affective processing. The proposed studies will provide important information that can be used to better understand these neurological disorders and develop effective treatments.

Our ability to selectively focus attention on elements of our sensory environment is a critical cognitive function that enables us to enhance the processing of high priority stimuli. A classic example is the "cocktail party" effect, in which a person can focus selectively on a particular speaker while tuning out other conversations. In vision, attending to a particular region of the visual field results in faster and better detection and discrimination of stimuli in that region. Both electrophysiological and hemodynamic brain imaging studies have shown that top-down executive attentional mechanisms can influence early sensory processing in modality-specific cortices. Recent studies using event-related functional MRI (fMRI) in humans have implicated a fronto-parietal network in the executive control of visual attention. As yet, however, relatively little work has investigated how attention is switched or coordinated between sensory modalities. Thus, it is not yet clear which brain mechanisms, regions, and resources controlling attention are supramodal and which are modality specific. Moreover, real objects, including speakers at cocktail parties, have multisensory characteristics that need to be attended, perceived, and integrated. Because multisensory integration involves synthesis of information derived from different sensory channels, it is not clear that the same attentional mechanisms will be operative in a multisensory environment as are employed in a unisensory situation. For example, attention to one feature or aspect of a multisensory object (e.g., the face of a speaker) might lead to a cross-modal spreading of attention (e.g., to encompass the speaker's voice). The present project proposes to combine event-related potentials (ERPs) and event-related fMRI to study the mechanisms by which attention operates in multisensory environments. This will include the study of executive control mechanisms and brain circuits that coordinate and switch attention between different sensory modalities, as well as how attention influences and interacts with the processing and integration of multisensory stimuli. Recording both ERP and fMRI measures of brain activity during the attentional tasks will reveal not only the brain areas that subserve multisensory attentional operations, but also the timing and sequence of their activations, thereby enhancing our understanding of the underlying mechanisms. Attentional deficits form key components of a variety of neurological disorders and mental illnesses, and thus elucidating the basic

ABSTRACT The ability to selectively focus attention on elements of our sensory environment is a critical cognitive func- tion that enables us to dynamically and flexibly enhance the processing of the most important stimuli, events, and tasks. Likewise, stimulus-reward associations and the potential for gaining reward on a task have also been found to enhance stimulus processing and influence behavior. There has been a growing recognition that these two core cognitive factors ? attention and reward ? interact extensively to shape cognition and behavior. In the next period of this grant, we propose a series of experiments investigating this vital interactive relation- ship between reward and attention. In particular, in Aim 1 we examine how cueing with advance information on locationally specific reward-magnitude potential and classic cueing of locational probability (Posner cueing) proactively shape attentional allocation and task performance. In contrast, in Aim 2 we examine how reward selectively associated with target-relevant stimuli or distractors in a visual-search attention task influences at- tentional and perceptual processes (Aim 2). We also expand our study of the interactive relationship between reward and attention to examine their interactions in audition, thereby also investigating the supramodality of these mechanisms (Aim 3). Lastly, we will also examine how stimulus-reward associations are updated in the sensory cortices by means of top-down modulatory mechanisms (Aim 4). An overarching working hypothesis in these studies is that a key way by which reward enhances task performance is by marshalling attentional control circuits that in turn allocate processing resources in the brain. We take a highly systems-oriented perspective in these studies: examining both (a) the attention- and re- ward-related cognitive-control mechanisms as they allocate and direct processing resources, and (b) markers of the modulations of those processing resources in the sensory cortices. As before, we will be taking a multi- methodological approach, using a combination of behavioral measures, event-related potentials (ERPs), event- related oscillatory EEG, and functional MRI (fMRI) to delineate the timing, sequence, and location of the under- lying neural processes and interregional neural interactions. Additionally, we will use simultaneous recordings of fMRI and EEG for several of the proposed experiments. Such an approach will enable us to perform trial-to- trial covariational analyses on the data patterns of these two measures of brain activity, providing powerful new ways to link the high-temporal-resolution EEG signals to the associated cortical generators measured in the fMRI. Moreover, the simultaneous recording will also allow us to examine how subcortical brain regions in- volved in attention and reward modulate the functional processes reflected by the cortical EEG ? reflecting crit- ical aspects of processing that cannot be assessed when these measures are acquired separately. Thus, these experiments will delineate with exceptional precision the neural mechanisms by which attentional and reward-related processes interact in the human brain and contribute to adaptive behavior in our complex world.