Figure 1.

Continuous variations of synaptic noise. (A Left) Representation of the M-cell’s (M) feed forward inhibitory networks (▴, −) and their excitatory inputs (▵, +) issued by eighth nerve primary fibers (VIII n.). Two sets of inhibitory interneurons are shown: the commissural ones (Com.) with their somata in the lateral vestibular nucleus (LVN) and the collateral cells (Coll.). Note the presence of reciprocal connections and feedback loops. Thicker lines outline the connections incorporated in a model, which also includes a history-dependent postanodal firing of the interneurons (Inset). Acoustic waves activate hair cells and induce repetitive discharges (vertical bars) in VIII n. fibers. (Right) Typical background activity with inverted unitary IPSPs (arrows), sampled at 3 kHz (dots), and reference baseline (dashed). (B and C) Analysis of 2 sec of synaptic noise (sampling rate = 3 kHz). (B1 and C1) Digitized data (Upper) and corresponding recurrence plots (RPs; Lower) from two fish showing checkerboard structures with a small scale background suggesting chaos (B1) and long lines parallel to the main diagonal indicating periodic activities embedded in aperiodic ones (C1). (B2 and C2) Larger magnifications of the areas indicated by boxes in the B1 and C1. (D) Fragment of a homogeneous RP obtained with a model of Gaussian series. For all plots, embedding dimensions = 10; Σ_j=1^N_eN_j = 2.5%N_e² ± 2,500 dots; and lag = 8.4, 5, and 0.66 msec for B, C, and D, respectively.