The Effect of Electrical Stimulation–Induced Pain on Time Perception and Relationships to Pain-Related Emotional and Cognitive Factors: A Temporal Bisection Task and Questionnaire–Based Study

Pain has not only sensory, but also emotional and cognitive, components. Some studies have explored the effect of pain on time perception, but the results remain controversial. Whether individual pain-related emotional and cognitive factors play roles in this process should also be explored. In this study, we investigated the effect of electrical stimulation–induced pain on interval timing using a temporal bisection task. During each task session, subjects received one of five types of stimulation randomly: no stimulus and 100 and 300 ms of non-painful and painful stimulation. Pain-related emotional and cognitive factors were measured using a series of questionnaires. The proportion of “long” judgments of a 1,200-ms visual stimulus duration was significantly smaller with 300 ms painful stimulation than with no stimulus (P < 0.0001) and 100 ms (P < 0.0001) and 300 ms (P = 0.021) non-painful stimulation. The point of subjective equality (PSE) did not differ among sessions, but the average Weber fraction (WF) was higher for painful sessions than for no-stimulus session (P = 0.022). The pain fear score correlated positively with the PSE under 100 ms non-painful (P = 0.031) and painful (P = 0.002) and 300 ms painful (P = 0.006) stimulation. Pain catastrophizing and pain anxiety scores correlated significantly with the WF under no stimulus (P = 0.005) and 100 ms non-painful stimulation (P = 0.027), respectively. These results suggest that electrical stimulation–induced pain affects temporal sensitivity, and that pain-related emotional and cognitive factors are associated with the processing of time perception.

The evolution of quantitative sensitivity

The ability to represent approximate quantities appears to be phylogenetically widespread, but the selective pressures and proximate mechanisms favouring this ability remain unknown. We analysed quantity discrimination data from 672 subjects across 33 bird and mammal species, using a novel Bayesian model that combined phylogenetic regression with a model of number psychophysics and random effect components. This allowed us to combine data from 49 studies and calculate the Weber fraction (a measure of quantity representation precision) for each species. We then examined which cognitive, socioecological and biological factors were related to variance in Weber fraction. We found contributions of phylogeny to quantity discrimination performance across taxa. Of the neural, socioecological and general cognitive factors we tested, cortical neuron density and domain-general cognition were the strongest predictors of Weber fraction, controlling for phylogeny. Our study is a new demonstration of evolutionary constraints on cognition, as well as of a relation between species-specific neuron density and a particular cognitive ability. This article is part of the theme issue ‘Systems neuroscience through the lens of evolutionary theory’.

Formalin-induced pain prolongs sub- to supra-second time estimation in rats

Background Temporal estimation can be influenced by pain, which is a complex psychological and physiological phenomenon. However, the time range in which perception is most sensitive to pain remains unclear. Methods In the present study, we explored the effects of acute inflammatory pain on time perception in the sub- to supra-second (0.6–2.4-s) and supra-second (2–8-s) ranges in rats. Plantar formalin injection was used to induce acute inflammatory pain, and a temporal bisection task was used to measure time perception. Task test sessions were held for five consecutive days (one per day): the day before injection (baseline), immediately after injection, and the three post-injection days. The point of subjective equality (PSE, which reflects the subjective duration) and Weber fraction (which reflects temporal sensitivity) were calculated and analysed. Results In the 0.6–2.4-s range, the PSE was significantly lower, indicating prolonged subjective duration, in the formalin group relative to the saline group (p = 0.049) immediately after injection. Formalin-induced pain also tended to lengthened time perception in the 0.6–2.4-s range on post-injection days 2 (p = 0.06) and 3 (p = 0.054). In the 2–8-s range, formalin injection did not affect the PSE or Weber fraction. Conclusions The enhanced effect of pain on temporal perception in the sub- to supra-second range is observed in this study and this effect is attenuated with the prolongation of estimated time, even in rats.

Frequency shapes the quality of tactile percepts evoked through electrical stimulation of the nerves

The quality of tactile percepts evoked by skin vibrations depends on the frequency of stimulation: as frequency increases, the vibrotactile “pitch” increases. In the present study, we assessed the degree to which the quality of tactile percepts evoked via electrical stimulation of the somatosensory nerves is shaped by the frequency of the pulse train (PF). Participants with chronically-implanted peripheral nerve interfaces rated the quality of electrical pulse trains that varied in both PF and pulse width (PW) along a single continuum and also described the subjective quality of the sensory experience using perceptual descriptors. We found that increases in PF led to systematic increases in perceived frequency independent of PW, up to about 50 Hz, at which point perceived frequency leveled off or decreased. PF discrimination matched its vibrotactile counterpart, yielding a Weber fraction of ∼0.2 at low frequencies, but discrimination performance was abolished above 50 Hz. Finally, we found that PF systematically shaped quality as characterized by verbal descriptors at low but not high frequencies. Furthermore, even when probed in this complex, multi-dimensional space defined by descriptors, PF modulated tactile quality along a single perceptual continuum. In conclusion, we show that quality can be shaped by imposing temporal patterns on a fixed neural population, highlighting the importance of spike timing in the peripheral nerve. However, this temporal patterning can only be resolved up to about 50 Hz when stimulation is applied to populations of tactile nerve fibers.

Does subitizing require attention? A systematic review and meta-analysis

Whether enumeration of small number of objects requires attention remains controversial. Although most recent studies argue for a role of attention in subitizing, these studies include varied stimuli and different methods of manipulating attention. It is unclear if the observed attention effects in different studies are real effects. It is also unclear whether there is publication bias in these studies. To answer this question, a systematic review and meta-analysis was performed to evaluate the attention effects on enumeration of small numbers. A total of 14 studies (22 experiments, 35 comparisons) were included in a meta-analysis to compare the attention effects on subitizing. Results from the meta-analysis suggest that a manipulation of attention can evidently modulate the behavioural performance in the subitizing range (response time, accuracy and Weber fraction). These findings were consistently observed in various experimental designs and different stimuli (p < .010; p < .001; p < .001; respectively), suggesting attention does play a role in subitizing. A new model was proposed to explain the mechanism of subitizing and enumeration. Findings in this study may contribute to the understanding of “number module” in brain and contribute to models of numerical cognition in education. However, a publication bias was observed in this study, suggesting the observed effects might not be very accurate. To better estimate the effect of attention manipulations in the subitizing range, studies with larger samples, or future meta-analyses including unpublished outcomes and unpublished studies may be required.

Comparative Statistical Analysis of Pre-Existing Non-Symbolic Cognitive Math Models as a Predictor of Math Acuity in Children

Approximate Number System (ANS) acuity has been the underlying basis of mathematical magnitude measure in developing children. The early number learning in a child by means of numerosity representation is said to be best estimated by an ANS based model. ANS models are majorly specific to cases where numbers are represented by non-digits and are therefore non-symbolic (dot representations). Prior research also suggests that ANS acuity models could be used to give an estimate of an accuracy of a child in a non-symbolic math task. Common measures of ANS acuity are based on weber fraction based accuracy performance and some others are based on numerical distance effect and reaction time. However though, very few studies have amalgamated reaction time and weber fraction models and compared them at an individualistic level using actual data collected over participants. In this research study, we effectively try to understand how factors like weber fraction, ratio, magnitude of numbers might affect the performance of a participant in a non-symbolic number comparison task. We also seek for any sort established relationship between numerical distance and reaction time and how that might be a predictor of good/bad performance. We carry out statistical analysis on both of these models (individually and combined) using data obtained from an online math task and thereby deduce which model could be a better predictor of a child’s math acuity.

Psychophysics Behavior of Human Tactile Mechanism to Discriminate Extremely Thin Copper Foils.

In this study, our objective is to analyze human tactile mechanism behavior in recognizing extremely thin foils using the psychophysics method. Seven pairs of copper foils ranging in thickness from 20 ~ 150 μm were used in the experiment. We applied the method of constant stimuli to define the difference threshold between the materials. In order to increase the detection rate, contact between human tactile function and the metal foils was maintained. As a result, the Weber fraction c consistently reduces as thickness increases. However, the slope decrement is steep compared to previous experimentation (using stainless steel as base). We also validated the behavior of the undetected regions up to 150-μm thicknesses. This achievement was quite significant considering the higher thickness test ratio. In future, further comparison shall be made using different material type.

Calculation Efficiencies for Mean Numerosity

Relative numerosity is traditionally studied using texture pairs. Observers must decide which member of each pair has the greater total number of texture elements. In the present experiment, textures were segregated into nonoverlapping “sectors” containing between zero and four elements, and our observers were asked to select the texture containing the greater average number of texture elements (per sector). If observers were more sensitive to total numerosity than average numerosity, their performance (quantified by the just-noticeable Weber fraction) should have been better when the two textures occupied the same number of sectors than when they occupied unequal numbers of sectors. However, we recorded Weber fractions between 11% and 13% for all observers in all conditions. This performance was comparable with an otherwise-ideal observer whose decisions were based on between three and five sectors in each texture. We conjecture that traditional numerosity discriminations are based on similarly small numbers of element clusters.

The Relationship Between Approximate Number System and Mathematics Competency in Indonesian Primary School Children

The purpose of this study is to investigate the relationship between Approximate Number System (ANS), a cognitive system which represents and estimates the cardinality of a set, and mathematics competency of primary school children. Many findings on ANS and its relations with mathematics competency showed inconsistency. This research is the first of its kind in Indonesia. 318 fourth and fifth-grade primary school students were instructed to perform non-symbolic (dots) comparison task to measure their Weber fraction (w), accuracy (percentage correct), and response time (ms) which are the measurement for ANS acuity. Mathematics competencies of the students were taken from school’s report card and the data were standardized for each school separately. Correlation and regression linear analysis were conducted to find the relationship between ANS acuity and mathematics’ competency. Analysis showed there was a weak but significant (p < 0.05) correlation between two measurements of ANS acuity, namely the Weber fraction and accuracy, with mathematics competency, but not response time (p > 0.05). Further analysis with linear regression showed there was no relationship between the two variables and mathematics score, which disproves this correlation. This study shows that there is no relationship between children’s ANS acuity and mathematics competency. Intrinsic factors such as children’s attention, engagement, and motivation, also methodological aspect needed further consideration. Future studies are needed to investigate the methodological aspect related to the measurement of ANS and mathematics’ competency as there is no ‘gold standard’ yet to measure ANS.