Figure 6. Dynamic clamp experiment.

(A) Intracellular recording of a perirhinal cortex neuron in dynamic clamp mode. The computer simulates the state of clusters of cooperative channels given the measured membrane potentials and emulates the effect of their conductance to the neuron’s activity by inserting a corresponding current. (B) Neurolucida drawing of the recorded neuron. (C) Graded persistent activity of the recorded neuron mediated by the multi stable conductance of the clusters of cooperative channels. (D) Hyperpolarization brings the cell back to rest via intermediate levels of persistent firing. In control recordings with identical, yet- independent channels, no persistent firing was observed (Figure 6—figure supplement 1). Slice preparation, electrophysiological setup and the dynamic clamp emulation of the clusters are described in Material and methods. Cluster parameters are summarized in Table 1.

Figure 6—figure supplement 1. Cooperative interactions are necessary to mediate graded persistent activity.

Control experiment to demonstrate the requirement of cooperative channel interactions for graded persistent activity in a perirhinal cortex neuron. Top: When the channels gated independently (red, J=0 mV), the neuron only fired during the stimulating pulses and otherwise remained silent. When, in contrast, the channels cooperate strongly (black, J=101.5 mV), the cell produced graded persistent activity (this trace is the full trace of the extract shown in Figure 6). Bottom: The independent channels reacted to spiking activity only in a transient way and remained closed after the stimulus. In contrast, cooperative channels opened and facilitated their neighbors to open as well. In this way, spiking could open whole clusters, which remained open after the stimulus and drove persistent activity. A detailed description of the dynamic clamp experiment is given in Material and methods. Cluster parameters are summarized in Table 1.