Emergent effects of synaptic connectivity on the dynamics of global and local slow waves in a large-scale thalamocortical network model of the human brain
Fig 2
Baseline model activity in awake and sleep states.
A) Wake state. a.1) Membrane voltages of all neurons from layer 2 over 5 seconds of simulation; a.2) Layer average voltage over time, simulating LFP; a.3) Activity of two representative neurons from layer 2, both showing irregular tonic firing; a.4) Voltage histogram of all neurons over the whole simulation time, note approximately -60mV peak representing baseline membrane voltage; a.5) Power spectral density (PSD) of the average voltage revealed a distinct 1/f phenomenon typical for in-vivo recordings. B) Slow-wave dynamics. b.1) Membrane voltages of all neurons (excluding medial wall) from layer 2 over 30 seconds of simulation, revealed synchronized bands of activity during Up states; b.2) Average voltage of all cortical layers (dashed black line) and layer 2 neurons (solid blue line, excluding medial wall) over time, with nearly identical behavior. Red triangles above and below the trace mark global Up and Down states, respectively, from layer 2 (coincident with global Up and Down states from the average of layers); a.3) Activity of two representative neurons from layer 2, both showing synchronized transitions between Up and Down states; a.4) Voltage histogram of all neurons over the whole simulation time, revealed the characteristic bi-modal distribution caused by Up and Down state alternations during SWS. Dashed vertical lines labeled V− and V+ indicate the voltage thresholds used to detect Down states and Up states, respectively; b.5) Distribution of the Up state onsets and offsets for all neurons over the whole simulation time. Narrow histograms indicate highly synchronous initiation and termination of the Up states. C) Zoom into the first Up state from panel b.1, with neurons sorted from earliest to latest onset time, and a single cell voltage from panel b.2, showing the transition from Down to Up state, steady firing during the Up state, and transition to Down state. D) Latency map, calculated as the onset delay of each neuron with respect to the earliest onset, for each Up state in panel b.2 (see Onset/offset detection in Methods for details). The percent of active neurons during each Up state is shown below the corresponding latency map. Up states involve nearly every neuron in the cortex within 300ms from its initiation time.