HHF Part1 - Historical Overview and General Introduction

Part 1 Historical Overview and General Introduction

What are the two focuses of human hand function in 19th century?

1. Counting number of sensory modalities in hand

Early tactile concerns centered on issues related to determining the appropriate number of human sensory modalities and submodalities and to the varying sensitivity and spatial acuity of the skina cross the entire human body when stimulated by mechanical and thermal forms of energy.

2. Skin's sensitivity to applied pressure 

Another important focus during the late 19th century was the skin's sensitivity to applied pressure. The German physiologist Max von Frey (1896) invented two instruments that were used to study pressure sensitivity and the location of “touch” spots on the skin.

What are the two important findings of human hand function in 19th century?

1. Weight sensing is more precise when tacticle sensing is combind with lifting.

Weight discrimination is precise with touch alone (i.e., tactile sensing), it is always more exact if the weight is lifted by the hand (i.e., active haptic sensing). The ability to discriminate between weights of different mass by voluntary muscular exertion was termed a sense of force (Frey, 1914)

2. Proximal joints are more sensitive in detecting both active / passive movements

He found that the thresholds for detecting both active and passive movements were much smaller for more proximal joints, such as the shoulder, as compared to the distal finger joints.

How is the Goldscheider's experiment conducted? I don't know.

Maybe by moving a parcipant's limb using external forces while restraining the cataneous sensations.

What is the dualistic mindbody philosophy of Descartes? What is the physical magnitudes?

Dualism: Descartes proposed that reality consists of two fundamentally different kinds of substances:

• Mind (Res Cogitans): The realm of thought, consciousness, and mental phenomena. According to Descartes, the mind is non-material, not subject to the laws of physics, and is the essence of self-awareness and rationality.
• Body (Res Extensa): The realm of physical substance, which includes matter and the physical laws governing it. The body is material, occupies space, and can be described in terms of mechanics and physics.

I think the physical magnitudes here are abut the perceptual events.

In keeping with Fechner's significant move away from the dualistic mindbody philosophy of Descartes, these researchers also began to explore the functional relation between numerically assessed sensory magnitudes of perceptual events and their corresponding physical magnitudes.

What is the sensorimonitor continuum of human hand function? (left: sensor, right: motor) draw it and explain them focusing on the difference.

(Sensory) Tactile - Active haptic sensing - Prehension - Non-prehensile activities (Motor)

 

Tactile - hand is always stationary

Active haptic sensing - hand is always moving

Prehension - Grasping

Non-prehensile activities - Non-grasping activities; pointing, keyboard toucing, sign language and etc

 

 

What are corollary discharge (CD) and efference copy (EC)?

To be explained later. A copy of motor signal that is used to predict sensory information. The predicted sensory information can be used for analyzing the external stimulus by measuring the difference between the prediction and the actual sensor signal. CD/EC are the similar terms.

 

Corollary Discharge

Definition: Corollary discharge (CD) is a copy of the motor command sent by the brain to the muscles, which is also sent to sensory areas of the brain.

Function:

• Sensory Prediction: It helps predict the sensory consequences of an action. For example, when you move your eyes, CD signals can predict the visual changes that will occur as a result of the eye movement.
• Distinguishing Self-Generated Actions: By comparing the predicted sensory feedback from CD with actual sensory feedback, the brain can distinguish between sensory changes caused by self-generated actions and those caused by external stimuli.

Efference Copy

Definition: Efference copy (EC) is essentially another term for corollary discharge, referring to the internal copy of an outgoing motor command (efferent signal) that is sent to other parts of the brain.