Planning Functional Grasps of Simple Tools Invokes the Hand-independent Praxis Representation Network: An fMRI Study

Object-oriented hand dexterity and grasping abilities, from the animal quarters to the neurosurgical OR: a systematic review of the underlying neural correlates in non-human, human primate and recent findings in awake brain surgery

Introduction

The sensorimotor integrations subserving object-oriented manipulative actions have been extensively investigated in non-human primates via direct approaches, as intracortical micro-stimulation (ICMS), cytoarchitectonic analysis and anatomical tracers. However, the understanding of the mechanisms underlying complex motor behaviors is yet to be fully integrated in brain mapping paradigms and the consistency of these findings with intraoperative data obtained during awake neurosurgical procedures for brain tumor removal is still largely unexplored. Accordingly, there is a paucity of systematic studies reviewing the cross-species analogies in neural activities during object-oriented hand motor tasks in primates and investigating the concordance with intraoperative findings during brain mapping. The current systematic review was designed to summarize the cortical and subcortical neural correlates of object-oriented fine hand actions, as revealed by fMRI and PET studies, in non-human and human primates and how those were translated into neurosurgical studies testing dexterous hand-movements during intraoperative brain mapping.

Methods

A systematic literature review was conducted following the PRISMA guidelines. PubMed, EMBASE and Web of Science databases were searched. Original articles were included if they: (1) investigated cortical activation sites on fMRI and/or PET during grasping task; (2) included humans or non-human primates. A second query was designed on the databases above to collect studies reporting motor, hand manipulation and dexterity tasks for intraoperative brain mapping in patients undergoing awake brain surgery for any condition. Due to the heterogeneity in neurosurgical applications, a qualitative synthesis was deemed more appropriate.

Results

We provided an updated overview of the current state of the art in translational neuroscience about the extended frontoparietal grasping-praxis network with a specific focus on the comparative functioning in non-human primates, healthy humans and how the latter knowledge has been implemented in the neurosurgical operating room during brain tumor resection.

Discussion

The anatomical and functional correlates we reviewed confirmed the evolutionary continuum from monkeys to humans, allowing a cautious but practical adoption of such evidence in intraoperative brain mapping protocols. Integrating the previous results in the surgical practice helps preserve complex motor abilities, prevent long-term disability and poor quality of life and allow the maximal safe resection of intrinsic brain tumors.

The parietal architecture binding cognition to sensorimotor integration: a multimodal causal study

Despite human's praxis abilities are unique among primates, comparative observations suggest that these cognitive motor skills could have emerged from exploitation and adaptation of phylogenetically older building blocks, namely the parieto-frontal networks subserving prehension and manipulation. Within this framework, investigating to which extent praxis and prehension-manipulation overlap and diverge within parieto-frontal circuits could help in understanding how human cognition shapes hand actions. This issue has never been investigated by combining lesion mapping and direct electrophysiological approaches in neurosurgical patients. To this purpose, 79 right-handed left-brain tumour patient candidates for awake neurosurgery were selected based on inclusion criteria. First, a lesion mapping was performed in the early postoperative phase to localize the regions associated with an impairment in praxis (imitation of meaningless and meaningful intransitive gestures) and visuo-guided prehension (reaching-to-grasping) abilities. Then, lesion results were anatomically matched with intraoperatively identified cortical and white matter regions, whose direct electrical stimulation impaired the Hand Manipulation Task. The lesion mapping analysis showed that prehension and praxis impairments occurring in the early postoperative phase were associated with specific parietal sectors. Dorso-mesial parietal resections, including the superior parietal lobe and precuneus, affected prehension performance, while resections involving rostral intraparietal and inferior parietal areas affected praxis abilities (covariate clusters, 5000 permutations, cluster-level family-wise error correction P < 0.05). The dorsal bank of the rostral intraparietal sulcus was associated with both prehension and praxis (overlap of non-covariate clusters). Within praxis results, while resection involving inferior parietal areas affected mainly the imitation of meaningful gestures, resection involving intraparietal areas affected both meaningless and meaningful gesture imitation. In parallel, the intraoperative electrical stimulation of the rostral intraparietal and the adjacent inferior parietal lobe with their surrounding white matter during the hand manipulation task evoked different motor impairments, i.e. the arrest and clumsy patterns, respectively. When integrating lesion mapping and intraoperative stimulation results, it emerges that imitation of praxis gestures first depends on the integrity of parietal areas within the dorso-ventral stream. Among these areas, the rostral intraparietal and the inferior parietal area play distinct roles in praxis and sensorimotor process controlling manipulation. Due to its visuo-motor 'attitude', the rostral intraparietal sulcus, putative human homologue of monkey anterior intraparietal, might enable the visuo-motor conversion of the observed gesture (direct pathway). Moreover, its functional interaction with the adjacent, phylogenetic more recent, inferior parietal areas might contribute to integrate the semantic-conceptual knowledge (indirect pathway) within the sensorimotor workflow, contributing to the cognitive upgrade of hand actions.

Coming to grips with reality: Real grasps, but not pantomimed grasps, resist a simultaneous tilt illusion

Investigations of grasping real, 3D objects subjected to illusory effects from a pictorial background often choose in-flight grasp aperture as the primary variable to test the hypothesis that the visuomotor system resists the illusion. Here we test an equally important feature of grasps that has received less attention: in-flight grasp orientation. The current study tested a variant of the simultaneous tilt illusion using a mirror-apparatus to manipulate the availability of haptic feedback. Participants performed grasps with haptic feedback (real grasps) and without it (pantomime grasps), reaching for the reflection of a real, 3D bar atop a background grating that induced a 1.1° bias in the perceived orientation of the bar in a separate sample of participants. Analysis of the hand's in-flight grasp orientation at early, late, and end stages of the reach showed that at no point were the real grasps biased by the illusion. In contrast, pantomimed grasps were affected by the illusion at the late and end stages of the reach. At each stage, the effect on the real grasps was significantly weaker than the effect of the illusion as measured by the mean point of subjective equality (PSE) in a two-alternative forced-choice task. In contrast, the effect on the pantomime grasps was statistically indistinguishable from the mean PSE at all three stages of the reach. These findings reinforce the idea that in-flight grasp orientation, like grasp aperture to pictorial illusions of target size, is refractory to pictorial backgrounds that bias perceived orientation.

The functional organization of skilled actions in the adextral and atypical brain

When planning functional grasps of tools, right-handed individuals (dextrals) show mostly left-lateralized neural activity in the praxis representation network (PRN), regardless of the used hand. Here we studied whether or not similar cerebral asymmetries are evident in non-righthanded individuals (adextrals). Sixty two participants, 28 righthanders and 34 non-righthanders (21 lefthanders, 13 mixedhanders), planned functional grasps of tools vs. grasps of control objects, and subsequently performed their pantomimed executions, in an event-related functional magnetic resonance imaging (fMRI) project. Both hands were tested, separately in two different sessions, counterbalanced across participants. After accounting for non-functional components of the prospective grasp, planning functional grasps of tools was associated with greater engagement of the same, left-hemisphere occipito-temporal, parietal and frontal areas of PRN, regardless of hand and handedness. Only when the analyses involved signal changes referenced to resting baseline intervals, differences between adextrals and dextrals emerged. Whereas in the left hemisphere the neural activity was equivalent in both groups (except for the occipito-temporo-parietal junction), its increases in the right occipito-temporal cortex, medial intraparietal sulcus (area MIP), the supramarginal gyrus (area PFt/PF), and middle frontal gyrus (area p9-46v) were significantly greater in adextrals. The inverse contrast was empty. Notably, when individuals with atypical and typical hemispheric phenotypes were directly compared, planning functional (vs. control) grasps invoked, instead, significant clusters located nearly exclusively in the left hemisphere of the typical phenotype. Previous studies interpret similar right-sided vs. left-sided increases in neural activity for skilled actions as handedness dependent, i.e., located in the hemisphere dominant for manual skills. Yet, none of the effects observed here can be purely handedness dependent because there were mixed-handed individuals among adextrals, and numerous mixed-handed and left-handed individuals possess the typical phenotype. Thus, our results clearly show that hand dominance has limited power in driving the cerebral organization of motor cognitive functions.

Taxonomic and thematic relations rely on different types of semantic features: Evidence from an fMRI meta-analysis and a semantic priming study

Taxonomic and thematic relations are major components of semantic representation but their neurocognitive underpinnings are still debated. We hypothesised that taxonomic relations preferentially activate parts of anterior temporal lobe (ATL) because they rely more on colour and shape features, while thematic relations preferentially activate temporoparietal cortex (TPC) because they rely more on action and location knowledge. We first conducted activation likelihood estimation (ALE) meta-analysis to assess evidence for neural specialisation in the existing fMRI literature (Study 1), then used a primed semantic judgement task to examine if the two relations are primed by different feature types (Study 2). We find that taxonomic relations show minimal feature-based specialisation but preferentially activate the lingual gyrus. Thematic relations are more dependent on action and location features and preferentially engage TPC. The meta-analysis also showed that lateral ATL is preferentially engaged by Thematic relations, which may reflect their greater reliance on verbal associations.

Action goals and the praxis network: an fMRI study

The praxis representation network (PRN) of the left cerebral hemisphere is typically linked to the control of functional interactions with familiar tools. Surprisingly, little is known about the PRN engagement in planning and execution of tool-directed actions motivated by non-functional but purposeful action goals. Here we used functional neuroimaging to perform both univariate and multi-voxel pattern analyses (MVPA) in 20 right-handed participants who planned and later executed, with their dominant and non-dominant hands, disparate grasps of tools for different goals, including: (1) planning simple vs. demanding functional grasps of conveniently vs. inconveniently oriented tools with an intention to immediately use them, (2) planning simple—but non-functional—grasps of inconveniently oriented tools with a goal to pass them to a different person, (3) planning reaching movements directed at such tools with an intention to move/push them with the back of the hand, and (4) pantomimed execution of the earlier planned tasks. While PRN contributed to the studied interactions with tools, the engagement of its critical nodes, and/or complementary right hemisphere processing, was differently modulated by task type. E.g., planning non-functional/structural grasp-to-pass movements of inconveniently oriented tools, regardless of the hand, invoked the left parietal and prefrontal nodes significantly more than simple, non-demanding functional grasps. MVPA corroborated decoding capabilities of critical PRN areas and some of their right hemisphere counterparts. Our findings shed new lights on how performance of disparate action goals influences the extraction of object affordances, and how or to what extent it modulates the neural activity within the parieto-frontal brain networks.

Complex tools and motor-to-mechanical transformations

The ability to use complex tools is thought to depend on multifaceted motor-to-mechanical transformations within the left inferior parietal lobule (IPL), linked to cognitive control over compound actions. Here we show using neuroimaging that demanding transformations of finger movements into proper mechanical movements of functional parts of complex tools invoke significantly the right rather than left rostral IPL, and bilateral posterior-to-mid and left anterior intraparietal sulci. These findings emerged during the functional grasp and tool-use programming phase. The expected engagement of left IPL was partly revealed by traditional region-of-interest analyses, and further modeling/estimations at the hand-independent level. Thus, our results point to a special role of right IPL in supporting sensory-motor spatial mechanisms which enable an effective control of fingers in skillful handling of complex tools. The resulting motor-to-mechanical transformations involve dynamic hand-centered to target-centered reference frame conversions indispensable for efficient interactions with the environment.

Left hemisphere dominance for bilateral kinematic encoding in the human brain

Neurophysiological studies in humans and nonhuman primates have revealed movement representations in both the contralateral and ipsilateral hemispheres. Inspired by clinical observations, we ask if this bilateral representation differs for the left and right hemispheres. Electrocorticography was recorded in human participants during an instructed-delay reaching task, with movements produced with either the contralateral or ipsilateral arm. Using a cross-validated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere, indicating similar neural representations for right and left arm movements. Notably, these left hemisphere electrodes were centered over premotor and parietal regions. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis.

Everyone Can Implement Eduball in Physical Education to Develop Cognitive and Motor Skills in Primary School Students

Studies suggest that incorporating core academic subjects into physical education (PE) stimulates the development of both motor and cognitive skills in primary school students. For example, several experiments show that children’s participation in Eduball, i.e., a method that uses educational balls with printed letters, numbers, and other signs, improves their physical fitness while simultaneously developing their mathematical and language skills. However, the question of who should conduct such classes to make them most effective (regular classroom teachers, physical education teachers, or maybe both in cooperation?) remains unanswered. Here, we replicated a previous Eduball experiment, but now, instead of one experimental group, there were three. In the first, Eduball-classes were conducted by the classroom teacher, in the second, by the physical education teacher, and in the third, collaboratively. After one year intervention, all experimental groups significantly improved both their cognitive (mathematical, reading, and writing) and gross motor (locomotor and object control) skills, and these effects were larger than in the control group participating in traditional PE. Importantly, there were no differences in progression between the Eduball-groups. Thus, our study demonstrates that methods linking PE with cognitive tasks can be effectively used by both PE specialists and general classroom teachers.

The Ties that Bind: Agnosia, Neglect and Selective Attention to Visual Scale

PURPOSE OF REVIEW

Historical and contemporary treatments of visual agnosia and neglect regard these disorders as largely unrelated. It is thought that damage to different neural processes leads directly to one or the other condition, yet apperceptive variants of agnosia and object-centered variants of neglect share remarkably similar deficits in the quality of conscious experience. Here we argue for a closer association between "apperceptive" variants of visual agnosia and "object-centered" variants of visual neglect. We introduce a theoretical framework for understanding these conditions based on "scale attention", which refers to selecting boundary and surface information at different levels of the structural hierarchy in the visual array.

RECENT FINDINGS

We review work on visual agnosia, the cortical structures and cortico-cortical pathways that underlie visual perception, visuospatial neglect and object-centered neglect, and attention to scale. We highlight direct and indirect pathways involved in these disorders and in attention to scale. The direct pathway involves the posterior vertical segments of the superior longitudinal fasciculus that are positioned to link the established dorsal and ventral attentional centers in the parietal cortex with structures in the inferior occipitotemporal cortex associated with visual apperceptive agnosia. The connections in the right hemisphere appear to be more important for visual conscious experience, whereas those in the left hemisphere appear to be more strongly associated with the planning and execution of visually guided grasps directed at multi-part objects such as tools. In the latter case, semantic and functional information must drive the selection of the appropriate hand posture and grasp points on the object. This view is supported by studies of grasping in patients with agnosia and in patients with neglect that show that the selection of grasp points when picking up a tool involves both scale attention and semantic contributions from inferotemporal cortex. The indirect pathways, which include the inferior fronto-occipital and horizontal components of the superior longitudinal fasciculi, involve the frontal lobe, working memory and the "multiple demands" network, which can shape the content of visual awareness through the maintenance of goal- and task-based abstractions and their influence on scale attention. Recent studies of human cortico-cortical pathways necessitate revisions to long-standing theoretical views on visual perception, visually guided action and their integrations. We highlight findings from a broad sample of seemingly disparate areas of research to support the proposal that attention to scale is necessary for typical conscious visual experience and for goal-directed actions that depend on functional and semantic information. Furthermore, we suggest that vertical pathways between the parietal and occipitotemporal cortex, along with indirect pathways that involve the premotor and prefrontal cortex, facilitate the operations of scale attention.

Semantic and action tool knowledge in the brain: Identifying common and distinct networks

Most cognitive models of apraxia assume that impaired tool use results from a deficit occurring at the conceptual level, which contains dedicated information about tool use, namely, semantic and action tool knowledge. Semantic tool knowledge contains information about the prototypical use of familiar tools, such as function (e.g., a hammer and a mallet share the same purpose) and associative relations (e.g., a hammer goes with a nail). Action tool knowledge contains information about how to manipulate tools, such as hand posture and kinematics. The present review aimed to better understand the neural correlates of action and semantic tool knowledge, by focusing on activation, stimulation and patients' studies (left brain-damaged patients). We found that action and semantic tool knowledge rely upon a large brain network including temporal and parietal regions. Yet, while action tool knowledge calls into play the intraparietal sulcus, function relations mostly involve the anterior and posterior temporal lobe. Associative relations engaged the angular and the posterior middle temporal gyrus. Moreover, we found that hand posture and kinematics both tapped into the inferior parietal lobe and the lateral occipital temporal cortex, but no region specificity was found for one or the other representation. Our results point out the major role of both posterior middle temporal gyrus and inferior parietal lobe for action and semantic tool knowledge. They highlight the common and distinct brain networks involved in action and semantic tool networks and spur future directions on this topic.

Hand-Selective Visual Regions Represent How to Grasp 3D Tools: Brain Decoding during Real Actions

Most neuroimaging experiments that investigate how tools and their actions are represented in the brain use visual paradigms where tools or hands are displayed as 2D images and no real movements are performed. These studies discovered selective visual responses in occipitotemporal and parietal cortices for viewing pictures of hands or tools, which are assumed to reflect action processing, but this has rarely been directly investigated. Here, we examined the responses of independently visually defined category-selective brain areas when participants grasped 3D tools (N = 20; 9 females). Using real-action fMRI and multivoxel pattern analysis, we found that grasp typicality representations (i.e., whether a tool is grasped appropriately for use) were decodable from hand-selective areas in occipitotemporal and parietal cortices, but not from tool-, object-, or body-selective areas, even if partially overlapping. Importantly, these effects were exclusive for actions with tools, but not for biomechanically matched actions with control nontools. In addition, grasp typicality decoding was significantly higher in hand than tool-selective parietal regions. Notably, grasp typicality representations were automatically evoked even when there was no requirement for tool use and participants were naive to object category (tool vs nontools). Finding a specificity for typical tool grasping in hand-selective, rather than tool-selective, regions challenges the long-standing assumption that activation for viewing tool images reflects sensorimotor processing linked to tool manipulation. Instead, our results show that typicality representations for tool grasping are automatically evoked in visual regions specialized for representing the human hand, the primary tool of the brain for interacting with the world.

Manual praxis and language-production networks, and their links to handedness

While Liepmann was one of the first researchers to consider a relationship between skilled manual actions (praxis) and language for tasks performed "freely from memory", his primary focus was on the relations between the organization of praxis and left-hemisphere dominance. Subsequent attempts to apply his apraxia model to all cases he studied - including his first patient, a "non-pure right-hander" treated as an exception - left the praxis-handedness issue unresolved. Modern neuropsychological and recent neuroimaging evidence either showed closer associations of praxis and language, than between handedness and any of these two functions, or focused on their dissociations. Yet, present-day developments in neuroimaging and statistics allow us to overcome the limitations of the earlier work on praxis-language-handedness links, and to better quantify their interrelationships. Using functional magnetic resonance imaging (fMRI), we studied tool use pantomimes and subvocal word generation in 125 participants, including righthanders (N_RH = 52), ambidextrous individuals (mixedhanders; N_MH = 31), and lefthanders (N_LH = 42). Laterality indices were calculated both in two critical cytoarchitectonic maps, and 180 multi-modal parcellations of the human cerebral cortex, using voxel count and signal intensity, and the most relevant regions of interest and their networks were further analyzed. We found that atypical organization of praxis was present in all handedness groups (RH = 25.0%, MH = 22.6%; LH = 45.2%), and was about two and a half times as common as atypical organization of language (RH = 3.8%; MH = 6.5%; LH = 26.2%), contingent on ROI selection/LI-calculation method. Despite strong associations of praxis and language, regardless of handedness and typicality, dissociations of atypically represented praxis from typical left-lateralized language were common (~20% of cases), whereas the inverse dissociations of atypically represented language from typical left-lateralized praxis were very rare (in ~2.5% of all cases). The consequences of the existence of such different phenotypes for theoretical accounts of manual praxis, and its links to language and handedness are modeled and discussed.

Physical Activity With Eduball Stimulates Graphomotor Skills in Primary School Students

Despite the general agreement that the interdisciplinary model of physical education (PE), based on the incorporation of core academic subjects into the PE curriculum, stimulates the holistic development of students, there is still a lack of methods for its implementation. Therefore, Eduball was created, i.e., a method that uses educational balls with printed letters, numbers, and other signs. Numerous studies have shown that children participating in activities with Eduballs can develop their physical fitness while simultaneously improving their academic performance, particularly in math and language, including some writing skills. However, little is known about the effects of Eduball on children's graphomotor skills, which are key for the academic performance of students throughout the entire schooling process. Here, we investigate whether 6-month participation in PE with Eduball stimulates graphomotor skills in primary school students, such as drawing prehandwriting letter patterns on unlined or lined paper and rewriting text on unlined or lined paper. Our results show that the Eduball class (N = 28) significantly improved these skills compared to the control class (N = 26) participating in traditional PE. For example, students from the experimental group wrote with a lower pen pressure and better stability of the line, in contrast to those from the control group. Therefore, this study demonstrates that the Eduball method successfully supports teachers in developing graphomotor skills in children. More broadly, our findings make clear once again that there is the need to integrate physical and cognitive development in education, which can be achieved by using an interdisciplinary model of PE.

The Role of Haptic Expectations in Reaching to Grasp: From Pantomime to Natural Grasps and Back Again

When we reach to pick up an object, our actions are effortlessly informed by the object's spatial information, the position of our limbs, stored knowledge of the object's material properties, and what we want to do with the object. A substantial body of evidence suggests that grasps are under the control of "automatic, unconscious" sensorimotor modules housed in the "dorsal stream" of the posterior parietal cortex. Visual online feedback has a strong effect on the hand's in-flight grasp aperture. Previous work of ours exploited this effect to show that grasps are refractory to cued expectations for visual feedback. Nonetheless, when we reach out to pretend to grasp an object (pantomime grasp), our actions are performed with greater cognitive effort and they engage structures outside of the dorsal stream, including the ventral stream. Here we ask whether our previous finding would extend to cued expectations for haptic feedback. Our method involved a mirror apparatus that allowed participants to see a "virtual" target cylinder as a reflection in the mirror at the start of all trials. On "haptic feedback" trials, participants reached behind the mirror to grasp a size-matched cylinder, spatially coincident with the virtual one. On "no-haptic feedback" trials, participants reached behind the mirror and grasped into "thin air" because no cylinder was present. To manipulate haptic expectation, we organized the haptic conditions into blocked, alternating, and randomized schedules with and without verbal cues about the availability of haptic feedback. Replicating earlier work, we found the strongest haptic effects with the blocked schedules and the weakest effects in the randomized uncued schedule. Crucially, the haptic effects in the cued randomized schedule was intermediate. An analysis of the influence of the upcoming and immediately preceding haptic feedback condition in the cued and uncued random schedules showed that cuing the upcoming haptic condition shifted the haptic influence on grip aperture from the immediately preceding trial to the upcoming trial. These findings indicate that, unlike cues to the availability of visual feedback, participants take advantage of cues to the availability of haptic feedback, flexibly engaging pantomime, and natural modes of grasping to optimize the movement.

Mental Shopping Calculations: A Transcranial Magnetic Stimulation Study

One of the most critical skills behind consumer's behavior is the ability to assess whether a price after a discount is a real bargain. Yet, the neural underpinnings and cognitive mechanisms associated with such a skill are largely unknown. While there is general agreement that the posterior parietal cortex (PPC) on the left is critical for mental calculations, and there is also recent repetitive transcranial magnetic stimulation (rTMS) evidence pointing to the supramarginal gyrus (SMG) of the right PPC as crucial for consumer-like arithmetic (e.g., multi-digit mental addition or subtraction), it is still unknown whether SMG is involved in calculations of sale prices. Here, we show that the neural mechanisms underlying discount arithmetic characteristic for shopping are different from complex addition or subtraction, with discount calculations engaging left SMG more. We obtained these outcomes by remodeling our laboratory to resemble a shop and asking participants to calculate prices after discounts (e.g., $8.80-25 or $4.80-75%), while stimulating left and right SMG with neuronavigated rTMS. Our results indicate that such complex shopping calculations as establishing the price after a discount involve SMG asymmetrically, whereas simpler calculations such as price addition do not. These findings have some consequences for neural models of mathematical cognition and shed some preliminary light on potential consumer's behavior in natural settings.

Decoding Brain States for Planning Functional Grasps of Tools: A Functional Magnetic Resonance Imaging Multivoxel Pattern Analysis Study

OBJECTIVES

We used multivoxel pattern analysis (MVPA) to investigate neural selectivity for grasp planning within the left-lateralized temporo-parieto-frontal network of areas (praxis representation network, PRN) typically associated with tool-related actions, as studied with traditional neuroimaging contrasts.

METHODS

We used data from 20 participants whose task was to plan functional grasps of tools, with either right or left hands. Region of interest and whole-brain searchlight analyses were performed to show task-related neural patterns.

RESULTS

MVPA revealed significant contributions to functional grasp planning from the anterior intraparietal sulcus (aIPS) and its immediate vicinities, supplemented by inputs from posterior subdivisions of IPS, and the ventral lateral occipital complex (vLOC). Moreover, greater local selectivity was demonstrated in areas near the superior parieto-occipital cortex and dorsal premotor cortex, putatively forming the dorso-dorsal stream.

CONCLUSIONS

A contribution from aIPS, consistent with its role in prospective grasp formation and/or encoding of relevant tool properties (e.g., potential graspable parts), is likely to accompany the retrieval of manipulation and/or mechanical knowledge subserved by the supramarginal gyrus for achieving action goals. An involvement of vLOC indicates that MVPA is particularly sensitive to coding of object properties, their identities and even functions, for a support of grip formation. Finally, the engagement of the superior parieto-frontal regions as revealed by MVPA is consistent with their selectivity for transient features of tools (i.e., variable affordances) for anticipatory hand postures. These outcomes support the notion that, compared to traditional approaches, MVPA can reveal more fine-grained patterns of neural activity. (JINS, 2018, 24, 1013-1025).

Efficiency in Rule- vs. Plan-Based Movements Is Modulated by Action-Mode

The rule/plan motor cognition (RPMC) paradigm elicits visually indistinguishable motor outputs, resulting from either plan- or rule-based action-selection, using a combination of essentially interchangeable stimuli. Previous implementations of the RPMC paradigm have used pantomimed movements to compare plan- vs. rule-based action-selection. In the present work we attempt to determine the generalizability of previous RPMC findings to real object interaction by use of a grasp-to-rotate task. In the plan task, participants had to use prospective planning to achieve a comfortable post-handle rotation hand posture. The rule task used implementation intentions (if-then rules) leading to the same comfortable end-state. In Experiment A, we compare RPMC performance of 16 healthy participants in pantomime and real object conditions of the experiment, within-subjects. Higher processing efficiency of rule- vs. plan-based action-selection was supported by diffusion model analysis. Results show a significant response-time increase in the pantomime condition compared to the real object condition and a greater response-time advantage of rule-based vs. plan-based actions in the pantomime compared to the real object condition. In Experiment B, 24 healthy participants performed the real object RPMC task in a task switching vs. a blocked condition. Results indicate that plan-based action-selection leads to longer response-times and less efficient information processing than rule-based action-selection in line with previous RPMC findings derived from the pantomime action-mode. Particularly in the task switching mode, responses were faster in the rule compared to the plan task suggesting a modulating influence of cognitive load. Overall, results suggest an advantage of rule-based action-selection over plan-based action-selection; whereby differential mechanisms appear to be involved depending on the action-mode. We propose that cognitive load is a factor that modulates the advantageous effect of implementation intentions in motor cognition on different levels as illustrated by the varying speed advantages and the variation in diffusion parameters per action-mode or condition, respectively.

Getting a handle on virtual tools: An examination of the neuronal activity associated with virtual tool use

Tool use is associated with three visual streams-dorso-dorsal, ventro-dorsal, and ventral visual streams. These streams are involved in processing online motor planning, action semantics, and tool semantics features, respectively. Little is known about the way in which the brain represents virtual tools. To directly assess this question, a virtual tool paradigm was created that provided the ability to manipulate tool components in isolation of one another. During functional magnetic resonance imaging (fMRI), adult participants performed a series of virtual tool manipulation tasks in which vision and movement kinematics of the tool were manipulated. Reaction time and hand movement direction were monitored while the tasks were performed. Functional imaging revealed that activity within all three visual streams was present, in a similar pattern to what would be expected with physical tool use. However, a previously unreported network of right-hemisphere activity was found including right inferior parietal lobule, middle and superior temporal gyri and supramarginal gyrus - regions well known to be associated with tool processing within the left hemisphere. These results provide evidence that both virtual and physical tools are processed within the same brain regions, though virtual tools recruit bilateral tool processing regions to a greater extent than physical tools.

Unique Neural Characteristics of Atypical Lateralization of Language in Healthy Individuals

Using functional magnetic resonance imaging (fMRI) in 63 healthy participants, including left-handed and ambidextrous individuals, we tested how atypical lateralization of language—i. e., bilateral or right hemispheric language representation—differs from the typical left-hemisphere dominance. Although regardless of their handedness, all 11 participants from the atypical group engaged classical language centers, i.e., Broca's and Wernicke's areas, the right-hemisphere components of the default mode network (DMN), including the angular gyrus and middle temporal gyrus, were also critically involved during the verbal fluency task. Importantly, activity in these regions could not be explained in terms of mirroring the typical language pattern because left-hemisphere dominant individuals did not exhibit similar significant signal modulations. Moreover, when spatial extent of language-related activity across whole brain was considered, the bilateral language organization entailed more diffuse functional processing. Finally, we detected significant differences between the typical and atypical group in the resting-state connectivity at the global and local level. These findings suggest that the atypical lateralization of language has unique features, and is not a simple mirror image of the typical left hemispheric language representation.

Involvement of the Left Supramarginal Gyrus in Manipulation Judgment Tasks: Contributions to Theories of Tool Use

OBJECTIVES

Two theories of tool use, namely the gesture engram and the technical reasoning theories, make distinct predictions about the involvement of the left inferior parietal lobe (IPL) in manipulation judgement tasks. The objective here is to test these alternative predictions based on previous studies on manipulation judgment tasks using transcranial magnetic stimulations (TMS) targeting the left supramarginal gyrus (SMG).

METHODS

We review recent TMS studies on manipulation judgement tasks and confront these data with predictions made by both tool use theories.

RESULTS

The left SMG is a highly intertwined region, organized following several functionally distinct areas and TMS may have disrupted a cortical network involved in the ability to use tools rather than only one functional area supporting manipulation knowledge. Moreover, manipulation judgement tasks may be impaired following virtual lesions outside the IPL.

CONCLUSIONS

These data are more in line with the technical reasoning hypothesis, which assumes that the left IPL does not store manipulation knowledge per se. (JINS, 2017, 23, 685-691).

Is there a Competition between Functional and Situational Affordances during Action Initiation with Everyday Tools?

Most studies of human-tool interactions focus on the typical use of a tool (e.g., cutting in the case of a knife). However, little is known about situations requiring atypical tool use (e.g., using a knife to tighten a screw). The present study focused on a selection of atypical uses of everyday tools which might be in conflict with their typical use. Our objective was to study how tool function influences the selection of the relevant action. In Experiment 1, which involved visuomotor priming, two everyday tools (a knife and a screwdriver) and two neutral tools (two bars, with no strong functional affordance) were used as primes and targets. Participants had to use the target with the appropriate box (indicated by the color) that allowed to make an action. Longer initiation times were observed when the prime was an everyday tool, irrespective of the nature of the target. We therefore observed a conflict between functional and situational affordances. To investigate whether the priming effect is caused by the task-irrelevance of the prime, we asked the participants in Experiment 2 to perform an action associated with the prime. The results showed longer initiation times only when the prime and target were everyday tools, irrespective of their precise nature. This suggests that activation of the typical use of a tool might not be fully automatic but flexible depending on the situation.

Numbers and functional lateralization: A visual half-field and dichotic listening study in proficient bilinguals

Potential links between language and numbers and the laterality of symbolic number representations in the brain are still debated. Furthermore, reports on bilingual individuals indicate that the language-number interrelationships might be quite complex. Therefore, we carried out a visual half-field (VHF) and dichotic listening (DL) study with action words and different forms of symbolic numbers used as stimuli to test the laterality of word and number processing in single-, dual-language and mixed -task and language- contexts. Experiment 1 (VHF) showed a significant right visual field/left hemispheric advantage in response accuracy for action word, as compared to any form of symbolic number processing. Experiment 2 (DL) revealed a substantially reversed effect - a significant right ear/left hemisphere advantage for arithmetic operations as compared to action word processing, and in response times in single- and dual-language contexts for number vs. action words. All these effects were language independent. Notably, for within-task response accuracy compared across modalities significant differences were found in all studied contexts. Thus, our results go counter to findings showing that action-relevant concepts and words, as well as number words are represented/processed primarily in the left hemisphere. Instead, we found that in the auditory context, following substantial engagement of working memory (here: by arithmetic operations), there is a subsequent functional reorganization of processing single stimuli, whether verbs or numbers. This reorganization - their weakened laterality - at least for response accuracy is not exclusive to processing of numbers, but the number of items to be processed. For response times, except for unpredictable tasks in mixed contexts, the "number problem" is more apparent. These outcomes are highly relevant to difficulties that simultaneous translators encounter when dealing with lengthy auditory material in which single items such as number words (and possibly other types of key words) need to be emphasized. Our results may also shed a new light on the "mathematical savant problem".