Magnitude Estimation of Contact Force When Objects with Different Shapes Are Applied Passively to the Fingerpad

Stimuli with spherically curved surfaces were presented passively to the fingerpads of human subjects. There were 28 stimuli, consisting of all combinations of 4 different curvatures and 7 different contact forces; these were presented in random order. Subjects scaled their perceived magnitude of the contact force using magnitude estimation. Perceived force increased markedly with an increase in experimentally applied contact force. An increase in curvature resulted in a slight increase in perceived contact force. Thus, when humans are passively presented with objects changing in both shape and contact force, they are able to extract information about the force. Because of the passive nature of the task, all such information must be conveyed to the brain by the cutaneous mechanoreceptors.     

Sensory biology of Phalangida harvestmen (Arachnida,Opiliones): a review,with new morphological data on 18 species

Phalangida includes three of the four suborders of Opiliones (Arachnida): Eupnoi, Dyspnoi and Laniatores. We review the literature on the sensory structures and capabilities of Phalangida, provide new morphological data for 18 species and discuss the 11 sensory structures that have been described in the group. Based on the published data encompassing both behaviour and morphology, three conclusions are apparent: (1) species of Phalangida appear to have limited abilities to detect stimuli at a distance; (2) close range olfaction probably helps to find foods with strong odours, but (3) they appear to be highly dependent on contact chemoreception to detect live prey, predators and mates. We also highlight the fact that legs I in the three suborders and pedipalps in Dyspnoi and Eupnoi are very important sensory appendages, thus legs II should not be called the ‘sensory appendages’ of harvestmen. In conclusion, we highlight the fact that the sensory capabilities, diet, prey capturing and handling ability, and foraging behaviour of species of Phalangida seem to be different from those of most other arachnids. Finally, we suggest future directions for studies in the field of the sensory system of the group.     

Behavioural responses of juvenile cuttlefish (Sepia officinalis) to local water movements

Physiological studies have shown that the epidermal head and arm lines in cephalopods are a mechanoreceptive system that is similar to the fish and amphibian lateral lines (Budelmann BU, Bleckmann H. 1988. A lateral line analogue in cephalopods: Water waves generate microphonic potentials in the epidermal head lines of Sepia officinalis and Lolliguncula brevis. J. Comp. Physiol. A 164:1-5.); however, the biological significance of the epidermal lines remains unclear. To test whether cuttlefish show behavioural responses to local water movements, juvenile Sepia officinalis were exposed to local sinusoidal water movements of different frequencies (0.01-1000 Hz) produced by a vibrating sphere. Five behavioural responses were recorded: body pattern changing, moving, burrowing, orienting, and swimming. Cuttlefish responded to a wide range of frequencies (20-600 Hz), but not to all of the frequencies tested within that range. No habituation to repeated stimuli was seen. Results indicate that cuttlefish can detect local water movements (most likely with the epidermal head and arm lines) and are able to integrate that information into behavioural responses.     

Particle and prey detection by mechanoreceptive copepods: a mathematical analysis

When particles move through fluids, they produce far-field pressure differences and near-field fluid deformations. Here we evaluate if a copepod, relying on mechanoreceptive antennulary setal hairs, can detect pressure changes caused by a variety of signal sources. We first provide a correction of the copepod mechanoreception model of Legier-Visser et al. (1986), showing how an object above a minimum size should be detectable. The pressure change P created by an object of this minimum size was 385 dynes/cm², based on biomechanical relationships for a rigid seta bending with respect to the exoskeletal body and using the neurophysiological detection threshold of a 10 nm bend of the sensory seta (Yen et al., 1992). The P for: a 3 m particle = 0.01 dynes/cm², a 50 m particle = 0.16 dynes/cm², an escaping nauplius = 78 dynes/cm², a revolving prey = 10^–5 dynes/cm², a 1 mm copepod escaping at 1 m/s at a distance of 1 mm from the mechanoreceptive sensory hairs of its captor = 312 dynes/cm². Only the copepod escaping at high-speed close to the captor would create a pressure difference that could elicit a response. At this point, we conclude that pressure differences are rarely of a magnitude that is perceptible and that additional information must be derived for a copepod to detect prey. Other signals include fluid deformations as well as other types of stimuli (odor, shadows). Like most organisms, a copepod will rely on all sensory modalities to find food, avoid predators, and track mates, assuring their survival in the aquatic environment. It also is possible that the biomechanical model is insufficient for estimating pressure differences causing the cuticular deformation or that further analysis is necessary to improve our certainty of the sensitivity of the copepod seta.     

The senses of sea anemones: responses of the SS1 nerve net to chemical and mechanical stimuli

The ectodermal slow system (SS1) is one of 3 separate nerve nets in sea anemones. SS1 sensory responses coordinate swimming in Stomphia coccinea (escape response) and expansion to dissolved food substances in Urticina felina (pre-feeding response). Here we have studied Actinia equina, Anemonia viridis, and Anthopleura ballii. Although these anemones can escape from nudibranch predators, the SS1 response to attack by Aeolidia papillosa is probably evoked mechanically rather than chemically (cf. Stomphia). Multiple SS1 pulses to mechanical stimulation are described for the first time. Previous work has shown that in the pre-feeding response of Urticina the SS1 is excited by betaine; in Actinia however, the excitant is proline. The anemones studied can utilize the SS1 in 2 different behavioural responses (escape and pre-feeding/feeding) because the different receptors involved respond at different frequencies (at around 0.6 Hz in escape and 0.2 Hz in pre-feeding).     

Spider senses - technical perfection and biology

This essay deals with sensory biology in a broad sense. It takes mechanosensory systems of spiders to illustrate a few basic issues. Particular attention is given to two aspects. 1. There is a remarkable “ingenuity” in the uptake and transformation of the adequate stimuli way out in the sensory periphery, which is reflected by an intimate relationship between the physical properties of the stimuli and the characteristics of the structures receiving and transforming them. We need to understand the details of this relationship in order to understand the relationship of an organism to its environment. 2. Sensory systems represent interfaces between the environment and behavior. As highly selective filters they have not evolved to provide abstract knowledge but to guide a particular behavior. The signals sent to the central nervous system are meaningful only in regard to their behavioral significance. – Some details of stimulus transformation in biological strain gauges (slit sensilla), airflow detectors (trichobothria) and touch receptors (tactile hairs) are described. Some of the refinement in the periphery is then meshed with the behavior of the whole organism. In this way the value shall be underlined of trying to understand reductionist details as building blocks of the complexity which enables an organism to behave in its own particular way in its species specific environment.     

Barrels XXIX: Barrels go Hollywood

Barrels XXIX brought together researchers focusing on the rodent barrel cortex and associated systems. The meeting revolved around three themes: thalamocortical interactions in motor control, touch in rodent, monkey, and humans, and the nature of the multisensory computations the brain makes. Over two days these topics were covered as well as many more presentations that focused on the physiology, behavior, and development of the rodent whisker-to-barrel cortex system.     

The role of sense organs in the feeding behaviour of juvenile sole and plaice

An infra-red video recording system was used to observe and compare the feeding activity of juvenile sole and plaice. Experiments in light or dark and chemical ablation of the neuromasts with streptomycin sulphate allowed all or a limited set of senses to be used by the fishes. Both species were able to feed on dead prey when only chemical stimuli were available. Plaice showed a greater dependence on vision for feeding but sole relied principally on chemoreception and mechanoreception. When any one sense was removed plaice became less active whereas sole became more active.     

Texture preferences of ascidian tadpole larvae during settlement

Ascidian tadpole larvae settle on hard surfaces and undergo metamorphosis into sessile adults. To test whether tadpoles evaluate the texture of surfaces they settle upon, we presented tadpoles with surfaces that were divided into halves; each half had one of four different textures: smooth, fine sandpaper, coarse sandpaper, and sandblasted. In all cases, twice as many individuals settled on one side over the other, but this was not consistently the smooth side or the rough side. More tadpoles settled on a smooth surface than one scoured by sandpaper, but more tadpoles settled on a sandblasted surface than smooth one. This indicates tadpoles are capable of finer tactile discrimination than merely detecting a hard surface, and supports the hypothesis that ascidian tadpoles have mechanoreceptive sensory neurons.     

Cytoarchitecture of the Ferret Suprasylvian Gyrus Correlated with Areas Containing Multiunit Responses Elicited by Stimulation of the Face

The cytoarchitecture was studied in a segment of the ferret suprasylvian gyrus containing at least two and possibly four somesthetic representations of the face that were observed in the primary somatosensory cortex. These representations were restricted to the crown of the gyrus and were surrounded by somesthetically unresponsive cortex that extended down both sides to the base of adjacent sulci. Numerous cytoarchitectonic subdivisions were found on a qualitative basis, and were confirmed quantitatively by cluster analyses and relevant statistical tests of 10 prominent features from layers III, IV, and V. Four distinct cytoarchitectonic subdivisions, each with a well-developed and homogeneous granular layer IV, were found distributed from anterior to posterior along the crown of the gyrus at sites corresponding to the locations of the four facial representations. The surrounding unresponsive cortex had a fragmented cytoarchitecture, especially along the medial bank and base of the coronal sulcus. This unresponsive cortex separated the facial representations from the body representations, which were located on the adjacent posterior cruciate gyrus. Most of the unresponsive subdivisions had a heterogeneous or agranular layer IV and fairly well-developed sublamination in layer III, which may be indicative of extensive corticocortical connections. One set of unresponsive subdivisions had comparable cytoarchitectures that directly bordered the facial representations. Another set of unresponsive subdivisions with comparable architectures occupied most of the lateral bank of the gyrus. The implications of multiple representations and cytoarchitectonic fragmentation of the ferret primary somatosensory cortex are discussed in relation to the organization of the primary somatosensory cortex in other species.