Is visual imagery really visual? Overlooked evidence from neuropsychology.

Abstract

Does visual imagery engage some of the same representations used in visual perception? The evidence collected by cognitive psychologists in support of this claim has been challenged by three types of alternative explanation: Tacit knowledge, according to which subjects use nonvisual representations to simulate the use of visual representations during imagery tasks, guided by their tacit knowledge of their visual systems; experimenter expectancy, according to which the data implicating shared representations for imagery and perception is an artifact of experimenter expectancies; and nonvisual spatial representation, according to which imagery representations are partially similar to visual representations in the way they code spatial relations but are not visual representations. This article reviews previously overlooked neuropsychological evidence on the relation between imagery and perception, and discusses its relative immunity to the foregoing alternative explanations. This evidence includes electrophysiological and cerebral blood flow studies localizing brain activity during imagery to cortical visual areas, and parallels between the selective effects of brain damage on visual perception and imagery. Because these findings cannot be accounted for in the same way as traditional cognitive data using the alternative explanations listed earlier, they can play a decisive role in answering the title question.The question of whether visual imagery is really visual, that is, whether it involves some of the same representations of stimuli normally engaged by the perception of those stimuli, has been the subject of a long-standing debate in cognitive psychology. This article reviews a set of empirical findings from neuropsychology that are directly relevant to this debate. I will argue that this generally overlooked source of data can play an important role in determining the relation between imagery and perception, because it is immune to many of the criticisms and alternative explanations that have plagued the cognitive psychology approach to this topic.One side of the debate maintains that imaging consists of the top-down activation of perceptual representations, that is, representations that are also activated automatically by an external stimulus during perception.

EEG dynamics reflects the partial and holistic effects in mental imagery generation

“…Previous studies have investigated different kinds of mental imagery, such as general, specific, contextual, and episodic autobiographical (de Beni and Pazzaglia, 1995;Cornoldi and Rossana, 1998), but the relationship between partial and holistic mental imagery generations is still poorly understood. Some visual perception studies, which share the common problem of modality-specific mechanisms and similar information processing with imagery, have shown that a subject evaluates holistic properties more easily than partial properties (Shepard and Cooper, 1982;Farah, 1988;Kosslyn, 1994). Additional experiments have been designed to investigate both visual perception and mental imagery, and have proved that the identification of holistic information is more important than that of partial information during Journal of Zhejiang University-SCIENCE B (Biomedicine & Biotechnology) ISSN 1673-1581 (Print); ISSN 1862-1783 (Online) www.zju.edu.cn/jzus; www.springerlink.com E-mail: jzus@zju.edu.cn mental imagery generation (Ganis et al, 2004;Låg et al, 2006;Thomas and Forde, 2006).…”

Self-knowledge of an amnesic patient: Toward a neuropsychology of personality and social psychology.

“…For example, studies of patients suffering amnesia as a result of head injury reveal a dissociation between episodic and semantic memory that suggests the existence of two distinct systems (e.g., Grossi, Trojano, Grasso, & Orsini, 1988;Tulving, 1989Tulving, , 1991; similarly, studies of imagery in brain-damaged individuals has suggested that visual imagery and spatial imagery are mediated by different systems and are thus not identical (e.g., Farah, 1988;Jankowiak, Kinsbourne, Shalev, & Bachman, 1992;Vargha-Khadem, Issacs, & Mishkin, 1994).…”

Temporal integration between visual images and visual percepts.

“…Whether, in the end, percepts and images are analog or propositional in form is irrelevant to our experiments (see Pylyshyn, 1973Pylyshyn, , 1978Pylyshyn, , 1981; for reviews and commentary on this debate, see also Finke, 1980Finke, , 1985Kosslyn, 1997). 2 For complete reviews, see Farah (1984Farah ( , 1988, Kosslyn (1987), and Tippett (1992).…”