Ambivalent Affines: Law Like Literature

This short essay will dwell upon the ‘law of literature and the literature of law’, as illuminated in the enduring scholarship and intellectual legacy of Peter Fitzpatrick. Reading with Fitzpatrick, we must grapple with a law that is both constituted and subverted by recourse to the supplement of fiction. These ambivalent ‘affines’, law and literature, share in an oscillatory rhythm: each is constituted and enlivened by an unbounded exteriority, yet each must be rendered normatively determinate. I reflect upon the ways in which Fitzpatrick’s account of ‘law like literature’ grasps and hones the methodological challenge implicit in this reading: to read law as literature and literature as law. Yet further, I extend a reading of Fitzpatrick’s scholarship that acknowledges this fictive law as not merely susceptible to but constituted by decoloniality.

Modulation of cortical slow oscillatory rhythm by GABAB receptors: an experimental and computational study

Slow wave oscillations (SWO) dominate cortical activity during deep sleep, anesthesia and in some brain lesions. SWO consist of Up states or periods of activity interspersed with Down states or periods of silence. The rhythmicity expressed during SWO integrates neuronal and connectivity properties of the network and it is often altered in neurological pathological conditions. Different mechanisms have been proposed to drive the transitions between Up and Down states, in particular, adaptation mechanisms have been proposed to contribute to the Up-to-Down transition. Synaptic inhibition, and specially GABAB receptors, have also been proposed to have a role in the termination of Up states. The interplay between these two potential mechanisms, adaptation and inhibition, is not well understood and the role of slow inhibition is not yet clear regarding the full cycle of the slow oscillatory rhythm. Here we contribute to its understanding by combining experimental and computational techniques. GABAB receptors-blockade not only elongated Up states, but also affected the subsequent Down states, and thus the whole cycle of the oscillations. Furthermore, while adaptation tends to yield a rather regular behavior, GABAB receptors-blockade decreased the variability of the sequence of Up and Down states. Interestingly, variability changes could be accomplished in two different ways: either accompanied by a shortening or by a lengthening of the duration of the Down state. Even when the most common observation is the lengthening of the Down states, both changes are expressed experimentally and also in numerical simulations. Our simulations suggest that the sluggishness of GABAB receptors to follow the excitatory fluctuations of the cortical network can explain these different network dynamics modulated by GABAB receptors.

Theta phase coordinated memory reactivation reoccurs in a slow-oscillatory rhythm during NREM sleep

It has been proposed that sleep’s contribution to memory consolidation is to reactivate prior encoded information. To elucidate the neural mechanisms carrying reactivation-related mnemonic information, we investigated whether content-specific memory signatures associated with memory reactivation during wakefulness reoccur during subsequent sleep. We show that theta oscillations orchestrate the reactivation of memories, irrespective of the physiological state. Reactivation patterns during sleep autonomously re-emerged at a rate of 1 Hz, indicating a coordination by slow oscillatory activity.

Continuous lateral oscillations as a core mechanism for taxis in Drosophila larvae

Taxis behaviour in Drosophila larva is thought to consist of distinct control mechanisms triggering specific actions. Here, we support a simpler hypothesis: that taxis results from direct sensory modulation of continuous lateral oscillations of the anterior body, sparing the need for ‘action selection’. Our analysis of larvae motion reveals a rhythmic, continuous lateral oscillation of the anterior body, encompassing all head-sweeps, small or large, without breaking the oscillatory rhythm. Further, we show that an agent-model that embeds this hypothesis reproduces a surprising number of taxis signatures observed in larvae. Also, by coupling the sensory input to a neural oscillator in continuous time, we show that the mechanism is robust and biologically plausible. The mechanism provides a simple architecture for combining information across modalities, and explaining how learnt associations modulate taxis. We discuss the results in the light of larval neural circuitry and make testable predictions.

Neural oscillations as a signature of efficient coding in the presence of synaptic delays

Cortical networks exhibit 'global oscillations', in which neural spike times are entrained to an underlying oscillatory rhythm, but where individual neurons fire irregularly, on only a fraction of cycles. While the network dynamics underlying global oscillations have been well characterised, their function is debated. Here, we show that such global oscillations are a direct consequence of optimal efficient coding in spiking networks with synaptic delays and noise. To avoid firing unnecessary spikes, neurons need to share information about the network state. Ideally, membrane potentials should be strongly correlated and reflect a 'prediction error' while the spikes themselves are uncorrelated and occur rarely. We show that the most efficient representation is when: (i) spike times are entrained to a global Gamma rhythm (implying a consistent representation of the error); but (ii) few neurons fire on each cycle (implying high efficiency), while (iii) excitation and inhibition are tightly balanced. This suggests that cortical networks exhibiting such dynamics are tuned to achieve a maximally efficient population code.

Neural oscillations as a signature of efficient coding in the presence of synaptic delays

Cortical networks exhibit "global oscillations", in which neural spike times are entrained to an underlying oscillatory rhythm, but where individual neurons fire irregularly, on only a fraction of cycles. While the network dynamics underlying global oscillations have been well characterised, their function is debated. Here, we show that such global oscillations are a direct consequence of optimal efficient coding in spiking networks with synaptic delays. To avoid firing unnecessary spikes, neurons need to share information about the network state. Ideally, membrane potentials should be strongly correlated and reflect a "prediction error" while the spikes themselves are uncorrelated and occur rarely. We show that the most efficient representation is achieved when: (i) spike times are entrained to a global Gamma rhythm (implying a consistent representation of the error); but (ii) few neurons fire on each cycle (implying high efficiency), while (iii) excitation and inhibition are tightly balanced. This suggests that cortical networks exhibiting such dynamics are tuned to achieve a maximally efficient population code.