Test-retest reliability of fMRI during nonverbal semantic decisions in moderate-severe nonfluent aphasia patients

Cortical reorganization in poststroke aphasia is not well understood. Few studies have investigated neural mechanisms underlying language recovery in severe aphasia patients, who are typically viewed as having a poor prognosis for language recovery. Although test-retest reliability is routinely demonstrated during collection of language data in single-subject aphasia research, this is rarely examined in fMRI studies investigating the underlying neural mechanisms in aphasia recovery. The purpose of this study was to acquire fMRI test-retest data examining semantic decisions both within and between two aphasia patients. Functional MRI was utilized to image individuals with chronic, moderate-severe nonfluent aphasia during nonverbal, yes/no button-box semantic judgments of iconic sentences presented in the Computer-assisted Visual Communication (C-ViC) program. We investigated the critical issue of intra-subject reliability by exploring similarities and differences in regions of activation during participants' performance of identical tasks twice on the same day. Each participant demonstrated high intra-subject reliability, with response decrements typical of task familiarity. Differences between participants included greater left hemisphere perilesional activation in the individual with better response to C-ViC training. This study provides fMRI reliability in chronic nonfluent aphasia, and adds to evidence supporting differences in individual cortical reorganization in aphasia recovery.     

Anticipatory postural adjustments for altering direction during walking

The authors examined how individuals adapt their gait and regulate their body configuration before altering direction during walking. Eight young adults were asked to change direction during walking with different turning angles (0 degree, 45 degree, 90 degree), pivot foot (left, right), and walking speeds (normal and fast). The authors used video and force platform systems to determine participants' whole-body center of mass and the center of pressure during the step before they changed direction. The results showed that anticipatory postural adjustments occurred during the prior step and occurred earlier for the fast walking speed. Anticipatory postural adjustments were affected by all 3 variables (turn angle, pivot foot, and speed). Participants leaned backward and sideward on the prior step in anticipation of the turn. Those findings indicate that the motor system uses central control mechanisms to predict the required anticipatory adjustments and organizes the body configuration on the basis of the movement goal.     

Liking and memory for musical stimuli as a function of exposure

Three experiments examined changes in liking and memory for music as a function of number of previous exposures, the ecological validity of the music, and whether the exposure phase required focused or incidental listening. After incidental listening, liking ratings were higher for music heard more often in the exposure phase and this association was stronger as ecological validity increased. After focused listening, liking ratings followed an inverted U-shaped function of exposure for the most ecologically valid stimuli (initial increases followed by decreases), but this curvilinear function was attenuated or nonexistent for less valid stimuli. In general, recognition improved as a function of previous exposure for focused listeners, but the effect was attenuated or absent for incidental listeners.     

Perception of biological motion: A stimulus set of human point-light actions

We present a set of stimuli representing human actions under point-light conditions, as seen from different viewpoints. The set contains 22 fairly short, well-delineated, and visually “loopable” actions. For each action, we provide movie files from five different viewpoints as well as a text file with the three spatial coordinates of the point lights, allowing researchers to construct customized versions. The full set of stimuli may be downloaded fromwww.psychonomic.org/archive/.     

Modeling unipolar depression as a chaotic process

This study inspected the deterministic structure of unipolar depression. Two women self-monitored sadness hourly 10 times a day for 6 months. One woman had a recurrent history of unipolar depression, and the other did not. Data were analyzed by visual inspection, examination of the Fourier transforms of the time plots, and the correlation dimension. Results suggested that in addition to a strong periodic component that existed only within the depressed subject's mood time series, a low-dimensional chaotic process might have been operating. In the nondepressed control subject, no such periodicity or process could be identified. The findings support maladaptive deterministic theories of mood disorders and have implications for the assessment of unipolar depression.     

Impulse and Movement Space-Time Variability

In 3 experiments, the authors examined movement space-time variability as a function of the force-time properties of the initial impulse in a movement timing task. In the range of motion and movement time task conditions, peak force, initial rate of force, and force duration were manipulated either independently or in combination across a range of parameter values. The findings showed that (a) impulse variability is predicted well by the elaboration of the isometric force variability scaling functions of L. G. Carlton, K. H. Kim, Y. T. Liu, and K. M. Newell (1993) to movement, and (b) the movement spatial and temporal outcome variability are complementary and well predicted by an equation treating the variance of force and time in Newton's 2nd law as independent random variables. Collectively, the findings suggest that movement outcome variability is the product of a coherent space-time function that is driven by the nonlinear scaling of the force-time properties of the initial impulse.     

What’s in a name? Lexical knowledge drives infants’ visual preferences in the absence of referential input

Seventeen-month-old infants were presented with pairs of images, in silence or with the non-directive auditory stimulus ‘look!’. The images had been chosen so that one image depicted an item whose name was known to the infant, and the other image depicted an image whose name was not known to the infant. Infants looked longer at images for which they had names than at images for which they did not have names, despite the absence of any referential input. The experiment controlled for the familiarity of the objects depicted: in each trial, image pairs presented to infants had previously been judged by caregivers to be of roughly equal familiarity. From a theoretical perspective, the results indicate that objects with names are of intrinsic interest to the infant. The possible causal direction for this linkage is discussed and it is concluded that the results are consistent with Whorfian linguistic determinism, although other construals are possible. From a methodological perspective, the results have implications for the use of preferential looking as an index of early word comprehension.     

Architecture and organizational principles of Broca's region

Identifying cortical areas for language and speech processing is a prerequisite for cognitive neuroscience and clinical research. Although Broca's region is one of the essential nodes in the language network, its anatomical constituents are ill-defined and multiple definitions of Broca's region exist. Sanides' concept of microstructural gradations interpreted Broca's region as developing from neighboring motor, dorsolateral-prefrontal, and insular cortices. Recent mapping approaches based on cytoarchitecture, transmitter receptor distribution, and connectivity revealed a highly differentiated segregation of this region far beyond Brodmann's classical scheme. This novel segregational concept of structural and functional architecture more adequately reflects the various functions of Broca's region in cognitive and/or linguistic processes.     

Automated assembly of optimally spaced and balanced paired comparisons: Controlling order effects

To control order effects in questionnaires containing paired comparisons, Ross (1934) described an optimal ordering of the pairings. The pairs can also be balanced so that every stimulus appears equal numbers of times as the first and the second member of a pair. First, we describe and illustrate the optimally spaced, balanced ordering of pairings. Then we show how the optimally spaced, balanced order can be used to implement a matrix-sampling design or a fully incomplete design when the number of stimuli n is so large that respondents cannot reasonably be expected to judge all n(n - 1)/2 pairs. The algorithm for balancing and optimally spacing the list of pairs is described.