Magnetic stimulation studies of visual cognition

The panoply of non-invasive techniques for brain imaging is responsible for much of the current excitement in cognitive neuroscience; sensory, perceptual and cognitive behaviour can now be correlated with cerebral blood flow as assessed by functional imaging, the electrical fields generated by populations of neurons or changes in magnetic fields created by electrical activity. Correlations between localized brain activity and behaviour, however, do not of themselves establish that any brain area is necessary for a particular task; necessity is the domain of the lesion technique. Transcranial magnetic stimulation (TMS) is a technique that can be used non-invasively to produce reversible functional disruption and has already been used to investigate visual detection, discrimination, attention and plasticity. The power of TMS as a `lesion' technique lies in the opportunity to combine reversible disruption with high degrees of spatial and temporal resolution. In this review we trace some of the major developments in the use of TMS as a technique for the investigation of visual cognition.     

Differentiation and unification in perception and cognition

It has been suggested that the development of distinctions between perception and cognition depends upon the perspective and the level of analysis chosen. Similarly, the unification of perception and cognition may be achieved from other perspectives and when other levels of analyses are applied. The fruitfulness, and disadvantages, of diverse suggestions for differentation/unification of perception and cognition are discussed briefly.     

An on-line laboratory in cognition and perception

The design of a computer-based laboratory system requires the coordination of pedagogical and technical goals. The development of our on-line laboratory in cognition and perception is described. The laboratory consists of 11 on-line experiments in which the student participates as both experimenter and subject. The software was designed for maximum transportability: Programs were written in a low-level BASIC, with thorough documentation; flexibility is provided both within and across experiments to suit local constraints; and the experiments are supported by a student manual, instructor’s manual, and implementation notes. Criteria for selecting experiments, implementation of the experiments, and preliminary evaluation of the laboratory are discussed.     

Interaction between affect and cognition in word perception

Investigated the hypothesis that the accuracy with which a briefly shown word is perceived depends on both the affective tone of the word and the activation of the corresponding memory code. To increase activation, expectation and word frequency were manipulated. Ss were exposed to a 25-ms flash of a target word. They then chose, from a word pair, the target word. In half the trials, this word pair was given before the flash to create an expectation. Consistent with the hypothesis, when the words were infrequent, accuracy in perception was lower for affective than for neutral words regardless of expectation. When the words were frequent, there was no effect of affective tone in the absence of expectation; in the presence of expectation, accuracy was higher for affective than for neutral words. The valence of the affective words had no effect. Results are interpreted in terms of attentional mechanisms implicated in conscious perception.     

On the distinction between perception and cognition

To uphold the distinction between perception and cognition for certain classes of tasks or phenomena, it is proposed that three criteria must be met: (1) when perceptual and cognitive functions serve different biological purposes, (2) when stimulus information in dynamic events is necessary, but not sufficient for veridical perception, and (3) when the task emphasizes explicit retrieval, as opposed to implicit use of information. Conversely, when the three criteria have not been met, conditions for theoretical unification exist.     

Introduction to Michotte's heritage in perception and cognition research

Several decades after Michotte's work was published, it continues to inspire current research in perception, cognition, and beyond. In this special issue we pay tribute to this heritage with a collection of empirical and theoretical papers on amodal completion and the perception of causality, two areas of research within which Michotte's work and ideas have had a lasting influence. As a background to better understand the remaining papers, we briefly sketch Michotte's life and work and the scope (in breadth and in depth) of his impact. We then review Michotte's seminal contributions to the areas covered in this special issue, some of the major research discoveries and themes in the intervening decades, and the major open questions and challenges we are still facing. We also include a sneak preview of the papers in this special issue, noting how they relate to Michotte's work and to each other. This review shows both how much influence Michotte has had on contemporary perception and cognition research, and how much important work remains to be done. We hope that the papers in this special issue will serve both to celebrate Michotte's heritage in this respect, and to inspire other investigators to continue the projects he began.     

The role of transcranial magnetic stimulation (TMS) in studies of vision, attention and cognition

Transcranial magnetic stimulation (TMS) can be conceptualized as a virtual lesion technique, capable of disrupting organized cortical activity, transiently and reversibly. The technique combines good spatial and temporal resolution and, moreover, because it represents an interference technique, can be said to have excellent functional resolution. The following is a review and discussion of the contribution which TMS has made to the study of vision, attention, development and plasticity and speech and language.     

Plasticity of brain and cognition in older adults

Aging is typically related to changes in brain and cognition, but the aging process is heterogeneous and differs between individuals. Recent research has started investigating the influence of cognitive and physical training on cognitive performance, functional brain activity, and brain structure in old age. The functional relevance of neural changes and the interactions among these changes following interventions is still a matter of debate. Here we selectively review research on structural and functional brain correlates of training-induced performance changes in healthy older adults and present exemplary longitudinal intervention studies sorted by the type of training applied (i.e., strategy-based training, process-specific training, and physical exercise). Although many training studies have been conducted recently, within each task domain, the number of studies that used comparable methods and techniques to assess behavioral and neural changes is limited. We suggest that future studies should include a multimodal approach to enhance the understanding of the relation between different levels of brain changes in aging and those changes that result from training. Investigating inter-individual differences in intervention-induced behavioral and neuronal changes would provide more information about who would benefit from a specific intervention and why. In addition, a more systematic examination of the time course of training-related structural and functional changes would improve the current level of knowledge about how learning is implemented in the brain and facilitate our understanding of contradictory results.     

Purposive behaviour in cognition and perception: Considerations of awareness in memory

The responses to the original article by Rönnberg (1990a) provoked interesting and thoughtful points of view that are covered by Gärling (1990), Hjelmquist (1990), Montgomery (1991), and Runeson (1990). These articles do not merely present a different outlook but also provide concepts that are certainly worthy of consideration and add more substance to the general topic under discussion. The purpose of this commentary is to seek an understanding of the ideas presented by the above authors within a synthesis of our views of current conceptualizations in cognition and perception. Each of the original criteria (Rönnberg, 1990a) will be treated in turn.     

Social cognition and the human brain

Humans are exceedingly social animals, but the neural underpinnings of social cognition and behavior are not well understood. Studies in humans and other primates have pointed to several structures that play a key role in guiding social behaviors: the amygdala, ventromedial frontal cortices, and right somatosensory-related cortex, among others. These structures appear to mediate between perceptual representations of socially relevant stimuli, such as the sight of conspecifics, and retrieval of knowledge (or elicitation of behaviors) that such stimuli can trigger. Current debates concern the extent to which social cognition draws upon processing specialized for social information, and the relative contributions made to social cognition by innate and acquired knowledge.     

Ordinal structure in the visual perception and cognition of smoothly curved surfaces

In theoretical analyses of visual form perception, it is often assumed that the 3-dimensional structures of smoothly curved surfaces are perceptually represented as point-by-point mappings of metric depth and/or orientation relative to the observer. This article describes an alternative theory in which it is argued that our visual knowledge of smoothly curved surfaces can also be defined in terms of local, nonmetric order relations. A fundamental prediction of this analysis is that relative depth judgments between any two surface regions should be dramatically influenced by monotonicity of depth change (or lack of it) along the intervening portions of the surface through which they are separated. This prediction is confirmed in a series of experiments using surfaces depicted with either shading or texture. Additional experiments are reported, moreover, that demonstrate that smooth occlusion contours are a primary source of information about the ordinal structure of a surface and that the depth extrema in between contours can be optically specified by differences in luminance at the points of occlusion.     

Prior stimulation and the perception of causality

An attempt was made to discover whether, in conditions similar to those of Michotte, the number of causal responses given by subjects was influenced by stimulation during the period just before the main experiment. Time-intervals between the arrival of object A and the departure of object B were systematically varied within the range 60 to 390 msec. Those who had earlier been exposed to shorter time-intervals (60 to 210 msec.) gave fewer causal responses than those who had been exposed to longer ones (150 to 300 msec. and 240 to 390 msec.). A possible explanation is offered in terms of the modification of existing “schemata.”     

Person perception informs understanding of cognition during visual search

Does person perception—the impressions we form from watching others—hold clues to the mental states of people engaged in cognitive tasks? We investigated this with a two-phase method: In Phase 1, participants searched on a computer screen (Experiment 1) or in an office (Experiment 2); in Phase 2, other participants rated the searchers’ video-recorded behavior. The results showed that blind raters are sensitive to individual differences in search proficiency and search strategy, as well as to environmental factors affecting search difficulty. Also, different behaviors were linked to search success in each setting: Eye movement frequency predicted successful search on a computer screen; head movement frequency predicted search success in an office. In both settings, an active search strategy and positive emotional expressions were linked to search success. These data indicate that person perception informs cognition beyond the scope of performance measures, offering the potential for new measurements of cognition that are both rich and unobtrusive.     

The Macintosh as a user-friendly laboratory for perception and cognition

We present a radically user-friendly Macintosh laboratory, MindLab, for instruction in perception and cognition. MindLab’s forte is its ability to display pictorial stimuli, including digitized photographs, transferred via the clipboard from Macintosh graphics applications. An experiment is programmed by specifying sequences of event primitives, represented by icons, to which stimuli, temporal parameters, and feedback options are assigned.     

The face and person perception: insights from social cognition

Social-cognitive investigations of face perception have tended to be motivated by different goals than cognitive and neuropsychological studies-namely, to understand the dynamics of social categorization rather than identity recognition-and the result has been a lack of cross-pollination of insights and ideas between the disciplines. We review the evidence from social cognition, with an eye to discussing how this work aligns with the Bruce and Young (1986) model of face recognition. Acknowledging the invaluable impact the model has exerted on our understanding of face recognition, we suggest that considering the bottom-up constraints of visual processing and the top-down influences of semantic knowledge will contribute to a more comprehensive understanding of face perception.