Chad J. Marsolek - US grants

The brain systems that underlie the ability to recognize different types of visual forms and the ability to recognize specific instances of the same type of form will be examined in the proposed research. An abstract- visual-form (AVF) system underlies recognition of different types of visual forms and operates more effectively in the left cerebral hemisphere (LH) than in the right cerebral hemisphere (RH). In contrast, a specific- visual-form (SVF) system underlies recognition of specific instances of a type of form and operates more effectively in the RH than in the LH. The proposed experiments will be conducted to further test whether these systems operate relatively independently in the brain. More importantly, the experiments are designed to test whether structural description characterizes the operations in an AVF system and whether template matching characterizes the operations in a SVF system. If so, the results from divided-visual-field studies of visual repetition priming should indicate that the parts of a visual form are stored and processed more effectively when the visual information is presented directly to the LH than to the RH, whereas the global structure of a visual form is stored and processed more effectively when the visual information is presented directed to the RH than to the LH.

Fundamental to visual object recognition is the ability to recognize abstract categories of objects (e.g., cups versus pens) as well as specific exemplars within those categories (e.g., individual pens). Interestingly, this ability poses a dilemma for the visual system: How can it recognize that two shapes should be considered the same (i.e., belong to the same abstract category) yet also different (i.e., correspond to different exemplars)? The aim of the proposed work is to investigate how the human brain may implement a solution to this problems. In particular, the goal is to uncover the architecture of functionally defined, neurally dissociable subsystems that underlie object recognition, and to determine whether this architecture reflects a solution to the abstract/specific dilemma. Understanding the structure of component subsystems has primary importance, as it must be addressed before satisfactory answers can be offered for contemporary questions in this field; different answers may apply to different subsystems. Preliminary studies indicate that dissociable subsystems learn to operate in parallel to accomplish abstract-category and specific-exemplar recognition of visual objects. However, it is difficult to produce fail-safe dissociations of functionally specified subsystems, and other architectures remain viable as alternative theories (e.g., dissociable subsystems operating in sequence, a single general-purpose mechanism, attention to different information within a single subsystem). Thus, the proposed research will further test and refine these theories, using a converging evidence attack to draw strong conclusions. The research will integrate analyses of the goals of the visual system with evidence of the neural implementation of dissociable subsystems to constrain such theories. Divided-visual-field studies will test whether abstract-category and specific-exemplar recognition subsystems operate in parallel (rather than in sequence) and with different relative efficiencies in the left and right cerebral hemispheres. They also will test the particular levels of categorization performed by abstract and specific subsystems, whether stimulus and task demands influence the relative contributions of these subsystems in predictable ways, as well as whether these subsystems utilize contradictory processing strategies (e.g., features-based versus whole-based processing). Overall, should evidence for dissociable parallel subsystems be observed, object recognition theories that attempt to account for performance through different architectures would have to be significantly revised. In any case, this research should lead to a greater understanding of the component subsystems underlying visual object recognition, with implications for addressing why neurological damage can produce selective visual recognition impairments and for suggesting useful architectures in computer vision systems.

DESCRIPTION (provided by applicant): The long-term objectives for this project are to develop and test a new method for examining the kind of emotional influences on memory that are exhibited in "flashbulb memories." Well-controlled laboratory experiments will test the hypothesis that emotional reactivity to visual scenes enhances episodic memory for the visual details in those scenes. This focused hypothesis helps to avoid some of the theoretical indeterminacy in previous discussions of such memories. Also, both emotional reactivity (to a standardized set of emotion-provoking scenes) and visual detail (e.g., particular left/right reflections of slides) are operationalized in concrete and physiologically motivated ways. In addition, the new method helps to overcome methodological concerns raised in previous naturalistic and laboratory research: Recognition memory procedures will provide experimental control and sensitive tests of memory accuracy, immediate tests will alleviate concerns about rehearsal of encoded information, and the use of many varied items will allow for strong and effective statistical tests. Preliminary experiments validate this method and indicate enhanced memory for details in high-emotional scenes but not in low-emotional scenes. Proposed experiments will examine important properties of this memory effect to address particular theoretical explanations. They will test whether detailed memory for emotion-provoking scenes (a) is observed only for negative scenes and not for the positive scenes, (b) depends on particular encoding or test tasks, (c) exhibits mood-congruent effects, (d) can be expressed in implicit memory, and (e) is influenced by retention interval. A clearer understanding of the properties of these flashbulb-like memory effects should help to suggest principles predicting the veridicality of emotional memories in eyewitness testimony situations. It also should help to provide new ways to conceptualize debilitating memories in post-traumatic stress disorder (and some phobias) and to suggest new treatments for such afflictions.