The nature and treatment of stuttering as revealed by fMRI A within- and between-group comparison

This article reviews some of our recent functional magnetic resonance imaging (fMRI) studies of stuttering. Using event-related fMRI experiments, we investigated brain activation during speech production. Results of three studies comparing persons who stutter (PWS) and persons who do not stutter (PWNS) are outlined. Their findings point to a region in the right frontal operculum (RFO) that was consistently implicated in stuttering. During overt reading and before fluency shaping therapy, PWS showed higher and more distributed neuronal activation than PWNS. Immediately after therapy differential activations were even more distributed and left sided. They extended to frontal, temporal, and parietal regions, anterior cingulate, insula, and putamen. These over-activations were slightly reduced and again more right sided two years after therapy. Left frontal deactivations remained stable over two years of observation, and therefore possibly indicate a dysfunction. After therapy, we noted higher activations in persons who stutter moderately than in those who stutter severely. These activations might reflect patterns of compensation. We discuss why these findings suggest that fluency-inducing techniques might synchronize a disturbed signal transmission between auditory, speech motor planning, and motor areas.

Educational objectives: The reader will learn about and be able to: (1) identify regions of brain activations and deactivations specific for PWS; (2) describe brain activation changes induced by fluency shaping therapy; and (3) discuss the correlation between stuttering severity and brain activation.     

Large-scale ensemble averaging of ambulatory impedance cardiograms

Impedance cardiography has been used increasingly to measure human physiological responses to emotional and mentally engaging stimuli. The validity of large-scale ensemble averaging of ambulatory impedance cardiograms was evaluated for preejection period (PEP), interbeat interval, and dZ/dt_(min) amplitude. We tested whether the average of “classical” 60-sec ensemble averages across periods with fixed activity, posture, physical load, social situation, and location could be accurately estimated from a single large-scale ensemble average spanning these entire periods. Impedance and electrocardiograms were recorded for about 24-h from 21 subjects. Recordings were scored by seven raters, using both methods for each subject. Good agreement (average intraclass correlation coefficient was .91) between both ensemble averaging methods was found for all three cardiac function measures. The results indicate that for unambiguous ambulatory impedance cardiograms, large-scale ensemble averaging is valid, which makes measuring prolonged changes in cardiac sympathetic activity by measuring ambulatory PEP feasible even in large epidemiological samples.     

Acquired ‘theory of mind'' impairments following stroke

The ability to attribute thoughts and feelings to self and others (‘theory of mind') has been hypothesised to have an innate neural basis and a dedicated cognitive mechanism. Evidence in favour of this proposal has come from autism; a brain-based developmental disorder which appears to be characterised by impaired theory of mind, despite sometimes good general reasoning skills/IQ. To date no case of specific acquired theory of mind impairment has been reported. The present study examined theory of mind in adults who had suffered right hemisphere stroke, a group known to show pragmatic and social difficulties. In one study using story materials and two using cartoons, patients' understanding of materials requiring attribution of mental states (e.g. ignorance, false belief) was significantly worse than their understanding of non-mental control materials. Data from healthy elderly subjects, and a small group of left hemisphere patients (who received the tasks in modified form), suggest that this impairment on mental state tasks is not a function of task difficulty. The findings support the notion of a dedicated cognitive system for theory of mind, and suggest a role for the healthy right hemisphere in the attribution of mental states.     

Marx and Exploitation

The discussion of the adequacy of Karl Marx's definition of exploitation has paid insufficient attention to a prior question: what is a definition? Once we understand Marx as offering a “reference-fixing definition in a model” we will realise that it is resistant to certain objections. A more general analysis of exploitation is offered here and it is suggested that Marx's own definition is a particular instance of the general analysis which makes a number of controversial moral assumptions.     

Differential effects of shared attention on perception of heading and 3-D object motion

When a person moves in a straight line through a stationary environment, the images of object surfaces move in a radial pattern away from a single point. This point, known as thefocus of expansion (FOE), corresponds to the person’s direction of motion. People judge their heading from image motion quite well in this situation. They perform most accurately when they can see the region around the FOE, which contains the most useful information for this task. Furthermore, a large moving object in the scene has no effect on observer heading judgments unless it obscures the FOE. Therefore, observers may obtain the most accurate heading judgments by focusing their attention on the region around the FOE. However, in many situations (e.g., driving), the observer must pay attention to other moving objects in the scene (e.g., cars and pedestrians) to avoid collisions. These objects may be located far from the FOE in the visual field. We tested whether people can accurately judge their heading and the three-dimensional (3-D) motion of objects while paying attention to one or the other task. The results show that differential allocation of attention affects people’s ability to judge 3-D object motion much more than it affects their ability to judge heading. This suggests that heading judgments are computed globally, whereas judgments about object motion may require more focused attention.     

The Effects of Leader and Subordinate Characteristics in the Development of Leader–Member Exchange Quality1

This study investigated the contribution of both subordinate and leader characteristics in the development of leader-member exchange (LMX) quality. Data from 56 subordinate-superior dyads working at a large West-coast media company revealed that subordinates high in work self-efficacy were liked more by their supervisors, perceived to be more similar to their supervisors, experienced more positive LMX quality, and were rated as better performers than subordinates low in self-efficacy. Previous job experience, was related only to one outcome; supervisor's liking of the subordinate. Subordinates initially low in self-efficacy benefited from high LMX, as evidenced by increased end-of-program self-efficacy. Perceptions of similarity between supervisor and subordinate were found to be more important to LMX quality than actual demographic similarity. Leader self-efficacy and optimism predicted subordinates' ratings of LMX quality only for female supervisors. Unexpectedly, leader self-efficacy and optimism were related to the leaders' own ratings of LMX and subordinate performance.     

“Girls Are as Good as Boys at Math” Implies That Boys Are Probably Better: A Study of Expressions of Gender Equality

Although “Girls are as good as boys at math” explicitly expresses equality, we predict it could nevertheless suggest that boys have more raw talent. In statements with this subject‐complement structure, the item in the complement position serves as the reference point and is thus considered more typical and prominent. This explains why “Tents are like houses,” for instance, sounds better than “Houses are like tents”—people generally think of houses as more typical. For domains about ability, the reference point should be the item that is typically more skilled. We further propose that the reference point should be naturally more skilled. In two experiments, we presented adults with summaries of actual scientific evidence for gender equality in math (Experiment 1) or verbal ability (Experiment 2), but we manipulated whether the reference point in the statements of equality in the summaries (e.g., “Boys’ verbal ability is as good as girls’”) was girls or boys. As predicted, adults attributed more natural ability to each gender when it was in the complement rather than subject position. Yet, in Experiment 3, we found that when explicitly asked, participants judged that such sentences were not biased in favor of either gender, indicating that subject‐complement statements must be transmitting this bias in a subtle way. Thus, statements such as “Girls are as good as boys at math” can actually backfire and perpetuate gender stereotypes about natural ability.     

Seeing What We Know, Knowing What We See: Challenging the Limits of Visual Acuity

Ageism has resulted in overstated expectations regarding the inevitable deterioration in human capabilities, such as visual perception, with age (Rowe and Kahn in Science, 237, 143?C149, 1987; Grant in Health and Social Work, 21, 9?C15, 1996). Human visual perception, however, is of a largely constructive nature, evidenced in the complementary interactions between top-down inputs (e.g., expectations) and bottom-up stimuli (Engel et al. in National Review of Neuroscience, 2(10), 704?C716, 2001; Miller and Cohen in, Annual Review of Neuroscience, 24, 167-202, 2001). Based on this constructive nature, we hypothesized that visual perception may be better than is typically expected. In three experiments, we demonstrated the malleability of visual acuity using a conditioning procedure involving manipulations in bottom-up stimuli. Experimental groups read a book excerpt with one letter in decreased font size, while the control groups read the same book excerpt with all letters in the same font size. Experiment 1 (N?=?112) examined whether visual acuity could be enhanced for a specific letter. Experiment 2 (N?=?70) assessed whether visual acuity could be enhanced for a non-conditioned letter, while Experiment 3 (N?=?108) evaluated whether the visual conditioning effects would transfer to all non-conditioned letters. Visual acuity for experimental groups was significantly better than that in the control groups, speaking to the general malleability of our visual sense.     

Bilingualism: consequences for mind and brain

Building on earlier evidence showing a beneficial effect of bilingualism on children's cognitive development, we review recent studies using both behavioral and neuroimaging methods to examine the effects of bilingualism on cognition in adulthood and explore possible mechanisms for these effects. This research shows that bilingualism has a somewhat muted effect in adulthood but a larger role in older age, protecting against cognitive decline, a concept known as 'cognitive reserve'. We discuss recent evidence that bilingualism is associated with a delay in the onset of symptoms of dementia. Cognitive reserve is a crucial research area in the context of an aging population; the possibility that bilingualism contributes to cognitive reserve is therefore of growing importance as populations become increasingly diverse.