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At least 577 records · Page 32Linked to original sources
PubMed2001

Illusions in reading maps by touch: reducing distance errors.

The study reports systematic distance errors in reading raised-line maps by touch, and how they can be reduced. We show that T-shaped road junctions produce the typical error due to overestimating the length of the bisecting road compared to the bisected road. The error was not reduced when the target location was marked initially by a symbol. However, it was eliminated by instructions to use both hands concurrently to scan the route relative to an external square frame surrounding the map layout and to the body midline. Road junctions, which resemble 'Müller-Lyer' configurations, produced a significant overestimation of the length of a road that ended in diverging side roads relative to underestimating a road section with converging side roads. Spatial anchor cues from landmarks along the route, either alone or in conjunction with the spatial frame instructions, eliminated the illusion equally. We discuss theoretical implications, and the use of map frames and landmarks as spatial guides to improve map use by touch.

Adolescent↗
PubMed2006

Layer-specific touch-dependent facilitation and depression in the somatosensory cortex during active whisking.

Brains adapt to new situations by retuning their neurons. The most common form of neuronal adaptation, typically observed with repetitive stimulations of passive sensory organs, is depression (responses gradually decrease until stabilized). We studied cortical adaptation when stimuli are acquired by active movements of the sensory organ. In anesthetized rats, artificial whisking was induced at 5 Hz, and activity of individual neurons in layers 2-5 was recorded during whisking in air (Whisking condition) and whisking against an object (Touch condition). Response strengths were assessed by spike counts. Input-layer responses (layers 4 and 5a) usually facilitated during the whisking train, whereas superficial responses (layer 2/3) usually depressed. In layers 2/3 and 4, but not 5a, responses were usually stronger during touch trials than during whisking in air. Facilitations were specific to the protraction phase; during retraction, responses depressed in all layers and conditions. These dynamic processes were accompanied by a slow positive wave of activity progressing from superficial to deeper layers and lasting for approximately 1 s, during the transient phase of response. Our results indicate that, in the cortex, adaptation does not depend only on the level of activity or the frequency of its repetition but rather on the nature of the sensory information that is conveyed by that activity and on the processing layer. The input and laminar specificities observed here are consistent with the hypothesis that the paralemniscal layer 5a is involved in the processing of whisker motion, whereas the lemniscal barrels in layer 4 are involved in the processing of object identity.

Action Potentials↗
PubMed2006

Encoding and decoding touch location in the leech CNS.

Spike times encode stimulus values in many sensory systems, but it is generally unknown whether such temporal variations are decoded (i.e., whether they influence downstream networks that control behavior). In the present study, we directly address this decoding problem by quantifying both sensory encoding and decoding in the leech. By mechanically stimulating the leech body wall while recording from mechanoreceptors, we show that pairs of leech sensory neurons with overlapping receptive fields encode touch location by their relative latencies, number of spikes, and instantaneous firing rates, with relative latency being the most accurate indicator of touch location. We then show that the relative latency and count are decoded by manipulating these variables in sensory neuron pairs while simultaneously monitoring the resulting behavior. Although both variables are important determinants of leech behavior, the decoding mechanisms are more sensitive to changes in relative spike count than changes in relative latency.

Action Potentials↗
PubMed1998

[Identification of the types of touching during nursing care in an outpatient service].

This study was realized in the outpatient ward of bone marrow transplantation. The sample consisted of 17 adult patients and six workers. The data was collected from October to December, 1996, being obtained through filming, decodification of the films, a questionnaire and interview with the workers. The purposes were to identify in what situations the different types occurred, and which regions of the body were involved. It was found that most of the touching was of the instrumental type. The regions touched were the thorax and upper limbs.

Adult↗
PubMed1998

[Touch: its actual use by nurses].

This study aims to verify the use of the touch by nurses according to LE MAY'S proposal (1986), as well as to verify when and why he uses it, according to his own perception. Thirty-seven nurses (20 teachers, 16 assistants and 01 who was attending a specialization course) were interviewed in September 1995 in the capital and other cities of the State of São Paulo, showing that the majority of the collected samples mentioned touch in an expressive manner, referring to using it mainly to demonstrate empathies and security on moments where patient's emotion were perceived.

Adult↗
PubMed2005

A field study of step-up exercises with touch for elderly people.

This study assessed step-up exercises appropriate for elderly persons (M age=70.7 yr., SD=7.0). The group did several exercises in 7 sessions per month (average participants per session was 14, SD=3). A 30-sec. chair-stand test (sit-to-stand), questionnaires on activities of daily living, and impressions of the exercises were examined. Activities of daily living were expected to differ on cluster analysis before and after exercise sessions. Each cluster was classified by basic and instrumental activities. The 30-sec. chair-stand test did not significantly improve. Subjects enjoyed doing exercises with touch. Appropriate exercises for elderly persons should promote activities of daily living. Functional movements with touch seem appropriate for maintaining physical fitness and social interaction.

Activities of Daily Living↗
PubMed1993

Comparison of touching behaviors of winners and losers in racquetball and tennis.

Similarities and differences in subjects' touching behaviors in two racquet sports, tennis (n = 50) and racquetball (n = 200), were examined to learn whether postcontest interactive ritual is observed for racquetball as for tennis (handshake?). Analysis confirmed the tennis handshake and significantly more physical contact between tennis than between racquetball players. No significant differences were noted in postcontest verbal contacts or in differential touching by winners and losers.

Adult↗
PubMed1994

Touch and vibrotactile neurons in a crotaline snake's trigeminal ganglia.

Thirty-five touch (M) neurons and 59 vibrotactile (V + M) neurons were recorded intrasomally in the trigeminal ganglion of a crotaline snake (the pit viper, Trimeresurus flavoviridis). The M neurons were excited by von Frey hair (5-10 mg) mechanical stimulation of the receptive field, and adapted slowly to a sustained stimulus. It was almost impossible to elicit 1:1 entrainment to sinusoidal movement. Vibration with touch was an adequate stimulus for the V + M neurons. The range of entrainment to sinusoidal movement was 5-300 Hz. Thresholds of V + M neurons to sustained mechanical stimulation could not be determined, but a response was obtained by stroking with a von Frey hair (5-10 mg). Receptive fields of both M and V + M neurons were found on the skin (scales) and the mucous membrane of the orofacial region. There was one receptive field of approximately 2 mm in diameter for each M or V + M neuron. The mean resting potentials (+/- SD) of M and V + M neurons were -57.0 +/- 5.1 mV (n = 26) and -63.7 +/- 8.2 mV (n = 49), respectively. Neurons of both modalities displayed no background discharge. The action potential of V + M neurons had a shorter mean duration than that of M neurons. The mean conduction velocities (+/- SD) of peripheral (and stem) axons of M and V + M neurons were 28.4 +/- 5.7 m/sec (n = 11) and 30.8 +/- 7.8 m/sec (n = 30), respectively. Recorded neurons were labeled with intrasomal horseradish peroxidase electrophoresis. V + M neurons had larger somata than M neurons. All axons of M and V + M neurons were myelinated and similar in diameter. M and V + M neurons had similar central projection patterns. The projection of the thick central axon divided into a thinner ascending fiber and a thick descending fiber at the entry zone of the root to the brainstem. The former ran ipsilaterally to the principal sensory nucleus of the trigeminal nerve (TPR), and the latter ran to the descending nucleus of the trigeminal nerve (TTD) and beyond, where terminal arbors and bouton swellings were observed. Smaller myelinated and unmyelinated collaterals were given off at right angles from the descending fiber of the central axon into the TTD. They projected more densely to the rostral part than to the caudal part of the TTD. All of these data were compared with data on warm-temperature neurons, previously obtained.

Afferent Pathways↗
PubMed2004

Comparison of pressure pain threshold, grip strength,dexterity and touch pressure of dominant and non-dominant hands within and between right-and left-handed subjects.

This study was done to evaluate differences in pressure pain threshold, grip strength, manual dexterity and touch pressure threshold in the dominant and non-dominant hands of right- and left-handed subjects, and to compare findings within and between these groups. Thirty-nine right-handed and twenty-one left-handed subjects participated in the study. Pressure pain threshold was assessed using a dolorimeter, grip strength was assessed with a hand-grip dynamometer, manual dexterity was evaluated using the VALPAR Component Work Sample-4 system, and touch pressure threshold was determined using Semmes Weinstein monofilaments. Results for the dominant and non-dominant hands were compared within and between the groups. In the right-handed subjects, the dominant hand was significantly faster with the VALPAR Component Work Sample-4, showed significantly greater grip strength, and had a significantly higher pressure pain threshold than the non-dominant hand. The corresponding results for the two hands were similar in the left-handed subjects. The study revealed asymmetrical manual performance in grip strength, manual dexterity and pressure pain threshold in right-handed subjects, but no such asymmetries in left-handed subjects.

Adult↗
PubMed2006

See what you've done! Active touch affects the number of perceived visual objects.

Previous research has shown that visual perception is affected by sensory information from other modalities. For example, sound can alter the visual intensity or the number of visual objects perceived. However, when touch and vision are combined, vision normally dominates--a phenomenon known as visual capture. Here we report a cross-modal interaction between active touch and vision: The perceived number of brief visual events (flashes) is affected by the number of concurrently performed finger movements (keypresses). This sensorimotor illusion occurred despite little ambiguity in the visual stimuli themselves and depended on a close temporal proximity between movement execution and vision.

Adult↗
PubMed2002

A crossmodal attentional blink between vision and touch.

There is currently a great deal of interest regarding the possible existence of a crossmodal attentional blink (AB) between audition and vision. The majority of evidence now suggests that no such crossmodal deficit exists unless a task switch is introduced. We report two experiments designed to investigate the existence of a crossmodal AB between vision and touch. Two masked targets were presented successively at variable interstimulus intervals. Participants had to respond either to both targets (experimental condition) or to just the second target (control condition). In Experiment 1, the order of target modality was blocked, and an AB was demonstrated when visual targets preceded tactile targets, but not when tactile targets preceded visual targets. In Experiment 2, target modality was mixed randomly, and a significant crossmodal AB was demonstrated in both directions between vision and touch. The contrast between our visuotactile results and those of previous audiovisual studies is discussed, as are the implications for current theories of the AB.

Adult↗
PubMed1998

Cross-modal links in exogenous covert spatial orienting between touch, audition, and vision.

Three experiments investigated cross-modal links between touch, audition, and vision in the control of covert exogenous orienting. In the first two experiments, participants made speeded discrimination responses (continuous vs. pulsed) for tactile targets presented randomly to the index finger of either hand. Targets were preceded at a variable stimulus onset asynchrony (150, 200, or 300 msec) by a spatially uninformative cue that was either auditory (Experiment 1) or visual (Experiment 2) on the same or opposite side as the tactile target. Tactile discriminations were more rapid and accurate when cue and target occurred on the same side, revealing cross-modal covert orienting. In Experiment 3, spatially uninformative tactile cues were presented prior to randomly intermingled auditory and visual targets requiring an elevation discrimination response (up vs. down). Responses were significantly faster for targets in both modalities when presented ipsilateral to the tactile cue. These findings demonstrate that the peripheral presentation of spatially uninformative auditory and visual cues produces cross-modal orienting that affects touch, and that tactile cues can also produce cross-modal covert orienting that affects audition and vision.

Adolescent↗
PubMed1999

Similar mechanisms underlie curvature comparison by static and dynamic touch.

In four experiments, we tested whether haptic comparison of curvature ranging from -4/m to +4/m is qualitatively the same for static and for dynamic touch. In Experiments 1 and 3, we tested whether static and dynamic curvature discrimination are based on height differences, attitude (slope) differences, curvature differences, or a combination of these geometrical variables. It was found that both static and dynamic hepatic curvature discrimination are based on attitude differences. In Experiments 2 and 4, we tested whether this mechanism leads to errors in the comparison of stimuli with different lengths for static and dynamic touch, respectively. If the judgments are based on attitude differences, subjects will make systematic errors in these comparisons. In both experiments, we found that subjects compared the curvatures of strips of the same length vertically, whereas they made systematic errors if they were required to compare the curvatures of strips of different lengths. Longer stimuli were judged to be more curved than shorter stimuli with the same curvature. We conclude that similar mechanisms underlie static and dynamic haptic curvature comparison. Moreover, additional data comparison showed that static and dynamic curvature comparison is not only qualitatively, but also quantitatively similar.

Humans↗
PubMed1992

The effect of orientation on tactual braille recognition: optimal touching positions.

Subjects in five experiments matched tangible braille against a visible matching code. In Experiment 1, braille recognition suffered when entire lines of braille characters were tilted in varying amounts from the upright. Experiment 2 showed that tilt lowered performance for tangible, large embossed letters, as well as for braille. However, recognition was better for print letters than it was for braille. In Experiment 3, subjects attempted to match the upright array against embossed braille that was left/right reversed, inverted up/down, or rotated +180 degrees. Performance was close to that for normal braille in the left/right reversal condition, and very low for the +180 degrees rotation group. These results on braille tilt in the "picture plane" may reflect difficulty in manipulating the tangible "image." Braille recognition performance was not lowered when the visible matching array was tilted -45 degrees or -90 degrees from the upright but the tangible stimuli were upright. In Experiment 4, recognition of left/right reversed braille that was physically horizontal (on the bottom of a shelf) was compared with that of braille left/right reversed due to its location on the back of a panel, in the vertical plane. Braille recognition accuracy was higher with braille located vertically. An additional experiment showed the beneficial effect of locating braille in the vertical, frontoparallel plane, obtained with +90 degree rotated braille. It is proposed that optimal tactual performance with tangible arrays might depend on touching position, and on the physical position of stimuli in space. Just as there are good and poor viewing positions, there may be optimal touching positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed2001

Prolactin in rats is attenuated by conspecific touch in a novel environment.

Prolactin is released in response to physical and psychological stress, the latter of which involves an animal's interpretation of its environment as potentially dangerous. This interpretation might be altered by social buffering, as defined by the presence of a social partner. In support of this claim, I previously found that the presence of a conspecific during exposure to the open field caused lower levels of prolactin in juvenile rats than did exposure to the open field alone. Because testing with a conspecific allowed the animals to touch, physical contact may have been necessary for the reduction of prolactin. To test this hypothesis, juvenile male and female rats in the present study were exposed to the open field (1) alone, (2) with a conspecific separated by a Plexiglas partition, or (3) with a conspecific without a partition. Touch was necessary to reduce stress as measured by prolactin levels.

Adaptation, Psychological↗
PubMed2004

Perceiving object motion using vision and touch.

In a previous experiment, we showed that bistable visual object motion was partially disambiguated by tactile input. Here, we investigated this effect further by employing a more potent visuotactile stimulus. Monocular viewing of a tangible wire-frame sphere (TS) rotating about its vertical axis produced bistable alternations of direction. Touching the TS biased simultaneous and subsequent visual perception of motion. Both of these biases were in the direction of the tactile stimulation and, therefore, constituted facilitation or priming, as opposed to interference or adaptation. Although touching the TS biased visual perception, tactile stimulation was not able to override the ambiguous visual percept. This led to periods of sensory conflict, during which visual and tactile motion percepts were incongruent. Visual and tactile inputs can sometimes be fused to form a coherent percept of object motion but, when they are in extreme conflict, can also remain independent.

Cues↗
PubMed1994

Nutritional intake. Use of touch and verbal cuing.

1. Many hospitalized elderly patients have inadequate nutritional intake. 2. Inexpensive, practical means of improving the nutritional status of elderly patients are needed. 3. Touch, verbal cuing, and the combination of touch and verbal cuing may be effective methods for increasing the nutritional intake of hospitalized elderly patients without severe cognitive dysfunction.

Aged↗
PubMed1995

Elderly residents: perceptions of nurses' comforting touch.

1. Elderly nursing home residents often feel unwanted or unloved because of a lack of physical contact with others or their caregivers' inability to communicate love and belonging. 2. In a study of 25 elderly nursing home residents, it was found that those who were subjected to comforting touch by their nurses perceived an increased feeling of affection and immediacy. 3. The conscious and intentional use of comforting touch by nurses and caregivers to elderly nursing home residents should be encouraged because of its beneficial effect of conveying love and belonging.

Aged↗