Christopher Bingham

Modern techniques of power spectrum estimation

The paper discusses the impact of the fast Fourier transform on the spectrum of time series analysis. It is shown that the computationally fastest way to calculate mean lagged products is to begin by calculating all Fourier coefficients with a fast Fourier transform and then to fast-Fourier-retransform a sequence made up ofa_{k}^{2}+b_{k}^{2}(wherea_{k}+ib_{k}are the complex Fourier coefficients). Also discussed are raw and modified Fourier periodograms, bandwidth versus stability aspects, and aims and computational approaches to complex demodulation. Appendixes include a glossary, a review of complex demodulation without fast Fourier transform, and a short explanation of the fast Fourier transform.

An Approximate Analysis of Variance Test for Non-Normality Suitable for Machine Calculation

Replacement by a simple approximation of expected values of order statistics in the Shapiro-Francis (1972) W′ statistics, yield a statistics that is more srlitable for machine computation. We show that is equivalent to W′ and discuss its percentage points.

Hypothalamic pituitary gonadal axis dysregulation in depressed women.

In order to examine HPG axis regulation in women with major depression, luteinizing hormone (LH) pulsativity was studied in 26 depressed and 24 normal women. Blood was sampled every 10 min for an 8-h period during the first week of their menstrual cycle. LH pulsatile release was analyzed using the computerized cluster analysis algorithm of Veldhuis and Johnson and spectral analysis. Compared to control women, depressed women had slower frequency dysrhythmic LH pulsatility. These results are consistent with a previously published pilot study which reported results of the first 23 subjects [Am. J. Psychiat. 154 (1997) 1454].

The volume density of cells and capillaries of the normal stria vascularis

The purpose of this study was to provide morphometric (i.e. quantitative anatomical) data on the normal chinchilla stria vascularis. Five normal chinchillas were used in the present investigation and four regions of the cochlea were examined in each animal. The width, radial area and number of marginal cells across the strias width increased from the cochlear apex toward the base. The increase in strial width and area appeared to be due to hyperplasia of the marginal cells. The mean total endolymphatic surface area of the stria vascularis was estimated to be 7.4 mm2 (S.E. = 1.23). The mean total volume of the stria vascularis was estimated to be 0.15 microliter (S.E. = 0.01). In addition, using a stereological method we found that the volume density of the cells and capillaries of the stria vascularis was constant along the length of the scala media. The mean (+/- S.E.) volume density of the stria cells and capillaries was estimated to be: marginal cells = 0.528 (0.013), intermediate cells = 0.212 (0.026), basal cells = 0.163 (0.009) and capillaries = 0.097 (0.009).

An identity involving partitional generalized binomial coefficients

Define coefficients (?[lambda]) by C[lambda](Ip + Z)/C[lambda](Ip) = [Sigma]k=0l [Sigma][varkappa][set membership, variant]k ([varkappa][lambda]) C?(Z)/C?(Ip), where the C[lambda]s are zonal polynomials in p by p matrices. It is shown that C[varkappa](Z) etr(Z)/k! = [Sigma]l=k[infinity] [Sigma][lambda][set membership, variant]l ([varkappa][lambda]) C[lambda](Z)/l!. This identity is extended to analogous identities involving generalized Laguerre, Hermite, and other polynomials. Explicit expressions are given for all ([varkappa][lambda]), [varkappa] [set membership, variant] k, k

Regulation of cognitive resources during an n-back task in youth-onset psychosis and attention-deficit/hyperactivity disorder (ADHD)

The goals of the current study were to use behavioral and pupillary measures to examine working memory on a spatial n-back task in 8-20-year-olds with youth-onset psychosis or ADHD (Combined subtype) and healthy controls to determine the contribution of different attentional factors to spatial working memory impairments, and to examine if age-related changes in performance differed across groups. Although both clinical groups had lower perceptual sensitivity on both 0- and 1-back, there was no evidence of an impairment in spatial working memory or differential order effects on the 0-back. Instead, results suggest that both clinical groups had difficulty encoding the stimuli. They also appeared to have difficulty maintaining attention and/or readiness to respond, and, to a lesser extent, recruiting resources on a trial-to-trial basis. It is likely that these attentional problems prevented the clinical groups from encoding the stimuli effectively and contributed to their general performance deficits.

Shared and Nonshared Symptoms in Youth-Onset Psychosis and ADHD

Objective: We compared ratings of behavior and attention problems between youth-onset psychosis and ADHD, two disorders in which attentional impairments play a key role, and examined the effect of psychostimulant use on age of onset in psychosis. Method: Parent and teacher ratings of behavioral problems and ADHD symptoms were collected using the Achenbach CBCL, TRF, and SNAP-IV Teacher Rating Scales on 42 participants with psychosis, 36 with ADHD and 57 controls (ages 8-19). Results and Conclusions: Results suggested that academic, externalizing, and attention problems reflect symptoms shared between the disorders, whereas internalizing, social and thought problems reflect factors that differ between disorders. Furthermore, participants with psychosis who had been prescribed psychostimulants had a younger age of onset of psychotic symptoms than those who had not. This difference could reflect dissimilarities in symptom severity symptom between subgroups or potentially harmful effects of psychostimulants in individuals predisposed to develop psychosis.

Incidental and Intentional Sequence Learning in Youth-Onset Psychosis and Attention-Deficit/Hyperactivity Disorder (ADHD)

The goal was to compare incidental and intentional spatial sequence learning in youth-onset psychosis and ADHD. The authors tested 8- to 19-year-olds with psychosis or ADHD and healthy controls on a serial reaction time (RT) task and used manual and oculomotor measures to examine learning. Participants were also administered a block in which they were explicitly instructed to learn a sequence. As in our previous studies with healthy adults and children, oculomotor anticipations and RTs showed learning effects similar to those in the manual modality. Results showed intact sequence-specific learning but fewer oculomotor anticipations in both clinical groups during incidental learning. In intentional learning, only the psychosis group showed impairments compared to controls. There were no interactions between age and diagnosis. Thus, the psychosis group showed relatively preserved incidental learning despite impairments in intentional learning. Additionally, both clinical groups showed impairments in the ability to search for, extract, and anticipate regularities (whether the regularities were there or not), but not in the ability to respond to these regularities when they were there.

An Approximation for the Distribution of the von Neumann Ratio

An approximation to the distribution of the von Neumann ratio T = used for testing independence. is presented. The approximation consists of treating [(n 2 – l)/(n 2 – 4)]½(1 – ½T) as a Pearson correlation coefficient on n + 3 observations. Probability points based on this approximation are compared with exact values and with values derived from two other approximations. It yields three decimal accuracy for n ≥ 9 and four decimal accuracy for n ≥ 15.

Oculomotor and Pupillometric Indices of Pro- and Antisaccade Performance in Youth-Onset Psychosis and Attention Deficit/Hyperactivity Disorder

The goals of the study were to examine inhibitory deficits on the antisaccade task in 8- to 20-year olds with youth-onset psychosis or attention deficit/hyperactivity disorder (ADHD) and healthy controls and to examine if age-related changes in performance differed across groups. In addition to the conventional measures of performance, pupillary dilations were used to obtain estimates of phasic and tonic level of arousal. Results showed that the psychosis, but not the ADHD, group had elevated antisaccade error rates; however, variability of error rates was high in all groups. These inhibitory failures were accompanied by a lower level of momentary cognitive effort (as indexed by pupillary dilations). The largest differences between the control and clinical groups were found not in the expected indices of inhibition but in the probability of correcting inhibitory errors and in variability of antisaccade response times, which were correlated with each other. These findings did not appear to be attributable to a deficit in maintaining task instructions in mind in either disorder or lack of motivation in ADHD. Instead, results point to impairments in both clinical groups in sustaining attention on a trial-by-trial basis, resulting in deficits in self-monitoring. Thus, results show inhibitory deficits in the context of more general attentional impairments in both disorders.