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Much indirect evidence supports the hypothesis that transformations of mental images are at least in part guided by motor processes, even in the case of images of abstract objects rather than of body parts. For example, rotation may be guided by processes that also prime one to see results of a specific motor action. We directly test the hypothesis by means of a dual-task paradigm in which subjects perform the Cooper-Shepard mental rotation task while executing an unseen motor rotation in a given direction and at a previously learned speed. Four results support the inference that mental rotation relies on motor processes. First, motor rotation that is compatible with mental rotation results in faster times and fewer errors in the imagery task than when the two rotations are incompatible. Second, the angle through which subjects rotate their mental images, and the angle through which they rotate a joystick handle are correlated, but only if the directions of the two rotations are compatible. Third, motor rotation modifies the classical inverted V-shaped mental rotation response time function, favoring the direction of the motor rotation; indeed, in some cases motor rotation even shifts the location of the minimum of this curve in the direction of the motor rotation. Fourth, the preceding effect is sensitive not only to the direction of the motor rotation, but also to the motor speed. A change in the speed of motor rotation can correspondingly slow down or speed up the mental rotation.

High-level visual processes make use of stored information, and are invoked during object identification, navigation, tracking, and visual mental imagery. The work presented in this document has resulted in a theory of the component "processing subsystems" used in high-level vision. This theory was developed by considering neuroanatomical, neurophysiological, and computational constraints. The theory has led to two kinds of empirical work. First, specific hypotheses about individual processing subsystems have been tested. For example, the analysis of the representation of spatial relations led to the prediction that the subsystems are used to encode this information, and a set of experiments was conducted that provided support for this distinction. This work has involved a combination of divided-visual-field experiments with normal subjects and detailed examinations of patients with focal brain damage. Second, the subsystems have been implemented in a large computer simulation model, which has been used to generate predictions about specific neurological syndromes. The model can be damaged in a variety of ways, and its performance on a set of tasks then observed. Predictions from the model have been tested, the results generally support its underlying assumptions and specific claims. In addition, individual subsystems have been implemented as "neural network" simulation models, which have been related directly to properties of the neural substrate assumed to underlie processing. The experiments conducted to date are summarized in the context of the theory in this report, and the utility of the theory for understanding the effects of brain damage is illustrated by reviewing a single case in detail. (Author)

Visual recognition, navigation, tracking, and imagery are posited to involve some of the same types of representations and processes. The first part of this paper develops a theory of some of the shared types of representations and processing modules. The theory is developed in light of neurophysiological and neuroanatomical data from non-human primates, computational constraints, and behavioral data from human subjects. In developing theories of some of the high-level computations that are performed by the visual system, three problems which must be solved by any visual system are considered: (1) position variability; (2) figure/ground segregation; and (3) non-rigid transformations. The second part of the paper develops a mechanism for the development of lateralization of visual function in the brain. The theory rests on a set of relatively simple, uncontroversial properties of the brain, including: (1) processing components; (2) exercise; (3) selectivity; (4) "central" bilateral control; and (5) reciprocal innervation. This theory leads to predictions about the lateralization of the putative processing modules. The third part of the paper examines critical tests of these predictions, and reviews relevant empirical findings in the literature. Eight pages of references and several figures are included. (Author/LMO)

This paper investigates the processes by which visual mental images--the precept-like short-term memory representations--are created from information stored in long-term memory. It also presents a new method for studying image generation. Three experiments were conducted using college students as subjects. In the first experiment, a Podgorny and Shephard paradigm was adapted to study image generation. In the second experiment, regression analyses were performed on response times in a scanning instruction and no-scanning instruction condition. Experiment three was designed to investigate whether scanning plays a functional role in image generation. Results indicated that images of upper case letters are formed segment by segment, in roughly the order in which most people draw the letters. Results were shown not to be an artifact of how people scan images once they are formed, and could not have been due to experimenter-expectancy effects. Results also indicated that subjective estimates of mental image generation time are quite close to those obtained using objective measures. (Author/LMO)