Right-hand Button Press Research Articles

The functional significance of the skilled performance positivity: An update

The skilled performance positivity (SPP) emerges approximately 450ms after button presses in a skilled performance task (SPT) where the participant is required to initiate a visual sweep with a left-hand button press and then stop it with a right-hand button press within a predetermined time frame (ranging from 40 to 60ms). The SPP has been thought to represent appraisal of performance results independent of the reafferent activity, and reported to reduce in amplitude following inaccurate timing performance. We hypothesized that reduced SPP on incorrect trials merely indicates superimposition of the feedback-related negativity (FRN) that is elicited by negative outcomes, because the right-hand button press not only stops the visual sweep but also presents visual feedback. Further, we assumed that the SPP essentially represents a P300 elicited by the visual feedback. To address these questions, we compared the SPT condition and a delayed-feedback (DFB) condition where feedback was presented approximately 1s after the left-hand button press. We observed the SPP only in the SPT condition, and found feedback-elicited P300s in the DFB condition. Both of these positivities shared a similar scalp distribution. We also replicated the reduced SPP on incorrect trials that shared a similar topography with the FRN elicited by the negative feedback. According to these findings, it is reasonable to conclude that the SPP represents the feedback-elicited P300, and after incorrect performance an FRN is superimposed on it.

Channel selection and classification of electroencephalogram signals: An artificial neural network and genetic algorithm-based approach

An electroencephalogram-based (EEG-based) brain-computer-interface (BCI) provides a new communication channel between the human brain and a computer. Amongst the various available techniques, artificial neural networks (ANNs) are well established in BCI research and have numerous successful applications. However, one of the drawbacks of conventional ANNs is the lack of an explicit input optimization mechanism. In addition, results of ANN learning are usually not easily interpretable. In this paper, we have applied an ANN-based method, the genetic neural mathematic method (GNMM), to two EEG channel selection and classification problems, aiming to address the issues above. Pre-processing steps include: least-square (LS) approximation to determine the overall signal increase/decrease rate; locally weighted polynomial regression (Loess) and fast Fourier transform (FFT) to smooth the signals to determine the signal strength and variations. The GNMM method consists of three successive steps: (1) a genetic algorithm-based (GA-based) input selection process; (2) multi-layer perceptron-based (MLP-based) modelling; and (3) rule extraction based upon successful training. The fitness function used in the GA is the training error when an MLP is trained for a limited number of epochs. By averaging the appearance of a particular channel in the winning chromosome over several runs, we were able to minimize the error due to randomness and to obtain an energy distribution around the scalp. In the second step, a threshold was used to select a subset of channels to be fed into an MLP, which performed modelling with a large number of iterations, thus fine-tuning the input/output relationship. Upon successful training, neurons in the input layer are divided into four sub-spaces to produce if-then rules (step 3). Two datasets were used as case studies to perform three classifications. The first data were electrocorticography (ECoG) recordings that have been used in the BCI competition III. The data belonged to two categories, imagined movements of either a finger or the tongue. The data were recorded using an 8 × 8 ECoG platinum electrode grid at a sampling rate of 1000 Hz for a total of 378 trials. The second dataset consisted of a 32-channel, 256 Hz EEG recording of 960 trials where participants had to execute a left- or right-hand button-press in response to left- or right-pointing arrow stimuli. The data were used to classify correct/incorrect responses and left/right hand movements. For the first dataset, 100 samples were reserved for testing, and those remaining were for training and validation with a ratio of 90%:10% using K-fold cross-validation. Using the top 10 channels selected by GNMM, we achieved a classification accuracy of 0.80 ± 0.04 for the testing dataset, which compares favourably with results reported in the literature. For the second case, we performed multi-time-windows pre-processing over a single trial. By selecting 6 channels out of 32, we were able to achieve a classification accuracy of about 0.86 for the response correctness classification and 0.82 for the actual responding hand classification, respectively. Furthermore, 139 regression rules were identified after training was completed. We demonstrate that GNMM is able to perform effective channel selections/reductions, which not only reduces the difficulty of data collection, but also greatly improves the generalization of the classifier. An important step that affects the effectiveness of GNMM is the pre-processing method. In this paper, we also highlight the importance of choosing an appropriate time window position.

EEG dipole analysis of motor-priming foreperiod activity reveals separate sources for motor and spatial attention components

Objective This study employed EEG source localisation procedures to study the contribution of motor preparatory and attentional processing to foreperiod activity in an S1–S2 motor priming task. Methods Behavioural and high-density event-related potential (ERP) data were recorded in an S1–S2 priming task where participants responded to S2 with a left or right-hand button press. S1 either provided information about response hand (informative) or ambiguous information (uninformative). Results Responses were significantly faster in informative trials compared with uninformative trials. Dipole source analysis of foreperiod lateralized ERPs revealed sources of motor preparatory activity in the dorsolateral premotor cortex (PMd) in line with previous work. In addition, two spatial attention components (ADAN, LDAP) were identified with generators in the PMd and occipitotemporal visual areas in the middle temporal (MT) region, respectively. Separation of motor-related and attentional PMd source locations was reliable along the rostral–caudal axis. Conclusions The presence of attentional components in a motor priming paradigm supports the premotor theory of attention which suggests a close link between attention and motor preparatory processes. Separation of components in the premotor cortex is in accord with a functional division of PMd into rostral (higher-order processing) and caudal (motor-related processing) areas as suggested by imaging work. Significance A prime for response preparation is a trigger for separate, but closely linked, attention-related activity in premotor areas.

Motor processing after movement execution as revealed by evoked and induced activity

Event-related synchronization (ERS) in the beta frequency band following movement execution has shown that motor processing is not completed yet when a movement ends. It is known that induced and evoked activities reflect different aspects of cortical processing which may result in different time courses. In the current study, we analyzed topography of postimperative negative variation (PINV) in 39 healthy right-handed adolescents in an acoustic forewarned reaction time (contingent negative variation, CNV) task using a 64-electrode high-density sensor array. We dissociated different PINV components in their time course from postmovement beta ERS in order to provide fundamental knowledge about evoked and induced EEG components after movement execution as a basis for further analysis of postmovement processing. A postmovement negativity occurred from about 500 to 1200 ms after the imperative stimulus (peaking about 600 ms after a right-hand button press) at central electrodes, contralateral to the response movement side. Current source density (CSD) analysis confirmed the current sinks over motor areas [contralateral primary motor/premotor and supplementary/cingulate motor area]. The described DC component (motor PINV, mPINV) differed in time course and localization from later “classical” PINV (cPINV) which is thought to reflect contingency reappraisal. mPINV could also be distinguished topographically from a mere delayed CNV resolution. When mPINV and ERS at the same left central electrode were compared, both parameters showed different time courses. Left central mPINV rather paralleled ERS at midcentral electrodes. Therefore, we suggest that the topography of mPINV provides first hints towards an involvement of contralateral primary motor cortex in postmovement processing beyond a mere idling state as reflected by later beta ERS. mPINV could be a useful tool to investigate the role of primary motor cortex in motor-learning processes. The combined analysis of induced and evoked activities seems to be able to elucidate different aspects of cortical connectivity and motor processes following movement.

Motor processing after movement execution as revealed by evoked and induced activity

Event-related synchronization (ERS) in the beta frequency band following movement execution has shown that motor processing is not completed yet when a movement ends. It is known that induced and evoked activities reflect different aspects of cortical processing which may result in different time courses. In the current study, we analyzed topography of postimperative negative variation (PINV) in 39 healthy right-handed adolescents in an acoustic forewarned reaction time (contingent negative variation, CNV) task using a 64-electrode high-density sensor array. We dissociated different PINV components in their time course from postmovement beta ERS in order to provide fundamental knowledge about evoked and induced EEG components after movement execution as a basis for further analysis of postmovement processing. A postmovement negativity occurred from about 500 to 1200 ms after the imperative stimulus (peaking about 600 ms after a right-hand button press) at central electrodes, contralateral to the response movement side. Current source density (CSD) analysis confirmed the current sinks over motor areas [contralateral primary motor/premotor and supplementary/cingulate motor area]. The described DC component (motor PINV, mPINV) differed in time course and localization from later “classical” PINV (cPINV) which is thought to reflect contingency reappraisal. mPINV could also be distinguished topographically from a mere delayed CNV resolution. When mPINV and ERS at the same left central electrode were compared, both parameters showed different time courses. Left central mPINV rather paralleled ERS at midcentral electrodes. Therefore, we suggest that the topography of mPINV provides first hints towards an involvement of contralateral primary motor cortex in postmovement processing beyond a mere idling state as reflected by later beta ERS. mPINV could be a useful tool to investigate the role of primary motor cortex in motor-learning processes. The combined analysis of induced and evoked activities seems to be able to elucidate different aspects of cortical connectivity and motor processes following movement.

Motor area activity during mental rotation studied by time-resolved single-trial fMRI.

The functional equivalence of overt movements and dynamic imagery is of fundamental importance in neuroscience. Here, we investigated the participation of the neocortical motor areas in a classic task of dynamic imagery, Shepard and Metzler's mental rotation task, by time-resolved single-trial functional Magnetic Resonance Imaging (fMRI). The subjects performed the mental-rotation task 16 times, each time with different object pairs. Functional images were acquired for each pair separately, and the onset times and widths of the activation peaks in each area of interest were compared to the response times. We found a bilateral involvement of the superior parietal lobule, lateral premotor area, and supplementary motor area in all subjects; we found, furthermore, that those areas likely participate in the very act of mental rotation. We also found an activation in the left primary motor cortex, which seemed to be associated with the right-hand button press at the end of the task period.

Scalp Topography of Event-related Brain Potentials and Cognitive Transition during Childhood

This study examined the relation between cognitive development and the ontogenesis of event-related brain potentials (ERPs) during childhood. First, the level of cognitive development was assessed in girls between 5 and 7 years of age with a standard Piagetian conservation kit. Then these children performed 2 experimental tasks: a visual selective attention (oddball) task and an experimental analogue of the Piagetian conservation of liquid quantity task. The oddball task required the child to count silently the number of rare stimuli presented in a series of frequent stimuli. The ERPs elicited in this task showed a positive wave with a centroparietal scalp distribution and a maximum amplitude at around 600 ms poststimulus. In the experimental analogue of the conservation of liquid quantity task, the child was presented with a choice stimulus requiring a left- or right-hand button press. The proportion of correct responses discriminated successfully between conservers and nonconservers as established by traditional Piagetian assessment procedures. The ERPs obtained in the experimental analogue of the conservation task were characterized by a broad positivity with a centroparietal scalp distribution. The broad positivity discriminated significantly between nonconservers and conservers but not between age groups. These findings received additional support from topographic and symmetric dipole analyses of the ERPs. The results of the dipole analysis suggested more anterior ERP sources for the nonconservers during the early part of stimulus analysis and more lateralized ERP sources for conservers during the later part of information processing. It is concluded that ERPs may provide a window on the relation between brain maturation and stage-wise cognitive development.

Effects of degradation of visual stimuli on components of the event-related potential (ERP) in go/nogo reaction tasks

In the present experiments, event-related potentials (ERPs) were measured to randomly presented letters, requiring either a right-hand button-press response (go), or requiring no response (nogo). In both go and nogo conditions, the letters could be intact or degraded. ERPs time-locked with voluntary right hand button-presses were measured in a separate condition. Nogo stimuli elicited larger negative components (N400, N480) at the frontal electrode sites, and larger late-positive components (P600, P640) at the central electrode sites, than go stimuli. Additionally, intact stimuli elicited larger late-positive components and smaller Slow Wave (SW) components then degraded stimuli, but these amplitude-differences were seen more clearly in the nogo than in the go conditions. These results are discussed in relation to cognitive and motor aspects of go and nogo stimuli, and the possibility of contamination of ERP components with movement-related potentials.