Biology subjects

Collie, M. F.

Publications and source records attributed to Collie, M. F..

3 recordsLinked to original sources

bioRxiv2025

Distributed control circuits across a brain-and-cord connectome

Just as genomes revolutionized molecular genetics, connectomes (maps of neurons and synapses) are transforming neuroscience. To date, the only species with complete connectomes are worms1-3 and sea squirts4 (103-104 synapses). By contrast, the fruit fly is more complex (108 synaptic connections), with a brain that supports learning and spatial memory5,6 and an intricate ventral nerve cord analogous to the vertebrate spinal cord7-11. Here we report the first densely reconstructed adult fly connectome that unites the brain and ventral nerve cord, and we leverage this resource to investigate principles of neural control. We show that effector neurons (motor neurons, endocrine cells and efferent neurons targeting the viscera) are primarily influenced by sensory neurons in the same body part, forming local feedback loops. These local loops are linked by long-range circuits involving ascending and descending neurons organized into behavior-centric modules. Single ascending and descending neurons are often positioned to influence the voluntary movements of multiple body parts, together with the endocrine cells or visceral organs that support those movements. Brain regions involved in learning and navigation supervise these circuits. These results reveal an architecture that is distributed, parallelized and embodied, reminiscent of distributed control architectures in engineered systems12,13.

neuroscience↗

bioRxiv2025

Specialized parallel pathways for adaptive control of visual object pursuit

To pursue a moving visual object, the brain must generate motor commands that continuously steer the object to the center of the visual field via feedback. The gain of this control loop is flexible, yet the biological mechanisms underlying such adaptive control are not well-understood. Here we show that adaptive control in the Drosophila pursuit system involves two parallel pathways. One detects objects in the periphery and steers them toward the center of the visual field. The other detects objects near the center of the visual field and steers them to the visual midline. This latter pathway is flexible: gain increases when the object is moving away from the midline and when the pursuer is running fast. This latter pathway is also preferentially recruited when the fly is aroused, and suppressing it decreases pursuit performance. Our findings demonstrate how adaptive control can emerge from parallel pathways with specialized properties.

neuroscience↗

bioRxiv2017

Preferential targeting of lateral entorhinal inputs onto newly integrated granule cells

Mature dentate granule cells in the hippocampus receive input from the entorhinal cortex via the perforant path in precisely arranged lamina, with medial entorhinal axons innervating the middle molecular layer and lateral entorhinal cortex axons innervating the outer molecular layer. Although vastly outnumbered by mature granule cells, adult-generated newborn granule cells play a unique role in hippocampal function, which has largely been attributed to their enhanced excitability and plasticity (Schmidt-Hieber et al., 2004; Ge et al., 2007). Inputs from the medial and lateral entorhinal cortex carry different informational content, thus the distribution of inputs onto newly integrated granules will affect their function in the circuit. Therefore we examined the functional innervation and synaptic maturation of newly-generated dentate granule cells using retroviral labeling in combination with selective optogenetic activation of medial or lateral entorhinal inputs. Our results indicate that lateral entorhinal inputs provide nearly all the functional innervation of newly integrated granule cells. Despite preferential functional targeting, the dendritic spine density of immature granule cells was not increased in the outer molecular layer compared to the middle molecular layer. However, chronic blockade of neurotransmitter release in medial entorhinal axons with tetanus toxin disrupted normal synapse development from both medial and lateral entorhinal inputs. Our results support a role for preferential lateral perforant path input onto newly generated neurons in mediating pattern separation, but also indicates that medial perforant path input is necessary for normal synaptic development.\n\nSignificance StatementThe formation of episodic memories involves the integration of contextual and spatial information. Newly integrated neurons in the dentate gyrus of the hippocampus play a critical role in this process, despite constituting only a minor fraction of total granule cells. Here we demonstrate that these neurons preferentially receive information thought to convey the context of an experience - a unique role that each newly integrated granule cell serves for about a month before reaching maturity.

neuroscience↗