A ratio code for vibrotactile pitch

Subjective impressions of pitch for 80 different sinusoidal vibrotactile stimuli delivered to the index finger were measured by free magnitude estimation in four subjects. In three of the subjects, pitch at a given frequency decreased as stimulus amplitude increased. The data of these subjects were well described by a model of pitch based on the relative levels of activation of the three major tactile channels. The main element in this model was a ratio of P channel activity to the sum of the activity levels of the P, NPI, and NPIII channels. Activity levels of the channels were estimated on the basis of the psychophysical literature, including a study of vibrotactile loudness using the same subjects and stimuli as those employed here. A fourth subject, whose pattern of loudness judgments had previously been shown to differ from those of the other subjects, did not conform to this pitch model: her data revealed significant increases in pitch with increases in amplitude, and appear to reflect an inability to combine signals across vibrotactile channels. Pitch changes resulting from vibrotactile adaptation were directionally consistent with our ratio model: pitch was slightly increased by adaptation to a 25 Hz stimulus, and slightly decreased by 200 Hz adaptation.     

种子重量与海拔的相关性分析：

种子重量与海拔的关系是植物生态学中重要而尚存争议的问题。本文对中国123科853种2879份野生植物种子的重量在海拔上的变化特点以及二者之间的相互关系进行了深入研究,结果显示：种子重量总体上与海拔呈负相关,种子重量级别多样性和生活型多样性随海拔上升呈阶梯状下降。但7级种子中,只有10。级种子的重量与海拔呈负相关;7种生活型中,只有灌木和匍匐草本的种子重量与海拔呈负相关;在种水平上,只有8．2％的物种种子重量与海拔存在相关性。本研究揭示了我国种子重量与海拔之间的复杂关系,以及遗传和环境对种子重量的影响,对植物育种、森林管理以及入侵植物的防治具有一定指导意义。     

Effect of vibration magnitude, vibration spectrum and muscle tension on apparent mass and cross axis transfer functions during whole-body vibration exposure

Twelve seated male subjects were exposed to 15 vibration conditions to investigate the nature and mechanisms of the non-linearity in biomechanical response. Subjects were exposed to three groups of stimuli: Group A comprised three repeats of random vertical vibration at 0.5, 1.0 and 1.5 m s⁻² r.m.s. with subjects sitting in a relaxed upright posture. Group B used the same vibration stimuli as Group A, but with subjects sitting in a ‘tense’ posture. Group C used vibration where the vibration spectrum was dominated by either low-frequency motion (2–7 Hz), high-frequency motion (7–20 Hz) or a 1.0 m s⁻² r.m.s. sinusoid at the frequency of the second peak in apparent mass (about 10–14 Hz) added to 0.5 m s⁻² r.m.s. random vibration. In the relaxed posture, frequencies of the primary peak in apparent mass decreased with increased vibration magnitude. In the tense posture, the extent of the non-linearity was reduced. For the low-frequency dominated stimulus, the primary peak frequency was lower than that for the high-frequency dominated stimulus indicating that the frequency of the primary peak in the apparent mass is dominated by the magnitude of the vibration encompassing the peak. Cross-axis transfer functions showed peaks of about 15–20% and 5% of the magnitudes of the peaks in the apparent mass for x- and y-direction transfer functions, respectively, in the relaxed posture. In the tense posture, cross-axis transfer functions reduced in magnitude with increased vibration, likely indicating a reduced fore-aft pitching of the body with increased tension, supporting the hypothesis that pitching contributes to the non-linearity in apparent mass.     

Digit ratio (2D:4D) and the spatial representation of magnitude

Digit ratio (as a putative indicator of prenatal androgen exposure) is related to a range of sexually dimorphic abilities, including spatial skills and mathematical ability. This study examined a phenomenon known as the SNARC effect (Spatial Numerical Association of Response Codes), which is taken as evidence of a mental representation of magnitude along a left-right-oriented number line, with low magnitudes associated with the left side of space, and high numbers with the right side of space. Participants made a parity judgement of numbers with responses made with a left key to odd numbers and a right key to even numbers. This was reversed for a second block of trials. Response times to numbers one to nine with both the right and left hand were calculated, and regression analyses conducted to analyse whether lower magnitudes were responded to faster with the left hand and higher magnitudes with the right hand. Participants with lower (more masculine) digit ratios on the right hand showed a stronger SNARC effect compared to participants with high digit ratios. This pattern of results was also found when the analyses were conducted separately for men and women. Results from left hand digit ratios indicated that only low digit ratio females showed a significant SNARC effect. These findings add to a growing literature on the relationship between digit ratio and cognitive abilities; in this case, simple cognitive representations that are accessed automatically rather than complex skills such as mental rotation or "mathematics" where a variety of solution strategies may be utilised.     

Monkey electrophysiological and human psychophysical responses to mutants of the sweet protein brazzein: delineating brazzein sweetness

Responses to brazzein, 25 brazzein mutants and two forms of monellin were studied in two types of experiments: electrophysiological recordings from chorda tympani S fibers of the rhesus monkey, Macaca mulatta, and psychophysical experiments. We found that different mutations at position 29 (changing Asp29 to Ala, Lys or Asn) made the molecule significantly sweeter than brazzein, while mutations at positions 30 or 33 (Lys30Asp or Arg33Ala) removed all sweetness. The same pattern occurred again at the beta-turn region, where Glu41Lys gave the highest sweetness score among the mutants tested, whereas a mutation two residues distant (Arg43Ala) abolished the sweetness. The effects of charge and side chain size were examined at two locations, namely positions 29 and 36. The findings indicate that charge is important for eliciting sweetness, whereas the length of the side-chain plays a lesser role. We also found that the N- and C-termini are important for the sweetness of brazzein. The close correlation (r = 0.78) between the results of the above two methods corroborates our hypothesis that S fibers convey sweet taste in primates.     

Discounting of sequences of delayed rewards of different amounts

The main purpose of this study was to determine whether the magnitude effect is present in cases where delayed sequences of rewards are discounted. The magnitude effect refers to the inverse relationship between the amount of a reward and the steepness of temporal discounting. This study was conducted with a computer program to estimate the indifference points, which served as indicators of the present subjective value of delayed sequences of small and large rewards. In the indifference point the subjective value of a single, immediate reward was equal to the subjective value of the delayed sequence (or to the value of a single delayed reward). As a control condition, we added an experimental task involving choices between single immediate and single delayed rewards. The experiment showed that the sequences of large rewards are discounted less steeply than are the sequences of small rewards. This finding suggests that the magnitude effect is present within the delayed sequences of rewards. In addition, when outcomes are relatively large, the results suggest that a single reward is discounted less steeply than the sequence of a total nominal value equal to this single reward. However, for relatively small rewards, the difference is not statistically significant. The less steep discounting of sequences of large rewards may explain the reward-bundling effect, which refers to less steep discounting of longer sequences than of shorter ones: longer sequences usually have greater overall nominal value. The present study was conducted on hypothetical rewards, and the results should be validated using real rewards.     

Differences between the tactile sensitivity on the anterior torso of normal individuals and those having suffered complete transection of the spinal cord

Using the method of limits and a magnitude estimation procedure, the sense of touch was examined at multiple sites on the anterior torso of normal subjects. Their performance was compared with the performance of individuals having experienced a functionally complete spinal cord transection more than 6 months prior to the tests. Near the insentient regions of the spinal cord-injured patients there was a zone wherein the threshold for light touch was elevated and variable. Within this same transition zone, estimates of the magnitude of a brushing stimulus increased as a linear function of distance from the border for approximately 12 cm away from insentient skin. Throughout the rest of the thorax, spinal cord-injured patients displayed touch thresholds 67% higher than normals and, at the same test sites, spinal cord-injured patients offered estimates of the intensity of the brushing stimulus that averaged 62% higher than normal subjects. The greater intensity of the sensations experienced by spinal cord-injured patients with even very weak stimuli and the smaller range within which they were able to scale stimulus intensity, produced a situation wherein the patients made frequent errors of judgement even on skin regions far from the body parts affected by the lesion. These observations support the hypothesis that spinal cord lesions interrupt tonic modulatory mechanisms having global influences on the sense of touch. This loss produces an elevation of the touch threshold and a reduction of the normal dynamic range of tactile sensory perception for all skin surfaces on the anterior torso.     

种子重量与海拔的相关性分析

种子重量与海拔的关系是植物生态学中重要而尚存争议的问题。本文对中国123科853种2879份野生植物种子的重量在海拔上的变化特点以及二者之间的相互关系进行了深入研究,结果显示：种子重量总体上与海拔呈负相关,种子重量级别多样性和生活型多样性随海拔上升呈阶梯状下降。但7级种子中,只有100级种子的重量与海拔呈负相关;7种生活型中,只有灌木和匍匐草本的种子重量与海拔呈负相关;在种水平上,只有82%的物种种子重量与海拔存在相关性。本研究揭示了我国种子重量与海拔之间的复杂关系,以及遗传和环境对种子重量的影响,对植物育种、森林管理以及入侵植物的防治具有一定指导意义。