A rapid sound-action association effect in human insular cortex

Cortical network differences in the sighted versus early blind for recognition of human-produced action sounds

Both sighted and blind individuals can readily interpret meaning behind everyday real-world sounds. In sighted listeners, we previously reported that regions along the bilateral posterior superior temporal sulci (pSTS) and middle temporal gyri (pMTG) are preferentially activated when presented with recognizable action sounds. These regions have generally been hypothesized to represent primary loci for complex motion processing, including visual biological motion processing and audio-visual integration. However, it remained unclear whether, or to what degree, life-long visual experience might impact functions related to hearing perception or memory of sound-source actions. Using functional magnetic resonance imaging (fMRI), we compared brain regions activated in congenitally blind versus sighted listeners in response to hearing a wide range of recognizable human-produced action sounds (excluding vocalizations) versus unrecognized, backward-played versions of those sounds. Here, we show that recognized human action sounds commonly evoked activity in both groups along most of the left pSTS/pMTG complex, though with relatively greater activity in the right pSTS/pMTG by the blind group. These results indicate that portions of the postero-lateral temporal cortices contain domain-specific hubs for biological and/or complex motion processing independent of sensory-modality experience. Contrasting the two groups, the sighted listeners preferentially activated bilateral parietal plus medial and lateral frontal networks, whereas the blind listeners preferentially activated left anterior insula plus bilateral anterior calcarine and medial occipital regions, including what would otherwise have been visual-related cortex. These global-level network differences suggest that blind and sighted listeners may preferentially use different memory retrieval strategies when hearing and attempting to recognize action sounds.

Event-related spectral perturbation induced by action-related sound

It is now well established that human brain is endowed with an auditory-motor system which may depend on individual's motor experience. Here we designed an electroencephalography (EEG) experiment for investigating this dependency. A sound with not-so-obvious meaning was presented to subjects firstly. Then a visual exposure process was carried out to establish an association between the sound and action. By analyzing event-related spectral perturbation (ERSP) in the mu rhythm, we expected to find response differences in the motor cortex between the pre- and post-exposure periods. Results of 14 subjects indicated that the activation of motor cortex was stronger in the post-exposure phase. Our study suggests that the auditory-motor association can be established rapidly by a simple exposure process.

SELF-GENERATED ACTIONS DURING LEARNING OBJECTS AND SOUNDS CREATE SENSORI-MOTOR SYSTEMS IN THE DEVELOPING BRAIN

Previous research shows that sensory and motor systems interact during verb perception, and that these interactions are formed through self-generated actions that refer to verb labels during development. Here we expand on these findings by investigating whether self-generated actions lead to sensori-motor interaction during sound perception and visual perception. The current research exposes young children to novel sounds that are produced by object movement through either a) actively exploring the objects and producing the sounds or b) by seeing and hearing an experimenter interact with the objects. Results demonstrate that the motor system was recruited during auditory perception only after learning involved self-generated interactions with objects. Interestingly, visual association regions were also active during both sound perception and visual perception after active exploratory learning, but not after passive observation. Therefore, in the developing brain, associations are built upon real-world interactions of body and environment, leading to sensori-motor representations of both objects and sounds.

Differential language expertise related to white matter architecture in regions subserving sensory-motor coupling, articulation, and interhemispheric transfer

The technique of diffusion tensor imaging (DTI) has been used to investigate alterations in white matter architecture following long-term training and expertise. Professional simultaneous interpreters (SI) provide an ideal model for the investigation of training-induced plasticity due to the high demands placed on sound to motor mapping mechanisms, which are vital for executing fast interpretations. In line with our hypothesis, we found clusters with decreased fractional anisotropy (FA) in the SI group in brain regions previously shown to support sensory-motor coupling mechanisms and speech articulation (cluster extent family-wise error corrected, P < 0.01). Furthermore, we found an altered white matter architecture indicated by lower FA values in the SI group in the most anterior and posterior parts of the corpus callosum. Our results suggest that language expertise is accompanied by plastic adaptations in regions strongly involved in motor aspects of speech and in interhemispheric information transfer. These results have implications for our understanding of language expertise in relation to white matter adaptations.

Cortical networks representing object categories and high-level attributes of familiar real-world action sounds

In contrast to visual object processing, relatively little is known about how the human brain processes everyday real-world sounds, transforming highly complex acoustic signals into representations of meaningful events or auditory objects. We recently reported a fourfold cortical dissociation for representing action (nonvocalization) sounds correctly categorized as having been produced by human, animal, mechanical, or environmental sources. However, it was unclear how consistent those network representations were across individuals, given potential differences between each participant's degree of familiarity with the studied sounds. Moreover, it was unclear what, if any, auditory perceptual attributes might further distinguish the four conceptual sound-source categories, potentially revealing what might drive the cortical network organization for representing acoustic knowledge. Here, we used functional magnetic resonance imaging to test participants before and after extensive listening experience with action sounds, and tested for cortices that might be sensitive to each of three different high-level perceptual attributes relating to how a listener associates or interacts with the sound source. These included the sound's perceived concreteness, effectuality (ability to be affected by the listener), and spatial scale. Despite some variation of networks for environmental sounds, our results verified the stability of a fourfold dissociation of category-specific networks for real-world action sounds both before and after familiarity training. Additionally, we identified cortical regions parametrically modulated by each of the three high-level perceptual sound attributes. We propose that these attributes contribute to the network-level encoding of category-specific acoustic knowledge representations.

Brain activation of children with developmental coordination disorder is different than peers

OBJECTIVES

Children with developmental coordination disorder (DCD) struggle to learn new motor skills, demonstrating more variable performance than typically developing (TD) children. The purpose of this study was to determine whether patterns of brain activity differed between children with and without DCD while performing a motor task.

METHODS

Using functional MRI, we measured brain activation patterns in 7 children with DCD and 7 age-matched peers (aged 8-12 years) during a fine-motor, trail-tracing task.

RESULTS

Despite similar levels of behavioral motor performance, different patterns of brain activity were noted between the 2 groups. The group with DCD showed significantly more activation than control subjects in left inferior parietal lobule, right middle frontal gyrus, right supramarginal gyrus, right lingual gyrus, right parahippocampal gyrus, right posterior cingulate gyrus, right precentral gyrus, right superior temporal gyrus, and right cerebellar lobule VI. These results suggest that the group with DCD relied on visuospatial processing to complete the task. The TD group demonstrated significantly more activation than the group with DCD in left precuneus, left superior frontal gyrus, right superior temporal gyrus/insula, left inferior frontal gyrus, and left postcentral gyrus; these regions have been associated with spatial processing, motor control and learning, and error processing.

CONCLUSIONS

Children with DCD activate different brain regions from typical children when performing the same trail-tracing task. Despite the small sample size, our results contribute to a growing body of literature suggesting that children with DCD exhibit differences in neural networks and patterns of brain activation relative to same-age peers.

The Internal Anticipation of Sensory Action Effects: When Action Induces FFA and PPA Activity

Voluntary action – in particular the ability to produce desired effects in the environment – is fundamental to human existence. According to ideomotor theory we can achieve goals in the environment by means of anticipating their outcomes. We aimed at providing neurophysiological evidence for the assumption that performing actions calls for the activation of brain areas associated with the sensory effects usually evoked by the actions. We conducted an fMRI study in which right and left button presses lead to the presentation of face and house pictures. We compared a baseline phase with the same phase after participants experienced the association between button presses and pictures. We found an increase in the parahippocampal place area (PPA) for the response that has been associated with house pictures and fusiform face area (FFA) for the response that has been coupled with face pictures. This observation constitutes support for ideomotor theory.

Vocal accuracy and neural plasticity following micromelody-discrimination training

Background

Recent behavioral studies report correlational evidence to suggest that non-musicians with good pitch discrimination sing more accurately than those with poorer auditory skills. However, other studies have reported a dissociation between perceptual and vocal production skills. In order to elucidate the relationship between auditory discrimination skills and vocal accuracy, we administered an auditory-discrimination training paradigm to a group of non-musicians to determine whether training-enhanced auditory discrimination would specifically result in improved vocal accuracy.

Methodology/Principal Findings

We utilized micromelodies (i.e., melodies with seven different interval scales, each smaller than a semitone) as the main stimuli for auditory discrimination training and testing, and we used single-note and melodic singing tasks to assess vocal accuracy in two groups of non-musicians (experimental and control). To determine if any training-induced improvements in vocal accuracy would be accompanied by related modulations in cortical activity during singing, the experimental group of non-musicians also performed the singing tasks while undergoing functional magnetic resonance imaging (fMRI). Following training, the experimental group exhibited significant enhancements in micromelody discrimination compared to controls. However, we did not observe a correlated improvement in vocal accuracy during single-note or melodic singing, nor did we detect any training-induced changes in activity within brain regions associated with singing.

Conclusions/Significance

Given the observations from our auditory training regimen, we therefore conclude that perceptual discrimination training alone is not sufficient to improve vocal accuracy in non-musicians, supporting the suggested dissociation between auditory perception and vocal production.

Implicit chord processing and motor representation in pianists

The aim of this paper is to assess the relevance of pitch dimension in auditory-motor interaction. Several behavioural and brain imaging studies have shown that auditory processing of sounds can activate motor representations, an effect which is however elicited only by action-related sounds, i.e., sounds linked to a specific motor repertoire. Music provides an appropriate framework for further exploration of this issue. Three groups of participants (pianists, non-pianist musicians and non-musicians) were tested with a shape decision task where left-hand and right-hand responses were required; each visual stimulus was paired with an auditory task-irrelevant stimulus (high-pitched or low-pitched piano-timbre chords). Of the three groups, only pianists had longer reaction times for left-hand/high-pitched chords and right-hand/low-pitched chords associations. These findings are consistent with an auditory-motor effect elicited by pitch dimension, as only pianists show an interaction between motor responses and implicit pitch processing. This interaction is consistent with the canonical mapping of hand gestures and pitch dimension on the piano keyboard. The results are discussed within the ideo-motor theoretical framework offered by the Theory of Event Coding (Hommel et al. in Behav Brain Sci 24:849-937, 2001).

The insular cortex: a comparative perspective

The human insular cortex is involved in a variety of viscerosensory, visceromotor, and interoceptive functions, and plays a role in complex processes such as emotions, music, and language. Across mammals, the insula has considerable morphologic variability. We review the structure and connectivity of the insula in laboratory animals (mouse, domestic cat, macaque monkey), and we present original data on the morphology and cytoarchitecture of insular cortex in less common species including a large carnivore (the Atlantic walrus, Odobenus rosmarus), two artiodactyls (the pigmy hippopotamus, Hexaprotodon liberiensis, and the Western bongo, Tragelaphus eurycerus), two cetaceans (the beluga whale, Delphinapterus leucas, and the minke whale, Balaenoptera acutorostrata), and a sirenian (the Florida manatee, Trichechus manatus latirostris). The insula shows substantial variability in shape, extent, and gyral and sulcal patterns, as well as differences in laminar organization, cellular specialization, and structural association with the claustrum. Our observations reveal that the insular cortex is extremely variable among mammals. These differences could be related to the role exerted by specific and selective pressures on cortical structure during evolution. We conclude that it is not possible to identify a general model of organization for the mammalian insular cortex.

Towards a neural basis of music-evoked emotions

Music is capable of evoking exceptionally strong emotions and of reliably affecting the mood of individuals. Functional neuroimaging and lesion studies show that music-evoked emotions can modulate activity in virtually all limbic and paralimbic brain structures. These structures are crucially involved in the initiation, generation, detection, maintenance, regulation and termination of emotions that have survival value for the individual and the species. Therefore, at least some music-evoked emotions involve the very core of evolutionarily adaptive neuroaffective mechanisms. Because dysfunctions in these structures are related to emotional disorders, a better understanding of music-evoked emotions and their neural correlates can lead to a more systematic and effective use of music in therapy.

Emotional moments across time: a possible neural basis for time perception in the anterior insula

A model of awareness based on interoceptive salience is described, which has an endogenous time base that might provide a basis for the human capacity to perceive and estimate time intervals in the range of seconds to subseconds. The model posits that the neural substrate for awareness across time is located in the anterior insular cortex, which fits with recent functional imaging evidence relevant to awareness and time perception. The time base in this model is adaptive and emotional, and thus it offers an explanation for some aspects of the subjective nature of time perception. This model does not describe the mechanism of the time base, but it suggests a possible relationship with interoceptive afferent activity, such as heartbeat-related inputs.

Different categories of living and non-living sound-sources activate distinct cortical networks

With regard to hearing perception, it remains unclear as to whether, or the extent to which, different conceptual categories of real-world sounds and related categorical knowledge are differentially represented in the brain. Semantic knowledge representations are reported to include the major divisions of living versus non-living things, plus more specific categories including animals, tools, biological motion, faces, and places-categories typically defined by their characteristic visual features. Here, we used functional magnetic resonance imaging (fMRI) to identify brain regions showing preferential activity to four categories of action sounds, which included non-vocal human and animal actions (living), plus mechanical and environmental sound-producing actions (non-living). The results showed a striking antero-posterior division in cortical representations for sounds produced by living versus non-living sources. Additionally, there were several significant differences by category, depending on whether the task was category-specific (e.g. human or not) versus non-specific (detect end-of-sound). In general, (1) human-produced sounds yielded robust activation in the bilateral posterior superior temporal sulci independent of task. Task demands modulated activation of left lateralized fronto-parietal regions, bilateral insular cortices, and sub-cortical regions previously implicated in observation-execution matching, consistent with "embodied" and mirror-neuron network representations subserving recognition. (2) Animal action sounds preferentially activated the bilateral posterior insulae. (3) Mechanical sounds activated the anterior superior temporal gyri and parahippocampal cortices. (4) Environmental sounds preferentially activated dorsal occipital and medial parietal cortices. Overall, this multi-level dissociation of networks for preferentially representing distinct sound-source categories provides novel support for grounded cognition models that may underlie organizational principles for hearing perception.

Performed or observed keyboard actions affect pianists' judgements of relative pitch

Action can affect visual perception if the action's expected sensory effects resemble a concurrent unstable or deviant event. To determine whether action can also change auditory perception, participants were required to play pairs of octave-ambiguous tones by pressing successive keys on a piano or computer keyboard and to judge whether each pitch interval was rising or falling. Both pianists and nonpianist musicians gave significantly more "rising" responses when the order of key presses was left-to-right than when it was right-to-left, in accord with the pitch mapping of the piano. However, the effect was much larger in pianists. Pianists showed a similarly large effect when they passively observed the experimenter pressing keys on a piano keyboard, as long as the keyboard faced the participant. The results suggest that acquired action-effect associations can affect auditory perceptual judgement.

Functional organization of the human anterior insular cortex

The human insular cortex is involved in a wide range of functions including motor control, language, and homeostatic regulation. Little is known, however, how these functions are topographically organized in the insular cortex and how they are functionally related to the amygdala, which is anatomically connected to the insular cortex. We have investigated these questions by conducting an activation likelihood estimate (ALE) meta-analysis of previously published neuroimaging studies reporting insula effects. We find auditory and language tasks to preferentially activate an area in the dorsal part of the anterior insular cortex (AIC). Motor tasks involving both the upper and lower extremity reproducibly activated a posterior AIC region, adjacent to the sulcus centralis insulae (SCI). Significant co-activation with the probabilistically defined amygdala was located in the ventral AIC where also responses related to peripheral physiological changes were repeatedly reported. These findings show that the human AIC is a functionally differentiated brain region. The dorsal region of the AIC may be involved in auditory-motor integration, while the ventral part of the AIC may interface the amygdala with insular regions involved in the regulation of physiological changes related to emotional states. Thus, the present findings provide insights into the organization of human AIC and a methodological approach that may be further used to refine the emerging functional map of the insular cortex.

How do you feel--now? The anterior insula and human awareness

The anterior insular cortex (AIC) is implicated in a wide range of conditions and behaviours, from bowel distension and orgasm, to cigarette craving and maternal love, to decision making and sudden insight. Its function in the re-representation of interoception offers one possible basis for its involvement in all subjective feelings. New findings suggest a fundamental role for the AIC (and the von Economo neurons it contains) in awareness, and thus it needs to be considered as a potential neural correlate of consciousness.

The Neural Correlate of Speech Rhythm as Evidenced by Metrical Speech Processing

The present study investigates the neural correlates of rhythm processing in speech perception. German pseudosentences spoken with an exaggerated (isochronous) or a conversational (nonisochronous) rhythm were compared in an auditory functional magnetic resonance imaging experiment. The subjects had to perform either a rhythm task (explicit rhythm processing) or a prosody task (implicit rhythm processing). The study revealed bilateral activation in the supplementary motor area (SMA), extending into the cingulate gyrus, and in the insulae, extending into the right basal ganglia (neostriatum), as well as activity in the right inferior frontal gyrus (IFG) related to the performance of the rhythm task. A direct contrast between isochronous and nonisochronous sentences revealed differences in lateralization of activation for isochronous processing as a function of the explicit and implicit tasks. Explicit processing revealed activation in the right posterior superior temporal gyrus (pSTG), the right supramarginal gyrus, and the right parietal operculum. Implicit processing showed activation in the left supramarginal gyrus, the left pSTG, and the left parietal operculum. The present results indicate a function of the SMA and the insula beyond motor timing and speak for a role of these brain areas in the perception of acoustically temporal intervals. Secondly, the data speak for a specific task-related function of the right IFG in the processing of accent patterns. Finally, the data sustain the assumption that the right secondary auditory cortex is involved in the explicit perception of auditory suprasegmental cues and, moreover, that activity in the right secondary auditory cortex can be modulated by top-down processing mechanisms.

Neural correlates of simple unimanual discrete and continuous movements: a functional imaging study at 3 T

INTRODUCTION

The cerebral and cerebellar network involved in unimanual continuous and discrete movements was studied in blood oxygenation level-dependent functional magnetic resonance imaging (fMRI) at 3 T.

METHODS

Seven healthy right-handed volunteers were scanned (1) while drawing a circle with the tip of the right index finger (continuous motor task), and (2) while drawing a triangle with the tip of the right index finger (discrete motor task).

RESULTS

In both motor tasks, extensive activations were observed in the sensorimotor (M1/S1), parietal, prefrontal, insular, lateral occipital (LOC) and anterior cerebellar cortices. Subcortical activations within red, thalamic and lentiform nuclei were also detected. However, discrete movements were specifically followed by the recruitment of the left orbitofrontal cortex, right dentate nucleus and the second cerebellar homunculus (HVIII), and bilateral and stronger activation of the sensorimotor cortical areas, whereas continuous movements specifically activated the right prefrontal cortex and the lateral hemispherical part of the neocerebellum (crus 1).

CONCLUSION

We confirm the findings of previous studies showing partly distinct neural networks involved in monitoring continuous and discrete movements, but we found new differential neural relays within the prefrontal, insular and neocerebellar cortices.

How the brain laughs

Laughter is an affective nonspeech vocalization that is not reserved to humans, but can also be observed in other mammalians, in particular monkeys and great apes. This observation makes laughter an interesting subject for brain research as it allows us to learn more about parallels and differences of human and animal communication by studying the neural underpinnings of expressive and perceptive laughter. In the first part of this review we will briefly sketch the acoustic structure of a bout of laughter and relate this to the differential anatomy of the larynx and the vocal tract in human and monkey. The subsequent part of the article introduces the present knowledge on behavioral and brain mechanisms of "laughter-like responses" and other affective vocalizations in monkeys and apes, before we describe the scant evidence on the cerebral organization of laughter provided by neuroimaging studies. Our review indicates that a densely intertwined network of auditory and (pre-) motor functions subserves perceptive and expressive aspects of human laughter. Even though there is a tendency in the present literature to suggest a rightward asymmetry of the cortical representation of laughter, there is no doubt that left cortical areas are also involved. In addition, subcortical areas, namely the amygdala, have also been identified as part of this network. Furthermore, we can conclude from our overview that research on the brain mechanisms of affective vocalizations in monkeys and great apes report the recruitment of similar cortical and subcortical areas similar to those attributed to laughter in humans. Therefore, we propose the existence of equivalent brain representations of emotional tone in human and great apes. This reasoning receives support from neuroethological models that describe laughter as a primal behavioral tool used by individuals - be they human or ape - to prompt other individuals of a peer group and to create a mirthful context for social interaction and communication.

The neural network involved in a bimanual tactile-tactile matching discrimination task: a functional imaging study at 3 T

INTRODUCTION

The cerebral and cerebellar network involved in a bimanual object recognition was studied in blood oxygenation dependent level functional magnetic resonance imaging (fMRI).

METHODS

Nine healthy right-handed volunteers were scanned (1) while performing bilateral finger movements (nondiscrimination motor task), and (2) while performing a bimanual tactile-tactile matching discrimination task using small chess pieces (tactile discrimination task).

RESULTS

Extensive activations were specifically observed in the parietal (SII, superior lateral lobule), insular, prefrontal, cingulate and neocerebellar cortices (HVIII), with a left predominance in motor areas, during the tactile discrimination task in contrast to the findings during the nondiscrimination motor task.

CONCLUSION

Bimanual tactile-tactile matching discrimination recruits multiple sensorimotor and associative cerebral and neocerebellar networks (including the cerebellar second homunculus, HVIII), comparable to the neural circuits involved in unimanual tactile object recognition.