Sensorimotor activation related to speaker vs. listener role during natural conversation.

Although the main function of speech is communication, the brain bases of speaking and listening are typically studied in single subjects, leaving unsettled how brain function supports interactive vocal exchange. Here we used whole-scalp magnetoencephalography (MEG) to monitor modulation of sensorimotor brain rhythms related to the speaker vs. listener roles during natural conversation. Nine dyads of healthy adults were recruited. The partners of a dyad were engaged in live conversations via an audio link while their brain activity was measured simultaneously in two separate MEG laboratories. The levels of ∼10-Hz and ∼20-Hz rolandic oscillations depended on the speaker vs. listener role. In the left rolandic cortex, these oscillations were consistently (by ∼20%) weaker during speaking than listening. At the turn changes in conversation, the level of the ∼10Hz oscillations enhanced transiently around 1.0 or 2.3s before the end of the partner's turn. Our findings indicate left-hemisphere-dominant involvement of the sensorimotor cortex during own speech in natural conversation. The ∼10-Hz modulations could be related to preparation for starting one's own turn, already before the partner's turn has finished.

Across-Time Change and Variation in Cultural Tightness-Looseness.

Cultural tightness-looseness, a dimension which describes the strength, multitude, and clarity of social norms in a culture, has proved significant in explaining differences between cultures. Although several studies have compared different cultures on this domain, this study is the first that targets both within-country differences and across-time variation in tightness-looseness. Using data from two nationally representative samples of Estonians, we found that the general tightness level had changed over a period of 10 years but the effect size of the change was small. A significant within country variance in 2002 had disappeared by 2012. Our results suggest that tightness-looseness, similarly to cultural value orientations, is a relatively stable and robust characteristic of culture-that is, change indeed takes place, but slowly. Future studies about across-time change and within-country variance in tightness-looseness should target more culturally diverse and socially divided societies.

Word-by-word entrainment of speech rhythm during joint story building.

Movements and behavior synchronize during social interaction at many levels, often unintentionally. During smooth conversation, for example, participants adapt to each others' speech rates. Here we aimed to find out to which extent speakers adapt their turn-taking rhythms during a story-building game. Nine sex-matched dyads of adults (12 males, 6 females) created two 5-min stories by contributing to them alternatingly one word at a time. The participants were located in different rooms, with audio connection during one story and audiovisual during the other. They were free to select the topic of the story. Although the participants received no instructions regarding the timing of the story building, their word rhythms were highly entrained (øverlineR = 0.70, p < 0.001) even though the rhythms as such were unstable (øverlineR = 0.14 for pooled data). Such high entrainment in the absence of steady word rhythm occurred in every individual story, independently of whether the subjects were connected via audio-only or audiovisual link. The observed entrainment was of similar strength as typical entrainment in finger-tapping tasks where participants are specifically instructed to synchronize their behavior. Thus, speech seems to spontaneously induce strong entrainment between the conversation partners, likely reflecting automatic alignment of their semantic and syntactic processes.

Brain responds to another person's eye blinks in a natural setting-the more empathetic the viewer the stronger the responses.

An observer's brain is known to respond to another person's small nonverbal signals, such as gaze shifts and eye blinks. Here we aimed to find out how an observer's brain reacts to a speaker's eye blinks in the presence of other audiovisual information. Magnetoencephalographic brain responses along with eye gaze were recorded from 13 adults who watched a video of a person telling a story. The video was presented first without sound (visual), then with sound (audiovisual), and finally the audio story was presented with a still-frame picture on the screen (audio control). The viewers mainly gazed at the eye region of the speaker. Their saccades were suppressed at about 180 ms after the start of the speaker's blinks, a subsequent increase of saccade occurence to the base level, or higher, at around 340 ms. The suppression occurred in visual and audiovisual conditions but not during the control audio presentation. Prominent brain responses to blinks peaked in the viewer's occipital cortex at about 250 ms, with no differences in mean peak amplitudes or latencies between visual and audiovisual conditions. During the audiovisual, but not visual-only, presentation, the responses were the stronger the more empathetic the subject was according to the Empathic Concern score of the Interpersonal Reactivity Index questionnaire (Spearman's rank correlation, 0.73). The other person's eye blinks, nonverbal signs that often go unnoticed, thus elicited clear brain responses even in the presence of attention-attracting audiovisual information from the narrative, with stronger responses in people with higher empathy scores.

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.

Neuromagnetic brain responses to other person's eye blinks seen on video.

Eye blinks, typically occurring 15-20 times per minute, rarely capture attention during face-to-face interaction. To determine the extent to which eye blinks affect the viewer's brain activity, we recorded magnetoencephalographic brain responses to natural blinks, and to the same blinks slowed down to 38% of the original speed. The stimuli were presented on video once every 2.3-6.2 s. As a control, we presented two horizontal black bars moving with the same time courses and the same extent as the eyelids in the blink video. Both types of blinks and bars elicited clear responses peaking at about 200 ms in the occipital areas, with no systematic differences between hemispheres. For the bars, these main responses were (as expected) weaker (by 24%) and later (by 33 ms) to slow-motion than normal-speed stimuli. For blinks, however, the responses to both normal-speed and slow-motion stimuli were of the same amplitude and latency. Our results demonstrate that the brain not only responds to other persons' eye blinks, but that the responses are as fast and of equal size even when the blinks are considerably slowed down. We interpret this finding to reflect the increased social salience of the slowed-down blinks that counteracted the general tendency of the brain to react more weakly and more slowly to slowly- vs. quickly-changing stimuli. This finding may relate to the social importance of facial gestures, including eye blinks.

Binaural interaction and the octave illusion.

The auditory octave illusion arises when dichotically presented tones, one octave apart, alternate rapidly between the ears. Most subjects perceive an illusory sequence of monaural tones: A high tone in the right ear (RE) alternates with a low tone, incorrectly localized to the left ear (LE). Behavioral studies suggest that the perceived pitch follows the RE input, and the perceived location the higher-frequency sound. To explore the link between the perceived pitches and brain-level interactions of dichotic tones, magnetoencephalographic responses were recorded to 4 binaural combinations of 2-min long continuous 400- and 800-Hz tones and to 4 monaural tones. Responses to LE and RE inputs were distinguished by frequency-tagging the ear-specific stimuli at different modulation frequencies. During dichotic presentation, ipsilateral LE tones elicited weaker and ipsilateral RE tones stronger responses than when both ears received the same tone. During the most paradoxical stimulus-high tone to LE and low tone to RE perceived as a low tone in LE during the illusion-also the contralateral responses to LE tones were diminished. The results demonstrate modified binaural interaction of dichotic tones one octave apart, suggesting that this interaction contributes to pitch perception during the octave illusion.

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.