Focal infrared neural stimulation with high-field functional MRI: A rapid way to map mesoscale brain connectomes

Abstract

We have developed a way to map brain-wide networks using focal pulsed infrared neural stimulation in ultrahigh-field magnetic resonance imaging (MRI). The patterns of connections revealed are similar to those of connections previously mapped with anatomical tract tracing methods. These include connections between cortex and subcortical locations and long-range cortico-cortical connections. Studies of local cortical connections reveal columnar-sized laminar activation, consistent with feed-forward and feedback projection signatures. This method is broadly applicable and can be applied to multiple areas of the brain in different species and across different MRI platforms. Systematic point-by-point application of this method may lead to fundamental advances in our understanding of brain connectomes.

Infrared inhibition impacts on locally initiated and propagating action potentials and the downstream synaptic transmission

“…Our observation that the IR light pulses terminated the firing at low frequencies but not those at high firing frequencies nor the suggests that the physiological and anatomical “contexts” of an AP are important to evaluate or predict the impact of the IR-mediated modulation. When IR light pulses are applied to complex neuronal networks such as mammalian cortexes, 3 , 6 – 9 the IR light inhibition of could serve as a basic model for understanding the impact of IR light on neuronal soma and on the axon initial segment. Assuming neurons in a network are under various levels of synaptic drive, our results suggest that neurons under weak excitatory drive will be inhibited disproportionally compared to those under strong excitatory drive.…”

“…At the upper-most level, the response of a brain region to IR light modulation will rely on the net result from the interaction of IR light with excitatory and inhibitory components of the network. 9 Gaining insights into how a neuron as a functional whole is modulated by IR light irradiation is the first step toward a more thorough understanding of IR-mediated modulation of a complex network.…”

“…Infrared (IR) light has emerged as a new modality that can reliably modulate both neural and muscular activities with the advantages of being contact-free, spatially selective, and MRI compatible. 1 – 3 IR-mediated modulation of excitable tissues has been demonstrated in a wide range of promising clinical applications, such as cochlear prostheses, 4 , 5 brain stimulation and mapping, 6 – 9 cardiac pacing, 10 and neural monitoring during surgery. 11 , 12 The main biological processes induced by pulsed IR light are attributed to the spatiotemporal thermal transients generated by water and tissue absorption, 13 which in turn can alter the membrane capacitance, 14 – 17 membrane resistance, 18 , 19 ion channel activities, 19 – 25 and intracellular calcium dynamics.…”

Computational modeling of the photon transport, tissue heating, and cytochrome C oxidase absorption during transcranial near-infrared stimulation

“…Indeed, photothermal neurostimulation using the 1064nm laser at the frontal cortex has been shown to improve cognitive functions along with neurometabolic activity[9]. Moreover, photothermal neurostimulation has been shown to be promising to map mesoscale brain connectomes[19].…”

INS-fOCT: a label-free, all-optical method for simultaneously manipulating and mapping brain function

“…36,37 This method has been demonstrated to activate cortical neurons as assessed by electrophysiological recordings, [38][39][40] optical calcium imaging, 41 OISI, 42 and fMRI. 43 Using trains of pulsed infrared light delivered via a fiber optic (e.g., 100 μm to 1 mm in diameter), INS leads to membrane capacitance change and depolarization of the neuronal membrane. 36,38,40,44 Although not cell-type specific, INS achieves high spatial precision of stimulation (matching the size of fiber optic used).…”