Contralateral Body Parts Research Articles

Distinct representation of ipsilateral hand movements in sensorimotor areas

There is ample evidence that the contralateral sensorimotor areas play an important role in movement generation, with the primary motor cortex and the primary somatosensory cortex showing a detailed spatial organization of the representation of contralateral body parts. Interestingly, there are also indications for a role of the motor cortex in controlling the ipsilateral side of the body. However, the precise function of ipsilateral sensorimotor cortex in unilateral movement control is still unclear. Here, we show hand movement representation in the ipsilateral sensorimotor hand area, in which hand gestures can be distinguished from each other and from contralateral hand gestures. High‐field functional magnetic resonance imaging (fMRI) data acquired during the execution of six left‐ and six right‐hand gestures by healthy volunteers showed ipsilateral activation mainly in the anterior section of precentral gyrus and the posterior section of the postcentral gyrus. Despite the lower activation in ipsilateral areas closer to the central sulcus, activity patterns for the 12 hand gestures could be mutually distinguished in these areas. The existence of a unique representation of ipsilateral hand movements in the human sensorimotor cortex favours the notion of transcallosal integrative processes that support optimal coordination of hand movements.

Hemispheric asymmetries in the processing of body sides: A study with ambiguous human silhouettes

When required to indicate the perceived orientation of pictures of human silhouettes with ambiguous front/back orientation and handedness, both right- and left-handed participants perceive the figures more frequently as right-handed than as left-handed, which seems to indicate an attentional bias towards the right arm of human bodies. Given that past research exploiting the divided visual field paradigm indicated a processing advantage for contralateral body parts in both hemispheres, we tested whether human silhouettes with ambiguous handedness presented in the right visual field would be interpreted more frequently as right-handed compared with those presented in the left visual field. We confirmed the expected lateralised embodiment of ambiguous human bodies, in line with previous studies showing that right and left limbs are processed faster and/or more accurately when presented in the right and left hemifield, respectively.

Positive and Negative Somatotopic BOLD Responses in Contralateral Versus Ipsilateral Penfield Homunculus.

One of the basic properties of sensory cortices is their topographical organization. Most imaging studies explored this organization using the positive blood oxygenation level-dependent (BOLD) signal. Here, we studied the topographical organization of both positive and negative BOLD in contralateral and ipsilateral primary somatosensory cortex (S1). Using phase-locking mapping methods, we verified the topographical organization of contralateral S1, and further showed that different body segments elicit pronounced negative BOLD responses in both hemispheres. In the contralateral hemisphere, we found a sharpening mechanism in which stimulation of a given body segment triggered a gradient of activation with a significant deactivation in more remote areas. In the ipsilateral cortex, deactivation was not only located in the homolog area of the stimulated parts but rather was widespread across many parts of S1. Additionally, analysis of resting-state functional magnetic resonance imaging signal showed a gradient of connectivity to the neighboring contralateral body parts as well as to the ipsilateral homologous area for each body part. Taken together, our results indicate a complex pattern of baseline and activity-dependent responses in the contralateral and ipsilateral sides. Both primary sensory areas were characterized by unique negative BOLD responses, suggesting that they are an important component in topographic organization of sensory cortices.

Motor versus body awareness: Voxel-based lesion analysis in anosognosia for hemiplegia and somatoparaphrenia following right hemisphere stroke

Anosognosia for hemiplegia (AHP) is informative about the neurocognitive basis of motor awareness. However, it is frequently associated with concomitant symptoms, such as hemispatial neglect and disturbances in the sense of body ownership (DSO). Although double dissociations between these symptoms have been reported, there is ongoing debate about whether they are manifestations of independent abnormalities, or a single neurocognitive deficit. We aimed to investigate the specificity of lesions associated with AHP by surpassing four, existing methodological limitations: (a) recruit a relatively large sample of patients (total N = 70) in a multi-centre study; (b) identify lesions associated with AHP in grey and white matter using voxel-based methods; (c) take into account the duration of AHP and concomitant neglect symptoms; and (d) compare lesions against a control hemiplegic group, patients suffering from AHP and DSO, and a few, rare patients with selective DSO. Results indicated that acute AHP is associated with a wide network, mainly including: (1) the Rolandic operculum, (2) the insula and (3) the superior temporal gyri. Subcortically, damage mainly involved the basal ganglia and white matter, mostly the superior corona radiate, arcuate fasciculus and the part of the ventral, superior longitudinal fasciculus. Persistent symptoms were linked with wider damage involving fronto-temporal cortex and long white matter tracts. A shift in the latero-medial direction (mainly involving the basal ganglia and surrounding white matter) emerged when DSO was taken accounted for. These results suggest that while bodily awareness is processed by areas widely distributed across the brain, intact subcortical structures and white matter tracts may be necessary to support basic feelings of owning and controlling contralateral body parts. An accurate and ‘up-to-date’ awareness of our motor abilities, however, may rely also on intact processing in cortical areas which presumably allow higher-order inferences about the current state of the body.

Cell and neuron densities in the primary motor cortex of primates

Cell and neuron densities vary across the cortical sheet in a predictable manner across different primate species (Collins et al., 2010b). Primary motor cortex, M1, is characterized by lower neuron densities relative to other cortical areas. M1 contains a motor representation map of contralateral body parts from tail to tongue in a mediolateral sequence. Different functional movement representations within M1 likely require specialized microcircuitry for control of different body parts, and these differences in circuitry may be reflected by variation in cell and neuron densities. Here we determined cell and neuron densities for multiple sub-regions of M1 in six primate species, using the semi-automated flow fractionator method. The results verify previous reports of lower overall neuron densities in M1 compared to other parts of cortex in the six primate species examined. The most lateral regions of M1 that correspond to face and hand movement representations, are more neuron dense relative to medial locations in M1, which suggests differences in cortical circuitry within movement zones.

SU‐FF‐I‐42: Making Hanging Protocols Work in a Clinical Setting

Purpose: The radiologists at our institution prefer to read bone surveys in a specific order. The specific order allows them to read studies more quickly, and easily perform comparisons between contralateral body parts (e.g. right and left humerus). However, we have four generations of DR equipment from a particular manufacturer, and the DICOM header information for DX objects is inconsistent amongst the systems. Therefore, a hanging protocol was developed to facilitate the hanging of bone survey images in the proper order. Materials and methods: Our PACS system (iSite, Stentor) allows the use of hanging protocols. These protocols use matching series rules to establish hanging orders. Matching series rules were used where DICOM header information was present (i.e. not in a hidden/private field) and consistent. Also, technologists were provided with a schematic detailing the order in which specific images had to be acquired to result in the correct hanging order where matching series rules could not be used. Results: A successful hanging protocol was created using a combination of PACS tools and technologist instruction. The resulting protocol maximized patient comfort, minimized patient movement between table and wall detectors, and was simple enough to ensure a high rate of compliance from technologists. In addition, we provided tools to technologists and supervisors to view their studies in the order it would hang when opened for reading, and to correct studies (via presentation states) where patient safety or comfort required an exception to be made or where a mistake was made by the technologist. Hanging protocols for CR objects were also created. Conclusions: Creation of useful hanging protocols is still possible even when limitations are presented by DICOM header structure and content.

Global activation of primary motor cortex during voluntary movements in humans

Objective: The primary motor cortex (M1) forms the executive part in the functional hierarchy of the motor system and is characterized by a somatotopic organization of body representations. While it is known that M1 efferent activity leads to movement execution in contralateral body parts, it appears that motor control is achieved by distributed processing of multimodal inputs and motor commands. In this study we wanted to assess functional implications of the distributed character of the human motor system with particular respect to the primary motor areas.

Contralateral coding of imagined body parts in the superior parietal lobe.

In monkeys, neurons in the superior parietal lobe (area 5) code for spatial position of contralateral body parts by combining visual and somatosensory signals. Using a modified version of the classical mental rotation task, we were able to demonstrate that in humans activation in the contralateral superior parietal lobe could be evoked when mental rotation was combined with motor imagery of hands. These findings show that even in the absence of visual and somatosensory input, information provided by motor imagery suffices to induce contralateral superior parietal lobe monitoring of the imagined limb configuration. This constitutes an important prerequisite for effective imagined motor practice that can be used to improve actual motor performance.

Spatial hemineglect in humans

The term `spatial hemineglect' refers collectively to disorders of spatial cognition, which concern specific sectors of space with reference to a given coordinate system. Patients with cerebral lesions involving the posterior-inferior parietal and the premotor cortex, most often in the right hemisphere, sometimes fail to explore the extra-personal and personal sectors of space contralateral to the side of the lesion, are not aware of stimuli presented in these portions of space, or of contralateral body parts and their disordered function. In addition to these negative signs patients may also show positive pathological manifestations, such as avoidance or withdrawal from the contralateral side of space, and delusional views concerning contralateral body parts. The many varieties of this disorder can occur in dissociated forms, suggesting a multifaceted organization of the internal representation of space, of spatial attention, and of their neural correlates. Many manifestations of hemineglect are modulated in a similar fashion by specific sensory stimulation that also affects visuo-motor processes in normal subjects. This ongoing sensory modulation might update the internal representations of space in a continuously changing environment, and contribute to the formation, around the vertical orientation of gravity, of our subjective unitary experience of space.

The primate subthalamic nucleus. I. Functional properties in intact animals

1. The present study tests several key aspects of the current model of the intrinsic circuitry of the basal ganglia, in particular the degree to which basal ganglia-thalamocortical circuits are functionally segregated at the level of the subthalamic nucleus (STN). To this end the responses of STN cells to somatosensory examination (n = 301 cells), the polarity and latencies of neuronal responses to passive and active movements (n = 223 cells), responses to microstimulation (n = 1589 sites), and cross-correlation functions of pairs of neighboring neurons (n = 72 pairs) were studied in STNs of three African green monkeys. 2. The activity of 55% of cells examined in STN was briskly modulated in response to passive movements of individual contralateral body parts. Of these, 86% responded to passive joint rotation of muscle palpation, but in some cases (25% of responding cells) responses were also elicited by light touch. In 91% of the responding cells responses were elicited by manipulations around a single joint only. 3. The caudoventral sector in STN was largely devoid of cells with responses to somatosensory stimulation. Within the rostrodorsal zone a lateral region containing neurons that responded to arm movements and a more medial region with neurons responding to leg movement were found. Cells responding to orofacial movements were located more dorsally and rostrally. Neurons with similar responses to active and passive movements of the limbs tended to be clustered within "arm" and "leg" zones. 4. Of identified arm cells in STN (n = 80), 36% responded to the application of torque pulses to the elbow (43 responses overall). Forty-eight percent of these cells responded to both extension and flexion torques. Ninety-three percent of the responses were initial increases in discharge, which characteristically occurred earlier and were shorter than initial decreases. Fifty-three percent of the responses were biphasic or multiphasic. 5. During active step tracking movements 40% of STN arm cells (n = 53 cells) responded with significant changes in activity. Thirty-six percent of these cells showed responses with both extension and flexion movements. Of the responses, 90% were increases in discharge. Only 14% of all responses were biphasic or multiphasic. Responses tended to occur around the time of movement onset (average latency 2 ms after movement onset). 6. Microstimulation (bipolar pulses, 40 microA, 200-500 ms train duration, 400 Hz) of the core of STN itself did not appear to produce movement.4+ synchronized activity in only 11% of pairs.(ABSTRACT TRUNCATED AT 400 WORDS)

Motor and sensory cortex in humans: topography studied with chronic subdural stimulation.

Classic neurosurgical teaching holds that once the Rolandic fissure (Rf) has been located, there are distinct differentiated primary motor and sensory functional units confined within a narrow cortical strip: Brodmann's Areas 4 and 6 for primary motor units in front of the Rf and 3, 1, and 2 for sensory units behind the Rf. To test this assumption, we examined in detail the records of cortical mapping done by electrical stimulation of the cerebral cortex via implanted subdural electrode grids in 35 patients with seizure disorders. Of 1381 stimulations of the electrode sites, 346 (25.1%) produced primary motor or motor-arrest and sensory responses in contralateral body parts: 56.8% were primary motor responses; 16.2% were motor-arrest; 22.5% were sensory; and the remaining 4.5% were mixed motor and sensory responses. Two-thirds (65.9%) of the primary motor responses were located within 10 mm of the Rf, and the remaining one-third (34.1%) were more than 10 mm anterior to the Rf or were posterior to the Rf. Furthermore, in the patient group with brain lesions, fewer than one-third (28.1%) of the responses were within the 10-mm narrow anterior strip. Our study reconfirmed that a significant number--at least one-third--of motor responses are distributed outside the classic narrow cortical strip. In patients with brain lesions, the motor representation is further displaced outside the narrow strip. This finding indicates that primary motor cortex may extend beyond the gyrus immediately anterior to the Rf.

Further physiological observations on the ventralis intermedius neurons in the human thalamus.

1. During the course of stereotaxic thalamotomy for 56 cases with tremor mainly due to Parkinson's disease and essential tremor, extracellular recordings were made from the thalamic ventralis intermedius (Vim) nucleus under local anesthesia. These procedures have been justified as an essential technique to achieve the best therapeutic results by a selective coagulation. These physiological observations provide important information about the functional organization of the ventrolateral thalamic mass in humans. 2. Using Leksell's stereotaxic apparatus, a pair of semimicroelectrodes was introduced simultaneously to the thalamic ventral lateral region from the prefrontal area. The Vim nucleus was identified tentatively by characteristic high background activity which contrasted to that found in its rostral part and by superimposed large amplitude spontaneously active units. 3. In this high activity zone, 135 units (approximately 1/5 of the recorded units) responded to natural stimulation applied to contralateral body parts. Among them, approximately 90% responded to a passive or active movement of a joint. Several lines of evidence suggested that probably muscle receptors were responsible. 4. The rest of units (approximately 10%) responded to light touch applied to contralateral skin surface. Convergent responses between kinesthetic and tactile units were never encountered. Also, kinesthetic and tactile neurons were geographically separated. The latter were found always at the end of our oblique trajectory, following the kinesthetic neurons. 5. Neurons with sensory responses were clustered mostly within the confines of the Vim nucleus, probably extending caudally to the ventrocaudalis externus anterior of Hassler. Evidence for a somatotopic representation in the Vim nucleus was obtained. 6. Electrical stimulation of the appropriate peripheral nerve produced responses of the same thalamic unit(s) that responded to natural stimulation. The latency to upper limb nerve stimulation was between approximately 10 and 20 ms. It was almost fixed in a given case. 7. It is concluded that the Vim nucleus receives kinesthetic afferent input from the contralateral body parts (mainly from the muscle receptor) and may be concerned with muscle sense. This may explain why a small, selective coagulation of the physiologically identified Vim has such a constant effect on several different kinds of tremor.

Somatotopic organization of the third somatosensory area (SIII) in cats.

Multiunit microelectrode recording techniques were used to study the location and organization of the third somatosensory area (SIII) in cats. Representations of all major contralateral body parts were found in a small region of cortex along the lateral wing of the ansate sulcus and between the lateral sulcus and the suprasylvian sulcus. The systematic map of the body surface included forepaw and face regions previously identified as parts of SIII. The forepaw representation was generally buried on the rostral bank of the lateral wing of the ansate sulcus. The representations of the face and mystacial vibrissae were largely exposed on the rostral suprasylvian gyrus, but part of the representation of the face was also buried in the lateral wing of the ansate sulcus. Representations of the trunk and hindlimb extended from the suprasylvian gyrus onto the medial bank of the suprasylvian sulcus. We had expected to find these latter body parts in more medial cortex just caudal to the representation of these parts in the first somatosensory area (SI). Instead, neurons in penetrations in cortex caudal to the SI trunk and hindlimb representations were unresponsive to tactile stimulation. The unexpected location of the hindlimb in SIII led us to determine whether the proposed parts of SIII had similar cortical and thalamic connections. Injected anatomical tracers revealed that the representations of both the forelimb and hindlimb were interconnected with SI and a region of the thalamus just dorsal to the ventroposterior nucleus. Similarities in patterns of connections of forelimb and hindlimb portions of SIII supported the conclusion that SIII as presented here is a functional unit of cortex. We conclude that SIII has a somatotopic organization that does not parallel that in SI, and that SIII is not entirely coextensive with either area 5 or area 5a of Hassler and Muhs-Clement (1964).

The organization of the sensory and motor areas of cerebral cortex in the platypus (Ornithorhynchus anatinus).

AbstractThe organization of sensory and motor regions of the cerebral cortex has been studied in the platypus (Ornithorhynchus anatinus), of the order Monotremata. Comparisons were made with the organization found in the other representative of this order, the echidna, and with primitive species of eutherian and metatherian mammals. Evoked potential and single neuron studies revealed a large single area of somatosensory representation in the posterior region of the hemisphere, extending from an approximately mid‐sagittal position around to the region of the rhinal sulcus on the ventrolateral surface of the hemisphere. The mediolateral representation of contralateral body parts was consistent with the pattern in the primary somatosensory area of other mammalian species. No evidence of a second somatosensory area was found. Neurons with similar receptive fields were grouped in columns normal to the cortical surface and a highly ordered pattern of somatotopic representation was found. Within the large area of bill representation individual neurons had receptive fields which were often punctate and no more than 1 mm in diameter. They responded to dynamic components of tactile stimuli delivered to their receptive fields on the bill.Movements on the contralateral side of the body could be elicited by bipolar electrical stimulation over an area on the dorsal surface of the hemisphere which largely overlapped the somatosensory area, but extended further anteriorly towards the frontal pole of the hemisphere. Visual and auditory projection regions were found overlapping the somatosensory area in the posterior part of the hemisphere. The auditory area overlapped the visual area and appeared to be displaced posteromedially in relation to its position in other species, a displacement which may be a consequence of the large expanse of cortical area associated with the bill.The observation that a large proportion of cortical area is devoted to specific sensory and motor function in platypus corresponds with earlier findings in primitive eutherian and metatherian species. The platypus neocortex appears to represent a more primitive stage of cortical development than that found in the other member of the order Monotremata, the echidna.

A note on alterations of personal orientation in Parkinsonism

As an extension of previous findings that Parkinson patients have alterations on tasks relating to body orientation, 54 patients were compared with 36 age-matched controls on the non-verbal portion of the Weinstein [1] body scheme task. Patients with predominantly right-sided symptoms and those with non-lateralized symptoms made significantly more total errors than the controls. Analysis of the error distributions indicated that patients with inferred right hemisphere damage and those with inferred bilateral damage tended to make significantly more bilateral errors than the normals; those patients with inferred left hemisphere damage differed from the controls only when required to point to contralateral body parts with the stimulus figure in the opposite orientation.