Biomedical subjects

J Pressing

Publications and source records attributed to J Pressing.

5 recordsLinked to original sources

PubMed1998

Error Correction Processes in Temporal Pattern Production.

A second-order autoregressive model for error correction is applied to measurements of synchronized tapping by an expert and a nonexpert subject for a wide range of patterns, ranging from simple off-beat tapping to a complex polyrhythm. The model can be seen as an extension of the first order approach of Vorberg and Wing and, also, as a linearized version of a general nonlinear model proposed by the author in another publication. The central measured variable is the asynchrony between presented tone and produced tap. General relations for the asynchrony autocovariance functions are derived, as well as covariance-based expressions for first- and second-order autoregressive error correction parameters. A second method of error parameter estimation, based on "local" binned calculations, is also presented. Combination of the two methods, buttressed by simulations, allows effective characterization of the time series' order and parameter values, and experimental support for the model is found to be strong in all cases. Error correction processes prove to be predominantly first order; second (and possibly higher) order effects occur predominantly under conditions of expertise and relatively high task demands. Expertise in tapping (as determined from these two subjects) is found to lead to reduced bias, reduced asynchrony and interonset variance, and, with the exception of a single case, increased values of error correction parameters relative to untrained performance. In a clear majority of cases where it could be tested, both the AR1 error correction parameter alpha, and the asynchrony and interonset standard deviations showed a strong tendency towards a linear relationship with tapping period. Copyright 1998 Academic Press.

Journal Article↗

PubMed1997

Spectral properties of human cognition and skill.

Many interactive human skills are based on real-time error detection and correction. Here we investigate the spectral properties of such skills, focusing on a synchronization task. A simple autoregressive error correction model, based on separate 'motor' and 'cognitive' sources, provides an excellent fit to experimental spectral data. The model can also apply to recurrent processes not based on error correction, allowing commentary on previous claims of 1/f-type noise in human cognition. A comparison of expert and non-expert subjects suggests that performance skill is not only based on reduced variance and bias, but also on the construction of richer mental models of error correction.

Cognition↗

PubMed1984

Temperature as a determinative factor in the evolution of genetic systems.

Heat induces a number of premutational lesions (for example, the deamination of cytosine to uracil) in DNA and RNA. These kinds of errors occur in resting as well as replicating polynucleotides. However, an increase in temperature also raises the probability of copying error occurring in nucleic acids because of increased thermal noise in the replicative machinery. In most modern genetic systems, the majority of heat-induced lesions are efficiently repaired. It follows that the importance of heat-induced error increases as the effectiveness of repair declines. We show in this paper that the error rate of enzymatic polynucleotide copying is expected to increase monotonically with temperature. We also explore the effects of temperature variations on the early evolution of biological information transmission mechanisms.

Biological Evolution↗

PubMed1984

Divided genomes and intrinsic noise.

Segmental genomes (i.e., genomes in which the genetic information is dispersed between two or more discrete molecules) are abundant in RNA viruses, but virtually absent in DNA viruses. It has been suggested that the division of information in RNA viruses expands the pool of variation available to natural selection by providing for the reassortment of modular RNAs from different genetic sources. This explanation is based on the apparent inability of related RNA molecules to undergo the kinds of physical recombination that generate variation among related DNA molecules. In this paper we propose a radically different hypothesis. Self-replicating RNA genomes have an error rate of about 10(-3) - 10(-4) substitutions per base per generation, whereas for DNA genomes the corresponding figure is 10(-9) - 10(-11). Thus the level of noise in the RNA copier process is five to eight orders of magnitude higher than that in the DNA process. Since a small module of information has a higher chance of passing undamaged through a noisy channel than does a large one, the division of RNA viral information among separate small units increases its overall chances of survival. The selective advantage of genome segmentation is most easily modelled for modular RNAs wrapped up in separate viral coats. If modular RNAs are brought together in a common viral coat, segmentation is advantageous only when interactions among the modular RNAs are selective enough to provide some degree of discrimination against miscopied sequences. This requirement is most clearly met by the reoviruses.

Biological Evolution↗

PubMed1983

Intrinsic noise and the design of the genetic machinery.

Darwinian theory envisages 'selection pressure' as a stress imposed on the genotype by the environment. However, noise in the replicative and translational mechanisms in itself imposes a significant 'pressure' on the adaptive fitness of the organism. We propose that the biosphere has been shaped by both extrinsic (environmental) and intrinsic (noise-generated) factors. Because noise has been a remorseless and ever-present background to the evolutionary process, adaptations to this intrinsic pressure include not only a variety of familiar genetic mechanisms but also many anatomical and life-style characteristics that focus on the transmission of information between generations.

Animals↗