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PubMed1995

Functional magnetic resonance imaging mapping of the sensorimotor cortex with tactile stimulation.

The purpose of this study is to compare tactile stimulation of the palm with voluntary movement of the fingers as paradigms for mapping the sensorimotor cortex in functional magnetic resonance imaging. In 22 subjects, 24 sets of functional magnetic resonance images were obtained with echoplanar acquisitions and cross-correlation image processing techniques. Two tasks were employed: a motor task in which subjects moved the thumb and index finger of one hand and a sensory task in which the palm was scratched by another person. The activation from the two tasks coincided entirely in 20 sets and partially in 3 sets. In one case, no activation was seen with the motor task. The study suggests that tactile stimulation of the palm is useful and reliable for mapping the sensorimotor cortex.

Adult↗

PubMed1998

Intraoperative localization of functional regions in the sensorimotor cortex by neuronavigation and cortical mapping.

Surgery of lesions within the central region requires exact intraoperative anatomical orientation and knowledge of the position of functional cortical regions to minimize the surgical trauma and to avoid postoperative neurological deficits. We combined somatosensory evoked potential (SSEP) phase reversal and/or cortical electrical stimulation with neuronavigation in 26 patients for localization and visualization of functional cortical areas and their anatomical site in relation to the lesion. After location of the central sulcus by means of SSEP phase reversal, the precentral gyrus was electrically stimulated to detect functional motor regions. Electrode position was documented, and the functional regions were related to the site of the lesion using a specially developed neuronavigation system. In 11 of 15 patients the central fissure was located with SSEP phase reversal. Electrical stimulation yielded motor evoked potentials in 23 of the total 26 patients. The anatomical site of these functional regions and their relation to the lesion were evaluated with the neuronavigation system. The precentral gyrus, central sulcus, and postcentral gyrus could be identified in all 23 cases. The combination of intraoperative electrophysiological mapping and neuronavigation provides safe and reliable localization of the sensorimotor cortex. This technique is a promising tool to minimize the risk of surgically caused sensory and motor deficits.

Adult↗

PubMed1999

Differences in functional magnetic resonance imaging of sensorimotor cortex during static and dynamic finger flexion.

Functional magnetic resonance imaging (fMRI) studies of the human motor system have commonly used movement paradigms which contain a dynamic component; however, the relationship between the fMRI signal for motor tasks with and without a dynamic component is not known. We have investigated the relationship between the fMRI signal during a static finger flexion task and during dynamic finger flexion at 1-3 Hz, each at two levels of force (5% and 10% of maximum voluntary contraction). A small fMRI response could be recorded from only a few subjects during the static tasks. In contrast, a substantial fMRI response occurred during dynamic tasks in all subjects at both levels of force. The fMRI response was not significantly correlated with force or movement rate during the dynamic tasks. It is concluded that the factors responsible for generating an fMRI response are fundamentally different during steady contractions compared to those involving a dynamic component, and that the fMRI signal may be more sensitive to changes in the pattern of neural activation rather than the ongoing firing rate or extent of activation.

Adult↗

PubMed2004

The functional organization of the sensorimotor region of the subthalamic nucleus.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is viewed by many as the ultimate therapy targeting severe advanced stages of Parkinson's disease (PD). A fundamental constituent of the mechanisms underlying the therapeutic effects of DBS is clearly the functional organization of the STN; however, there is limited understanding of the organization of this structure in humans. Data from primates suggest that different domains can be identified in the STN, including a sensorimotor area with a segregated body map, as well as nonmotor areas. Recent clinical studies have used microelectrode recording to investigate the presence of a body map in the sensorimotor STN of PD patients. This paper will review and compare experimental and clinical data regarding the functional organization of the STN and discuss the clinical implications for PD patients undergoing STN DBS.

Animals↗

PubMed2002

Localization of sensorimotor cortex by using functional magnetic resonance imaging: comparison between finger tapping and palm scratching in normal volunteer.

The purpose of this study was to compare the location and intensity of activation of the sensorimotor cortex between finger tapping and palm scratching paradigms in normal volunteers and to consider using passive task instead of motor task in patients who are unable to perform motor task. Multishot echo-planar T2*-weighted imaging sequences at the level of the sensorimotor cortex were performed in axial plane during finger tapping and palm scratching paradigms in 13 normal volunteers. The authors found that the location of activation was slightly posterior only in bilateral passive task compared to bilateral motor task but there was no statistical significance. However, this observation was not seen in unilateral tasks. The intensity of activation of both motor and passive tasks was comparable. The authors conclude that in normal volunteers passive task (palm scratching) can be used instead of motor task (finger tapping) to localize the location of the sensorimotor cortex.

Adult↗

PubMed1995

Functional magnetic resonance imaging at 1.5 T during sensorimotor and cognitive task.

Functional activations of the human brain cortex were observed with a standard 1.5-tesla MR imaging system using a long time echo fast low-angle shot sequence. Neural activation increases regional cerebral blood flow resulting in increased capillaries and venous blood oxygenation. Processing requires adapted algorithms because the time course of intensity signal showed fluctuations of the baseline. The use of a 'follow-up' method to generate activation maps is proposed. Brain activation was detected in striate cortex during photic stimulation and in sensorimotor areas while subjects were moving their hands. In mental imagery tasks, we observed a primary and secondary visual cortex activation during memory recall of the flashing light. Motor ideation showed an activation of the rolandic areas.

Adult↗

PubMed2005

The synaptic microcircuitry associated with primary afferent terminals in the interpolaris and caudalis of trigeminal sensory nuclear complex.

Previous ultrastructural studies indicating a higher number of axoaxonic contacts on individual low-threshold mechanoreceptive afferents in the principalis (Vp) than in the oralis (Vo) of cat trigeminal sensory nuclear complex (TSNC) suggest that the synaptic microcircuitry associated with primary afferents manifests unique differences across the sensory nuclei of TSNC. To address this issue, we analyzed synaptic microcircuits associated with fast adapting vibrissa afferent terminals in the interpolaris (Vi) and caudalis (Vc, laminae III/IV) by using intraaxonal injections of horseradish peroxidase (HRP) in cats. Forty-two and 65 HRP-labeled boutons were analyzed in the Vi and Vc, respectively. The labeled boutons contained clear, spherical vesicles. They most frequently formed asymmetric axodendritic synapses and were commonly postsynaptic to unlabeled axon terminals containing pleomorphic vesicles (p-endings) with symmetric junctions. The examination of synaptic contacts over the entire surface of individual boutons indicated that the afferent boutons made contacts with an average of two postsynaptic targets in the Vi and Vc. In contrast, axoaxonic contacts, and labeled boutons participating in synaptic triads, where p-endings contacted both the boutons and their postsynaptic targets, were, on average, higher in the Vi than in the Vc. These results suggest that the output of sensory information conveyed through low-threshold mechanoreceptive afferents is more strongly controlled at the level of the first synapse by presynaptic and postsynaptic mechanisms in the Vi responsible for sensory discriminative functions than in the Vc for sensorimotor reflexive functions.

Afferent Pathways↗

PubMed1994

Comparative effects of fluoxetine, amitriptyline and serotonin on functional motor recovery after sensorimotor cortex injury.

A recent investigation of the effects of the antidepressants desipramine and trazodone on behavioral recovery in brain-injured animals suggested that antidepressants, which act to increase noradrenergic activity in the brain, may facilitate the rate of recovery, whereas those that act to increase serotonergic (5-HT) activity may hinder recovery and reinstate deficits in recovered animals. The present study was designed to evaluate these findings further by assessing the effect of a single intraperitoneal injection of fluoxetine (a relatively pure 5-HT reuptake blocker), amitriptyline (a mixed 5-HT and noradrenergic reuptake blocker with alpha 1-adrenergic receptor blocking activity) or a single intraventricular infusion of 5-HT on recovery of beam-walking ability in animals with a unilateral sensorimotor cortex injury. None of the drugs significantly affected the rate of recovery. Although fluoxetine was ineffective in reinstating the motor deficit in recovered animals, amitriptyline reinstated the deficit in a dose-dependent fashion. Infusion of 5-HT resulted in an extremely transient reinstatement of the deficit, which was largely attributable to its short-term sedative properties. These results suggest that 5-HT may be less involved in functional recovery than previously thought. They also add further support to previous findings that indicate that drugs which act to antagonize alpha 1-adrenergic activity (e.g., phenoxybenzamine) may interfere with motor recovery after sensorimotor cortex injury. An appreciation of the potential impact of certain antidepressants on functional recovery in brain-injured patients appears warranted.

Amitriptyline↗

PubMed1997

Abnormal functional lateralization of the sensorimotor cortex in patients with schizophrenia.

Previous neuroimaging studies have suggested that patients with schizophrenia fail to recruit appropriate focal patterns of cortical responses to cognitive tasks. We investigated whether patients with schizophrenia show a normal focal response to a simple motor task. Seven strongly right-handed patients with schizophrenia and seven strongly right-handed normal subjects performed motor tasks of increasing complexity. Patients were unable to recruit as focal a response even to a simple, automatic sequential finger movement task. They showed greater ipsilateral activation in the primary sensorimotor and lateral premotor regions and had a significantly lower laterality quotient than normal subjects. These phenomena increased with the complexity of the task. These results demonstrate a functional disturbance in the cortical motor circuitry of patients with schizophrenia.

Adult↗

PubMed1990

The significance of foliation and fissuration of cerebellar cortex. The cerebellar folium as a fundamental unit of sensorimotor integration.

I propose the general hypothesis that each individual folium in the cerebellum is an integrative module that is involved in unique sets of sensorimotor transactions. Although the basic types of operations carried out by cerebellar cortex may be similar in all folia, the mosaic of afferent sources, intrinsic organization and efferent destinations appear to be unique for each folium. I believe that this conception is supported by: 1) comparative data which illustrate species-typical folial patterns, 2) neuroanatomical data which reveal not only different structural features of folial crowns and fundi, but differential afferent and efferent connectivity of different folia as well, 3) physiological data, which demonstrate unique patterns of afferent activity in different folia, and especially by 4) ontogenetic data which establish that each folial crown expands and differentiates into an architecturally distinct cortical entity. Taken together, all these lines of evidence suggest that the numbers and patterns of folia exhibited by the cerebellar cortex of different mammals are morphological indicators of differential organization of sensorimotor control functions in each animal. Even intraspecific individual variations in folial number, size and pattern may signify structural-functional determinants of some individual differences in sensorimotor transactions. Since so little research has addressed the many testable ideas embodied in these general hypotheses, it seems to me that neuroscientists have a long way to go to clarify how the many different folia and lobules of cerebellar cortex actually function in the common, everyday, orderly, dynamic and ongoing reflex, postural, learned and deliberate behavioral sequences that characterize the normal behavioral repertoires of different animals. The enormous advances in understanding brought forth by the extensive research and writings of Professor Brodal and his colleagues have expanded our horizons to avail us of an enormous range of new vistas into cerebellar functional morphology. It is now the task of neurobiologists to explore these diverse new domains in ever greater depth and detail.

Animals↗

PubMed2006

A sensorimotor map: modulating lateral interactions for anticipation and planning.

Experimental studies of reasoning and planned behavior have provided evidence that nervous systems use internal models to perform predictive motor control, imagery, inference, and planning. Classical (model-free) reinforcement learning approaches omit such a model; standard sensorimotor models account for forward and backward functions of sensorimotor dependencies but do not provide a proper neural representation on which to realize planning. We propose a sensorimotor map to represent such an internal model. The map learns a state representation similar to self-organizing maps but is inherently coupled to sensor and motor signals. Motor activations modulate the lateral connection strengths and thereby induce anticipatory shifts of the activity peak on the sensorimotor map. This mechanism encodes a model of the change of stimuli depending on the current motor activities. The activation dynamics on the map are derived from neural field models. An additional dynamic process on the sensorimotor map (derived from dynamic programming) realizes planning and emits corresponding goal-directed motor sequences, for instance, to navigate through a maze.

Action Potentials↗

PubMed2001

A comparison of long-term functional outcome after 2 middle cerebral artery occlusion models in rats.

BACKGROUND AND PURPOSE: Proven behavioral assessment strategies for testing potential therapeutic agents in rat stroke models are needed. Few studies include tasks that demand higher levels of sensorimotor and cognitive function. Because behavioral outcome and rate of recovery vary among ischemia models, there is a need to characterize and compare performance on specific tasks across models. METHODS: To this end, sensorimotor and cognitive deficits were assessed during a 5-week period after either permanent proximal middle cerebral artery occlusion (pMCAO) or permanent distal middle cerebral artery occlusion combined with a 90-minute occlusion of both common carotid arteries (dMCAO/tCCAO) in Sprague-Dawley rats. The EBST, hindlimb and forelimb placing, and cylinder tests were given at regular intervals postinjury to assess sensorimotor function. Cognitive function was assessed with a multitrial water navigation task. RESULTS: pMCAO, which caused both striatal and cortical damage, produced persistent sensorimotor and cognitive deficits. Limb placing responses and postural reflexes were impaired throughout the month of testing. A persistent bias for using the ipsilateral forelimb for wall movements in the cylinder test was observed as well as a bias for landing on the opposite forelimb. pMCAO rats were also impaired in the water navigation task. dMCAO/tCCAO, which caused only cortical damage, produced similar sensorimotor deficits, but these were greatly diminished by 2 weeks after injury. No impairment was found for water tank navigation. Correlations between forelimb placing (both models), water navigation performance (pMCAO model), and sensorimotor asymmetry (dMCAOtCCAO model) and infarct volume were observed. CONCLUSIONS: Based on the range of functions affected and stability of observed deficits, the pMCAO model appears to be preferable to the dMCAO/tCCAO model for use in assessing therapeutic agents for stroke.

Animals↗

PubMed2005

Relationship between sensorimotor adaptation and cognitive functions in younger and older subjects.

We investigated whether deficits of adaptive improvement in seniors are related to an age-dependent decay of the brain's executive functions. Younger and older subjects completed a battery of cognitive tests, and preformed aimed arm movements before and during exposure to rotated visual feedback. In accordance with previous work, we found that adaptive improvement during exposure was degraded in seniors, while the transfer of adaptation to a new motor task was not. This pattern of findings confirms that strategic control but not sensorimotor recalibration is affected by old age. Using multiple linear regression (MLR) to extract separate executive components from our test battery, we found that basic response speed and decision-making, but not the inhibition of prepotent responses or mental flexibility, were degraded in our older subjects. Again using MLR, we found that degraded adaptive improvement in our seniors was partly related to the decay of basic response speed and decision-making, and partly to age-dependent phenomena not addressed by our cognitive-test battery. Finally, we observed that interindividual variability of cognition and adaptive improvement was larger in old than in young subjects, which could explain why some previous studies found degraded adaptation in seniors while others did not.

Adaptation, Physiological↗

PubMed2001

Remodelling of sensorimotor maps in paraplegia: a functional magnetic resonance imaging study after a surgical nerve transfer.

The adult mammalian brain has the capacity of reorganising its neural connections in response to lesions/modifications of the peripheral and central nervous system. We show in vivo, using functional magnetic resonance imaging (fMRI), that in paraplegics the lower-limb sensorimotor cortex is invaded by the arm representation. This functional reshaping appears to be reversible. Indeed, surgical transfer of the ulnar nerve to the ipsilateral quadriceps and hip muscles allowed their contraction in a paraplegic patient. During fMRI, these voluntary movements activated the hip and thigh representation in sensorimotor cortex. We suggest that the functional recovery of the lower-limb functional maps might have been driven by the restored somatosensory inputs from the reactivated periphery. The voluntary movements of the lower-limbs are regained through the 're-awakening' of the corresponding sensorimotor cortex.

Adult↗

PubMed1996

[Functional imaging of the sensorimotor cortex using an ultra-fast MR imaging method].

UNLABELLED: The aim of this study was to assess changes in brain activity during a motor task and variable sensory stimulation using echo planar imaging, which represents the fastest clinically usefull imaging technique available. MATERIALS AND METHODS: The subjects of this study were 11 healthy-volunteers, 4 males and 11 females, with an average of 26.4 years. The subjects were instructed to tap the fingers of one hand as the motor task. Compressed air was applied 5 times a second as "simple" sensory stimulation. Simple figures were drawn on the subjects palm as "complex" sensory stimulation. In all cases, functional imaging was performed by T2*-weighted echo planar imaging (TE = 53 msec, TR = 3000 msec, flip angle = 90 degrees, matrix 64 x 64, FOV = 205 mm, slice thickness = 8 mm) alternately at rest and during the task (intervals: 30 sec). A total of 60 images was collected in 3 minutes. Images obtained by subtracting images at rest and during the task were analyzed. RESULTS AND DISCUSSION: Almost all subjects showed a transient signal increase in the contralateral paracentral region during simple sensory stimulation. Continuous signal increases in the contra- and/or ipsi-lateral para-central region were observed during complex sensory stimulation. Some exhibited signal increases in the parietal or frontal association cortex, but they disappeared when subject's attention was distracted during stimulation. All subjects displayed signal increases in the contralateral para-central region during the motor task. Some of them exhibited signal increases in the medial frontal area (supplementary motor area) and ipsilateral para-central region. These results suggest that the signal increases of functional MRI reflect not only simple reactions to stimulation but higher cerebral function as well.

Adult↗

PubMed2006

Sensorimotor gating and dopamine function in postpartum rats.

There is much speculation regarding the effects of estrogen withdrawal at the end of pregnancy on forebrain dopamine, however, few studies have directly examine changes in this system postpartum. The present work sought to determine what changes in forebrain dopamine function occur in the postpartum rat. Specifically, prepulse inhibition of the acoustic startle response (PPI) was measured in primiparous female rats on postpartum day 2 (PPD2) or 14 (PPD14) following treatment with saline or the dopamine D2 agonist, quinpirole. Diestrus (DI) females served as controls. Dopamine content and turnover as well as cyclic AMP (cAMP) accumulation were determined within the nucleus accumbens and dorsal striatum in these same females. In addition, circulating levels of plasma corticosterone, estradiol and progesterone were measured. PPI was significantly disrupted in both postpartum groups. This effect was associated with decreased cAMP content within the nucleus accumbens. Quinpirole treatment (0.1 and 0.5 mg/kg) dose-dependently disrupted PPI in DI controls while PPD2 and PPD14 animals demonstrated reduced sensitivity to the D2 agonist. PPD14 animals demonstrated increased startle amplitude, an effect that was attenuated by quinpirole treatment. PPD14 females were also less sensitive to quinpirole-mediated reductions in DA turnover within the nucleus accumbens and both PPD2 and PPD14 females had an attenuated response to the stimulatory effects of quinpirole on corticosterone secretion. Collectively these findings suggest that the postpartum period is associated with reduced sensorimotor gating and altered forebrain DA systems, which may be related to shifts in circulating hormones.

Animals↗

PubMed1996

NADPH-diaphorase in the developing rat: lower brainstem and cervical spinal cord, with special reference to the trigemino-solitary complex.

A previous study indicated that in adult rat, a distinctive neuronal group in the dorsomedial division of the subnucleus oralis of the spinal trigeminal nucleus (SpVo) and the rostrolateral part of the nucleus of the solitary tract (Sn) is stained for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), and suggested that the labeled structures are involved with sensorimotor reflexive functions. This study aimed to characterize the developmental expression of NADPH-d in SpVo and Sn, including other areas of the lower brainstem and cervical spinal cord, by means of the enzyme histochemical staining technique, from the prenatal through the postnatal period. On embryonic day 12 (E12), no neurons in the brain were stained for NADPH-d, whereas blood vessels were stained. Labeling in the vessels was consistently present throughout pre- and postnatal periods but decreased with development. On E15, labeled neurons appeared in the dorsomedial part of SpVo and the rostrolateral part of Sn, but not in the other nuclei. The labeled neurons in both nuclei increased in numbers drastically to E17. Postnatally, they tended to increase gradually in Sn, but to decrease slightly in SpVo. The cell size of labeled neurons reached a plateau at E17 in SpVo, but at postnatal day 4 (P4) in Sn. In other nuclei on E17, labeling appeared in the lateral paragigantocellular reticular, intermediate reticular, medullary reticular, pedunculopontine tegmental, and spinal vestibular nuclei, and laminae V, VI, and X of the cervical spinal cord. On E20 and P0, labeling appeared in the dorsal column, laterodorsal tegmental, raphe obscurus, parvocellular reticular, ventral gigantocellular reticular, and parahypoglossal nuclei, and laminae IX of the cervical spinal cord. On P4 labeling appeared in the parabrachial and median raphe nuclei, medial and caudolateral Sn, the magnocellular zone of subnucleus caudalis of the spinal trigeminal nucleus (SpVc), and laminae III/IV of the cervical spinal cord. On P10, labeling appeared in the paratrigeminal and dorsal raphe nuclei, the superficial zone of SpVc, and laminae I/II of the cervical spinal cord. No newly labeled neurons appeared in any nuclei after P14. The very early appearance of NADPH-d staining in SpVo and Sn, which precedes the appearance of NADPH-d elsewhere in the brainstem, suggests that the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) system has an important role for primitive orofacial sensorimotor reflexive functions. Furthermore, the pattern of developmental expression of NADPH-d in SpVo and Sn suggests that the NO/cGMP system is organized in a distinct manner in different nuclei.

Afferent Pathways↗

PubMed2006

Long-term effects of ranirestat (AS-3201) on peripheral nerve function in patients with diabetic sensorimotor polyneuropathy.

OBJECTIVES: We aimed to determine whether ranirestat, an aldose reductase inhibitor, maintains the improved nerve function observed in patients with diabetic sensorimotor polyneuropathy (DSP) after completing a 12-week nerve biopsy study. RESEARCH DESIGN AND METHODS: Patients with mild to moderate DSP, as determined by the presence of sural nerve responses, were enrolled in a double-blind, placebo-controlled biopsy trial and randomized to placebo or 5 or 20 mg/day ranirestat for 12 weeks. Patients completing this biopsy study were offered a 48-week extension at the same ranirestat dose or at 5 mg/day ranirestat if they were originally treated with placebo. Electrophysiological tests, the Toronto Clinical Neuropathy Score, and vibration perception thresholds (VPTs) were performed at entry and at 12 (end of the biopsy study) and 60 (end of the 48-week extension) weeks. RESULTS: Peroneal motor nerve conduction velocity (NCV) improved in the 20-mg/day group following 60 weeks of treatment. Sural and median sensory NCV improved after both 12 and 60 weeks of treatment with 20 mg/day. VPT improved after 60 weeks of treatment with 20 mg/day. Ranirestat was well tolerated with no difference in adverse events between the 5- and 20-mg/day groups. CONCLUSIONS: Twenty milligrams ranirestat per day improves NCV and VPT following 60 weeks of administration. The improved sensory nerve function observed after 12 weeks of therapy was maintained at 60 weeks, and improved motor nerve function was observed at 60 weeks.

Aldehyde Reductase↗