Facilitation of neural responses to targets moving against optic flow

For the human observer, it can be difficult to follow the motion of small objects, especially when they move against background clutter. In contrast, insects efficiently do this, as evidenced by their ability to capture prey, pursue conspecifics, or defend territories, even in highly textured surrounds. We here recorded from target selective descending neurons (TSDNs), which likely subserve these impressive behaviors. To simulate the type of optic flow that would be generated by the pursuer’s own movements through the world, we used the motion of a perspective corrected sparse dot field. We show that hoverfly TSDN responses to target motion are suppressed when such optic flow moves syn-directional to the target. Indeed, neural responses are strongly suppressed when targets move over either translational sideslip or rotational yaw. More strikingly, we show that TSDNs are facilitated by optic flow moving counterdirectional to the target, if the target moves horizontally. Furthermore, we show that a small, frontal spatial window of optic flow is enough to fully facilitate or suppress TSDN responses to target motion. We argue that such TSDN response facilitation could be beneficial in modulating corrective turns during target pursuit.

Automatic inhibition of habitual response associated with a non-target object while performing goal-directed actions

This study is devoted to investigating mechanisms that inhibit habituated response associated with affordance of a non-target while executing action directed to a target. In four experiments, a paradigm was used that required a rapid left- or right-hand response according to the direction of the target arrow presented simultaneously or in close temporal proximity to a non-target whose handle position afforded grasping with the left or right hand. In general, responding was decelerated and more erroneous when the handle position was compatible with the responding hand. This effect of response inhibition was removed when the delay between the non-target offset and target onset was longer than 200 ms, and reversed into response facilitation when the target onset was delayed for 400–600 ms. The study suggests that processes that control withholding habitual response associated with affordance of a non-target utilise response inhibition mechanisms overlapping with those involved in behavioural control of the stop-signal task. This response inhibition is triggered automatically and directly by affordance of a non-target without preceding response excitation associated with this affordance cue.

To Run or Not to Run? Automatic Evaluations and Reflective Attitudes Toward Exercise

Using an evaluative priming procedure, this study tested whether automatic evaluations of running differ among groups based on their amount of exercise and whether they were runners or not. Ninety-five participants (26 ± 5.06 years; 46% female) were divided into five groups: an inactive group, active exercisers, highly active exercisers, active runners, and highly active runners. A priming effect score was calculated based on the concept of response facilitation or inhibition: the reaction is faster when the target and prime are valence congruent and becomes slower if they are incongruent. The highly active runner group differed significantly from the inactive group (p < .01) and from the active exerciser group (p < .05). Furthermore, reflective evaluations were measured via questionnaires. The results show that priming effect scores can detect automatic evaluations of running, and they differ not only because of the amounts of physical exercise but also because of their preferred type of exercise.

Please Empathize! Instructions to empathize strengthen response facilitation after pain observation

Recent research has shown that observing others in pain leads to a general facilitation of reaction times. The current study sheds further light on the relationship between pain observation and reaction time by exploring how bottom-up processes, in the form of perceived pain intensity, and top-down processes, in the form of explicit instructions to empathize, influence response facilitation after pain observation. Participants watched videos of a hand getting pierced by a needle or touched by a Q-tip. To manipulate bottom-up information, participants saw videos depicting either deep or shallow insertion of the needle. To investigate potential top-down modulation, half the participants were explicitly requested to empathize with the person in the video, while the other half were told to simply watch and attend to the video. Results from two experiments corroborate previous results showing response facilitation after pain observation. Critically, experiment 2 provides robust evidence that explicit instructions to empathize with a person in pain strengthen response facilitation. We discuss these results considering social cognitive neuroscience and experimental psychology studies of empathy and pain observation.

An Analysis of N2 Event-Related-Potential Correlates of Sequential and Response-Facilitation Effects in Cognitive Control

According to conflict-monitoring theory ( Botvinick, Braver, Barch, Carter, & Cohen, 2001 ), sequential adjustments in cognitive control indicate that encountering information-processing conflict engages cognitive-control mechanisms. With 20 participants in an event-related-potential (ERP) experiment, we found significant congruence-sequence effects (CSEs) for behavioral measures and for N2 amplitude, a negative-going ERP component established in previous work to be related to cognitive control. We also found an interaction between the Stroop-trajectory manipulation and a response-compatibility manipulation for behavioral measures and, to a lesser extent, for N2 amplitude, such that the Stroop-trajectory congruence effect was larger on response-compatible than on response-incompatible trials. This study is the first to identify N2 amplitude as a neural correlate of the CSE in a confound-minimized task. Accordingly, these results found N2 amplitude to be associated with adjustments in cognitive control as a function of sequential and response-facilitation effects while also validating the Stroop-trajectory task as a confound-minimized means of assessing neural correlates of CSEs.

Binocular summation in marmoset lateral geniculate nucleus

In primates and carnivores, the main laminae of the dorsal lateral geniculate nucleus (LGN) receive monocular excitatory input in an eye-alternating fashion. There is also evidence that nondominant eye stimulation can reduce responses to dominant eye stimulation and that a subset of LGN cells in the koniocellular (K) layers receives convergent binocular excitatory input from both eyes. What is not known is how the two eye inputs summate in the K layers of LGN. Here, we aimed to answer this question by making extracellular array electrode recordings targeted to K layers in the marmoset (Callithrix jacchus) LGN, as visual stimuli (flashed 200 ms temporal square-wave pulses or drifting gratings) were presented to each eye independently or to both eyes simultaneously. We found that when the flashed stimulus was presented to both eyes, compared to the dominant eye, the peak firing rate of most cells (61%, 14/23) was reduced. The remainder showed response facilitation (17%) or partial summation (22%). A greater degree of facilitation was seen when the total number of spikes across the stimulus time window (200 ms) rather than peak firing rates was measured. A similar pattern of results was seen for contrast-varying gratings and for small numbers of parvocellular (n = 12) and magnocellular (n = 3) cells recorded. Our findings show that binocular summation in the marmoset LGN is weak and predominantly sublinear in nature.

Biasing Actions by Incentive Valence in an Approach/Avoidance Task

The present study investigates interactions between incentive valence and action, which mirror well-known valence-action biases in the emotional domain. In three joystick experiments, incentive valence (win/loss) and action type (approach/avoid) were signaled by distinct orthogonal stimulus features. By combining several design aspects, i.e., the use of bi-directional joystick movements, the inclusion of no-incentive baseline trials, and cue-locked versus target-locked valence and action signals, we tried to bridge between paradigms used in the emotional and motivational domain, and to understand previous, partly inconsistent results. In the first task variant (Experiment 1), we observed performance benefits for compatible mappings (win-approach; loss-avoid) relative to incompatible ones (loss-approach; win-avoid) when valence and action signals were target-locked, consistent with a fairly automatic response activation that can benefit or impair task performance. In contrast, cue-locked valence signals led to response facilitation (relative to a no-incentive baseline) more or less independent of actual valence (win/loss) and action type (approach/avoid), which is reminiscent of general facilitation effects of incentive cues across diverse cognitive tasks. Slight design variations did not change this main result pattern, indicating that it was neither driven by the close proximity between target and performance feedback (Experiment 2), nor by mere temporal coincidence of valence and action signals (Experiment 3), but rather by differences between preparatory (cued) and immediate (non-cued) effects of incentive valence. The present study provides novel insights regarding the nature of valence-action biases in the motivational domain and helps to integrate previous, partly inconsistent findings across domains.

Observing painful events in others leads to a temporally extended general response facilitation in the self

Excitability in the motor cortex is modulated when we observe other people receiving a painful stimulus (Avenanti et al., 2005). However, the task dependency of this modulation is not well understood, as different paradigms have yielded seemingly different results. Previous neurophysiological work employing transcranial magnetic stimulation (TMS) suggests that watching another person’s hand being pierced by a needle leads to a muscle specific inhibition, assessed via motor evoked potentials. Results from previous behavioural studies suggest that overt behavioural responses are facilitated due to pain observation (Morrison et al., 2007a; 2007b). There are several paradigmatic differences both between typical TMS studies and behavioural studies, and within behavioural studies themselves, that limit our overall understanding of how pain observation affects the motor system. In the current study, we combine elements of typical TMS experimental designs in a behavioural assessment of how pain observation affects overt behavioural responding. Specifically, we examined the muscle specificity, timing, and direction of modulation of motor responses due to pain observation. To assess muscle specificity, we employed pain and non-pain videos from previous TMS studies in a Go/No-Go task in which participants responded by either pressing a key with their index finger or with their foot. To assess timing, we examined response times for Go signals presented at 0ms or 500ms after the video. Results indicate that observation of another individual receiving a painful stimulus leads to a non-effector specific, temporally extended response facilitation (e.g., finger and foot facilitation present at 0ms and 500ms delays), compared to observation of non-pain videos. This behavioural facilitation effect differs from the typical motor inhibition seen in TMS studies, and we argue that the effects of pain observation on the motor system are state-dependent, with different states induced via task instructions. We discuss our results in light of previous work on motor responses to pain observation.