THEORY-1346: In rat cortical slices with synapses blocked, extracellular fields of the local field potential's size, applied by an electrode, shift the membrane potential of layer 5 pyramidal neurons by less than 0.5 mV at frequencies up to 100 Hz and, with spiking driven by current, phase-lock spike times without changing spike counts, most effectively for slow fields, and synchronize nearby neurons; the authors explain the effect by Kirchhoff's circuit laws and a fixed firing threshold

Source

Anastassiou, Perin, Markram & Koch (2011), LIT-1953, pp. 217–222 and the online methods; read in NOTE-1516.

What was actually shown

• Subthreshold, n = 23: membrane oscillations of 0.16 mV at 1 Hz and 0.14 mV at 100 Hz for I₀ = 100 nA, anti-phase with the extracellular potential (p. 218).
• Spiking, n = 25, each condition paired with a control: spike counts unchanged, phase locking rising with field strength, significant at 1 Hz from 0.74 mV/mm (P = 6.5 × 10⁻⁵) and at 8 Hz (P = 0.019), and at 30 Hz only near 5.6 mV/mm (p. 220).
• Synchrony: four simultaneously patched neurons clustered their spikes near 270° under a common 1 Hz field (p. 221).

Each could have come out otherwise: the membrane response could have been filtered at high frequency, as intracellular injection is, or the timing shift could have come with a rate change that explained it. Neither happened.

What this does not say

• That this happens in vivo. The fields were applied; the matched amplitudes are an argument.
• That brain activity is not locally describable. The authors’ own explanation is circuit physics (p. 221).
• Anything about attention or experience (LIT-388).