Introduction. Academic and commercial research teams are currently developing a new generation of devices that will interact with, incorporate, and/or emulate living nervous systems. Neural prostheses to restore hearing, mobility or sight will offer a wider range of function; robotic devices will become more effective with “neuromorphic” control systems; fundamentally new methods for processing information will be motivated by biological systems. Neural Engineering is the intellectual force behind these developments, supported by recent advances in cellular neurobiology, microfabrication and neural modeling. Based on decades of quantitative approaches to increase our understanding of neural systems, bioengineers are now beginning to design neural systems and neural interfaces. Neural engineers have new tools to control aspects of these systems such as guided axon growth and multielectrode arrays for stimulation and recording. In addition to potential applications attracting the attention of biotech and defense industries, these efforts in turn increase our understanding of natural neural systems.

Tactile sensing in the naked mole rat refers to the ability of this naturally blind species to respond to, and localize, stimuli that deflect facial vibrissae, but also an array of somatic vibrissae.

Cockroaches were observed with videographic methods as escape running was initiated, but with obstacles in the path of their run. The goal was to determine the repertoire of possible responses to obstacles and the sensory cues used to trigger the responses. Intact cockroaches collided with obstacles on only about 10% of trials. The most common collision avoidance strategy was simply to stop running prior to impact. However, occasionally animals moved vertically and climbed over the barrier, or turned and navigated an edge of the obstacle, or completely reversed run direction. The avoidance strategies chosen depended on the size and configuration of the obstacle. Tests for the use of vision in detecting obstacles showed that its role, if any, is small. However, all manipulations that altered the antennal system changed behavior in a way consistent with the hypothesis that antennal mechanosensation plays a major role in collision avoidance. For example, reducing antennal length, or severing the main antennal nerve without altering the length produced significant increases in the frequency of collisions. Tests with tethered insects showed that (1) the antennae are preferentially directed forward as animals run, and (2) nearly simultaneous contact with both antennae is required to make the cockroach stop. Our data indicate that running cockroaches employ strategies that set their sensorimotor systems in a mode of readiness to deal with obstacles and they suggest that sensory information about the presence and configuration of obstacles is used to make choices, at very short latencies, about how to respond to obstructions.

Submitted for the MAR10 Meeting of The American Physical Society Kinetics and physical properties of photolatent base catalyzed thiol-epoxy resins CHRISTOPHER COMER, OLIVIA MCNAIR, CHARLES HOYLE, DANIEL SAVIN, University of Southern Mississippi, School of Polymers and High Performance Materials — Typical epoxy resin systems based on multifunctional epoxides and multifunctional amines yield polymeric materials with unrivaled chemical resistance, toughness, and adhesion. Unfortunately amine cured epoxy resins must be mixed immediately prior to application because reactivity of the amine and epoxy is too high. Thiol-epoxy resins offer a less reactive alternative to these traditional epoxy resins and are catalyzed by the addition of a tertiary amine, such as DBN. In this study a combination of a diepoxide with multifunctional thiols based on mercaptoacetate (MA) and mercaptopropionate (MP) were polymerized using a photolatent base catalyst or DBN. The reactivity of the MA and MP based thiols were characterized using Real-time FT-IR. Mechanical and thermal properties of the resins were characterized using DMA, DSC, MTS, pencil hardness, and impact resistance. Thiol-cured epoxy systems have uniform network structures, as indicated by sharp tan δ peaks and distinct glass transition region shown by DMA and DSC respectively. Daniel Savin University of Southern Mississippi Date submitted: 19 Nov 2009 Electronic form version 1.4

Thiol-isocyanate-ene ternary networks with systematic variations (100/100/0, 100/80/20, 100/60/40, 100/40/60, 100/20/80, and 100/0/100) were prepared by sequential and simultaneous thiol-ene and thiol-isocyanate click reactions. The thiol-isocyanate coupling reaction was triggered thermally or photolytically to control the sequence with the thiol-ene photopolymerization. Triethyl amine (TEA) and 2,2-dimethoxy-2-phenyl acetophenone (DMPA) were used for the sequential thermally induced thiol-isocyanate coupling and photochemically initiated thiol-ene reaction, respectively. A thermally stable photolatent base catalyst (tributylamine.tetraphenylborate salt, TBA center dot HBPh4) capable of in situ generation of tributylamine by UV light was used with isopropylthioxanthone (ITX) for the simultaneous thiol-isocyanate/thiol-ene curing systems The kinetics of the hybrid networks investigated using real-time IR indicate that both thiol-isocyanate and thiol-ene reactions were quantitatively rapid and efficient (>90% of conversion in a matter of minutes and seconds, respectively) The T-g of the thiourethane/thiol-ene hybrid networks progressively increases (-5 to 35 degrees C by DSC) as a function of the thiourethane content due to the higher extent of hydrogen bonding, also resulting in enhanced mechanical properties. Highly uniform and dense network structures exhibiting narrow full width at half-maximum (similar to 10 degrees C) were obtained for both the sequential and the simultaneous thiol click reactions, resulting in identical thermal properties that are independent of the sequence of the curing processes

The organization of the antennal muscles, nerves, and motor neurons has been investigated in the cockroach, Periplaneta americana. Antennal movements have been observed by video analysis, muscle actions have been determined by dissection and direct mechanical testing, and the motor neurons innervating each muscle have been defined with a recently developed selective backfill method. A model of the antennomotor system of Periplaneta has thus been established and compared with that of crickets. Five muscles located within the head capsule insert on the most proximal antennal segment, the scape. By their action, they allow the scape to move in essentially any direction within the dorsoventral and anteroposterior planes. An additional pair of muscles, one dorsal and one ventral, are found within the scape. They insert on the pedicel and move the pedicel in the dorsal-ventral plane. These seven muscles are controlled by at least 17 motor neurons with somata located in the deutocerebrum. By their action, these motor neurons enable cockroaches to move the long flagellum of each antenna through a wide range of positions in the frontal space, medio-laterally, and also allow depression toward the substrate and elevation well above the level of the head. The antennal motor neurons have been classified into five morphological types based on soma and axon location. Each morphological type has been correlated with a particular pattern of muscle innervation and control. The neurites of all motor neurons are located along the medial aspect of the dorsal lobe of the deutocerebrum.

Even simple behaviors of vertebrates are typically generated by the concerted action of large numbers of brain cells. However, the mechanisms by which groups of neurons work together as functional populations to guide behavior remain largely unknown. One of the major model systems for exploring these mechanisms has been mammalian visuomotor behavior. We describe here experiments that establish a new model system for analyzing the sensory control of behavior by neuronal populations using a mammalian somatosensory response: orientation to touch cues in a rodent. We found that the CNS mechanisms used to direct these orientation responses to touch can be delineated from behavioral experiments. In this study we demonstrate that the superior colliculus, a component of the vertebrate midbrain most often thought of as a visual structure, is an essential component of the naked mole-rat's unique tactile orienting behavior. Furthermore, the information processing that underlies this behavior displays striking parallels with that used for visual orientation at anatomical and computational levels.

The eyes and visual capacity of the naked mole-rat, Heterocephalus glaber, a subterranean rodent, were evaluated using anatomical, biochemical, and functional assays, and compared to other rodents of similar body size (mouse and gerbil). The eye is small compared to mouse, yet possesses cornea, lens, and retina with typical mammalian organization. The optic nerve cross-sectional area and fiber density are ~10% and ~50% that of gerbil, respectively. Levels per unit retinal area of 11-cis and all-trans retinal, derivatives of vitamin A associated with the visual cycle, are comparable to mouse. The corneal electroretinogram (ERG) exhibits early and late negative components that scale with flash strength; raising the body temperature of this poikilothermic animal from 30°C (normal for H. glaber ) to 37°C (normal for mouse) revealed an ERG response with typically mammalian features, but greatly attenuated and with slower kinetics. Leaving the nest chamber was a behavior correlated with light onset displayed preferentially by breeding females. Optical models of five mole-rat eyes suggest reasonable, but variable, image formation at the retina, possibly related to age. Results are consistent with amorphous light detection, possibly useful for circadian entrainment or escape behavior in the event of tunnel breeches.

Cockroaches escape from predators by turning and then running. This behavior can be elicited when stimuli deflect one of the rostrally located and highly mobile antennae. We analyzed the behavior of cockroaches, under free-ranging conditions with videography or tethered in a motion tracking system, to determine (1) how antennal positional dynamics influence escape turning, and (2) if visual cues have any influence on antennal mediated escape. The spatial orientation of the long antennal flagellum at the time of tactile stimulation affected the direction of resultant escape turns. However, the sign of flagellar displacement caused by touch stimuli, whether it was deflected medially or laterally for example, did not affect the directionality of turns. Responsiveness to touch stimuli, and escape turn performance, were not altered by blocking vision. However, because cockroaches first orient an antenna toward stimuli entering the peripheral visual field, turn direction can be indirectly influenced by visual input. Finally, when vision was blocked, the run phase of escape responses displayed reduced average velocities and distances traveled. Our results suggest that tactile and visual influences are integrated with previously known wind-sensory mechanisms to achieve multisensory control of the full escape response.

Orientation guided by mechanosensory stimuli is a fundamental behavior that has been analyzed most effectively in simple systems, but has been difficult to assess in mammals. This study demonstrates that sparsely distributed sensory 'hairs' on the body of naked mole-rats provide an ideal detector array for the assessment of touch guided orienting behavior. Naked mole-rats are fully subterranean rodents that are functionally blind and lack fur. About 40 tactile hairs (resembling facial vibrissae) are found on each side of the body, and they are systematically organized in a grid-like pattern from head to tail. Deflection of a single body hair triggered a highly accurate orientation of the snout toward the point of stimulation, thus topographically organized motor behavior can be elicited from this sensory array. This orienting behavior is specific to the body hair system: touch of intervening skin evoked responses less reliably, and observed responses were not topographically organized. Orientation elicited from this array was accurate regardless of the head-to-body position at the time of hair stimulation indicating that the orienting motor score takes relative head position into account. The consistent pattern of these hairs coupled with robust orienting behavior indicates that this mammalian model provides an appropriately simple system for analyzing the neuronal basis of sensorimotor integration involved in tactile orienting behavior.

The superior colliculus (or optic tectum in nonmammals) plays a critical role in the visual system and is essential for integrating sensory inputs to guide eye and head movements. However, what is the role of the superior colliculus (SC) in species that depend almost exclusively on touch? In this study we examined the SC of the star-nosed mole, a subterranean mammal that, instead of using vision, explores its environment using its tactile star. The star acts like a mechanosensory eye with a central tactile fovea that is constantly shifted in a saccadic manner. Multiunit microelectrode recordings were used to determine the topography and receptive field organization of somatosensory inputs to the SC and to test for visual and auditory responses. Here we report an SC dominated by somatosensory inputs in which neurons in all layers responded to mechanosensory stimulation, forming a topographic representation of contralateral body dominated by the mechanosensory star. Receptive fields were large, and appendage representations overlapped, suggesting that the SC may use a distributed, population code to guide the saccadic movements of the mole's touch fovea. No auditory or visual responses were recorded from the SC, although neurons in the neighboring inferior colliculus responded to auditory stimuli. Layers IVb-VII were identified, and a layer superficial to IVb contained neurons that responded to somatosensory stimulation, suggesting that there are unique patterns of afferents in the star-nosed mole's SC.

Cockroaches (Periplaneta americana) orient their antennae toward moving objects based on visual cues. Presumably, this allows exploration of novel objects by the antennal flagellum. We used videographic and electrophysiological methods to determine if receptors on the flagellum are essential for triggering escape, or if they enable cockroaches to discriminate threatening from non-threatening objects that are encountered. When a flagellum was removed, and replaced with a plastic fiber, deflection of a "prosthetic flagellum" still activated the descending mechanosensory interneurons associated with escape and produced typical escape responses. However, escape was essentially eliminated by constraining the movement of the scape and pedicel at the antennal base. When cockroaches approached and briefly explored the surface of a spider or another cockroach with the flagellum, they produced escape significantly more often in response to subsequent controlled contact from a spider than from a cockroach. This discrimination did not depend on visual or wind-sensory input, but required flagellar palpation of the surface. The crucial sensory cues appear to involve texture rather than surface chemicals. These results indicate that cockroaches acquire basic information on stimulus identity during exploration of surfaces with flagellar receptors, but that basal receptors are triggers for escape behavior.

Studies of insect identified neurons over the past 25 years have provided some of the very best data on sensorimotor integration; tracing information flow from sensory to motor networks. General principles have emerged that have increased the sophistication with which we now understand both sensory processing and motor control. Two overarching themes have emerged from studies of identified sensory interneurons. First, within a species, there are profound differences in neuronal organization associated with both the sex and the social experience of the individual. Second, single neurons exhibit some surprisingly rich examples of computational sophistication in terms of (a) temporal dynamics (coding superimposed upon circadian and shorter-term rhythms), and also (b) what Kenneth Roeder called ‘neural parsimony’: that optimal information can be encoded, and complex acts of sensorimotor coordination can be mediated, by small ensembles of cells. Insect motor systems have proven to be relatively complex, and so studies of their organization typically have not yielded completely defined circuits as are known from some other invertebrates. However, several important findings have emerged. Analysis of neuronal oscillators for rhythmic behavior have delineated a profound influence of sensory feedback on interneuronal circuits: they are not only modulated by feedback, but may be substantially reconfigured. Additionally, insect motor circuits provide potent examples of neuronal restructuring during an organism's lifetime, as well as insights on how circuits have been modified across evolutionary time. Several areas where future advances seem likely to occur include: molecular genetic analyses, neuroecological syntheses, and neuroinformatics — the use of digital resources to organize databases with information on identified nerve cells and behavior.