Podcast
Questions and Answers
What is the role of the afferent fibers in the trigeminal pathway?
What is the role of the afferent fibers in the trigeminal pathway?
What sensory function is lost with a lesion in area 3b of the primary somatosensory cortex?
What sensory function is lost with a lesion in area 3b of the primary somatosensory cortex?
Where does the signal travel after reaching the trigeminal nuclei?
Where does the signal travel after reaching the trigeminal nuclei?
Which neuron type is primarily responsible for identifying an object's quality during stereognosis?
Which neuron type is primarily responsible for identifying an object's quality during stereognosis?
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In which area is tactile and proprioceptive information integrated?
In which area is tactile and proprioceptive information integrated?
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What aspect of the primary somatosensory cortex (SS cortex) is primarily noted in the document?
What aspect of the primary somatosensory cortex (SS cortex) is primarily noted in the document?
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What does the columnar representation in the SS cortex indicate?
What does the columnar representation in the SS cortex indicate?
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Which of the following structures receives incoming sensory afferent information?
Which of the following structures receives incoming sensory afferent information?
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Study Notes
Sensory Pathways
- Stereognosis: ability to identify objects by touch, involving 3b neurons and comparison to previous experiences to deduce shape, size, and other features of objects
- Accurate tactile quality is needed to distinguish objects based on their shape, size and other features.
- The size of the objects also plays a role in being able to distinguish the shape
- Different neurons identify various aspects of objects
- Information from the skin (touch) and proprioceptive information from muscles and joints combine to create perception.
Flow of Sensory Information
- Information on the skin and muscles/joints passes through the thalamus (VP) to the primary sensory cortex (SS).
- Neurons pass through posterior dorsal area of the thalamus (VP)
- There is an interplay between information from different sources - touch and proprioception, eye movements also take part in processing.
- Sensory information from the body is sent to the primary sensory cortex and then further processed in association areas.
- Processing of touch, pain, and temperature is further processed
- Cortical neuron involvement leads to the identification of objects
- The secondary (higher) sensory cortex receives input from SS and other areas. This is where complex perceptions, like stereognosis, are formed.
- A descending pathway from the motor cortex influences sensory processing.
Cortical Representation
- The representation of sensory information in the cortex is organized topographically.
- Different parts of the body are represented in distinct areas of the cortex.
- Neurons in the cortex are organized into columns.
- In the somatosensory cortex (S1), this columnar organization is present (columns of neurons receiving input from small areas of skin).
- Information from different parts of the body travels to different columns of the S1 cortex.
Sensory Lesions
- Lesions in the primary sensory cortex can affect the ability to discriminate between different tactile stimuli.
- Lesions in the higher sensory areas affect complex perceptions like stereognosis.
- In contrast lesions in the higher sensory areas produce a disturbance in the perception of spatial features instead of the ability to perceive individual stimuli.
- Lesions also cause contralateral effects in sensory processing
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Description
Explore the intricate mechanisms of sensory pathways, focusing on the role of stereognosis and tactile quality in object identification. Understand how sensory information from the skin and proprioceptive input integrates within the brain to form our perception of objects. Delve into the neural processes involved in transmitting this information to the primary sensory cortex.
