Primary Sensorimotor Areas Research Articles

Correlations in spontaneous activity and gray matter density between left and right sensoritmotor areas of pianists

Resting-state functional MRI and structural MRI were used to study correlations of spontaneous activity and gray matter density between the left and right primary sensorimotor areas in pianists and nonmusicians. Functional MRI analysis showed significant correlation of spontaneous activity between the left and right primary sensorimotor area in both groups; however, there was no between-group difference. Structural MRI analysis showed significant correlation in gray matter density between the left and right sensorimotor areas in nonmusicians (r=0.65, P=0.001), but not in pianists (r=0.07, P=0.78), with a significant between-group difference (P=0.035). The lack of correlation of gray matter density between the left and right sensorimotor areas might be the basis of bimanual coordination of the pianists.

Golf putt outcomes are predicted by sensorimotor cerebral EEG rhythms

It is not known whether frontal cerebral rhythms of the two hemispheres are implicated in fine motor control and balance. To address this issue, electroencephalographic (EEG) and stabilometric recordings were simultaneously performed in 12 right-handed expert golfers. The subjects were asked to stand upright on a stabilometric force platform placed at a golf green simulator while playing about 100 golf putts. Balance during the putts was indexed by body sway area. Cortical activity was indexed by the power reduction in spatially enhanced alpha (8-12 Hz) and beta (13-30 Hz) rhythms during movement, referred to as the pre-movement period. It was found that the body sway area displayed similar values in the successful and unsuccessful putts. In contrast, the high-frequency alpha power (about 10-12 Hz) was smaller in amplitude in the successful than in the unsuccessful putts over the frontal midline and the arm and hand region of the right primary sensorimotor area; the stronger the reduction of the alpha power, the smaller the error of the unsuccessful putts (i.e. distance from the hole). These results indicate that high-frequency alpha rhythms over associative, premotor and non-dominant primary sensorimotor areas subserve motor control and are predictive of the golfer's performance.

Structural abnormalities in the cerebellum and sensorimotor circuit in writer's cramp

Structural abnormalities were detected in bilateral primary sensorimotor areas in writer's cramp. Evidence in other primary dystonia, including blepharospasm and cervical dystonia, suggest that structural abnormalities may be observed in other brain areas such as the cerebellum in writer's cramp. To test the hypothesis that structural abnormalities are present along the sensorimotor and cerebellar circuits in patients with writer's cramp. Using voxel-based morphometry, the authors compared the brain structure of 30 right-handed patients with writer's cramp with that of 30 healthy control subjects matched for gender, age, and handedness. Gray matter decrease was found in the hand area of the left primary sensorimotor cortex, bilateral thalamus, and cerebellum (height threshold p < 0.01, cluster significant at p < 0.05 corrected for multiple comparisons). These results demonstrate in writer's cramp the presence of structural abnormalities in brain structures interconnected within the sensorimotor network including the cerebellum and the cortical representation of the affected hand. These abnormalities may be related to the pathophysiology of writer's cramp, questioning the role of the cerebellum, or to maladaptive plasticity in a task-related dystonia.

Mutual‐information‐based approach for neural connectivity during self‐paced finger lifting task

Frequency-dependent modulation between neuronal assemblies may provide insightful mechanisms of functional organization in the context of neural connectivity. We present a conjoined time-frequency cross mutual information (TFCMI) method to explore the subtle brain neural connectivity by magnetoencephalography (MEG) during a self-paced finger lifting task. Surface electromyogram (sEMG) was obtained from the extensor digitorum communis. Both within-modality (MEG-MEG) and between-modality studies (sEMG-MEG) were conducted. The TFCMI method measures both the linear and nonlinear dependencies of the temporal dynamics of signal power within a pre-specified frequency band. Each single trial of MEG across channels and sEMG signals was transformed into time-frequency domain with use of the Morlet wavelet to obtain better temporal spectral (power) information. As compared to coherence approach (linear dependency only) in broadband analysis, the TFCMI method demonstrated advantages in encompassing detection for the mesial frontocentral cortex and bilateral primary sensorimotor areas, clear demarcation of event- and non-event-related regions, and robustness for sEMG - MEG between-modality study, i.e., corticomuscular communication. We conclude that this novel TFCMI method promises a possibility to better unravel the intricate functional organizations of brain in the context of oscillation-coded communication.

Overt and imagined singing of an Italian aria

Activation maps of 16 professional classical singers were evaluated during overt singing and imagined singing of an Italian aria utilizing a sparse sampling functional magnetic imaging (fMRI) technique. Overt singing involved bilateral primary and secondary sensorimotor and auditory cortices but also areas associated with speech and language production. Activation magnitude within the gyri of Heschl (A1) was comparable in both hemispheres. Subcortical motor areas (cerebellum, thalamus, medulla and basal ganglia) were active too. Areas associated with emotional processing showed slight (anterior cingulate cortex, anterior insula) activation. Cerebral activation sites during imagined singing were centered on fronto-parietal areas and involved primary and secondary sensorimotor areas in both hemispheres. Areas processing emotions showed intense activation (ACC and bilateral insula, hippocampus and anterior temporal poles, bilateral amygdala). Imagery showed no significant activation in A1. Overt minus imagined singing revealed increased activation in cortical (bilateral primary motor; M1) and subcortical (right cerebellar hemisphere, medulla) motor as well as in sensory areas (primary somatosensory cortex, bilateral A1). Imagined minus overt singing showed enhanced activity in the medial Brodmann's area 6, the ventrolateral and medial prefrontal cortex (PFC), the anterior cingulate cortex and the inferior parietal lobe. Additionally, Wernicke's area and Brocca's area and their homologues were increasingly active during imagery. We conclude that imagined and overt singing involves partly different brain systems in professional singers with more prefrontal and limbic activation and a larger network of higher order associative functions during imagery.

Hand sensory–motor cortical network assessed by functional source separation

The functional source separation procedure (FSS) was applied to identify the activities of the primary sensorimotor areas (SM1) devoted to hand control. FSS adds a functional constraint to the cost function of the basic independent component analysis, and obtains source activity all along different processing states. Magnetoencephalographic signals from the left SM1 were recorded in 14 healthy subjects during a simple sensorimotor paradigm--galvanic right median nerve stimuli intermingled with submaximal isometric thumb opposition. Two functional sources related to the sensory flow in the primary cortex were extracted requiring maximal responsiveness to the nerve stimulation at around 20 and 30 ms (S1a, S1b). Maximal cortico-muscular coherence was required for the extraction of the motor source (M1). Sources were multiplied by the Euclidean norm of their corresponding weight vectors, allowing amplitude comparisons among sources in a fixed position. In all subjects, S1a, S1b, M1 were successfully obtained, positioned consistently with the SM1 organization, and behaved as physiologically expected during the movement and processing of the sensory stimuli. The M1 source reacted to the nerve stimulation with higher intensity at latencies around 30 ms than around 20 ms. The FSS method was demonstrated to be able to obtain the dynamics of different primary cortical network activities, two devoted mainly to sensory inflow, and the other to the motor control of the contralateral hand. It was possible to observe each source both during pure sensory processing and during motor tasks. In all conditions, a direct comparison of source intensities can be achieved.

Tracking Alzheimer's disease.

Population-based brain mapping provides great insight into the trajectory of aging and dementia, as well as brain changes that normally occur over the human life span. We describe three novel brain mapping techniques, cortical thickness mapping, tensor-based morphometry (TBM), and hippocampal surface modeling, which offer enormous power for measuring disease progression in drug trials, and shed light on the neuroscience of brain degeneration in Alzheimer's disease (AD) and mild cognitive impairment (MCI). We report the first time-lapse maps of cortical atrophy spreading dynamically in the living brain, based on averaging data from populations of subjects with Alzheimer's disease and normal subjects imaged longitudinally with MRI. These dynamic sequences show a rapidly advancing wave of cortical atrophy sweeping from limbic and temporal cortices into higher-order association and ultimately primary sensorimotor areas, in a pattern that correlates with cognitive decline. A complementary technique, TBM, reveals the 3D profile of atrophic rates, at each point in the brain. A third technique, hippocampal surface modeling, plots the profile of shape alterations across the hippocampal surface. The three techniques provide moderate to highly automated analyses of images, have been validated on hundreds of scans, and are sensitive to clinically relevant changes in individual patients and groups undergoing different drug treatments. We compare time-lapse maps of AD, MCI, and other dementias, correlate these changes with cognition, and relate them to similar time-lapse maps of childhood development, schizophrenia, and HIV-associated brain degeneration. Strengths and weaknesses of these different imaging measures for basic neuroscience and drug trials are discussed.

Lower Limb Sensorimotor Network: Issues of Somatotopy and Overlap

Functional magnetic resonance imaging (fMRI) was used 1) to describe the pattern of whole brain activity during motion of isolated joints of the lower limb, 2) to examine the somatotopic organization of lower limb joint representations in the primary sensorimotor cortex and the anterior lobe of the cerebellum and 3) to quantify the degree of overlap between these lower limb joint activations. Eighteen healthy, right leg dominant volunteers participated in a motor block-design study, performing repetitive knee, ankle and toes flexion/extension movements. In order to relate lower limb joints activation to the well-described patterns of finger movement, serial finger-to-thumb opposition was also assessed. All movements were auditory paced at 72 beats/min (1.2 Hz). Isolated lower limb joints movement activated a distributed sensorimotor network, including primary and non-primary sensorimotor areas. Although a large overlap was evident in primary sensorimotor cortex (SM1) and cerebellum representations of the three lower limb joints, a somatotopic arrangement was recognizable with reference to center of mass coordinates of each individual joint in the above areas. Detection of active brain regions during movement of the lower limb joints is feasible with fMRI although a carefully optimized methodology protocol is required.

Closed-lip Schizencephaly Around the Central Sulcus With Intractable Epilepsy Treated by Peri-lesional Focus Resection -Case Report-

A 24-year-old man presented with closed-lip schizencephaly around the right central sulcus manifesting as an 11-year history of intractable epilepsy. Mild motor paresis in the left extremities and mental retardation were observed. Tonic posture with bilateral facial tonic contraction was asymmetrical, predominantly in the left extremities. Magnetic resonance imaging demonstrated closed-lip schizencephaly around the right central sulcus. The epileptogenic zone was determined in the supplementary motor area, and premotor and primary sensorimotor cortices using invasive recordings. As the thickened cortex was considered functional, corticectomy of the supplementary motor area and premotor area was performed, preserving the primary sensorimotor area. Histological examination revealed marked cortico-subcortical gliosis, particularly in the medial part of the resection. Asymmetrical tonic postural seizure disappeared completely after surgery. Medically intractable epilepsy with schizencephaly represents a considerable challenge in epilepsy surgery. Partial corticectomy adjacent to the thickened cortex was effective for seizure control in a patient with closed-lip schizencephaly around the central sulcus.

Functional brain mapping of actual car-driving using [18F]FDG-PET

This study aims at identifying the brain activation during actual car-driving on the road, and at comparing the results to those of previous studies on simulated car-driving. Thirty normal volunteers, aged 20 to 56 years, were divided into three subgroups, active driving, passive driving and control groups, for examination by positron emission tomography (PET) and [18F]2-deoxy-2-fluoro-D-glucose (FDG). The active driving subjects (n = 10) drove for 30 minutes on quiet normal roads with a few traffic signals. The passive driving subjects (n = 10) participated as passengers on the front seat. The control subjects (n = 10) remained seated in a lit room with their eyes open. Voxel-based t-statistics were applied using SPM2 to search brain activation among the subgroups mentioned above. Significant brain activation was detected during active driving in the primary and secondary visual cortices, primary sensorimotor areas, premotor area, parietal association area, cingulate gyrus, the parahippocampal gyrus as well as in thalamus and cerebellum. The passive driving manifested a similar-looking activation pattern, lacking activations in the premotor area, cingulate and parahippocampal gyri and thalamus. Direct comparison of the active and passive driving conditions revealed activation in the cerebellum. The result of actual driving looked similar to that of simulated driving, suggesting that visual perception and visuomotor coordination were the main brain functions while driving. In terms of attention and autonomic arousal, however, it seems there was a significant difference between simulated and actual driving possibly due to risk of accidents. Autonomic and emotional aspects of driving should be studied using an actual driving study-design.

Rhythmic brain activities related to singing in humans

To investigate the motor control related to sound production, we studied cortical rhythmic changes during continuous vocalization such as singing. Magnetoencephalographic (MEG) responses were recorded while subjects spoke in the usual way (speaking), sang (singing), hummed (humming) and imagined (imagining) a popular song. The power of alpha (8–15 Hz), beta (15–30 Hz) and low-gamma (30–60 Hz) frequency bands was changed during and after vocalization (singing, speaking and humming). In the alpha band, the oscillatory changes for singing were most pronounced in the right premotor, bilateral sensorimotor, right secondary somatosensory and bilateral superior parietal areas. The beta oscillation for the singing was also confirmed in the premotor, primary and secondary sensorimotor and superior parietal areas in the left and right hemispheres where were partly activated even for imagined a song (imaging). These regions have been traditionally described as vocalization-related sites. The cortical rhythmic changes were distinct in the singing condition compared with the other vocalizing conditions (speaking and humming) and thus we considered that more concentrated control of the vocal tract, diaphragm and abdominal muscles is responsible. Furthermore, characteristic oscillation in the high-gamma (60–200 Hz) frequency band was found in Broca’s area only in the imaging condition and might occur singing rehearsal and storage process in Broca’s area.

The relationship between motor deficit and hemisphere activation balance after stroke: A 3T fMRI study

Functional imaging during movement of the hand affected by a stroke has shown excess activation of the contralesional motor network, implying less physiological hemisphere activation balance. Although this may be adaptive, the relationship between the severity of motor deficit and the hemisphere activation balance for the four major cortical motor areas has not been systematically studied. We prospectively studied 19 right-handed patients with first-ever stroke (age range 61 ± 10 years) in the stable phase of recovery (> 3 months after onset), using auditory-paced index–thumb (IT) tapping of the affected hand at 1.25 Hz as the fMRI paradigm. The hemisphere activation balance for the primary motor (M1), primary somatosensory (S1), supplementary motor (SMA) and dorsal premotor (PMd) areas was measured by a modified weighted laterality index (wLI), and correlations with motor performance (assessed by the affected/unaffected ratio of maximum IT taps in 15 s, termed IT-R) were computed. There were statistically significant negative correlations between IT-R and the wLI for M1 and S1, such that the more the hemispheric balance shifted contralesionally, the worse the performance. Furthermore, worse performance was related to a greater amount of contralesional, but not ipsilesional, activation. No significant correlation between IT-R and the wLI was obtained for the SMA and PMd, which functionally have stronger bilateral organization. These findings suggest that the degree of recovery of fine finger motion after stroke is determined by the extent to which activation balance in the primary sensory motor areas – where most corticospinal fibers originate – departs from normality. This observation may have implications for therapy.

3D pattern of brain atrophy in HIV/AIDS visualized using tensor-based morphometry

35% of HIV-infected patients have cognitive impairment, but the profile of HIV-induced brain damage is still not well understood. Here we used tensor-based morphometry (TBM) to visualize brain deficits and clinical/anatomical correlations in HIV/AIDS. To perform TBM, we developed a new MRI-based analysis technique that uses fluid image warping, and a new α-entropy-based information-theoretic measure of image correspondence, called the Jensen–Rényi divergence (JRD). Methods 3D T1-weighted brain MRIs of 26 AIDS patients (CDC stage C and/or 3 without HIV-associated dementia; 47.2 ± 9.8 years; 25M/1F; CD4 + T-cell count: 299.5 ± 175.7/μl; log 10 plasma viral load: 2.57 ± 1.28 RNA copies/ml) and 14 HIV-seronegative controls (37.6 ± 12.2 years; 8M/6F) were fluidly registered by applying forces throughout each deforming image to maximize the JRD between it and a target image (from a control subject). The 3D fluid registration was regularized using the linearized Cauchy–Navier operator. Fine-scale volumetric differences between diagnostic groups were mapped. Regions were identified where brain atrophy correlated with clinical measures. Results Severe atrophy (∼ 15–20% deficit) was detected bilaterally in the primary and association sensorimotor areas. Atrophy of these regions, particularly in the white matter, correlated with cognitive impairment ( P = 0.033) and CD4 + T-lymphocyte depletion ( P = 0.005). Conclusion TBM facilitates 3D visualization of AIDS neuropathology in living patients scanned with MRI. Severe atrophy in frontoparietal and striatal areas may underlie early cognitive dysfunction in AIDS patients, and may signal the imminent onset of AIDS dementia complex.

Electro-encephalogram based brain–computer interface: improved performance by mental practice and concentration skills

Mental imagination is the essential part of the most EEG-based communication systems. Thus, the quality of mental rehearsal, the degree of imagined effort, and mind controllability should have a major effect on the performance of electro-encephalogram (EEG) based brain-computer interface (BCI). It is now well established that mental practice using motor imagery improves motor skills. The effects of mental practice on motor skill learning are the result of practice on central motor programming. According to this view, it seems logical that mental practice should modify the neuronal activity in the primary sensorimotor areas and consequently change the performance of EEG-based BCI. For developing a practical BCI system, recognizing the resting state with eyes opened and the imagined voluntary movement is important. For this purpose, the mind should be able to focus on a single goal for a period of time, without deviation to another context. In this work, we are going to examine the role of mental practice and concentration skills on the EEG control during imaginative hand movements. The results show that the mental practice and concentration can generally improve the classification accuracy of the EEG patterns. It is found that mental training has a significant effect on the classification accuracy over the primary motor cortex and frontal area.

Negative myoclonus. An overview of its clinical features, pathophysiological mechanisms, and management

Negative myoclonus (NM) is an unspecific motor disorder that can characterize a variety of neurological conditions. From the clinical point of view, NM appears as a shock-like involuntary jerky movement caused by a sudden, brief interruption of muscle activity. Asterixis is a type of NM that occurs typically in toxic-metabolic encephalopathies. NM of epileptic nature, or epileptic negative myoclonus (ENM), is defined as an interruption of tonic muscle activity, which is time-locked to an epileptic EEG abnormality, without evidence of an antecedent positive myoclonia in the agonist–antagonist muscles. ENM can be observed in idiopathic, cryptogenic, and symptomatic epileptic disorders. Pathophysiological hypotheses on the origin of NM involve subcortical as well as cortical mechanisms. Recent neuroimaging and neurophysiologic investigations, including intracerebral recordings and electrical stimulation procedures in epileptic patients, suggest the participation of premotor, primary motor, primary sensory, and supplementary motor areas in the genesis of NM. Polygraphic monitoring is essential for the diagnosis of NM, allowing the demonstration of brief interruptions of a tonic EMG activity, not preceded by a positive myoclonus in the agonist and antagonist muscles of the affected limb. Simultaneous EEG-EMG monitoring demonstrating the association of NM with an epileptic potential is consistent with the diagnosis of ENM. Evolution and prognosis of NM is mainly related to aetiology. In childhood idiopathic partial epilepsy, ENM can respond to some drugs (in particular, ethosuximide), whereas other medications (such as carbamazepine or phenytoin) have been reported to induce or worsen it.

Effects of surface EMG rectification on power and coherence analyses: An EEG and MEG study

Coherence between electromyography (EMG) and electroencephalography (EEG) or magnetoencephalography (MEG) is frequently examined to gain insights on neuromuscular binding. Commonly, EMG signals are rectified before coherence is computed. However, the appropriateness of EMG rectification in computing EMG–EEG/MEG coherence has never been validated. Since rectification is a non-linear operation and alters the EMG power spectrum, such a validation is important to ensure the accuracy of coherence calculation. In this study we experimentally investigated the effects of EMG rectification on EMG power spectra and its coherence with EEG/MEG signals. Subjects performed sustained isometric index finger abduction at ∼5–10% maximal voluntary force (in both EEG–EMG and MEG–EMG experiments) and index finger tapping at ∼2–4 Hz (in EEG–EMG experiment only). Bipolar surface EMG data from the first dorsal interosseus (FDI) and EEG/MEG signals from the contralateral primary sensorimotor area (C3) were recorded simultaneously. Power spectra and coherence with the EEG/MEG were calculated before and after EMG rectification. The results show that rectification shifts EMG power to lower frequencies, possibly enhancing peaks of motor unit firing. Coherences with the EEG/MEG signals were not significantly changed by EMG rectification, indicating EMG rectification is overall an appropriate procedure in power and coherence analyses.

Relationship between intracerebral gamma oscillations and slow potentials in the human sensorimotor cortex

Changes in sensorimotor rhythms (mu, beta and gamma) and movement-related cortical potentials (MRCPs) are both generated principally by the contralateral sensorimotor areas during the execution of self-paced movement. They appear to reflect movement control mechanisms, which remain partially unclear. With the aim of better understanding their sources and significance, we recorded MRCPs and sensorimotor rhythms during and after self-paced movement using intracerebral electrodes in eight epileptic subjects investigated by stereoelectroencephalography. The results showed that: (i) there is a strong spatial relationship between the late components of movement--the so-called motor potential (MP) and post-movement complex (PMc)--and gamma event-related synchronization (ERS) within the 40-60 Hz band, as the MP/PMc always occurred in contacts displaying gamma ERS (the primary sensorimotor areas), whereas mu and beta reactivities were more diffuse; and (ii) MPs and PMc are both generated by the primary motor and somatosensory areas, but with distinct sources. Hence, this could mean that kinesthesic sensory afferences project to neurons other than those firing during the pyramidal tract volley. The PMc and low gamma ERS represent two electrophysiological facets of kinesthesic feedback from the joints and muscles involved in the movement to the sensorimotor cortex. It could be suggested that gamma oscillations within the 40-60 Hz band could serve to synchronize the activities of the various neuronal populations involved in control of the ongoing movement.

Quantitative measure of complexity of the dynamic event-related EEG data

Currently, the quantification of event-related EEG is usually based on power feature with the classical band power method. In this paper, the method quantifying the complexity and irregularity of event-related EEG data in relation to hand motor imagery is presented. Two groups of the complexity indexes: Kolmogorov complexity ( Kc) and Fourier spectral entropy ( FSE) are discussed. The event-related desynchronization/synchronization (ERD/ERS) time course is analyzed and characterized by two parameters Kc and FSE, respectively. The percentage of EEG complexity during imagination of the unilateral hand movement relative to that during reference period is calculated for quantifying the complexity measure of ERD/ERS time course. The method is applied to two sets of movement-related EEG data recorded over the primary sensorimotor area from two subjects. In addition, the validity of the quantitative measure of complexity of the event-related EEG is testified by evaluating the performance of feature extraction and classification. The results show that both Kc and FSE can effectively describe the dynamic complexity of event-related EEG and also display the consistent and similar behaviors. The relative increase and decrease of event-related EEG complexity could be an indicator of ERD/ERS, which is also independent of the power changes. Thus, the dynamic complexity measure of event-related EEG quantified by Kc and FSE provides another evidence for ERD/ERS and can be meaningful for analyzing the event-related EEG.

How a Lateralized Brain Supports Symmetrical Bimanual Tasks

A large repertoire of natural object manipulation tasks require precisely coupled symmetrical opposing forces by both hands on a single object. We asked how the lateralized brain handles this basic problem of spatial and temporal coordination. We show that the brain consistently appoints one of the hands as prime actor while the other assists, but the choice of acting hand is flexible. When study participants control a cursor by manipulating a tool held freely between the hands, the left hand becomes prime actor if the cursor moves directionally with the left-hand forces, whereas the right hand primarily acts if it moves with the opposing right-hand forces. In neurophysiological (electromyography, transcranial magnetic brain stimulation) and functional magnetic resonance brain imaging experiments we demonstrate that changes in hand assignment parallels a midline shift of lateralized activity in distal hand muscles, corticospinal pathways, and primary sensorimotor and cerebellar cortical areas. We conclude that the two hands can readily exchange roles as dominant actor in bimanual tasks. Spatial relationships between hand forces and goal motions determine hand assignments rather than habitual handedness. Finally, flexible role assignment of the hands is manifest at multiple levels of the motor system, from cortical regions all the way down to particular muscles.

A cluster-based quantitative procedure in an fMRI study of Parkinson's disease

Parkinson's disease is a neurological disorder associated with disfunction of dopaminergic pathways of the basal ganglia. In this study, we report the effects of decreasing plasma concentrations of the dopamine-agonist apomorphine on the size and extents of activity clusters observed with functional magnetic resonance imaging during a simple motor task. Eight patients at advanced disease stage and six healthy volunteers were studied during four consecutive sessions. We observed consistent activations in the primary sensorimotor area of the contralateral side and in the supplementary motor area of both patients and controls during the first session. During subsequent sessions, while the drug concentration gradually decreased in patients, they showed a fragmentation of the activity areas, with an overall decrease of involved volume and a decline of activity in the supplementary motor area. The appearing of activity in the ipsilateral motor area matched a partial recovery of supplementary motor area activation. During the last session, when patients showed severe dyskinesia, a widespread region of positive and negative correlations between signal and task was observed. We conclude that the lack of subcortical circuitry is partially reversible by apomorphine and that when the drug effects are reduced, there is a possible mechanism recruitment of alternate subcortical pathways.