Memory recalls can be triggered by associative linkages. The first type of associative linkage in neural circuits is the action of resonance among IFPs (impulse firing patterns), discussed in the last article. The second type is feedback. Resonance and feedback are similar in that they trigger responses in neural circuits, but are different in that resonance is omnidirectional while feedback is directional. Feedback IFPs and resonant IFPs may need to be similar or inductive 1 to the responding IFPs for the response to happen. The direction of neural feedback is charted by synaptic connections and influenced by the flow and distribution of neurochemicals. As such, neural circuits are clusters of strongly synaptically connected neurons and their surrounding neurochemicals/nutrient supplies. These circuits host and facilitate playbacks of particular IFPs that are equivalent to particular perceptions / memories / feelings / thoughts.
note 1: Resonance by induction. For example, the oscillating air column movement (movements 1) of the flute is induced by a mouth blowing air partially into the flute hole and partly outside the hole (movements 2). And the oscillating movement on the stretched surface of a drum head is induced by the movement of a mass hitting the surface of the durm. The two movement systems are not similar. The movement of one system is oscillatory consequent to factors introduced by the other system: pressure differential, reaction overshoots to pressure differential that creates a reverse pressure differential, reaction overshoots to reverse pressure differential that lead back to pressure differential again, and so on. This resonance is just vibration. The other type of resonance is when one system moves in a similar way to that movements introduced by the other system. This is more like echo or biomimicry and not necessarily sound-making.