Brain Perception Representation Of Fabric Contact Pressure Comfort Based On FMRI

The comprehensive expression of the pressure,squeeze and friction caused by the contact of the fabric with human skin in the brain was perception.The application of functional Magnetic Resonance Imaging(fMRI),a modern medical imaging technology,in the field of brain perception had proved that it had ultra-high spatial and temporal resolution and unique expression of skin touch perception.It provided a new practical method for explainning objective characterization and cognitive mechanism of the contact comfort in the field of textile material and engineering,and provided a specific and standard method for the objective,scientific,accurate and quantitative physiological characterization of the pressure comfort of fabric contact.Therefore,it made up for the inherent theoretical defects of the traditional psychological quantitative evaluation system,physical-mechanical evaluation system and indirect physiological evaluation system of effectors.In textile actual use process,the vast majority of the fabric were all contact with the human body,in the process of fabric contact pressure comfort evaluation,the areas of waist and abdomen located below the chest which covered important visceral section were the most sensitive to stress tolerance.In order to judge and analyze the neural activity response of the human brain and the direction of somatosensory information flow when the human body was stimulated by different degrees of fabric contact pressure stimulation,this paper utilized the advanced fMRI technology to observe the brain sensory information of seven women volunteers when their waist and abdomen were stimulated by increasing contact pressures from high elastic fabrics.In addition,a variety of brain image processing tools such as SPM,Anatomy,AAL,Marsbar,Xjview and BrainNet Viewer were used to carry out targeted data processing on brain perception images.The so called targeted data processing were referred to the results of the analysis of the topic were not aimed at the whole brain analysis,but for the brain regions(Primary sensory cortex SI,Second sensory cortex SII and Insula IN)involved in the transmission of somatosensory information and related to the somatosensory perception of fabric contact pressure in view of the present literature,contact pressure pain perception brain regions(Amygdala brain area AMYG),and joy and happiness felt brain regions(Precuneus PQ)for the analysis of brain regions.The design method of block was use in this topic,the subjects were asked to repeat the static-pressure stimulation process three times in a time series,activation intensity value and the number of activated voxels(activation range)could be viewed as evaluation indexes.the activation intensity value was converted from the difference of cerebral blood-oxygen level dependent signal(BOLD)between in the pressure stimulation state and in the resting state by the general linear model.The so-called positive activation referred to the fact that,in this brain region,the blood-oxygen level dependent signal(BOLD)under the textile pressure stimulation was higher than that in the resting state,which was the result of the comprehensive effect of the stimulation to promote the local cerebral blood flow in this brain region,while the negative activation was the opposite.The results of functional magnetic resonance(fMRI)experiments under the stimulation of gradually pressurized fabric showed that,when the contact pressure of the fabric was lower than the threshold value of comfortable contact pressure,the brain areas of the subjects were mainly negatively activated,and the negative activation peak point and the negative activation range were the largest in the central posterior gyri region of the primary sensory cortex I-POST.When the contact pressure of the fabric was within the threshold of comfortable contact pressure,the activation in the brain of the subject was mainly positive,and the peak point and range of positive activation in the central posterior gyri of the secondary sensory cortex were the highest.When the contact pressure of the fabric exceeded the comfort threshold of the contact pressure of the waist and abdomen of the human body,the activation in the brain of the subject changed back to negative activation,but the maximum negative activation peak point and negative activation intensity transferred to the amygdala brain area AMYG.The results showed that,on the one hand,the contact pressure stimulation of the fabric promoted the flow of somatosensory information from the primary sensory cortex to the secondary sensory cortex and then to the amygdala brain region with the increase of fabric pressure.On the other hand,it indicated that either shallow surface contact under low pressure or deep oppressive contact under high pressure would produce negative perception in human brain dominated by inhibitory effect,namely discomfort perception.The difference was that the negative discomfort perception under low contact pressure was mainly projected to the primary sensory cortex,while the negative pressure perception under high contact pressure was mainly projected to the amygdala brain region And only when the appropriate fabric contact pressure,to give priority to the positive effect of human brain promote effect,namely comfort perception,and its main projection area was located in the secondary sensory cortex.The reason for its negative discomfort was that under excessive oppression of the fabric,the local cerebral blood flow decreased and the oxygen consumption rate was higher than the oxygen supply rate,leading to the decrease of neural activity and negative activation in brain imaging.However,under the action of too small fabric pressure,the velocity of cerebral blood flow increased slowly,but the oxygen consumption of nerve activity was too large,resulting in the oxygen consumption was greater than the oxygen supply,which would also inhibit the nerve activity and present negative activation.The functional magnetic resonance imaging test under the stimulation of constant elongation fabrics verified the correctness of the inference of the pressure test of gradually increased fabric,and the correlation analysis of the brain activation index under the stimulation of constant elongation fabric and the physical factors of fabric found that:The perceived intensity of low-pressure discomfort in the central posterior gyrus of the primary sensory cortex I-POST was mainly affected by the surface roughness and the constant stress elastic response rate,while the perceived range of low-pressure contact discomfort was mainly affected by the stress relaxation rate.The rougher the surface of the fabric and the higher the elastic recovery rate were,the stronger the perceived signal strength of the low-pressure contact discomfort of I-POST would be,and the larger the fabric relaxation rate were,the wider the perceived signal range of the low-pressure contact discomfort of I-POST would be.The intensity and range of the contact comfort signal of the central posterior gyri of the secondary sensory cortex II-POST were mainly affected by the mean variance of surface friction coefficient and elastic modulus.The more uniform the fabric surface and the greater the elastic modulus,the stronger and wider the comfort sensing signal intensity of II-POST would be.The intensity and range of discomfort sensing signals of contact oppression in the amygdala brain region were mainly affected by the surface roughness and the response rate of constant stress elasticity.The rougher the surface of the fabric and the worse the resilience,the stronger and wider the intensity and range of discomfort sensing signals of oppression in the amygdala brain region.Correlation analysis of brain signal change index and physical factors under the stimulation of constant elongation fabric found that:The SI and AMYG brain regions focused on the stress change of the fabric,while the SII brain regions focused more on the surface properties of the fabric.After brain regions were refined according to function,the fast adaptive sensing brain region BA1 and slow adaptive sensing brain region BA3 a of the primary sensory cortex were affected by stress and transverse modulus of elasticity respectively,showing high linear negative correlation and linear positive correlation.That was,under certain contact pressure,the smaller the fracture stress and the higher the transverse modulus of the fabric were,the more attention was paid to the brain regions of BA1 and BA3 a.In the secondary sensory cortex,Parietal Operculum 1 brain region OP1 was mainly affected by the surface roughness,and showed a positive linear correlation,that was,under the contact pressure stimulation of the same elongation,a tactile pressure stimulus with a rough surface fabric would attract a higher attention to the OP1 brain area.