Two Point Discrimination

Not everyone has the same quality of tactile sensibility throughout their entire body. This might be because the person might have a disability , disorder or perhaps they have had an amputated limb . Also , it could be due to any physical flaws such as any previous scars or burns . In order to know how these disabilities or physical flaws have affected their tactile sensibility they would need to be compared to the tactile sensibility of those who have no disabilities or physical flaws by using a functional test called two point discrimination.

Two point discrimination is used to measure the ability of an individual to sense the two point stimuli that are presented at the same time. This is testing the quality of their tactile sensibility (Wolny et al. ,2016) . The sensory receptors in an individual's body are what respond to any stimuli that are presented and transmit that data to the brain. These receptors are located everywhere throughout the body including skeletal muscles, bones, joints and even skin (Alsaeed et al. , 2014).

There have been multiple studies presented where the two point discrimination test is used to examine those with disorders , disabilities or skin flaws such as scars or burns but there are only quite some few about how the functional test is being used to measure the tactile sensibility of normal healthy adults. Both individuals who are and are not presented with disabilities or disorders should be examined in order to acknowledge the normal values of tactile sensibility.

Some studies involve clinical patients such as inpatients and outpatients . Sarkar and colleagues examined where the TPD was lost and if there were any other sensory changes located in the upper limbs of diabetic patients (type 2). A cross sectional design was administered in this study and controlled in a hospital (2011). There were 15 participants with type 2 diabetes, participants diagnosed with neuropathy were excluded from the analysis. Results showed that TPD can be used to predict upper limb neuropathy in patients with type 2 diabetes without using normative values from normal healthy adults.

Studies have not only have been administered on clinical patients but also on students. Alsaeed and colleagues examined these students in order to generate normative values using TPD for the skin areas of the dominant hand (2014) There were 270 randomly selected students who had a background of arts and design as well as a background of medical and literacy. Results showed that those who had a background of arts and design had better discriminatory sensations than those who had a medical and literacy background . This shows that an individual's background can show an effect on their tactile sensibility.

Similar to this study , Wolny and colleagues presented a sample of 140 healthy individuals compared to 132 individuals with Carpal Tunnel Syndrome . The aim was to compare the two point discrimination senses as well as the kinesthetic senses or dysfunctions in participants diagnosed with Carpal Tunnel Syndrome to those of the healthy individuals . The results of the t-test for independent samples revealed that there were significant disturbances that occurred with the participants who were diagnosed with Carpal Tunnel Syndrome in the TPD sense and kinesthetic sense or dysfunction of the strength and motion when compared to those in healthy participants (Wolny et al. , 2016).

Another study whose participants were students was run by Koo and colleagues . There were 128 females and 128 males who were from Korea in their 20's . Those who had cutaneous disorders , scars , burns , dermal hypersensibility or neurological deficits were excluded (2016) . An independent samples t-test was used to show the effect of TPD between females and males . The results showed that women posses more TPD ability than men.

Continuing to generate normative values of TPD in more recent studies Won and colleagues also have reported normative values of TPD in the forehead , cheek , mentum , upper lip , lower lip and tongue tip (2017) .This research showed a significant effect size , gender and test modality on TPD values . More particularly , women showed lower TPD values than those of men. These findings are compared to findings from those whom are diagnosed with a disability or disorder to exam the significant effect.

Seeing how important it is to examine those who are normal young adults , this current experiment aimed to measure where TPD was lost in normal healthy students and particularly on the right side of the participants body regions such as the back of the tricep , inner forearm , cheek , and upper lip were all examined . An aesthesiometer was used to help record and indicate the TPD values . A within subjects design was administered since all the participants were tested in all of the conditions . A repeated measures ANOVA was used to analyze any differences among the body parts .

Methods

Subjects

Eighteen Queens College students , enrolled in a second level experimental design course on Tuesdays and Thursdays afternoons , participated in this project for a course credit . Among eighteen participants , there were 5 males and 13 females who ranged in age from 20 to 30 years old . This was a diverse sample that included (11%) African Americans (11%) , Asian (39%) , Caribbean (6%) , Caucasian (22%) and Hispanic (22%) .

Materials

Each pair received a brand new aesthesiometer which were used to probe the skin . A piece of looseleaf and a writing tool were provided by the students and used to record where two point discrimination was lost on four regions of the body ; back of the tricep , inner forearm , cheek and upper lip . A computer with Ethernet access was used to access the SPS software in order to analyze the results .

Procedure

A within subjects design and a repeated measures ANOVA were used to test the body regions ; the back of the tricep , inner forearm , cheek and upper lip and detect where two point discrimination was lost . The independent variable had four levels of body regions ; the back of the tricep , inner forearm , check and upper lip , only the right side of the body was tested . We received aesthesiometer to determine with pressure where the two point discrimination was lost . Subjects received a visual demonstration of TPD . The visual demonstration was performed on the left side of the body to avoid any interference with the experiment and results . Certain criteria was specified for each initial probe placement as follows ; back of the right tricep fully opened (10 cm) , the right inner forearm placement (10 cm) , the right cheek opened to (5 cm) and the right upper lip had an initial starting point (2 cm) . After the aesthesiometer was placed initially onto given body region , the aesthesiometer was closed by cm until the participant reported only 1 probe touched their skin . As we performed the experiment , in each pair the subjects alternated between being the experimenter and the participant after each body region was completed for the pair . The participant playing subject sat in a relaxed position with their eyes closed to avoid visual stimulation . The experimenter measured , using the aesthesiometer , and recorded on paper where two point discrimination was lost . When all subjects were measured on all four body regions the experiment was considered to be ended . All data was collected and submitted into the SPSS software and analyzed the results .

Results

Figure 1 shows the direction of effect that was significant from least to most sensitive.
A repeated measures ANOVA revealed that there was a significant effect of body region on where two point discrimination was lost among all the body parts tested . ( F(3,14) = 75.55 , p= 0.0000000006 , ?· 2 = .82 ) . Further analysis using a Post Hoc test showed all pairwise comparisons to be significant (p= .0001) with one exception , the tricep compared to the forearm (p= .02) . A linear effect demonstrated the right tricep (M= 62.78 SD= 5.29) was least sensitive (p= 0.0001) followed by the right inner forearm (M= 51.94 SD= 4.11) , the right cheek (M= 20.83 SD= 2.15) and finally significantly most sensitive was the upper right lip (M= 4.83 SD= 1.10) .

Discussion

By examining the effect of TPD on normal healthy young adults the results were as predicted . There was a significant difference among all body regions that were tested . Particularly the upper right lip compared to the right tricep . Similar to the Won et al. it was reported that both the female and male had significant different TPD values amongst themselves . Although gender effects were not analyzed here , resulting in an unequal distribution of male and female participants were measured and therefore under represents males . Some factors that could have affected the results include the temperature in the room , some subjects reported feeling cold , the amount of students who participated and the fact that they were all college students may have altered results . In regards to the pressure , some experimenters might've been too gentle with the aesthesiometer or even too harsh . The expectancy of knowing that there were 2 probes on the aesthesiometer might've also thrown the participants off affecting the TPD values . Previous studies had examined participants with disabilities or skin flaws such as burns or scars , the Queens College students had no reported disabilities and none were taking medication that might have affected the results of the TPD values . It was important to generate these normative values so that they can be compared to the findings in these previous studies were the participants have disabilities or disorders . This will predict or show the significant effect on tactile sensibility due to their disability or disorder , as well as any skin flaw they might have .

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