Touching lips and hearing fingers: effector-specific congruency between tactile and auditory stimulation modulates N1 amplitude and alpha desynchronization

EEG correlates of anticipatory attention and target processing in children and adults during visual spatial attention

The ability of attentional orienting has been suggested to keep developing throughout childhood. Electroencephalography (EEG) studies have shown that 6-10 year old children exhibit lateralized alpha-band (8-13 Hz) activity and event-related potentials (ERPs) that are classic markers of spatial attentional orienting in adults. However, the lack of a direct comparison of these EEG correlates between children and adults in the same experiment made it difficult to evaluate developmental effects on neural activity throughout attentional stages. This study aimed to directly compare cue-related alpha activity and ERPs for the anticipatory attention stage and target-related ERPs for the target processing stage between healthy children and adults. Participants, including 19 children (6-10 years) and 23 adults (18-34 years), successfully completed a visual spatial attention task, although children responded more slowly and less consistently than adults. Both age groups exhibited significant cue-related alpha lateralization and ERPs (EDAN, ADAN, and LDAP) during anticipatory attention and significant attentional modulation of target-related N1 during target processing. However, no significant difference was found in the magnitude of attentional modulation of these EEG correlates between children and adults. These findings suggest that the neural underpinnings of anticipatory attention and target processing during visual spatial attention could have been largely developed in 6-10 year old children.

Implementation of an Early Communication Intervention for Young Children with Cerebral Palsy Using Single-Subject Research Design

The implementation of an intervention protocol aimed at increasing vocal complexity in three pre-linguistic children with cerebral palsy (two males, starting age 15 months, and one female, starting age 16 months) was evaluated utilising a repeated ABA case series design. The study progressed until the children were 36 months of age. Weekly probes with trained and untrained items were administered across each of three intervention blocks. Successive blocks targeted more advanced protophone production and speech movement patterns, individualised for each participant. Positive treatment effects were seen for all participants in terms of a greater rate of achievement of target protophone categories and speech movement patterns. Tau coefficients for trained items demonstrated overall moderate to large AB phase contrast effect sizes, with limited evidence of generalisation to untrained items. Control items featuring protophones and speech movements not targeted for intervention showed no change across phases for any participant. Our data suggest that emerging speech-production skills in prelinguistic infants with CP can be positively influenced through a multimodal intervention focused on capitalising on early periods of plasticity when language learning is most sensitive.

Towards a somatosensory theory of speech perception

Speech perception is known to be a multimodal process, relying not only on auditory input but also on the visual system and possibly on the motor system as well. To date there has been little work on the potential involvement of the somatosensory system in speech perception. In the present review, we identify the somatosensory system as another contributor to speech perception. First, we argue that evidence in favor of a motor contribution to speech perception can just as easily be interpreted as showing somatosensory involvement. Second, physiological and neuroanatomical evidence for auditory-somatosensory interactions across the auditory hierarchy indicates the availability of a neural infrastructure that supports somatosensory involvement in auditory processing in general. Third, there is accumulating evidence for somatosensory involvement in the context of speech specifically. In particular, tactile stimulation modifies speech perception, and speech auditory input elicits activity in somatosensory cortical areas. Moreover, speech sounds can be decoded from activity in somatosensory cortex; lesions to this region affect perception, and vowels can be identified based on somatic input alone. We suggest that the somatosensory involvement in speech perception derives from the somatosensory-auditory pairing that occurs during speech production and learning. By bringing together findings from a set of studies that have not been previously linked, the present article identifies the somatosensory system as a presently unrecognized contributor to speech perception.

Body representations as indexed by oscillatory EEG activities in the context of tactile novelty processing

Neural oscillatory activities in different frequency bands are known to reflect different cognitive functions. The current study investigates neural oscillations involved in tactile novelty processing, in particular how physically different digits of the hand may be categorized as being more or less similar to one another. Time-frequency analyses were conducted on EEG responses recorded from a somatosensory mismatch protocol involving stimulation of the 1st, 3rd, and 5th digits. The pattern of tactile stimulation leveraged a functional category boundary between the 1st digit (thumb) and the other fingers. This functional category has been hypothesized to derive, in part, from the way that the hand is used to grasp and haptically explore objects. EEG responses to standard stimuli (the 3rd digit, probability of 80%) and two deviant stimuli (1st digit as across-boundary deviant and 5th digit as within-boundary deviant, probability of 10% each) were examined. Analyses of EEG responses examined changes in power as well as phase information. Deviant tactile stimuli evoked significantly greater theta event-related synchronization and greater phase-locking values compared to the corresponding control stimuli. The increase in theta power evoked by the contrast of the 3rd digit and the 1st digit was significantly larger than for the contrast between the 3rd and 5th digits. Desynchronization in the alpha and beta bands was greater for deviant than control stimuli, which may reflect increased local cortical excitation to novel stimuli, modulated by top-down feedback processes as part of a hierarchical novelty detection mechanism. The results are discussed in the context of the growing literature on neural processes involved in the generation and maintenance of body representations.

Sensorimotor Oscillations During a Reciprocal Touch Paradigm With a Human or Robot Partner

Robots provide an opportunity to extend research on the cognitive, perceptual, and neural processes involved in social interaction. This study examined how sensorimotor oscillatory electroencephalogram (EEG) activity can be influenced by the perceived nature of a task partner – human or robot – during a novel “reciprocal touch” paradigm. Twenty adult participants viewed a demonstration of a robot that could “feel” tactile stimulation through a haptic sensor on its hand and “see” changes in light through a photoreceptor at the level of the eyes; the robot responded to touch or changes in light by moving a contralateral digit. During EEG collection, participants engaged in a joint task that involved sending tactile stimulation to a partner (robot or human) and receiving tactile stimulation back. Tactile stimulation sent by the participant was initiated by a button press and was delivered 1500 ms later via an inflatable membrane on the hand of the human or on the haptic sensor of the robot partner. Stimulation to the participant’s finger (from the partner) was sent on a fixed schedule, regardless of partner type. We analyzed activity of the sensorimotor mu rhythm during anticipation of tactile stimulation to the right hand, comparing mu activity at central electrode sites when participants believed that tactile stimulation was initiated by a robot or a human, and to trials in which “nobody” received stimulation. There was a significant difference in contralateral mu rhythm activity between anticipating stimulation from a human partner and the “nobody” condition. This effect was less pronounced for anticipation of stimulation from the robot partner. Analyses also examined beta rhythm responses to the execution of the button press, comparing oscillatory activity when participants sent tactile stimulation to the robot or the human partner. The extent of beta rebound at frontocentral electrode sites following the button press differed between conditions, with a significantly larger increase in beta power when participants sent tactile stimulation to a robot partner compared to the human partner. This increase in beta power may reflect greater predictably in event outcomes. This new paradigm and the novel findings advance the neuroscientific study of human–robot interaction.

Cross-modal effects in speech perception

Speech research during recent years has moved progressively away from its traditional focus on audition toward a more multisensory approach. In addition to audition and vision, many somatosenses including proprioception, pressure, vibration and aerotactile sensation are all highly relevant modalities for experiencing and/or conveying speech. In this article, we review both long-standing cross-modal effects stemming from decades of audiovisual speech research as well as new findings related to somatosensory effects. Cross-modal effects in speech perception to date are found to be constrained by temporal congruence and signal relevance, but appear to be unconstrained by spatial congruence. Far from taking place in a one-, two- or even three-dimensional space, the literature reveals that speech occupies a highly multidimensional sensory space. We argue that future research in cross-modal effects should expand to consider each of these modalities both separately and in combination with other modalities in speech.

Neural representations of the body in 60-day-old human infants

The organization of body representations in the adult brain has been well documented. Little is understood about this aspect of brain organization in human infancy. The current study employed electroencephalography (EEG) with 60-day-old infants to test the distribution of brain responses to tactile stimulation of three different body parts: hand, foot, and lip. Analyses focused on a prominent positive response occurring at 150-200 ms in the somatosensory evoked potential at central and parietal electrode sites. The results show differential electrophysiological signatures for touch of these three body parts. Stimulation of the left hand was associated with greater positive amplitude over the lateral central region contralateral to the side stimulated. Left foot stimulation was associated with greater positivity over the midline parietal site. Stimulation of the midline of the upper lip was associated with a strong bilateral response over the central region. These findings provide new insights into the neural representation of the body in infancy and shed light on research and theories about the involvement of somatosensory cortex in infant imitation and social perception.