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Response to transient disturbances during intentional forearm flexion in man.

Steps of torque were applied to the human forearm during intentional flexion movements with peak velocities of 40-500 degrees/sec and during ballistically initiated flexion movements. The question asked was whether or not the motor ouput to both agonist and antagonist muscles is independent of sensory input data or is accessible and influenced by these inputs. The data obtained demonstrate unequivocally that the applied perturbation affects the motor output, irrespective of the speed of the movement. The time of onset of the reflex changes in motor output and their maxima are related to the movement's parameters. Data are presented which indicate that the source for the reflex changes observed are the muscle spindles.

Afferent Pathways↗

Modulation of the myotatic reflex gain in man during intentional movements.

Human subjects were asked to perform sinusoidal tracking movements (0.5--3.0 Hz) with their forearms while external torque disturbances were applied at the elbow. The changes in angular position, velocity, and acceleration produced by these disturbances were found to be represented in the reflex changes in EMG activity of both biceps and triceps muscles. The gain of each of these reflex components varied during the tracking task, their maximal being about the same as those measured when the torque disturbances were applied in the absence of movements and the subjects attempted to maintain a constant forearm position. Such changes in gain were found to be centrally regulated since they were shown not to depend on the movement itself, being also present during force tracking, i.e. under nearly isometric conditions. Also their minima and maxima did not coincide with those of the EMG activity. These results suggest that an internal plan (or model) of the learned task is present, whereby reflex gains can be regulated independently from the motion and alpha-motoneuron activity. Such regulation effectively uncouples the reflex motor output from the intentionally controlled motion and maintains spindle sensitivity to external disturbances independent of large changes in muscle length. These conclusions are discussed in the context of the functional role of gamma-motoneurons in the control of movements.

Adult↗

An intentional-action guiding algorithm in a user-programmable memory prosthesis.

Patients with memory problems tend to forget what their intentions are in the course of carrying out a series of sequential actions directed towards a desired goal. To aid in this problem, a working memory prosthesis has been designed and implemented on a microcomputer connected to a voice synthesizer. The instrument keeps the patient on the track of his current action plan by uttering pre-stored spoken instructions at periodic intervals. An interface algorithm allows the user to enter the steps of his own routine action-patterns in computer memory along with mnemonics for evoking them. Further potential uses of such a memory prosthesis are described.

Computers↗

Evoked potentials from passive elbow movements. II. Modification by motor intent.

Subjects were instructed to remain passive or to react to a forearm perturbation by opposing the imposed movement. Evoked potentials (EPs) were recorded at 8 scalp sites in both conditions. In the React condition, reflexes were observed in the EMG (mean onsets of 67 and 81 msec) and the EP was modified. Source derivation techniques revealed that the earliest cortical response (31 msec) across the central sulcus was not changed. Therefore the intention to react did not seem to affect afferent transmission to the primary sensorimotor cortex. Two periods of modulation were observed. In both, parietal and frontal potentials were modulated together, prior to the reflex components. After 70 msec, the pattern of potential gradients which occurred in the Passive case was accelerated and intensified in the React condition. The overall effect was to focus a larger zone of negativity over motor cortex at the time of triggered EMG output (109 msec). The earlier changes in cortical activity could be causally related to the appearance of the late stretch reflex. Since parietal and frontal areas were principally involved and not the motor area, it is suggested that the former exert a modulatory influence on spinal and brain-stem reflex centres.

Elbow↗

A protocol for the assessment of prelinguistic intentional communication.

This article presents a protocol for the assessment of prelinguistic intentional communication with young and/or severely language-impaired children. A set of tasks and scoring procedures are presented for the elicitation of proto-declarative and proto-imperative behaviors. Data are presented that attest to the reliable utilization of this protocol.

Child Language↗

Intentional and unintentional memory in young children: remembering vs. playing.

In an exploration of Istomina's (1975) paradigm contrasting children's recall from an involuntary or game-like context with recall from an intentional or lesson-like context, this study investigated the relative efficacy of asking 4- and 5-year-olds "to remember" or "to play with" a set of 16 pictures or toys in a naturalistic or laboratory setting. The children's behavior and language were measured during two 2-min study phases, after which recall was assessed. Toys promoted different study phase activities and better retention than pictures, asking a child "to remember" a set of toys led to less recall than asking the child "to play" with the toys, and, across all conditions, instructions "to play" and "to remember" elicited differentiated study phase responses but similar levels of retention.

Attention↗

Disproportionate intentional spatial-memory impairments in amnesia.

Twenty-four amnesics, including patients with Korsakoff's disease, post-encephalitic amnesia and amnesia caused by rupture of an anterior communicating artery aneurysm (ACoAA), were compared with 24 matched control subjects on a task in which words were presented in any one of four positions on a computer screen and subjects were instructed to remember both the words and their locations. The patients were tested after more learning opportunity, exposure to shorter lists, and after shorter delays than were their controls in order to match the word recognition performance of the two groups. Under these conditions, the amnesics' ability to locate recognized words was significantly worse than that of their controls. Although there was a tendency for the ACoAA patients to show more severe spatial memory deficits than Korsakoff patients, there was no clear evidence that aetiology of amnesia was a critical determinant of whether spatial memory was more impaired than word recognition. It was concluded that amnesics show a disproportionately severe memory deficit for spatial information that is intentionally encoded as well as for that which is incidentally encoded.

Adolescent↗

Intentional replantation of a maxillary molar. A 4-year follow-up.

A 4-year follow-up of a case treated by intentional replantation has been presented. A maxillary molar with a metal core was diagnosed as having acute apical periodontitis, endodontic treatment was determined to be impractical, and the tooth was extracted. Three roots canals which could not be detected roentgenologically were discovered and, after apicoectomy and reversed amalgam filling, the tooth was replanted in its socket. The follow-up reveals periapical repair with no signs of root resorption or ankylosis.

Adult↗

Intentional vital root transection: a 52-week histopathologic study in Macaca mulatta.

Past studies dealing with the vascular supply to surgically mobilized dentoalveolar segments have mentioned occasional encounters with vital root transection and have noted varying degrees of pulpal response to this insult. The purpose of this investigation was to observe the pulpal and periapical responses of monkey dental tissues to intentional vital root transection over a 1-year postoperative period. Four adult Macaca mulatta monkeys were used in this study. All roots were surgically transected within the apical third with a bur. Maxillary and mandibular quadrants for 1, 2, 3, 4, 6, 12, 24, and 52 weeks following surgery were obtained after the animals were killed by perfusion of the left ventricle. The tissue blocks were prepared by routine histologic methods. The results demonstrated a disruption of the normal pulpal architecture, with initial pulpal degeneration and subsequent early replacement by the periodontal ligament tissue. A cellular cemental lining of the root canal occurred in all specimens. The periodontal ligament-like tissue continued to deposit cementum, resulting in almost total obliteration of the root canal and pulp chamber and leaving an intact but much reduced blood supply to the pulp chamber containing periodontal tissues.

Animals↗

Intentional replantation: a successful alternative for hopeless teeth.

An interesting case of intentional reimplantation, in which the distal root of a mandibular molar was reimplanted after hemisection, is reported for the first time. This root served as the distal abutment for a three-unit bridge. A 3-year follow-up revealed a successful outcome, with a clinically asymptomatic and functional tooth with no radiographic signs of resorption or ankylosis.

Calcinosis↗

Saccadic reaction times in gap/overlap paradigms: a model based on integration of intentional and visual information on neural, dynamic fields.

The systematic variations of regular saccadic reaction times induced in gap/overlap paradigms are addressed by a quantitative model. Intentional and visual information are integrated on a retinotopic representation of visual space, on which activity dynamics is related to movement initiation. Using a specific conception of "motor preparation", known effects of general warnings and fixation point on- and offsets are reproduced. Results of new experiments are predicted and the extent to which fixation point offsets are specific to ocular responses is analyzed in the light of the exposed model architecture. Relations of the theoretical framework to neurophysiological findings are discussed.

Fixation, Ocular↗

Development of EMG-based mode and intent recognition algorithms for a computer-controlled above-knee prosthesis.

Conventional above-knee prostheses are unable to replace normal leg function due to the lack of adaptive control. Computer-controlled prostheses offer the possibility to implement such adaptive control. For a particular locomotion mode, control algorithms can generate appropriate damping profiles as a function of selected sensory inputs and stored information on normal walking. However, it is essential in such systems that the locomotor modes can be determined accurately from the inputs of the control system. Recognition of the intent to change from one mode to another is also a necessity because the control system has to account for such transitions. The possibility of using EMG signals from hip muscles and muscle residuals of the stump for this purpose is investigated. The modes tested are level walking, ramp ascent and ramp descent with slopes of 6 degrees and 9 degrees. EMG activity curves for three muscles: gluteus maximus, gluteus medius and tensor fasciae latae, are presented for the different modes. The results are obtained from two reference groups of 12 normal individuals and from a prosthetic patient. The results show the possibility of discriminating between modes. A discussion is made of the implementation of the results obtained by a finite state approach and the difficulties relating to the use of EMG signals for control purposes.

Algorithms↗

Epidermoid carcinoma of the anal margin: 17 cases treated with curative-intent radiation therapy.

Between 1973 and 1991, 17 patients with epidermoid carcinoma of the anal margin without evidence of distant metastasis were treated with curative-intent radiation therapy (RT). There were nine T1-tumors, six T2-, one T3- and one T4-tumor; two patients presented with inguinal node involvement: one N1 and one N3. Nine patients underwent prior incomplete local excision (six with microscopic involvement of surgical margins and two with macroscopic residual disease). The radiation dose to the tumor was 60-70 Gy; the radiation dose to the inguinal lymph nodes was 40-45 Gy in N0, and 50-60 Gy for involved inguinal nodes. The 5- and 10-year cancer-specific survival rates were 86.2% and 77.5%, respectively. The same probabilities were 100% and 100% for T1-tumors, 60% and 40% for T2-tumors. Severe complications occurred in two patients, one anal radionecrosis requiring a colostomy and one permanent anal incontinence after local excision, which was non-related to irradiation. For the cured patients, the sphincter preservation rate after 5 years was 82% (9/11). In univariate analysis and in Cox multivariate analysis, the cancer-specific survival rate was influenced by one factor: the tumor size.

Adult↗

Antiseptic toxicity in wounds healing by secondary intention.

The effects of two commonly used antiseptics for chronic ulcer care, chloramine T and chlorhexidine, on the biochemical and histological parameters of healing have been examined. The antiseptics were compared with saline when applied to 10 mm skin defects on Sprague-Dawley rats. Chloramine T significantly delayed the production of collagen and prolonged the acute inflammatory response compared with saline. Chlorhexidine did not differ from saline. We conclude that hypochlorite antiseptics may adversely affect healing by secondary intention and the antibacterial and desloughing action of agents should be carefully balanced against their toxic effect.

Animals↗

Effects of reducing plantar support on anticipatory postural and intentional activities associated with flexion of the lower limb.

This study examines the anticipatory dynamics of the center of gravity and the EMG activity of ipsi- and contralateral (to the moving leg) soleus (SOL) and tibialis anterior (TA) in flexion of the lower limb executed from different plantar support surfaces. Subjects were standing initially on a plane surface or a surface reduced to two narrow rods under the moving or stance foot. Reduction of the plantar support surface under the moving limb induced a decrease in the anticipatory activity of both TA and in the intentional ipsilateral SOL EMG activity, but the anticipatory activity of SOL did not change. The lateral and vertical accelerations of the center of gravity decreased. When the reduction was under the stance limb, the biomechanical traces did not change markedly and the EMG activity was similar to that of the control situation. The differential effects in EMG activity, depending on whether the reduced plantar surface was under the moving or the stance side, suggest that tonic plantar stimulation induces complex reflex actions on muscles involved in the preparation and execution of voluntary movement. The functional demand could explain the gating from one motor organization to another.

Adult↗

Nasopharyngeal carcinoma in Saudi Arabia: a retrospective study of 166 cases treated with curative intent.

A retrospective review was performed of the medical records of 166 adult patients with biopsy-proven carcinomas of the nasopharynx treated with curative intent at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. All patients were treated between June 1975 and December 1985 using megavoltage therapy equipment. Most patients presented with advanced nodal disease: 23 patients (13.9%) were N0, 16 patients (9.6%) were N1, 29 patients (17.5%) were N2, and 98 patients (59%) were N3. The overwhelming majority of patients had nonkeratinizing lesions (158/166). At the time of analysis, mean follow-up time was 24.2 months (range 2-108). Actuarial curves are presented for local/regional control as a function of T-stage and N-stage and for survival and time to development of distant metastases as a function of N-stage. At 4 years local/regional control was 70% for T1 lesions, 59% for T2 lesions, 30% for T3 lesions, and 35% for T4 lesions. There was little correlation between local/regional control and N-stage being about 50% at 4 years for all nodal subgroups. Only six patients exhibited an isolated first failure in the regional nodes alone, whereas 60 patients failed initially at the primary site (either alone or in conjunction with a simultaneous nodal failure). The development of distant metastases correlated to some extent with nodal disease ranging from 20% at 4 years for T1/T2 N0 patients to 70% for patients who initially presented with N3 disease. Survival data was more difficult to obtain due to cultural biases in a medically unsophisticated patient population. True survival curves are bounded by calculating actuarial curves in two ways: death as the failure endpoint and death plus lost-with-active-disease as failure endpoints. In terms of the latter curves, at 4 years "survival" ranged from 39% for patients with T1/T2 N0 lesions to 23% for patients with N3 lesions.

Adult↗

High-dose reirradiation of head and neck cancer with curative intent.

PURPOSE: This study evaluates the response of new or recurrent head and neck cancers and the response of associated normal tissues to high dose reirradiation with curative intent. METHODS AND MATERIALS: From 1964 to 1991, 15 patients with in-field new second head and neck cancers and 85 patients with recurrent head and neck cancers have had high-dose reirradiation that overlapped with previously irradiated volumes. Reirradiation was given only to patients with no more than apparent minimal clinical radiation effects from the first radiation course. The reirradiation consisted of external beam only in 82 patients, external beam plus intracavitary or interstitial implant irradiation in 14 patients, and interstitial implant irradiation only in four patients. The combined overlapping dose from both the initial and subsequent irradiation (including brachytherapy) was 69-89 Gy in 14 patients, 90-99 Gy in 15 patients, 100-119 Gy in 27 patients, and 120 Gy or greater in 44 patients. Four patients had areas of overlap that received greater than 180 Gy. RESULTS: The actuarial 5-year survival was 37% for patients with new second primary cancers and 17% for patients with recurrent cancers. Loco-regional tumor control was achieved in 60% of the patients with new tumors and in 27% of the patients with recurrent tumors. Nine of the 100 patients developed severe adverse normal tissue effects from the reirradiation. CONCLUSION: High-dose reirradiation of head and neck cancers can be successful curative treatment in a significant proportion of patients. It is associated with substantial but acceptable risks in properly selected patients.

Dose-Response Relationship, Drug↗