Abstract
A classical view of neural coding relies on temporal firing synchrony among functional groups of neurons, however, the underlying mechanism remains an enigma. Here we experimentally demonstrate a mechanism where time-lags among neuronal spiking leap from several tens of milliseconds to nearly zero-lag synchrony. It also allows sudden leaps out of synchrony, hence forming short epochs of synchrony. Our results are based on an experimental procedure where conditioned stimulations were enforced on circuits of neurons embedded within a large-scale network of cortical cells in vitro and are corroborated by simulations of neuronal populations. The underlying biological mechanisms are the unavoidable increase of the neuronal response latency to ongoing stimulations and temporal or spatial summation required to generate evoked spikes. These sudden leaps in and out of synchrony may be accompanied by multiplications of the neuronal firing frequency, hence offering reliable information-bearing indicators which may bridge between the two principal neuronal coding paradigms.
Highlights
One of the major challenges of modern neuroscience is to elucidate the brain mechanisms that underlie firing synchrony among neurons
We demonstrate that the underlying biological mechanism to sudden leaps in and out of synchrony is the unavoidable increase of the neuronal response latency (Aston-Jones et al, 1980; De Col et al, 2008; Ballo and Bucher, 2009; Gal et al, 2010) to ongoing stimulations, which imposes a non-uniform stretching of the neuronal circuit delay loops
LEAP TO SYNCHRONY ACCOMPANIED BY A DOUBLED FIRING FREQUENCY Experimental results We first demonstrate leaps to synchrony using a neuronal circuit consisting of four neurons and conditioned stimulations split into weak/strong stimulations (Figure 1A)
Summary
One of the major challenges of modern neuroscience is to elucidate the brain mechanisms that underlie firing synchrony among neurons. Such spike correlations with differing degrees of temporal precision have been observed in various sensory cortical areas, in particular in the visual (Eckhorn et al, 1988; Gray et al, 1989), auditory (Ahissar et al, 1992; Nicolelis et al, 1995), somatosensory (Nicolelis et al, 1995), and frontal (Vaadia et al, 1995) areas. Since the dynamical variations in neuronal features, e.g., the increase in neuronal response latencies per evoked spike, are extremely small, one might expect only very slow variations in firing timings. Sudden leaps, in and out of synchrony, seem unexpected
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