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PubMed1995

The role of the left somatosensory cortex in human hand movement.

Hemispheric dominance for motor control in the human brain is still unclear. Here we propose asymmetric sensorimotor integration during human hand movements. We investigated the dexterity of hand movements and related sensory functions in four right-handed patients with cerebrovascular lesions in the postcentral gyrus. To clarify the distributions of cortical damage, semiquantitative analysis of regional cerebral blood flow (rCBF) was performed using single photon emission computed tomography (SPECT), and a three-dimensional surface display was generated from SPECT. Scores on motor and sensory tasks and rCBF values in the patients were compared with those in control subjects. All patients presented with asymmetric clumsiness of complex finger movements, in association with impairments of combined sensations such as stereognosis. These findings were indicative of a disorder of sensory information processing necessary to guide the movements. Two patients with left hemispheric damage showed bilateral clumsy hands, predominating on the right side, while the other two patients with right hemispheric damage showed only a left clumsy hand. In agreement with asymmetric clumsiness, measurement of rCBF along with a three-dimensional surface display revealed cortical hypoperfused areas, mainly in the perirolandic cortices, comprising the primary motor and somatosensory cortices. Perirolandic cortical hypoperfusion was bilateral in the two patients with bilateral clumsy hands, but only on the right side in the other two patients with left clumsy hands. These results suggest a dominant role of the left somatosensory cortex in sensorimotor integration for complex finger movements of humans.

Aged↗

PubMed2005

Improved sensory relearning after nerve repair induced by selective temporary anaesthesia - a new concept in hand rehabilitation.

The outcome after nerve repair in adults is generally poor. We hypothesized that forearm deafferentation would enhance the sensory outcome by increasing the cortical hand representation. A prospective, randomized, double-blind study was designed to investigate the effects of cutaneous forearm anaesthesia combined with sensory re-education on the outcome after ulnar or median nerve repair. During a 2 week period, a local anaesthetic cream (EMLA (n = 7) or placebo (n=6) was applied repeatedly onto the flexor aspect of the forearm of the injured arm and combined with sensory re-education. Evaluation of sensory function was carried out at regular intervals and at 4 weeks after the last EMLA/placebo session. The EMLA group showed significant improvement compared to placebo in perception of touch/pressure, tactile gnosis and in the summarized outcome after 6 weeks. These results suggest that cutaneous forearm anaesthesia of the injured limb, in combination with sensory re-education, can enhance sensory recovery after nerve repair.

Adult↗

PubMed1995

Transmembrane signaling characterized in bacterial chemoreceptors by using sulfhydryl cross-linking in vivo.

Transmembrane signaling by bacterial chemoreceptors is thought to involve conformational changes within a stable homodimer. We investigated the functional consequences of constraining movement between pairs of helices in the four-helix structure of the transmembrane domain of chemoreceptor Trg. Using a family of cysteine-containing receptors, we identified oxidation treatments for intact cells that catalyzed essentially complete sulfhydryl cross-linking at selected positions and yet left flagellar and sensory functions largely unperturbed. Constraining movement by cross-links between subunits had little effect on tactic response, but constraining movement between transmembrane segments of the monomer drastically reduced function. We deduce that transmembrane signaling requires substantial movement between transmembrane helices of a monomer but not between interacting helices across the interface between subunits.

Bacterial Proteins↗

PubMed2001

Eagle's syndrome: a report of 4 patients treated using a modified extraoral approach.

PURPOSE: This study evaluated a slightly modified extraoral approach to removing the symptomatic elongated styloid process. A brief description of this surgical technique and its comparison to the intraoral approach is provided. PATIENTS AND METHODS: Four patients in whom an extraoral approach was used to expose and remove the elongated calcified stylohyoid complex were evaluated. Five sides were treated and reviewed individually. All patients were interviewed preoperatively and postoperatively, and their records were thoroughly examined. Patients were objectively evaluated for pain, function, sensory and motor nerve deficits, and aesthetics. RESULTS: Follow-up time ranged from 6 to 39 months with an average of 21 months. Improvement in the original symptoms was reported for 4 of the 5 operated sides. Three of 5 procedures resulted in more than an 80% reduction in pain and improvement in function. All patients had a satisfactory cosmetic result and no paresthesia. CONCLUSIONS: The advantages of the extraoral approach are reflected in this small retrospective study by the absence of perioperative complications and the minimal blood loss, surgical morbidity, and hospital stay.

Adult↗

PubMed2001

Epinephrine increases the neurotoxic potential of intrathecally administered lidocaine in the rat.

BACKGROUND: Epinephrine is commonly added to lidocaine solutions to increase the duration of spinal anesthesia. Despite this common usage, the effect of epinephrine on the neurotoxic potential of this anesthetic is not known. The current experiments investigated whether adding epinephrine increases functional impairment or histologic damage induced by spinal administration of lidocaine in the rat. METHODS: Eighty rats were divided into four groups to receive an intrathecal injection of normal saline containing either 5% lidocaine, 5% lidocaine with 0.2 mg/ml of epinephrine, 0.2 mg/ml of epinephrine, or normal saline alone. Animals were assessed for persistent sensory impairment using the tail-flick test administered 4 and 7 days after infusion. Animals were then killed, and the spinal cord and nerve roots were prepared for neuropathologic evaluation. RESULTS: Rats given 5% lidocaine developed persistent sensory impairment and histologic damage, and the addition of epinephrine resulted in a further significant increase in injury. Sensory function in animals given epinephrine without anesthetic was similar to baseline and did not differ from saline. Histologic changes in animals treated with epinephrine alone did not differ significantly from saline controls. CONCLUSIONS: The neurotoxicity of intrathecally administered lidocaine is increased by the addition of epinephrine. When making clinical recommendations for maximum safe intrathecal dose of this anesthetic, one may need to consider whether the solution contains epinephrine.

Anesthesia, Spinal↗

PubMed1998

A comparison of the linear tuning properties of two classes of axons in the bullfrog lagena.

Various vertebrate inner-ear end organs appear to have switched their sensory function between equilibrium sensing and acoustic sensing over the courses of various lines of evolution. It is possible that all that is required to make this transition is to provide an end organ with access to the appropriate stimulus mode and frequency range. If, as we believe, however, the adaptive advantage of an acoustic sensory system lies in its ability to sort the total acoustic input into components that correspond to individual acoustic sources, and the adaptive advantage of an equilibrium sensory system lies in its ability to compute the total orientation and motion of the head without regard to the individual sources contributing to that orientation and motion, then it is easy to argue that the differences between acoustic and equilibrium sensors should be more profound than simply access to the appropriate stimuli. Effective signal-sorting requires high resolution in both time and frequency; to achieve this resolution, a peripheral tuning structure must be one of high dynamic order (i.e., constructed from multiple independent energy storage elements). If the peripheral tuning structure simply converts head acceleration to head displacement, velocity, or jerk (i.e., provides one or two steps of integration or differentiation with respect to time, where one energy storage element per step is required), then high dynamic order is inappropriate. Because the bullfrog lagena possesses both acoustic and equilibrium sensitive regions, it is especially suited for comparing these two sensor types and addressing the question of dynamic order of tuning. In this paper we report observations of the linear tuning properties of bullfrog lagenar primary afferent nerve fibers obtained by stimulating the lagena with random, dorsoventral micromotion over the frequency range from 10 Hz to 1.0 kHz. Tuning curves obtained by reverse correlation analysis and discrete Fourier transformation were used to estimate the dynamic order of each fiber's associated peripheral tuning structure. We found two classes of lagenar afferent axons--those with lowpass amplitude tuning characteristics (44 units) and those with bandpass amplitude tuning characteristics (73 units). Lowpass units were found to originate at the equilibrium region of the macula, and they exhibited low dynamic order--summed low- and high-frequency slopes (absolute values) ranged from 10 dB/decade to 64 dB/decade, implying dynamic orders of less than one to three (the modal value was equal to one). Bandpass units were found to originate at the acoustic region of the macula, and they exhibited higher dynamic order than lowpass units--summed low- and high-frequency slopes (absolute values) ranged from 53 dB/decade to 185 dB/decade, implying dynamic orders of three to nine (the modal value was equal to five). It appears that while lagenar equilibrium and acoustic sensors both possess access to signals in the acoustic frequency range, lagenar acoustic sensors are tuned by means of peripheral structures with markedly greater dynamic order and consequently markedly greater physical complexity. These results suggest that steep-sloped (high-dynamic-order) tuning properties reflect special adaptations in acoustic sensors not found in equilibrium sensors, and that any evolutionary transition between the two sensor types must have involved profound structural changes.

Acoustic Maculae↗

PubMed2005

Anti-tubulin labeling reveals ampullary neuron ciliary bundles in opisthobranch larvae and a new putative neural structure associated with the apical ganglion.

This investigation examines tubulin labeling associated with the apical ganglion in a variety of planktotrophic and lecithotrophic opisthobranch larvae. Emphasis is on the ampullary neurons, in which ciliary bundles within the ampulla are strongly labeled. The larvae of all but one species have five ampullary neurons and their associated ciliary bundles. The anaspid Phyllaplysia taylori, a species with direct development and an encapsulated veliger stage, has only four ampullary neurons. The cilia-containing ampulla extends to the pretrochal surface via a long, narrow canal that opens to the external environment through a very small pore (0.1 microm diameter). Cilia within the canal were never observed to project beyond the opening of the apical pore. The ampullary canals extend toward and are grouped with the ciliary tuft cells and remain in this location as planktotrophic larvae feed and grow. If, as has been reported, the ciliary tuft is motile, the pores may be continually bathed in fresh seawater. Such an arrangement would increase sensitivity to environmental chemical stimuli if the suggested chemosensory function of these neurons is correct. In general, ciliary bundles of newly hatched veligers are smaller in planktotrophic larvae than in lecithotrophic larvae. In planktotrophic larvae of Melibe leonina, the ciliary bundles increase in length and width as the veligers feed and grow. This may be related to an increase in sensitivity for whatever sensory function these neurons fulfill. An unexpected tubulin-labeled structure, tentatively called the apical nerve, was also found to be associated with the apical ganglion. This putative nerve extends from the region of the visceral organs to a position either within or adjacent to the apical ganglion. One function of the apical nerve might be to convey the stimulus resulting from metamorphic induction to the visceral organs.

Animals↗

PubMed1999

Overexpression of Arabidopsis phytochrome B inhibits phytochrome A function in the presence of sucrose.

Overexpression of phytochrome B (phyB) in Arabidopsis has previously been demonstrated to result in dominant negative interference of phytochrome A (phyA)-mediated hypocotyl growth inhibition in far-red (FR) light. This phenomenon has been examined further in this study and has been found to be dependent on the FR fluence rate and on the availability of metabolizable sugars in the growth medium. Poorly metabolized sugars capable of activating the putative hexokinase sensory function were not effective in eliciting the phytochrome interference response. Overexpressed phyB lacking the chromophore-binding site was also effective at inhibiting the phyA response, especially at higher fluence rates of FR. Overexpressed phyB produces the dominant negative phenotype without any apparent effect on phyA abundance or degradation. It is possible that phyA and phyB interact with a common reaction partner but that either the energy state of the cell or a separate sugar-signaling mechanism modulates the phytochrome-signaling interactions.

Arabidopsis↗

PubMed2001

Mild diabetic neuropathy affects ankle motor function.

OBJECTIVE: To evaluate the effect of age and diabetic neuropathy on ankle motor function in the frontal plane in terms of rate of torque development and capability for balance recovery. DESIGN: Case control study. Six older women with diabetic neuropathy compared to six women without neuropathy, matched for age and presence of diabetes mellitus; and nine healthy young women. BACKGROUND: Neuropathy causes a distal impairment in lower extremity sensory function which increases fall risk. Impairments in ankle inversion/eversion proprioceptive thresholds have been identified, but the effect of neuropathy on ankle motor strength in the frontal plane is unknown. METHODS: Subjects' abilities to recover from a lateral lean (with center of gravity offset as percentage of foot width) while standing on one foot, and to rapidly generate inversion torque about the ankle, were quantified. RESULTS: All nine of the young, but only one of six older, control subjects recovered from a 10% lean (P=0.0052). Three of six older controls, but no neuropathy subject, recovered from a 5% lean (P=0.083). Neuropathy subjects demonstrated half the ankle rate of torque development [78.2 (50.8) N m/s; P=0.016] of the young and older controls [162.0 (54.6) and 152.7 (22.2) N m/s, respectively]. CONCLUSIONS: Diabetic neuropathy leads to a decrease in rapidly available ankle strength which impairs balance recovery among older women. Younger women demonstrate similar ankle strength but superior balance recovery compared to older women without neuropathy.

Adult↗

PubMed2007

Gordon Holmes Lecture: Gordon Holmes and the neurological heritage.

Sir Gordon Holmes is one of the great figures in the history of twentienth century neurology. In him, there came together the traditions of German and British neurology which moulded a physiological approach to normal and disordered function of the nervous system with a commitment to interpreting clinical phenomena in the light of meticulous pathological examination. He, more than any other individual, was responsible for the form of the neurological examination as it is now performed; and his insights are fundamental to the way that, nowadays, we think about vision, somato-sensory function, the spinal cord and the cerebellum.

Cerebellum↗

PubMed2000

Intraoperative unmasking of brain redundant motor sites during resection of a precentral angioma: evidence using direct cortical stimulation.

We report the first observation of real-time intraoperative evidence of a retrocentral redistribution of motor areas with an unmasking of precentral redundant motor sites, before and after, respectively, surgical removal of a precentral arteriovenous malformation using direct electrical stimulation. This study shows large-scale plasticity of the motor function behind the central sulcus as the result of an arteriovenous malformation, the brain's ability to effect short-term unmasking of precentral motor sites after arteriovenous malformation resection, and the existence of redundant precentral and postcentral motor areas for the same movement, suggesting that the central sulcus does not simply divide motor and sensory functions.

Adult↗

PubMed1997

Combination leflunomide and cyclosporine prevents rejection of functional whole limb allografts in the rat.

Whole rear limbs were transplanted from Brown Norway or Lewis rat donors to Lewis rat recipients (n=6 per group). One group of allograft recipients was treated with leflunomide (10 mg/kg/24 hr/orally) and cyclosporine (5 mg/kg24 hr/orally) starting 2 days before to surgery. Treatment continued for 60 days or until graft rejection. Untreated allografts were rejected over 6-8 days. After isograft transplantation, weight bearing began by day 17-25 after surgery. Sensory function was restored by 50 days after surgery. All allografts in the drug-treated group survived the 60-day period; survival in this group was significantly longer (P=0.0001) than the untreated controls. Weight bearing began by day 30, but was incomplete in two rats at 60 days. Peroneal nerve function was present in half the rats at 60 days after surgery. Leflunomide combined with cyclosporine prevented whole limb allograft rejection across a major histocompatibility barrier.

Animals↗

PubMed2005

Short-lasting impairment of temperature perception by high frequency rTMS of the sensorimotor cortex.

OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) has become a useful tool for investigating and even modulating human brain function. RTMS of the human motor cortex can produce changes in excitability that outlast the period of stimulation. To investigate the persistent effect of high-frequency rTMS of sensorimotor cortex (SM1) on somatosensory function. METHODS: We evaluated the thermal thresholds (cold and warm sensation) in 14 normal subjects before and after a short train of 5Hz rTMS over the SM1 or occipital cortex (OC). RESULTS: Threshold for cold perception was increased immediately after rTMS of the left SM1 and no effects at all were noticed after OC stimulation. There was a slight, not significant, increase of warm threshold immediately after the rTMS of the left SM1 and no effects at all were noticed after OC stimulation. CONCLUSIONS: High frequency rTMS over primary sensorimotor cortex seems to modulate sensory function related to thermal (cold) perception. SIGNIFICANCE: The method may be useful for both the study of normal human physiology of temperature perception and for rTMS based manipulation of brain plasticity in patients with sensory disturbances.

Adult↗

PubMed2004

The relationship between sensory impairment and functional independence among elderly.

BACKGROUND: It has been well established that increasing age is associated with decreasing functional ability in older adults. It is important to understand the specific factors that affect instrumental activities of daily living (IADL) and functional independence among older adults with sensory disabilities. METHODS: Nationally representative sample of adults aged 55 years and older with seeing or hearing disabilities were categorised into three sensory classifications: "Seeing Disabled but Hearing Abled" (SD-HA), "Hearing Disabled but Seeing Abled" (HD-SA), and both "Seeing and Hearing Disabled" (SD-HD). The additional category of "Seeing Disabled and/or Hearing Disabled" (SD and/or HD) was created to calculate the total of all individuals from the above categories who either had a seeing or hearing disability or both sensory disabilities. Respondents were asked to indicate whether they received assistance in performing seven IADL and their level of functional independence. RESULTS: The most common factors that affect IADL were heavy chores, grocery shopping and housework. Individuals with both seeing and hearing disabilities (SD-HD) reported having the most IADL restrictions, followed by individuals with only seeing disabilities (SD-HA) and only hearing disabilities (HD-SA). Individuals with severe sensory disabilities were generally more likely to report IADL restrictions and less likely to have decision-making control and be happy with their lives. In each sensory classification, females aged 55-64 years and 65 years and older reported more IADL restrictions than males. CONCLUSION: Both seeing and hearing disabilities have a significant impact on restricting an individual's IADL.

Journal Article↗

PubMed2004

The role of functional and perceptual attributes: evidence from picture naming in dementia.

We examined the performance of a group of people with moderately severe Alzheimer's type dementia on a naming task. We found that functional information plays an important role in determining naming performance on both living and non-living things. Perceptual information may play some role in naming living things. We also found some evidence that the semantic category to which an item belongs may also have some effect on naming performance. We argue that both the sensory-functional and domain-specific knowledge hypotheses may be correct: the brain is to some organized on taxonomic grounds, while the semantic representations of living and non-living things depend differentially on perceptual and functional information. These representations can be differentially disrupted by damage to modality-specific stores. At a moderate level of severity, dementia causes global damage that has the effect of disrupting both the localized taxonomic and the modality-specific stores. We discuss the nature of functional information.

Adult↗

PubMed2007

Cortical reorganization following bimanual training and somatosensory stimulation in cervical spinal cord injury: a case report.

BACKGROUND AND PURPOSE: Deficits in upper-extremity function in individuals with tetraplegia are primarily due to the loss of motor pathways. Detrimental cortical reorganization, however, may create further loss of function. The purpose of this case report is to describe the cortical changes associated with a combination intervention using bimanual massed practice training with somatosensory stimulation. CASE DESCRIPTION: "BR" was a 22-year-old man with C6 tetraplegia and hand impairment who participated in this training intervention for 3 weeks. OUTCOMES: BR demonstrated improvements in sensory function, strength (the force-generating capacity of muscle), and performance of functional hand skills. Following the training, the cortical motor map of the biceps brachii muscle shifted anteriorly and increased in area and volume. DISCUSSION: This is the first documented case in which changes in the size and location of the cortical map were associated with an intervention and improvement in function in an individual with tetraplegia. This case suggests that an intensive training intervention may induce both functional and neurophysiological changes.

Adult↗

PubMed2000

Quantitative sensory nerve conduction threshold (sNCT) evaluation of the trigeminal nerve at the mental foramen area.

STATEMENT OF PROBLEM: There is a need for a quick, objective, quantitative sensory test of the mandibular inferior alveolar nerve to assess sensory dysfunction due to trauma, infection, or disease. PURPOSE: This study evaluated the reliability and reproducibility of a commercially available electrodiagnostic quantitative sensory nerve conduction threshold (sNCT) evaluation testing method and established normative values for future evaluation of nerve dysfunction. MATERIAL AND METHODS: Rapid current perception threshold (R-CPT) values were obtained with Neurometer CPT/C, an electrodiagnostic sNCT device that administers an alternating constant-current sinusoid waveform stimulus at either 2000 Hz (H) (Hertz [cycles/second]), 250 Hz (M), or 5 Hz (L) at intensity levels ranging from 0.001 to 10 mA. Thirty-four healthy subjects were tested then retested by the same operator from 7 days to 153 days. R-CPT evaluation was performed over the mental foramen bilaterally with dual disposable gold-plated electrodes and a hypoallergenic electrode gel held in place using nonconductive adhesive tape. Two consecutive identical R-CPT measures were obtained for each stimulation frequency for determination of the final R-CPT value. RESULTS: On the left side, there was no difference between the first and second test (P > .05). On the right side, there was a statistical difference between the first and second test for L, M, and H, but the confidence interval is very narrow and the differences are not clinically significant. CONCLUSION: From the values obtained, R-CPT testing was reliable for the quantification of sensory function in healthy individuals.

Adult↗

PubMed1996

Morphogenesis of the brain in larval and juvenile Japanese eels, Anguilla japonica.

We compared the morphology, including relative volumes (RV), of some brain regions in leptocephalus larvae (10-30 mm in total length), glass eels (elvers), young, and immature pre-adults of the Japanese eel Anguilla japonica. The external brain shape of the leptocephali gradually changes from a laterally compressed one to a depressed elongated one. These changes are fundamentally due to biased growth of the telencephalon and optic tectum. The dramatic brain transformation progresses until the juvenile stage and culminates in an adult-type brain arrangement, with a developed cerebellum and eminentia granularis and a much more flattened appearance. The RVs of brain regions closely related to somatic sensory functions are quite different in larvae and juveniles. The larvae possess larger optic tecta and smaller chemo- and mechanosensory regions than the juveniles. The RV of the olfactory bulb increases, and that of the optic tectum decreases, until the adult stage, unlike the condition in a pelagic fish, Pagrus major, suggesting that adult eels are inferior to pelagic fishes in visual perception. In contrast, the brain morphology of the larvae suggests that they are equipped with a well-developed visual system, while the functional significance of the system still remains a mystery. It might be important for feeding, orientation and diurnal vertical migration of the larvae.

Anguilla↗