Cortical networks related to human use of tools

Trajectory recognition as the basis for object individuation: a functional model of object file instantiation and object-token encoding

The perception of persisting visual objects is mediated by transient intermediate representations, object files, that are instantiated in response to some, but not all, visual trajectories. The standard object file concept does not, however, provide a mechanism sufficient to account for all experimental data on visual object persistence, object tracking, and the ability to perceive spatially disconnected stimuli as continuously existing objects. Based on relevant anatomical, functional, and developmental data, a functional model is constructed that bases visual object individuation on the recognition of temporal sequences of apparent center-of-mass positions that are specifically identified as trajectories by dedicated "trajectory recognition networks" downstream of the medial-temporal motion-detection area. This model is shown to account for a wide range of data, and to generate a variety of testable predictions. Individual differences in the recognition, abstraction, and encoding of trajectory information are expected to generate distinct object persistence judgments and object recognition abilities. Dominance of trajectory information over feature information in stored object tokens during early infancy, in particular, is expected to disrupt the ability to re-identify human and other individuals across perceptual episodes, and lead to developmental outcomes with characteristics of autism spectrum disorders.

Brain mechanisms of perceiving tools and imagining tool use acts: a functional MRI study

The ability to conceptualize and manipulate tools in a complex manner is a distinguishing characteristic of humans, and forms a promising milestone in human evolution. While using tools is a motor act, proposals for executing such acts may be evoked by the mere perception of a tool. Imagining an action using a tool may invoke mental readjustment of body posture, planning motor movements, and matching such plans with the model action. This fMRI study examined the brain response in 32 healthy adults when they either viewed a tool or imagined using it. While both viewing and imagining tasks recruited similar regions, imagined tool use showed greater activation in motor areas, and in areas around the bilateral temporoparietal junction. Viewing tools, on the other hand, produced robust activation in the inferior frontal, occipital, parietal, and ventral temporal areas. Analysis of gender differences indicated males recruiting medial prefrontal and anterior cingulate cortices and females, left supramarginal gyrus and left anterior insula. While tool viewing seems to generate prehensions about using them, the imagined action using a tool mirrored brain responses underlying functional use of it. The findings of this study may suggest that perception and imagination of tools may form precursors to overt actions.

It takes two-skilled recognition of objects engages lateral areas in both hemispheres

Our object recognition abilities, a direct product of our experience with objects, are fine-tuned to perfection. Left temporal and lateral areas along the dorsal, action related stream, as well as left infero-temporal areas along the ventral, object related stream are engaged in object recognition. Here we show that expertise modulates the activity of dorsal areas in the recognition of man-made objects with clearly specified functions. Expert chess players were faster than chess novices in identifying chess objects and their functional relations. Experts' advantage was domain-specific as there were no differences between groups in a control task featuring geometrical shapes. The pattern of eye movements supported the notion that experts' extensive knowledge about domain objects and their functions enabled superior recognition even when experts were not directly fixating the objects of interest. Functional magnetic resonance imaging (fMRI) related exclusively the areas along the dorsal stream to chess specific object recognition. Besides the commonly involved left temporal and parietal lateral brain areas, we found that only in experts homologous areas on the right hemisphere were also engaged in chess specific object recognition. Based on these results, we discuss whether skilled object recognition does not only involve a more efficient version of the processes found in non-skilled recognition, but also qualitatively different cognitive processes which engage additional brain areas.

Re-examining the gesture engram hypothesis. New perspectives on apraxia of tool use

In everyday life, we are led to reuse the same tools (e.g., fork, hammer, coffee-maker), raising the question as to whether we have to systematically recreate the idea of the manipulation which is associated with these tools. The gesture engram hypothesis offers a straightforward answer to this issue, by suggesting that activation of gesture engrams provides a processing advantage, avoiding portions of the process from being reconstructed de novo with each experience. At first glance, the gesture engram hypothesis appears very plausible. But, behind this beguiling simplicity lies a set of unresolved difficulties: (1) What is the evidence in favour of the idea that the mere observation of a tool is sufficient to activate the corresponding gesture engram? (2) If tool use can be supported by a direct route between a structural description system and gesture engrams, what is the role of knowledge about tool function? (3) And, more importantly, what does it mean to store knowledge about how to manipulate tools? We begin by outlining some of the main formulations of the gesture engram hypothesis. Then, we address each of these issues in more detail. To anticipate our discussion, the gesture engram hypothesis appears to be clearly unsatisfactory, notably because of its incapacity to offer convincing answers to these different issues. We conclude by arguing that neuropsychology may greatly benefit from adopting the hypothesis that the idea of how to manipulate a tool is recreated de novo with each experience, thus opening interesting perspectives for future research on apraxia.

The organization and dissolution of semantic-conceptual knowledge: is the 'amodal hub' the only plausible model?

In recent years, the anatomical and functional bases of conceptual activity have attracted a growing interest. In particular, Patterson and Lambon-Ralph have proposed the existence, in the anterior parts of the temporal lobes, of a mechanism (the 'amodal semantic hub') supporting the interactive activation of semantic representations in all modalities and for all semantic categories. The aim of then present paper is to discuss this model, arguing against the notion of an 'amodal' semantic hub, because we maintain, in agreement with the Damasio's construct of 'higher-order convergence zone', that a continuum exists between perceptual information and conceptual representations, whereas the 'amodal' account views perceptual informations only as a channel through which abstract semantic knowledge can be activated. According to our model, semantic organization can be better explained by two orthogonal higher-order convergence systems, concerning, on one hand, the right vs. left hemisphere and, on the other hand, the ventral vs. dorsal processing pathways. This model posits that conceptual representations may be mainly based upon perceptual activities in the right hemisphere and upon verbal mediation in the left side of the brain. It also assumes that conceptual knowledge based on the convergence of highly processed visual information with other perceptual data (and mainly concerning living categories) may be bilaterally represented in the anterior parts of the temporal lobes, whereas knowledge based on the integration of visual data with action schemata (namely knowledge of actions, body parts and artefacts) may be more represented in the left fronto-temporo-parietal areas.

On the role of object information in action observation: an fMRI study

Observing other people's actions activates a network of brain regions that is also activated during the execution of these actions. Here, we used functional magnetic resonance imaging to test whether these "mirror" regions in frontal and parietal cortices primarily encode the spatiomotor aspects or the functional goal-related aspects of observed tool actions. Participants viewed static depictions of actions consisting of a tool object (e.g., key) and a target object (e.g., keyhole). They judged the actions either with regard to whether the objects were oriented correctly for the action to succeed (spatiomotor task) or whether an action goal could be achieved with the objects (function task). Compared with a control condition, both tasks activated regions in left frontoparietal cortex previously implicated in action observation and execution. Of these regions, the premotor cortex and supramarginal gyrus were primarily activated during the spatiomotor task, whereas the middle frontal gyrus was primarily activated during the function task. Regions along the intraparietal sulcus were more strongly activated during the spatiomotor task but only when the spatiomotor properties of the tool object were unknown in advance. These results suggest a division of labor within the action observation network that maps onto a similar division previously proposed for action execution.

The Neuroscience of Storing and Molding Tool Action Concepts: How "Plastic" is Grounded Cognition?

Choosing how to use tools to accomplish a task is a natural and seemingly trivial aspect of our lives, yet engages complex neural mechanisms. Recently, work in healthy populations has led to the idea that tool knowledge is grounded to allow for appropriate recall based on some level of personal history. This grounding has presumed neural loci for tool use, centered on parieto-temporo-frontal areas to fuse perception and action representations into one dynamic system. A challenge for this idea is related to one of its great benefits. For such a system to exist, it must be very plastic, to allow for the introduction of novel tools or concepts of tool use and modification of existing ones. Thus, learning new tool usage (familiar tools in new situations and new tools in familiar situations) must involve mapping into this grounded network while maintaining existing rules for tool usage. This plasticity may present a challenging breadth of encoding that needs to be optimally stored and accessed. The aim of this work is to explore the challenges of plasticity related to changing or incorporating representations of tool action within the theory of grounded cognition and propose a modular model of tool–object goal related accomplishment. While considering the neuroscience evidence for this approach, we will focus on the requisite plasticity for this system. Further, we will highlight challenges for flexibility and organization of already grounded tool actions and provide thoughts on future research to better evaluate mechanisms of encoding in the theory of grounded cognition.

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

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

More automation and less cognitive control of imagined walking movements in high- versus low-fit older adults

Using motor imagery, we investigated brain activation in simple and complex walking tasks (walking forward and backward on a treadmill) and analyzed if the motor status of older adults influenced these activation patterns. Fifty-one older adults (64-79 years of age) were trained in motor execution and imagery and then performed the imagination task and two control tasks (standing, counting backward) in a horizontal position within a 3T MRI scanner (first-person perspective, eyes closed). Walking backward as compared to walking forward required larger activations in the primary motor cortex, supplementary motor area, parietal cortex, thalamus, putamen, and caudatum, but less activation in the cerebellum and brainstem. Motor high-fit individuals showed more activations and larger BOLD signals in motor-related areas compared to low-fit participants but demonstrated lower activity in the dorsolateral prefrontal cortex. Moreover, parietal activation in high-fit participants remained stable throughout the movement period whereas low-fit participants revealed an early drop in activity in this area accompanied by increasing activity in frontal brain regions. Overall, walking forward seemed to be more automated (more activation in cerebellum and brainstem), whereas walking backward required more resources, e.g., for visual-spatial processing and sensorimotor control. Low-fit subjects in particular seemed to require more cognitive resources for planning and controlling. High-fit subjects, on the contrary, revealed more movement automation and a higher "attention span." Our results support the hypothesis that high fitness corresponds with more automation and less cognitive control of complex motor tasks, which might help to free up cognitive resources.

Neuroimaging of love: fMRI meta-analysis evidence toward new perspectives in sexual medicine

INTRODUCTION

Brain imaging is becoming a powerful tool in the study of human cerebral functions related to close personal relationships. Outside of subcortical structures traditionally thought to be involved in reward-related systems, a wide range of neuroimaging studies in relationship science indicate a prominent role for different cortical networks and cognitive factors. Thus, the field needs a better anatomical/network/whole-brain model to help translate scientific knowledge from lab bench to clinical models and ultimately to the patients suffering from disorders associated with love and couple relationships.

AIM

The aim of the present review is to provide a review across wide range of functional magnetic resonance imaging (fMRI) studies to critically identify the cortical networks associated with passionate love, and to compare and contrast it with other types of love (such as maternal love and unconditional love for persons with intellectual disabilities).

METHODS

Retrospective review of pertinent neuroimaging literature.

MAIN OUTCOME MEASURES

Review of published literature on fMRI studies of love illustrating brain regions associated with different forms of love.

RESULTS

Although all fMRI studies of love point to the subcortical dopaminergic reward-related brain systems (involving dopamine and oxytocin receptors) for motivating individuals in pair-bonding, the present meta-analysis newly demonstrated that different types of love involve distinct cerebral networks, including those for higher cognitive functions such as social cognition and bodily self-representation.

CONCLUSIONS

These metaresults provide the first stages of a global neuroanatomical model of cortical networks involved in emotions related to different aspects of love. Developing this model in future studies should be helpful for advancing clinical approaches helpful in sexual medicine and couple therapy.

Taxonomic counts of cognition in the wild

In 1985, Kummer & Goodall pleaded for an ecology of intelligence and proposed that innovations might be a good way to measure cognition in the wild. Counts of innovation per taxonomic group are now available in hundreds of avian and primate species, as are counts of tactical deception, tool use and social learning. Robust evidence suggests that innovation rate and its neural correlates allow birds and mammals to cope better with environmental change. The positive correlations between taxonomic counts, and the increasing number of cognitive and neural measures found to be associated with ecological variables, suggest that domain general processes might be more pervasive than previously thought in the evolution of intelligence.

Understanding actions of others: the electrodynamics of the left and right hemispheres. A high-density EEG neuroimaging study

Background

When we observe an individual performing a motor act (e.g. grasping a cup) we get two types of information on the basis of how the motor act is done and the context: what the agent is doing (i.e. grasping) and the intention underlying it (i.e. grasping for drinking). Here we examined the temporal dynamics of the brain activations that follow the observation of a motor act and underlie the observer's capacity to understand what the agent is doing and why.

Methodology/Principal Findings

Volunteers were presented with two-frame video-clips. The first frame (T0) showed an object with or without context; the second frame (T1) showed a hand interacting with the object. The volunteers were instructed to understand the intention of the observed actions while their brain activity was recorded with a high-density 128-channel EEG system. Visual event-related potentials (VEPs) were recorded time-locked with the frame showing the hand-object interaction (T1). The data were analyzed by using electrical neuroimaging, which combines a cluster analysis performed on the group-averaged VEPs with the localization of the cortical sources that give rise to different spatio-temporal states of the global electrical field. Electrical neuroimaging results revealed four major steps: 1) bilateral posterior cortical activations; 2) a strong activation of the left posterior temporal and inferior parietal cortices with almost a complete disappearance of activations in the right hemisphere; 3) a significant increase of the activations of the right temporo-parietal region with simultaneously co-active left hemispheric sources, and 4) a significant global decrease of cortical activity accompanied by the appearance of activation of the orbito-frontal cortex.

Conclusions/Significance

We conclude that the early striking left hemisphere involvement is due to the activation of a lateralized action-observation/action execution network. The activation of this lateralized network mediates the understanding of the goal of object-directed motor acts (mirror mechanism). The successive right hemisphere activation indicates that this hemisphere plays an important role in understanding the intention of others.

A functional role for motor simulation in identifying tools

Embodied cognition promotes the involvement of the motor system in cognitive processing, such as tool identification. Although neuropsychological studies suggest that the motor system is not necessary for identifying tools, it may still have a functional role in tool recognition. To test this possibility, we used a motor interference task: Participants squeezed a rubber ball in one hand while naming pictures of tools and animals. Participants were faster and more accurate in naming the tools that were oriented with the handle facing away from the squeezing hand than in naming the tools that were oriented with the handle facing toward the squeezing hand. There was no effect of orientation for animals. Given that participants simulate grasping a tool with the hand closest to the handle, this result demonstrates that interfering with the ability to simulate grasping impairs tool naming and suggests that motor simulation has a functional role in tool identification.

Gesture discrimination in primary progressive aphasia: the intersection between gesture and language processing pathways

The issue of the relationship between language and gesture processing and the partial overlap of their neural representations is of fundamental importance to neurology, psychology, and social sciences. Patients suffering from primary progressive aphasia, a clinical syndrome characterized by comparatively isolated language deficits, may provide direct evidence for anatomical and functional association between specific language deficits and gesture discrimination deficits. A consecutive series of 16 patients with primary progressive aphasia and 16 matched control subjects participated. Our nonverbal gesture discrimination task consisted of 19 trials. In each trial, participants observed three video clips showing the same gesture performed correctly in one clip and incorrectly in the other two. Subjects had to indicate which of the three versions was correct. Language and gesture production were evaluated by means of conventional tasks. All participants underwent high-resolution structural and diffusion tensor magnetic resonance imaging. Ten of the primary progressive aphasia patients showed a significant deficit on the nonverbal gesture discrimination task. A factor analysis revealed that this deficit clustered with gesture imitation, word and pseudoword repetition, and writing-to-dictation. Individual scores on this cluster correlated with volume in the left anterior inferior parietal cortex extending into the posterior superior temporal gyrus. Probabilistic tractography indicated this region comprised the cortical relay station of the indirect pathway connecting the inferior frontal gyrus and the superior temporal cortex. Thus, the left perisylvian temporoparietal area may underpin verbal imitative behavior, gesture imitation, and gesture discrimination indicative of a partly shared neural substrate for language and gesture resonance.

Observing Learned Object-specific Functional Grasps Preferentially Activates the Ventral Stream

In one popular account of the human visual system, two streams are distinguished, a ventral stream specialized for perception and a dorsal stream specialized for action. The skillful use of familiar tools, however, is likely to involve the cooperation of both streams. Using functional magnetic resonance imaging, we scanned individuals while they viewed short movies of familiar tools being grasped in ways that were either consistent or inconsistent with how tools are typically grasped during use. Typical-for-use actions were predicted to preferentially activate parietal areas important for tool use. Instead, our results revealed several areas within the ventral stream, as well as the left posterior middle temporal gyrus, as preferentially active for our typical-for-use actions. We believe these findings reflect sensitivity to learned semantic associations and suggest a special role for these areas in representing object-specific actions. We hypothesize that during actual tool use a complex interplay between the two streams must take place, with ventral stream areas providing critical input as to how an object should be engaged in accordance with stored semantic knowledge.

Large-brained mammals live longer

Many mammals have brains substantially larger than expected for their body size, but the reasons for this remain ambiguous. Enlarged brains are metabolically expensive and require elongated developmental periods, and so natural selection should have favoured their evolution only if they provide counterbalancing advantages. One possible advantage is facilitating the construction of behavioural responses to unusual, novel or complex socio-ecological challenges. This buffer effect should increase survival rates and favour a longer reproductive life, thereby compensating for the costs of delayed reproduction. Here, using a global database of 493 species, we provide evidence showing that mammals with enlarged brains (relative to their body size) live longer and have a longer reproductive lifespan. Our analysis supports and extends previous findings, accounting for the possible confounding effects of other life history traits, ecological and dietary factors, and phylogenetic autocorrelation. Thus, these findings provide support for the hypothesis that mammals counterbalance the costs of affording large brains with a longer reproductive life.

Hearing living symbols and nonliving icons: category specificities in the cognitive processing of environmental sounds

The neurocognitive processing of environmental sounds and linguistic stimuli shares common semantic resources and can lead to the activation of motor programs for the generation of the passively heard sound or speech. We investigated the extent to which the cognition of environmental sounds, like that of language, relies on symbolic mental representations independent of the acoustic input. In a hierarchical sorting task, we found that evaluation of nonliving sounds is consistently biased toward a focus on acoustical information. However, the evaluation of living sounds focuses spontaneously on sound-independent semantic information, but can rely on acoustical information after exposure to a context consisting of nonliving sounds. We interpret these results as support for a robust iconic processing strategy for nonliving sounds and a flexible symbolic processing strategy for living sounds.

Meta-analysis of neuroimaging data

As the number of neuroimaging studies that investigate psychological phenomena grows, it becomes increasingly difficult to integrate the knowledge that has accrued across studies. Meta-analyses are designed to serve this purpose, as they allow the synthesis of findings not only across studies but also across laboratories and task variants. Meta-analyses are uniquely suited to answer questions about whether brain regions or networks are consistently associated with particular psychological domains, including broad categories such as working memory or more specific categories such as conditioned fear. Meta-analysis can also address questions of specificity, which pertains to whether activation of regions or networks is unique to a particular psychological domain, or is a feature of multiple types of tasks. This review discusses several techniques that have been used to test consistency and specificity in published neuroimaging data, including the kernel density analysis (KDA), activation likelihood estimate (ALE), and the recently developed multilevel kernel density analysis (MKDA). We discuss these techniques in light of current and future directions in the field. Copyright © 2010 John Wiley & Sons, Ltd. This article is categorized under: Neuroscience > Cognition.

Naming manipulable objects: anatomy of a category specific effect in left temporal tumours

Whether semantic knowledge is categorically organized or is based in an undifferentiated distributed network within the temporal lobes or it is at least partially organized in property-based networks is still an open issue. With a naming task involving living and nonliving entities, the latter divided according to degree of manipulability, we studied a group of 30 tumour patients with either right, left anterior or left posterior temporal lobes' lesions and a herpes simplex encephalitis patient (MU). Both cross-subject and cross-stimulus analyses were conducted. Left hemisphere patients were overall worse than both right hemisphere patients and controls in the naming task. They moreover named nonliving items worse than living. This effect was larger in left posterior temporal than both right temporal and also left anterior temporal patients and significant both at a cross-subject and cross-stimulus levels of analysis. In addition the left posterior temporal group had more difficulties with highly manipulable objects than left anterior temporal patients, but the effect was significant only on a cross-subject analysis. VLSM lesion analysis revealed that the area most critically associated with the larger naming deficit for manipulable objects was the posterior superior portion of the left temporal lobe, particularly the posterior middle temporal gyrus. These results support a 'property-based networks' account of semantic knowledge rather than an 'undifferentiated network' account. For manipulable objects, this would be a posterior-temporal/inferior-parietal left hemisphere "action/manipulation-property-based" network related to the dorsal pathways which is thought to be important in action control, as suggested by neuroimaging results.

A neurosemantic theory of concrete noun representation based on the underlying brain codes

This article describes the discovery of a set of biologically-driven semantic dimensions underlying the neural representation of concrete nouns, and then demonstrates how a resulting theory of noun representation can be used to identify simple thoughts through their fMRI patterns. We use factor analysis of fMRI brain imaging data to reveal the biological representation of individual concrete nouns like apple, in the absence of any pictorial stimuli. From this analysis emerge three main semantic factors underpinning the neural representation of nouns naming physical objects, which we label manipulation, shelter, and eating. Each factor is neurally represented in 3-4 different brain locations that correspond to a cortical network that co-activates in non-linguistic tasks, such as tool use pantomime for the manipulation factor. Several converging methods, such as the use of behavioral ratings of word meaning and text corpus characteristics, provide independent evidence of the centrality of these factors to the representations. The factors are then used with machine learning classifier techniques to show that the fMRI-measured brain representation of an individual concrete noun like apple can be identified with good accuracy from among 60 candidate words, using only the fMRI activity in the 16 locations associated with these factors. To further demonstrate the generativity of the proposed account, a theory-based model is developed to predict the brain activation patterns for words to which the algorithm has not been previously exposed. The methods, findings, and theory constitute a new approach of using brain activity for understanding how object concepts are represented in the mind.

Dissociating networks of imitation

The investigation of imitation, which consists of observation and later reproduction of voluntary actions, promises insights into the complex processes of human actions. Although several aspects concerning the component neural processes necessary for action execution are known, our current understanding of the neural networks underlying these remains sparse. The present study applies independent component analysis (ICA) to functional magnetic resonance imaging (fMRI) data acquired during imitation of abstract gestures and object-related actions. This enables identification of neural networks underlying the production of these imitations. The explorative approach of ICA is complemented by an analysis of time courses from the maxima of each component. Four independent networks were active during delayed imitation. These can be assigned to the aspects of (1) action perception, (2) motor preparation and action execution, (3) encoding and retrieval into and from working memory, as well as (4) the dynamic integration of object affordances into the action. At least two of these networks participate in action preparation, one contains areas involved with motor working memory and one includes areas which are connected to the true action execution. The fourth network only shows activity shortly before an object-related action is imitated. This indicates a late integration of object affordances into the movement as the time course of activity in this network pertains to action rather than perception of the object.

The impact of left hemisphere stroke on force control with familiar and novel objects: neuroanatomic substrates and relationship to apraxia

Fingertip force scaling for lifting objects frequently occurs in anticipation of finger contact. An ongoing question concerns the types of memories that are used to inform predictive control. Object-specific information such as weight may be stored and retrieved when previously encountered objects are lifted again. Alternatively, visual size and shape cues may provide estimates of object density each time objects are encountered. We reasoned that differences in performance with familiar versus novel objects would provide support for the former possibility. Anticipatory force production with both familiar and novel objects was assessed in six left hemisphere stroke patients, two of whom exhibited deficient actions with familiar objects (ideomotor apraxia; IMA), along with five control subjects. In contrast to healthy controls and stroke participants without IMA, participants with IMA displayed poor anticipatory scaling with familiar objects. However, like the other groups, IMA participants learned to differentiate fingertip forces with repeated lifts of both familiar and novel objects. Finally, there was a significant correlation between damage to the inferior parietal and superior and middle temporal lobes and impaired anticipatory control for familiar objects. These data support the hypotheses that anticipatory control during lifts of familiar objects in IMA patients are based on object-specific memories and that the ventro-dorsal stream is involved in the long-term storage of internal models used for anticipatory scaling during object manipulation.

Gray and white matter changes associated with tool-use learning in macaque monkeys

We used noninvasive MRI and voxel-based morphometry (VBM) to detect changes in brain structure in three adult Japanese macaques trained to use a rake to retrieve food rewards. Monkeys, who were naive to any previous tool use, were scanned repeatedly in a 4-T scanner over 6 weeks, comprising 2 weeks of habituation followed by 2 weeks of intensive daily training and a 2-week posttraining period. VBM analysis revealed significant increases in gray matter with rake performance across the three monkeys. The effects were most significant (P < 0.05 corrected for multiple comparisons across the whole brain) in the right superior temporal sulcus, right second somatosensory area, and right intraparietal sulcus, with less significant effects (P < 0.001 uncorrected) in these same regions of the left hemisphere. Bilateral increases were also observed in the white matter of the cerebellar hemisphere in lobule 5. In two of the monkeys who exhibited rapid learning of the rake task, gray matter volume in peak voxels increased by up to 17% during the intensive training period; the earliest changes were seen after 1 week of intensive training, and they generally peaked when performance on the task plateaued. In the third monkey, who was slower to learn the task, peak voxels showed no systematic changes. Thus, VBM can detect significant brain changes in individual trained monkeys exposed to tool-use training for the first time. This approach could open up a means of investigating the underlying neurobiology of motor learning and other higher brain functions in individual animals.

The representation of tool use in humans and monkeys: common and uniquely human features

Though other species of primates also use tools, humans appear unique in their capacity to understand the causal relationship between tools and the result of their use. In a comparative fMRI study, we scanned a large cohort of human volunteers and untrained monkeys, as well as two monkeys trained to use tools, while they observed hand actions and actions performed using simple tools. In both species, the observation of an action, regardless of how performed, activated occipitotemporal, intraparietal, and ventral premotor cortex, bilaterally. In humans, the observation of actions done with simple tools yielded an additional, specific activation of a rostral sector of the left inferior parietal lobule (IPL). This latter site was considered human-specific, as it was not observed in monkey IPL for any of the tool videos presented, even after monkeys had become proficient in using a rake or pliers through extensive training. In conclusion, while the observation of a grasping hand activated similar regions in humans and monkeys, an additional specific sector of IPL devoted to tool use has evolved in Homo sapiens, although tool-specific neurons might reside in the monkey grasping regions. These results shed new light on the changes of the hominid brain during evolution.

Category-specific neural processing for naming pictures of animals and naming pictures of tools: an ALE meta-analysis

Using activation-likelihood estimation (ALE) meta-analysis, we identified brain areas that are invoked when people name pictures of animals and pictures of tools. We found that naming animals and naming tools invoked separate distributed networks in the brain. Specifically, we found that naming animals invoked greater responses than naming tools in frontal lobe structures that are typically modulated by emotional content and task demands, and in a number of visual areas in the ventral stream. In contrast, naming tools invoked greater responses in a different set of areas in the ventral stream than those invoked by naming animals. Naming tools also invoked greater responses than naming animals in motor areas in the frontal lobe as well as in sensory areas in the parietal lobe. The only overlapping sites of activation that we found for naming these two categories of objects were in the left pars triangularis, the left inferior temporal gyrus, and the left parahippocampal gyrus. Taken together, our meta-analysis reveals that animals and tools are categorically represented in visual areas but show convergence in higher-order associative areas in the temporal and frontal lobes in regions that are typically regarded as being involved in memory and/or semantic processing. Our results also reveal that naming tools not only engages visual areas in the ventral stream but also a fronto-parietal network associated with tool use. Whether or not this network associated with tool use contributes directly to recognition will require further investigation.

Neural integration of iconic and unrelated coverbal gestures: a functional MRI study

Gestures are an important part of interpersonal communication, for example by illustrating physical properties of speech contents (e.g., "the ball is round"). The meaning of these so-called iconic gestures is strongly intertwined with speech. We investigated the neural correlates of the semantic integration for verbal and gestural information. Participants watched short videos of five speech and gesture conditions performed by an actor, including variation of language (familiar German vs. unfamiliar Russian), variation of gesture (iconic vs. unrelated), as well as isolated familiar language, while brain activation was measured using functional magnetic resonance imaging. For familiar speech with either of both gesture types contrasted to Russian speech-gesture pairs, activation increases were observed at the left temporo-occipital junction. Apart from this shared location, speech with iconic gestures exclusively engaged left occipital areas, whereas speech with unrelated gestures activated bilateral parietal and posterior temporal regions. Our results demonstrate that the processing of speech with speech-related versus speech-unrelated gestures occurs in two distinct but partly overlapping networks. The distinct processing streams (visual versus linguistic/spatial) are interpreted in terms of "auxiliary systems" allowing the integration of speech and gesture in the left temporo-occipital region.

The posterior parietal cortex and non-spatial cognition

The primate posterior parietal cortex (PPC) processes information related to environmental physical space. The human PPC has apparently expanded not only in size but also in its functional range to encompass certain abstract and higher-order conceptual spaces. In this report, we review various forms of non-spatial representation in the PPC. These forms are presented roughly in order of the level of abstraction of the 'objects' and pseudo-spatial relations represented. Also, we consider mechanisms that could have enabled the hominid PPC to establish such representations. Lastly, we offer a general principle to unify the newer forms of representation with the original functions of the PPC.

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

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

Simulation, situated conceptualization, and prediction

Based on accumulating evidence, simulation appears to be a basic computational mechanism in the brain that supports a broad spectrum of processes from perception to social cognition. Further evidence suggests that simulation is typically situated, with the situated character of experience in the environment being reflected in the situated character of the representations that underlie simulation. A basic architecture is sketched of how the brain implements situated simulation. Within this framework, simulators implement the concepts that underlie knowledge, and situated conceptualizations capture patterns of multi-modal simulation associated with frequently experienced situations. A pattern completion inference mechanism uses current perception to activate situated conceptualizations that produce predictions via simulations on relevant modalities. Empirical findings from perception, action, working memory, conceptual processing, language and social cognition illustrate how this framework produces the extensive prediction that characterizes natural intelligence.

Brain regions related to tool use and action knowledge reflect nicotine dependence

In addition to reward- and craving-related processes, habitual mechanisms play an important role in addiction. While the dorsal striatum has been proposed to code for the motivational state of habitual drug-seeking actions, the neural underpinnings of the corresponding drug-taking skills and action knowledge remain poorly understood. We used functional magnetic resonance imaging (fMRI) and a behavioral orientation affordance paradigm to investigate the neural and behavioral correlates of automatized drug-taking actions in nicotine dependence. Smokers exhibited higher fMRI activations than nonsmokers when viewing smoking-related but not when viewing control images. These group differences in fMRI activations were located not only in brain regions associated with craving and habitual learning (left ventral and dorsal striatum, dorsolateral prefrontal cortex, insula, uncus, medial frontal gyrus, right subcallosal gyrus, and bilateral parahippocampal gyrus), but also in a network of brain regions which has been strongly implicated in the encoding of action knowledge and tool use skills (bilateral premotor cortex, left superior parietal lobule, and right lateral cerebellum). A behavioral affordance reaction-time task indicated that smokers, but not nonsmokers, showed an automatized responsiveness to smoking paraphernalia similar to everyday objects. Moreover, smokers showed strong intercorrelations between fMRI activations in tool use-related brain regions, behavioral responsiveness to smoking-related cues, and severity of nicotine dependence. Apparently smoking-related action representations in smokers are stored in brain regions typically representing tool use skills and action knowledge. Most importantly, cortical and behavioral correlates of the respective drug-taking skills vary with the individual degree of nicotine dependence.

Human cortical organization for processing vocalizations indicates representation of harmonic structure as a signal attribute

The ability to detect and rapidly process harmonic sounds, which in nature are typical of animal vocalizations and speech, can be critical for communication among conspecifics and for survival. Single-unit studies have reported neurons in auditory cortex sensitive to specific combinations of frequencies (e.g., harmonics), theorized to rapidly abstract or filter for specific structures of incoming sounds, where large ensembles of such neurons may constitute spectral templates. We studied the contribution of harmonic structure to activation of putative spectral templates in human auditory cortex by using a wide variety of animal vocalizations, as well as artificially constructed iterated rippled noises (IRNs). Both the IRNs and vocalization sounds were quantitatively characterized by calculating a global harmonics-to-noise ratio (HNR). Using functional MRI, we identified HNR-sensitive regions when presenting either artificial IRNs and/or recordings of natural animal vocalizations. This activation included regions situated between functionally defined primary auditory cortices and regions preferential for processing human nonverbal vocalizations or speech sounds. These results demonstrate that the HNR of sound reflects an important second-order acoustic signal attribute that parametrically activates distinct pathways of human auditory cortex. Thus, these results provide novel support for the presence of spectral templates, which may subserve a major role in the hierarchical processing of vocalizations as a distinct category of behaviorally relevant sound.

Tool use and physical cognition in birds and mammals

In the wild, chimpanzees are the most prolific and proficient tool users, yet their understanding of tools in the laboratory is surprisingly poor. Although this apparent lack of understanding might be interpreted as a reflection of a general failure of animals to appreciate 'folk physics', recent studies suggest that some non-tool using species perform rather well on such laboratory tasks. In some animals, tool use and manufacture may also engage aspects of planning, but some non-tool using species have also been shown to demonstrate prospective cognition. Consequently, we argue that habitual tool use is not a clear predictor of physical intelligence, for either instrumental tool tasks or tests of planning.

Concepts and categories: a cognitive neuropsychological perspective

One of the most provocative and exciting issues in cognitive science is how neural specificity for semantic categories of common objects arises in the functional architecture of the brain. More than two decades of research on the neuropsychological phenomenon of category-specific semantic deficits has generated detailed claims about the organization and representation of conceptual knowledge. More recently, researchers have sought to test hypotheses developed on the basis of neuropsychological evidence with functional imaging. From those two fields, the empirical generalization emerges that object domain and sensory modality jointly constrain the organization of knowledge in the brain. At the same time, research within the embodied cognition framework has highlighted the need to articulate how information is communicated between the sensory and motor systems, and processes that represent and generalize abstract information. Those developments point toward a new approach for understanding category specificity in terms of the coordinated influences of diverse regions and cognitive systems.

Evaluating the consistency and specificity of neuroimaging data using meta-analysis

Making sense of a neuroimaging literature that is growing in scope and complexity will require increasingly sophisticated tools for synthesizing findings across studies. Meta-analysis of neuroimaging studies fills a unique niche in this process: It can be used to evaluate the consistency of findings across different laboratories and task variants, and it can be used to evaluate the specificity of findings in brain regions or networks to particular task types. This review discusses examples, implementation, and considerations when choosing meta-analytic techniques. It focuses on the multilevel kernel density analysis (MKDA) framework, which has been used in recent studies to evaluate consistency and specificity of regional activation, identify distributed functional networks from patterns of co-activation, and test hypotheses about functional cortical-subcortical pathways in healthy individuals and patients with mental disorders. Several tests of consistency and specificity are described.

The adaptive value of tool-aided defense against wild animal attacks

Throughout history humans have faced the persistent threat of attacks by wild animals, and how humans respond to this problem can make the difference between survival and death. In theory, the use of tools to fend off animal attacks would be more effective than resisting bare-handed, yet evidence for the advantage of tool-aided defense is scarce and equivocal. Two studies of news accounts of wild animal attacks against humans were conducted to test the hypothesis that tool-aided defense is indeed associated with reductions in injuries and deaths. Results of both Study 1 (N=172) and Study 2 (N=370) supported the hypothesis. The observed survival advantage of tool-aided defense for modern humans suggests that this tactic also would have worked for human ancestors who lived more closely to dangerous wild animals.