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PubMed1998

Scalar expectancy theory and peak-interval timing in humans.

The properties of the internal clock, temporal memory, and decision processes used to time short durations were investigated. The peak-interval procedure was used to evaluate the timing of 8-, 12-, and 21-s intervals, and analyses were conducted on the mean response functions and on individual trials. A distractor task prevented counting, and visual feedback on accuracy and precision was provided after each trial. Mean response distributions were (a) centered at the appropriate real-time criteria, (b) highly symmetrical, and (c) scalar in their variability. Analysis of individual trials indicated more memory variability relative to response threshold variability. Taken together, these results demonstrate that humans show the same qualitative timing properties that other animals do, but with some quantitative differences.

Adult↗

PubMed1990

Cue exposure during a period of abstinence reduces the resumption of operant behavior for oral ethanol reinforcement.

The present study examined the prediction made by learning theories of drug addiction that systematic cue exposure (extinction) procedures should reduce ethanol (EtOH) consumption. In 3 experiments, male rats were trained on a variable-interval schedule to press a bar for a sweetened EtOH solution. These procedures established associations between a variety of cues (contextual, response feedback, visual, taste) and EtOH consumption. After performance had stabilized, a period of abstinence was imposed during which no EtOH was available. Groups of rats differed only in the number of EtOH-associated cues experienced during this period. The level of EtOH consumption after abstinence was reduced in proportion to the degree of cue exposure. These findings support the learning hypothesis that drug-associated cues contribute to the resumption of drug-taking behavior and further suggest that extinction procedures may be valuable in preventing relapse.

Alcohol Drinking↗

PubMed2005

Self-motion perception during locomotor recalibration: more than meets the eye.

Do locomotor aftereffects depend specifically on visual feedback? In 7 experiments, 116 college students were tested, with closed eyes, at stationary running or at walking to a previewed target after adaptation, with closed eyes, to treadmill locomotion. Subjects showed faster inadvertent drift during stationary running and increased distance (overshoot) when walking to a target. Overshoot seemed to saturate (i.e., reach a ceiling) at 17% after as little as 1 min of adaptation. Sidestepping at test reduced overshoot, suggesting motor specificity. But inadvertent drift effects were decreased if the eyes were open and the treadmill was drawn through the environment during adaptation, indicating that these effects involve self-motion perception. Differences in expression of inadvertent drift and of overshoot after adaptation to treadmill locomotion may have been due to different sets of ancillary cues available for the 2 tasks. Self-motion perception is multimodal.

Adaptation, Psychological↗

PubMed2001

Perceptual basis of bimanual coordination.

Periodic bimanual movements are often the focus of studies of the basic organizational principles of human actions. In such movements there is a typical spontaneous tendency towards mirror symmetry. Even involuntary slips from asymmetrical movement patterns into symmetry occur, but not vice versa. Traditionally, this phenomenon has been interpreted as a tendency towards co-activation of homologous muscles, probably originating in motoric neuronal structures. Here we provide evidence contrary to this widespread assumption. We show for two prominent experimental models-bimanual finger oscillation and bimanual four-finger tapping-that the symmetry bias is actually towards spatial, perceptual symmetry, without regard to the muscles involved. We suggest that spontaneous coordination phenomena of this kind are purely perceptual in nature. In the case of a bimanual circling model, our findings reveal that highly complex, even 'impossible' movements can easily be performed with only simple visual feedback. A 'motoric' representation of the performed perceptual oscillation patterns is not necessary. Thus there is no need to translate such a 'motoric' into a 'perceptual' representation or vice versa, using 'internal models' (ref. 29). We suggest that voluntary movements are organized by way of a representation of the perceptual goals, whereas the corresponding motor activity, of sometimes high complexity, is spontaneously and flexibly tuned in.

Fingers↗

PubMed2003

Fabrication of solid-state nanopores with single-nanometre precision.

Single nanometre-sized pores (nanopores) embedded in an insulating membrane are an exciting new class of nanosensors for rapid electrical detection and characterization of biomolecules. Notable examples include alpha-hemolysin protein nanopores in lipid membranes and solid-state nanopores in Si3N4. Here we report a new technique for fabricating silicon oxide nanopores with single-nanometre precision and direct visual feedback, using state-of-the-art silicon technology and transmission electron microscopy. First, a pore of 20 nm is opened in a silicon membrane by using electron-beam lithography and anisotropic etching. After thermal oxidation, the pore can be reduced to a single-nanometre when it is exposed to a high-energy electron beam. This fluidizes the silicon oxide leading to a shrinking of the small hole due to surface tension. When the electron beam is switched off, the material quenches and retains its shape. This technique dramatically increases the level of control in the fabrication of a wide range of nanodevices.

Crystallization↗

PubMed1987

Detection of hypercapnia by normal subjects.

1. To investigate whether changes in PaCO2 can be detected independently of the CO2-induced changes in pulmonary ventilation, we tested five normal subjects for the ability to distinguish different levels of end-tidal PCO2 (PETCO2) while holding minute ventilation constant. 2. Helped by a visual feedback system, the subjects maintained a constant ventilation targeted at a level that was higher than that dictated by the chemical drive at PETCO2 = 50 mmHg (6.7 kPa). End-tidal PCO2 was held at 40 mmHg (5.3 kPa) during the first 2 min of each test trial ('control period'); then, for 4 min ('test period'), PETCO2 was either elevated to 50 mmHg or kept at 40 mmHg. Twelve runs were performed by each subject. 3. In 24 out of the total 30 trials (80%) in which PETCO2 was raised during the test period to 50 mmHg, the subjects detected the changes. There was one false positive result (3%), when PETCO2 kept at 40 mmHg during the test period was reported as different from control. In four out of the five subjects the ability to detect the change in PETCO2 from 40 to 50 mmHg was statistically significant. 4. We conclude that increases in PETCO2 can be detected independently of changes in the absolute level of ventilation.

Carbon Dioxide↗

PubMed1980

Performance of children with severe to profound auditory impairment in instrumentally guided reduction of nasal resonance.

Twelve students at the Kentucky School for the Deaf were studied using a bioelectronic instrument to provide visual feedback of the degree of nasal resonance, thereby guiding them toward reduction of excessively nasal voice quality. The subjects were given a maximum of fourteen 20-min sessions of training. The results indicated that the feedback information was used very effectively by five subjects and somewhat effectively by four others. The remaining three subjects did not demonstrate a consistent relationship between periods of training and reduction in nasal resonance. Pre- and post-training testing using stimuli not included in the training material demonstrated significant generalization of the nasalance control gained in the training sessions.

Adolescent↗

PubMed1985

A microcomputer-based wearable biofeedback device to improve transfer of treatment in parkinsonian dysarthria.

Achieving transfer of treatment outside the clinic is a problem for almost all individuals with speech disorders but has been particularly difficult in the treatment of patients with Parkinsonism. Given this situation and the frequency of vocal intensity problems in this population, we developed a wearable biofeedback device that could provide a patient with information about speech intensity outside the clinic. Auditory-perceptual and acoustic analyses were performed on audiotaped samples of reading and spontaneous speech recorded in the clinic pre- and posttreatment and at 10- and 20-week follow-ups. Visual feedback of intensity was integrated with auditory cues from a microcomputer that was then worn outside the clinic. The results indicated that the subject did transfer a substantial portion of clinic improvement to the outside environment while wearing the feedback device and suggest the utility of a microcomputer-based wearable device for assessing treatment effects as well as for improving transfer.

Aged↗

PubMed1985

Speech production and oral motor skill in an adult with an unrepaired palatal cleft.

The aim of this study was to identify maneuvers and strategies that enabled an adult speaker to produce "pressure" consonants intelligibly despite an open cleft of the palate. Dynamic palatometry indicated that this was achieved in part by increasing linguapalatal contact in stop sound production and narrowing the linguapalatal groove in sibilant sound production. These adaptations apparently enabled the talker to compensate for reduced air supply in a manner similar to that identified previously in responses of subjects with esophageal speech. Oral motor skill was examined in a nonspeech task that involved tongue tip placement at six points along the palate with and without visual feedback. This revealed precise control of the tongue even in the region of the cleft. Less accurate tongue placement skills were found in the central palatal region despite intactness of the palate. This supports the hypothesis that phonetic inventories of human languages are shaped by oral motor capabilities.

Adult↗

PubMed1990

Ramp-and-hold force control in the upper and lower lips: developing new neuromotor assessment applications in traumatically brain injured adults.

The relation among several parameters of the ramp-and-hold force contraction and target force level was quantified for the upper and lower lip in 40 normal adults and in 4 young adults who had sustained traumatic brain injury (TBI). Using visual feedback, subjects produced ramp-and-hold compression lip forces as rapidly and accurately as possible to end-point target levels ranging from 0.25 to 2.00 newtons. In normal adults, significant positive linear relations were found between the parameters of the ramp-and-hold lip force task and target force level, including the peak rate of force change, peak force, and the mean and standard deviation of force during the hold phase. Though males and females have been shown to differ greatly on absolute maximum force-generating capabilities, they are virtually identical on the measures used to quantify the lip force ramp-and-hold task over the range of compression forces studied. Preliminary investigation of lip force control in 4 TBI subjects suggests that these quantitative measures are useful in determining the distribution and nature of motor impairment between the upper and lower lips during a dynamic force control task.

Adolescent↗

PubMed1992

The effects of auditory and visual interference on speech and sign.

Hearing adults produced signed and spoken monologues under conditions of quiet or 80 dB SPL of noise and with their vision unobstructed or obstructed. Their signs were videotaped and a random sample of 24 frames was analyzed in each condition through a computer program that determined the overall distance of the hand from a marker placed on the signer's torso. Vocal intensity was digitized from the tape recordings and analyzed by computer for 1 min of continuous speech in each condition. The visual obstruction had no effect either on the distance of the signs or on the vocal intensity of their speech. The subjects increased vocal intensity by about 55% when the noise was introduced (the usual Lombard effect), but the noise had no effect on the distance of the signs. Sign performance was not influenced by visual feedback, and sign and speech were independent communication systems, even in bilingual speaking and signing subjects.

Adult↗

PubMed1996

Sense of effort and the effects of fatigue in the tongue and hand.

Fatigue and increased effort are common symptoms for people with movement disorders and dysarthria, but they are rarely quantified. In an attempt to develop a clinically useful and physiologically meaningful measure of fatigue, we used a task that involves sustaining a target effort level without visual feedback while squeezing a bulb connected to a pressure transducer. In the first experiment, 12 healthy young adults performed the constant-effort task with the tongue and the preferred hand at 3 submaximal levels of effort. The resulting pressure declined over time as a negative exponential function with a nonzero asymptote. In the second experiment, 6 subjects performed the constant-effort task before and after acutely fatiguing the tongue and hand. The rate of pressure decline was significantly greater after fatigue. One possible mechanism for the characteristic negative exponential function is that it reflects a constant descending drive from higher centers in the CNS to the appropriate motoneuron pools. Thus, this technique may elucidate the contribution of central fatigue to normal and disordered speech.

Adolescent↗

PubMed1996

Negative intraoral air pressures of deaf children with cochlear implants: physiology, phonology, and treatment.

The primary purpose of this investigation was to examine deaf children's use of negative intraoral air pressures (-Po's) from a physiological and a phonological perspective, with the hope of gathering insight into the strategies these children use to produce speech. A secondary purpose was to compare the effectiveness of two methods of treating these deviant productions. Subjects were four profoundly deaf children, age 6:6-9:2, who used cochlear implants and had demonstrated persistent use of -Po's. Po's were collected during production of CV syllables with initial [p] and [b] and a variety of vowel contexts. Two of the children used -PO's more often before low than high vowels. We suggest that this vowel-based pattern may result when deaf children learn to lower their larynges in response to visible jaw lowering cues. Another child presented with a pattern of more frequent -Po's before front than back vowels, suggesting that she may have expanded her pharynx anteriorly as she attempted to achieve an anterior tongue placement. Two children also clearly used -Po's more frequently for voiced than voiceless stops, possibly resulting from a tendency to use the degree rather than the timing of vocal fold adduction to distinguish voiceless and voiced phonemes. Two of the children were enrolled in a single-subject multiple baseline study to compare the effectiveness of traditional articulation treatment and visual-feedback treatment. The child who was a far less proficient talker demonstrated rapid and sustained change, whereas the better talker demonstrated minimal change with treatment. This study provides evidence that (a) deaf children use speech production strategies quite unlike those of normally hearing children and (b) deviant speech behaviors of deaf children should be treated before they become part of functional phonological systems. This work highlights the need to consider the unique speech behaviors of deaf children, and their reliance on alternate feedback mechanisms, when developing assessment and treatment procedures.

Age of Onset↗

PubMed2001

Brain correlates of fast and slow handwriting in humans: a PET-performance correlation analysis.

The present study examined the cerebral control of velocity during handwriting. We employed H215O positron emission tomography (PET) to measure the regional cerebral blood flow (rCBF) in 10 healthy subjects. Participants were required to write the German verb 'bellen' ('to bark') either at their normal speed (i.e. fast open-loop handwriting) or to write at approximately half of their normal speed without visual feedback. The second task required a continuous modification of the motor output according to the kinaesthetic feedback from the hand (i.e. slow closed-loop handwriting). Pencil movements were recorded during PET scanning and analysed off-line using a stroke-based analysing program. The mean number of inversions in velocity (NIV) per stroke was used to quantify the mode of motor control during each PET scan. A NIV of 1 indicates fast open-loop processing, whereas an increase in NIV reflects a shift towards slow closed-loop processing of handwriting. Foci in the left primary sensorimotor cortex, the right lateral premotor cortex, the left anterior parietal cortex, the left anterior putamen, the left rostral supplementary motor area and the right precuneus showed a graded increase in functional activation with the mean NIV per stroke, suggesting that this set of brain regions is particularly involved in the processing of slow closed-loop writing movements. No area showed a negative relationship between rCBF and the mean NIV per stroke, suggesting that fast open-loop handwriting is achieved by an optimized cooperation of the manual sensorimotor network rather than by a selective activation of a distinct network component.

Adult↗

PubMed1998

The variability of bite force measurement between sessions, in different positions within the dental arch.

The effect of measuring bite force with different patterns of transducer on different occasions was studied. Maximum voluntary bite force was measured in eight volunteers. Three transducer positions, each with a different pattern of transducer, were used; between the anterior teeth, between the second premolar and the first molar on one side and between the second premolars and first molars on both sides. Visual feedback of force was provided. Two sets of five maximum clenches were recorded with a rest period in between. This sequence was repeated for each transducer and the experiment was repeated on three different days. The highest forces were measured with the bilateral posterior transducer (mean 580 N, s.d. 235) and the lowest on the anterior transducer (mean 286 N, s.d. 164). The standard deviations of the bite force mean values were used as an indication of the variability and were subjected to a non-parametric anova (Kruskal-Wallis). The forces recorded with each transducer position were significantly different between the transducers (P < 0.01) and the maximum bite force showed least variability when measured between the posterior teeth on one side only. There was little difference in bite force between the three different sessions (P > or = 0.05) when measured in the same position within the dental arch, whichever of the three positions that may be.

Adult↗

PubMed2000

Influence of clenching level on intercuspal contact area in various regions of the dental arch.

The purpose of this study was to evaluate the relationship between the clenching level and the intercuspal contact area in different regions of the dental arch. Twenty-five healthy subjects with natural normal dentitions and good occlusal support performed clenching tasks in the intercuspal position at four different levels (10, 30, 70 and 100% levels of maximum voluntary contraction) through EMG visual feedback from bilateral masseter and anterior temporal muscles. Simultaneously, the occlusal contacts were recorded with a silicone occlusal contact checking material (Black Silicone, GC Dental Industrial Corp., Tokyo, Japan). The occlusal records were analysed by an image analyser. Every area of the thickness less than 50 microm was determined to be an occlusal contact area. The occlusal contact areas on the anterior teeth (incisors and canines), the premolars (first and second premolars) and the molars (first and second molars) were calculated separately. The posterior occlusal contact area increased with an increase in the clenching levels but that of the anterior did not. The results of this study indicate that the increase in clenching forces affects the anterior and posterior occlusal contact areas differently.

Adult↗

PubMed2000

Changes in jaw-jerk on different levels of jaw closure and teeth-clenching in humans.

We investigated how the jaw-jerk in the human masseter muscle is modulated in relation to the level of jaw closure (JC) and teeth clenching. Electromyographic (EMG) activity was recorded with surface electrodes. Background EMG activity of the masseter muscle was kept at three low teeth clenching levels with visual feedback. The level of JC was changed in six steps along the habitual path of closure relative to the mean maximal jaw opening during gum chewing by inserting a bite block between the upper and lower molars. The jaw-jerk was evoked by applying mechanical stimulation of about 20 N with a hammer to the bite-fork placed on the lower molars on one side in each condition of combination of a level of JC with a level of teeth-clenching. At the resting condition the excitability of the jaw-jerk increased with JC, while at weak voluntary teeth clenching it then decreased and increased again as the jaw was progressively closed. It is suggested that the excitability of the jaw-jerk would increase toward the occlusal position, which in turn would contribute to smooth masticatory movements. In addition, the mode of modulation of the jaw-jerk was studied in a subject with skeletal malocclusion.

Adult↗

PubMed2003

Force-matching errors after eccentric exercise attributed to muscle soreness.

1. Experiments were performed to test the ability of human subjects to match forces in their elbow flexor muscles following eccentric exercise of one arm and, in a second series, after biceps brachii of one arm had been made sore by injection of hypertonic saline. 2. In the force-matching task, the elbow flexors of one arm, the reference arm, generated 30% of maximum voluntary contraction (MVC) under visual control. Subjects matched that level with their other arm, the indicator arm, without visual feedback. 3. After eccentric exercise of elbow flexors of the indicator arm, subjects felt they had achieved a satisfactory match while indicating forces that were significantly lower, by approximately 5%, than the reference level. Errors were in the opposite direction (i.e. forces were overestimated) when the reference arm was exercised. 4. Errors were reduced when matching forces were expressed as fractions of the sessional MVC rather than the pre-exercise MVC. Residual errors from 24 h postexercise onwards were attributed to muscle soreness from the exercise. 5. In support of this view, a similar pattern of matching errors was observed when an unexercised arm was made sore by injection of hypertonic saline into the biceps. 6. It is concluded that muscle soreness can interfere with a subject's ability to match forces, perhaps as a result of a reduced excitability of motor cortex. It implies that muscle soreness may contribute to the weakness experienced after a period of unaccustomed eccentric exercise.

Electromyography↗