lecture 10 - receptive fields, lateral inhibition

what sensory modality is conveyed by DCML pathway

a. temp

b. fine touch (but also vibration, pressure & proprioception)

c. nociption

d. back pain

b. fine touch (but also vibration, pressure & proprioception)

DRG neurons transmit mechanosensitive signals via their centrally projecting afferent fibers that directly innervate cell bodies in ________

a. dorsal column nuclei

b. substantia gelatinosa

c. VPL of thalamus

d. medial lemniscus

a. dorsal column nuclei

What does the Dorsal Column Medial Lemniscal (DCML) pathway process?

Fine touch signals from skin mechanoreceptors.

Where do first-order neurons in the DCML pathway originate?

In the dorsal root ganglion (DRG) of the peripheral nervous system (PNS).

Where do first-order neurons synapse in the DCML pathway?

In the dorsal column nuclei (DCN) of the medulla with second-order neurons.

What is a receptive field?

A small area of skin that, when stimulated, activates a sensory neuron.

What is the shape of a DRG neuron's receptive field in the DCML pathway?

Annular (ring-shaped)

What happens when tactile stimulation occurs in a DRG neuron's receptive field?

It activates the corresponding DCN neuron and inhibits neighboring DCNs.

What is lateral inhibition in the DCML pathway?

Inhibitory interneurons reduce activation of neighboring DCNs to sharpen contrast.

How does lateral inhibition affect receptive fields?

It changes receptive fields from annular to concentric "on-center, off-surround" shapes.

Why is lateral inhibition important for tactile acuity?

It enhances contrast and improves two-point discrimination by suppressing weaker stimuli near strong stimuli.

What shape do receptive fields take in S1 after convergence of inputs?

Rectangular shapes that help detect movement direction and stimulus orientation.

What brain areas in S1 are involved in tactile stimulus processing?

S1, Area 3 and Area 1.

What four mechanisms contribute to two-point discrimination?

1. Lateral inhibition

2. High representation in somatosensory cortex

3. Small receptive field size

4. High density of receptive fields

What is activity-dependent reorganization of receptive fields?

Increased use of a body part (e.g., hands) increases receptive field number and tactile acuity.

Does DRG cell 1 and cell 2 have separate receptive field? T or F

T

All sensory neurons in a sensory pathway doesn’t have a receptive field. T or F

F