Neural Network Evidence for the Coupling of Presaccadic Visual Remapping to Predictive Eye Position Updating.

As we look around a scene, we perceive it as continuous and stable even though each saccadic eye movement changes the visual input to the retinas. How the brain achieves this perceptual stabilization is unknown, but a major hypothesis is that it relies on presaccadic remapping, a process in which neurons shift their visual sensitivity to a new location in the scene just before each saccade. This hypothesis is difficult to test in vivo because complete, selective inactivation of remapping is currently intractable. We tested it in silico with a hierarchical, sheet-based neural network model of the visual and oculomotor system. The model generated saccadic commands to move a video camera abruptly. Visual input from the camera and internal copies of the saccadic movement commands, or corollary discharge, converged at a map-level simulation of the frontal eye field (FEF), a primate brain area known to receive such inputs. FEF output was combined with eye position signals to yield a suitable coordinate frame for guiding arm movements of a robot. Our operational definition of perceptual stability was "useful stability," quantified as continuously accurate pointing to a visual object despite camera saccades. During training, the emergence of useful stability was correlated tightly with the emergence of presaccadic remapping in the FEF. Remapping depended on corollary discharge but its timing was synchronized to the updating of eye position. When coupled to predictive eye position signals, remapping served to stabilize the target representation for continuously accurate pointing. Graded inactivations of pathways in the model replicated, and helped to interpret, previous in vivo experiments. The results support the hypothesis that visual stability requires presaccadic remapping, provide explanations for the function and timing of remapping, and offer testable hypotheses for in vivo studies. We conclude that remapping allows for seamless coordinate frame transformations and quick actions despite visual afferent lags. With visual remapping in place for behavior, it may be exploited for perceptual continuity.

Akrasia and the Aesthetic: Human Agency and the Site of Literature, 1760-1820

This study focuses on a series of foundational stylistic and formal innovations in eighteenth-century and Romantic literature, and argues that they can be cumulatively attributed to the distinct challenges authors faced in representing human action and the will. The study focuses in particular on cases of “acting against better judgment” or “failing to do what one knows one ought to do” – concepts originally theorized as “akrasia” and “weakness of the will” in ancient Greek and Scholastic thought. During the Enlightenment, philosophy increasingly conceives of human minds and bodies like systems and machines, and consequently fails to address such cases except as intractable or incoherent. Yet eighteenth-century and Romantic narratives and poetry consistently engage the paradoxes and ambiguities of action and volition in representations of akrasia. As a result, literature develops representational strategies that distinguish the epistemic capacities of literature as privileged over those of philosophy.

The study begins by centering on narratives of distempered selves from the 1760s. Jean-Jacques Rousseau’s Confessions and Laurence Sterne’s A Sentimental Journey narrate cases of knowingly and weakly acting against better judgment, and in so doing, reveal the limitations of the “philosophy of the passions” that famously informed sentimental literature at the time. These texts find that the interpretive difficulties of action demand a non-systematic and hermeneutic approach to interpreting a self through the genre of narrative. Rousseau’s narrative in particular informs William Godwin’s realist novels of distempered subjects. Departing from his mechanistic philosophy of mind and action, Godwin develops the technique of free indirect discourse in his third novel Fleetwood (1805) as a means of evoking the ironies and self-deceptions in how we talk about willing.

Romantic poetry employs the literary trope of weakness of will primarily through the problem of regretted inaction – a problem which I argue motivates the major poetic innovations of William Wordsworth and John Keats. While Samuel Taylor Coleridge sought to characterize his weakness of will in philosophical writing, Wordsworth turns to poetry with The Prelude (1805), revealing poetry itself to be a self-deceiving and disappointing form of procrastination. More explicitly than Wordsworth, John Keats identifies indolence as the prime symbol and basis of what he calls “negative capability.” In his letters and poems such as “On Seeing the Elgin Marbles” (1817) and “Ode on Indolence” (1819), Keats reveals how the irreducibly contradictory qualities of human agency speak to the particular privilege of “disinterested aesthetics” – a genre fitted for the modern era for its ability to disclose contradictions without seeking to resolve or explain them in terms of component parts.