Fig. 1.

Neuronal adaptation as a neurobiological correlate of WM. (A) Adaptive neuron is driven by a step current with amplitude 400 pA for a duration of 300 ms. Tonic spiking with uniformly spaced interspike intervals (Left) due to a refractory conductance $g_{\text{ref}}$ (blue). Spike rate conductance $g_{\text{sra}}$ (red) adaptively decreases excitability and stretches out spike times (Right). Both conductances are spike-triggered but differ in magnitude and their decay time constants. (B) f–I curves show neuronal spike rates as a function of input current strength. As the time constant ${\tau }_{\text{sra}}$ of $g_{\text{sra}}$ increases (from 10 ms to 1.5 s; Left), spike rates decrease (black to gray gradient) because neuronal adaptation lasts longer. Likewise, as the magnitude of the spike-triggered change $\mathrm{\Delta }{g}_{\text{sra}}$ increases (from 1 to 200 nS; Right), spike rates decrease (black to gray gradient) because adaptation becomes stronger. (C) Single neuron spike response (green dots) to a Poissonian input stimulus (orange; 0.5 kHz) from 50 presynaptic neurons, when preceded only by background noise (black; 0.25 kHz) or another sensory stimulus (blue; 0.5 kHz). (D) Histograms display SRA (dashed line indicates mean) which encodes context-dependent neuronal behavior in response to the orange stimulus. Memory of the blue stimulus is maintained in the hyperpolarized membrane state of the postsynaptic neuron (green). (E) Population-averaged memory traces $g_{\text{sra}}$ (red) over time, induced by a sequence of three items (y position of traces aligned with corresponding population). (F) Linear combination of these traces can distinguish the sequential order of inputs (123, 231, or 312) after stimulus offset (dashed line).