Oscillating latent dynamics in robot systems during walking and reaching.

Sensorimotor control of complex, dynamic systems such as humanoids or quadrupedal robots is notoriously difficult. While artificial systems traditionally employ hierarchical optimisation approaches or black-box policies, recent results in systems neuroscience suggest that complex behaviours such as locomotion and reaching are correlated with limit cycles in the primate motor cortex. A recent result suggests that, when applied to a learned latent space, oscillating patterns of activation can be used to control locomotion in a physical robot. While reminiscent of limit cycles observed in primate motor cortex, these dynamics are unsurprising given the cyclic nature of the robot's behaviour (walking). In this preliminary investigation, we consider how a similar approach extends to a less obviously cyclic behaviour (reaching). This has been explored in prior work using computational simulations. But simulations necessarily make simplifying assumptions that do not necessarily correspond to reality, so do not trivially transfer to real robot platforms. Our primary contribution is to demonstrate that we can infer and control real robot states in a learnt representation using oscillatory dynamics during reaching tasks. We further show that the learned latent representation encodes interpretable movements in the robot's workspace. Compared to robot locomotion, the dynamics that we observe for reaching are not fully cyclic, as they do not begin and end at the same position of latent space. However, they do begin to trace out the shape of a cycle, and, by construction, they are driven by the same underlying oscillatory mechanics.

Identification of putative rat ribonuclease III by differential display: a novel rat mRNA expressed in a circadian manner in the rat suprachiasmatic nucleus.

The suprachiasmatic nucleus (SCN) of the hypothalamus constitutes the principal site responsible for the generation and entrainment of circadian rhythms in mammals. The mechanisms of the circadian clock involve periodic gene expression. Here we report the use of differential display reverse transcriptase polymerase chain reaction to identify a novel rat mRNA sequence which is highly homologous to human ribonuclease III. Analysis of its expression in the rat brain by in situ hybridization histochemistry showed this transcript to be expressed at differing intensities at various sites. Temporal variation in expression was observed in the SCN, with a peak at circadian time (CT) 2 and a nadir at CT14. No significant changes in its expression were detected across the cycle within the supraoptic nucleus, cingulate cortex or caudate putamen.