Biomedical subjects

Kert Viele

Publications and source records attributed to Kert Viele.

4 recordsLinked to original sources

PubMed2006

Automated classification of evoked quantal events.

We provide both theoretical and computational improvements to the analysis of synaptic transmission data. Theoretically, we demonstrate the correlation structure of observations within evoked postsynaptic potentials (EPSP) are consistent with multiple random draws from a common autoregressive moving-average (ARMA) process of order (2, 2). We use this observation and standard time series results to construct a statistical hypothesis testing procedure for determining whether a given trace is an EPSP. Computationally, we implement this method in R, a freeware statistical language, which reduces the amount of time required for the investigator to classify traces into EPSPs or non-EPSPs and eliminates investigator subjectivity from this classification. In addition, we provide a computational method for calculating common functionals of EPSPs (peak amplitude, decay rate, etc.). The methodology is freely available over the internet. The automated procedure to index the quantal characteristics greatly facilitates determining if any one or multiple parameters are changing due to experimental conditions. In our experience, the software reduces the time required to perform these analyses from hours to minutes.

Animals↗

PubMed2006

Self-modeling structure of evoked postsynaptic potentials.

With the simplicity of the synaptic structure and physiology at neuromuscular junctions (NMJs) of crayfish and the given transmitter being released in quantal packets, a detailed assessment in the fundamental processes of chemical synaptic transmission is possible. Since the quantal event is the basic element of transmission, we consider an approach to further understand the characteristics of quantal responses. In this study, we introduce a method for combining information across excitatory postsynaptic potentials (EPSPs) that are quantal in nature. The method is called self-modeling regression, known in the statistics literature as SEMOR. This method illustrates that the differing timing and heights of EPSPs can be described with four coefficients measuring affine (shift and scale) transformations of the x and y axes. We demonstrate that this relationship allows us to provide a unified schema for the many functionals currently used in the literature, such as peak amplitude, tau, latency, area under the curve, or decay time. Computer code in R is available on the internet to perform the analysis.

Animals↗

PubMed2003

Estimating the number of release sites and probability of firing within the nerve terminal by statistical analysis of synaptic charge.

Investigating the function of individual synapses is essential to understanding the mechanisms that influence the efficacy of chemical synaptic transmission. The known simplicity of the synaptic structure at the crayfish neuromuscular junction (NMJ) and its quantal nature of release allows an assessment of discrete synapses within the motor nerve terminals. Our goal in this article is to investigate the effect of the stimulation frequency on the number of active release sites (n) and the probability of release (p) at those active sites. Because methods based on direct counts often provide unstable joint estimates of (n) and (p), we base our analysis on mixture modeling. In particular, the mixture modeling approach is used to estimate (n) and (p) for stimulation frequencies of 1 Hz, 2 Hz, and 3 Hz. Our results indicate that as the stimulation frequency increases, new sites are recruited (thus increasing n) and the probability of release (p) increases.

Action Potentials↗

PubMed2002

Grammatical morphology and perception of synthetic and natural speech in children with specific language impairments.

Studies investigating the relationship between the use of inflectional morphology and speech-perception abilities in children with SLI traditionally have employed synthetic speech stimuli. The purpose of this study was to replicate the findings reported in Leonard, McGregor, and Allen (1992) with an older group of children with SLI and to determine if the pattern of deficits seen for synthetic speech extends to perception of natural speech stimuli. The speech-perception abilities of 27 children between the ages of 6;11 and 8;11 (15 SLI and 12 NL) were compared using natural and synthetic versions of the [das]-[daS], [dabiba]-[dabuba], and [i]-[u] contrast pairs originally used in Leonard et al. The findings reported by Leonard et al. were replicated with synthetic speech but not for the natural speech. Use of inflectional morphology in obligatory contexts by the children with SLI was not significantly correlated with their perception abilities for any of the natural or synthetic speech-contrast pairs. Further, although both groups' ability to maintain the target contrast in memory declined over the span of the trials for all target contrasts for both natural and synthetic speech, the rate of decline did not differ significantly between the SLI and NL groups. Findings are discussed with respect to possible deficits in linking phonological representations to grammatical representations in children with SLI.

Child↗