Biology subjects

Groh, A.

Publications and source records attributed to Groh, A..

4 recordsLinked to original sources

bioRxiv2024

A tactile discrimination task to study neuronal dynamics in freely-moving mice

Sensory discrimination tasks are valuable tools to study neuronal mechanisms of perception and learning. Most discrimination tasks for electrophysiological and imaging studies in rodents require the animals to be head-fixed. However, implementing neurophysiological recordings into more ethologically realistic settings with unrestrained animals has been challenging. Here, we introduce a whisker-dependent discrimination task for freely moving mice, integrating electrophysiology and calcium imaging with cellular resolution. In this go/no-go paradigm, male mice learned to discriminate aperture widths within days while foraging on a linear platform. The setups versatility enables exploration into diverse behavioral aspects, including tactile discrimination thresholds, valence-dependent behavior, and cognitive flexibility following repeated task rule reversals. Rule learning was highly stereotypical, fast and reproducible across individual mice. Electrophysiological recordings revealed distributed tactile processing across the thalamocortical system, with subsets of units encoding both movement- and stimulus-related features. Sensory encoding was strongly modulated by behavioral state, with neurons tuned to locomotion, whisking, whisker angle and phase, head angle, and spatial position. By enabling simultaneous extracellular recordings and calcium imaging within the same freely moving paradigm, this approach allows for precise synchronization of neural activity with multiple behavioral readouts. This paradigm provides a versatile tool to elucidate neural mechanisms of cognition and sensory processing in naturalistic conditions.

neuroscience↗

bioRxiv2024

Differential representation of active and passive touch in mouse somatosensory thalamus

Active and passive sensing strategies are integral to an animals behavioral repertoire. Nevertheless, there is a lack of information regarding the neuronal circuitry that underpins these strategies, particularly at the thalamus level. We evaluated how active versus passive whisker deflections are represented in single neurons of the ventral posterior thalamus (VPM) and the posterior medial thalamus (POm) in awake mice. These are the first-and higher-order thalamic nuclei of the whisker system, respectively. VPM neurons robustly responded to both active and passive whisker deflections, while POm neurons showed a preference for passive deflections and responded poorly to active touches. This response disparity could not be explained by the animals voluntary whisking state or stimulus kinetics. In contrast, cortical activity significantly influenced POms responses to passive touch. Inhibition of the barrel cortex strongly attenuated whisker responses in POm and simultaneously increased the whisking phase coding. This suggests that POm receives touch information from the cortex and phase information from the brainstem. Together, these findings suggest two thalamic relay streams, where VPM robustly relays both active and passive deflection, while POms sensitivity requires top-down cortical involvement to signal salient events such as unexpected passive deflections.

neuroscience↗

bioRxiv2022

Trans-collicular pathways for sensory-motor integration in the whisker system

The superior colliculus (SC), a conserved midbrain-node with extensive long-range connectivity throughout the brain, is a key structure for innate behaviors. Descending cortical pathways are increasingly recognized as central control points for SC-mediated behaviors, but how cortico-collicular pathways coordinate SC activity at the cellular level is poorly understood. Moreover, despite the known role of the SC as a multisensory integrator, the involvement of the SC in the somatosensory system is largely unexplored in comparison to its involvement in the visual and auditory systems. Here, we mapped the connectivity of the whisker-sensitive region of the SC in mice with trans-synaptic and intersectional tracing tools and in vivo electrophysiology. The results reveal a novel trans-collicular connectivity motif in which neurons in motor- and somatosensory cortices impinge onto the brainstem-SC-brainstem sensory-motor arc and onto SC-midbrain output pathways via only one synapse in the SC. Intersectional approaches and optogenetically assisted connectivity quantifications in vivo reveal convergence of motor and somatosensory cortical input on individual SC neurons, providing a new framework for sensory-motor integration in the SC. More than a third of the cortical recipient neurons in the whisker SC are GABAergic neurons, which include a hitherto unknown population of GABAergic projection neurons targeting thalamic nuclei and the zona incerta. These results pinpoint a whisker region in the SC of mice as a node for the integration of somatosensory and motor cortical signals via parallel excitatory and inhibitory trans-collicular pathways which link cortical and subcortical whisker circuits for somato-motor integration.

neuroscience↗

bioRxiv2022

Primary Somatosensory Cortex Bidirectionally Modulates Sensory Gain and Nociceptive Behavior in a Layer-Specific Manner

The primary somatosensory cortex (S1) is a hub for body sensation of both innocuous and noxious signals, yet its role in somatosensation versus pain is debated. Despite known contributions of S1 to sensory gain modulation, its causal involvement in subjective sensory experiences remains elusive. Here, in mouse S1, we reveal the involvement of cortical output neurons in layers 5 (L5) and 6 (L6) in the perception of innocuous and noxious somatosensory signals. We find that L6 activation can drive aversive hypersensitivity and spontaneous nocifensive behavior. Linking behavior to neuronal mechanisms, we find that L6 enhances thalamic somatosensory responses, and in parallel, strongly suppresses L5 neurons. Directly suppressing L5 reproduced the pronociceptive phenotype induced by L6 activation, suggesting an anti-nociceptive function for L5 output. Indeed, L5 activation reduced sensory sensitivity and reversed inflammatory allodynia. Together, these findings reveal a layer-specific and bidirectional role for S1 in modulating subjective sensory experiences.

neuroscience↗