Studying the neural bases of prism adaptation using fMRI: A technical and design challenge

Prism adaptation induces rapid recalibration of visuomotor coordination. The neural mechanisms of prism adaptation have come under scrutiny since the observations that the technique can alleviate hemispatial neglect following stroke, and can alter spatial cognition in healthy controls. Relative to non-imaging behavioral studies, fMRI investigations of prism adaptation face several challenges arising from the confined physical environment of the scanner and the supine position of the participants. Any researcher who wishes to administer prism adaptation in an fMRI environment must adjust their procedures enough to enable the experiment to be performed, but not so much that the behavioral task departs too much from true prism adaptation. Furthermore, the specific temporal dynamics of behavioral components of prism adaptation present additional challenges for measuring their neural correlates. We developed a system for measuring the key features of prism adaptation behavior within an fMRI environment. To validate our configuration, we present behavioral (pointing) and head movement data from 11 right-hemisphere lesioned patients and 17 older controls who underwent sham and real prism adaptation in an MRI scanner. Most participants could adapt to prismatic displacement with minimal head movements, and the procedure was well tolerated. We propose recommendations for fMRI studies of prism adaptation based on the design-specific constraints and our results.     

Perceiving verbal and vocal emotions in a second language

Emotional inferences from speech require the integration of verbal and vocal emotional expressions. We asked whether this integration is comparable when listeners are exposed to their native language and when they listen to a language learned later in life. To this end, we presented native and non-native listeners with positive, neutral and negative words that were spoken with a happy, neutral or sad tone of voice. In two separate tasks, participants judged word valence and ignored tone of voice or judged emotional tone of voice and ignored word valence. While native listeners outperformed non-native listeners in the word valence task, performance was comparable in the voice task. More importantly, both native and non-native listeners responded faster and more accurately when verbal and vocal emotional expressions were congruent as compared to when they were incongruent. Given that the size of the latter effect did not differ as a function of language proficiency, one can conclude that the integration of verbal and vocal emotional expressions occurs as readily in one's second language as it does in one's native language.     

A new object captures attention—but only when you know it’s new

Two hypotheses have been advanced to explain why an object appearing suddenly in an empty location captures attention. According to the first hypothesis, the visual transients that accompany an abrupt onset automatically trigger attentional orienting toward the object. The second hypothesis claims that the visual system regards the onset as an advent of a new object, and the latter’s novelty causes attention to be drawn toward it. To discriminate between these two accounts, Franconeri, Hollingworth, and Simons (2005) introduced a procedure in which an object was added to the display but, crucially, the object’s onset transients were concealed. Their results showed that this additional object failed to capture attention, which they interpreted as evidence against the new-object hypothesis. But the Franconeri et al. procedure could somehow have impeded the visual system from identifying the additional object as new. In three experiments, Franconeri et al.’s results were first replicated and extended. Further, it was shown that when the conditions facilitated the encoding of the locations of the old items, the new object did succeed in capturing attention.     

Adolescence, sexual conflict, and anorexia nervosa

Anorexia nervosa is a life-threatening mental disorder. As many as one out of every 250 girls between the ages of 12 and 18 may develop anorexia nervosa. The high incidence of the disorder among adolescent girls suggests that developmental sexual pressure inherent in adolescence may be associated with the onset of the disease. The symptoms of anorexia nervosa appear with the onset of puberty and the development of the secondary sex characteristics. Symptom formation is related to the following developmental issues: physiological changes (menstruation and breast development) and psychological changes (body image and sexual identity).     

Goal-Directed Aiming: Correcting a Force-Specification Error With the Right and Left Hands

In 2 experiments, the authors examined manual aiming asymmetries as well as the ability of participants to adjust their aiming trajectories following an unexpected change to the inertial resistance to movement. In Experiment 1, participants (N = 11) were able to rapidly adjust their movement trajectories to conform to the new movement requirements. They were faster and more consistent when aiming with their right hand than with their left hand, regardless of whether or not the movement was perturbed. In Experiment 2, participants' (N = 11) vision of the hand was manipulated so that the role of visual feedback in the corrective process could be examined. Vision had an impact not only on performance but also on the characteristics of the movement trajectories. Manual asymmetries in aiming were associated with a right hand superiority during the final corrective stages of the movement.     

Measuring online volitional response control with a continuous tracking task

We present a new tracking task designed to measure elements of response control in particular types of response adjustments such as stopping. In this task, participants track a visual target by manually pressing on a force sensor to yield a trace of force over time. Hardware specifications are detailed, as is an algorithm for determining the latencies of response adjustments such as stopping. We illustrate the use of the task in two experiments. Experiment 1 explores the reliability of data produced by the task. Experiment 2 examines some of the issues that can be addressed using the new task. These results demonstrate the usefulness and potential of the task for gauging response control within the context of the stopping literature.     

Capturing focused attention

When attention is diffuse, as in a visual search task, an abrupt onset almost invariably succeeds in capturing attention. But if attention had been cued in advance to a different location, the same onset may then fail to capture attention (Theeuwes, 1991; Yantis and Jonides, 1990). In previous demonstrations, the onset appeared frequently. This may have diminished the onset's novelty, which in turn could have affected its potency in capturing attention. The question we asked was whether preserving the onset's novelty could enhance its capacity in capturing attention, even when attention had been prioritized elsewhere. As in Theeuwes's (1991) study, observers were cued to the target location with a 100%-predictive central arrow cue. The frequency with which visual transients were introduced was varied across experiments. When the onset stimulus appeared frequently (Experiment 1), it indeed failed to capture attention. But when its appearance was relatively infrequent (Experiment 2), capture effects were clearly observed. In Experiment 3, the target appeared in one location throughout the experiment. This would have improved target localization, but an infrequently appearing onset stimulus still successfully captured attention.     

The processing of spatial frequency and orientation information

Three identification experiments were completed to disambiguate the associations between spatial frequency and orientation information at the sensory, decisional, and response levels. The stimuli were gratings generated by crossing four levels each of spatial frequency and orientation. In Experiment 1, the subjects made a single identification response to the stimuli. In Experiment 2, two identification responses were made, one for the spatial frequency component and the other for the orientation component. In Experiment 3, the subjects identified either the spatial frequency or the orientation component in any block of trials. The data were confusion matrices, and an information-transmission approach was used to investigate the interactions in the system. The results show that although there were sensory associations, there were no interactions at the decisional level. Performance parity was found: there was no significant difference between the single- and double-judgment paradigms in terms of information transmitted. Overall, the results suggest that although spatial frequency and orientation information is coded jointly at the sensory level, subsequent processing is independent, with each dimension drawing upon different attentional resources.     

A test of motor skill-specific action embodiment in ice-hockey players

To further our understanding of the role of the motor system in comprehending action-related sentences, we compared action experts (athletes) to visual experts (fans) and novices when responding with an action-specific effector (either hand or foot). These conditions allowed inferences about the degree and specificity of embodiment in language comprehension. Ice hockey players, fans and novices made speeded judgments regarding the congruence between an auditorily presented sentence and a subsequently presented picture. Picture stimuli consisted of either hockey or everyday items. Half of these pictures ‘matched’ the action implied in the preceding sentence. Further, the action in these images involved either primarily the hand or the foot. For everyday items, action-matched items were responded to faster than action-mismatched items. However, only the players and fans showed the action-match effect for hockey items. There were no consistent effector-stimuli compatibility effects, nor skill-based interactions with compatibility, suggesting that the action-match effect was not based on motor ability per se, but rather a construction of the action based on knowledge or visual experience with the hockey related sentences.