Neural correlates of grasping

Prehension, the capacity to reach and grasp objects, comprises two main components: reaching, i.e., moving the hand towards an object, and grasping, i.e., shaping the hand with respect to its properties. Knowledge of this topic has gained a huge advance in recent years, dramatically changing our view on how prehension is represented within the dorsal stream. While our understanding of the various nodes coding the grasp component is rapidly progressing, little is known of the integration between grasping and reaching. With this Mini Review we aim to provide an up-to-date overview of the recent developments on the coding of prehension. We will start with a description of the regions coding various aspects of grasping in humans and monkeys, delineating where it might be integrated with reaching. To gain insights into the causal role of these nodes in the coding of prehension, we will link this functional description to lesion studies. Finally, we will discuss future directions that might be promising to unveil new insights on the coding of prehension movements

Cortical Sensorimotor Mechanisms for Neural Control of Skilled Manipulation

abstract: The human hand is a complex biological system. Humans have evolved a unique ability to use the hand for a wide range of tasks, including activities of daily living such as successfully grasping and manipulating objects, i.e., lifting a cup of coffee without spilling. Despite the ubiquitous nature of hand use in everyday activities involving object manipulations, there is currently an incomplete understanding of the cortical sensorimotor mechanisms underlying this important behavior. One critical aspect of natural object grasping is the coordination of where the fingers make contact with an object and how much force is applied following contact. Such force-to-position modulation is critical for successful manipulation. However, the neural mechanisms underlying these motor processes remain less understood, as previous experiments have utilized protocols with fixed contact points which likely rely on different neural mechanisms from those involved in grasping at unconstrained contacts. To address this gap in the motor neuroscience field, transcranial magnetic stimulation (TMS) and electroencephalography (EEG) were used to investigate the role of primary motor cortex (M1), as well as other important cortical regions in the grasping network, during the planning and execution of object grasping and manipulation. The results of virtual lesions induced by TMS and EEG revealed grasp context-specific cortical mechanisms underlying digit force-to-position coordination, as well as the spatial and temporal dynamics of cortical activity during planning and execution. Together, the present findings provide the foundation for a novel framework accounting for how the central nervous system controls dexterous manipulation. This new knowledge can potentially benefit research in neuroprosthetics and improve the efficacy of neurorehabilitation techniques for patients affected by sensorimotor impairments.Dissertation/ThesisDoctoral Dissertation Neuroscience 201

Neurophysiological Investigation of the Functional Interactions between Manual Action Control and Working Memory

Gündüz Can R. Neurophysiological Investigation of the Functional Interactions between Manual Action Control and Working Memory. Bielefeld: Universität Bielefeld; 2020

Unsupervised decoding of long-term, naturalistic human neural recordings with automated video and audio annotations

Fully automated decoding of human activities and intentions from direct neural recordings is a tantalizing challenge in brain-computer interfacing. Most ongoing efforts have focused on training decoders on specific, stereotyped tasks in laboratory settings. Implementing brain-computer interfaces (BCIs) in natural settings requires adaptive strategies and scalable algorithms that require minimal supervision. Here we propose an unsupervised approach to decoding neural states from human brain recordings acquired in a naturalistic context. We demonstrate our approach on continuous long-term electrocorticographic (ECoG) data recorded over many days from the brain surface of subjects in a hospital room, with simultaneous audio and video recordings. We first discovered clusters in high-dimensional ECoG recordings and then annotated coherent clusters using speech and movement labels extracted automatically from audio and video recordings. To our knowledge, this represents the first time techniques from computer vision and speech processing have been used for natural ECoG decoding. Our results show that our unsupervised approach can discover distinct behaviors from ECoG data, including moving, speaking and resting. We verify the accuracy of our approach by comparing to manual annotations. Projecting the discovered cluster centers back onto the brain, this technique opens the door to automated functional brain mapping in natural settings

Time course and specificity of sensory-motor alpha modulation during the observation of hand motor acts and gestures: a high density EEG study

The main aim of the present study was to explore, by means of high-density EEG, the intensity and the temporal pattern of event-related sensory-motor alpha desynchronization (ERD) during the observation of different types of hand motor acts and gestures. In particular, we aimed to investigate whether the sensory-motor ERD would show a specific modulation during the observation of hand behaviors differing for goal-relatedness (hand grasping of an object and meaningless hand movements) and social relevance (communicative hand gestures and grasping within a social context). Time course analysis of alpha suppression showed that all types of hand behaviors were effective in triggering sensory-motor alpha ERD, but to a different degree depending on the category of observed hand motor acts and gestures. Meaningless gestures and hand grasping were the most effective stimuli, resulting in the strongest ERD. The observation of social hand behaviors such as social grasping and communicative gestures, triggered a more dynamic time course of ERD compared to that driven by the observation of simple grasping and meaningless gestures. These findings indicate that the observation of hand motor acts and gestures evoke the activation of a motor resonance mechanism that differs on the basis of the goal-relatedness and the social relevance of the observed hand behavior

Dissociating neural activity associated with the subjective phenomenology of monocular stereopsis : an EEG study

Support for DV and MU was provided by the Leverhulme Trust Research Project Grant (Grant Reference RGP-2016-269).The subjective phenomenology associated with stereopsis, of solid tangible objects separated by a palpable negative space, is conventionally thought to be a by-product of the derivation of depth from binocular disparity. However, the same qualitative impression has been reported in the absence of disparity, e.g., when viewing pictorial images monocularly through an aperture. Here we aimed to explore if we could identify dissociable neural activity associated with the qualitative impression of stereopsis, in the absence of the processing of binocular disparities. We measured EEG activity while subjects viewed pictorial (non-stereoscopic) images of 2D and 3D geometric forms under four different viewing conditions (Binocular, Monocular, Binocular aperture, Monocular aperture). EEG activity was analysed by oscillatory source localization (beamformer technique) to examine power change in occipital and parietal regions across viewing and stimulus conditions in targeted frequency bands (alpha: 8–13Hz & gamma: 60–90Hz). We observed expected event-related gamma synchronization and alpha desynchronization in occipital cortex and predominant gamma synchronization in parietal cortex across viewing and stimulus conditions. However, only the viewing condition predicted to generate the strongest impression of stereopsis (monocular aperture) revealed significantly elevated gamma synchronization within the parietal cortex for the critical contrasts (3D vs. 2D form). These findings suggest dissociable neural processes specific to the qualitative impression of stereopsis as distinguished from disparity processing.PostprintPeer reviewe

Motor observation, motor performance, and motor imagery : an ERP study.

Two major theoretical models, Direct Mapping and Functional Equivalence, suggest that the observation of action and imagery of action, respectively, involve activation of similar motor related areas. Despite the wealth of evidence that supports these two perspectives, the degree to which these motor-related actions overlap is still only vaguely defined. The present investigation sought to assess both the spatial and temporal characteristics of the brain activity involved in these motor related conditions. Specifically, the present study used ERP technology to assess the neural substrates of Motor Observation, Motor Performance, and Motor Imagery. Participants viewed images depicting two human grasping motions, whole hand grasping or precision finger-to-thumb grasping. Participants were to report, perform, or imagine performing the observed action depicted in the target image. Ongoing EEG was time-locked to the presentation of the target image. The EEG data were filtered, segmented, submitted to a series of artifact correction procedures, then averaged. Subsequently, the averaged data were subject a two-step sequential principal component analysis. These were then subjected to repeated measures ANOVAs. Additional analyses included amplitude and latency measures, obtained from selected regions across different conditions. These measures were compared and examined for group differences. In addition, Low Resolution Brain Electromagnetic Tomography was used to elucidate the underlying neural activity. Specifically, all three of the motor related experimental conditions were expected to show increased activation of motor related areas on the contralateral hemisphere (left hemisphere) to the instructed action, particularly in the Primary Motor Cortex and Primary Somatosensory Cortex, and increased activation in the Supplementary Motor Area, relative to a nonmotor control condition. However, the statistical analyses failed to support these hypotheses. In the end, a greater understanding of these processes through scientific advances further develops and improves both interventions and treatments aimed at bettering the lives of those suffering from a myriad of psychological, physical and psychophysical disorders resulting from many psychobiological causes including stroke, dismemberment, physical injury, and cognitive dysfunction. While the present study failed to further elucidate these neural mechanisms, this area of study is increasingly important and beneficial to wide ranging areas of medicine, neuroscience, and cognitive and sports psychology

Reach to grasp movement: a simultaneous recording approach

In our everyday life, we interact continually with objects. We reach for them, we grasp them, we manipulate them. All these actions are apparently very simple. Yet, this is not so. The mechanisms that underlie them are complex, and require multiple visuomotor transformations entailing the capacity to transform the visual features of the object in the appropriate hand configuration, and the capacity to execute and control hand and finger movements. In neural terms, grasping behavior can be dissociated into separate reach and grip components. According to this view, computations regarding the grasp component occurs within a lateral parietofrontal circuit involving the anterior intraparietal area (AIP) and both the dorsal (PMd) and the ventral (PMv) premotor areas. The general agreement is that the processes occurring in AIP constitute the initial step of the transformation leading from representation of objects to movement aimed at interacting with such objects. Evidence supporting this view comes from neurophysiological studies showing that the representation of three-dimensional object features influences both the rostral sector of the ventral premotor cortex (area F5) and the ventro-rostral sector of the dorsal premotor area (area F2vr; for review see Filimon, 2010). With respect to the reach component, there is agreement that it is subserved by a more medial parieto-frontal circuit including the medial intraparietal area (mIP) termed as the parietal reach region (PRR), area V6A, and the dorsal premotor area F2. Human neuroimaging studies go in the same direction. They showed the involvement of the anterior portion of the human AIP in grasping behavior and they proposed human homologues of both the ventral and dorsal premotor cortices during grasping. Whereas, reaching activates the medial intraparietal and the superior parieto-occipital cortex (for review see Castiello & Begliomini, 2008). Altogether these studies suggest that in humans, like in monkeys, reach to grasp movements involve a large network of interconnected structures in the parietal and frontal lobes. And, that this cortical network is differentially involved for the control of distinct aspects characterizing the planning and the control of reach to grasp movement. Nevertheless, how the neural control systems interact with the complex biomechanics of moving limbs - as to help us to identify the operational principles to look for in reach to grasp studies and, more in general, in motor control - remains an open question. In this respect, it is only through the use of converging techniques with different characteristics that we might fully understand how the human brain controls the grasping function. What is so far lacking in the literature on cortical control of grasp in humans is a systematic documentation of the time course of neural activity during performance of reach to grasp movement. To fill this gap the present thesis will consider the co-registration of behavioural and neural events in order to provide deeper insights into the neuro-functional basis of reach to grasp movements in humans. In Chapter 1 an overview on the state of the art in many disciplines investigating reach to grasp processes will be provided, with particular attention to neurophysiology, from which most of the knowledge regarding the neural underpinnings of reach to grasp movements comes from. Furthermore, kinematical as well as neuroimaging, and evoked related potentials (ERP) investigations will be reviewed. Particular emphasis will be given to neuroimaging studies, especially those exploring grasping movements by functional magnetic resonance imaging (fMRI), as the technique adopted to conduct the studies presented in this thesis (Chapter 1). Basic principles of co-registration techniques, which are at the core of the methodological aspect of the present thesis, will be reviewed (Chapter 2). In this respect, a description of the methodologies adopted in the present thesis together with general information regarding signal processing and data analysis for these different techniques will be provided in specific appendices (III, IV). Then, three studies focusing on the co-registration of kinematical with ERP (Chapters 3 and 4) and FMRI with ERP (Chapter 5) will be presented and discussed. In Chapter 3 the co-registration of ERP and kinematical signals will be considered with specific reference to hand shaping, that is the grasp component of the targeted movement. A similar co-registration approach will be adopted in Chapter 4 for investigating the underlying circuits of reaching. The focus for Chapter 5 will be the co-registration of ERPs and fMRI signals as to reveal the time course of activation of the differential cortical areas related to the planning, initiation and on-line control of reaching and grasping movements and how such activity varies depending on object size. A general discussion (Chapter 6), contextualizing the results obtained by the studies presented in this thesis will follow

Action observation and motor imagery in performance of complex movements: Evidence from EEG and kinematics analysis

Motor imagery (MI) and action observation (AO) are considered effective cognitive tools for motor learning, but little work directly compared their cortical activation correlate in relation with subsequent performance. We compared AO and MI in promoting early learning of a complex four-limb, hand?foot coordination task, using electroencephalographic (EEG) and kinematic analysis. Thirty healthy subjects were randomly assigned into three groups to perform a training period in which AO watched a video of the task, MI had to imagine it, and Control (C) was involved in a distracting computation task. Subjects were then asked to actually perform the motor task with kinematic measurement of error time with respect to the correct motor performance. EEG was recorded during baseline, training and task execution, with task-related power (TRPow) calculation for sensorimotor (alpha and beta) rhythms reactive with respect to rest. During training, the AO group had a stronger alpha desynchronization than the MI and C over frontocentral and bilateral parietal areas. However, during task execution, AO group had greater beta synchronization over bilateral parietal regions than MI and C groups. This beta synchrony furthermore demonstrated the strongest association with kinematic errors, which was also significantly lower in AO than in MI. These data suggest that sensorimotor activation elicited by action observation enhanced motor learning according to motor performance, corresponding to a more efficient activation of cortical resources during task execution. Action observation may be more effective than motor imagery in promoting early learning of a new complex coordination task

The cognitive neuroscience of prehension: recent developments

Prehension, the capacity to reach and grasp, is the key behavior that allows humans to change their environment. It continues to serve as a remarkable experimental test case for probing the cognitive architecture of goal-oriented action. This review focuses on recent experimental evidence that enhances or modifies how we might conceptualize the neural substrates of prehension. Emphasis is placed on studies that consider how precision grasps are selected and transformed into motor commands. Then, the mechanisms that extract action relevant information from vision and touch are considered. These include consideration of how parallel perceptual networks within parietal cortex, along with the ventral stream, are connected and share information to achieve common motor goals. On-line control of grasping action is discussed within a state estimation framework. The review ends with a consideration about how prehension fits within larger action repertoires that solve more complex goals and the possible cortical architectures needed to organize these actions