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B Crespi

Publications and source records attributed to B Crespi.

10 recordsLinked to original sources
PubMed2006

Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism.

We describe a new hypothesis for the development of autism, that it is driven by imbalances in brain development involving enhanced effects of paternally expressed imprinted genes, deficits of effects from maternally expressed genes, or both. This hypothesis is supported by: (1) the strong genomic-imprinting component to the genetic and developmental mechanisms of autism, Angelman syndrome, Rett syndrome and Turner syndrome; (2) the core behavioural features of autism, such as self-focused behaviour, altered social interactions and language, and enhanced spatial and mechanistic cognition and abilities, and (3) the degree to which relevant brain functions and structures are altered in autism and related disorders. The imprinted brain theory of autism has important implications for understanding the genetic, epigenetic, neurological and cognitive bases of autism, as ultimately due to imbalances in the outcomes of intragenomic conflict between effects of maternally vs. paternally expressed genes.

Autistic Disorder↗
PubMed2003

The evolution of inquilinism, host-plant use and mitochondrial substitution rates in Tamalia gall aphids.

We used mitochondrial DNA data to infer phylogenies for 28 samples of gall-inducing Tamalia aphids from 12 host-plant species, and for 17 samples of Tamalia inquilinus, aphid 'inquilines' that obligately inhabit galls of the gall inducers and do not form their own galls. Our phylogenetic analyses indicate that the inquilines are monophyletic and closely related to their host aphids. Tamalia coweni aphids from different host plants were, with one exception, very closely related to one another. By contrast, the T. inquilinus aphids were strongly genetically differentiated among most of their host plants. Comparison of branch lengths between the T. coweni clade and the T. inquilinus clade indicates that the T. inquilinus lineage evolves 2.5-3 times faster for the cytochrome oxidase I gene. These results demonstrate that: (1) Tamalia inquilines originated from their gall-inducing hosts, (2) communal (multi-female) gall induction apparently facilitated the origin of inquilinism, (3) diversification of the inquilines has involved rapid speciation along host-plant lines, or the rapid evolution of host-plant races, and (4) the inquilines have undergone accelerated molecular evolution relative to their hosts, probably due to reduced effective population sizes. Our findings provide insight into the behavioural causes and evolutionary consequences of transitions from resource generation to resource exploitation.

Animals↗
PubMed1999

Storage capacity of non-monotonic neurons.

Non-monotonic neurons have been shown to enhance the storage capacity of auto-associative memories. This work investigates the retrieval capacities of different types of non-monotonic neurons. It is found that storage capacity is maximized when the neuron response is a function with well defined geometrical characteristics. Numerical experiments demonstrate that storage capacity is directly related to the dynamical property of the iterative map, x(i)-->g( summation operator jT(ij)x(j)), that describes the network evolution. Maximum capacity is reached when the neuron dynamics are subdivided into two non-overlapping "erratic bands" around points x(i)=+/-1. The capacity improvements are explained in terms of the energy function associated with the network dynamics.

Journal Article↗