תובנה - Neuroscience - # Attention and Sensory Processing in Secondary Thalamic Nuclei

Attentional Modulation of Secondary Somatosensory and Visual Thalamus in Mice

Q: How do the secondary thalamic nuclei contribute to cortical plasticity and multimodal associative learning

The secondary thalamic nuclei, such as POm and LP, play a crucial role in cortical plasticity and multimodal associative learning. These nuclei are involved in reshaping activity based on behavioral relevance and task engagement. In the context of the study, the researchers found that behavioral training reshaped activity in secondary thalamic nuclei, inducing responses to behaviorally relevant stimuli regardless of sensory modality. This suggests that the secondary nuclei contribute to encoding the behavioral relevance of stimuli and facilitating learning based on task demands. In terms of cortical plasticity, studies have shown that POm and LP are involved in facilitating long-term plasticity in the cortex. For example, POm excitation has been found to facilitate long-term plasticity in layer 2/3 pyramidal cells in S1, while LP likely contributes to cortical plasticity as well. The elevated firing rates in these nuclei during periods of high arousal and task engagement could open a window of plasticity, allowing for learning and memory formation based on the behavioral context. Therefore, the secondary thalamic nuclei contribute to cortical plasticity by modulating activity in response to behaviorally relevant stimuli and facilitating associative learning across modalities.

Q: What are the potential mechanisms, such as neuromodulation or corticothalamic inputs, that drive the non-sensory responses in the secondary thalamic nuclei

The non-sensory responses observed in the secondary thalamic nuclei, such as POm and LP, could be driven by various mechanisms, including neuromodulation and corticothalamic inputs. Neuromodulatory systems, such as acetylcholine and norepinephrine, are known to track arousal levels and can directly influence thalamic activity. These neuromodulators may act on the secondary thalamic nuclei to modulate responses to behaviorally relevant stimuli. For example, cholinergic activity could enhance tactile responses in POm or visual responses in LP, depending on the behavioral context. Additionally, corticothalamic inputs play a crucial role in shaping thalamic activity. POm receives input from somatosensory cortex, while LP receives input from visual cortical areas. These inputs could drive the non-sensory responses observed in the nuclei, especially in the context of attention and task engagement. Direct corticothalamic projections may contribute to enhanced responses to behaviorally relevant stimuli, regardless of sensory modality. Therefore, a combination of neuromodulation and corticothalamic inputs likely underlies the non-sensory responses in the secondary thalamic nuclei.

Q: How do the different subregions and functional subdivisions within POm and LP differentially encode sensory and non-sensory information

The different subregions and functional subdivisions within POm and LP exhibit distinct encoding of sensory and non-sensory information. In the study, the researchers found that the effects of conditioning on POm sensory responses varied by anatomical location. While visual conditioning induced visual responses throughout POm, cells in the lateral dorsal region of POm remained more sensitive to the air puff than the drifting grating. This suggests that there is a core location in POm that is always whisker-sensitive, while conditioning dictates the selectivity of the rest of the nucleus. Similarly, LP showed varied stimulus-evoked activity that was heavily dependent on conditioning. In tactilely conditioned mice, the majority of LP cells responded to both the air puff and the drifting grating, while in visually conditioned mice, a greater portion of cells were visually responsive. The different subregions within LP likely contribute to the differential encoding of sensory and non-sensory information. For example, LP receives input from various visual cortical areas, which could drive visual responses in some regions but not others. Overall, the subregions and functional subdivisions within POm and LP play a critical role in encoding sensory and non-sensory information based on the behavioral context and task demands. The differential responses observed in these nuclei highlight the complex and nuanced processing of stimuli across modalities within the thalamus.

מושגי ליבה

Behavioral training reshapes activity in secondary thalamic nuclei, inducing responses to behaviorally relevant stimuli regardless of sensory modality.

תקציר

The study investigated how sensory-, arousal-, and movement-evoked activity in the secondary somatosensory (POm) and visual (LP) thalamic nuclei are shaped by associative learning in head-fixed mice.

Key highlights:

Mice were trained to attend to a stimulus of one sensory modality (visual or tactile) while ignoring a stimulus of the other modality.
In tactilely conditioned mice, POm was robustly activated by touch and largely unresponsive to visual stimuli. In visually conditioned mice, POm showed widespread visual responses.
Similar effects were observed in LP, where tactile conditioning potentiated tactile responses and visual conditioning enhanced visual responses.
POm and LP activity correlated with arousal and movement regardless of conditioning type, but this could not fully explain the sensory responses.
The study concludes that the secondary thalamic nuclei encode the behavioral relevance of a stimulus, rather than its sensory modality.

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biorxiv.org

סטטיסטיקה

Mice in the tactile conditioning group displayed a robust increase in pupil radius and whisking amplitude at the onset of the air puff, which persisted throughout the offset period.
Mice in the visual conditioning group exhibited a pupil constriction at stimulus onset, followed by pupil dilation.
POm cells in tactilely conditioned mice had significantly higher response indices to the air puff compared to the drifting grating, while POm cells in visually conditioned mice exhibited a wide range of selectivity.
LP cells in tactilely conditioned mice had significantly higher response indices to the air puff compared to the drifting grating.

ציטוטים

"Behavioral training reshapes activity in secondary thalamic nuclei, inducing responses to behaviorally relevant stimuli regardless of sensory modality."
"Secondary nuclei may respond to behaviorally relevant, reward-predicting stimuli regardless of stimulus modality."

תובנות מפתח מזוקקות מ:

Attentional modulation of secondary somatosensory and visual thalamus of mice

by Petty,G., Br... ב- www.biorxiv.org 03-25-2024

https://www.biorxiv.org/content/10.1101/2024.03.22.586242v1

שאלות מעמיקות

How do the secondary thalamic nuclei contribute to cortical plasticity and multimodal associative learning

The secondary thalamic nuclei, such as POm and LP, play a crucial role in cortical plasticity and multimodal associative learning. These nuclei are involved in reshaping activity based on behavioral relevance and task engagement. In the context of the study, the researchers found that behavioral training reshaped activity in secondary thalamic nuclei, inducing responses to behaviorally relevant stimuli regardless of sensory modality. This suggests that the secondary nuclei contribute to encoding the behavioral relevance of stimuli and facilitating learning based on task demands.
In terms of cortical plasticity, studies have shown that POm and LP are involved in facilitating long-term plasticity in the cortex. For example, POm excitation has been found to facilitate long-term plasticity in layer 2/3 pyramidal cells in S1, while LP likely contributes to cortical plasticity as well. The elevated firing rates in these nuclei during periods of high arousal and task engagement could open a window of plasticity, allowing for learning and memory formation based on the behavioral context. Therefore, the secondary thalamic nuclei contribute to cortical plasticity by modulating activity in response to behaviorally relevant stimuli and facilitating associative learning across modalities.

What are the potential mechanisms, such as neuromodulation or corticothalamic inputs, that drive the non-sensory responses in the secondary thalamic nuclei

The non-sensory responses observed in the secondary thalamic nuclei, such as POm and LP, could be driven by various mechanisms, including neuromodulation and corticothalamic inputs. Neuromodulatory systems, such as acetylcholine and norepinephrine, are known to track arousal levels and can directly influence thalamic activity. These neuromodulators may act on the secondary thalamic nuclei to modulate responses to behaviorally relevant stimuli. For example, cholinergic activity could enhance tactile responses in POm or visual responses in LP, depending on the behavioral context.
Additionally, corticothalamic inputs play a crucial role in shaping thalamic activity. POm receives input from somatosensory cortex, while LP receives input from visual cortical areas. These inputs could drive the non-sensory responses observed in the nuclei, especially in the context of attention and task engagement. Direct corticothalamic projections may contribute to enhanced responses to behaviorally relevant stimuli, regardless of sensory modality. Therefore, a combination of neuromodulation and corticothalamic inputs likely underlies the non-sensory responses in the secondary thalamic nuclei.

How do the different subregions and functional subdivisions within POm and LP differentially encode sensory and non-sensory information

The different subregions and functional subdivisions within POm and LP exhibit distinct encoding of sensory and non-sensory information. In the study, the researchers found that the effects of conditioning on POm sensory responses varied by anatomical location. While visual conditioning induced visual responses throughout POm, cells in the lateral dorsal region of POm remained more sensitive to the air puff than the drifting grating. This suggests that there is a core location in POm that is always whisker-sensitive, while conditioning dictates the selectivity of the rest of the nucleus.
Similarly, LP showed varied stimulus-evoked activity that was heavily dependent on conditioning. In tactilely conditioned mice, the majority of LP cells responded to both the air puff and the drifting grating, while in visually conditioned mice, a greater portion of cells were visually responsive. The different subregions within LP likely contribute to the differential encoding of sensory and non-sensory information. For example, LP receives input from various visual cortical areas, which could drive visual responses in some regions but not others.
Overall, the subregions and functional subdivisions within POm and LP play a critical role in encoding sensory and non-sensory information based on the behavioral context and task demands. The differential responses observed in these nuclei highlight the complex and nuanced processing of stimuli across modalities within the thalamus.