Patterns of Activity of Simultaneously Recorded Neurons in Midbrain Reticular Formation

Axonal activity in vivo: technical considerations and implications for the exploration of neural circuits in freely moving animals

“…In agreement with descriptions of SDWs in Robbins et al early reports of axonal action potentials also reported that the amplitude and shape of axonal recordings were stable for at least for up to 24 h (Amassian et al, 1961 ). While the largest amplitude axonal spikes reported by Cooper et al ( 1969 ) were ~150 μV, Robbins et al reported recordings of several axons that were significantly larger in amplitude, particularly in the alveus.…”

“…With regard to recordings of brief units, Mountcastle preferred to refer to putative cortical stellate neuron waveforms as “thin spikes” due to the uncertainty that they may have been thalamocortical fibers (Mountcastle et al, 1969 ). Both Amassian et al ( 1961 ) and Cooper et al ( 1969 ) reported recordings of brief, triphasic action potentials approximately 130 μs in duration in a variety of species (cat, squirrel, monkey) and recording locations (optic tract, geniculostriate fibers in the visual cortex, pons and medulla, and also the cuneate nucleus). The triphasic waveform shape of putative axonal recording is common to these descriptions of axonal recordings as well as descriptions of SDWs in white matter tracts in Robbins et al As described in Figure 1 , the triphasic waveform shape arises when a propagating action potential is elicited near the recording electrode.…”

“…These in vitro studies have shown that axons are more than merely reliable conduits for ordered signal propagation and may be directly involved in complex information processing (Debanne, 2004 ; Bucher and Goaillard, 2011 ; Bakkum et al, 2013 ), contribute to high frequency network oscillations (Traub et al, 2003a , b ; Gloveli et al, 2005 ; Dugladze et al, 2012 ) and possess intrinsic breaking mechanisms that can potentially halt seizure propagation (Meeks et al, 2005 ). However, the in vivo recording of axonal activity in freely moving animals has received little attention since early microelectrode recordings were developed (Amassian et al, 1961 ; Cooper et al, 1969 ).…”

Short duration waveforms recorded extracellularly from freely moving rats are representative of axonal activity

“…Our description of SDWs also matches that of classic fiber tract recordings using 3 μm diameter tungsten wires set in micropipettes. Both Amassian et al (1961) and Cooper et al (1969) reported recordings of brief triphasic action potentials approximately 130 μs in duration in a variety of species (cat, squirrel, squirrel monkey) and recording locations (optic tract, geniculostriate fibers in the visual cortex, pons and medulla, and also the cuneate nucleus). Similar to these reports, SDWs were also found to be quite stable (see 24 h recordings of SDWs in Figure 6A ).…”

“…Being able to reliably record waveform activity from axons will provide the opportunity to explore these mechanisms in vivo. While great strides have been made in the diffusion weighted imaging of axonal processes ( Basser and Pierpaoli, 1996 ) as well as the visualization of axonal projections ( Chung et al, 2013 ), in vivo axonal activity, as recorded in freely moving animals, has received little attention since early microelectrode recordings were developed ( Amassian et al, 1961 ; Cooper et al, 1969 ) and remain poorly characterized.…”