Behavioural and ERP indices of response inhibition during a Stop-signal task in children with two subtypes of Attention-Deficit Hyperactivity Disorder.

Previous research has shown that children with Attention-Deficit Hyperactivity Disorder of the Combined Type (AD/HDcom) have problems with response inhibition, with poorer task performance and atypical inhibition-related ERPs relative to control subjects, while little is known about response inhibition in children with Attention-deficit Hyperactivity Disorder of the Predominantly Inattentive Type (AD/HDin). In this study children with AD/HDin (N=12), AD/HDcom (N=13) and age-matched controls (N=13) aged between 8 and 14 years completed a Stop-signal task, with visual Go and auditory Stop-signal stimuli, while EEG was recorded. The results indicated that the groups did not differ on any inhibitory task performance measure, but the AD/HD groups showed more errors of omission to Go stimuli than controls. ERPs to the visual Go stimuli differed between children with AD/HDin and controls (increased central N1 and N2, decreased central P2 and increased parietal P3), while the AD/HDcom group showed only minor scalp distribution differences for N2 and P3. The AD/HDin group showed amplitude differences from controls to Stop signals (larger central N1 and parietal P3; reduced midline N2) and did not show a Successful vs. Failed inhibition effect for P3. The AD/HDcom group showed reduced parietal P3 to Stop signals, with the Trial Type effect present for N2 but not P3. These data suggest that the apparent atypical inhibitory processing at N2 and P3 may stem, at least in part, from atypical early sensory/alerting processing of all stimuli in children with AD/HDin.     

1.5-T surface-coil MRI of the knee

Five normal knees and 20 knees with suspected abnormalities involving the menisci or articular surfaces were examined with high-resolution surface-coil MRI. Surgical correlation was available in 15 cases. Signal-to-noise ratios were optimized using a field strength of 1.5 T and a round 7.6-cm surface coil. Spatial resolution was maximized by using fields of view reduced to as small as 8 cm. Separate examinations of the medial and lateral joint compartments were performed with the surface coil positioned vertically adjacent to the meniscus of interest. Ten meniscal tears were identified using sagittal and coronal images. T1-weighted images were adequate to detect most meniscal tears, and T2-weighted images were useful for providing an "arthrogram effect" in the presence of a joint effusion. Extrameniscal lesions that were examined included osteonecrosis of the femoral condyle, subchondral cysts, rheumatoid arthritis, degenerative arthritis, and anterior cruciate ligament tears. MRI was useful in determining the integrity of articular cartilage overlying defects in the subchondral bone and in detecting gross cartilage lesions in arthritis, but was less sensitive than arthroscopy in evaluating moderate changes in the hyaline cartilage.     

Errorless learning and the cognitive rehabilitation of memory-impaired schizophrenic patients

BACKGROUND: In recent years, evidence has accumulated that a significant proportion of schizophrenic patients have severe memory impairment, which cannot be attributed to the effects of medication, chronicity or institutionalization. Our group has demonstrated that memory impairment is associated with poor psychosocial outcome and treatment resistance. Work on the classical amnesic syndrome has suggested that memory training is facilitated by adopting an 'errorless learning' approach, where subjects do not experience failure during learning. This is based on the theory that the preserved implicit memory of amnesic patients results in implicitly remembered incorrect responses interfering with target items, in the absence of a functioning explicit memory system to allow differentiation. METHOD: We compared three groups of subjects, memory-impaired schizophrenic patients, memory unimpaired schizophrenic patients and healthy controls. RESULTS: An errorless learning approach conferred a significant advantage on the memory-impaired schizophrenic group, bringing their performance up to the level of both control groups. In contrast, adopting a traditional trial and error, or errorful approach resulted in markedly impaired performance in the memory-impaired schizophrenic group only. CONCLUSIONS: We conclude that errorless learning approaches may be worthy of further evaluation in the cognitive rehabilitation of memory-impaired schizophrenic patients.     

Peer review and performance improvement in a radiation oncology clinic

A program was implemented in the Radiation Oncology Division at Naval Medical Center San Diego to document baselines for process improvement and fairly assess physician supervisory performance for recredentialing. This program was based on criteria established by the American College of Radiology (ACR). In addition to weekly chart rounds with peer review of films and charts while patients are on treatment, a new mechanism of peer review post-therapy was instituted. All patients completing therapy have this peer review prior to final disposition of their charts. Data are now readily available for physician recredentialing. Further, several points of inconsistent chart documentation have been identified and remedied. This mechanism is a simple and efficient way to ensure continuing patient care within ACR standards.     

Volumetric magnetic resonance imaging study of the brain in subjects with sex chromosome aneuploidies

OBJECTIVES: Cognitive impairment has been reported in people with sex chromosome aneuploides (SCAs) and it has been proposed that the presence of an extra sex chromosome may have an adverse effect on neurodevelopment. This study examines the hypothesis with structural MRI of the brain. METHODS: Thirty two subjects with SCA (XXX (n=12), XYY (n=10), and XXY (n=10)) from a birth cohort study were matched groupwise for age, parental social class, and height with normal controls (13 female, 26 male). Brain MRI, measurements of IQ, and a structured psychiatric interview were performed. RESULTS: The XXX females and XXY males had significantly smaller whole brain volumes than controls of the same phenotypic sex (p=0.003 and p相似文献   

High frequency limitations on mach bands

The contrast required to see Mach bands in a trapezoidal grating has been measured under different conditions. At photopic levels, increasing contrast is required as grating frequency increases. Mach bands are absent at all frequencies in scotopic viewing. Their absence at lower frequencies is not due simply to lack of suprathreshold contrast since at low frequencies contrast sensitivity is little affected by dark adaptation.Trapezoids of diminishing ramp width require increasing contrast until for a square edge a contrast of just greater than 1 would be required. This is difficult to achieve in most subjects.The Chevreul illusion behaves quite differently being unaffected by dark adaptation and grating frequency.     

An explanation for the visibility of low frequency gratings

The cause of the low-frequency roll-off in the contrast sensitivity function of human vision was investigated. Evidence was found that low-frequency structure in the visual world is perceived not by harmonic analysis but by detection of contrast gradients.This hypothesis is supported by the thresholds of trapezoidal gratings, i.e. gratings which have regions of uniform luminance alternating with linear luminance ramps. Doubling the ramp slope halves the threshold at ramp widths of 0.5° and greater. Trapezoids with ramp widths less than 0.5° all have the same threshold which is equal to a square grating threshold.The visual world therefore is analyzed by two different mechanisms. Above the peak of the contrast sensitivity function harmonic analysis takes place and below it, contrast gradient analysis.     

A preliminary assessment of bladder distension in the treatment of enuretic children.

Urodynamic studies were performed in 22 enuretic children. Each child had previously been investigated to exclude gross psychological disturbance and organic disease and had been treated unsuccessfully in the past by conventional means. 16 of the 22 children showed evidence of bladder instability and were subjected to bladder distension. At follow-up, 4 children were in complete remission of symptoms, 6 had improved and 6 showed no change; the girls responded better than the boys. The interpretation of urodynamic studies, the significance of the results of bladder distension and the possible role of detrusor instability in the aetiology of enuresis are discussed.