27- Haptics & the Brain-Body Connection (3.30.26)

HAPTICS & the Brain-Body Connection

3.30.26

START

Announcements

Exam 2 due tonight (Mon 3/30) at 11:59 pm!

01.

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Project Milestone 3 due on Wed (4/1) at 11:59 pm - needs to be a rought draft of your video -submit in groups

Agenda

Haptic Perception

01.

The Dorsal Column Medial Lemiscal Pathway (DCML)

02.

Somatoosensory Cortex

03.

Cortical Plasticity

04.

Haptic Perception

actively using touch to perceive and identify objects by their 3D shape and other material properties

Haptics Involves Tactile Perception

• Involves the integration of information from tactile perception, proprioception, and themoreception
• Tactile perception:
• shape: edges, corners, curvature
• surface features: texture, hardness, stickiness

Haptics Involves Proprioception

• Involves the integration of information from tactile perception, proprioception, and themoreception
• Proprioception:
• shape: position and conformation of the hand holding the object
• weight: force the object applies to the limbs

Haptics Involves Thermoreception

• Involves the integration of information from tactile perception, proprioception, and themoreception
• Themoreception:
• material properties that would affect temperature (e.g., metal tends to be cold to the touch)

Dorsal column-medial lemiscal (DCML) pathway

• sends signals involved in tactile perception and proprioception

Dorsal column-medial lemniscal (DCML) pathway

• first synapse in the medulla
• then medial lemiscus carries info from medulla to ventral posterior (VP) nucleus of the thalamus

Primary Somatosensory Cortex (S1)

• receives signals directly from the thalamus
• sub-divided into 4 sections

Primary Somatosensory Cortex (S1)

• Has four subregions: Areas 1, 2, 3a, & 3b
• All sub-areas of S1 receive input directly from the thalamus
• Area 2 receives input from all other areas of S1
• Each of the 4 sub-regions of S1 contains a distinct body-mapping organization

Somatotopic Maps

• somatotopic mapping - using brain-space to represent physical space: similar principle to retinotopic mapping and tonotopic mapping

• Adjacent cell populations in S1 tend to represent nearby body areas

• The extent (size) of these different cell populations corresponds to the density of receptors in the corresponding body part
• similar principle to cortical magnification of the fovea

Secondary Somatosensory Cortex (S2)

• subregion of somatosensory cortex that receives its input from S1
• considered part of the ventral stream of somatosensory information processing

Secondary Somatosensory Cortex (S2)

Neurons in Area S2 show receptive fields related to the orientation of the edge of an object

• respond to stimulation from multiple parts of the body
• thought to play a role in judging the shape of an object
• related to identity, consistent with the ventral stream

Dorsal & Ventral Pathways from the Thalamus

Ventral pathway: allows for representation of 3D shape

• area 2 of S1 combines proprioceptive and tactile information and sends to S2
• separate pathways from S2 for memory storage and decision-making

Dorsal & Ventral Pathways from the Thalamus

Dorsal pathway: perception to guide action

• e.g., reaching to grasp, adjusting action based on feel
• area S1 sends info to posterior parietal cortex, which relays it to premotor cortex

VP Thalamus Sends Affective Signals to Amygdala, Insula, & ACC

VP Thalamus Sends Discriminative Signals to Insula & S1

Cortical Plasticity

Learning to make fine sensory discriminations involves expanding the region of sensory cortex that represented the corresponding body part

• non-human primate studies showed that the cortical space devoted to the index finger increased after a training

Cortical Plasticity

Learning to make fine sensory discriminations involves expanding the region of sensory cortex that represented the corresponding body part

• makes phantom limb training possible

Thank you for listening!

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