What Simon "knows" about cultural differences: The influence of cultural orientation and traffic directionality on spatial compatibility effects.

Previous research has suggested that culture influences perception and attention. These studies have typically involved comparisons of Westerners with East Asians, motivated by assumed differences in the cultures' self-concept or position on the individualism-collectivism spectrum. However, other potentially important sources of cultural variance have been neglected, such as differences in traffic directionality shaped by the urban spatial environment (i.e., left-hand vs. right-hand traffic). Thus, existing research may potentially place too much emphasis on self-concepts or the individualism-collectivism dimension in explaining observed cultural differences in cognition. The present study investigated spatial cognition using a Simon task and tested participants from four nations (Australia, China, Germany, and Malaysia) that differ in both cultural orientation (collectivistic vs. individualistic) and traffic directionality (left-hand vs. right-hand traffic). The task used two possible reference frames underlying the Simon effect: a body-centered one based on global stimulus position relative to the screen's center versus an object-centered one based on local stimulus position relative to a context object. As expected, all groups showed a reliable Simon effect for both spatial reference frames. However, the global Simon effect was larger in participants from countries with left-hand traffic. In contrast, the local Simon effect was modulated by differences in cultural orientation, with larger effects in participants from collectivistic cultures. This pattern suggests that both sources of cultural variation, viz. cultural orientation and traffic directionality, contribute to differences in spatial cognition in distinct ways.

Sensory attenuation prevails when controlling for temporal predictability of self- and externally generated tones.

Sensory attenuation of self-produced, compared to physically identical but externally produced events is a classical finding in research on perception in action. The most prominent model to explain this effect draws on an internal forward model generating predictions about action outcomes, efference copies, during action planning and initiation. Even though this finding has a long tradition in psychology and neuroscience, several studies have highlighted methodological limitations which open the door for alternative explanations of sensory attenuation effects, most notably in terms of temporal prediction. Here we present an experimental design which carefully controls for this confounding factor. Crucially, we observed the auditory N1 component of the event-related potential to be attenuated for self-generated tones as compared to externally generated tones even when a predictive cue (a bar that is continuously filling up) allows for identical temporal predictability of both events. These findings suggest that voluntary actions do indeed involve a unique, predictive component, affecting the perceptual processing of ensuing events.

Sharing Different Reference Frames: How Stimulus Setup and Task Setup Shape Egocentric and Allocentric Simon Effects.

Different reference frames are used in daily life in order to structure the environment. The two-choice Simon task setting has been used to investigate how task-irrelevant spatial information influences human cognitive control. In recent studies, a Go/NoGo Simon task setting was used in order to divide the Simon task between a pair of participants. Yet, not only a human co-actor, but also even an attention-grabbing object can provide sufficient reference in order to reintroduce a Simon effect (SE) indicating cognitive conflict in Go/NoGo task settings. Interestingly, the SE could only occur when a reference point outside of the stimulus setup was available. The current studies exploited the dependency between different spatial reference frames (egocentric and allocentric) offered by the stimulus setup itself and the task setup (individual vs. joint Go/NoGot task setting). Two studies (Experiments 1 and 2) were carried out along with a human co-actor. Experiment 3 used an attention-grabbing object instead. The egocentric and allocentric SEs triggered by different features of the stimulus setup (global vs. local) were modulated by the task setup. When interacting with a human co-actor, an egocentric SE was found for global features of the stimulus setup (i.e., stimulus position on the screen). In contrast, an allocentric SE was yielded in the individual task setup illustrating the relevance of more local features of the stimulus setup (i.e., the manikin's ball position). Results point toward salience shifts between different spatial reference frames depending on the nature of the task setup.

An Internet-Based Real-Time Audiovisual Link for Dual MEG Recordings.

HYPERSCANNING: Most neuroimaging studies of human social cognition have focused on brain activity of single subjects. More recently, "two-person neuroimaging" has been introduced, with simultaneous recordings of brain signals from two subjects involved in social interaction. These simultaneous "hyperscanning" recordings have already been carried out with a spectrum of neuroimaging modalities, such as functional magnetic resonance imaging (fMRI), electroencephalography (EEG), and functional near-infrared spectroscopy (fNIRS). DUAL MEG SETUP: We have recently developed a setup for simultaneous magnetoencephalographic (MEG) recordings of two subjects that communicate in real time over an audio link between two geographically separated MEG laboratories. Here we present an extended version of the setup, where we have added a video connection and replaced the telephone-landline-based link with an Internet connection. Our setup enabled transmission of video and audio streams between the sites with a one-way communication latency of about 130 ms. Our software that allows reproducing the setup is publicly available. VALIDATION: We demonstrate that the audiovisual Internet-based link can mediate real-time interaction between two subjects who try to mirror each others' hand movements that they can see via the video link. All the nine pairs were able to synchronize their behavior. In addition to the video, we captured the subjects' movements with accelerometers attached to their index fingers; we determined from these signals that the average synchronization accuracy was 215 ms. In one subject pair we demonstrate inter-subject coherence patterns of the MEG signals that peak over the sensorimotor areas contralateral to the hand used in the task.

My partner is also on my mind: social context modulates the N1 response.

When individuals share a task with a partner, one's own actions and one's partner's actions have to be precisely tuned to one another. With behavioral means, it has been numerously shown that splitting a simple reaction time task between two participants produces similar interference patterns to those occurring when controlling the whole task on one's own. Less is known about the neuronal correlates when sharing a task with a partner. The processes of agent identification ("my turn" vs. "my partner's turn") were the focus of this study. In an EEG study, pairs of participants responded to different action-associated stimuli in a Go/NoGo paradigm. The same task was performed together with a partner (joint Go/NoGo condition) and when a partner was not present (single Go/NoGo condition). This study showed a top-down influence of social setting on early visual processing as indexed by the Go-N1 and NoGo-N1 response. This effect was only present in the joint Go/NoGo condition. It was particularly present in those trials where the partner did not have to act. Taken together, these results yield evidence for an early top-down influence of social setting on early processes of stimulus identification and differentiation.

MEG dual scanning: a procedure to study real-time auditory interaction between two persons.

Social interactions fill our everyday life and put strong demands on our brain function. However, the possibilities for studying the brain basis of social interaction are still technically limited, and even modern brain imaging studies of social cognition typically monitor just one participant at a time. We present here a method to connect and synchronize two faraway neuromagnetometers. With this method, two participants at two separate sites can interact with each other through a stable real-time audio connection with minimal delay and jitter. The magnetoencephalographic (MEG) and audio recordings of both laboratories are accurately synchronized for joint offline analysis. The concept can be extended to connecting multiple MEG devices around the world. As a proof of concept of the MEG-to-MEG link, we report the results of time-sensitive recordings of cortical evoked responses to sounds delivered at laboratories separated by 5 km.

Action-sound coincidences suppress evoked responses of the human auditory cortex in EEG and MEG.

The N1 auditory ERP and its magnetic counterpart (N1[m]) are suppressed when elicited by self-induced sounds. Because the N1(m) is a correlate of auditory event detection, this N1 suppression effect is generally interpreted as a reflection of the workings of an internal forward model: The forward model captures the contingency (causal relationship) between the action and the sound, and this is used to cancel the predictable sensory reafference when the action is initiated. In this study, we demonstrated in three experiments using a novel coincidence paradigm that actual contingency between actions and sounds is not a necessary condition for N1 suppression. Participants performed time interval production tasks: They pressed a key to set the boundaries of time intervals. Concurrently, but independently of keypresses, a sequence of pure tones with random onset-to-onset intervals was presented. Tones coinciding with keypresses elicited suppressed N1(m) and P2(m), suggesting that action-stimulus contiguity (temporal proximity) is sufficient to suppress sensory processing related to the detection of auditory events.

The cerebellum generates motor-to-auditory predictions: ERP lesion evidence.

Forward predictions are crucial in motor action (e.g., catching a ball, or being tickled) but may also apply to sensory or cognitive processes (e.g., listening to distorted speech or to a foreign accent). According to the "internal forward model," the cerebellum generates predictions about somatosensory consequences of movements. These predictions simulate motor processes and prepare respective cortical areas for anticipated sensory input. Currently, there is very little evidence that a cerebellar forward model also applies to other sensory domains. In the current study, we address this question by examining the role of the cerebellum when auditory stimuli are anticipated as a consequence of a motor act. We applied an N100 suppression paradigm and compared the ERP in response to self-initiated with the ERP response to externally produced sounds. We hypothesized that sensory consequences of self-initiated sounds are precisely predicted and should lead to an N100 suppression compared with externally produced sounds. Moreover, if the cerebellum is involved in the generation of a motor-to-auditory forward model, patients with focal cerebellar lesions should not display an N100 suppression effect. Compared with healthy controls, patients showed a largely attenuated N100 suppression effect. The current results suggest that the cerebellum forms not only motor-to-somatosensory predictions but also motor-to-auditory predictions. This extends the cerebellar forward model to other sensory domains such as audition.

Selective suppression of self-initiated sounds in an auditory stream: An ERP study.

Numerous studies have shown that the N1 event-related potential (ERP) response is attenuated when it is elicited by self-initiated sounds. This N1 suppression effect is generally interpreted to reflect an internal prediction mechanism, which enables the discrimination of the sensory consequences of our own actions and those of others. The blocked design used in the forerunner studies (i.e., self- and externally initiated sounds presented in different blocks) seriously limits the relevance of these findings, because the N1 effect can simply be explained by contextual task differences. In the present study, self- and externally initiated sounds were mixed within blocks. N1 suppression was found, and its magnitude was even larger than that observed in a traditional blocked condition. This result supports the involvement of an internal prediction mechanism in the discrimination of the sensory consequences of one's own actions and those of others.

Attenuated human auditory middle latency response and evoked 40-Hz response to self-initiated sounds.

For several modalities, it has been shown that the processing of sensory information generated by our own actions is attenuated relative to the processing of sensory information of externally generated stimuli. It has been proposed that the underlying mechanism builds predictions about the forthcoming sensory input and forwards them to the respective sensory processing levels. The present study investigated whether early auditory processing is suppressed by the top-down influences of such an internal forward model mechanism. To this end, we compared auditory middle latency responses (MLRs) and evoked 40-Hz responses elicited by self-initiated sounds with those elicited by externally initiated but otherwise identical sounds. In the self-initiated condition, the amplitudes of the Pa (27-33 ms relative to sound onset) and Nb (40-46 ms) components of the MLRs were significantly attenuated when compared to the responses elicited by click sounds presented in the externally initiated condition. Similarly, the evoked activity in the 40-Hz and adjacent frequency bands was attenuated. Considering that previous research revealed subcortical and auditory cortex contributions to MLRs and 40-Hz responses, our results support the existence of auditory suppression effects with self-initiated sounds on temporally and structurally early auditory processing levels. This attenuation in the processing of self-initiated sounds most probably contributes to the optimal processing of concurrent external acoustic events.