The effects of ADL on recovery of swallowing function in stroke patients after acute phase.

This study aimed to examine the association between the degree of recovery from dysphagia and changes in functional independence measure (FIM) items in stroke patients after acute phase by conducting a historical cohort study, because none explains the effects of activities of daily living (ADL) on recovery of swallowing function. Study patients included hospitalised stroke patients after acute phase in whom dysphagia was confirmed (n = 72). Change in nutritional intake method score was examined for association with age, days from stroke onset to admission, length of hospital stay and change in FIM score. Moreover, to examine characteristics of patients who were removed from tube feeding, all patients who required tube feeding at the time of admission were divided into two groups comprising those who required tube feeding at discharge and those who did not. A significant and positive association was observed between change in nutritional intake method and FIM for all items other than self-care of bathing, locomotion of stairs and problem solving. Patients who were removed from tube feeding were significantly younger than those who required tube feeding at the time of discharge (P < 0.041) and also showed significantly higher FIM scores for transfer and all cognitive FIM items at the time of admission (P < 0.05). This study demonstrated that nutritional intake methods improve in conjunction with FIM improvements in patients with dysphagia following the acute phase of stroke. Our results suggest that the age and cognitive function may influence the recovery of patient ability of oral intake.

Effects of reclining posture on velopharyngeal closing pressure during swallowing and phonation.

Velopharyngeal closure plays an important role in preventing air pressure leakage during swallowing and phonation from oropharynx to nasopharynx. Levator veli palatini muscle activity is influenced by oral and nasal air pressure, volume of the swallow bolus and postural changes. However, it is unclear how velopharyngeal closing pressure is affected by reclining posture. The purpose of this study was to investigate the effects of reclining posture on velopharyngeal closing pressure during swallowing and phonation. Nine healthy male volunteers (age range, 27-34 years) participated in this study. Velopharyngeal closing pressure during a dry swallow, a 5-mL liquid swallow, a 5-mL honey-thick liquid swallow and phonations of /P∧/ and /K∧/ were evaluated in an upright posture and at reclining postures of 60° and 30°. A manometer catheter was inserted transnasally onto the soft palate, and each trial was repeated three times. A solid-state manometer catheter with an intra-luminal transducer was used to evaluate the amplitude and duration of each trial, and data were statistically analysed. Average amplitudes during dry and liquid swallows were significantly lower in reclining postures compared with the upright posture, but the amplitude was not significantly different during the thick liquid swallow. Average durations were not affected by postural changes. The amplitudes during phonations were lower in reclining postures, but the differences were not significant. Velopharyngeal closure is significantly affected by reclining posture. This suggests that velopharyngeal closing pressure may be adjusted according to afferent inputs, such as reclining posture and bolus viscosity.

Deficits of masticatory movements caused by lesions in the orofacial somatosensory cortex of the awake cat.

The purpose of this study was to determine the role of somatosensory cortex (SI) in the control of orofacial movements during eating. We identified perioral and tongue projection regions of the cat SI and destroyed cells in one region by injecting kainic acid. The effects on orofacial behavior were then studied over a period of 4-6 weeks. Cats with unilateral lesions in the perioral region (PL-cats) dropped food from the contralateral side of the mouth in the early phase. Failure in erection of the contralateral whisker hairs during masticatory movements and delay of the masticatory start were observed throughout the experimental period. Furthermore, in the late phase, PL-cats showed prolongations of the masticatory and food intake periods, which were accompanied by the increase in the number of swallows and chewing cycles. Cats with unilateral lesions in the tongue region (TL-cats) showed the prolongation of the masticatory period in the early phase, which was accompanied by the increase in the number of swallows and chewing cycles. TL-cats did not show the prolongation of the food intake period and failure in erection of the contralateral whisker hairs. In both PL- and TL-cats, masticatory and swallowing rhythms were normal.

Morphological analysis of cat masseteric motoneurons after intracellular staining with horseradish peroxidase.

Intracellular injection of horseradish peroxidase (HRP) into 58 masseteric motoneurons identified by antidromic activation was performed in cats under pentobarbital anesthesia. Monosynaptic EPSPs were evoked by masseteric nerve stimuli in 52 cells, and were absent in the remaining six cells. The antidromic nature of the evoked spikes was confirmed by IS-SD separation observed at high frequency (50 Hz) stimulation. Motoneurons with monosynaptic excitation from masseter afferents showed IPSPs following stimulation of lingual and inferior alveolar nerves. Motoneurons which did not show monosynaptic excitation from masseter afferents showed no IPSPs from the above nerves. There were no differences in cell size or the number of stem dendrites between motoneurons with and without monosynaptic EPSPs. No recurrent collaterals were observed in any motor axons. Motoneurons with monosynaptic EPSPs were located at all rostrocaudal levels throughout the trigeminal motor nucleus, whereas motoneurons without such EPSPs were encountered only at the middle level. Dendrites of motoneurons with monosynaptic EPSPs did not extend into the medial portion of the nucleus where motoneurons innervating the anterior belly of the digastric muscle were located. In contrast, motoneurons without monosynaptic EPSPs had dendrite branches extending well into the medial part. The results show that there are two subpopulations of masseteric motoneurons that differ in peripheral inputs as well as dendritic morphology.

Regenerative process after experimental injury of hypoglossal nerves in guinea pigs.

The nerve regenerative process has been investigated by many studies. However, the quantification of the degree of crush of peripheral nerves has not yet been performed. The aim of this study was to determine and standardize the ligature intensity and crush level of the hypoglossal nerve of guinea pigs. The compound action potentials evoked by electric stimulation were used as an index of the degree of nerve crush. To demonstrate nerve regeneration after ligating and crushing of the right hypoglossal nerve, fluorescein isothiocynate conjugated cholera toxin-B subunit (CTb-FITC) was injected into the intact fiber of the left hypoglossal nerve, and the central side from the crushed region of the right hypoglossal nerve fiber. The total cross sectional area of the retrograde-labeled hypoglossal motoneurons was investigated under a confocal laser scanning microscope. The results of the evaluation using CTb-FITC indicated that the nerve regeneration occurred from two weeks after crush and recovered in six weeks.

Mastication-related neurons in the orofacial first somatosensory cortex of awake cats.

In the orofacial area of the first somatosensory cortex (SI), we recorded single unit activity from 699 neurons in 11 awake cats. Fifty-two percent (362/699) were mastication-related neurons (MRNs) showing activity related to some aspects of masticatory movements. MRNs were divided into three types by their activity patterns: (1) the rhythmical type, showing rhythmical bursts in pace with the masticatory rhythm; (2) the sustained type, showing a sustained firing during the period of taking food and (3) the transient (biting) type, showing intense discharges in coincidence with biting hard food. MRNs had mechanoreceptive fields in the perioral, tongue, periodontal and mandibular regions. The activities of perioral rhythmical-MRNs, mandibular transient-MRNs, tongue rhythmical-MRNs and periodontal transient-MRNs were correlated with food texture, while perioral rhythmical-MRNs, perioral sustained-MRNs and tongue sustained-MRMs were not. Both facial and intraoral MRNs were scattered throughout the facial and intraoral projection areas in SI. These findings provide evidence that the orofacial SI monitors masticatory movements for food ingestion.

Fifth somatosensory cortex (SV) representation of the whole body surface in the medial bank of the anterior suprasylvian sulcus of the cat.

The physiological properties of neurons in the medial bank of the anterior suprasylvian sulcus (ASSS-m) of the cat's cortex were studied using unit recording techniques. Receptive fields (RFs) on the face are represented in the most rostral aspects of the ASSS-m. Of these neurons, 84% responded to light touch of the skin on the contralateral region of the face and 12% responded to mechanical stimulation of facial hair. In addition, 4% of the neurons responded to light touch to the skin or mechanical stimulation of the hair on the contralateral face and also to visual stimuli. The RFs of neurons responsive to the hindlimb and tail are located in the most caudal aspects of the ASSS-m. 22% of these neurons responded to the light touch to the skin and 78% responded to movement of hair. The RFs of neurons responsive to the trunk area in the ASSS-m are located between the facial and hindlimb regions. Of these neurons, 2% responded to light touch of the skin and 98% responded to movements of hair. Some neurons which responded to stimulation of hair or skin on the trunk included forelimb and/or hindlimb areas. In addition, some neurons had RFs on both sides of the trunk including the shoulder area. These regions were in area 5a. Various features of representation in ASSS-m distinguish this region from other somatosensory areas. We designate the ASSS-m as the fifth somatosensory cortex (SV).

Topographical distribution and functional properties of cortically induced rhythmical jaw movements in the monkey (Macaca fascicularis).

1. The lateral part of the pericentral cortex of both hemispheres in three awake monkeys was explored with intracortical microstimulation (ICMS) using short trains (T/S; 200-microseconds pulses at 333 Hz for 35 ms, less than or equal to microA) and long trains (C/S; 200-microseconds pulses at 50 Hz for 3 s, less than or equal to 60 microA). In both hemispheres of one of these monkeys, the responsiveness of single cortical neurons to stimulation of the orofacial region was tested at the same intracortical sites where ICMS was applied. 2. Movements were evoked from four physiologically defined cortical regions: the primary face motor cortex (MI), the primary face somatosensory cortex (SI), the principal part of the cortical masticatory area (CMAp) which was located in the precentral gyrus lateral to MI, and a deep part of the cortical masticatory area (CMAd) which was located in the inferior face of the frontal operculum. 3. Two types of cortically induced movements were observed: a single twitch movement and EMG activity of the orofacial muscles that was evoked by T/S at a short latency (10-45 ms) and rhythmical jaw movements (RJMs) which were only evoked by C/S. 4. RJMs were evoked at C/S frequencies ranging from 20 to 300 Hz. At movement threshold, the frequency of the cortically induced RJMs varied from 0.7 to 1.5 Hz and usually increased with the increase of C/S intensity up to 2 times movement threshold. The vertical amplitude of RJMs was also stimulus dependent, and at movement threshold it ranged from 3 to 9 mm. 5. The movement patterns of the cortically induced RJMs remained constant during the course of C/S but could be differentiated in the frontal plane into ipsilateral- (RJMi), vertical-(RJMv), and contralateral- (RJMc) directed movements. These three different patterns of RJMs were associated with different patterns of masticatory muscle activity. 6. Each cortical region contained many sites from which RJMs could be induced (so-called RJM sites). The RJMi sites were more numerous than RJMc sites in all regions except SI and were located anterolateral or lateral to the RJMc sites in each region; the RJMv sites were scattered throughout each cortical region. 7. In MI, C/S elicited RJMs from 94 intracortical sites from which short-latency twitch movements could also be evoked by T/S.(ABSTRACT TRUNCATED AT 400 WORDS)

Input-output relationships of the primary face motor cortex in the monkey (Macaca fascicularis).

1. Somatosensory afferent input and its relationship with efferent output were examined in the primary face motor cortex (MI) and adjacent cerebral cortical areas. Excitatory afferent inputs were tested in a total of 1,654 single neurons recorded in awake or anesthetized monkeys (Macaca fascicularis), and output was characterized in these same monkeys by the movement and EMG responses evoked by intracortical microstimulation (ICMS) at the neuronal recording sites. 2. Most neurons in the MI area responded to light tactile stimulation of the orofacial region, especially the upper lip, lower lip, and tongue. Although contralateral afferent inputs predominated, 21% of the neurons received ipsilateral or bilateral orofacial inputs. The afferent input evoked by tactile stimulation of the upper and lower lips was represented especially at the medial border and the input from the tongue at the lateral border of MI. However, in most regions of MI between the medial and lateral borders, an intermingling of tactile inputs from different orofacial areas occurred. Multiple representation of tactile input from the same orofacial area was found in several, often quite separate, intracortical sites in MI. 3. Only a small proportion of the MI neurons could be activated by the deep stimuli used (e.g., stretch and pressure applied to muscle, passive jaw movement, low-intensity stimulation of hypoglossal nerve) from the orofacial region. Those neurons which did respond to these low-threshold deep inputs were not clearly segregated from those which responded to tactile input, although most of the neurons receiving deep input were located in the rostral part of MI. 4. A somatotopic pattern of representation of orofacial tactile input was more obvious in the primary face somatosensory cortex (SI). At the medial border of SI, the periorbital area was represented, then followed laterally in sequence the tactile representation of the upper lip, lower lip, and intraoral area. Contralateral afferent inputs predominated, but as in MI, a considerable proportion of SI neurons received ipsilateral or bilateral orofacial inputs. Few neurons in the region explored (areas 3b, 1, and 2) responded to deep orofacial stimuli. 5. Tactile input also dominated the input patterns of neurons in the premotor cortex (PM). Most neurons received ipsilateral or bilateral orofacial afferent inputs and no clear somatotopic pattern was noted. Several PM neurons were also activated by visual stimuli. 6. Muscle twitches evoked by ICMS were limited to MI.(ABSTRACT TRUNCATED AT 400 WORDS)

Organization of the primate face motor cortex as revealed by intracortical microstimulation and electrophysiological identification of afferent inputs and corticobulbar projections.

1. The technique of intracortical microstimulation (ICMS), supplemented by single-neuron recording, was used to carry out an extensive mapping of the face primary motor cortex. The ICMS study involved a total of 969 microelectrode penetrations carried out in 10 unanesthetized monkeys (Macaca fascicularis). 2. Monitoring of ICMS-evoked movements and associated electromyographic (EMG) activity revealed a general pattern of motor cortical organization. This was characterized by a representation of the facial musculature, which partially enclosed and overlapped the rostral, medial, and caudal borders of the more laterally located cortical regions representing the jaw and tongue musculatures. Responses were evoked at ICMS thresholds as low as 1 microA, and the latency of the suprathreshold EMG responses ranged from 10 to 45 ms. 3. Although contralateral movements predominated, a representation of ipsilateral movements was found, which was much more extensive than previously reported and which was intermingled with the contralateral representations in the anterior face motor cortex. 4. In examining the fine organizational pattern of the representations, we found clear evidence for multiple representation of a particular muscle, thus supporting other investigations of the motor cortex, which indicate that multiple, yet discrete, efferent microzones represent an essential organizational principle of the motor cortex. 5. The close interrelationship of the representations of all three muscle groups, as well as the presence of a considerable ipsilateral representation, may allow for the necessary integration of unilateral or bilateral activities of the numerous face, jaw, and tongue muscles, which is a feature of many of the movement patterns in which these various muscles participate. 6. In six of these same animals, plus an additional two animals, single-neuron recordings were made in the motor and adjacent sensory cortices in the anesthetized state. These neurons were electrophysiologically identified as corticobulbar projection neurons or as nonprojection neurons responsive to superficial or deep orofacial afferent inputs. The rostral, medial, lateral, and caudal borders of the face motor cortex were delineated with greater definition by ICMS and these electrophysiological procedures than by cytoarchitectonic features alone. We noted that there was an approximate fit in area 4 between the extent of projection neurons and field potentials anti-dromically evoked from the brain stem and the extent of positive ICMS sites.(ABSTRACT TRUNCATED AT 400 WORDS)