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PubMed2006

Characterizing exploration behavior in spatial neglect: omissions and repetitive search.

In search tasks, patients with spatial neglect typically fail to respond to stimuli on the contralesional side. Such behavior has been associated with hyperattention to the ipsilesional side and a deficit in disengaging from attended stimuli. The present study investigated whether such explanations can also account for a further kind of behavior frequently shown by neglect patients: repetitive returns to previously indicated stimuli, particularly on the ipsilesional side. A group of neglect patients was tested along with a group of healthy participants and a patient control group without neglect. Participants performed an exploration task in which they searched for targets defined by their shape or for all stimuli either with the aid of vision or blindfolded. The results showed differential effects of reducing the salience of visual stimuli by blindfolding. For a subgroup of patients, detection rate improved, while for others the percentage of omissions increased. However, contrary to the control groups, blindfolding had no effect on repetitive search in the neglect group, inconsistent with hyperattention, a disengage or impaired working memory deficits. The rate of repetitive returns to previously indicated locations did not seem to be associated with the percentage of omitted stimuli, suggesting that repetitive returns may be best explained by a disruption of systematic search and lack of volitional control in spatial neglect. The results further underline the importance of considering repetitive search behavior in addition to omissions in standard neglect assessments.

Aged↗
PubMed2005

The functional significance of mu rhythms: translating "seeing" and "hearing" into "doing".

Existing evidence indicates that mu and other alpha-like rhythms are independent phenomena because of differences in source generation, sensitivity to sensory events, bilateral coherence, frequency, and power. Although mu suppression and enhancement echo sensorimotor processing in frontoparietal networks, they are also sensitive to cognitive and affective influences and likely reflect more than an idling brain state. Mu rhythms are present at early stages of human development and in other mammalian species. They exhibit adaptive and dynamically changing properties, including frequency acceleration and posterior-to-anterior shifts in focus. Furthermore, individuals can learn to control mu rhythms volitionally in a very short period of time. This raises questions about the mu rhythm's open neural architecture and ability to respond to cognitive, affective, and motor imagery, implying an even greater developmental and functional role than has previously been ascribed to it. Recent studies have suggested that mu rhythms reflect downstream modulation of motor cortex by prefrontal mirror neurons, i.e., cells that may play a critical role in imitation learning and the ability to understand the actions of others. It is proposed that mu rhythms represent an important information processing function that links perception and action-specifically, the transformation of "seeing" and "hearing" into "doing." In a broader context, this transformation function results from an entrainment/gating mechanism in which multiple alpha networks (visual-, auditory-, and somatosensory-centered domains), typically producing rhythmic oscillations in a locally independent manner, become coupled and entrained. A global or 'diffuse and distributed alpha system' comes into existence when these independent sources of alpha become coherently engaged in transforming perception to action.

Animals↗
PubMed2004

Nociceptive EMG suppression in triceps brachii muscle in humans.

OBJECTIVE: Inhibitory spinal reflexes in human hand muscles mediated by cutaneous afferents (=cutaneous silent periods, CSPs) serve to protect the hand from injury. Proximal muscles are included in a complex protective pattern implementing both excitatory and inhibitory reflexes. METHODS: We investigated the functional organization of CSPs in the triceps brachii muscle (TB) - the prime elbow extensor - assessing different stimulus intensities and elbow positions. Thirteen healthy subjects underwent recurrent electrical index finger tip stimulation with different intensities while volitionally activating TB against resistance. The rectified and averaged electromyogram (EMG) was recorded from TB with surface electrodes while the elbow joint was held in full flexion, full extension, and at an angle of 90 degrees. RESULTS: Digit II stimulation resulted in distinct CSPs in TB. Increasing stimulus intensities caused a more profound EMG suppression. Different elbow positions had a significant influence on CSP onset and end latency, and duration. CONCLUSIONS: The present findings are consistent with a functional organization of protective reflexes in the proximal human upper limb across several metameric segments. Spinal inhibitory neurons serving to rapidly suppress basic muscle synergies may compete with neural circuitry involved in postural control.

Adult↗
PubMed2004

EMG for assessing the recovery of voluntary movement after acute spinal cord injury in man.

OBJECTIVE: Multi-channel electromyogram (EMG) was used to examine the pattern and time-course of voluntary contraction recovery in subjects with acute traumatic spinal cord injury (SCI), concentrating on the latest time after injury at which a given muscle would begin to show voluntary recruitment. METHODS: We conducted repeated measures of voluntary contractions of 12 lower limb muscles (for all subjects) and 12 upper-limb muscles (for subjects with cervical injury), beginning within days of the injury and extending for 1 or more years post-injury. The EMG interference pattern was scored in a blinded fashion from tape records. RESULTS: We recruited 229 subjects, including 152 from whom repeated measures were made. Several different patterns of recovery were identified. For persons with motor-incomplete injury to the cervical or thoracic spine, EMG recruitment had not yet occurred by 5 weeks post-injury in roughly 1/2 of all lower limb muscles, and prolonged delays between injury and recruitment onset were sometimes seen. Injury to the thoracolumbar spine was frequently associated with very long delays (i.e. >1 year) between injury and resumption of volitional contraction of distal lower limb muscles. DISCUSSION: The incidence of neurologically incomplete SCI is rising. In such subjects, delays of 1 or more months between injury and the onset of voluntary contraction are common for muscles of the distal upper limbs (for cervical injury) and lower limbs. Given the abbreviated period of in-patient rehabilitation now routine in the United States, these subjects in particular will benefit from frequent follow-up evaluations to assess spontaneous recovery and design appropriate rehabilitation strategies to maximize functional independence. Moreover, the potential for delayed recovery must be considered when designing and implementing novel clinical interventions for treating SCI, to better differentiate between spontaneous and treatment-related improvements in neurologic function.

Acute Disease↗
PubMed2006

What is the Bereitschaftspotential?

Since discovery of the slow negative electroencephalographic (EEG) activity preceding self-initiated movement by Kornhuber and Deecke [Kornhuber HH, Deecke L. Hirnpotentialänderungen bei Willkurbewegungen und passiven Bewegungen des Menschen: Bereitschaftspotential und reafferente Potentiale. Pflugers Archiv 1965;284:1-17], various source localization techniques in normal subjects and epicortical recording in epilepsy patients have disclosed the generator mechanisms of each identifiable component of movement-related cortical potentials (MRCPs) to some extent. The initial slow segment of BP, called 'early BP' in this article, begins about 2 s before the movement onset in the pre-supplementary motor area (pre-SMA) with no site-specificity and in the SMA proper according to the somatotopic organization, and shortly thereafter in the lateral premotor cortex bilaterally with relatively clear somatotopy. About 400 ms before the movement onset, the steeper negative slope, called 'late BP' in this article (also referred to as NS'), occurs in the contralateral primary motor cortex (M1) and lateral premotor cortex with precise somatotopy. These two phases of BP are differentially influenced by various factors, especially by complexity of the movement which enhances only the late BP. Event-related desynchronization (ERD) of beta frequency EEG band before self-initiated movements shows a different temporospatial pattern from that of the BP, suggesting different neuronal mechanisms for the two. BP has been applied for investigating pathophysiology of various movement disorders. Volitional motor inhibition or muscle relaxation is preceded by BP quite similar to that preceding voluntary muscle contraction. Since BP of typical waveforms and temporospatial pattern does not occur before organic involuntary movements, BP is used for detecting the participation of the 'voluntary motor system' in the generation of apparently involuntary movements in patients with psychogenic movement disorders. In view of Libet et al.'s report [Libet B, Gleason CA, Wright EW, Pearl DK. Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain 1983;106:623-642] that the awareness of intention to move occurred much later than the onset of BP, the early BP might reflect, physiologically, slowly increasing cortical excitability and, behaviorally, subconscious readiness for the forthcoming movement. Whether the late BP reflects conscious preparation for intended movement or not remains to be clarified.

Beta Rhythm↗
PubMed2006

Upper extremity muscle activation during recovery of reaching in subjects with post-stroke hemiparesis.

OBJECTIVE: To investigate upper extremity muscle activation and recovery during the first few months after stroke. METHODS: Subjects with hemiparesis following stroke were studied performing a reaching task at an acute time point (mean=9 days post-stroke) and then again at a subacute time point (mean=109 days post-stroke). We recorded kinematics and electromyographic activity of six upper extremity muscles. RESULTS: At the acute time point, the hemiparetic group had delayed muscle onsets, lower modulation ratios, and higher relative levels of muscle activation (%MVIC) during reaching than controls. From the acute to the subacute time points, improvements were noted in all three variables. By the subacute phase, muscle onsets were similar to controls, while modulation ratios remained lower than controls and %MVIC showed a trend toward being greater in the hemiparetic group. Changes in muscle activation were differentially related to changes in reaching performance. CONCLUSIONS: Our data show that improvements in muscle timing and decreases in the relative level of volitional activation may underlie improved reaching performance in the early months after stroke. SIGNIFICANCE: Given that stroke is one of the leading causes of persistent physical disability, it is important to understand how the ability to activate muscles changes during the early phases of recovery after injury.

Adult↗
PubMed2003

The role of primary motor cortex in goal-directed movements: insights from neurophysiological studies on non-human primates.

Neurophysiological studies on non-human primates have provided a large body of information on the response patterns of neurons in primary motor cortex during volitional motor tasks. Rather than finding a single simple pattern of activity in primary motor cortex neurons, these studies illustrate that neural activity in this area reflects many different types of information, including spatial goals, hand motion, joint motion, force output and electromyographic activity. This richness in the response characteristics of neurons makes estimates of any single variable on motor performance from population signals imprecise and prone to errors. It initially seems puzzling that so many different types of information are represented in primary motor cortex. However, such richness in neural responses reflects its important role in converting high-level behavioral goals generated in other cortical regions into complex spatiotemporal patterns to control not only alpha-motoneuron activity but also other features of spinal processing.

Animals↗
PubMed2004

G protein polymorphisms do not predict weight loss and improvement of hypertension in severely obese patients.

Both the gene encoding the alpha subunit of G stimulatory proteins (GNAS1) and the beta3 subunit gene (GNB3) of G proteins are associated with obesity and/or hypertension. Moreover, the TT/TC825 polymorphism of GNB3 predicts greater weight loss than the CC825 polymorphism in obese patients (mean body mass index, 35 kg/m2) undergoing a structured nonpharmacologic weight loss program. Gastric banding enforces a low-calorie diet by diminishing the need for volitional adherence. It is unknown whether these polymorphisms predict the variable weight loss in patients after bariatric surgery. Three hundred and four severely obese patients (mean +/- SEM age, 42 +/- 1 years; 245 women and 59 men; mean +/- SEM body mass index, 43.9 +/- 0.3 kg/m2) followed prospectively for at least 3 years after surgery were genotyped for the GNB3 C825T, G814A, and GNAS1 T393 polymorphisms. All analyses were performed blinded to the phenotypic characteristics of the study group. Frequencies of polymorphisms were comparable to those previously published. No polymorphism studied predicted 3-year weight loss or was associated with high blood pressure in severely obese patients after gastric banding. Multivariate analysis of potentially confounding factors such as reoperation rate or use of sibutramine or orlistat revealed similar results (P > 0.1). Regardless of the mechanism(s) involved for these discordant findings, GNB3 C825T, G814A, and GNAS1 T393C polymorphisms do not seem to be reliable predictors of long-term weight loss.

Adult↗
PubMed2006

Loathing the sinner, medicalizing the sin: why sexually violent predator statutes are unjust.

In seventeen states, persons convicted of one or more sexually violent offenses may be involuntarily civilly committed at the end of their criminal terms if they suffer from a mental disorder that renders them likely to reoffend sexually. These statutes place the burden on states to show that the sex offender meets the United States Constitutional standard of dangerousness. The key to proving dangerousness is proof of a mental disorder. However, the United States Supreme Court recently found that the offender need not be mentally ill. He need only "suffer" from "mental abnormality" or "personality disorder" that affects his cognitive, emotional or volitional capacities such that he is highly likely to sexually reoffend. These statutes are expressions of disgust: a fear of contamination by persons who engage in sexual conduct that forces us to confront our dark impulses. We do not merely hate the sin; we hate the sinner, and we want the sinner to be removed from our presence. Moreover, the emotions these statutes express are the source of widespread moral panic not warranted by data about recidivism risk. Laws that express disgust are likely to result in the unjust treatment of sex offenders.

Commitment of Persons with Psychiatric Disorders↗
PubMed2006

The finite helical axis of the knee joint (a non-invasive in vivo study using fast-PC MRI).

An understanding of the in vivo knee joint kinematics is critical for the further improvement and validation of knee joint models and for the development of better surgical and rehabilitative protocols. Unfortunately, most studies exploring the finite helical axis (FHA) tend to produce excellent qualitative results, but quantitative results are often lacking. Thus, the purpose of this study was to non-invasively and in vivo quantify the tibiofemoral FHA in a relatively large normal population during volitional knee extension using fast-PC MRI, to report the data relative to consistent coordinate systems (making it available for modeling input, experimental comparison and for device design), to determine the variability of the FHA, to investigate the screw home mechanism and to test the hypothesis that knee joint kinematics are independent of gender. Intra- and inter-subject repeatability was excellent. The intra- (inter-) subject repeatability of the FHA orientation in the frontal and axial planes was 1.8% (3.3%) and 3.7% (6.0%) of the average value, respectively. At the beginning of extension, the FHA was directed laterally and slightly superiorly and at the end of extension, it was directed in the lateral-inferior direction, indicative of the screw-home mechanism. The FHA location was not fixed during extension. There was small, but significant differences in all FHA parameters between genders and normalizing positional data relative to epicondylar width helped to reduce this difference. The data obtained in the current study forms an excellent base for future knee joint modeling and clinical studies.

Adult↗
PubMed2004

Residual function in peripheral nerve stumps of amputees: implications for neural control of artificial limbs.

PURPOSE: It is not known whether motor and sensory pathways associated with a missing or denervated limb remain functionally intact over periods of many months or years after amputation or chronic peripheral nerve transection injury. We examined the extent to which activity on chronically severed motor nerve fibers could be controlled by human amputees and whether distally referred tactile and proprioceptive sensations could be induced by stimulation of sensory axons in the nerve stumps. METHODS: Amputees undergoing elective stump procedures were invited to participate in this study. Longitudinal intrafascicular electrodes were threaded percutaneously and implanted in severed nerves of human amputees. The electrodes were interfaced to an amplifier and stimulator system controlled by a laptop computer. Electrophysiologic tests were conducted for 2 consecutive days after recovery from the surgery. RESULTS: It was possible to record volitional motor nerve activity uniquely associated with missing limb movements. Electrical stimulation through the implanted electrodes elicited discrete, unitary, graded sensations of touch, joint movement, and position, referring to the missing limb. CONCLUSIONS: These findings indicate that both central and peripheral motor and somatosensory pathways retain significant residual connectivity and function for many years after limb amputation. This implies that peripheral nerve interfaces could be used to provide amputees with prosthetic limbs that have more natural feel and control than is possible with current myoelectric and body-powered control systems.

Action Potentials↗
PubMed2007

Mild head injury--a close relationship between motor function at 1 week post-injury and overall recovery at 3 and 6 months.

Based on previous findings of impaired eye and arm motor control after mild closed head injury (CHI), this study examined whether early eye and arm motor function, and the level of post-injury cerebral dysfunction manifested in motor control, relates systematically to recovery at 3 and 6 months after mild CHI. At 1 week post-injury, we assessed oculomotor function, upper-limb visuomotor performance, and cognitive status in 37 mild CHI patients. Re-examination at 3 and 6 months determined outcome in terms of postconcussional symptoms and performance of everyday tasks, as assessed by the Rivermead Postconcussion Symptoms Questionnaire, the Rivermead Head Injury Follow-up Questionnaire and the SF-36 Health Survey. We then examined the association of early motor function, cognitive status and self-reported health condition with outcome using linear regression. Motor-based regression models explained a high proportion of the variance in outcome (70-89%), with motor function at 1 week being more closely related to outcome at 3 and 6 months than early psychometric assessment (13-32%) or self-reported health status (54-79%). These motor-based models incorporated subcortical/subconscious motor functions alongside motor functions that are subject to volitional control and are primarily mediated by frontal, parietal and temporal cortical brain regions. Early assessment of eye and arm motor function may help in improving accuracy of outcome prediction after mild CHI. Such assessment may assist in the better targeting of early health care intervention and help decrease head-trauma-related morbidity and rehabilitation costs.

Adolescent↗
PubMed2026

Persistent cloaca without vaginal-common channel fistula: A Case series characterizing a rare phenotype.

INTRODUCTION: Persistent cloaca occurs in approximately 1 in 25,000 live births. Among patients with cloaca, the absence of a vaginal connection to the common channel represents a rare phenotype with distinct anatomic and management considerations. We describe the urologic, gynecologic, and surgical characteristics of this patient subset. METHODS: We performed a retrospective analysis of a single-institution cohort of patients with persistent cloaca managed at a quaternary-care children's hospital between 2019 and 2025. Patients were eligible if they underwent primary cloacal repair by our multidisciplinary team and met all three diagnostic criteria for absent vaginal-common channel fistula: no hydrocolpos on imaging, no identified vaginal opening on cystoscopy or cloacagram, and no visible lumen between müllerian and cloacal structures identified intraoperatively. RESULTS: Of 51 patients who underwent primary repair, 6 (12%) met criteria for absent vaginal-common channel fistula. All met criteria for VACTEGRLS association. Common channel length ranged from 1.1 to 7.0 cm and urethral length from 0.5 to 2.2 cm. Urologic anomalies were nearly universal: five patients (83%) had a solitary functional kidney and four (67%) had vesicoureteral reflux. All underwent posterior sagittal anorectoplasty (PSARP) for rectal repair with the common channel repurposed as the neourethra. Five (83%) underwent diagnostic laparoscopy during which the müllerian structures were examined but left in situ. At last follow-up (median 17.5 months, range 4-35 months), three patients (50%) had volitional voiding and three (50%) required assisted bladder emptying via vesicostomy or Mitrofanoff. CONCLUSION: Persistent cloaca without a vaginal-common channel fistula represents a rare but clinically distinct phenotype characterized by severe urologic anomalies. Recognition of this phenotype is essential for surgical planning and long-term urologic and gynecologic surveillance. Because there was no connection between the vagina and the urinary tract, delaying management of the müllerian structures did not adversely affect the urinary tract.

Humans↗
PubMed2006

Long-term followup of patients after redo bladder neck reconstruction for bladder exstrophy complex.

PURPOSE: The aim of this study was to determine whether redo bladder neck reconstruction is effective in achieving continence after a failed bladder neck reconstruction procedure. MATERIALS AND METHODS: We retrospectively reviewed the hospital records of patients with bladder exstrophy who had undergone redo bladder neck reconstruction. There were 30 patients in the study, including 20 boys and 10 girls. Mean patient age at redo bladder neck reconstruction was 9.3 years (range 3.2 to 15.5). The patients were divided into 3 groups on the basis of the preoperative pattern of incontinence--incomplete wetters, complete wetters and those on continuous suprapubic drainage. Of the patients 15 already had undergone bladder augmentation, 12 had undergone a Mitrofanoff procedure and 12 had been treated with bulking agents injected in the bladder neck in an attempt to achieve continence. Four patients had undergone more than 1 bladder neck procedure. The patients were investigated with a combination of noninvasive urodynamics, cystoscopy, cystogram and ultrasound. All patients underwent Mitchell's modification of Young-Dees-Leadbetter bladder neck reconstruction. Additional procedures performed included augmentation cystoplasty and Mitrofanoff formation. RESULTS: Mean followup was 6.9 years (range 1.2 to 15.5). Postoperatively 28 patients were using clean intermittent catheterization to empty the bladder (5 per urethra, 23 via Mitrofanoff). Two patients remained on continuous suprapubic catheter drainage. A total of 18 patients (60%) were dry postoperatively (80% of girls and 50% of boys). Among dry patients only 3 were performing clean intermittent catheterization per urethra and 15 via a Mitrofanoff channel. No patient was able to void per urethra without the need for clean intermittent catheterization. The 2 patients on continuous suprapubic catheter drainage continued to remain so. At night only 50% of the patients were dry (5 on free drainage, 4 on clean intermittent catheterization, 6 not on any drainage). Those patients who did not respond satisfactorily to redo bladder neck reconstruction underwent subsequent additional procedures, which included injection of bulking agents (3 patients), insertion of an artificial urinary sphincter (1), Mitrofanoff formation (2) and bladder augmentation plus Mitrofanoff channel (1). Postoperative complications included difficulty with clean intermittent catheterization (8 patients), perivesical leak (1), recurrent epididymo-orchitis (1), upper urinary tract dilatation (2) and incisional hernia (1). Bladder neck closure was being considered in 5 patients. CONCLUSIONS: In our experience redo bladder neck reconstruction cannot achieve continence with volitional voiding per urethra. Although redo bladder neck reconstruction can render a significant number of patients dry, it is only effective if performed in conjunction with augmentation. Failure of the initial bladder neck reconstruction may be a reflection of a bladder that is of inadequate capacity and/or compliance. Therefore, bladder augmentation should be considered in all patients requiring redo bladder neck reconstruction. Bladder neck closure may be a better alternative to redo bladder neck reconstruction.

Adolescent↗
PubMed2007

Rehabilitative ultrasound measurement of select trunk muscle activation during induced pain.

Rehabilitative ultrasound imaging (RUSI) is considered a valid method to measure muscle activation in key spinal muscles in asymptomatic subjects. Research measuring muscle activation with RUSI in painful subjects is limited. The aim of this study was to determine if changes in muscle activation from experimentally induced pain can be measured by RUSI. Six male subjects performed tasks known to activate the transverse abdominis (TrA) and lumbar multifidus (LM) while RUSI measurements of muscle thickness were obtained during control and hypertonic saline conditions. The abdominal draw-in maneuver was used to volitionally activate the TrA and a series of upper extremity lifting tasks were used to automatically activate the LM. Pain was induced by injecting 5% hypertonic saline into the longissimus muscle adjacent to the LM at the L4 level. The percent change in muscle thickness from rest to contraction represented muscle activation. Activation was significantly less (p<0.01) during the painful condition on 4 of the 5 tasks performed for the LM and on the task performed for the TrA. These results indicate that RUSI can be used to measure pain-related changes in deep trunk muscle activation. Future research should include a larger sample size and women.

Abdominal Muscles↗
PubMed2006

A comparative study of the effect of food consumption on labour and birth outcomes in Australia.

OBJECTIVE: to explore the effect of volitional food consumption by women during labour on labour and birth outcomes. DESIGN: a comparative design using concurrent controls. SETTING: four public hospitals in Sydney, Australia. PARTICIPANTS: 217 English-speaking, nulliparous women with low-risk pregnancies. The sample was divided into four sub-groups identified post hoc from reported behaviour: (1) 82 women who chose to eat food during early labour only; (2) 10 who ate during established labour only; (3) 31 who ate during early and established labour and (4) 94 who chose to consume clear fluids only during early and established labour. INTERVENTIONS: voluntarily eating food during labour compared with voluntarily consuming clear fluids only. MEASUREMENTS: differences between the four eating groups were examined for labour progress using one-way analysis of variance (ANOVA). A hierarchical multiple regression tested the association between eating during labour and labour duration. The relationship between food intake and the incidence of medical interventions was tested using chi(2) tests. FINDINGS: eating during the early phase of the first stage of labour was associated with M=2.16 hrs longer labour (p<0.01). When women ate food during both their early and established phases of labour, M=3.5 hrs was added to their labour (p<0.01). The incidence of vomiting, medical interventions during labour or adverse birth outcomes were unaffected by food intake. CONCLUSION: the findings suggest that women should be informed that labour may take longer when they eat food. However, eating does not seem to affect other labour or birth outcomes. IMPLICATION FOR PRACTICE: the findings challenge the belief among many midwives that food intake is beneficial to labour progress. However, women should not be denied food for fear of vomiting or because it may make labour longer. Women with low-risk labours should be informed of the risk, although rare, of aspiration if general anaesthesia is required, and be allowed to respond to their natural desires for oral intake during labour.

Adult↗
PubMed2004

Role of basal ganglia-brainstem pathways in the control of motor behaviors.

Here we review a role of a basal ganglia-brainstem (BG-BS) system throughout the mesopontine tegmentum in the control of various types of behavioral expression. First the basal ganglia-brainstem system may contribute to an automatic control of movements, such as rhythmic limb movements and adjustment of postural muscle tone during locomotion, which occurs in conjunction with voluntary control processes. Second, the basal ganglia-brainstem system can be involved in the regulation of awake-sleep states. We further propose the possibility that the basal ganglia-brainstem system is responsible for the integration of volitionally-guided and emotionally-triggered expression of motor behaviors. It can be proposed that dysfunction of the basal ganglia-brainstem system together with that of cortico-basal ganglia loop underlies the pathogenesis of behavioral disturbances expressed in basal ganglia dysfunction.

Basal Ganglia↗
PubMed2006

Effects of age on latency and error generation in internally mediated saccades.

Most studies on the effects of ageing on saccades have examined reflexive saccades; the only commonly studied volitional task has been the antisaccade task, with contradictory results. We examined in both young and elderly normal subjects the latency of anti-, memory-guided, and predictable saccades and the timing of self-paced saccades; we also evaluated errors made on the first two tasks. We expected errors to be correlated between tasks; we also expected antisaccade latencies and errors to be inversely correlated. We also expected antisaccade and memory-guided saccade latencies to be longer in individuals with a high self-paced rate. Except for predictable saccades, mean latencies were significantly higher in the elderly. However, their performance was more variable. Errors were also significantly more frequent on anti- and memory-guided saccade tasks. Most of the hypothesised correlations were not observed. Analysis of error latencies showed that whilst most antisaccade errors were reflexive, for memory-guided saccades both express errors and errors with latencies between 0.4 and 2.5 s were observed. The latter appeared to be a premature release of what would otherwise have been a properly planned response. Age thus impaired all but the predictable saccade task; nevertheless, there were few relationships between measures across tasks. This suggests that a range of processes mediate peoples' performance on these saccade paradigms.

Adolescent↗