Touch Perception
Perception
Factors affecting frequency discrimination of vibrotactile stimuli: implications for cortical encoding. (1/275)
BACKGROUND: Measuring perceptual judgments about stimuli while manipulating their physical characteristics can uncover the neural algorithms underlying sensory processing. We carried out psychophysical experiments to examine how humans discriminate vibrotactile stimuli. METHODOLOGY/PRINCIPAL FINDINGS: Subjects compared the frequencies of two sinusoidal vibrations applied sequentially to one fingertip. Performance was reduced when (1) the root mean square velocity (or energy) of the vibrations was equated by adjusting their amplitudes, and (2) the vibrations were noisy (their temporal structure was irregular). These effects were super-additive when subjects compared noisy vibrations that had equal velocity, indicating that frequency judgments became more dependent on the vibrations' temporal structure when differential information about velocity was eliminated. To investigate which areas of the somatosensory system use information about velocity and temporal structure, we required subjects to compare vibrations applied sequentially to opposite hands. This paradigm exploits the fact that tactile input to neurons at early levels (e.g., the primary somatosensory cortex, SI) is largely confined to the contralateral side of the body, so these neurons are less able to contribute to vibration comparisons between hands. The subjects' performance was still sensitive to differences in vibration velocity, but became less sensitive to noise. CONCLUSIONS/SIGNIFICANCE: We conclude that vibration frequency is represented in different ways by different mechanisms distributed across multiple cortical regions. Which mechanisms support the "readout" of frequency varies according to the information present in the vibration. Overall, the present findings are consistent with a model in which information about vibration velocity is coded in regions beyond SI. While adaptive processes within SI also contribute to the representation of frequency, this adaptation is influenced by the temporal regularity of the vibration. (+info)Stimulus dependence of barrel cortex directional selectivity. (2/275)
Neurons throughout the rat vibrissa somatosensory pathway are sensitive to the angular direction of whisker movement. Could this sensitivity help rats discriminate stimuli? Here we use a simple computational model of cortical neurons to analyze the robustness of directional selectivity. In the model, directional preference emerges from tuning of synaptic conductance amplitude and latency, as in recent experimental findings. We find that directional selectivity during stimulation with random deflection sequences is strongly dependent on the mean deflection frequency: Selectivity is weakened at high frequencies even when each individual deflection evokes strong directional tuning. This variability of directional selectivity is due to generic properties of synaptic integration by the neuronal membrane, and is therefore likely to hold under very general physiological conditions. Our results suggest that directional selectivity depends on stimulus context. It may participate in tasks involving brief whisker contact, such as detection of object position, but is likely to be weakened in tasks involving sustained whisker exploration (e.g., texture discrimination). (+info)Prefrontal cortex and somatosensory cortex in tactile crossmodal association: an independent component analysis of ERP recordings. (3/275)
Our previous studies on scalp-recorded event-related potentials (ERPs) showed that somatosensory N140 evoked by a tactile vibration in working memory tasks was enhanced when human subjects expected a coming visual stimulus that had been paired with the tactile stimulus. The results suggested that such enhancement represented the cortical activities involved in tactile-visual crossmodal association. In the present study, we further hypothesized that the enhancement represented the neural activities in somatosensory and frontal cortices in the crossmodal association. By applying independent component analysis (ICA) to the ERP data, we found independent components (ICs) located in the medial prefrontal cortex (around the anterior cingulate cortex, ACC) and the primary somatosensory cortex (SI). The activity represented by the IC in SI cortex showed enhancement in expectation of the visual stimulus. Such differential activity thus suggested the participation of SI cortex in the task-related crossmodal association. Further, the coherence analysis and the Granger causality spectral analysis of the ICs showed that SI cortex appeared to cooperate with ACC in attention and perception of the tactile stimulus in crossmodal association. The results of our study support with new evidence an important idea in cortical neurophysiology: higher cognitive operations develop from the modality-specific sensory cortices (in the present study, SI cortex) that are involved in sensation and perception of various stimuli. (+info)Measures of individual differences in taste and creaminess perception. (4/275)
(+info)Mechanical resonance enhances the sensitivity of the vibrissa sensory system to near-threshold stimuli. (5/275)
(+info)Magnitude estimation of softness. (6/275)
(+info)Dynamic translation of surface coarseness into whisker vibrations. (7/275)
(+info)Intermodal event files: integrating features across vision, audition, taction, and action. (8/275)
(+info)Touch perception, also known as tactile perception, refers to the ability to perceive and interpret sensations resulting from mechanical stimulation of the skin and other tissues. This sense is mediated by various receptors in the skin, such as Meissner's corpuscles, Pacinian corpuscles, Merkel's disks, and Ruffini endings, which detect different types of stimuli like pressure, vibration, and texture.
The information gathered by these receptors is transmitted to the brain through sensory neurons, where it is processed and integrated with other sensory information to create a coherent perception of the environment. Touch perception plays a crucial role in many aspects of daily life, including object manipulation, social interaction, and the appreciation of various forms of sensory pleasure.
In the context of medicine and psychology, perception refers to the neurophysiological processes, cognitive abilities, and psychological experiences that enable an individual to interpret and make sense of sensory information from their environment. It involves the integration of various stimuli such as sight, sound, touch, taste, and smell to form a coherent understanding of one's surroundings, objects, events, or ideas.
Perception is a complex and active process that includes attention, pattern recognition, interpretation, and organization of sensory information. It can be influenced by various factors, including prior experiences, expectations, cultural background, emotional states, and cognitive biases. Alterations in perception may occur due to neurological disorders, psychiatric conditions, sensory deprivation or overload, drugs, or other external factors.
In a clinical setting, healthcare professionals often assess patients' perceptions of their symptoms, illnesses, or treatments to develop individualized care plans and improve communication and adherence to treatment recommendations.
Therapeutic Touch (TT) is a non-invasive therapy that practitioners use to help promote physical and emotional well-being. It's based on the idea that human beings are energy fields that can be manipulated to facilitate healing. Here's a medical definition:
Therapeutic Touch is a contemporary energy therapy that incorporates the intentional and sensitive use of universal energy for the purpose of facilitating the physical, emotional, mental, and spiritual well-being of the client. Practitioners consciously use their hands within the client's energy field to identify areas of imbalance, congestion, or depletion and facilitate the flow of energy to restore balance and harmony. (Adapted from Nurturing the Spirit Through Therapeutic Touch, by Dolores Krieger & Dora Kunz, 1985)
It's important to note that while some people report positive experiences with TT, its effectiveness is not universally accepted within the medical community. Some studies have suggested benefits, but more rigorous research is needed to establish its therapeutic value conclusively.