Cognitive brain potentials in children at risk for schizophrenia: preliminary findings

Event-related brain potentials were recorded to auditory stimuli from children at risk for schizophrenia and normal control children who were part of two independent samples being followed longitudinally. Subjects were required to detect (with a reaction time response) one of two infrequent events (either a pitch change or a missing stimulus), each of which occurred 17 percent of the time, and was embedded in a sequence of frequent events occurring 66 percent of the time. The event-related potential (ERP) elicited by both infrequent stimuli consisted of a positive-going wave peaking at 350 msec for the pitch change ERP (P350) and 400 msec for the missing stimulus ERP (P400) and a slow wave, which overlapped with and extended beyond the P350 and P400 potentials. When the eliciting event was relevant, these potentials were significantly larger than when it was irrelevant. When the waveforms by the highrisk (HR) subjects were compared to those produced by the normal control (NC) subjects, the HR subjects of both samples showed significantly less late positive amplitude (P350 and P400) than the NC subjects, but only when the eliciting event was relevant. This effect appeared to be independent of reaction time, as reaction time means and variances were quite similar between risk groups. Other possible explanations for this amplitude reduction were explored. Since late positive component amplitude reduction has been consistently reported to characterize the waveforms of adult schizophrenics, the reduction seen in children at genetic risk for schizophrenia may be a premorbid indicator for the development of the psychosis.

An investigation of hybrid III and living human drop tests

The effect of roof crush on restrained occupants has often been discussed without regard to the headroom available, effectiveness of belts, and location of roof crush. In this article, the question of the ability to protect a simply restrained occupant in an environment in which the roof does not crush is addressed. The subjects were inverted and dropped vertically in noncrushable production vehicle compartments and a specially designed drop fixture. Data collected includes head accelerations, vehicle accelerations, head displacements, belt angles, anchor point location, seat position, and belt tension for a variety of occupant sizes. To our knowledge, these are the first inverted living human vertical studies to be scientifically documented and reported. It was found that no head or neck injuries resulted from drops of up to 91 cm and velocities up to 4.2 m/sec for restrained occupants in the absence of roof crush.

An event-related potential evaluation of involuntary attentional shifts in young and older adults

Involuntary shifts in attention to irrelevant stimuli were studied in elderly and young volunteers during a dichotic-listening task. Event-related potentials and behavioral measures were recorded. Volunteers heard pairs of tones presented with 2 different stimulus onset asynchronies (SOAs). To-be-ignored tones were presented to the left ear, followed by to-be-attended tones to the right ear. Left-ear tones were a frequent standard (700 Hz) and an infrequent small (650 Hz) and large (500 Hz) deviant. Right-ear tones (1500 Hz) were presented with 2 equiprobable intensities. Volunteers responded to the lower intensity stimulus. Behavioral performance was impaired at the short SOA when to-be-ignored large deviants preceded to-be-attended targets, but more so for the elderly volunteers. Large deviants also elicited the mismatch negativity (MMN) and P3a for both age groups. It was concluded that the more impaired behavioral performance observed for the elderly was due to greater sensitivity to output from the MMN system by a frontal lobe system responsible for the maintenance of attentional focus.

The effect of perceptual grouping on the mismatch negativity

The mismatch negativity (MMN) was used as a probe to evaluate changes, with age, of transient auditory memory. Subjects were 16 young (M = 23 years) and 16 old (M = 72 years) people. Standard auditory stimuli were presented in trains of eight tones (1000 Hz) with either a I-s or 8-s intertrain interval (ITI). Occasionally, the first stimulus of a train was replaced with a 1200 Hz tone (deviant). The MMN was recorded while subjects watched a silent movie and ignored the sounds. Both groups of subjects showed an MMN response to deviant stimuli under the 1-s ITI condition, but MMNs were only seen for some subjects under the 8-s ITI condition. After MMN recording, subjects performed a discrimination task to the tones used for recording MMNs. Accuracy for both groups was near 100% at both ITIs. These results suggest that generation of MMN is a function of the perceptual grouping of the acoustical stimuli and that the integrity of perceptual grouping may be maintained with increased age.

Patterns of psychopathology and dysfunction in high-risk children of parents with panic disorder and major depression

OBJECTIVE

The purpose of the study was to evaluate 1) whether an underlying familial predisposition is shared by all anxiety disorders or whether specific risks are associated with specific disorders, and 2) whether panic disorder and major depression have a familial link.

METHOD

The study compared four groups of children: 1) offspring of parents with panic disorder and comorbid major depression (N=179), 2) offspring of parents with panic disorder without comorbid major depression (N=29), 3) offspring of parents with major depression without comorbid panic disorder (N=59), and 4) offspring of parents with neither panic disorder nor major depression (N=113).

RESULTS

Parental panic disorder, regardless of comorbidity with major depression, was associated with an increased risk for panic disorder and agoraphobia in offspring. Parental major depression, regardless of comorbidity with panic disorder, was associated with increased risks for social phobia, major depression, disruptive behavior disorders, and poorer social functioning in offspring. Both parental panic disorder and parental major depression, individually or comorbidly, were associated with increased risk for separation anxiety disorder and multiple (two or more) anxiety disorders in offspring.

CONCLUSIONS

These findings confirm and extend previous results documenting significant associations between the presence of panic disorder and major depression in parents and patterns of psychopathology and dysfunction in their offspring.

A controlled study of behavioral inhibition in children of parents with panic disorder and depression

OBJECTIVE

"Behavioral inhibition to the unfamiliar" has been proposed as a precursor to anxiety disorders. Children with behavioral inhibition are cautious, quiet, introverted, and shy in unfamiliar situations. Several lines of evidence suggest that behavioral inhibition is an index of anxiety proneness. The authors sought to replicate prior findings and examine the specificity of the association between behavioral inhibition and anxiety.

METHOD

Laboratory-based behavioral observations were used to assess behavioral inhibition in 129 young children of parents with panic disorder and major depression, 22 children of parents with panic disorder without major depression, 49 children of parents with major depression without panic disorder, and 84 children of parents without anxiety disorders or major depression (comparison group). A standard definition of behavioral inhibition based on previous research ("dichotomous behavioral inhibition") was compared with two other definitions.

RESULTS

Dichotomous behavioral inhibition was most frequent among the children of parents with panic disorder plus major depression (29% versus 12% in comparison subjects). For all definitions, the univariate effects of parental major depression were significant (conferring a twofold risk for behavioral inhibition), and for most definitions the effects of parental panic disorder conferred a twofold risk as well.

CONCLUSIONS

These results suggest that the comorbidity of panic disorder and major depression accounts for much of the observed familial link between parental panic disorder and childhood behavioral inhibition. Further work is needed to elucidate the role of parental major depression in conferring risk for behavioral inhibition in children.

24-hour history is more closely associated with vitamin A status and provides a better estimate of dietary vitamin A intake of deficient Indonesian preschool children than a food frequency method

OBJECTIVES

To determine if the Simplified Dietary Assessment to Identify Groups at Risk of Inadequate Intake of Vitamin A developed by the International Vitamin A Consultative Group (IVACG) correctly classified a group of vitamin A-deficient children as being at risk, and to see if a food frequency questionnaire (FFQ) or 24-hour history (24HH) yielded estimated dietary vitamin A intakes most closely associated with vitamin A status.

DESIGN

Forty-seven foods were identified as contributing most of the vitamin A to the diet of the study population. For each food, usual portion sizes were determined during a pilot study. Intake was calculated from data collected by FFQ and 24HH. Four modifications of the 24HH analysis were made to determine if this method of analysis could be simplified.

SUBJECTS/SETTING

Subjects were 265 Indonesian children with or at high risk of developing xerophthalmia.

RESULTS

Mean and median intakes of vitamin A based on the 24HH analysis were 50% and 27% of the US Recommended Dietary Allowance, respectively, which accurately identified the study sample as being at risk. Dietary intake based on the 24HH was significantly associated with serum retinol concentration (P = .01, trend test). Eliciting portion sizes during the 24HH was not necessary once the usual portion sizes consumed by the population were estimated in the pilot study. Mean and median intakes of vitamin A based on the FFQ were 150% and 118% of the Recommended Dietary Allowance, respectively, which suggests that the FFQ overestimated intake. Intake based on the FFQ was not correlated with serum retinol concentration.

CONCLUSIONS

Our findings do not support the IVACG recommendation that the FFQ be regarded as more reliable than the 24HH when the 2 methods produce different conclusions, nor the recommendation of some users of the method that the 24HH be dropped from the assessment method.

Evaluating the effectiveness of a vision rehabilitation intervention using an objective and subjective measure of functional performance

PURPOSE

To test the hypothesis that vision rehabilitation using optometry, occupational therapy and social work services increases patients' functional ability and to assess whether involving families in the intervention results in more successful outcomes.

METHODS

We conducted an outcome study of 97 patients new to the Vision Rehabilitation Service. Subjects were between the ages of 19 and 91 years, with a median age of 76. Their visual acuities were 20/100 or worse in the better eye, with 50% of the subjects having acuities worse than 20/200. Macular degeneration was the most prevalent diagnosis. Subjects were assigned to either an individually focused (n=48) or a family focused (n=49) intervention. The outcome measure was change in function, as assessed by speed and accuracy of performance (objective measure) and by the patients' self-reports of difficulty and dependency in performing daily activities (subjective measures). Data were collected before and after the intervention.

RESULTS

Most patients had documented improvement after rehabilitation on both objective (p=.0001) and subjective (decreased dependency, p=.01) measures of function. The sample size did not provide adequate statistical power to show differences between family focused and individually focused interventions.

CONCLUSIONS

This study documents significant improvement after vision rehabilitation for a predominantly elderly population. Patients in both family and individually focused interventions improved comparably.

Whole-body FDG positron emission tomographic imaging for staging esophageal cancer comparison with computed tomography

PURPOSE

The aim of the authors in this study was to critically evaluate the role of whole-body positron emission tomographic (PET) imaging with fluorine-18 fluorodeoxyglucose (FDG) in staging esophageal cancer, and further to compare this method with conventional imaging with computed tomography (CT).

MATERIALS AND METHODS

The authors performed independent, blinded retrospective evaluations of FDG PET images obtained in 47 patients referred for the initial staging of esophageal cancer before minimally invasive surgical staging. Twenty PET studies from patients with nonesophageal thoracic cancers were randomly selected for inclusion in the PET readings. In a subset of 37 of 47 cases, the PET findings were compared with independent readings of CT studies acquired within the same 6-week interval. The utility of the imaging findings was evaluated using a high-sensitivity interpretation (i.e., assigning equivocal findings as positive) and a low-sensitivity interpretation (i.e., assigning equivocal findings as negative).

RESULTS

PET was less sensitive (41% in high-sensitivity mode, 35% in low-sensitivity mode) than CT (63% to 87%) for diagnosing tumor involvement in locoregional lymph nodes, which was identified by surgical assessment in 72% of patients. Notable, however, was the greater specificity of PET-determined nodal sites (to approximately 90%) compared with CT (14% to 43%). In detecting histologically proved distant metastases (n = 10), PET performed considerably better when applied in the high-sensitivity mode, with a sensitivity rate of approximately 70% and a specificity rate of more than 90% in the total group and in the subset of patients with correlative CT data. In the low-sensitivity mode, CT identified only two of seven metastatic sites, whereas the high-sensitivity mode resulted in an unacceptably high rate of false-positive readings (positive predictive value, 29%). PET correctly identified one additional site of metastasis that was not detected by CT.

CONCLUSIONS

The relatively low sensitivity of PET for identifying locoregional lesions precludes its replacement of conventional CT staging. However, the primary advantage of PET imaging is its superior specificity for tumor detection and improved diagnostic value for distant metastatic sites, features that may substantially affect patient management decisions. In conclusion, PET imaging is useful in the initial staging of esophageal cancer and provides additional and complementary information to that obtained by CT imaging.

Learning-induced LTP in neocortex

The hypothesis that learning occurs through long-term potentiation (LTP)- and long-term depression (LTD)-like mechanisms is widely held but unproven. This hypothesis makes three assumptions: Synapses are modifiable, they modify with learning, and they strengthen through an LTP-like mechanism. We previously established the ability for synaptic modification and a synaptic strengthening with motor skill learning in horizontal connections of the rat motor cortex (MI). Here we investigated whether learning strengthened these connections through LTP. We demonstrated that synapses in the trained MI were near the ceiling of their modification range, compared with the untrained MI, but the range of synaptic modification was not affected by learning. In the trained MI, LTP was markedly reduced and LTD was enhanced. These results are consistent with the use of LTP to strengthen synapses during learning.

Event-related potential (ERP) studies of memory encoding and retrieval: a selective review

As event-related brain potential (ERP) researchers have increased the number of recording sites, they have gained further insights into the electrical activity in the neural networks underlying explicit memory. A review of the results of such ERP mapping studies suggests that there is good correspondence between ERP results and those from brain imaging studies that map hemodynamic changes. This concordance is important because the combination of the high temporal resolution of ERPs with the high spatial resolution of hemodynamic imaging methods will provide a greatly increased understanding of the spatio-temporal dynamics of the brain networks that encode and retrieve explicit memories.

Event-related brain potential investigations of memory and aging

A review of the literature that examines event-related brain potentials (ERPs) and memory with respect to aging reveals some consistency in the processes that might be spared and those that might be compromised with increasing age. By and large, the ERP repetition effect, recorded during indirect memory paradigms, appears to be relatively intact with aging, suggesting spared repetition priming mechanisms and the brain substrates upon which they depend. Some age-related findings during direct (i.e. explicit) memory testing suggest that a left-sided posterior old/new effect ( approximately 500-800 ms), thought to reflect a relatively automatic retrieval of item information, is equivalent in young and old. A later, long-duration, right-sided, prefrontal old/new effect, allied with the search for and/or the retrieval of contextual information (i.e. source memory), has been found to be smaller or absent in the waveforms of the old in two of three studies, suggesting impaired source memory mechanisms in the elderly. It is argued that the data are relatively consistent with spared item retrieval mechanisms in the elderly presumably supported by medial temporal lobe structures. However, although the data are suggestive, there are too few studies at this time to reach a firm conclusion as to whether the mechanisms that support contextual retrieval, presumably mediated by prefrontal cortical structures, are impaired in the elderly.

Functional role of NMDA autoreceptors in olfactory mitral cells

The output of the olfactory bulb is governed by the interaction of synaptic potentials with the intrinsic conductances of mitral cells. While mitral cells often are considered as simple relay neurons, conveying activity in olfactory receptor cells to the piriform cortex, there is strong physiological and behavioral evidence that local synaptic interactions within the olfactory bulb modulate mitral cell discharges and facilitate odorant discrimination. Understanding the circuitry of the olfactory bulb is complicated by the fact that most dendrites in this region are both pre- and postsynaptic. Feedback inhibition is mediated through reciprocal dendrodendritic synapses between the secondary dendrites of mitral cells and GABAergic granule cells. Here we show that glutamate released from mitral cell dendrites also activates local N-methyl-D-aspartate (NMDA) autoreceptors, generating an inward tail current following depolarizing voltage steps. Autoreceptor-mediated self-excitation is calcium dependent, can be evoked by single action potentials in the presence of magnesium, and is graded with the number of spikes in a train. We find that dendrodendritic inhibition also is evoked by single action potentials but saturates rapidly during repetitive discharges. Self-excitation also underlies the prolonged afterdischarges apparent in mitral cells following potassium channel blockade. Both afterdischarges and autoreceptor-mediated tail currents persist in TTX, suggesting that they are produced by local rather than polysynaptic actions of glutamate. Blockade of NMDA autoreceptors with 2-amino-5-phosphonovaleric acid (APV) reduces the firing frequency within action potential cluster. The rapid kinetics of self-excitation suggests a functional role of NMDA autoreceptors in prolonging periods of phasic firing in mitral cells.

Calcium influx through NMDA receptors directly evokes GABA release in olfactory bulb granule cells

Recurrent inhibition in olfactory bulb mitral cells is mediated via reciprocal dendrodendritic synapses with granule cells. Although GABAergic granule cells express both NMDA and non-NMDA glutamate receptors, dendrodendritic inhibition (DDI) relies on the activation of NMDA receptors. Using whole-cell recordings from rat olfactory bulb slices, we now show that olfactory NMDA receptors have a dual role; they depolarize granule cell spines, and they provide a source of calcium that can evoke GABA exocytosis. We demonstrate that exogenous NMDA can trigger GABA release after blockade of voltage-dependent calcium channels (VDCCs) with Cd. We also find that postsynaptic depolarization alone can evoke GABA release via a separate mechanism that relies on calcium influx through Cd-sensitive VDCCs. By selectively manipulating postsynaptic responses in granule cells with high-K or low-Na extracellular solutions, we show that endogenous glutamate can elicit GABA release via both NMDA receptor- and VDCC-dependent pathways. Finally, we find that blockade of Na channels in granule cells with tetrodotoxin enhances DDI, presumably by reducing the depolarization of granule cells during DDI and thereby increasing the driving force for Ca entry through NMDA receptors. These results provide evidence of a novel mechanism for evoked transmitter release that depends on Ca influx through ionotropic receptors and provides a new potential site for synaptic plasticity in the olfactory bulb.

An event-related potential study of encoding in young and older adults

Event-related brain potentials (ERPs) were recorded from young (M age=25) and older (M age=71) adults during the study phase of a recognition memory paradigm. Participants studied two temporally distinct lists of sentences (each containing two unassociated nouns). During recognition testing, in response to the nouns, participants made old/new, followed by remember (context)/know (familiarity) and temporal source (i.e., list) judgments. To assess age-related differences in encoding, the ERPs recorded during study were averaged as a function of the correctness of the judgment of old in conjunction with subsequent temporal (list correct/incorrect) and subsequent remember and know judgments, i.e., subsequent memory or Dm effects were computed. Both young and old showed robust Dm activity regardless of whether the subsequent temporal source judgment was correct or incorrect. Although both young and old produced robust Dm effects for study items subsequently associated with a remember judgment, only the older participants showed a reliable Dm effect associated with study trials that were subsequently associated with a know judgment. This pattern of results suggests that older adults did not differentially encode items that would be subsequently retrieved with context from those that would be retrieved without such attributes.

Validity of DSM-IV subtypes of attention-deficit/hyperactivity disorder: a family study perspective

OBJECTIVE

To test the hypothesis that the clinical severity of subtypes paralleled a gradient of familial severity.

METHOD

One hundred forty children with attention-deficit/hyperactivity disorder (ADHD) and 120 normal control children and their biological relatives were studied: Because these data had been collected prior to the publication of DSM-IV, DSM-III-R symptoms were used to approximate DSM-IV subtypes using a method the authors had validated in prior work.

RESULTS

The first prediction from the hypothesis was true: rates of ADHD among relatives of each subtype group were greater than rates among relatives of controls. But the second prediction did not hold: rates of ADHD were not significantly higher among relatives of combined-typed probands compared with relatives of other probands. The "gradient model" also predicted that subtypes would not "breed true" (i.e., the subtype of the relative would not be the same as that of the proband). The prediction of nonspecificity was refuted for the inattentive and combined subtypes, but hyperactive-impulsive ADHD was found almost exclusively among relatives of hyperactive-impulsive probands.

CONCLUSIONS

Although the results are limited by some small subsamples along with the use of a DSM-III-R-ascertained sample, they provide little evidence for the idea that DSM-IV subtypes of ADHD correspond to familially distinct conditions. They also do not confirm the idea that the subtypes fall along a gradient of familial severity. Instead, they suggest that symptom differences among subtypes are due to nonfamilial, environmental causes.

A developmental trajectory in implicit memory is revealed by picture fragment completion

Dissociations between performance on implicit and explicit tasks have often been taken as evidence that different neural structures subserve the two types of memory. One such dissociation involves developmental differences that emerge in explicit tasks, but which appear to be absent in implicit tasks. Such findings are consistent with the idea that implicit memory is subserved by a more primitive system that evolves earlier at both phylogenetic and ontogenetic levels. The present paper reviews previous studies that claimed to find evidence that implicit memory is fully developed in very young children. Issues of measurement error, ceiling effects, and insufficient power brought up questions about those studies with respect to the developmental issue. The present study compares performance on implicit (picture fragment completion) and explicit (free recall and recognition) memory tasks with groups ranging in age from 5-28 years. We find a reliable developmental trend in both implicit and explicit performance in which the former cannot be attributed to the operation of explicit memory processes. Thus, we conclude that implicit memory, like explicit memory, develops with age.

Brain event-related potentials (ERPs) in schizophrenia during a word recognition memory task

Impairments of recognition memory for words and attenuation of the ERP 'old-new' effect have been found in patients with left medial temporal lobe damage. If left temporal lobe dysfunction in schizophrenia involves medial structures (e.g. hippocampus), then schizophrenic patients might show similar abnormalities of verbal recognition memory. This study recorded ERPs from 30 electrode sites while subjects were engaged in a continuous word recognition memory task. Results are reported for 24 patients having a diagnosis of schizophrenia (n = 16) or schizoaffective disorder (n = 8) and 19 age-matched healthy controls. Both patients and controls showed the expected 'old-new' effect, with greater late positivity to correctly recognized old words at posterior sites, and there was also no significant difference between groups in P3 amplitude. However, accuracy of word recognition memory was poorer in patients than controls, and patients showed markedly smaller N2 amplitude. Reduced amplitudes of N2 and N2-P3 were associated with poorer performance, with highest correlations over the left inferior parietal (N2) and left medial parietal (N2-P3) region. Moreover, patients failed to show significantly greater left than right hemisphere amplitude of N2-P3 at posterior sites, which was seen for healthy controls. These findings suggest that impaired word recognition in schizophrenia may arise from a left lateralized deficit at an early stage of processing, beginning at 200-300 ms after word onset.

Episodic priming and memory for temporal source: event-related potentials reveal age-related differences in prefrontal functioning

Event-related potentials (ERPs) were recorded from young (M = 25) and older (M = 71) adults during a recognition memory paradigm that assessed episodic priming. Participants studied two temporally distinct lists of sentences (each with two unassociated nouns). At test, in response to the nouns, participants made old-new, followed by remember (context)-know (familiarity) and source (i.e., list) judgments. Both young and older adults showed equivalent episodic priming effects. However, compared to the young adults, the older adults showed a greater source performance decrement than item memory performance decrement. Both age groups showed equivalent posterior-maximal old-new ERP effects. However, only the young produced a frontal-maximal, late onset old-new effect that differed as a function of subsequent list attribution. Because source memory is thought to be mediated by prefrontal cortex, we conclude that age-related memory differences may be due to a deficit in a prefrontal cortical system that underlies source memory and are not likely to be due to an age-related decline in episodic priming.

Comparison of treatment with fluorinated glucocorticoids to the natural history of autoantibody-associated congenital heart block: retrospective review of the research registry for neonatal lupus

OBJECTIVE

To compare intervention with fluorinated glucocorticoids to the natural history of untreated congenital heart block (CHB) with respect to conduction abnormalities, associated effusions, ascites, and hydrops fetalis, and the requirement for a pacemaker.

METHODS

Records of all mothers enrolled in the Research Registry for Neonatal Lupus were reviewed. The cohort includes 47 mothers whose sera contain anti-SSA/Ro or anti-SSB/La antibodies, and their 50 offspring with CHB, in whom at least 4 echocardiograms were performed after in utero diagnosis. In 28 pregnancies, mothers received dexamethasone 4-9 mg/day for 3-19 weeks or betamethasone 12-24 mg/week for >6 weeks (group A). In 22 pregnancies, fluorinated steroids were not used (group B).

RESULTS

Third-degree block was present in 21 fetuses in group A and 18 fetuses in group B; none were reversible despite steroid treatment. Three fetuses in group A and 2 in group B progressed from second-degree block, alternating with third-degree block, to permanent third-degree block at birth and postnatally. Of 4 fetuses in group A with second-degree block at presentation, all reverted to first-degree block by birth; 2 remain so at age 4 years, 1 alternates between first-degree and second-degree block at 2 years, and the fourth is in second-degree block at age 4 years. Of 2 fetuses in group B with second-degree block at presentation, both progressed to permanent third-degree block postnatally. Initial echocardiographic evaluation revealed pericardial effusions in 13 group A versus 4 group B fetuses, pleural effusions in 2 group A versus 0 group B, ascites in 8 group A versus 0 group B (P < 0.007), hydrops fetalis in 8 group A versus 0 group B (P < 0.007), and intrauterine growth restriction in 1 group A versus 1 group B. Pericardial effusions resolved and reappeared in both groups. Steroid therapy was most effective in the resolution of pleural effusions (2 of 2), ascites (6 of 8), and hydrops fetalis (5 of 8). Oligohydramnios ensued in 9 group A and 2 group B fetuses. Although fetuses in group A had more complications at presentation than those in group B, there were no significant differences in the duration of pregnancy (35.7 weeks versus 37.0 weeks), the number of deaths (4 versus 1), final degree of heart block, or requirement for a pacemaker (14 versus 11).

CONCLUSION

While prospective trials are needed, these data suggest that fluorinated steroids should be considered for fetuses with incomplete block or hydropic changes. Serial echocardiograms are recommended to monitor fetal progress. It remains to be determined whether third-degree block is reversible if therapy is initiated immediately upon detection.

Scaling is necessary when making comparisons between shapes of event-related potential topographies: a reply to Haig et al

A. R. Haig, E. Gordon, and S. Hook (1997) disputed G. McCarthy and C. C. Wood's (1985) contention that scaling should be used when assessing the statistical significance of between condition (or group) differences in the shapes of event-related potential (ERP) scalp topographies. Haig et al. based their contention upon the lack of empirical realism in McCarthy and Wood's model of within-group ERP noise, claiming that McCarthy and Wood's results could not be generalized to realistic ERP data. We argue, on both empirical and theoretical grounds, that Haig et al. do not make a compelling case against generalization of McCarthy and Wood's results. Moreover, Haig et al.'s conclusion is based upon a misconception of how scaling should be used. We conclude that when a quantitative measure of differences between topographic shapes is needed, scaling is not an option--it is a requirement.

ERP recordings during a picture fragment completion task: effects of memory instructions

Sequential implicit (picture fragment completion) and explicit (free recall and recognition) memory tasks were performed by two groups of young adults. Subjects assigned to the intentional condition were asked to memorize the stimuli presented during the picture fragment completion task, whereas subjects assigned to the incidental condition were not so instructed. In the picture fragment completion task, all subjects showed savings (priming), i.e., their identification thresholds for previously seen fragments were lower than those for fragments not previously seen, and no between-group performance difference was found. Free recall performance was better for the intentional than the incidental group, but recognition performance did not differ between the groups. Despite similar between-group performance, event-related brain potentials (ERPs) recorded during the picture fragment completion and recognition tasks revealed between-group differences in information processing. The ERP data suggest that similar behavioral performance during memory tasks may have been associated with distinct neuronal mechanisms subserving priming and recollection.