Reflecting the discrepancy between received and predicted outcomes, the reward prediction error (RPE) plays an important role in learning in a dynamic environment. A number of studies suggested that the feedback-related negativity (FRN) component of an event-related potential, known to be associated with unexpected outcomes, encodes RPEs. While FRN was clearly shown to be sensitive to the probability of outcomes, the effect of outcome magnitude on FRN remains to be further clarified. In studies on the neural underpinnings of reward anticipation and outcome evaluation, a monetary incentive delay (MID) task proved to be particularly useful. We investigated whether feedback-locked FRN and cue-locked dN200 responses recorded during an auditory MID task were sensitive to the probability and magnitude of outcomes. The cue-locked dN200 is associated with the update of information about the magnitude of prospective outcomes. Overall, we showed that feedback-locked FRN was modulated by both the magnitude and the probability of outcomes during an auditory version of MID task, whereas no such effect was found for cue-locked dN200. Furthermore, the cue-locked dN200, which is associated with the update of information about the magnitude of prospective outcomes, correlated with the standard feedback-locked FRN, which is associated with a negative RPE. These results further expand our knowledge on the interplay between the processing of predictive cues that forecast future outcomes and the subsequent revision of these predictions during outcome delivery.
Express saccades have very short latencies and are often considered a special population of saccadic eye movements. Recent evidence suggests that express saccade generation in humans increases with training, and that this training is independent of the actual saccade vector being trained. We assessed the time course of these training-induced increases in express saccade generation and how they differ between the nasal and temporal hemifields, and second whether they transfer from the trained to the untrained eye. We also measured the effects of training on saccade latencies more generally, and upon peak velocities. The training effect transferred between the nasal and temporal hemifields and between the trained and untrained eyes. More surprisingly, we found an asymmetric effect of training on express saccade proportions: Before training, express saccade proportions were higher for saccades made into the nasal hemifield but with training this reversed. This training-induced asymmetry was also observed in overall saccade latencies, showing how training can unmask nasal/temporal asymmetries in saccade latencies. Finally, we report for the first time that saccadic peak velocities increased with training, independently of changes in amplitude. Keywords Nasal temporal asymmetry · Express
Vibrotactile displays can compensate for the loss of sensory function of people with permanent or temporary deficiencies in vision, hearing, or balance, and can augment the immersive experience in virtual environments for entertainment, or professional training. This wide range of potential applications highlights the need for research on the basic psychophysics of mechanisms underlying human vibrotactile perception. One key consideration when designing tactile displays is determining the minimal possible spacing between tactile motors (tactors), by empirically assessing the maximal throughput of the skin, or, in other words, vibrotactile spatial acuity. Notably, such estimates may vary by tactor type. We assessed vibrotactile spatial acuity in the lower thoracic region for three different tactor types, each mounted in a 4×4 array with center-to-center inter-tactor distances of 25 mm, 20 mm, and 10 mm. Seventeen participants performed a relative three-alternative forcedchoice point localization task with successive tactor activation for both vertical and horizontal stimulus presentation. The results demonstrate that specific tactor characteristics (frequency, acceleration, contact area) significantly affect spatial acuity measurements, highlighting that the results of spatial acuity measurements may only apply to the specific tactors tested. Furthermore, our results reveal an anisotropy in vibrotactile perception, with higher spatial acuity for horizontal than for vertical stimulus presentation. The findings allow better understanding of vibrotactile spatial acuity and can be used for formulating guidelines for the design of tactile displays, such as regarding inter-tactor spacing, choice of tactor type, and direction of stimulus presentation.
A phenomenon termed negative priming is defined as an increase in reaction time and/or decrease in performance during instances in which current target stimuli are employed as distractor stimuli in the previous trial. A recent qualitative review on negative priming reported neural regions of interest underlined by activity within the right middle frontal gyrus and left middle temporal gyrus; however, these areas of interest have not been tested and supported by using coordinate-based, quantitative meta-analysis. We compiled functional magnetic resonance imaging studies that examined neural correlates of priming tasks using perceptual, conceptual and lexical primes. Effect-size signed differential mapping was used to perform a neuroimaging meta-analysis on the negative priming effect. Results from fourteen studies (245 participants; 85 foci) show concordance across studies in the right middle frontal gyrus and the left superior temporal gyrus, as suggested by the previous review; however, results also yielded concordance within the anterior cingulate cortex. Our data support the extant hypothesis and offer new insights into the neural mechanisms of the negative priming effect.
Most of the cerebral functions are asymmetrically represented in the two hemispheres. Moreover, dexterity and coordination of the distal segment of the dominant limbs depend on cortico-motor lateralization. In this study, we investigated whether postural control may be also considered a lateralized hemispheric brain function. To this aim, 15 young subjects were tested in standing position by measuring Center of Pressure (COP) shifts along the antero-posterior axis (COP-Y) during dynamic posturography before and after continuous Theta Burst Stimulation (cTBS) intervention applied to the dominant or non-dominant M1 hand area as well as to the vertex. We show that when subjects were expecting a forward platform translation, the COP-Y was positioned significantly backward or forward after dominant or non-dominant M1 stimulation, respectively. We postulate that cTBS applied on M1 may have disrupted the functional connectivity between intra- and inter-hemispheric areas implicated in the anticipatory control of postural stability. This study suggests a functional asymmetry between the two homologous primary motor areas, with the dominant hemisphere playing a critical role in the selection of the appropriate postural control strategy.
Introduction Attentional networks are sensitive to sleep deprivation and increased time awake. However, existing evidence is inconsistent and may be accounted for by differences in chronotype or time-of-day. We examined the effects of sustained wakefulness over a normal “socially constrained” day (following 18 h of sustained wakefulness), following a night of normal sleep, on visual attention as a function of chronotype. Methods Twenty-six good sleepers (mean age 25.58; SD 4.26; 54 % male) completed the Attention Network Test (ANT) at two time points (baseline at 8 am; following 18-h sustained wakefulness at 2 am). The ANT provided mean reaction times (RTs), error rates, and the efficiency of three attentional networks—alerting, orienting, and executive control/conflict. The Morningness–Eveningness Questionnaire measured chronotype. Results Mean RTs were longer at time 2 compared to time 1 for those with increasing eveningness; the opposite was true for morningness. However, those with increasing morningness exhibited longer RT and made more errors, on incongruent trials at time 2 relative to those with increasing eveningness. There were no significant main effects of time or chronotype (or interactions) on attentional network scores. Conclusion Sustained wakefulness produced differential effects on visual attention as a function of chronotype. Whilst overall our results point to an asynchrony effect, this effect was moderated by flanker type. Participants with increasing eveningness outperformed those with increasing morningness on incongruent trials at time 2. The preservation of executive control in evening-types following sustained wakefulness is likely driven by differences in circadian phase between chronotypes across the day.
The right temporoparietal junction (rTPJ) is a polysensory cortical area that plays a key role in perception and awareness. Neuroimaging evidence shows activation of rTPJ in intersensory and sensorimotor conflict situations, but it remains unclear whether this activity reflects detection or resolution of such conflicts. To address this question, we manipulated the relationship between touch and vision using the so-called mirror-box illusion. Participants' hands lay on either side of a mirror, which occluded their left hand and reflected their right hand, but created the illusion that they were looking directly at their left hand. The experimenter simultaneously touched either the middle (D3) or the ring finger (D4) of each hand. Participants judged, which finger was touched on their occluded left hand. The visual stimulus corresponding to the touch on the right hand was therefore either congruent (same finger as touch) or incongruent (different finger from touch) with the task-relevant touch on the left hand. Single-pulse transcranial magnetic stimulation (TMS) was delivered to the rTPJ immediately after touch. Accuracy in localizing the left touch was worse for D4 than for D3, particularly when visual stimulation was incongruent. However, following TMS, accuracy improved selectively for D4 in incongruent trials, suggesting that the effects of the conflicting visual information were reduced. These findings suggest a role of rTPJ in detecting, rather than resolving, intersensory conflict.