Right, left or both? Brain hemispheres and apraxia of naturalistic actions

Neuropsychology allows us to see more clearly how brain processes are organized by looking at the way they fall apart. For example, a hundred years of research on brain-damaged individuals with deficits of higher-level motor abilities have shed light on the organization of normal motor abilities. A consistent finding has been the dominant role of the left hemisphere in motor control in right-handers. However, the recent paper of Hartmann et al. challenges this tradition by suggesting that both hemispheres can contribute to complex object and tool use.     

Rethinking the focusing effect in decision-making

According to Legrenzi et al. [Cognition 49 (1993) 37], in making a choice people consider only the alternatives explicitly represented in their mental model of the decision situation. Their idea has found empirical support in the "focusing effect": Individuals focus on the alternatives explicitly stated in the problem context, and do not take into account other possibilities. In their original study, Legrenzi and colleagues considered only one factor to account for the explicit representation of an alternative--i.e., its explicit verbal formulation in the decision problem. Recent theories of relevance and information gain can help articulate their original idea, suggesting that individuals explicitly represent relevant alternatives, whether or not they are explicitly formulated in the decision problem. In three experiments we first replicated Legrenzi et al.'s original experiment, and then showed that the explicit verbal mention of an alternative is neither sufficient nor necessary to focus on it. The results suggest that individuals are able to consider relevant alternatives, even when they are not made explicit in the verbal formulation of a decision problem.     

Selective deficit of motor imagery as tapped by a left-right decision of visually presented hands

This paper presents the case of MT, a patient suffering from apraxia with left-hemisphere damage who showed a selective deficit in mentally rotating images of hands whereas he was still able to mentally rotate other visual stimuli. The deficit was particularly evident when MT was asked to decide which hand (left or right) was represented in a picture. suggested that in order to carry out this task, participants would mentally rotate a representation of their own body part until it aligns with the stimulus and it does appear that MT's ability to mentally simulate movements is impaired. In contrast, he was able to mentally rotate other forms of bi- and three-dimensional stimuli. Our findings are also consistent with proposal that there are at least two ways in which objects can be mentally rotated, one that recruits processes devoted to motor preparation (e.g., hands), and another that does not.     

Visual effects in picture and word categorization

Two experiments are reported in which participants categorized stimuli as belonging or not belonging to the category of fruits. Blocks of pictures and words were used, with items referring to exemplars having either high or low intercategory visual similarity and/or semantic relatedness. For both pictures and words, response time was longer in the semantically related conditions than in the unrelated condition. Furthermore, there was a strong effect of visual similarity for pictures but not for words when semantic relatedness was held constant: Participants took longer to classify pictures of fruits when these were mixed with visually similar vegetables than when they were mixed with visually dissimilar vegetables. Reducing the stimulus visibility by adding a dot pattern had an additive effect for words but an interactive effect for pictures. The results are explained in terms of a unique locus for category decisions about pictures and words.     

Task-set inertia and memory-consolidation bottleneck in dual tasks

Three dual-task experiments examined the influence of processing a briefly presented visual object for deferred verbal report on performance in an unrelated auditory-manual reaction time (RT) task. RT was increased at short stimulus-onset asynchronies (SOAs) relative to long SOAs, showing that memory consolidation processes can produce a functional processing bottleneck in dual-task performance. In addition, the experiments manipulated the spatial compatibility of the orientation of the visual object and the side of the speeded manual response. This cross-task compatibility produced relative RT benefits only when the instruction for the visual task emphasized overlap at the level of response codes across the task sets (Experiment 1). However, once the effective task set was in place, it continued to produce cross-task compatibility effects even in single-task situations (“ignore” trials in Experiment 2) and when instructions for the visual task did not explicitly require spatial coding of object orientation (Experiment 3). Taken together, the data suggest a considerable degree of task-set inertia in dual-task performance, which is also reinforced by finding costs of switching task sequences (e.g., AC → BC vs. BC → BC) in Experiment 3.     

Framing the Ultimatum Game: Gender differences and autonomic responses

The present study aimed at investigating whether the way offers are framed in the Ultimatum Game (UG) affects behavioral and autonomic responses in men and women. The “I give you” and “I take” expressions were used as gain and loss frames, respectively. Skin conductance and heart rate were recorded as indices of autonomic activation in response to unfair, mid‐value, and fair offers. Acceptance rates were higher in men than in women under the gain frame. Moreover, men showed higher acceptance rates under the gain than under the loss frame with mid‐value offers, whereas women's choices were not affected by frame. On the physiological level, men produced differential autonomic response patterns during decision‐making when offers were presented under gain and loss framing. The “I take” frame, by acting as a loss frame, elicited in men the characteristic defensive response pattern that is evoked by aversive stimulation, in which increases in skin conductance are coupled with increases in heart rate. On the other hand, the “I give you” frame, by acting as a gain frame, elicited in men increases in skin conductance associated with prevailing heart rate deceleratory responses, reflecting a state of enhanced attention and orienting. In contrast, women's autonomic reactivity was not affected by frame, consistent with behavioral results. Phasic changes in heart rate were crucial in revealing differential functional significance of skin conductance responses under different frames in men, thus questioning the assumption that this autonomic measure can be used as an index of negative emotional arousal in the UG.     

We are what we eat: How food is represented in our mind/brain

Despite the essential role of food in our lives, we have little understanding of the way our knowledge about food is organized in the brain. At birth, human infants exhibit very few food preferences, and do not yet know much about what is edible and what is not. A multisensory learning development will eventually turn young infants into omnivore adults, for whom deciding what to eat becomes an effortful task. Recognizing food constitutes an essential step in this decisional process. In this paper we examine how concepts about food are represented in the human brain. More specifically, we first analyze how brain-damaged patients recognize natural and manufactured food, and then examine these patterns in the light of the sensory-functional hypothesis and the domain-specific hypothesis. Secondly, we discuss how concepts of food are represented depending on whether we embrace the embodied view or the disembodied view. We conclude that research on food recognition and on the organization of knowledge about food must also take into account some aspects specific to food category, the relevance of which has not been sufficiently recognized and investigated to date.     

Imitation of transitive and intransitive actions in healthy individuals

A handful of patients have been described as being impaired in performing transitive gestures, despite being still able to perform intransitive gestures. This impairment need not be explained by assuming different mechanisms; rather, it can be due to transitive actions being more difficult. In this study we tested whether neurologically healthy participants had greater difficulties in imitating transitive actions with respect to intransitive actions. Consistent with the prediction, subjects imitated intransitive better than transitive gestures. The ease of imitation of intransitive actions supports the complexity account of apraxic impairments.     

Cognitive neuroscience of actions: a whole is greater than the sum of its parts

The purpose of the present issue of Brain and Cognition is to demonstrate that the strength of neuroscience is in its multidisciplinary approach to understand events. Here we are concerned with the domain of action recognition and production. Seven articles have been selected as representative studies of actions carried out in different areas of neuroscience such as neuropsychology, neurophysiology, and cognitive science. Although each addresses different questions within the field, the articles share a common neuroscientific knowledge, as can be readily gathered from the references cited in each article.