The Effect of Knowledge of Upcoming Haptic Feedback on Normal and Pantomime Grasps

Normal grasping actions towards real objects are target-directed, mediated via real-time visuomotor control, and provide haptic feedback. Studies of visual form agnosic patient DF suggest that pantomime (pretend) grasps are different; they recruit the visual Ventral stream (inferior temporal cortex), while normal grasps recruit the visual Dorsal stream (posterior parietal cortex). This functional duality underlies the eponymous Two Visual Systems Hypothesis (TVSH). Critics of the TVSH emphasize the multimodal nature of sensory processing and propose a model, termed the Common Source Hypothesis (CSH), of a single more localized system. Existing studies of natural prehension during interleaved trials of normal and pantomime grasps are presented as supporting the CSH, as are reports that pantomime grasps are unsusceptible to knowledge of haptic feedback availability. However, these studies have methodological shortcomings that compromise their results. The current study replicated these experiments while eliminating those methodological shortcomings. Healthy participants performed grasping tasks involving cylinders presented to the participant using a mirror setup, while data on grasp kinematics were recorded. Normal and pantomime grasps were used to recruit the dorsal and ventral streams respectively. We found that when interleaving normal and pantomime grasps and controlling for knowledge of upcoming haptic feedback, pantomime grasps displayed the expected decrements in precision, supporting the TVSH. Additionally, pantomime grasps were susceptible to manipulation of knowledge whereas normal grasps were not, indicating a bifurcation of the visual system by degree of cognitive accessibility. These findings highlight the important role of cognition in mediating grasping actions when a participant knows there will not be haptic feedback on the upcoming grasp

Turning money into speech: campaign finance, political advertising, and the civic sphere

In this dissertation, I trace the history of campaign finance reform's influence on political advertising. I track the discourses held within Congress and court hearings to uncover what I call the money-speech paradigm, the ideological principles behind the construction of the marketplace of ideas. I then examine how the relationship between money and speech impacts the production of political advertisements to evaluate the strength of speech within presidential elections from 1976 to 2016. My findings show that campaign spending is being increasingly reregulated to serve interest groups rather than the public. While more opportunities to engage in independent speech emerged, the number of truly autonomous groups has seen little change. In contrast, the number of political advertisers coordinating with one another regularly grows. This came about through a view competition that assumes diversity will naturally occur, resulting in the deregulation of political speech by emphasizing that political advertisers be independent from the government and not each other while expanding who can produce advertisements. As a result, the U.S. government left the diversity of speech unprotected. I use this data to suggest the use of a new metaphor for campaign finance reform. Specifically, I suggest that viewing campaign finance reform as the creation of icebergs-large dense networks of political power that are only partially visible is more apt than the hydraulics used by some legal scholars in the past.Includes bibliographical references

Combinatorial synthesis and high-throughput photopotential and photocurrent screening of mixed-metal oxides for photoelectrochemical water splitting

A high-throughput method has been developed using a commercial piezoelectric inkjet printer for synthesis and characterization of mixed-metal oxide photoelectrode materials for water splitting. The printer was used to deposit metal nitrate solutions onto a conductive glass substrate. The deposited metal nitrate solutions were then pyrolyzed to yield mixed-metal oxides that contained up to eight distinct metals. The stoichiometry of the metal oxides was controlled quantitatively, allowing for the creation of vast libraries of novel materials. Automated methods were developed to measure the open-circuit potentials (Eoc), short-circuit photocurrent densities (Jsc), and current density vs. applied potential (J–E) behavior under visible light irradiation. The high-throughput measurement of Eoc is particularly significant because open-circuit potential measurements allow the interfacial energetics to be probed regardless of whether the band edges of the materials of concern are above, close to, or below the values needed to sustain water electrolysis under standard conditions. The Eoc measurements allow high-throughput compilation of a suite of data that can be associated with the composition of the various materials in the library, to thereby aid in the development of additional screens and to form a basis for development of theoretical guidance in the prediction of additional potentially promising photoelectrode compositions

SUSY Gauge Dynamics and Singularities of 4d N=1 String Vacua

Many N=1 heterotic string compactifications exhibit physically mysterious singularities at codimension one in the moduli space of vacua. At these singularities, Yukawa couplings of charged fields develop poles as a function of the moduli. We explain these conformal field theory singularities, in a class of examples, as arising from non-perturbative gauge dynamics of non-perturbative gauge bosons (whose gauge coupling is the sigma model coupling) in the string theory.Comment: 17 pages, harvmac bi

Elliptic curves over a finite field and the trace formula

We prove formulas for power moments for point counts of elliptic curves over a finite field $k$ such that the groups of $k$-points of the curves contain a chosen subgroup. These formulas express the moments in terms of traces of Hecke operators for certain congruence subgroups of $\operatorname{SL}_2(\mathbb{Z})$. As our main technical input we prove an Eichler-Selberg trace formula for a family of congruence subgroups of $\operatorname{SL}_2(\mathbb{Z})$ which include as special cases the groups $\Gamma_1(N)$ and $\Gamma(N)$. Our formulas generalize results of Birch and Ihara (the case of the trivial subgroup, and the full modular group), and previous work of the authors (the subgroups $\mathbb{Z}/2\mathbb{Z}$ and $(\mathbb{Z}/2\mathbb{Z})^2$ and congruence subgroups $\Gamma_0(2),\Gamma_0(4)$). We use these formulas to answer statistical questions about point counts for elliptic curves over a fixed finite field, generalizing results of Vl\v{a}du\c{t}, Gekeler, Howe, and others.Comment: To appear in Proc. London Math. Soc. 61 page

The Role of Haptic Expectations in Reaching to Grasp: From Pantomime to Natural Grasps and Back Again

© Copyright © 2020 Whitwell, Katz, Goodale and Enns. When we reach to pick up an object, our actions are effortlessly informed by the object’s spatial information, the position of our limbs, stored knowledge of the object’s material properties, and what we want to do with the object. A substantial body of evidence suggests that grasps are under the control of “automatic, unconscious” sensorimotor modules housed in the “dorsal stream” of the posterior parietal cortex. Visual online feedback has a strong effect on the hand’s in-flight grasp aperture. Previous work of ours exploited this effect to show that grasps are refractory to cued expectations for visual feedback. Nonetheless, when we reach out to pretend to grasp an object (pantomime grasp), our actions are performed with greater cognitive effort and they engage structures outside of the dorsal stream, including the ventral stream. Here we ask whether our previous finding would extend to cued expectations for haptic feedback. Our method involved a mirror apparatus that allowed participants to see a “virtual” target cylinder as a reflection in the mirror at the start of all trials. On “haptic feedback” trials, participants reached behind the mirror to grasp a size-matched cylinder, spatially coincident with the virtual one. On “no-haptic feedback” trials, participants reached behind the mirror and grasped into “thin air” because no cylinder was present. To manipulate haptic expectation, we organized the haptic conditions into blocked, alternating, and randomized schedules with and without verbal cues about the availability of haptic feedback. Replicating earlier work, we found the strongest haptic effects with the blocked schedules and the weakest effects in the randomized uncued schedule. Crucially, the haptic effects in the cued randomized schedule was intermediate. An analysis of the influence of the upcoming and immediately preceding haptic feedback condition in the cued and uncued random schedules showed that cuing the upcoming haptic condition shifted the haptic influence on grip aperture from the immediately preceding trial to the upcoming trial. These findings indicate that, unlike cues to the availability of visual feedback, participants take advantage of cues to the availability of haptic feedback, flexibly engaging pantomime, and natural modes of grasping to optimize the movement

4-aminopyridine toxicity: a case report and review of the literature.

INTRODUCTION: 4-Aminopyridine (4-AP) selectively blocks voltage-gated potassium channels, prolongs the action potential, increases calcium influx, and subsequently, enhances interneuronal and neuromuscular synaptic transmission. This medication has been studied and used in many disease processes hallmarked by poor neuronal transmission in both the central and peripheral nervous systems including: multiple sclerosis (MS), spinal cord injuries (SCI), botulism, Lambert-Eaton syndrome, and myasthenia gravis. It has also been postulated as a potential treatment of verapamil toxicity and reversal agent for anesthesia-induced neuromuscular blockade. To date, there have been limited reports of either intentional or accidental 4-AP toxicity in humans. Both a case of a patient with 4-AP toxicity and review of the literature are discussed, highlighting commonalities observed in overdose. CASE REPORT: A 37-year-old man with progressive MS presented with diaphoresis, delirium, agitation, and choreathetoid movements after a presumed 4-AP overdose. 4-AP concentration at 6 h was 140 ng/mL. With aggressive benzodiazepine administration and intubation, he recovered uneventfully. DISCUSSION: The commonalities associated with 4-AP toxicity conforms to what is known about its mechanism of action combining cholinergic features including diaphoresis, altered mental status, and seizures with dopamine-related movement abnormalities including tremor, choreoathetosis, and dystonia. Management of patients poisoned by 4-AP centers around good supportive care with definitive airway management and controlling CNS hyperexcitability aggressively with gamma-aminobutyric acid agonist agents. Adjunctive use of dopamine antagonists for extrapyramidal effects after sedation is a treatment possibility. As 4-aminopyridine recently received Federal Drug Administration approval for the treatment of ambulation in patients with MS, physicians should be keenly aware of its presentation, mechanism of action, and management in overdose