HHF Part9 - Hand Function Across the Lifespan

Part 9 Hand Function Across the Lifespan

08/22/2024

"Physical Aspects Pertaining to Hand Development"

Early Hand Development and Growth:

• Anatomical Development: The hand's anatomical features are defined by 10 weeks of gestation, and a primitive grasp reflex appears by 12 weeks (e.g., Brown, Omar, & O'Regan, 1997).
• Growth: By age 18 years, the size of an infant's hand increases by 200-300% in length and width (e.g., Flatt & Burmeister, 1979). This growth affects the child's ability to manipulate objects and whether they need one or two hands for grasping (e.g., Newell, McDonald, & Baillargeon, 1993).

Neural and Sensory Maturation:

• Myelination: Myelination of the central nervous system progresses from sensory areas to the motor cortex, with full myelination of corticospinal fibers occurring around 8-10 years (e.g., Müller, Hömberg, & Lenard, 1991). This affects the speed of neural conduction; for instance, conduction velocity in the neonatal spinal cord is about 10 m/s, increasing to adult levels of 50-70 m/s by age 8 (e.g., Khater-Boidin & Duron, 1991).
• Sensory Pathways: Sensory fibers in the median and ulnar nerves reach adult conduction velocities by 12-18 months (e.g., Desmedt et al., 1973). The speed of these pathways impacts reflex responses, such as grip adjustments when objects begin to slip.

Age-Related Changes in Skin and Sensory Receptors:

• Mechanoreceptors: Older adults experience a reduction in mechanoreceptors like Meissner's and Pacinian corpuscles. For example, Meissner's corpuscles decrease by 23-34% from age 22 to 78 (e.g., Bruce, 1980). Pacinian corpuscles also decrease or remodel with age (e.g., Cauna, 1965).
• Skin Changes: The skin on the dorsum of the hand becomes thinner and drier with age due to decreased sweat gland output. The decreased sweat gland output may reduce the friction between hand and object and
  potentially increases the risk of objects slipping from the grasp (e.g., Roberts, Andrews, & Caird, 1975; Silver et al., 1965).

Musculoskeletal Changes in the Elderly:

• Muscle Mass and Strength: Muscle mass declines by 25-45% with age, reducing maximum strength (e.g., Mathiowetz et al., 1985). This includes a loss of motor units and a shift to larger, slower motor units (e.g., Larsson & Ansved, 1995).
• Joint Changes: Aging often involves osteoarthritis and rheumatoid arthritis, affecting the joints and functional capacity of the hand (e.g., Carmeli et al., 2003).

 

"Tactile Sensing"

Pressure Sensitivity

• Decline with Age: Pressure sensitivity decreases as people age. For instance, research by Thornbury and Mistretta (1981) found a 1.4-fold decrease in pressure sensitivity across ages from 19 to 88 years. Bruce (1980) observed that older individuals (average age 72) were 2.5 times less sensitive at the little finger compared to younger individuals (18-20 years).
• Specific Findings: Older adults also show reduced sensitivity to single pressure indentations on the thenar eminence compared to younger adults (e.g., Kenshalo, 1986).

Vibrotactile Sensitivity

• General Decline: Vibrotactile sensitivity declines with age across all four psychophysical channels that mediate vibratory sensations (Gescheider et al., 1994). The decline is more pronounced in the Pacinian (P) channel than in the Meissner (NP I), Merkel (NP II), and Ruffini (NP III) channels.
• Sensitivity Differences: Younger participants (mean age 23.6 years) are more sensitive to vibrations than older participants (mean age 73.6 years). This decline is linked to reduced receptor density, particularly affecting the P channel, which integrates neural activity across many receptors (Cauna, 1965).
• Absolute vs. Relative Thresholds: Absolute difference thresholds (the smallest detectable difference in stimulus amplitude) increase with age, but relative difference thresholds (Weber fractions) do not show significant age-related changes, except near the absolute threshold. This indicates that although absolute sensitivity declines, relative sensitivity remains relatively stable (Gescheider et al., 1996).

Thermal Sensitivity

• Cold vs. Warm Sensitivity: Sensitivity to cold generally exceeds sensitivity to warmth at all ages (Stevens & Choo, 1998).
• Age-Related Decline: Thermal sensitivity decreases more in extremities (hands and feet) compared to central areas (face). For example, sensitivity to warmth and cold on the tip of the index finger and the thenar eminence decreases at different rates, with warmth decreasing slightly faster than cold (0.02°C vs. 0.014°C per year on the index finger) (Stevens & Choo, 1998).

Spatial Acuity

• Decline with Age: Spatial acuity, measured by two-point touch thresholds, declines with age. Gellis and Pool (1977) found that spatial acuity is highest in the third decade of life (30s) and lowest in the ninth decade (80s). This decline is evident at major hand locations: fingertips, thenar and hypothenar areas, and the dorsum.
• Specific Findings: Stevens and Patterson (1995; Stevens & Choo, 1996) confirmed that tactile spatial acuity on the fingertip decreases with age. They assessed acuity using various methods, including two-point gap discrimination, point localization, line-length discrimination, and line-orientation discrimination. All these measures showed a similar rate of decline, approximately 1% per year from ages 20 to 80.
• Acuity Dimensions: The sensitivity of the fingertip declines uniformly across different acuity dimensions (length, locus, orientation, gap), suggesting a common underlying mechanism, possibly related to the thinning of mechanoreceptor networks.

Temporal Acuity

• Effect of Age on Temporal Acuity: Van Doren, Gescheider, and Verrillo (1990) investigated how aging affects tactile temporal acuity using a temporal gap-detection task. They found that temporal acuity (the ability to detect brief gaps in vibratory stimuli) decreases with age, particularly for gaps of short duration (8 to 256 ms). The ability to detect gaps was better with sinusoids compared to noise.
• Differences by Stimulus Type: Temporal acuity was significantly affected by the type of stimulus. For noise, the acuity declined more sharply with age than for sinusoids. This suggests different underlying processes for detecting gaps with different types of stimuli.
• Mechanistic Insights: The study's results suggest that simple models of detection, like an integrator with a fixed time constant, do not fully explain the findings. Instead, models that account for temporal summation and multiple looks, such as the multiple look model, might better explain the observed changes in temporal acuity with age.

 

"Active Haptic Sensing" - Object Recognition and Classification

Early Development of Haptic Object Recognition:

• Children as young as 2.5 years can recognize objects by touch. For example, Bigelow (1981) showed that children could identify an average of 5.6 out of 7 common objects by touch at this age. By the age of 5, their recognition ability is nearly perfect.
• Studies, such as those by Morrongiello et al. (1994), show that both the speed and accuracy of haptic object recognition improve with age. Older children are better at recognizing objects, especially by focusing on diagnostic features.

Haptic vs. Visual Object Processing:

• Unlike visual processing, where young children tend to process objects globally (considering overall similarity), haptic processing tends to be more analytic (focused on specific features) across all age groups. For instance, Berger and Hatwell (1993, 1995, 1996) found that even 5-year-olds processed objects based on individual features like roughness or size rather than overall similarity.
• Adults use specialized exploratory procedures (EPs) that provide precise information about specific object properties, leading to more analytical processing. However, when integrating this detailed information, adults can still make global (overall similarity) judgments, but this occurs at a higher cognitive level.

Developmental Shifts in Processing Strategies:

• As children age, their haptic exploration strategies evolve. Younger children tend to use more global processing (considering the whole object), while older children and adults use more analytic processing (focusing on specific features).
• The preference for certain object features changes with age. Younger children might focus on roughness (texture), while older children and adults shift to considering size or shape, as seen in Berger and Hatwell's studies.

Challenges with Multiattribute Objects:

• Processing objects with multiple attributes (e.g., size, texture) poses a challenge, especially for younger children. Morrongiello et al. (1994) found that younger children often confuse objects based on global shape, while older children can also confuse local parts of the objects.
• Identification of miniaturized objects is particularly difficult for children, indicating that haptic recognition is influenced by object size. -> interesting

Importance of Comprehensive Understanding:

• A thorough understanding of how children process multiattribute objects is crucial for developing accurate models of haptic object processing. Variability in research findings may stem from differences in experimental tasks and inconsistent definitions of key concepts like "global" and "analytic" processing.

Maybe a robot can also gradually learn how to recognize common objects? global attribute first -> local attribute later. roughness first , size / shape after

 

"Active Haptic Sensing"  - Perceiving Properties of Surfaces and Objects

Texture, Compliance, Temperature, Weight

• Haptic Texture Perception:
  • Early Sensitivity: Infants as young as 6 months can differentiate between coarse textures through touch. For example, Bushnell and colleagues observed that infants showed different behaviors when exploring textured versus smooth surfaces, indicating sensitivity to texture differences.
  • Earlier Onset: More recent studies suggest that infants may begin to perceive texture as early as 4 months. For instance, Morange-Majoux et al. (1997) found that 4- to 5-month-old infants actively explored texture differences using a lateral motion technique, which is optimal for texture discrimination. Additionally, Molina and Jouen (2003) demonstrated that even neonates (3–5 days old) might distinguish between different textures, although the role of visual input cannot be completely excluded.
• Haptic Perception of Compliance, Temperature, and Weight:
  • Compliance (Object Hardness/Flexibility): Infants around 6 to 7 months can haptically differentiate hard objects from flexible ones. For example, Gibson and Walker (1984) showed that 12-month-old infants responded differently to rigid and flexible objects by squeezing the flexible ones and banging the rigid ones. The ability to perceive compliance is suggested to develop around 6 months, but there is uncertainty about whether younger infants can do so.
  • Temperature Perception: By 6 months, infants can differentiate objects that are warm or cool to the touch. For instance, Bushnell et al. (1985, 1989) demonstrated that infants touched unfamiliar temperature objects longer than familiar ones, indicating recognition through touch. However, studies have not yet explored thermal perception in infants younger than 6 months.
  • Weight Perception: The ability to perceive weight through touch appears to develop later than other haptic properties, emerging around 9 months at the earliest. Ruff (1982, 1984) and others found that older infants (9 to 12 months) showed different behaviors (e.g., banging) when handling objects of different weights. However, younger infants (6 months) did not display such weight discrimination.
• Developmental Changes in Weight Perception:
  • Size-Weight Illusion: Studies on children aged 2–10 years indicate that younger children are less susceptible to the size-weight illusion, where a smaller object of the same weight as a larger one feels heavier. Robinson (1964) found that the magnitude of this illusion decreases with age, suggesting that weight discrimination improves as children grow older. However, Pick and Pick (1967) reported that the illusion's magnitude actually increased with age from 6 to 16 years, possibly due to older children being more influenced by object volume or moment of inertia.
• Need for Further Research:
  • Gaps in Knowledge: The research highlights gaps in our understanding of haptic perception, particularly in younger infants and in the development of weight perception. There is a need for more studies to clarify these developmental trends and to explore how infants and young children perceive different object properties through touch.

Orientation, Size, Shape; I think there's not much interesting takeaway here

 

• Infant Haptic Perception: Infants can perceive size and basic shape differences through touch as early as 2-4 months, but configural shape perception develops later, around 15 months.
• Orientation Perception: No studies on haptic orientation perception in infants exist. Older children struggle more than adults with line orientation tasks.
• Developmental Timeline: Recent research shows that haptic shape perception begins much earlier than previously thought, challenging older theories by Piaget and others.
• Lifespan Haptic Perception: Haptic shape perception improves through childhood, peaks in early adulthood, and slightly declines with age.

 

Manual Exploration

 

• Manual Exploration in Infants: By 4 months, infants use manual exploration to perceive object boundaries and unity, with their hand movements adapting to different object properties like texture and shape.
• Developmental Link: The development of haptic perception in infants is closely tied to the motoric development of exploratory procedures (EPs), with infants' hand movements evolving to more precise methods, such as using fingertips by 6 months. -> worth noting
• Neonates' Capabilities: Neonates can differentiate coarse texture changes through reflexive grasps, although this may not involve true haptic perception of detailed object configurations.
• Tool Use in Preschoolers: By preschool age, children can make judgments about tool functionality using appropriate sensory modalities, such as touch for material properties (e.g., compliance) and vision for geometric properties (e.g., size).
• Haptic Object Recognition in Older Children: As children age, they become faster, more accurate, and more thorough in their manual exploration during haptic object recognition tasks.
• Research Gaps: There is limited research on the role of hand movements in haptic perception in children beyond infancy and in older adults.

 

 

"Prehension" - Reaching

 

• Early Development of Grasping:
  • Newborns exhibit basic hand movements, such as the grasp reflex, but these are often imprecise and not related to visual objects.
  • By 4-5 months, infants develop more voluntary control over reaching and grasping, with improved hand coordination and use of visual cues.
• Task Constraints and Grasping:
  • Grasping success in infants varies based on task constraints like object position, size, and the child’s posture.
  • Postural control influences reaching strategies; infants who can sit upright tend to use one hand for reaching, while those without postural control use both hands symmetrically.
• Refinement of Reaching Skills:
  • From birth to around 20 weeks, reaching skills gradually improve, with a transition from fragmented movements to smoother, more coordinated actions.
  • By 13 months, infants start adjusting hand aperture for object size, but this ability continues to develop and refine throughout childhood.

• Grasping and Hand Size:
  • The use of one or two hands for grasping depends on the size of the object relative to hand size, a pattern consistent across infants, children, and adults.
• Continued Development in Childhood:
  • Prehensile skills, including coordination between reaching and grasping, continue to develop and become more efficient during childhood.
  • By 12 years of age, children show better coordination and less reliance on visual cues when reaching for objects.
• Grasping in the Elderly:
  • Older adults exhibit longer movement durations and slower acceleration/deceleration during reach-to-grasp tasks, likely due to a more cautious movement strategy.
  • Despite slower movements, the coordination between reaching and grasping remains intact, with minimal age-related differences in kinematic patterns.

 

 

"Prehension" - Grasping

다 뻔한 거 같아서 이제 짧게 정리함. 

Overall Implications:

• In Children: The gradual refinement of prehensile abilities reflects the maturation of sensory and motor systems. This development allows for better force control and anticipatory adjustments based on sensory feedback.
• In the Elderly: The decline in grip strength and manual dexterity with age underscores the impact of both physiological changes in muscle and sensory systems and the necessity for greater safety margins in handling objects to prevent slips and drops.

 

"Psychometric Studies of Prehension"

Overall Implications:

• In Children: Standardized psychometric tests are useful in tracking the development of manual dexterity and identifying any developmental issues. There is a general trend of improved dexterity with age, although gender differences are evident.
• In the Elderly: Aging leads to a decline in manual dexterity, particularly noticeable in tasks requiring fine motor skills. However, an individual’s initial level of dexterity is a critical factor in determining the extent of decline, more so than their chronological age.

 

"Typing and Piano Playing"

Overall Implications:

 

• Non-Prehensile Movements: Age-related declines in motor speed and accuracy are common, but certain skills, especially those practiced regularly and at a high level, can be preserved well into older age.
• Specificity of Skill Preservation: Overlearned motor skills, such as typing and piano playing, show remarkable resistance to age-related decline, likely due to specific mechanisms that compensate for general processing limitations in older adults.

Some other takeaways that are interesting:

• Elderly: Studies on older adults (55–85 years) show that they maintain accuracy in pointing movements, regardless of how the target is perceived (visually or kinesthetically). This suggests that proprioception is relatively well-preserved in healthy older adults.

 

 

• Fitts' Law in Children: Fitts' Law, which relates movement time to the amplitude and accuracy requirements of a task, applies to children over 5 years old. As children age, their movement time decreases, indicating better control over muscle forces and improved accuracy.