The preparation and readiness for voluntary movement: a high-field event-related fMRI study of the Bereitschafts-BOLD response

Activity within motor areas of the cortex begins to increase 1 to 2 s prior to voluntary self-initiated movement (termed the Bereitschaftspotential or readiness potential). There has been much speculation and debate over the precise source of this early premovement activity as it is important for understanding the roles of higher order motor areas in the preparation and readiness for voluntary movement. In this study, we use high-field (3-T) event-related fMRI with high temporal sampling (partial brain volumes every 250 ms) to specifically examine hemodynamic response time courses during the preparation, readiness, and execution of purely self-initiated voluntary movement. Five right-handed healthy volunteers performed a rapid sequential finger-to-thumb movement performed at self-determined times (12-15 trials). Functional images for each trial were temporally aligned and the averaged time series for each subject was iteratively correlated with a canonical hemodynamic response function progressively shifted in time. This analysis method identified areas of activation without constraining hemodynamic response timing. All subjects showed activation within frontal mesial areas, including supplementary motor area (SMA) and cingulate motor areas, as well as activation in left primary sensorimotor areas. The time courses of hemodynamic responses showed a great deal of variability in shape and timing between subjects; however, four subjects clearly showed earlier relative hemodynamic responses within SMA/cingulate motor areas compared with left primary motor areas. These results provide further evidence that the SMA and cingulate motor areas are major contributors to early stage premovement activity and play an important role in the preparation and readiness for voluntary movement. (C) 2003 Elsevier Inc. All rights reserved.

Auditory lexical decisions in children with specific language impairment

This study examined spoken-word recognition in children with specific language impairment (SLI) and normally developing children matched separately for age and receptive language ability. Accuracy and reaction times on an auditory lexical decision task were compared. Children with SLI were less accurate than both control groups. Two subgroups of children with SLI, distinguished by performance accuracy only, were identified. One group performed within normal limits, while a second group was significantly less accurate. Children with SLI were not slower than the age-matched controls or language-matched controls. Further, the time taken to detect an auditory signal, make a decision, or initiate a verbal response did not account for the differences between the groups. The findings are interpreted as evidence for language-appropriate processing skills acting upon imprecise or underspecified stored representations.

Preventing recurrent events long term after coronary artery bypass graft: Suboptimal use of medications in a population study

Background There are few population-based data on long-term management of patients after coronary artery bypass graft (CABG), despite the high risk for future major vascular events among this group. We assessed the prevalence and correlates of pharmacotherapy for prevention of new cardiac events in a large population-based series. Methods A postal survey was conducted of 2500 randomly selected survivors from a state population of patients 6 to 20 years after first CABG. Results Response was 82% (n = 2061). Use of antiplatelet agents (80%) and statins (64%) declined as age increased. Other independent predictors of antiplatelet use included statin use (odds ratio [OR] 1.6, 95% CI 1.26-2.05) and recurrent angina (OR 1.6, CI 1.17-2.06). Current smokers were less likely to use aspirin (OR 0.59, CI 0.4-0.89). Statin use was associated with reported high cholesterol (OR 24.4, CI 8.4-32.4), management by a cardiologist (OR 2.3, CI 1.8-3.0), and the use of calcium channel-blockers. Patients reporting hypertension or heart failure, in addition to high cholesterol, were less likely to use statins. Angiotensin-converting enzyme inhibitors were the most commonly prescribed agents for management of hypertension (59%) and were more frequently used among patients with diabetes and those with symptoms of heart failure. Overall 42% of patients were on angiotensin-converting enzyme inhibitors and 36% on beta-blockers. Conclusions Gaps exist in the use of-recommended medications after CABG. Lower anti-platelet and statin use was associated with older age, freedom from angina, comorbid heart failure or hypertension, and not regularly visiting a cardiologist. Patients who continue to smoke might be less likely to adhere to prescribed medications.

Response to Drs Greve and Bianchini

We would like to thank Drs Greve and Bianchini for their interest in our paper and we agree that psychological factors involved in pain presentations can be complex. However, Drs Greve and Bianchini seem to have missed the point of our study. It was not the aim of this study to investigate psychological factors involved in whiplash injury. On the contrary, the aim of the study was to longitudinally investigate the development of sensory changes from the acute stage of whiplash injury until either recovery or the development of persistent symptoms. The GHQ-28 was used as a broad measure of psychological distress in an attempt to account for the effect of psychological distress on pain threshold measures. The authors may like to note that our later paper specifically investigated the development of psychological changes following whiplash injury

Credit assignment: The memory representation of dynamic task events

The experiment examined the influence of memory for prior instances on aircraft conflict detection. Participants saw pairs of similar aircraft repeatedly conflict with each other. Performance improvements suggest that participants credited the conflict status of familiar aircraft pairs to repeated static features such as speed, and dynamic features such as aircraft relative position. Participants missed conflicts when a conflict pair resembled a pair that had repeatedly passed safely. Participants either did not attend to, or interpret, the bearing of aircraft correctly as a result of false memory-based expectations. Implications for instance models and situational awareness in dynamic systems are discussed.

Response to Screening for abdominal aortic aneurysm - Screening reduces deaths related to aneurysm

Editor—We reported the study in a transparent fashion and were deliberately cautious in our conclusions. Australia and the United Kingdom are very different with regard to arrangements for primary care, which did not permit us to undertake a preliminary assessment of the eligibility of men for screening before we randomised them and issued half invitations to attend for the ultrasound examination.

"That is bloody revolting"! Inhibitory control of thoughts better left unsaid

An experiment explored the hypothesis that inhibitory ability helps people stop themselves from engaging in socially inappropriate behavior. All participants completed a Stroop color-naming task, after which half of the participants were asked to remember an eight-digit number (inducing divided attention). Participants were then offered an unfamiliar and visually unappetizing food product (a chicken foot) under conditions of either low or high social pressure to pretend that it was appealing. Participants who had full attention available and were under pressure to pretend the food was appealing were least likely to emit a negative response, and performance on the Stroop task predicted the degree to which they successfully restrained negative responses. These results suggest that the cognitive ability to inhibit unwanted information facilitates socially appropriate behavior.

The fMRI response of the LGN and V1 to cardinal red-green, blue-yellow, and achromatic visual stimuli

We compared the responsiveness of the LGN and the early retinotopic cortical areas to stimulation of the two cone-opponent systems (red - green and blue - yellow) and the achromatic system. This was done at two contrast levels to control for any effect of contrast. MR images were acquired on seven subjects with a 4T Bruker MedSpec scanner. The early visual cortical areas were localised by phase encoded retinotopic mapping with a volumetric analysis (Dumoulin et al, 2003 NeuroImage 18 576 - 587). We initially located the LGN in four subjects by using flickering stimuli in a separate scanning session, but subsequently identified it using the experimental stimuli. Experimental stimuli were sine-wave counterphasing rings (2 Hz, 0.5 cycle deg-1), cardinal for the selective activation of the L/M cone-opponent (RG), S cone-opponent (BY), and achromatic (Ach) systems. A region of interest analysis was performed. When presented at equivalent absolute contrasts (cone contrast = 5% - 6%), the BOLD response of the LGN is strongest to isoluminant red - green stimuli and weakest to blue - yellow stimuli, with the achromatic response falling in between. Area V1, on the other hand, responds best to both chromatic stimuli, with the achromatic response falling below. The key change from the LGN to V1 is a dramatic boost in the relative blue - yellow response, which occurred at both contrast levels used. This greatly enhanced cortical response to blue - yellow relative to the red - green and achromatic responses may be due to an increase in cell number and/or cell response between the LGN and V1. We speculate that the effect might reflect the operation of contrast constancy across colour mechanisms at the cortical level.