Hand-Foot Coupling: An Advantage for Crossed Legs

It is difficult to perform distinct, simultaneous motor actions with the ipsilateral hand and foot; for example, clockwise circles with the right hand and counter-clockwise circles with the right foot. By chance, we discovered that this hand-foot coupling task is easier when seated with legs crossed. We consider various explanations. First, that there are reduced demands on the contralateral hemisphere when the motor programme of the right foot is executed on the left side of the body. Second, that the legs-crossed scenario is easier because movements are symmetrical with respect to body midline. By considering related motor actions, we conclude that neither of these explanations provides a full account. Thus, we suggest a third explanation, which is that coupling effects are reduced by virtue of increased postural stability and reduced anticipatory postural adjustments.

Description and DNA barcoding of Lycenchelys lenzeni, a new species of eelpout (Perciformes: Zoarcidae) from the deep sea off the Kuril Archipelago

A new species of eelpout genus Lycenchelys Gill, 1884 is described based on seven specimens caught at a depth of about 2350 m in the Bussol Strait, southwest of the Kuril Island Simushir. The species differs from its congeners in the following combination of characters: vertebrae 26–28 + 100–102 = 126–130; interorbital and occipital pores absent; postorbital pores 3–4; suborbital pores 7 (rarely 6); preoperculomandibular pores 4 + 4; gill rakers 11–16; dorsal fin rays 118–122; anal fin rays 105–108; pelvic fin rays 2; middle and lower ray tips of pectoral fin very slightly exserted; lateral line double with mediolateral and ventral branches; pyloric caeca not developed. The new species is morphologically most similar to Lycenchelys micropora and Lycenchelys jordani, which differ from the new species in having three pelvic-fin rays (vs. two pelvic-fin rays in the new species). L. micropora has the pectoral-fin origin below body midline, whereas the new species has the pectoral-fin origin at body midline. Middle and lower ray tips of pectoral fin are very slightly exserted in L. lenzeni sp. nov., whereas they are well exserted in L. jordani and L. micropora. Mitochondrial COI sequences were analyzed from four paratype specimens and all show the same haplotype sequence. The DNA barcodes allowed discrimination of L. lenzeni sp. nov. from other species of Lycenchelys where sequence data were available. The nearest match with already published sequences was Lycenchelys antarctica, with a sequence similarity of 98.25%, followed by Lycenchelys aratrirostris (sequence similarities 97.95–97.96%) and L. jordani (sequence similarity of 97.81%).

Effects of Line Separation and Exploration on the Visual and Haptic Detection of Symmetry and Repetition

Detection of regularities (e.g., symmetry, repetition) can be used to investigate object and shape perception. Symmetry and nearby lines may both signal that one object is present, so moving lines apart may disrupt symmetry detection, while repetition may signal that multiple objects are present. Participants discriminated symmetrical/irregular and repeated/irregular pairs of lines. For vision, as predicted, increased line separation disrupted symmetry detection more than repetition detection. For haptics, symmetry and repetition detection were similarly disrupted by increased line separation; also, symmetry was easier to detect than repetition for one-handed exploration and for body midline-aligned stimuli, whereas symmetry was harder to detect than repetition with two-handed exploration of stimuli oriented across the body. These effects of exploration and stimulus orientation show the influence of modality-specific processing rather than properties of the external world on regularity detection. These processes may, in turn, provide insights into the nature of objectness in vision and in touch.

Watching touch increases people’s alertness to tactile stimuli presented on the body surface

Several studies have shown that watching one’s own body part improves tactile acuity and discrimination abilities for stimuli presented on that location. In a series of experiments we asked the participants to localize tactile stimuli presented on the left or right arm. In Experiment 1 the participants were not allowed to watch their body, but they could see another person’s left arm via a LCD display. This arm could be touched or not during the presentation of the stimuli. We found that when the participants saw the arm on the screen being touched, their responses to the tactile stimuli presented on the left and on the right arm were faster and more accurate than when the arm on the screen was approached but not touched. Critically, we did not find any illusion of ownership related to the hand seen on the screen. In Experiments 2 and 3 we varied the position of the screen with respect to the participant’s body midline and the image displayed on it (an arm or an object of equal size). The participants gave faster responses when an object rather than a hand was displayed on the screen. Moreover, the responses were slower when the hand on the screen was placed in front of the participants, as compared to any other position. Taken together the results of our experiments would seem to suggest that watching touch activates multisensory mechanisms responsible for alerting people regarding the possible presence of tactile stimuli on the body surface.

The Effect of Bilateral Isometric Forces in Different Directions on Motor Cortical Function in Humans

The activity in the primary motor cortex (M1) reflects the direction of movements, but little is known about physiological changes in the M1 during generation of bilateral isometric forces in different directions. Here, we used transcranial magnetic stimulation to examine motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), and interhemispheric inhibition (IHI) in the left first dorsal interosseous (FDI) during isometric index finger abduction while the right index finger remained at rest or performed isometric forces in different directions (abduction or adduction) and in different postures (prone and supine). Left FDI MEPs were suppressed during bilateral compared with unilateral forces, with a stronger suppression when the right index finger force was exerted in the adduction direction regardless of hand posture. IHI targeting the left FDI increased during bilateral compared with unilateral forces and this increase was stronger during right index finger adduction despite the posture of the right hand. SICI decreased to a similar extent during both bilateral forces in both hand postures. Thus generation of index finger isometric forces away from the body midline (adduction direction), regardless of the muscle engaged in the task, down-regulates corticospinal output in the contralateral active hand to a greater extent than forces exerted toward the body midline (abduction direction). Transcallosal inhibition, but not GABAergic intracortical circuits, was modulated by the direction of the force. These findings suggest that during generation of bimanual isometric forces the M1 is driven by “extrinsic” parameters related to the hand action.