6D dynamic tractography visualizes the effective connectivity supporting specific linguistic stages in the developing brain

During a verbal conversation, as individuals listen and respond, the human brain moves through a series of complex linguistic processing stages: decoding of speech sounds, semantic comprehension, retrieval of semantically coherent words, and finally, overt production of speech outputs. Each process is thought to be supported by a cortical network consisting of local and long-range connections bridging between major cortical areas. Both temporal and extratemporal lobe regions are suggested to have functional compartments responsible for distinct language domains, including the perception and production of phonological and semantic components. This study provides quantitative evidence of how directly connected, inter-lobar neocortical networks support distinct linguistic stages of linguistic processing across brain development. A novel six-dimensional tractography animation technique was used to intuitively visualize the strength and temporal dynamics of direct inter-lobar effective connectivity between cortical areas activated during distinct linguistic processing stages. This study analyzed 3,401 non-epileptic intracranial electrode sites from 37 children with focal epilepsy (age: 5–20 years) who underwent extraoperative electrocorticography recording. We used a principal component analysis of high-gamma modulations during an auditory naming task to determine the relative involvement of each cortical area during each linguistic processing stage. To quantify direct effective connectivity, we delivered single-pulse electrical stimulation to 488 temporal lobe sites and 1,581 extratemporal lobe sites and measured the early cortico-cortical spectral responses at distant electrodes. Mixed model analyses determined the effects of naming-related high-gamma co-augmentation between connecting regions, age, and cerebral hemisphere on the strength of effective connectivity independent of epilepsy-related factors. Direct effective connectivity was strongest between temporal and extratemporal lobe site pairs which were simultaneously activated during the period between sentence offset and verbal response onset (i.e., semantic retrieval period); this connectivity was approximately twice more robust than that with temporal lobe sites activated during stimulus listening or overt response. Conversely, extratemporal lobe sites activated during overt response were equally connected with temporal lobe language sites. Older age was associated with the increased strength of inter-lobar effective connectivity between those activated during semantic retrieval. The arcuate fasciculus supported approximately two-thirds of the direct effective connectivity pathways from temporal to extratemporal auditory language-related areas but only up to half of those in the opposite direction. The uncinate fasciculus consisted of only less than 2% of those in the temporal-to-extratemporal direction and up to 6% of those in the opposite direction. Our multimodal study quantified and animated the direct inter-lobar networks toward and from temporal lobe regions supporting distinct stages of auditory language processing. Additionally, age-dependent strengthening of connectivity after age five may preferentially occur between language areas supporting semantic retrieval.

A New Technique to Measure the Level of Interest Using Heartbeat-Evoked Brain Potential

Interest is a positive emotion related to attention. The event-related brain potential (ERP) probe technique is a useful method to evaluate the level of interest in dynamic stimuli. However, even in the irrelevant probe technique, the probe is presented as a physical stimulus and steals the observer’s attentional resources, although no overt response is required. Therefore, the probe might become a problematic distractor, preventing deep immersion of participants. Heartbeat-evoked brain potential (HEP) is a brain activity, time-locked to a cardiac event. No probe is required to obtain HEP data. Thus, we aimed to investigate whether the HEP can be used to evaluate the level of interest. Twenty-four participants (12 males and 12 females) watched attractive and unattractive individuals of the opposite sex in interesting and uninteresting videos (7 min each), respectively. We performed two techniques each for both the interesting and the uninteresting videos: the ERP probe and the HEP techniques. In the former, somatosensory stimuli were presented as task-irrelevant probes while participants watched videos: frequent (80%) and infrequent (20%) stimuli were presented at each wrist in random order. In the latter, participants watched videos without the probe. The P2 amplitude in response to the somatosensory probe was smaller and the positive wave amplitudes of HEP were larger while watching the videos of attractive individuals than while watching the videos of unattractive ones. These results indicate that the HEP technique is a useful method to evaluate the level of interest without an external probe stimulus.

Task-irrelevant visual forms facilitate covert and overt spatial selection

Covert and overt spatial selection behaviors are guided by both visual saliency maps derived from early visual features as well as priority maps reflecting high-level cognitive factors. However, whether mid-level perceptual processes associated with visual form recognition contribute to covert and overt spatial selection behaviors remains unclear. We hypothesized that if peripheral visual forms contribute to spatial selection behaviors, then they should do so even when the visual forms are task-irrelevant. We tested this hypothesis in male and female human subjects as well as in male macaque monkeys performing a visual detection task. In this task, subjects reported the detection of a supra-threshold target spot presented on top of one of two peripheral images, and they did so with either a speeded manual button press (humans) or a speeded saccadic eye movement response (humans and monkeys). Crucially, the two images, one with a visual form and the other with a partially phase-scrambled visual form, were completely irrelevant to the task. In both manual (covert) and oculomotor (overt) response modalities, and in both humans and monkeys, response times were faster when the target was congruent with a visual form than when it was incongruent. Importantly, incongruent targets were associated with almost all errors, suggesting that forms automatically captured selection behaviors. These findings demonstrate that mid-level perceptual processes associated with visual form recognition contribute to covert and overt spatial selection. This indicates that neural circuits associated with target selection, such as the superior colliculus, may have privileged access to visual form information.Significance statementSpatial selection of visual information either with (overt) or without (covert) foveating eye movements is critical to primate behavior. However, it is still not clear whether spatial maps in sensorimotor regions known to guide overt and covert spatial selection are influenced by peripheral visual forms. We probed the ability of humans and monkeys to perform overt and covert target selection in the presence of spatially congruent or incongruent visual forms. Even when completely task-irrelevant, images of visual objects had a dramatic effect on target selection, acting much like spatial cues used in spatial attention tasks. Our results demonstrate that traditional brain circuits for orienting behaviors, such as the superior colliculus, likely have privileged access to visual object representations.

Lelonkiewicz_et_al_2020_Adaptation_and_Anticipation

Interacting agents may anticipate their partner’s upcoming response and include it in their action plan. In turn, observing an overt response can trigger agents to adapt. But while anticipation and adaptation are known to shape action control, their interplay in social interactions remains largely unexplored. In four experiments, we asked how both of these mechanisms could contribute to one striking phenomenon: Agents initiate actions faster when they know their partner will produce a compatible rather than an incompatible response. In Experiment 1, we manipulated the compatibility between agents’ actions and partners’ responses, and investigated the interplay between adaptation and anticipation within the same dyadic interaction. In Experiments 2-4 we isolated the contribution of each of the two mechanisms by having agents interact with virtual partners whose responses could be experimentally controlled. We found that adaptation and anticipation exert parallel but independent effects on action execution: Participants initiated their actions more quickly when the upcoming partner response was compatible and, independently, when their partner had responded more quickly on the preceding trial. These findings elucidate models of action control in social interactions. [NOTE: Please cite this paper as: Lelonkiewicz, J. R., Gambi, C., Weller, L., & Pfister, R. (2020). Action–effect anticipation and temporal adaptation in social interactions. Journal of Experimental Psychology: Human Perception and Performance, 46(4), 335–349. https://doi.org/10.1037/xhp0000717 ]

Influence of kinesthetic motor imagery and effector specificity on the long-latency stretch response

The long-latency “reflexive” response (LLR) following an upper limb mechanical perturbation is generated by neural circuitry shared with voluntary control. This feedback response supports many task-dependent behaviors and permits the expression of goal-directed corrections at latencies shorter than voluntary reaction time. An extensive body of literature has demonstrated that the LLR shows flexibility akin to voluntary control, but it has not yet been tested whether instruction-dependent LLR changes can also occur in the absence of an overt voluntary response. The present study used kinesthetic motor imagery ( experiment 1) and instructed participants to execute movement with the unperturbed contralateral limb ( experiment 2) to explore the relationship between the overt production of a voluntary response and LLR facilitation. Activity in stretched right wrist flexors were compared with standard “do not-intervene” and “compensate” conditions. Our findings revealed that on ~40% of imagery and ~50% of contralateral trials, a response occurred during the voluntary epoch in the stretched right wrist flexors. On these “leaked” trials, the early portion of the LLR (R2) was facilitated and displayed a similar increase to compensate trials. The latter half of the LLR (R3) showed further modulation, mirroring the patterns of voluntary epoch activity. By contrast, the LLR on “non-leaked” imagery and contralateral trials did not modulate. We suggest that even though a hastened voluntary response cannot account for all instruction-dependent LLR modulation, the overt execution of a response during the voluntary epoch in the same muscle(s) as the LLR is a prerequisite for instruction-dependent facilitation of this feedback response. NEW & NOTEWORTHY Using motor imagery and contralateral responses, we provide novel evidence that facilitation of the long-latency reflex (LLR) requires the execution of a response during the voluntary epoch. A high proportion of overt response “leaks” were found where the mentally simulated or mirrored response appeared in stretched muscle. The first half of the LLR was categorically sensitive to the appearance of leaks, whereas the latter half displayed characteristics closely resembling activity in the ensuing voluntary period.

The P300 as marker of inhibitory control – fact or fiction?

Inhibitory control, i.e., the ability to stop or suppress actions, thoughts, or memories, represents a prevalent and popular concept in basic and clinical neuroscience as well as psychology. At the same time, it is notoriously difficult to study as successful inhibition is characterized by the absence of a continuously quantifiable direct behavioral marker. It has been suggested that the P3 latency, and here especially its onset latency, may serve as neurophysiological marker of inhibitory control as it correlates with the stop signal reaction time (SSRT). The SSRT estimates the average stopping latency, which itself is unobservable since no overt response is elicited in successful stop trials, based on differences in the distribution of go reaction times and the delay of the stop- relative to the go-signal in stop trials.In a meta-analysis and an independent EEG experiment, we found that correlations between the P3-latency and the SSRT are indeed replicable, but also unspecific. Not only does the SSRT also correlate with the N2-latency, but both P3- and N2-latency measures show similar or even higher correlations with other behavioral parameters such as the go reaction time or stopping accuracy. The missing specificity of P3-SSRT correlations, together with the general pattern of associations, suggests that these manifest effects are driven by underlying latent processes other than inhibition, such as those associated with the speed-accuracy trade-off.

Response Complexity Reduces Errors on a Response Inhibition Task

Objective The purpose of this investigation was to elucidate the role of button-response complexity to targets in a response inhibition task. Background Response inhibition is the ability to correctly inhibit an overt response to a target. The U.S. military is actively pursuing development of armed, combat robots as a force multiplier, which may present challenges to operators of combat robots in the form of response inhibition errors. Method A total of 15 participants completed two 51-min versions of a modified sustained attention to response task (SART). Participants were outfitted with an electrocardiogram to index heart-rate variability and completed the NASA–Task Load Index (NASA-TLX) to index workload. Results The results demonstrated that the complex SART reduced errors of commission (4%) and slowed response times (874 ms) to correct Go targets relative to the simple SART (14%, 739 ms). The NASA-TLX did not show differences between the modified SARTs; however, heart-rate variability did demonstrate that Soldiers had an increased autonomic stress response to the complex SART. Conclusion Increasing the behavioral response requirement during a response inhibition task can decrease errors of commission; however, it comes at the cost of slower response times to target stimuli. Heart-rate variability may provide better insight into objective workload relative to subjective measures. Application The use of complex behavioral responses may provide a viable option to reduce potential “friendly fire” or collateral damage by Soldiers remotely engaging a target-rich environment.

Flexibility in adopting relative frames of reference in dorsal and lateral settings

The relative frame of reference (FoR) is used to describe spatial relations between two objects from an observer’s perspective. Standard, frontal referencing situations with objects located in the observer’s visual field afford three well-established variants: translation, reflection, and rotation. Here, we focus on references in non-standard situations with objects located at the back or at the side of an observer ( dorsal and lateral, respectively). We scrutinise the consistency assumption, which was introduced to infer the covert strategy used in dorsal tasks from an ambiguous overt response: that, when confronted with a non-standard situation, people adopt a strategy consistent with how they construct the relative FoR in frontal situations. Lateral tasks enable us to disentangle the ambiguous response. The results of a study in Norway and Germany support the consistency assumption in part: Nearly all participants with a preference for translation in frontal tasks applied translation in lateral tasks, and some participants with a preference for reflection in frontal tasks turned towards the objects before applying reflection in lateral tasks. Most other participants with a preference for reflection in frontal tasks, however, switched to translation in lateral tasks. The latter may be due to a specific affordance of the lateral arrangements, which invite translation as the easier strategy compared to the alternative derived from reflection. Our findings indicate that people do not apply their preferred variant of the relative FoR to all kinds of situations, but rather flexibly adapt their strategy when it is more convenient to do so.

From Bullets to Banners and Back Again? The Ambivalent Role of Ex-combatants in Contested Land Deals in Sierra Leone

The rise of land deals poses unpredictable risks to war-torn societies, exposing them to the violent folds of the global economy. In Sierra Leone, commercial land leases have perpetuated the chieftaincy monopoly, further curtailed social mobility, and sparked particular resentment among youths and ex-combatants. Drawing on the concept of the “war machine,” I analyse how Kamajor militia fighters shape contestation against land deals and explore the attendant risks for remobilisation and conflict transformation. My findings, based on in-depth ethnographic field research, indicate that while aggrieved communities turn to Kamajor-run civil society organisations for support, Kamajor living in precarious conditions largely shy away from open contestation. While the historically close ties between the Kamajor and the chieftaincy have eroded in the wake of commercial land leases, complex patronage networks along with the moral setback encountered from the Special Court proceedings and tight surveillance thwart a more overt response. Yet, the Kamajor’s background support remains key to the struggle of anti-plantation and mining activists.

You’d better decide first: overt and covert decisions improve metacognitive accuracy

How can we assess the accuracy of our decisions? Recent theoretical and empirical work suggest that confidence in one’s decision is influenced by the characteristics of motor response in a preceding decisional task. In this paper we present experiment designed to test whether decision itself can also inform confidence and therefore increase its accuracy. We tested 143 participants who solved an anagram-solving task in one of 3 conditions: participants either rated their confidence immediately after responding to the anagram task (overt decision), rated their confidence immediately after making a decision but without overt response (covered decision), or rated their confidence before both deciding and responding. The results showed significant relationship between decision accuracy and confidence level in each condition, however this relation was stronger when confidence rating followed decision, either covert or overt. We argue that completing a decisionmaking process increases metacognitive accuracy.