Functional organization of the lateral premotor cortex: fMRI reveals different regions activated by anticipation of object properties, location and speed

Hands off, brain off? A meta-analysis of neuroimaging data during active and passive driving

BACKGROUND

Car driving is more and more automated, to such an extent that driving without active steering control is becoming a reality. Although active driving requires the use of visual information to guide actions (i.e., steering the vehicle), passive driving only requires looking at the driving scene without any need to act (i.e., the human is passively driven).

MATERIALS & METHODS

After a careful search of the scientific literature, 11 different studies, providing 17 contrasts, were used to run a comprehensive meta-analysis contrasting active driving with passive driving.

RESULTS

Two brain regions were recruited more consistently for active driving compared to passive driving, the left precentral gyrus (BA3 and BA4) and the left postcentral gyrus (BA4 and BA3/40), whereas a set of brain regions was recruited more consistently in passive driving compared to active driving: the left middle frontal gyrus (BA6), the right anterior lobe and the left posterior lobe of the cerebellum, the right sub-lobar thalamus, the right anterior prefrontal cortex (BA10), the right inferior occipital gyrus (BA17/18/19), the right inferior temporal gyrus (BA37), and the left cuneus (BA17).

DISCUSSION

From a theoretical perspective, these findings support the idea that the output requirement of the visual scanning process engaged for the same activity can trigger different cerebral pathways, associated with different cognitive processes. A dorsal stream dominance was found during active driving, whereas a ventral stream dominance was obtained during passive driving. From a practical perspective, and contrary to the dominant position in the Human Factors community, our findings support the idea that a transition from passive to active driving would remain challenging as passive and active driving engage distinct neural networks.

Evaluation of abstract rule-based associations in the human premotor cortex during passive observation

Decision-making often manifests in behavior, typically yielding overt motor actions. This complex process requires the registration of sensory information with one's internal representation of the current context, before a categorical judgment of the most appropriate motor behavior can be issued. The construct concept of embodied decision-making encapsulates this sequence of complex processes, whereby behaviorally salient information from the environment is represented in an abstracted space of potential motor actions rather than only in an abstract cognitive "decision" space. Theoretical foundations and some empirical evidence account for support the involvement of premotor cortical circuits in embodied cognitive functions. Animal models show that premotor circuits participate in the registration and evaluation of actions performed by peers in social situations, that is, prior to controlling one's voluntary movements guided by arbitrary stimulus-response rules. However, such evidence from human data is currently limited. Here we used time-resolved magnetoencephalography imaging to characterize activations of the premotor cortex as human participants observed arbitrary, non-biological visual stimuli that either respected or violated a simple stimulus-response association rule. The participants had learned this rule previously, either actively, by performing a motor task (active learning), or passively, by observing a computer perform the same task (passive learning). We discovered that the human premotor cortex is activated during the passive observation of the correct execution of a sequence of events according to a rule learned previously. Premotor activation also differs when the subjects observe incorrect stimulus sequences. These premotor effects are present even when the observed events are of a non-motor, abstract nature, and even when the stimulus-response association rule was learned via passive observations of a computer agent performing the task, without requiring overt motor actions from the human participant. We found evidence of these phenomena by tracking cortical beta-band signaling in temporal alignment with the observation of task events and behavior. We conclude that premotor cortical circuits that are typically engaged during voluntary motor behavior are also involved in the interpretation of events of a non-ecological, unfamiliar nature but related to a learned abstract rule. As such, the present study provides the first evidence of neurophysiological processes of embodied decision-making in human premotor circuits when the observed events do not involve motor actions of a third party.

Driver's turning intent recognition model based on brain activation and contextual information

Traffic situations like turning at intersections are destined for safety-critical situations and accidents. Human errors are one of the main reasons for accidents in these situations. A model that recognizes the driver's turning intent could help to reduce accidents by warning the driver or stopping the vehicle before a dangerous turning maneuver. Most models that aim at predicting the probability of a driver's turning intent use only contextual information, such as gap size or waiting time. The objective of this study is to investigate whether the combination of context information and brain activation measurements enhances the recognition of turning intent. We conducted a driving simulator study while simultaneously measuring brain activation using high-density fNIRS. A neural network model for turning intent recognition was trained on the fNIRS and contextual data. The input variables were analyzed using SHAP (SHapley Additive exPlanations) feature importance analysis to show the positive effect of the inclusion of brain activation data. Both the model's evaluation and the feature importance analysis suggest that the combination of context information and brain activation leads to an improved turning intent recognition. The fNIRS results showed increased brain activation differences during the "turn" decision-making phase before turning execution in parts of the left motor cortices, such as the primary motor cortex (PMC; putative BA 4), premotor area (PMA; putative BA 6), and supplementary motor area (SMA; putative BA 8). Furthermore, we also observed increased activation differences in the left prefrontal areas, potentially in the left middle frontal gyrus (putative BA 9), which has been associated with the control of executive functions, such as decision-making and action planning. We hypothesize that brain activation measurements could be a more direct indicator with potentially high specificity for the turning behavior and thus help to increase the recognition model's performance.

[Mirror neurons, neural substrate of action understanding?]

In 1992, the Laboratory of Human Physiology at the University of Parma (Italy) publish a study describing "mirror" neurons in the macaque that activate both when the monkey performs an action and when it observes an experimenter performing the same action. The research team behind this discovery postulates that the mirror neurons system is the neural basis of our ability to understand the actions of others, through the motor mapping of the observed action on the observer's motor repertory (direct-matching hypothesis). Nevertheless, this conception met serious criticism. These critics attempt to relativize their function by placing them within a network of neurocognitive and sensory interdependencies. In short, the essential characteristic of these neurons is to combine the processing of sensory information, especially visual, with that of motor information. Their elementary function would be to provide a motor simulation of the observed action, based on visual information from it. They can contribute, with other non-mirror areas, to the identification/prediction of the action goal and to the interpretation of the intention of the actor performing it. Studying the connectivity and high frequency synchronizations of the different brain areas involved in action observation would likely provide important information about the dynamic contribution of mirror neurons to "action understanding". The aim of this review is to provide an up-to-date analysis of the scientific evidence related to mirror neurons and their elementary functions, as well as to shed light on the contribution of these neurons to our ability to interpret and understand others' actions.

The influence of auditory rhythms on the speed of inferred motion

The present research explored the influence of isochronous auditory rhythms on the timing of movement-related prediction in two experiments. In both experiments, participants observed a moving disc that was visible for a predetermined period before disappearing behind a small, medium, or large occluded area for the remainder of its movement. In Experiment 1, the disc was visible for 1 s. During this period, participants were exposed to either a fast or slow auditory rhythm, or they heard nothing. They were instructed to press a key to indicate when they believed the moving disc had reached a specified location on the other side of the occluded area. The procedure measured the (signed) error in participants' estimate of the time it would take for a moving object to contact a stationary one. The principal results of Experiment 1 were main effects of the rate of the auditory rhythm and of the size of the occlusion on participants' judgments. In Experiment 2, the period of visibility was varied with size of the occlusion area to keep the total movement time constant for all three levels of occlusion. The results replicated the main effect of rhythm found in Experiment 1 and showed a small, significant interaction, but indicated no main effect of occlusion size. Overall, the results indicate that exposure to fast isochronous auditory rhythms during an interval of inferred motion can influence the imagined rate of such motion and suggest a possible role of an internal rhythmicity in the maintenance of temporally accurate dynamic mental representations.

Larger Volume and Different Activation of the Brain in Response to Threat in Military Officers

Introduction:

Military missions involve stressful and life-threatening situations; however, soldiers should have a healthy cognition on the battlefield despite their high-stress levels. This is an ability that should be gained during prior military training. Successful and influential training is suggested to be associated with structural and functional improvements of the brain.

Methods:

This study investigated the pattern of brain activation while observing videos relevant to life-threatening situations, in addition to brain structure. Accordingly, the obtained data were compared between 20 military members and 26 healthy controls. The study participants were all male, aged between 19 to 24 years, right-handed, studying BSc, and from the same socioeconomic status.

Results:

The obtained data presented a larger volume in a total number of 1103 voxels of the brain (in 5 brain areas) in the military group. Furthermore, the military group suggested higher brain activation in the visual processing areas of the brain when observing real combat videos; however, this increment was mostly in the areas associated with motor processing and executive functions in the controls.

Conclusion:

This study indicated that military training is associated with positive structural changes in the brain. Besides, it provided a different brain activation in response to stressful situations. These findings highlighted the importance of qualified military training.

Cortical presentation of language functions in patients after total laryngectomy: a fMRI study

Purpose

The aim of this study is to use functional magnetic resonance (fMRI) to analyse the cortical presentation of selected language functions in patients after a total laryngectomy.

Methods

Eighteen patients after total laryngectomy treated with electrolarynx speech and 18 volunteers were included. The mean number of patients’ post-operative speech rehabilitation sessions was five (range of 3–8 sessions). Four paradigms were used, including noun generation, pseudoword reading, reading phrases with pseudowords, and nonliteral sign reproduction.

Results

In noun, the most significant difference between the groups was the stronger activation of both lingual gyri in the volunteers. Pseudoword reading resulted in stronger activations in patients than in volunteers in the lingual gyri, the right cerebellum, the right Broca’s area, and the right parietal operculum. Reading phrases with pseudowords involved different parts of the Brodmann area 40. During nonliteral sign reproduction, there was a stronger activation of the left Broca’s area in volunteers and a stronger activation of the left premotor cortex in patients.

Conclusion

This study provides evidence of altered cortical activation in response to language tasks in patients after a laryngectomy compared with healthy volunteers, which may be considered brain plasticity in response to a laryngectomy.

Shared premotor activity in spoken and written communication

The aim of the present study was to uncover a possible common neural organizing principle in spoken and written communication, through the coupling of perceptual and motor representations. In order to identify possible shared neural substrates for processing the basic units of spoken and written language, a sparse sampling fMRI acquisition protocol was performed on the same subjects in two experimental sessions with similar sets of letters being read and written and of phonemes being heard and orally produced. We found evidence of common premotor regions activated in spoken and written language, both in perception and in production. The location of those brain regions was confined to the left lateral and medial frontal cortices, at locations corresponding to the premotor cortex, inferior frontal cortex and supplementary motor area. Interestingly, the speaking and writing tasks also appeared to be controlled by largely overlapping networks, possibly indicating some domain general cognitive processing. Finally, the spatial distribution of individual activation peaks further showed more dorsal and more left-lateralized premotor activations in written than in spoken language.

Action, observation or imitation of virtual hand movement affect differently regions of the mirror neuron system and the default mode network

Virtual reality (VR)-based paradigms use visual stimuli that can modulate visuo-motor networks leading to the stimulation of brain circuits. The aims of this study were to compare the changes in blood-oxygenation level dependent (BOLD) signal when watching and imitating moving real (RH) and virtual hands (VH) in 11 healthy participants (HP). No differences were found between the observation of RH or VH making this VR-based experiment a promising tool for rehabilitation protocols. VH-imitation involved more the ventral premotor cortex (vPMC) as part of the mirror neuron system (MNS) compared to execution and VH-observation conditions. The dorsal-anterior Precuneus (da-Pcu) as part of the Precuneus/posterior Cingulate Cortex (Pcu/pCC) complex, a key node of the Default Mode Network (DMN), was also less deactivated and therefore more involved. These results may reflect the dual visuo-motor roles for the vPMC and the implication of the da-Pcu in the reallocation of attentional and neural resources for bimodal task management. The ventral Pcu/pCC was deactivated regardless of the condition confirming its role in self-reference processes. Imitation of VH stimuli can then modulate the activation of specific areas including those belonging to the MNS and the DMN.

Spontaneous Brain Activity Predicts Task-Evoked Activity During Animate Versus Inanimate Touch

The spontaneous activity of the brain is characterized by an elaborate temporal structure with scale-free properties as indexed by the power law exponent (PLE). We test the hypothesis that spontaneous brain activity modulates task-evoked activity during interactions with animate versus inanimate stimuli. For this purpose, we developed a paradigm requiring participants to actively touch either animate (real hand) or inanimate (mannequin hand) stimuli. Behaviorally, participants perceived the animate target as closer in space, temporally more synchronous with their own self, and more personally relevant, compared with the inanimate. Neuronally, we observed a modulation of task-evoked activity by animate versus inanimate interactions in posterior insula, in medial prefrontal cortex, comprising anterior cingulate cortex, and in medial superior frontal gyrus. Among these regions, an increased functional connectivity was shown between posterior insula and perigenual anterior cingulate cortex (PACC) during animate compared with inanimate interactions and during resting state. Importantly, PLE during spontaneous brain activity in PACC correlated positively with PACC task-evoked activity during animate versus inanimate stimuli. In conclusion, we demonstrate that brain spontaneous activity in PACC can be related to the distinction between animate and inanimate stimuli and thus might be specifically tuned to align our brain with its animate environment.

Get a grip: individual variations in grip strength are a marker of brain health

Demonstrations that grip strength has predictive power in relation to a range of health conditions-even when these are assessed decades later-has motivated claims that hand-grip dynamometry has the potential to serve as a "vital sign" for middle-aged and older adults. Central to this belief has been the assumption that grip strength is a simple measure of physical performance that provides a marker of muscle status in general, and sarcopenia in particular. It is now evident that while differences in grip strength between individuals are influenced by musculoskeletal factors, "lifespan" changes in grip strength within individuals are exquisitely sensitive to integrity of neural systems that mediate the control of coordinated movement. The close and pervasive relationships between age-related declines in maximum grip strength and expressions of cognitive dysfunction can therefore be understood in terms of the convergent functional and structural mediation of cognitive and motor processes by the human brain. In the context of aging, maximum grip strength is a discriminating measure of neurological function and brain health.

High-precision voluntary movements are largely independent of preceding vertex potentials elicited by sudden sensory events

KEY POINTS

Salient and sudden sensory events generate a remarkably large response in the human brain, the vertex wave (VW). The VW is coupled with a modulation of a voluntarily-applied isometric force. In the present study, we tested whether the VW is also related to executing high-precision movements. The execution of a voluntary high-precision movement remains relatively independent of the brain activity reflected by the preceding VW. The apparent relationship between the positive VW and movement onset time is explained by goal-related but stimulus-independent neural activities. These results highlight the need to consider such goal-related but stimulus-independent neural activities when attempting to relate event-related potential amplitude with perceptual and behavioural performance.

ABSTRACT

Salient and fast-rising sensory events generate a large biphasic vertex wave (VW) in the human electroencephalogram (EEG). We recently reported that the VW is coupled with a modulation of concomitantly-applied isometric force. In the present study, in five experiments, we tested whether the VW is also related to high-precision visuomotor control. We obtained three results. First, the saliency-induced increase in VW amplitude was paralleled by a modulation in two of the five extracted movement parameters: a reduction in the onset time of the voluntary movement (P < 0.005) and an increase in movement accuracy (P < 0.005). Second, spontaneous trial-by-trial variability in vertex wave amplitude, for a given level of stimulus saliency, was positively correlated with movement onset time (P < 0.001 in four out of five experiments). Third, this latter trial-by-trial correlation was explained by a widespread EEG negativity independent of the occurrence of the positive VW, although overlapping in time with it. These results indicate that (i) the execution of a voluntary high-precision movement remains relatively independent of the neural processing reflected by the preceding VW, with (ii) the exception of movement onset time, for which saliency-based contextual effects are dissociated from trial-by-trial effects. These results also indicate that (iii) attentional effects can produce spurious correlations between event-related potentials (ERPs) and behavioural measures. Although sudden salient stimuli trigger characteristic EEG responses coupled with distinct reactive components within an ongoing isometric task, the results of the present study indicate that the execution of a subsequent voluntary movement appears largely protected from such saliency-based modulation, with the exception of movement onset time.

Symbol Digit Modalities Test adaptation for Magnetic Resonance Imaging environment: A systematic review and meta-analysis

BACKGROUND

The Symbol Digit Modalities Test (SDMT) is widely used for cognitive evaluation of information processing speed (IPS), required in many cognitive operations. Despite being unspecific for different neurological disorders, it is sensitive to assess impaired performance related to stroke, Parkinson's disease, traumatic brain injury, and multiple sclerosis. However, in addition to evaluate the presence and severity of IPS impairment, it is of interest to determine the localization and integration of brain regions responsible for the functions assessed by the SDMT.

OBJECTIVE

To review the studies that adapted the SDMT to the magnetic resonance environment and obtain the brain areas associated with the performance of the task in healthy subjects with a meta-analysis.

METHODOLOGY

A systematic review was performed using ten studies published between 1990 and 2017, and selected from four databases. All studies included participants of both genders and age between 18 and 50 years, used Functional Magnetic Resonance Imaging (fMRI) and SDMT adaptation and reported brain regions associated with the task. Six of them also reported the region coordinates in a standard space, so they were included in a meta-analysis. Activation Likelihood Estimation algorithm, with significance for p < 0.05 corrected for multiple comparisons, was used to identify areas that are robustly related to the performance of the SDMT.

RESULTS

The areas predominantly reported in the studies of our meta-analysis were regions of the frontoparietal attentional network and occipital cortex, as well as cuneus, precuneus, and cerebellum. Individually all regions that survived the statistical threshold are consistent with what is expected after reviewing prospective studies.

CONCLUSIONS

The present study allowed the identification of brain areas activated during the performance of the SDMT in healthy subjects, and therefore it will help understanding the differences in brain activation by this task in clinical populations. Moreover, it may guide future studies of therapeutic strategies and interventions in those populations.

Action-feature integration blinds to feature-overlapping perceptual events: Evidence from manual and vocal actions

Previous studies showed that the identification of a left- or right-pointing arrowhead is impaired when it appears while planning and executing a spatially compatible left or right keypress (Müsseler & Hommel, 1997a). We attribute this effect to stimulus processing and action control operating on the same feature codes so that, once a code is integrated in an action plan, it is less available for perceptual processing. In three pairs of experiments we tested the generality of this account by using stimulus–response combinations other than arrows and manual keypresses. Planning manual left–right keypressing actions impaired the identification of spatially corresponding arrows but not of words with congruent meaning. On the contrary, planning to say “left” or “right” impaired the identification of corresponding spatial words but not of congruent arrows. Thus, as the feature-integration approach suggests, stimulus identification is impaired only with overlap of perceptual or perceptually derived stimulus and response features while mere semantic congruence is insufficient.

High-resolution language mapping of Broca's region with transcranial magnetic stimulation

Broca's region, corresponding roughly to cytoarchitectonic areas 44 and 45 in the inferior frontal cortex, holds a multifunctional role in language processing, as shown, e.g., by functional imaging data. Neuro-navigated transcranial magnetic stimulation (TMS) enables complementary non-invasive mapping of cortical functions with high spatial resolution. Here, we report on detailed TMS language mapping of Broca's region in 12 healthy participants. The test protocol with an object naming task was adapted for high-resolution and semi-quantitative mapping of TMS-induced effects on speech and language performance. Hierarchical cluster analysis of normalized ratings of error frequency and severity revealed a clear focus of TMS impact at dorso-posterior target sites, close to the inferior frontal junction. Adjacent clusters of moderate and slightly affected stimulation sites yielded a posterosuperior-to-anteroinferior gradient of TMS susceptibility. Our findings indicate that the part of Broca's region most susceptible to TMS-induced language inhibition in object naming is located in the dorsal area 44.

Time-based expectations entail preparatory motor activity

Human behavior is guided by expectations that facilitate perception of upcoming events or reaction to them. In natural settings expectations are often implicitly based on time, e.g., when making a phone call one would expect to hear either a person answering (earlier) or a voicemail greeting (later). We investigated how time-based expectations can improve performance in the absence of explicit prior information on the pending stimulus or the associated response. Visual stimuli were presented after a characteristic short or long foreperiod, and a forced-choice categorization using either the left or the right hand was required. The electroencephalogram (EEG) revealed a decrease in central 9-12 Hz power over the course of the trial. Moreover, lateralized pre-motor potentials were observed which changed polarity after the short foreperiod. At stimulus onset, amplitudes of pre-motor potentials co-varied with performance, so that higher (more negative) amplitudes were associated with slower responses to unexpected targets. Altogether, the results suggest that implicit time-based expectations entail effector-specific preparatory brain activity, which is inhibited until the expected onset time of the event. Thus, time-based expectations prepare for action.

Applying fMRI complexity analyses to the single subject: a case study for proposed neurodiagnostics

Nonlinear dynamic tools have been statistically validated at the group level to identify subtle differences in system wide regulation of brain meso-circuits, often increasing clinical sensitivity over conventional analyses alone. We explored the feasibility of extracting information at the single-subject level, illustrating two pairs of healthy individuals with psychological differences in stress reactivity. We applied statistical and nonlinear dynamic tools to capture key characteristics of the prefrontal-limbic loop. We compared single subject results with statistical results for the larger group. We concluded that complexity analyses may identify important differences at the single-subject level, supporting their potential towards neurodiagnostic applications.

Cerebral Functional Response during Eyelid Opening/Closing with Bell's Phenomenon and Volitional Vertical Eye Movements in Humans

Bell's phenomenon is a physiological phenomenon wherein the eye ball involuntarily rolls upward during eyelid closing. Although this phenomenon occurs in healthy individuals, the neural mechanism related to Bell's phenomenon has not yet been identified. We aimed to investigate the brain regions relevant to Bell's phenomenon and volitional eye movement using [¹⁵O] H₂O and positron emission tomography (PET). We measured regional cerebral blood flow (rCBF) in 8 normal subjects under 3 conditions: at rest with eyes closed, during opening and closing of the eyelids in response to sound stimuli (lid opening/closing), and during vertical movement of the eyes with lids closed in response to sound stimuli (volitional eye movement). The supplementary motor area (SMA) proper, right superior temporal gyrus, right insular cortex and left angular gyrus were activated during lid opening/closing. The right frontal eye field (FEF), pre-SMA, left primary motor area, right angular gyrus, and SMA proper were activated during volitional eye movement. The SMA proper was active during both tasks, while the FEF and pre-SMA were active during volitional eye movement, but not during eyelid opening/closing. A comparison of activation during volitional eye movements and lid opening/closing tasks revealed a relative increase in rCBF in the FEF. There were no areas that are activated in relation to Bell's phenomenon. In conclusion, activation in the FEF mainly occurs during volitional eye movement. Since Bell's phenomenon is a reflexive eye movement, the FEF is scarcely concerned in Bell's phenomenon.

Disambiguating ambiguous motion perception: what are the cues?

Motion perception is a fundamental feature of the human visual system. As part of our daily life we often have to determine the direction of motion, even in ambiguous (AMB) situations. These situations force us to rely on exogenous cues, such as other environmental motion, and endogenous cues, such as our own actions, or previously learned experiences. In three experiments, we asked participants to report the direction of an AMB motion display, while manipulating exogenous and endogenous sources of information. Specifically, in all three experiments the exogenous information was represented by another motion cue while the endogenous cue was represented, respectively, by movement execution, movement planning, or a learned association about the motion display. Participants were consistently biased by less AMB motion cues in the environment when reporting the AMB target direction. In the absence of less AMB exogenous motion information, participants were biased by their motor movements and even the planning of such movements. However, when participants learned a specific association about the target motion, this acquired endogenous knowledge countered exogenous motion cues in biasing participants’ perception. Taken together, our findings demonstrate that we disambiguate AMB motion using different sources of exogenous and endogenous cues, and that learned associations may be particularly salient in countering the effects of environmental cues.

The Potentiation of Associative Memory by Emotions: An Event-Related FMRI Study

Establishing associations between pieces of information is related to the medial temporal lobe (MTL). However, it remains unclear how emotions affect memory for associations and, consequently, MTL activity. Thus, this event-related fMRI study attempted to identify neural correlates of the influence of positive and negative emotions on associative memory. Twenty-five participants were instructed to memorize 90 pairs of standardized pictures during a scanned encoding phase. Each pair was composed of a scene and an unrelated object. Trials were neutral, positive, or negative as a function of the emotional valence of the scene. At the behavioral level, participants exhibited better memory retrieval for both emotional conditions relative to neutral trials. Within the right MTL, a functional dissociation was observed, with entorhinal activation elicited by emotional associations, posterior parahippocampal activation elicited by neutral associations, and hippocampal activation elicited by both emotional and neutral associations. In addition, emotional associations induced greater activation than neutral trials in the right amygdala. This fMRI study shows that emotions are associated with the performance improvement of associative memory, by enhancing activity in the right amygdala and the right entorhinal cortex. It also provides evidence for a rostrocaudal specialization within the MTL regarding the emotional valence of associations.

Functional specificity in the motor system: Evidence from coupled fMRI and kinematic recordings during letter and digit writing

A few intriguing neuropsychologial studies report dissociations where agraphic patients are severely impaired for writing letters whereas they write digits nearly normally. Here, using functional magnetic resonance imaging (fMRI) together with graphic tablet recordings, we tested the hypothesis that the motor patterns for writing letters are coded in specific regions of the cortex. We found a set of three regions that were more strongly activated when participants wrote letters than when they wrote digits and whose response was not explained by low-level kinematic features of the graphic movements. Two of these regions (left dorsal premotor cortex and supplementary motor complex) are part of a motor control network. The left premotor activation belongs to what is considered in the literature a key area for handwriting. Another significant activation, likely related to phoneme-to-grapheme conversion, was found in the right anterior insula. This constitutes the first neuroimaging evidence of functional specificity derived from experience in the cortical motor system.

Oscillatory motor network activity during rest and movement: an fNIRS study

Coherent network oscillations (<0.1 Hz) linking distributed brain regions are commonly observed in the brain during both rest and task conditions. What oscillatory network exists and how network oscillations change in connectivity strength, frequency and direction when going from rest to explicit task are topics of recent inquiry. Here, we study network oscillations within the sensorimotor regions of able-bodied individuals using hemodynamic activity as measured by functional near-infrared spectroscopy (fNIRS). Using spectral interdependency methods, we examined how the supplementary motor area (SMA), the left premotor cortex (LPMC) and the left primary motor cortex (LM1) are bound as a network during extended resting state (RS) and between-tasks resting state (btRS), and how the activity of the network changes as participants execute left, right, and bilateral hand (LH, RH, and BH) finger movements. We found: (i) power, coherence and Granger causality (GC) spectra had significant peaks within the frequency band (0.01-0.04 Hz) during RS whereas the peaks shifted to a bit higher frequency range (0.04-0.08 Hz) during btRS and finger movement tasks, (ii) there was significant bidirectional connectivity between all the nodes during RS and unidirectional connectivity from the LM1 to SMA and LM1 to LPMC during btRS, and (iii) the connections from SMA to LM1 and from LPMC to LM1 were significantly modulated in LH, RH, and BH finger movements relative to btRS. The unidirectional connectivity from SMA to LM1 just before the actual task changed to the bidirectional connectivity during LH and BH finger movement. The uni-directionality could be associated with movement suppression and the bi-directionality with preparation, sensorimotor update and controlled execution. These results underscore that fNIRS is an effective tool for monitoring spectral signatures of brain activity, which may serve as an important precursor before monitoring the recovery progress following brain injury.

Sensory-guided motor tasks benefit from mental training based on serial prediction

Mental strategies have been suggested to constitute a promising approach to improve motor abilities in both healthy subjects and patients. This behavioural effect has been shown to be associated with changes of neural activity in premotor areas, not only during movement execution, but also while performing motor imagery or action observation. However, how well such mental tasks are performed is often difficult to assess, especially in patients. We here used a novel mental training paradigm based on the serial prediction task (SPT) in order to activate premotor circuits in the absence of a motor task. We then tested whether this intervention improves motor-related performance such as sensorimotor transformation. Two groups of healthy young participants underwent a single-blinded five-day cognitive training schedule and were tested in four different motor tests on the day before and after training. One group (N=22) received the SPT-training and the other one (N=21) received a control training based on a serial match-to-sample task. The results revealed significant improvements of the SPT-group in a sensorimotor timing task, i.e. synchronization of finger tapping to a visually presented rhythm, as well as improved visuomotor coordination in a sensory-guided pointing task compared to the group that received the control training. However, mental training did not show transfer effects on motor abilities in healthy subjects beyond the trained modalities as evident by non-significant changes in the Jebsen-Taylor handfunctiontest. In summary, the data suggest that mental training based on the serial prediction task effectively engages sensorimotor circuits and thereby improves motor behaviour.

Neural dynamics of speech act comprehension: an MEG study of naming and requesting

The neurobiological basis and temporal dynamics of communicative language processing pose important yet unresolved questions. It has previously been suggested that comprehension of the communicative function of an utterance, i.e. the so-called speech act, is supported by an ensemble of neural networks, comprising lexico-semantic, action and mirror neuron as well as theory of mind circuits, all activated in concert. It has also been demonstrated that recognition of the speech act type occurs extremely rapidly. These findings however, were obtained in experiments with insufficient spatio-temporal resolution, thus possibly concealing important facets of the neural dynamics of the speech act comprehension process. Here, we used magnetoencephalography to investigate the comprehension of Naming and Request actions performed with utterances controlled for physical features, psycholinguistic properties and the probability of occurrence in variable contexts. The results show that different communicative actions are underpinned by a dynamic neural network, which differentiates between speech act types very early after the speech act onset. Within 50–90 ms, Requests engaged mirror-neuron action-comprehension systems in sensorimotor cortex, possibly for processing action knowledge and intentions. Still, within the first 200 ms of stimulus onset (100–150 ms), Naming activated brain areas involved in referential semantic retrieval. Subsequently (200–300 ms), theory of mind and mentalising circuits were activated in medial prefrontal and temporo-parietal areas, possibly indexing processing of intentions and assumptions of both communication partners. This cascade of stages of processing information about actions and intentions, referential semantics, and theory of mind may underlie dynamic and interactive speech act comprehension.

Prediction processes during multiple object tracking (MOT): involvement of dorsal and ventral premotor cortices

BACKGROUND

The multiple object tracking (MOT) paradigm is a cognitive task that requires parallel tracking of several identical, moving objects following nongoal-directed, arbitrary motion trajectories.

AIMS

The current study aimed to investigate the employment of prediction processes during MOT. As an indicator for the involvement of prediction processes, we targeted the human premotor cortex (PM). The PM has been repeatedly implicated to serve the internal modeling of future actions and action effects, as well as purely perceptual events, by means of predictive feedforward functions.

MATERIALS AND METHODS

Using functional magnetic resonance imaging (fMRI), BOLD activations recorded during MOT were contrasted with those recorded during the execution of a cognitive control task that used an identical stimulus display and demanded similar attentional load. A particular effort was made to identify and exclude previously found activation in the PM-adjacent frontal eye fields (FEF).

RESULTS

We replicated prior results, revealing occipitotemporal, parietal, and frontal areas to be engaged in MOT.

DISCUSSION

The activation in frontal areas is interpreted to originate from dorsal and ventral premotor cortices. The results are discussed in light of our assumption that MOT engages prediction processes.

CONCLUSION

We propose that our results provide first clues that MOT does not only involve visuospatial perception and attention processes, but prediction processes as well.

Intentional weighting: a basic principle in cognitive control

Human perception and action are tailored to the situation at hand, and thus reflect the current intentions of the perceiver/actor. We suggest that this is achieved by an "intentional-weighting" mechanism. It operates on the cognitive representations of the features of perceived events and produced event--perceptions and actions that is. Intention- or goal-related feature dimensions are weighted more strongly, so that feature values defined on the respective dimension have a stronger impact on information processing, and stimulus and response selection in particular. This article discusses what intentional weighting is, how such a mechanism may work, and how it relates to available research on attention, action planning, and executive control.

Neural simulation of actions: effector- versus action-specific motor maps within the human premotor and posterior parietal area?

This study addresses the controversy over how motor maps are organized during action simulation by examining whether action simulation states, that is, motor imagery and action observation, run on either effector-specific and/or action-specific motor maps. Subjects had to observe or imagine three types of movements effected by the right hand or the right foot with different action goals. The functional magnetic resonance imaging results showed an action-specific organization within premotor and posterior parietal areas of both hemispheres during action simulation, especially during action observation. There were also less pronounced effector-specific activation sites during both simulation processes. It is concluded that the premotor and parietal areas contain multiple motor maps rather than a single, continuous map of the body. The forms of simulation (observation, imagery), the task contexts (movements related to an object, with usual/unusual effector), and the underlying reason for performing the simulation (rate your subjective success afterwards) lead to the specific use of different representational motor maps within both regions. In our experimental setting, action-specific maps are dominant especially, during action observation, whereas effector-specific maps are recruited to only a lesser degree.

On the anticipatory precue activity in motor cortex

Motor cortical neurons are activated during movement preparation and execution, and in response to task-relevant visual cues. A few studies also report activation before the expected presentation of cues. Here, we study specifically this anticipatory activity preceding visual cues in motor cortical areas. We recorded the activity of 1215 neurons in the motor cortex of two macaque monkeys while they performed a center-out reaching task, including two consecutive delays of equal duration, known in advance. During the first delay (D1), they had to await the spatial cue and only reach to the cued target after the second delay (D2). Forty-two percent of the neurons displayed anticipatory activity during D1. Among these anticipatory neurons, 59% increased (D1up) their activity and the remaining decreased (D1down) their activity. By classifying the neurons according to these firing rate profiles during D1, we found that the activity during D2 differed in a systematic way. The D1up neurons were more likely to discharge phasically soon after the spatial cue and were less active during movement execution, whereas the D1down neurons showed the opposite pattern. But, regardless of their temporal activity profiles, the two categories seemed equally involved in early and late motor preparation, as reflected in their directional selectivity. This precue activity in motor cortex may reflect two complementary, coexisting processes: the facilitation of incoming spatial information in parallel with the downregulation of corticospinal excitability to prevent a premature response.

An approach to separating the levels of hierarchical structure building in language and mathematics

We aimed to dissociate two levels of hierarchical structure building in language and mathematics, namely 'first-level' (the build-up of hierarchical structure with externally given elements) and 'second-level' (the build-up of hierarchical structure with internally represented elements produced by first-level processes). Using functional magnetic resonance imaging, we investigated these processes in three domains: sentence comprehension, arithmetic calculation (using Reverse Polish notation, which gives two operands followed by an operator) and a working memory control task. All tasks required the build-up of hierarchical structures at the first- and second-level, resulting in a similar computational hierarchy across language and mathematics, as well as in a working memory control task. Using a novel method that estimates the difference in the integration cost for conditions of different trial durations, we found an anterior-to-posterior functional organization in the prefrontal cortex, according to the level of hierarchy. Common to all domains, the ventral premotor cortex (PMv) supports first-level hierarchy building, while the dorsal pars opercularis (POd) subserves second-level hierarchy building, with lower activation for language compared with the other two tasks. These results suggest that the POd and the PMv support domain-general mechanisms for hierarchical structure building, with the POd being uniquely efficient for language.

Tempo mediates the involvement of motor areas in beat perception

Increasing evidence shows that the neural circuits involved in beat perception overlap with motor circuitry even in the absence of overt movement. This study investigated effects of tempo on beat-based processing by combining functional magnetic resonance imaging with a perceptual timing paradigm where participants made simple temporal judgments about short rhythmic sequences. Of central interest were judgments about ambiguous test rhythms where the perceived direction of a timing deviation ("speeding up" vs. "slowing down") depended on the induction of an implied beat. Successful beat induction was reduced when the implied beat was at a slower tempo (1,500 ms) than when it was at a faster tempo (600 ms). Decreased beat induction was accompanied by decreased functional activity in the basal ganglia, premotor and supplementary motor regions, and thalamus. Findings support the conclusion that rhythms presented at a slow tempo reduce involvement of a striato-thalamo-cortico network in beat-based processing.

Bidirectional gray matter changes after complex motor skill learning

Long-term motor skill learning has been consistently shown to result in functional as well as structural changes in the adult human brain. However, the effect of short learning periods on brain structure is not well understood. In the present study, subjects performed a sequential pinch force task (SPFT) for 20 min on 5 consecutive days. Changes in brain structure were evaluated with anatomical magnetic resonance imaging (MRI) scans acquired on the first and last day of motor skill learning. Behaviorally, the SPFT resulted in sequence-specific learning with the trained (right) hand. Structural gray matter (GM) alterations in left M1, right ventral premotor cortex (PMC) and right dorsolateral prefrontal cortex (DLPFC) correlated with performance improvements in the SPFT. More specifically we found that subjects with strong sequence-specific performance improvements in the SPFT also had larger increases in GM volume in the respective brain areas. On the other hand, subjects with small behavioral gains either showed no change or even a decrease in GM volume during the time course of learning. Furthermore, cerebellar GM volume before motor skill learning predicted (A) individual learning-related changes in the SPFT and (B) the amount of structural changes in left M1, right ventral PMC and DLPFC. In summary, we provide novel evidence that short-term motor skill learning is associated with learning-related structural brain alterations. Additionally, we showed that practicing a motor skill is not exclusively accompanied by increased GM volume. Instead, bidirectional structural alterations explained the variability of the individual learning success.

Visual and audiovisual effects of isochronous timing on visual perception and brain activity

Understanding how the brain extracts and combines temporal structure (rhythm) information from events presented to different senses remains unresolved. Many neuroimaging beat perception studies have focused on the auditory domain and show the presence of a highly regular beat (isochrony) in “auditory” stimulus streams enhances neural responses in a distributed brain network and affects perceptual performance. Here, we acquired functional magnetic resonance imaging (fMRI) measurements of brain activity while healthy human participants performed a visual task on isochronous versus randomly timed “visual” streams, with or without concurrent task-irrelevant sounds. We found that visual detection of higher intensity oddball targets was better for isochronous than randomly timed streams, extending previous auditory findings to vision. The impact of isochrony on visual target sensitivity correlated positively with fMRI signal changes not only in visual cortex but also in auditory sensory cortex during audiovisual presentations. Visual isochrony activated a similar timing-related brain network to that previously found primarily in auditory beat perception work. Finally, activity in multisensory left posterior superior temporal sulcus increased specifically during concurrent isochronous audiovisual presentations. These results indicate that regular isochronous timing can modulate visual processing and this can also involve multisensory audiovisual brain mechanisms.

Visual and auditory stimuli associated with swallowing activate mirror neurons: a magnetoencephalography study

In the present study, we evaluated activated areas of the cerebral cortex with regard to the mirror neuron system during swallowing. To identify the activated areas, we used magnetoencephalography. Subjects were ten consenting volunteers. Swallowing-related stimuli comprised an animated image of the left profile of a person swallowing water with laryngeal elevation as a visual swallowing trigger stimulus and a swallowing sound as an auditory swallowing trigger stimulus. As control stimuli, a still frame image of the left profile without an additional trigger was shown, and an artificial sound as a false auditory trigger was provided. Triggers were presented at 3,000 ms after the start of image presentation. The stimuli were combined and presented and the areas activated were identified for each stimulus. With animation and still-frame stimuli, the visual association area (Brodmann area (BA) 18) was activated at the start of image presentation, while with the swallowing sound and artificial sound stimuli, the auditory areas BA 41 and BA 42 were activated at the time of trigger presentation. However, with animation stimuli (animation stimulus, animation + swallowing sound stimuli, and animation + artificial sound stimuli), activation in BA 6 and BA 40, corresponding to mirror neurons, was observed between 620 and 720 ms before the trigger. Besides, there were also significant differences in latency time and peak intensity between animation stimulus and animation + swallowing sound stimuli. Our results suggest that mirror neurons are activated by swallowing-related visual and auditory stimuli.

Premotor Cortex Is Sensitive to Auditory–Visual Congruence for Biological Motion

The auditory and visual perception systems have developed special processing strategies for ecologically valid motion stimuli, utilizing some of the statistical properties of the real world. A well-known example is the perception of biological motion, for example, the perception of a human walker. The aim of the current study was to identify the cortical network involved in the integration of auditory and visual biological motion signals. We first determined the cortical regions of auditory and visual coactivation (Experiment 1); a conjunction analysis based on unimodal brain activations identified four regions: middle temporal area, inferior parietal lobule, ventral premotor cortex, and cerebellum. The brain activations arising from bimodal motion stimuli (Experiment 2) were then analyzed within these regions of coactivation. Auditory footsteps were presented concurrently with either an intact visual point-light walker (biological motion) or a scrambled point-light walker; auditory and visual motion in depth (walking direction) could either be congruent or incongruent. Our main finding is that motion incongruency (across modalities) increases the activity in the ventral premotor cortex, but only if the visual point-light walker is intact. Our results extend our current knowledge by providing new evidence consistent with the idea that the premotor area assimilates information across the auditory and visual modalities by comparing the incoming sensory input with an internal representation.

Repetitive TMS suggests a role of the human dorsal premotor cortex in action prediction

Predicting the actions of other individuals is crucial for our daily interactions. Recent evidence suggests that the prediction of object-directed arm and full-body actions employs the dorsal premotor cortex (PMd). Thus, the neural substrate involved in action control may also be essential for action prediction. Here, we aimed to address this issue and hypothesized that disrupting the PMd impairs action prediction. Using fMRI-guided coil navigation, rTMS (five pulses, 10 Hz) was applied over the left PMd and over the vertex (control region) while participants observed everyday actions in video clips that were transiently occluded for 1 s. The participants detected manipulations in the time course of occluded actions, which required them to internally predict the actions during occlusion. To differentiate between functional roles that the PMd could play in prediction, rTMS was either delivered at occluder-onset (TMS-early), affecting the initiation of action prediction, or 300 ms later during occlusion (TMS-late), affecting the maintenance of an ongoing prediction. TMS-early over the left PMd produced more prediction errors than TMS-early over the vertex. TMS-late had no effect on prediction performance, suggesting that the left PMd might be involved particularly during the initiation of internally guided action prediction but may play a subordinate role in maintaining ongoing prediction. These findings open a new perspective on the role of the left PMd in action prediction which is in line with its functions in action control and in cognitive tasks. In the discussion, the relevance of the left PMd for integrating external action parameters with the observer’s motor repertoire is emphasized. Overall, the results are in line with the notion that premotor functions are employed in both action control and action observation.

Neuro-robotics study on integrative learning of proactive visual attention and motor behaviors

The current paper proposes a novel model for integrative learning of proactive visual attention and sensory-motor control as inspired by the premotor theory of visual attention. The model is characterized by coupling a slow dynamics network with a fast dynamics network and by inheriting our prior proposed multiple timescales recurrent neural networks model (MTRNN) that may correspond to the fronto-parietal networks in the cortical brains. The neuro-robotics experiments in a task of manipulating multiple objects utilizing the proposed model demonstrated that some degrees of generalization in terms of position and object size variation can be achieved by organizing seamless integration of the proactive object-related visual attention and the related sensory-motor control into a set of action primitives in the distributed neural activities appearing in the fast dynamics network. It was also shown that such action primitives can be combined in compositional ways in acquiring novel actions in the slow dynamics network. The experimental results presented substantiate the premotor theory of visual attention.

Subcortical contributions to effective connectivity in brain networks supporting imitation

Using functional magnetic resonance imaging (fMRI), we investigated effective connectivity in brain networks supporting imitation. Despite extensive reports of regional functional specialization underlying action perception, action execution and imitation, our understanding of the potential contribution of subcortical sites is limited, as is our knowledge of how regions displaying functional specialization interact with each other on a system level. While in the scanner, participants performed a simple imitation paradigm with three conditions: Observe trials, in which participants passively viewed a human actor executing a sequence of four finger presses on a keypad; Imitate trials, in which participants imitated the actor's finger presses on a keyboard; and Execute trials, in which participants also executed finger presses but did so based on visuospatial cues in the absence of the actor's hand. Relative to the Execute condition, Imitate trials evoked significantly more activity in superior and inferior parietal lobules (SPL, IPL), posterior superior temporal sulcus (pSTS), and in a ventral aspect of dorsal premotor cortex (PMd). Psychophysiological interaction (PPI) analysis, a means of assessing effective connectivity, revealed significant interactions with regions of cerebellar lobule VII from seeds both in the right pSTS and right SPL, such that activity in these sites was more highly correlated during imitation. A similar interaction was found between right pSTS and left IPL. These results clarify the role of cortical regions supporting action observation, action execution and imitation, and highlight the role the cerebellum may play in facilitating both motor and nonmotor aspects of imitation.

The impact of iconic gestures on foreign language word learning and its neural substrate

Vocabulary acquisition represents a major challenge in foreign language learning. Research has demonstrated that gestures accompanying speech have an impact on memory for verbal information in the speakers' mother tongue and, as recently shown, also in foreign language learning. However, the neural basis of this effect remains unclear. In a within-subjects design, we compared learning of novel words coupled with iconic and meaningless gestures. Iconic gestures helped learners to significantly better retain the verbal material over time. After the training, participants' brain activity was registered by means of fMRI while performing a word recognition task. Brain activations to words learned with iconic and with meaningless gestures were contrasted. We found activity in the premotor cortices for words encoded with iconic gestures. In contrast, words encoded with meaningless gestures elicited a network associated with cognitive control. These findings suggest that memory performance for newly learned words is not driven by the motor component as such, but by the motor image that matches an underlying representation of the word's semantics.

Exploring the detection of associatively novel events using fMRI

Identifying and evaluating events which are novel in a particular environment is crucially important for adaptive behavior. These events are often not just novel, as they typically violate expectations which may be formulated based on numerous features of our surroundings, one of which includes the ordinal structure (temporal order) of relevant stimuli. Events which violate such expectations, namely sequential deviants, constitute one category of associatively novel stimuli. The present event-related fMRI study investigated the detection of sequential deviants presented within three types of equivalently organized, attended visual sequences which differed in stimulus dimensions relevant for defining the sequential structure (position, rhythm, and object identity). Presenting deviants within perceptual sequences defined by position and rhythm stimulus properties triggered comparable patterns of activations within the lateral parietal, premotor, and prefrontal regions. However, the activations identified in the context of position sequences showed a more dorsal distribution when compared to those in rhythm sequences. In contrast, detection of deviants within object sequences was supported by right-lateralized parietal and temporal cortices. Thus, although the obtained results indicate similarities and partial overlap in activations triggered by specific pairs of deviants, differences in their processing were also revealed. This suggests that the general task context and specific stimulus features which define the deviant itself influence which brain regions within a widespread network incorporating lateral prefrontal, anterior premotor, and posterior (mainly lateral parietal) areas will become engaged in its processing.

Prediction of collision events: an EEG coherence analysis

OBJECTIVE

A common daily-life task is the interaction with moving objects for which prediction of collision events is required. To evaluate the sources of information used in this process, this EEG study required participants to judge whether two moving objects would collide with one another or not. In addition, the effect of a distractor object is evaluated.

METHODS

The measurements included the behavioural decision time and accuracy, eye movement fixation times, and the neural dynamics which was determined by means of EEG coherence, expressing functional connectivity between brain areas.

RESULTS

Collision judgment involved widespread information processing across both hemispheres. When a distractor object was present, task-related activity was increased whereas distractor activity induced modulation of local sensory processing. Also relevant were the parietal regions communicating with bilateral occipital and midline areas and a left-sided sensorimotor circuit.

CONCLUSIONS

Besides visual cues, cognitive and strategic strategies are used to establish a decision of events in time. When distracting information is introduced into the collision judgment process, it is managed at different processing levels and supported by distinct neural correlates.

SIGNIFICANCE

These data shed light on the processing mechanisms that support judgment of collision events; an ability that implicates higher-order decision-making.