Biology subjects

Smith, C. D.

Publications and source records attributed to Smith, C. D..

3 recordsLinked to original sources

bioRxiv2025

Negative-Valence Neurons in the Larval Zebrafish Pallium

An organisms survival depends on the rapid classification of sensory events as either harmful or beneficial. In mammals, this computation is partially performed by neurons in the amygdala that respond to signals with negative or positive valence. The larval zebrafish pallium is thought to contain homologs of the mammalian amygdala, isocortex, and hippocampus; however, the signals encoded by pallial neurons remain largely uncharacterized. Using two-photon light-sheet microscopy to image 7-9-day-old zebrafish that express pan-neuronal GCaMP6s, we recorded calcium dynamics throughout the brain while presenting a panel of strongly aversive stimuli including infrared heat, electric shock, and a whole-field looming shadow, together with milder threats including vibration, loud sound, light transitions, and a partial looming stimulus. A compact cluster of neurons in the rostrolateral dorsal pallium (Rl) responded vigorously to strongly noxious and fully looming stimuli, but not to the milder cues. In contrast, neurons in the ventromedial pallium and habenula responded to all stimuli tested. Rl neurons are characterized by high Tiam2a expression, suggesting they can be genetically accessed. Thus, our results identify a locus of negative valence neurons in the teleost pallium.

neuroscience↗

bioRxiv2024

Toward an understanding of the small groups of thumb muscles that produce lateral pinch movement: application to surgical restoration of grasp following neurologic impairment

ABSTRACT AND KEY TERMSO_ST_ABSPurposeC_ST_ABSTendon transfer surgeries that engage the flexor pollicis longus muscle (FPL) are commonly performed to enable lateral pinch grasp in persons with tetraplegia. Functional outcomes, however, have been mixed. This might be the case, in part, because FPL produces hyperflexion at the interphalangeal (IP) joint and radial deviation at the carpometacarpal (CMC) joint. Therefore, the goal of this simulation study was to investigate whether small groups of muscles could produce movement with less IP joint hyperflexion and CMC ab/adduction than FPL produces during lateral pinch movement. MethodsWe adapted a published, open-source computational musculoskeletal model of the hand to implement lateral pinch grasp. A forward-dynamics simulation approach was used to drive the thumb for 27 muscle groups being considered from an extended posture to a flexed posture to make contact with the side of the index finger. We calculated CMC ab/adduction deviation from the flexion-extension plane and IP joint flexion in the plane that all muscle groups produced, and compared those joint angle movements to those of FPL when it alone drove the thumb. ResultsOf the 27 simulations, three muscle groups, each consisting of three or four muscles, generated lower IP joint flexion and CMC ab/adduction than those of FPL. ConclusionsThis simulation work points to the potential of novel, multi-insertion site tendon transfer surgeries to out-perform the current standard of care to restore lateral pinch grasp following tetraplegia.

bioengineering↗

bioRxiv2019

FOXP2 exhibits neuron class specific expression, but is not required for multiple aspects of cortical histogenesis

The expression patterns of the transcription factor FOXP2 in the developing mammalian forebrain have been described, and some studies have tested the role of this protein in the development and function of specific forebrain circuits by diverse methods and in multiple species. Clinically, mutations in FOXP2 are associated with severe developmental speech disturbances, and molecular studies indicate that impairment of Foxp2 may lead to dysregulation of genes involved in forebrain histogenesis. Here, anatomical and molecular phenotypes of the cortical neuron populations that express FOXP2 were characterized in mice. Additionally, Foxp2 was removed from the developing mouse cortex at different prenatal ages using two Cre-recombinase driver lines. Detailed molecular and circuit analyses were undertaken to identify potential disruptions of development. Surprisingly, the results demonstrate that Foxp2 function is not required for many functions that it has been proposed to regulate, and therefore plays a more limited role in cortical development than previously thought.

developmental biology↗