T domain factors regulate developmental processes such as oogenesis, gastrulation, neurogenesis, and limb development throughout the animal kingdom (for review, see Smith 1999) and form a super family of at least seven subgroups (Wattler et al. 1998). The best-characterized subgroup are the Brachyury-type T domain proteins that have been found in ascidians, cephalochordates, sea urchins, star fish, hemichordates, jellyfish, and insects (Smith 1999;Technau and Bode 1999;Shoguchi et al. 2000). The Brachyury homologs are expressed in the gut and the posterior mesoderm where they appear to have virtually the same functions in the different phyla (Kusch and Reuter 1999;Smith 1999;Bassham and Postlethwait 2000;Woollard and Hodgkin 2000). In some clades, the expression in either of the tissues is transient or missing; in these cases the respective aspect of Brachyury function might have been lost during evolution (e.g., Peterson et al. 1999;Bassham and Postlethwait 2000).Brachyury proteins act as transcriptional activators and can bind to a 24-bp palindromic target sequence, which was identified based on the binding site selection method . X-ray crystallography revealed an association of the target sequence with two T domains, which are in close contact on the palindrome (Mü ller and Herrmann 1997). However, the arrangement of binding sites in a palindrome is not a requirement for transcriptional activation by Brachyury: certain combinations of 12-bp halves of the palindromic sequence are sufficient (Kispert et al. 1995). Likewise, the binding sites so far characterized in vivo were solely homologous to palindrome halves. Within the regulatory region of efgf, the first identified target gene of the Xenopus Brachyury protein Xbra, only two half sites were found .The Drosophila Brachyury homolog Brachyenteron (Byn) acts in the development of the hindgut and of certain muscle precursors of the midgut (Kispert et al. 1994;Singer et al. 1996;Kusch and Reuter 1999). Byn certainly functions through a larger set of target genes in both developmental processes. One of those is the homeobox

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Looking at objects is one of the most basic sensorimotor behaviours, which requires calibration of the perceptual and motor systems. Recently, we have introduced a neural-dynamic architecture, in which the sensorimotor transformations, which lead to precise saccadic gaze shifts, is initially learned and is autonomously updated if changes in the environment or in the motor plant of the agent require adaptation. Here, we demonstrate how the allocentric, gazedirection independent memory representations may be formed in this architecture and how sequences of precise gaze shifts may be generated to memorised targets. Our simulated robotic experiments demonstrate functioning of the architecture on an autonomous embodied agent.

Abstract-This paper presents a neurally-inspired architecture for learning to reach toward visually-perceived targets. The whole behavioural loop from object perception to motor control is realised in the architecture of interconnected Dynamic Neural Fields. The sensory-motor mappings, involved in generation of saccadic gaze shifts and reaching arm movements, adapt in the system autonomously along with the generated behaviour. A network of neural-dynamic nodes organises activation and deactivation of the behavioural modules of the architecture in time, leading to an autonomous process model of development of looking and reaching. The architecture was implemented and validated in a simulated robotic agent.