Tours / Demonstrations Psychology Department 119 Minard 9 : 30 a

s of Presentations Linda Langley, North Dakota State University “Aging and the Role of Inhibition and in Visual Search” The goal of this project is to determine the cognitive mechanisms that contribute to adult age differences in visual search, focusing on inhibitory mechanisms. Inhibition of return (IOR), a phenomenon of attentional orienting that is indexed by slower response times to targets presented at previously attended locations, is considered largely intact with age. This talk will describe the findings of three grant-funded studies that examined age differences in IOR. Two studies found age differences in the temporal resolution and spatial distribution of IOR. A third study found similar patterns of inhibition for younger and older adults within a complex search environment. Studies that use eye tracking and electrophysiological techniques to explore aging and inhibition will also be discussed. Patricia Reuter-Lorenz, University of Michigan “Affective Working Memory: Converging Evidence for a New Construct” In daily life emotional feeling states come and go, often influencing our thoughts, decisions and actions in ways that we may or may not recognize. Given the seeming automaticity of emotions, the idea that our mental architecture might include a kind of workspace or working memory for emotion may seem counterintuitive. However, Davidson & Irwin (1999) made just this claim when they proposed the existence of affective working memory. To date there has been little empirical work to directly address the viability of this construct. I will present an overview of new converging evidence from behavioral studies of younger and older adults, and neuroimaging results to support the idea that working memory includes a separable subsystem for the on-line maintenance of affective representations. Affective working memory may serve a vital role in evaluative judgments and decision-making. Robert D. Gordon, North Dakota State University “Selective Attention During Scene Perception” A key to understanding the perception and representation of complex scenes lies in determining the factors that guide attention during scene viewing. In a series of experiments, I have investigated the influence of scene semantics on the allocation of attention. The results of such experiments suggest that attention is drawn preferentially to the locations of inconsistent objects, whose identities conflict with the scene context. Two accounts of this effect will be described, and evidence will be presented that is supportive of one account: that attention is drawn to inconsistent objects because they represent areas of perceptual dysfluency. Thus, semantic factors appear to influence attentional allocation during scene perception by affecting the ease with which objects in the scene are identified. Arthur Kramer, University of Illinois “Aging and Multi-Task Performance: In and Out of the Lab” I’ll speak about our recent research on two distinct but related topics. First, I will briefly describe some of our research on optimizing driver performance across the adult lifespan through the use of collision avoidance devices. Studies in a variety of driving environments with increasing levels of complexity will be examined. Second, I will discuss some of our recent research on changes in the neural circuits, as indexed by event-related fMRI, as a function of adaptive multi-task training with young and older adults. Chris Kelland Friesen, North Dakota State University “Orienting in Response to Directional Cues” My research program is aimed at understanding how, and under what circumstances, humans will orient spatial attention in response to directional cues, such as arrows or another person's eye gaze direction, in the visual environment. Using traditional experimental cuing methods, researchers have shown that nonpredictive centrallypresented directional cues can produce a shift of spatial attention that is reflexive or automatic in nature. After presenting background information on orienting to directional cues and comparing this orienting with traditionally-studied exogenous and endogenous orienting, I will describe some current and recently-completed directional cuing experiments conducted in my laboratory. One recent study tested the reflexivity of this orienting by presenting gaze and arrow cues under conditions of unawareness of the cue. A second recent study compared orienting to nonpredictive gaze cues, arrow cues, and peripheral sudden onset cues within the same subjects. In this study, the time course of reflexive orienting in response to these three cue types was examined by varying both cue-to-target SOA and cue duration. A third withinsubject study (in progress), which is pilot work for an ERP study, examines the time course of orienting in response to both spatially predictive and spatially nonpredictive gaze, arrow, and symmetrical symbolic cues. In this study, the goal is to identify exogenous and endogenous components associated with central directional cues that either do or do not have inherent visual properties indicating directionality. Finally, I will outline plans for future studies arising from the results of these studies, as well as plans for several other related research projects. Wolfgang Teder-Sälejärvi, North Dakota State University “Selective Attention to Rapid Tactile Stimuli – ERPs and Source Localization” We investigated the time course and scalp topography of ERPs to rapidly presented tactile stimuli in 15 human subjects. High density EEG and EOG recordings were acquired from 62 electrodes, referenced to the averaged mastoids (bandpass 0.1-100 Hz, sample rate 250 Hz, excessive blinks and eye movements rejected offline). Brief tactile stimuli of 10 ms duration were delivered via four actuator rods (1 mm tip diameter) to the pointer fingers (frequent standard stimuli, p=.45) or middle fingers (infrequent deviant target stimuli, p=.05) of each hand. The inter-stimulus interval (rectangular distribution) varied between 270 and 540 ms. The subject’s task was to press a footswitch to targets appearing either at the left or right middle finger in separate runs. Inspection of the grand-average standard-stimulus waveforms and topographical iso-voltage maps revealed a slightly lateralized, relatively sharp early negative component (N45) with a maximum over fronto-central cortex. This early component inverted in polarity over centro-parietal sites and was influenced by the direction of attention. We also observed attention-driven, lateralized modulations of a later component with a central distribution, peaking at about 130 ms. John Foxe, Nathan S. Kline Institute for Psychiatric Research “Spatiotemporal Dynamics of Human Object Recognition Processing: Integrated high-density electrical mapping, functional imaging and human intracranial studies of ‘perceptual closure’ processes” Humans are capable of recognizing objects, often despite highly adverse viewing conditions (e.g. fog, occlusion, camouflage etc.). The term “perceptual closure” has been used to refer to the neural processes responsible for “filling-in” missing information in the visual image under such conditions. Closure phenomena have been linked to a group of object recognition areas, the so-called lateral occipital complex (LOC). Here we investigated the spatio-temporal dynamics of perceptual closure processes by co-registering data from high-density electrical recordings (ERPs) and functional magnetic resonance imaging (fMRI) while subjects participated in a perceptual closure task. Subjects were presented with highly fragmented images and control scrambled images. Fragmented images were calibrated to be ‘just’ recognizable as objects (i.e., perceptual closure was necessary), whereas the scrambled images were unrecognizable. Comparison of responses to these two stimulus classes revealed the neural processes underlying perceptual closure. fMRI revealed an object recognition system that mediates these closure processes, the core of which consists of the LOC regions. ERP recordings resulted in the wellcharacterized NCL component (for negativity associated with closure), a robust relative negativity over bilateral occipito-temporal scalp that occurs in the 230-400 ms timeframe. Our investigations further revealed an extended network of dorsal and frontal regions, also involved in perceptual closure processes. Inverse source analysis showed that the major generators of NCL localized to the identical regions within LOC revealed by the fMRI recordings and detailed the temporal dynamics across these LOC regions including interactions between LOC and these other nodes of the object-recognition circuit. Finally, direct intracranial recordings from human cortex in patients implanted for epilepsy mapping, provides validation of the localization data obtained from the source analyses of surface recordings. Mark Brady, North Dakota State University “Collecting Natural Images for Vision Science” In order to fully understand human vision, we need to understand how humans process natural images. Therefore, psychophysics with natural images is an essential part of vision science. Since natural images are more complex than artificial stimuli, we would also like to find ways to describe natural image structure. Natural image statistics is one such way. Natural images, as stimuli, and image statistics studies, depend on cameras. It has been widely assumed that any snapshot from any camera will do. This assumption ignores the fact that camera characteristics and settings can have a significant effect on the images and on image statistics. This talk will describe these camera effects and how to control them in an experimental setting. Daniel Kersten, University of Minnesota “Natural Images, Natural Percepts and Early Visual Processing” The traditional model of primary visual cortex (V1) is a retinotopically organized set of spatio-temporal filters. This model has been extraordinarily fruitful, providing explanations of a considerable body of psychophysical and neurophysiological results. It has also produced compelling linkages between natural image statistics, efficient coding theory, and neural responses. However, there is increasing evidence that V1 is doing a whole lot more. We can get insight into early cortical processing by studying both the relationship between image input and neural activity, and between human visual percepts and early cortical activity. I will describe functional magnetic resonance imaging (fMRI) studies which show that V1 activity is modulated by object properties, such as an object's degree of perceptual organization and by its perceived size. Stéphane Rainville, North Dakota State University “fMRI Evidence for an Intermediate Visual-Shape Population Code in Lateral Occipital Cortex” PURPOSE: Humans are exceptionally sensitive to small deviations from circularity. Here we used fMRI to test whether circles have a special status in the coding of shape. METHODS: BOLD signals were recorded from 6 participants in a 13 6-mm coronal-slice volume anchored on the occipital pole. A region-of-interest analysis isolated the lateral-occipital complex (LOC) by contrasting BOLD signals from images of intact vs. scrambled tools. In key experiments, observers viewed closed contours that varied in basic shape (i.e. radial frequency) and deviation from circularity (i.e. radial amplitude). Experiments followed a block design where deviation from circularity was varied across blocks, and basic shape was either varied within block (multi-shape blocks) or held fixed (single-shape blocks). Observers performed size judgments to maintain attention. RESULTS: BOLD response increased monotonically with deviation from circularity in both multiand singleshape blocks although responses to single-shape blocks had lower amplitudes. CONCLUSIONS: Data suggest that deviations from circle prototypes constitute the basis of increased neural activity. Release from adaptation implicit in higher responses to multi-shape blocks suggests that neural subpopulations selective for different shapes (i.e. radial-frequency contours) underlie shape coding in LOC.