Somatosensory Flashcards
1
Q
why is touch important?
A
- Sensory deprivation (esp. mechanosensory) is associated with problems such as impaired growth and cognitive development, as well as an elevated incidence of serious infections and attachment disorders (Frank et al., 1996).
- Hopper and Pinneau (1957) found that 10 min of additional handling per day resulted in a significant reduction in regurgitation.
- Casler (1967) reported that institutionalized infants receiving an additional 20 min of tactile stimulation per day for 10 weeks had higher scores on developmental assessments.
- Isolate-reared rats were hyperactive, easily distracted on cognitive tasks. But if they received paintbrush stroking for 2 min eight times per day, they performed as well as maternally reared controls (Lovic & Fleming, 2004).
2
Q
what are the tactile receptors in the skin?
A
- Four types of receptor sensitive just to mechanical stimulation in glabrous (hairless) skin:
- Merkel’s discs
- Meissner’s corpuscles
- Ruffini’s corpuscles
- Pacinian corpuscles
- Hairy skin contains all these, except Meissner’s corpuscles.
- In some tasks, such as grasping and manipulation, all receptor types are active.
- In most tasks, pattern of activity across receptor types likely to be important.
3
Q
what is the Merkel (SA1) receptors?
A
- Respond to sustained pressure or low frequency (<5 Hz) vibration, and spatial deformation.
- Enable coarse texture, pattern and form perception.
- Densely packed on the fingertips (similar to cones in the fovea) and offer acuity.
4
Q
what is the pacinian corpuscules?
A
- Respond to very high frequencies of stimulation (40–400 Hz).
- Allow fine texture perception.
5
Q
what is the ruffini corpuscules?
A
- Very low dynamic/temporal sensitivity, but respond to sustained pressure and lateral skin stretch.
- Detect object motion and force due to skin stretching, and sensing of finger position.
6
Q
what is the meissner?
A
- Sensitive to high frequencies of skin deformation (5–40 Hz), and spatial deformation.
7
Q
who was wilder penfield?
A
- Canadian brain surgeon who treated epileptic patients.
- Would stimulate their brains before surgery to minimise side-effects.
- Mapped out the motor and somatosensory cortex.
- In 1951, he published “Epilepsy and the Functional Anatomy of the Human Brain”.
8
Q
what is the two point threshold?
A
- The two-point threshold is the shortest the distance required for you to recognise two points of contact.
9
Q
what are the pressure sensitivity threshold?
A
- You use different monofibres of different sizes/stiffness (see right) to measure how much pressure is required for the participant to feel something.
- Each monofibre allows you to apply a specific amount of pressure. It bends when the peak-force threshold has been achieved, and a relatively consistent force is continued by the filaments until they are either removed from the skin contact or are severely curved.
- The pressure sensitivity threshold corresponds to the minimal pressure required for participants to feel something.
10
Q
what is the localisation threshold?
A
- The localisation threshold is when the participants can just detect the two stimuli being presented in two different places.
11
Q
what is tactile recognition by active touch?
A
- Lederman and Klatzky (1987) examined how we actively interact with objects in our environment and proposed a set of Exploratory procedures (EPs).
- Which EPs are used and in which order depends on task and user’s hypothesis.
12
Q
what is tactile recognition by passive touch?
A
- Simple or familiar shapes can be recognised by passive touch.
- Johnson and Phillips (1981) applied raised letters to stationary fingertip and found that 30% of participants can correctly identified letter when the height was 3 mm, but over 80% when height was 8 mm.
13
Q
what did Jones at al. 2009 study?
A
- Jones et al. (2009) used tactors and presented participants with tactile patterns on their forearm.
- Participants were presented with different tactile pattern, see right. The numbers represent the sequence of 115Hz pulses that lasted 500ms before a 500ms gap.
- In this example, participants would be presented with upward moving pattern:
- Three pulses at the bottom lasting 500ms.
- 500ms gap
- Three pulses in the middle row lasting 500ms
- 500ms gap
- Three pulses in the top row lasting 500ms - Jones et al. (2009) found that the mean accuracies for:
- Up, up/right and up/left to be around 37%
- Left and Right to be 87%
- This showed that recognition for patterns moving across the arm is better than for patterns moving along the arm.
14
Q
what is the cutaneous rabbit?
A
- Geldard and Sherrick (1972) presented three tactors (A, B, and C) separated by 10 cm on forearms of participants:
- Five × 2ms pulses were presented at A
- 40–80ms gap
- Five × 2ms pulses were presented at B
- 40–80ms gap
- Five × 2ms pulses were presented at C - Spatiotemporal pattern of taps administered to the arm with templates showing how stimuli are typically perceived
15
Q
where does the cutaneous rabbit effect come from?
A
- Not in receptors between tactors because local anaesthetic does not stop rabbit.
- Blankenburg et al. (2006) measure the activation of S1 when presenting participants with three tactors A, B, C spaced along forearm.
- There were three conditions in their study:
- A, B then C stimulated in sequence
- rabbit effect was experienced
- A then C, without B.
- Participants still felt as though stimulation had occurred at B. This is called the illusory rabbit.
- A, then C, then A.
- no stimulation felt at B and no rabbit effect. - Blankenburg et al. (2006) found that the region in S1 that is active when B alone stimulated, is also active in Conditions 1 (rabbit) and 2 (illusory rabbit), but not in Condition 3 (control).
- They concluded that S1 involved in conscious experience of rabbit.
16
Q
what do we gain from touch?
A
- Light et al. (2005) showed that the reported frequency of physical contact (hugs) with partners was correlated with elevated oxytocin levels and lowered blood pressure in women.
- Oxitocin is related to pair-bonding behaviour of mammals (Uvnas-Moberg, 1996; Uvnas-Moberg & Eriksson, 1996) and it also has analgesic and reward properties.
17
Q
what is the correlation between massage and pain tolerance?
A
- Agren et al. (1995) found that massage-like stroking of rats’ abdomens raised plasma oxytocin levels. This was associated with enhanced tolerance of pain (as measured by latency to withdraw from heat or respond to mechanical stimulation).
18
Q
what are the correlations between grooming behaviour and endorphines?
A
- An association between grooming and endorphin release was demonstrated experimentally by Keverne et al. (1989) in talapoin monkeys and rhesus macaques (Martel et al., 1995; Graves et al., 2002).
- Endorphin plays a well understood role as part of the mechanisms of pain control (Stefano et al., 2000).
19
Q
what are the types of pain?
A
- Nociceptive pain – activation of nociceptive receptors
- Inflammatory pain – damage to tissues and inflammations to joints or by tumour cells
- Neuropathic pain – lesion or other damage to the nervous system
20
Q
what is the direct pathway model?
A
- Melzack and Wall (1965) showed that pain signals are sent directly from the skin to the brain
- But there exist other factors that can alter pain…
- Mental state…
- Focus of attention…
21
Q
what is the correlation between mental state and pain?
A
- Phantom limbs feel tingly and retain the shape of the lost limb.
- Patients perceive them as part of their body.
- Pain is common—often burning, cramping, or shooting; may be mild or severe.
- Typical sensations include:
- Clenched hand causing ache.
- Calf cramps in the leg.
- Searing toe pain like a red-hot poker.
- Phantom limb pain is very common among amputees:
- 72% experience it shortly after amputation
- 65% still have it after 6 months
- 60% after 2 years
- Only 7% of patients benefit from the 50+ available therapies in the long term.
22
Q
what are the causes of the phantom limb pain?
A
- Katz and Melzack (1990) have proposed that in addition to nerve deafferentation (and damage), there are somatosensory pain memories that may be revived after an amputation and can lead to phantom limb pain.
- They suggested that implicit and explicit memory both contribute to the experience of phantom limbs and phantom-limb pain.
23
Q
what is the treatment of phantom limb pain?
A
- Phantom limb pain remains a difficult-to-treat condition.
- Culp and Abdi (2022) reviewed the effectiveness of traditional pharmacologic treatment and neuromodulation therapies (e.g. spinal cord/motor cortex/deep brain stimulations), and found that the latter have proven to be highly effective with minimal side effect profiles.
24
Q
what did deWied & Verbaten 2001 study?
A
- participants were exposed to either pleasant, neutral or unpleasant pictures. A cold-pressor test (that caused pain) was administered simultaneously.
- Results revealed that pain tolerance scores were higher as a function of picture pleasantness.
- conducted a second experiment to examine the role of pain cues in the effects of negative affect on cold pressor pain: Participants were shown unpleasant pictures that either did or did not include pain-related material.
- Participants who viewed pictures without pain cues tolerated the cold water for a longer period of time than those who viewed pictures that contained pain-related information.
25
Q
what is the sensory discriminative dimension?
A
- The sensory-discriminative dimension, often referred to simply as ‘intensity’ or given the label ‘sensory’, includes the spatial, and temporal characteristics and quality of pain.
26
Q
what is the affective motivational dimension?
A
- The affective-motivational dimension, often referred to simply as ‘unpleasantness’ or given the label ‘affective’, captures how ‘bad’ or how ‘unpleasant’ the pain is. It also captures the motivational aspect of pain—the aspect that makes us want to take protective action.
27
Q
what are the sensory and affective components?
A
- These two dimensions of pain involve distinctneural pathways (Treedes et al., 1999; Eisenberger, 2012): Sensory components are shown in green and affective components in red.
28
Q
what is dymenorrhea?
A
- Dysmenorrhea is the medical term for menstrual pain.
- Primary: pain without an underlying condition
- Secondary: pain caused by conditions like endometriosis or fibroids
- Affects up to 95% of menstruating individuals.
- A leading cause of educational absenteeism, impacting attendance and participation.
- Only 11% of individuals across 16 countries seek help for dysmenorrhea (Armour et al., 2021).
- Barriers include low health literacy, stigma, embarrassment, and the belief that menstrual pain isn’t a serious issue.
- Some individuals normalize severe symptoms.
- Dysmenorrhea has a significant negative impact on academic performance at both school and university levels (Armour et al., 2019).
29
Q
what is social pain?
A
- Eisenberg (2012) suggested that experiences of social rejection, exclusion or loss are generally considered to be some of the most ‘painful’ experiences that we endure. Indeed, many of us go to great lengths to avoid situations that may engender these experiences (such as public speaking).
- Emerging evidence suggests that experiences of social pain — the painful feelings associated with social disconnection — rely on some of the same neurobiological substrates that underlie experiences of physical pain.
30
Q
what is the correlation between social exclusion and pain?
A
- Eisenberg et al. (2004) presented participants with two scenarios: one where they are included in a game of cyberball and another where they are excluded.
- They found increased activity in the dACC and AI (both associated with affective physical pain) when participants were excluded in a game of cyberball.
- Experiences of social pain rely on brain regions associated with the affective component of pain in order to warn against and prevent the dangers of social harm.
31
Q
what impact did empathetic support have on pain?
A
- Fauchon et al. (2017) investigated the influence of perceived empathetic or unempathetic feedback upon the pain responses of participants in a pain experiment.
- Subjects were placed in a positive or a negative condition where an “observer” expressed different degrees of understanding of the participants’ pain.
