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At least 1,243 records · Page 69Linked to original sources

PubMed2006

Robot-assisted thoracoscopic esophagectomy with the patient in the prone position.

We describe a new technique of esophagectomy by robot-assisted thoracoscopy with the patient in the prone position, followed by laparoscopy and left cervicotomy with the patient in the supine position. We report two procedures performed November 2002 and September 2003. The technique should allow more thorough lymph node removal while reducing postoperative pain and morbidity. The thoracoscopy is robot-assisted and the articulations within the pleural cavity improve the surgeon's dexterity and reduce trocar movements. The prone position allows mobilization of the esophagus with only three trocars because the lung, which is partially deflated, does not block access. With the patient in the prone position, bleeding does not obscure the operative field. Stomach mobilization, gastric tube creation, and celiac lymphadenectomy are performed by laparoscopy. The esogastric anastomosis is a totally mechanical side-to-side anastomosis realized by left cervicotomy.

Carcinoma, Squamous Cell↗

PubMed2005

A unilateral section of the corticospinal tract at cervical level in primate does not lead to measurable cell loss in motor cortex.

The effects of a unilateral interruption of the dorsolateral funiculus at cervical level on the survival of neurons in the motor cortex were investigated in macaque monkeys. The lesion was made on the left side at the transition region between the 7(th) and 8(th) cervical segments, above the motoneurons controlling hand muscles. As a result, the homolateral hand became paretic, although an incomplete recovery of manual dexterity took place during 2 months post-lesion. A quantitative anatomical assessment of pyramidal neurons in layer V was performed in the hindlimb area of the primary motor cortex and in the supplementary motor area (SMA proper). The pyramidal neurons were visualized using the marker SMI-32 and thus included the subpopulation of corticospinal neurons. These quantitative data demonstrated that the vast majority of the axotomized corticospinal (CS) neurons did not degenerate. Rather, their somata shrank, compared to the opposite hemisphere or to intact monkeys. This conclusion is in contrast to some previous studies in monkeys that argued for a substantial degeneration of motor cortex neurons as a result of transection of the corticospinal tract; yet in agreement with others that concluded the survival of most CS neurons. The survival of the majority of CS axotomized neurons is also consistent with the observation of numerous CS axons 1 mm above the cervical hemisection.

Animals↗

PubMed2000

Dark adaptation, motor skills, docosahexaenoic acid, and dyslexia.

Dyslexia is a widespread condition characterized by difficulty with learning and movement skills. It is frequently comorbid with dyspraxia (developmental coordination disorder), the chief characteristic of which is impaired movement skills, indicating that there may be some common biological basis to the conditions. Visual and central processing deficits have been found. The long-chain polyunsaturated fatty acids (LCPUFAs) are important components of retinal and brain membranes. In the preliminary studies reported here, dark adaptation was shown to be impaired in 10 dyslexic young adults when compared with a similar control group (P < 0.05, repeated-measures analysis of variance); dark adaptation improved in 5 dyslexia patients after supplementation with a docosahexaenoic acid (DHA)-rich fish oil for 1 mo (P < 0.05, paired t test on final rod threshold); and movement skills in a group of 15 dyspraxic children improved after 4 mo of supplementation with a mixture of high-DHA fish oil, evening primrose oil, and thyme oil (P < 0.007 for manual dexterity, P < 0.02 for ball skills, and P < 0.03 for static and dynamic balance; paired t tests). The studies were small and had designs that did not allow firm conclusions to be made. However, when considered with other evidence from another closely related condition, attention-deficit hyperactivity disorder, for which reduced ability to elongate and desaturate the essential fatty acids linoleic acid and alpha-linolenic acid to arachidonic acid and DHA, respectively, has been proposed, the studies suggest that more research, including double-blind, placebo-controlled studies, would be useful to clarify the benefits of LCPUFAs in dyslexia and other closely related conditions.

Apraxias↗

PubMed1989

Fine-needle aspiration by vacuum tubes.

Fine-needle aspiration of subcutaneous masses, accepted in many parts of Europe and the Americas as a routine diagnostic technique, employs a syringe holder to facilitate the creation of a vacuum to withdraw cells. This investigation demonstrates that a vacuum tube used in venipuncture can be used to supply the negative pressure to suck cells into the needle. This apparatus is more readily available than a syringe holder in hospitals and clinics, and particularly provides the operator with a more dexterous approach to the mass because the fingers holding the needle can be much closer to the mass being immobilized by the other hand.

Biopsy, Needle↗

PubMed2001

Associations of blood lead, dimercaptosuccinic acid-chelatable lead, and tibia lead with neurobehavioral test scores in South Korean lead workers.

The authors performed a cross-sectional study to evaluate associations between blood lead, tibia lead, and dimercaptosuccinic acid (DMSA)-chelatable lead and measures of neurobehavioral and peripheral nervous system function among 803 lead-exposed workers and 135 unexposed controls in South Korea. The workers and controls were enrolled in the study between October 1997 and August 1999. Central nervous system function was assessed with a modified version of the World Health Organization Neurobehavioral Core Test Battery. Peripheral nervous system function was assessed by measuring pinch and grip strength and peripheral vibration thresholds. After adjustment for covariates, the signs of the beta coefficients for blood lead were negative for 16 of the 19 tests and blood lead was a significant predictor of worse performance on eight tests. On average, for the eight tests that were significantly associated with blood lead levels, an increase in blood lead of 5 microg/dl was equivalent to an increase of 1.05 years in age. In contrast, after adjustment for covariates, tibia lead level was not associated with neurobehavioral test scores. Associations with DMSA-chelatable lead were similar to those for blood lead. In these currently exposed workers, blood lead was a better predictor of neurobehavioral performance than was tibia or DMSA-chelatable lead, mainly in the domains of executive abilities, manual dexterity, and peripheral motor strength.

Adult↗

PubMed2004

Association of medication adherence, knowledge, and skills with emergency department visits by adults 50 years or older with congestive heart failure.

PURPOSE: The association of medication adherence, knowledge, and skills with emergency department (ED) visits by patients 50 years of age or older with congestive heart failure (CHF) was studied. METHODS: The patients in this study were enrolled in the usual care group of an ongoing trial of patients with CHF to determine the effects of a pharmacy-based intervention on relevant outcomes. Participants' medication knowledge and skills were assessed during individual interviews. Medication knowledge assessed patients' knowledge of the dosage, frequency, and indication of each of their CHF medications. The medications skills assessment evaluated patients' dexterity (ability to open medication bottles), literacy (ability to read labels), and ability to distinguish colors of tablets and capsules. Medication adherence to CHF drugs was calculated from electronic monitors and prescription-refill records over a six-month period. The primary outcomes of this study were the numbers of all-cause cardiovascular and CHF-specific ED visits during a six-month period. Log-linear regression models were used to analyze the effects of medication knowledge, skill, and adherence on ED visits. RESULTS: Sixty-one patients participated in this study. Multivariate log-linear models adjusted for demographic variables showed that lower medication adherence (p < 0.001) and an inability to read standard prescription and auxiliary labels (p = 0.002) were associated with an increased number of cardiovascular-related ED visits. Knowledge of the prescribed dose was associated with CHF-specific ED visits (p < 0.001). CONCLUSION: Greater medication knowledge, skills, and adherence were associated with fewer ED visits among patients 50 years of age or older with CHF in an urban, teaching medical center.

Adult↗

PubMed2002

Clustered encouragement designs with individual noncompliance: bayesian inference with randomization, and application to advance directive forms.

In many studies comparing a new 'target treatment' with a control target treatment, the received treatment does not always agree with assigned treatment-that is, the compliance is imperfect. An obvious example arises when ethical or practical constraints prevent even the randomized assignment of receipt of the new target treatment but allow the randomized assignment of the encouragement to receive this treatment. In fact, many randomized experiments where compliance is not enforced by the experimenter (e.g. with non-blinded assignment) may be more accurately thought of as randomized encouragement designs. Moreover, often the assignment of encouragement is at the level of clusters (e.g. doctors) where the compliance with the assignment varies across the units (e.g. patients) within clusters. We refer to such studies as 'clustered encouragement designs' (CEDs) and they arise relatively frequently (e.g. Sommer and Zeger, 1991; McDonald et al., 1992; Dexter et al., 1998) Here, we propose Bayesian methodology for causal inference for the effect of the new target treatment versus the control target treatment in the randomized CED with all-or-none compliance at the unit level, which generalizes the approach of Hirano et al. (2000) in important and surprisingly subtle ways, to account for the clustering, which is necessary for statistical validity. We illustrate our methods using data from a recent study exploring the role of physician consulting in increasing patients' completion of Advance Directive forms.

Journal Article↗

PubMed1989

Comparison of diazepam with midazolam as i.v. sedation for outpatient gastroscopy.

We studied 26 patients in a double-blind investigation to compare psychomotor and cognitive recovery for 30 h after sedation for day-case gastroscopy with i.v. diazepam 0.15 mg kg-1 or midazolam 0.07 mg kg-1. Significantly more patients reported side effects at 7, 10 and 30 h post-gastroscopy after diazepam than after midazolam (P less than 0.05). Compared with baseline, the midazolam group was significantly impaired in critical flicker fusion threshold, reaction time, dexterity and visualization tasks up to 4 h after administration (P less than 0.05). There was a significant association between midazolam and amnesia for the procedure (P less than 0.001).

Adult↗

PubMed1993

The role of premotor cortex and the supplementary motor area in the temporal control of movement in man.

In the present study temporal control of movement was systematically analysed in patients with unilateral lesions of the lateral or medial premotor cortex (PMC) or supplementary motor area (SMA) and in age-matched controls. The ability to learn new temporal adjustments was evaluated by examining rhythm reproduction using either the left or right hand or both hands in an alternating manner. A severe impairment in rhythm reproduction was found after lateral or medial PMC lesions; the deficit was most pronounced when our patients were required to use both hands in an alternating manner. The impairment occurred in the absence of difficulties in manual dexterity or impairments in discriminating the rhythm patterns. In a second series of experiments the contribution of the SMA in organizing movements in the time domain was examined. In this series, two patients with left-sided lesions, including the SMA but sparing tissue from the lateral hemispheric surface, and seven age-matched controls were requested to reproduce rhythm constellations in the presence of a sound signal and from memory. Results reveal that patients with left medial lesions involving the SMA had most severe difficulties to produce any rhythms from memory, though they were able to produce the rhythms under auditory pacing. This deficit in programming sequential patterns from memory in the time domain should be interpreted in the context of a decline in the ability to benefit from previous stimulus presentation, which prevents an effective later programming of these sequences when they have to be rehearsed from memory. It was found that patients with left SMA lesions had an increase in reaction time on a sequential digit task when sequences had to be produced under delayed conditions; by contrast, the controls showed a decrease of reaction time after previous stimulus presentation. The present findings extend previous knowledge on sequential motor tasks and argue for a critical role for both the SMA and the premotor cortex in the generation of sequences from memory that fit into a precise timing plan.

Adult↗

PubMed1993

Longitudinal study of central motor conduction time following stroke. 2. Central motor conduction measured within 72 h after stroke as a predictor of functional outcome at 12 months.

A longitudinal study was performed on 118 first-ever stroke patients to evaluate neurophysiological measurements of central motor conduction time (CMCT) in the period immediately following stroke as predictors of functional outcome and mortality at 12 months. Measurements of CMCT were made as described in the accompanying article (Heald et al., 1993, Brain, 116, 1355-1370), in which the following three groups of patients were recognized within 12-72 h after the onset of symptoms: normal response group, delayed response group and no response group. Neurophysiological and clinical investigations were commenced 12-72 h (designated as day 1) after the onset of symptoms and repeated at set time intervals up to 12 months. The subjects were examined neurologically and assessed using the Motricity Index for muscle strength, the Nine-hole Peg Test to measure manual dexterity, the Barthel Score for activities of daily living and the modified Rankin Scale for functional outcome. The duration of stay in hospital and the occurrence of stroke-related death were noted. During the first week following stroke, absence of responses correlated closely with the patient's symptoms and neurological observations of abnormal muscle tone and tendon reflexes. Correlations were made in the three groups of patients of functional scores at day 1 and at 12 months. Patients with normal CMCT had consistently higher scores throughout the 12 month period and achieved significantly better functional recovery. Patients with no responses showed poor performance in neurological and functional tests throughout the 12 month period. Patients with delayed CMCT had neurological and functional scores intermediate between those of the other two groups, but outcome at 12 months was similar to those in the normal response group. Where the threshold to cortical stimulation was abnormally high, functional outcome was generally poor. Mortality was highest in the group with absent responses and the survivors spent the longest period in hospital. In conclusion, the observation of normal or delayed CMCT at day 1 identifies a group of patients with a high probability of survival and functional recovery. The absence of responses to cortical stimulation at day 1 identifies a group of patients who are at high risk of poor functional recovery at 12 months and greater probability of stroke-related death during this period.

Cerebrovascular Disorders↗

PubMed1999

Muscle spindle activity in the affected upper limb after a unilateral stroke.

Weakness, loss of dexterity and exaggerated reflex responses to proprioceptive and cutaneous stimuli are typical features of hemiparetic stroke. Since the extent to which altered fusimotor drive contributes to these deficits has not been established, this study was designed to assess fusimotor function in stroke patients by comparing three aspects of muscle spindle afferent behaviour (background discharge rate, responses to reflex inputs and responses to voluntary contractions) in 11 subjects affected by recent cerebrovascular lesions, with those in 18 healthy volunteers. The mean background discharge rates of muscle spindle afferents in the radial nerve when subjects attempted to relax the recorded limb completely were 6.6 +/- 5.3 Hz (n = 26) in patients and 6.4 +/- 6.1 Hz (n = 76) in control subjects. The variability of discharge rate of active afferents was also similar (0.12 +/- 0.07 and 0.09 +/- 0. 10, respectively). Reflex activation of fusimotor neurons was assessed using trains of electrical stimuli to the superficial radial nerve or to the palm of the hand, and using natural skin stimuli. Neither type of cutaneous stimulation affected muscle spindle afferent discharge in the absence of an EMG response. During deliberate voluntary contractions muscle spindle discharge rates were enhanced similarly in both the control and patient groups, indicating that volitional drives could access fusimotor neurons in the patients. Qualitatively, spindle behaviour was similar in patients and control subjects. These findings suggest that fusimotor function is not disturbed any more or less than skeletomotor function in hemiparetic patients and it is concluded that fusimotor dysfunction probably contributes little to their deficit.

Acoustic Stimulation↗

PubMed1999

The role of ventral medial wall motor areas in bimanual co-ordination. A combined lesion and activation study.

Two patients with midline tumours and disturbances of bimanual co-ordination as the presenting symptoms were examined. Both reported difficulties whenever the two hands had to act together simultaneously, whereas they had no problems with unimanual dexterity or the use of both hands sequentially. In the first patient the lesion was confined to the cingulate gyrus; in the second it also invaded the corpus callosum and the supplementary motor area. Kinematic analysis of bimanual in-phase and anti-phase movements revealed an impairment of both the temporal adjustment between the hands and the independence of movements between the two hands. A functional imaging study in six volunteers, who performed the same bimanual in-phase and anti-phase tasks, showed strong activations of midline areas including the cingulate and ventral supplementary motor area. The prominent activation of the ventral medial wall motor areas in the volunteers in conjunction with the bimanual co-ordination disorder in the two patients with lesions compromising their function is evidence for their pivotal role in bimanual co-ordination.

Adult↗

PubMed2001

Tactile apraxia: unimodal apractic disorder of tactile object exploration associated with parietal lobe lesions.

Tactile apraxia is characterized by an isolated disturbance of hand movements for use of and interaction with an object (transitive movements) in the presence of preserved intransitive movements (movements without use of an object, for example repetitive movements or gestures). It is, however, still unclear whether motor and sensory abnormalities represent causal or associated features of tactile apraxia. To address this question, quantitative kinematic recordings of exploratory finger movements (transitive movements) and rapid alternating finger movements (intransitive movements) were studied in 20 healthy volunteers and 22 patients with focal lesions of the parietal, anterofrontal and motor cortex. The most severe deficits of manual object exploration were found in patients with parietal lesions, using the hand contralateral to the lesion. Patients with lesions of the anterior parietal lobe who exhibited prominent sensory deficits and astereognosia showed a decrease in frequency and regularity of exploratory finger movements and a marked increase in exploration space. Patients with posterior parietal lesions exhibiting severe astereognosia, apraxia and deficits in dexterity had a greater decrease in frequency and regularity of manipulative movements, but a less pronounced increase of exploration space than the patients with anterior parietal lesions. Although the patients with parietal lobe lesions could generate rapid alternating finger movements, the regularity of these movements was also impaired. In comparison, patients with frontal lobe lesions exhibited impaired contralesional manipulatory and rapid alternating finger movements but no sensory abnormalities or astereognosia. We conclude that tactile apraxia represents a deficit in the programming of exploratory finger movements mediated by the parietal lobe. The comparison with lesions of other regions participating in the cortical network for tactile exploration reveals that apraxia of exploratory movements in parietal lobe lesions represents a disturbance distinct from elementary motor or sensory abnormalities, but closely related to stereognostic functioning.

Adolescent↗

PubMed2005

Apraxia in movement disorders.

The definition of apraxia specifies that the disturbance of performed skilled movements cannot be explained by the more elemental motor disorders typical of patients with movement disorders. Generally this does not present a significant diagnostic problem when dealing with 'higher-level' praxic disturbances (e.g. ideational apraxia), but it can be a major confound in establishing the presence of limb-kinetic apraxia. Most motor disturbances characteristic of extrapyramidal disorders, particularly bradykinesia and dystonia, will compromise the ability to establish the presence of loss of dexterity and deftness that constitutes this subtype. The term 'apraxia' has also been applied to other motor disturbances, such as 'gait apraxia' and 'apraxia of eyelid opening', that perhaps are misnomers, demonstrating the lack of a coherent nomenclature in this field. Apraxia is a hallmark of corticobasal degeneration (CBD) and historically this has received the most attention among the movement disorders. Corticobasal degeneration is characterized by various forms of apraxia affecting limb function, particularly ideomotor apraxia and limb-kinetic apraxia, although buccofacial and oculomotor apraxia can be present as well. The syndrome of parkinsonism and prominent apraxia, designated the 'corticobasal syndrome' (CBS), may be caused by a variety of other central nervous system pathologies including progressive supranuclear palsy (PSP), Alzheimer's disease, dementia with Lewy bodies and frontotemporal dementias. Distinct from the CBS, PSP and Parkinson's disease can demonstrate varying degrees of apraxia on selected tests, especially in those patients with more severe cognitive dysfunction. Diseases that cause the combination of apraxia and a primary movement disorder most often involve a variety of cerebral cortical sites as well as basal ganglia structures. Clinical-pathological correlates and functional imaging studies are compromised by both this diffuse involvement and the confusion experienced in the clinical evaluation of apraxia in the face of the additional elemental movement disorders. Finally, although apraxia results in clear disability in patients with the CBS, it is not clear how milder ideomotor apraxia found on specific testing contributes to patients' overall day-to-day motor disability.

Alzheimer Disease↗

PubMed2005

MTI of white matter hyperintensities.

The severity of tissue changes associated with incidental white matter hyperintensities (WMH) in the elderly cannot be sufficiently determined by conventional MRI. We, therefore, performed a regional analysis of the magnetization transfer ratio (MTR) maps obtained on a 1.5 T scanner from 198 neurologically asymptomatic participants of the Austrian Stroke Prevention Study (mean age 70, age range 52-87 years) in regard to WMH and predefined areas of normal appearing brain tissue. Fluid attenuated inversion recovery MRI was used to grade lesion severity and for lesion volume measurements. The MTR of WMH was always significantly lower than that of normal appearing white matter (NAWM) with an overall relative reduction of approximately 10% and decreased significantly with increasing scores of WMH severity (P = 0.02) and WMH volume (r = -0.24, P = 0.0016). NAWM MTR was not different between subjects with very few and extensive WMH and the WMH volume was associated with NAWM MTR of the frontal lobes only. Concerning a possible impact on cerebral functioning the MTR of the frontal NAWM was significantly associated with fine motor dexterity (P = 0.04) but not with cognitive performance. A significant decline of the MTR with aging was seen in both NAWM and cortex but not in WMH. We conclude that MTR measurements can serve to quantify WMH associated tissue damage. It is predominantly focal, relatively mild, increases with lesion size and may have remote effects on the frontal white matter.

Aged↗

PubMed2005

Performance of locomotion and foot grasping following a unilateral thoracic corticospinal tract lesion in monkeys (Macaca mulatta).

Six adult monkeys (Macaca mulatta) received a unilateral lesion of the lateral corticospinal tract (CST) in the thoracic spinal cord. Prior to surgery, the animals were trained to perform quadrupedal stepping on a treadmill, and item retrieval with the foot. Whole body kinematics and electromyogram (EMG) recordings were made prior to, and at regular intervals over a period of 12 weeks after the CST lesion. After 1 week of recovery, all monkeys were able to walk unaided quadrupedally on the treadmill. The animals, however, dragged the hindpaw ipsilateral to the lesion along the treadmill belt during the swing phase and showed a significant reorganization of the spatiotemporal pattern of hindlimb (HL) and forelimb (FL) displacements. The inability to appropriately trigger the swing phase resulted in an increase in the cycle duration and stride length of both HLs. The stance duration decreased in the ipsilateral HL, and increased in the contralateral HL and both FLs. Consequently, there was a dramatic disruption of interlimb and intralimb coupling that was reflected in the limb kinematic and EMG patterns. The CST lesion completely abolished the ability of the monkeys to retrieve items with the foot ipsilateral to the lesion and significantly disrupted the level of performance of the contralateral HL during the first 2 weeks post-lesion. Interestingly, selected HL muscles remained almost quiescent when the monkeys attempted to retrieve items, but were unsuccessful with the affected foot at 1 week post-lesion, whereas the capacity to activate the same muscles was preserved, although reduced, during stepping. Spatial and temporal parameters of gait, kinematics, and EMG patterns recorded during locomotion generally converged toward control values over time, but significant differences persisted up to 12 weeks post-lesion. Although some control was recovered over the distal foot musculature, fine foot grasping remained significantly impaired at the end of the testing period. These findings demonstrate that the CST pathway from the brain normally makes an important contribution to interlimb and intralimb coordination during basic locomotion, and to muscle activation to produce dexterous foot digit movements in the monkey. Furthermore, the present study indicates that the primate has the ability to rapidly accommodate locomotor performance, and to a lesser degree fine foot motor skills, to a reduction in supraspinal control. Identification of the neural substrates mediating the rapid recovery of motor function following injury to the primate spinal cord could provide insight into developing repair strategies to augment functional recovery from neuromotor impairments.

Animals↗

PubMed2006

Mecp2 deficiency is associated with learning and cognitive deficits and altered gene activity in the hippocampal region of mice.

Rett syndrome (RTT) is a debilitating neurological condition associated with mutations in the X-linked MECP2 gene, where apparently normal development is seen prior to the onset of cognitive and motor deterioration at 6-18 months of life. A targeted deletion of the methyl-CpG-binding domain (MBD) coding region and disruption of mRNA splicing was introduced in the mouse, resulting in a complete loss of Mecp2 transcripts and protein. Postnatal comparison of XO and XY mutant Mecp2 allele-containing null mice revealed similar effects on mouse growth and viability, suggesting that phenotypic manifestations are not modulated by the Y-chromosome. Further assessment of Mecp2-null XY mice highlighted cerebellar and hippocampal/amygdala-based learning deficits in addition to reduced motor dexterity and decreased anxiety levels. Brain tissues containing the hippocampal formation of XY Mecp2-null mice also displayed significant changes in genetic activity, which are related to the severity of the mutant phenotype.

Animals↗

PubMedDate not supplied

Postnatal maturation of the direct corticospinal projections in the macaque monkey.

Postnatal changes in the topography of the multiple corticospinal projections in the macaque monkey were followed using retrogradely transported fluorescent tracers, and related to the monkey's acquisition of manual dexterity; both behavioral and anatomical maturation were completed by about 8 postnatal months. Cortical origins of the corticospinal projections were examined by constructing planar projection maps of the distributions of labeled corticospinal neuron somas; these somas were found only in lamina V. At birth elaborate somatotopically organized corticospinal projections from primary motor cortex (area 4), the mesial supplementary motor area and cingulate areas 23 and 24, area 12, dorsolateral area 6a beta, the dorsolateral and ventral area 6a alpha (area F4), parietal areas 2/5, 7b and the peri-insular cortex (including area SII), were clearly defined, with axons extending to all spinal cord segments. While this pattern of regional projections broadly resembled that of the mature macaque, there were, however, substantial maturational changes during the 8 months after birth. These included (1) a halving of the area of cerebral cortex from which the contralateral corticospinal projection originated and (2) a threefold reduction in the number of labeled corticospinal neurons projecting to all segments of the cord. Collateral elimination rather than neuronal cell death was the likely mechanism for this reduction in the population and areal extent of corticospinal neurons in the maturing macaque. The surviving corticospinal axon terminals also developed substantially during the postnatal period. At birth some terminals had invaded the intermediate zone in each spinal segment, but few had penetrated the dorsal and ventral horns. By 6 postnatal months, however, many corticospinal neurons were retrogradely labeled following the injection of fluorescent labels into each of these spinal zones in cervical and lumbar spinal segments. These data demonstrate a considerable postnatal reduction in corticospinal neurons projecting to the contralateral spinal cord, and imply that many of the axons that are eliminated never synapse on spinal neurons. It is suggested that during the middle fetal period the axons of many of the cortical neurons in lamina V that in the mature monkey will terminate on particular neuron populations in the thalamus, brainstem, or spinal cord, traverse a common pathway down through the internal capsule into the spinal cord, passing close to these successive targets, and possibly forming collaterals at these levels. In the postnatal period each such neuron establishes a stable, effective synaptic input to only one or a few of these subcortical target populations, and the remaining collateral branches regress. The postnatal maturation of corticospinal neurons, examined in this study, is compatible with such a model.

Animals↗