Supplementary Sensory Area Research Articles

Activation of brain areas following ankle dorsiflexion versus plantar flexion: Functional magnetic resonance imaging verification.

Changes in activated areas of the brain during ankle active dorsiflexion and ankle active plantar flexion were observed in six healthy subjects using functional magnetic resonance imaging. Excited areas of ankle active dorsiflexion involved the bilateral primary motor area and the primary somatosensory area, as well as the bilateral supplementary sensory area, the primary visual area, the right second visual area, and the vermis of cerebellum. Excited areas of ankle active plantar flexion included the ipsilateral supplementary motor area, the limbic system, and the contralateral corpus striatum. Fine movements of the cerebral cortex control the function of the ankle dorsiflexion to a larger extent than ankle plate flexion, and the function of ankle plate flexion is more controlled by the subcortical area.

Extraoperative functional mapping of motor areas in epileptic patients by high-frequency cortical stimulation

The aim of this study was to investigate the usefulness of a short train of high-frequency (500 Hz) cortical stimulation to delineate the primary motor cortex (MI), supplementary motor area (SMA), primary somatosensory cortex (SI), supplementary sensory area (SSA), negative motor area (NMA), and supplementary negative motor area (SNMA) in patients with epilepsy who were undergoing functional mapping. Seventeen patients were studied, all of whom underwent functional mapping using 50-Hz electrical stimulation. After these clinical evaluations, cortical stimulations with a short train of electrical pulses at 500 Hz were performed through subdural electrodes placed at the MI, SMA, SI, SSA, NMA, and SNMA, which had been identified by 50-Hz stimulation, and surrounding cortical areas, while surface electromyography readings were recorded. Stimulation of the MI elicited motor evoked potentials (MEPs) in contralateral muscles. Stimulation of the SMA also induced MEPs in contralateral muscles but with longer latencies compared with the MI stimulation. Stimulation of the SMA did not elicit MEPs in ipsilateral muscles. Stimulation of the SI, SSA, NMA, and SNMA did not induce MEPs in any muscle. In one patient, MEPs were elicited without seizure induction by 500-Hz stimulation of the electrodes, whereas a 50-Hz stimulation of the same electrodes induced his habitual seizures. Extraoperative high-frequency stimulation with MEP monitoring is a useful complementary method for cortical mapping without inducing seizure. Stimulation of SMA induces MEPs in contralateral muscles, with longer latencies compared with the stimulation of MI. This finding may be useful for the differentiation between MI and SMA, especially in the foot motor areas.

Cytoarchitecture and cortical connections of the posterior cingulate and adjacent somatosensory fields in the rhesus monkey.

The cytoarchitecture and connections of the caudal cingulate and medial somatosensory areas were investigated in the rhesus monkey. There is a stepwise laminar differentiation starting from retrosplenial area 30 towards the isocortical regions of the medial parietal cortex. This includes a gradational emphasis on supragranular laminar organization and general reduction of the infragranular neurons as one proceeds from area 30 toward the medial parietal regions, including areas 3, 1, 2, 5, 31, and the supplementary sensory area (SSA). This trend includes a progressive increase in layer IV neurons. Area 23c in the lower bank and transitional somatosensory area (TSA) in the upper bank of the cingulate sulcus appear as nodal points. From area 23c and TSA the architectonic progression can be traced in three directions: one culminates in areas 3a and 3b (core line), the second in areas 1, 2, and 5 (belt line), and the third in areas 31 and SSA (root line). These architectonic gradients are reflected in the connections of these regions. Thus, cingulate areas (30, 23a, and 23b) are connected with area 23c and TSA on the one hand and have widespread connections with parieto-temporal, frontal, and parahippocampal (limbic) regions on the other. Area 23c has connections with areas 30, 23a and b, and TSA as well as with medial somatosensory areas 3, 1, 2, 5, and SSA. Area 23c also has connections with parietotemporal, frontal, and limbic areas similar to areas 30, 23a, and 23b. Area TSA, like area 23c, has connections with areas 3, 1, 2, 5, and SSA. However, it has only limited connections with the parietotemporal and frontal regions and none with the parahippocampal gyrus. Medial area 3 is mainly connected to medial and dorsal sensory areas 3, 1, 2, 5, and SSA and to areas 4 and 6 as well as to supplementary (M2 or area 6m), rostral cingulate (M3 or areas 24c and d), and caudal cingulate (M4 or areas 23c and d) motor cortices. Thus, in parallel with the architectonic gradient of laminar differentiation, there is also a progressive shift in the pattern of corticocortical connections. Cingulate areas have widespread connections with limbic, parietotemporal, and frontal association areas, whereas parietal area 3 has more restricted connections with adjacent somatosensory and motor cortices. TSA is primarily related to the somatosensory-motor areas and has limited connections with the parietotemporal and frontal association cortices.

Transient activation of a somatosensory area in painful hallucinations shown by fMRI.

The disturbance of somatosensory perception and bodily experiences, including somatosensory hallucinations, are main features of the coenaesthesia sub-syndrome of schizophrenia. We used functional MRI to study a coenaesthesia patient with rapidly fluctuating painful somatosensory hallucinatory perceptions. Transient brain activations accompanying hallucinations were similar to the pattern elicited in a control experiment (non-painful tactile stimulation). However, an area in the medial parietal cortex, including parts of the precuneus and previously characterised as a supplementary sensory area, was activated significantly stronger during hallucinations than the control condition. This finding demonstrates elevated brain activity in a somatosensory area accompanying painful somatic hallucinations.

Converging evidence from microstimulation, architecture, and connections for multiple motor areas in the frontal and cingulate cortex of prosimian primates.

In the present study, somatotopic organization, architectonic features, and patterns of connections were used to define motor areas in the frontal and cingulate cortex of the prosimian primate Galago garnetti. Sites throughout portions of the motor cortex were electrically stimulated with microelectrodes at the approximate depth of layer V. In some of the same animals, injections in primary motor cortex (M1), and in the spinal cord, revealed patterns of connections with physiologically identified motor areas. Results were related to cortical architecture in brain sections processed for Nissl, myelin, cytochrome oxidase, acetylcholinesterase, or neurofilaments. Evidence was obtained for a number of fields previously identified in simian primates, including M1, dorsal premotor field with caudal (PMDc) and rostral (PMDr) divisions, ventral premotor area (PMV), supplementary motor area (SMA), presupplementary motor area (pre-SMA), frontal eye field (FEF), and cingulate motor areas, CMAr and CMAc located rostrally and caudally, respectively. In addition, we distinguished area 6Ds of Preuss and Goldman-Rakic (1991a) between PMV and PMDc, and a more posterior cingulate sensorimotor area (CSMA) with motor connections that may correspond to the supplementary sensory area of monkeys. Areas M1, SMA, PMDc, PMV, CMAr, CMAc, and CSMA projected to the spinal cord, while all of these areas and 6Ds projected to M1. Although area M1 had the lowest stimulation thresholds for evoked movements, movements were also evoked from the other motor areas, as well as from somatosensory areas 3a and 3b. These results indicate that prosimian galagos have a complex of motor areas that closely resembles that in monkeys and suggest that at least 10 motor fields emerged early in primate evolution.

Cortical connections of the frontoparietal opercular areas in the Rhesus monkey

The connections of the frontoparietal opercular areas were studied in rhesus monkeys by using antero- and retrograde tracer techniques. The rostral opercular cortex including the gustatory and proisocortical motor (ProM) areas is connected with precentral areas 3, 1, and 2 as well as with the rostral portion of the opercular area which resembles the second somatosensory type of cortex (area SII) and the ventral portion of area 6. Its distant connections are with the ventral portion of prefrontal areas 46, 11, 12, and 13 as well as with the rostral insula and cingulate motor area (CMAr). The mid opercular region (areas 1 and 2) is connected with pre- and postcentral areas 3, 1, and 2 as well as SII. Additionally, it is connected with the ventral portion of area 6, area 44, area ProM, the gustatory area, and the rostral insula. Its distant connections are with area 4, the ventral portion of area 46, area 7b, and area POa in the intraparietal sulcus (IPS). The rostral parietal opercular region is connected with the postcentral portions of areas 3, 1, and 2; areas 5, 7, and SII; the gustatory area; and the vestibular area. Its other connections are with area 4, area 44, the ventral portion of area 46, area ProM, CMAr, and the supplementary motor area (SMA). The caudal opercular region is connected with the dorsal portion of area 3; areas 2, 5, and 7a; and areas PEa as well as IPd of IPS. It is also connected with area SII, insula, and the superior temporal sulcus. Its distant connections are with area 44; the dorsal portion of area 8 and the ventral portion of area 46; as well as CMAr, SMA, and the supplementary sensory area. This connectivity suggests that the ventral somatosensory areas are involved in sensorimotor activities mainly related to head, neck, and face structures as well as to taste. Additionally, these areas may have a role in frontal (working) and temporal (tactile) memory systems.

Cortical activation during reaching movements in the monkey as revealed by optical recording

We describe methods of localizing functional regions of the mesial wall, based on 47 patients studied intraoperatively or following chronic implantation of subdural electrodes. Somatosensory evoked potentials were recorded to stimulation of posterior tibial, dorsal pudendal, median, and trigeminal nerves. Bipolar cortical stimulation was performed, and in 4 cases movement-related potentials were recorded.The cingulate and marginal sulci formed the inferior and posterior borders of the sensorimotor areas and the supplementary motor area (SMA). The foot sensory area occupied the posterior paracentral lobule, while the genitalia were represented anterior to the foot sensory area, near the cingulate sulcus. The foot motor area was anterior and superior to the sensory areas, but there was overlap in these representations. There was a rough somatotopic organization within the SMA, with the face represented anterior to the hand. However, there was little evidence of the “pre-SMA” region described in monkeys. Complex movements involving more than one extremity were elicited by stimulation of much of the SMA. The region comprising the supplementary sensory area was not clearly identified, but may involve much of the precuneus. Movement-related potentials did not provide additional localizing information, although in some recordings readiness potentials were recorded from the SMA that appeared to be locally generated.

Localization of functional regions of human mesial cortex by somatosensory evoked potential recording and by cortical stimulation

We describe methods of localizing functional regions of the mesial wall, based on 47 patients studied intraoperatively or following chronic implantation of subdural electrodes. Somatosensory evoked potentials were recorded to stimulation of posterior tibial, dorsal pudendal, median, and trigeminal nerves. Bipolar cortical stimulation was performed, and in 4 cases movement-related potentials were recorded. The cingulate and marginal sulci formed the inferior and posterior borders of the sensorimotor areas and the supplementary motor area (SMA). The foot sensory area occupied the posterior paracentral lobule, while the genitalia were represented anterior to the foot sensory area, near the cingulate sulcus. The foot motor area was anterior and superior to the sensory areas, but there was overlap in these representations. There was a rough somatotopic organization within the SMA, with the face represented anterior to the hand. However, there was little evidence of the “pre-SMA” region described in monkeys. Complex movements involving more than one extremity were elicited by stimulation of much of the SMA. The region comprising the supplementary sensory area was not clearly identified, but may involve much of the precuneus. Movement-related potentials did not provide additional localizing information, although in some recordings readiness potentials were recorded from the SMA that appeared to be locally generated.

Supplementary Sensorimotor Seizures

The electroclinical and neuroimaging features, and response to antiepileptic drugs in 12 children with seizures involving the supplementary sensory motor area (SSMA) are reported from the British Columbia’s Children’s Hospital, Vancouver, BC, Canada.

Striatal connections of the parietal association cortices in rhesus monkeys

The corticostriatal connections of the parietal association cortices were examined by the autoradiographic technique in rhesus monkeys. The results show that the rostral portion of the superior parietal lobule projects predominantly to the dorsal portion of the putamen, whereas the caudal portion of the superior parietal lobule and the cortex of the upper bank of the intraparietal sulcus have connections with the caudate nucleus as well as with the dorsal portion of the putamen. The medial parietal convexity cortex projects strongly to the caudate nucleus, and has less extensive projections to the putamen. In contrast, the medial parietal cortex within the caudal portion of the cingulate sulcus projects predominantly to the dorsal portion of the putamen, and has only minor connections with the caudate nucleus. The rostral portion of the inferior parietal lobule projects mainly to the ventral sector of the putamen, and has only minor connections with the caudate nucleus. The middle portion of the inferior parietal lobule has sizable projections to both the putamen and the caudate nucleus. The caudal portion of the inferior parietal lobule as well as the lower bank of the intraparietal sulcus project predominantly to the caudate nucleus, and have relatively minor connections with the putamen. The cortex of the parietal opercular region also shows a specific pattern of corticostriatal projections. Whereas the rostral portion projects exclusively to the ventral sector of the putamen, the caudal portion has connections to the caudate nucleus as well. Thus, it seems that parietostriatal projections show a differential topographic distribution; within both the superior and the inferior parietal region, as one progresses from rostral to caudal, there is a corresponding shift in the predominance of projections from the putamen to the caudate nucleus. In addition, with regard to the projections to the putamen, the superior parietal lobule is related mainly to the dorsal portion, and the inferior parietal lobule to the ventral portion. The striatal projections of the cortex of the caudal portion of the cingulate gyrus (corresponding in part to the supplementary sensory area) and of the rostral parietal opercular region (corresponding in part to the second somatosensory area) are directed almost exclusively to the dorsal and ventral sectors of the putamen, respectively. This pattern resembles that of the primary somatosensory cortex. The results are discussed with regard to the overall architectonic organization of the posterior parietal region. Possible functional aspects of parietostriatal connectivity are considered in the light of physiological and behavioral studies.

Ventrolateral and dorsomedial somatosensory association cortex damage produces distinct somesthetic syndromes in humans.

Five somatosensory cortices have distinctive somatotopic representations, cytoarchitecture, and connectivity: primary somatosensory cortex (SI), ventrolateral association cortices (SII, SIII, and SIV), and dorsomedial association cortex (supplementary sensory area). Patients with focal lesions of ventrolateral (n = 5) and dorsomedial (n = 6) somatosensory association cortices (SACs) and hemiparetic (n = 8) and neurologically normal control patients (n = 14) underwent detailed somesthetic testing that encompassed basic, intermediate, and complex (tactile object recognition) somesthetic functions. Dorsomedial lesions acutely caused severe disruption of somesthetic processing and severe apraxia when the area of damage was extensive and involved anterior and posterior cortices. In contrast, ventrolateral lesions caused tactile agnosia. Chronically, sensorimotor function following dorsomedial damage improved considerably. Tactile agnosia following ventrolateral damage, however, was readily detectable for years following onset. Functional differences between ventrolateral and dorsomedial SACs may reflect parallel processing in dual somatosensory systems.

The relationship between human long-latency somatosensory evoked potentials recorded from the cortical surface and from the scalp

In scalp recordings, stimulation of the median nerve evokes a number of long-latency (40–300 msec) somatosensory evoked potentials (SEPs) whose neural origins are unknown. We attempted to infer the generators of these potentials by comparing them with SEPs recorded from the cortical surface or from within the brain. SEPs recorded from contralateral sensorimotor cortex can be characterized as “precentral,” “postcentral,” or “pericentral.” The scalp-recorded P45, N60 and P100 potentials appear to correspond to the pericentral P50, N90 and P190 potentials and are probably generated mainly in contralateral area 1 of somatosensory cortex. The scalp-recorded N70–P70 appear to correspond to the precentral and postcentral N80–P80 and are generated mainly in contralateral area 3b of somatosensory cortex. The scalp-recorded N120–P120 appear to correspond to the intracranial N100–P100 and are probably generated bilaterally in the second somatosensory areas. N140 and P190 (the “vertex potentials”) are probably generated bilaterally in the frontal lobes, including orbito-frontal, lateral and mesial (supplementary motor area) cortex. The supplementary sensory area probably generates long-latency SEPs, but preliminary recordings have yet to confirm this assumption. Most of the proposed correspondences are speculative because the different conditions under which scalp and intracranial recordings are obtained make comparison difficult. Human recordings using chronically implanted cortical surface electrodes, and monkey studies of SEPs which appear to be analogs of the human potentials, should provide better answers regarding the precise generators of human long-latency SEPs.

Learning of Sequential Finger Movements in Man: A Combined Kinematic and Positron Emission Tomography (PET) Study.

The cerebral structures participating in learning of a manual skill were mapped with regional cerebral blood flow (rCBF) measurements and positron emission tomography in nine healthy volunteers. The task was a complicated right-hand finger movement sequence. The subjects were examined at three stages: during initial practice of the finger movement sequence, in an advanced stage of learning, and after they had learnt the finger movement sequence. Quantitative evaluation of video tapes and electromyographic records of the right forearm and hand muscles demonstrated that the finger movements significantly accelerated and became more regular. Significant mean rCBF increases were induced in the left motor hand area, the left premotor cortex, the left supplementary motor area, the left sensory hand area, the left supplementary sensory area and the right anterior lobe of the cerebellum. During the learning process significant depressions of the mean rCBF occurred bilaterally in the superior parietal lobule, the anterior parietal cortex and the pars triangularis of the right inferior frontal cortex. The mean rCBF increases in these structures during the initial stage of learning were related to somatosensory feedback processing and internal language for the guidance of the finger movements. These activations disappeared when the subjects had learnt the finger movement sequence. Conversely, the mean rCBF significantly rose during the course of learning in the midsector of the putamen and globus pallidus on the left side. It is suggested that during the learning phase of this movement sequence, the basal ganglia were critically involved in the establishment of the final motor programme.

Somatosensory Discrimination of Shape: Tactile Exploration and Cerebral Activation.

This study of somatosensory discrimination of rectangular parallelepipeda with the right hand had three purposes: (i) to describe the exploratory finger movements; (ii) to reveal the anatomical brain structures specifically engaged in the production of exploratory finger movements; and (iii) to reveal the anatomical structures specifically engaged in the discrimination of tactually sensed shape. The thumb was the most active finger, moving with a mean exploration frequency of 2.4 Hz, as evident from videotape records of the exploratory finger movements. The cerebral structures activated during somatosensory discrimination were mapped by measurements of regional cerebral blood flow (rCBF) in six healthy male volunteers with positron emission tomography (PET) and the use of the computerized brain atlas of Greitz et al. (1991, J. Comp. Ass. Tomogr., 15, 26 - 38). The rCBF changes caused by somatosensory discrimination were compared point-to-point to a PET-study on right-hand finger movements and a PET-study on vibration stimulation of the right hand. From these results the following conclusions were drawn. The rCBF increase in the left superior parietal lobule indicated the site engaged in the analysis of shape. The rCBF increases in the left supplementary sensory area, bilaterally in premotor areas, in the left putamen, the right dentate nucleus and bilaterally in the posterior cerebellum were related to the control of the tactile exploratory finger movements. The rCBF increases in the right homologue of Broca's area, bilaterally in the superior prefrontal cortex and in the right midfrontal cortex probably resulted from working memory, the direction of attention, and the discrimination process.

The callosal system of the superior parietal lobule in the monkey.

The callosal connections of the superior parietal lobule, area 5 of Brodmann, were studied in macaque monkeys (M. nemestrina and M. fascicularis) using anatomical techniques based on both anterograde and retrograde axoplasmic transport of wheat-germ-agglutinin-conjugated horseradish peroxidase. From sagittal sections, two-dimensional flattened computer reconstructions of the volumes of cortical tissue containing callosal-projecting neurons (callosal efferent zone) and/or callosal terminal axons (callosal terminal territory) were obtained. Callosal zones were found in area 5, including the supplementary sensory area, in a limited part of area 6, i.e., in the supplementary motor area, in area 7b, in the cortex of the dorsal bank of the sylvian fissure, and in a limited part of area 7a, in the cortex of the upper third of the rostral bank of the superior temporal sulcus. Callosal neurons in all cortical areas studied, though with regional variations, predominated in layer IIIb, but were also very numerous in layers VI and V. They were rare in other cortical laminae. In the cortical regions projecting heterotopically to area 5, the tangential distribution of callosal neurons was discontinuous because of the presence of large acallosal regions. These were not observed in area 5, although here the distribution of callosal neurons waxed and waned in the tangential cortical plane. Callosal axons to and/or from area 5 crossed the midline in the posterior, presplenial part of the corpus callosum. In the superior parietal lobule they terminated in radial patches or columns, spanning layers I-IV. These columns of various width (200-2,000 micron) were separated by gaps of similar size, free of such terminals. Callosal neurons were present not only within, but also between, the callosal terminal columns. Callosal neurons located within the callosal terminal columns were, in a statistically significant way, more numerous than those located between them. The callosal efferent zone occupied 71% of the tangential domain of area 5, whereas the callosal terminal territory occupied only 49% of it. This difference is statistically significant. The discontinuous columnar arrangement of callosal terminals and the periodic distribution of callosal neurons in the lateral part of area 5 defined three main bands of callosal connections of irregular shape which were oriented mediolaterally and ran parallel to the main architectonic borders, the border between areas 2 and 5 and that between 5 and 7.

Ipsilateral symptoms caused by an arteriovenous malformation of the second or supplementary sensory area of the island of Reil

Ipsilateral symptoms caused by an arteriovenous malformation of the second or supplementary sensory area of the island of Reil