Calcium activity is a degraded estimate of spikes

Hot Off the Press – December 22, 2022

Summary

Neurons communicate via electrical signals – spikes – and recording these has provided fundamental information regarding how the brain works. When neurons send electrical signals, several other biological signals occur, notably calcium. Calcium signaling is often used to make inferences about spike activity. However, it was unknown how closely calcium signaling hews to known spike correlates during a complex cognitive operation, such as learning. Hart and colleagues used olfactory discrimination learning in rats, spike recording, and calcium imaging to address this question. Spike data replicated findings from previous olfactory discrimination learning tasks; spikes represented both specific and general components of the task. Calcium activity provided a degraded estimate of the information contained in spikes, representing the task only in broad-strokes. These findings demonstrate that using calcium activity as a proxy for spikes during complex cognitive operations results in the loss of information conveyed by subtle changes in spike activity.

Publication Information

Hart, Evan E; Gardner, Matthew P H; Panayi, Marios C; Kahnt, Thorsten; Schoenbaum, Geoffrey

Calcium activity is a degraded estimate of spikes Journal Article

In: Curr Biol, vol. 32, no. 24, pp. 5364–5373.e4, 2022, ISSN: 1879-0445.

Abstract | Links

@article{pmid36368324,

title = {Calcium activity is a degraded estimate of spikes},

author = {Evan E Hart and Matthew P H Gardner and Marios C Panayi and Thorsten Kahnt and Geoffrey Schoenbaum},

url = {https://pubmed.ncbi.nlm.nih.gov/36368324/},

doi = {10.1016/j.cub.2022.10.037},

issn = {1879-0445},

year  = {2022},

date = {2022-12-01},

urldate = {2022-12-01},

journal = {Curr Biol},

volume = {32},

number = {24},

pages = {5364--5373.e4},

abstract = {Recording action potentials extracellularly during behavior has led to fundamental discoveries regarding neural function-hippocampal neurons respond to locations in space, motor cortex neurons encode movement direction, and dopamine neurons signal reward prediction errors-observations undergirding current theories of cognition, movement, and learning. Recently it has become possible to measure calcium flux, an internal cellular signal related to spiking. The ability to image calcium flux in anatomically or genetically identified neurons can extend our knowledge of neural circuit function by allowing activity to be monitored in specific cell types or projections, or in the same neurons across many days. However, while initial studies were grounded in prior unit recording work, it has become fashionable to assume that calcium is identical to spiking, even though the spike-to-fluorescence transformation is nonlinear, noisy, and unpredictable under real-world conditions. It remains an open question whether calcium provides a high-fidelity representation of single-unit activity in awake, behaving subjects. Here, we have addressed this question by recording both signals in the lateral orbitofrontal cortex (OFC) of rats during olfactory discrimination learning. Activity in the OFC during olfactory learning has been well-studied in humans, nonhuman primates, and rats, where it has been shown to signal information about both the sensory properties of odor cues and the rewards they predict. Our single-unit results replicated prior findings, whereas the calcium signal provided only a degraded estimate of the information available in the single-unit spiking, reflecting primarily reward value.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}