Figure 2.

Neuromodulation of the claustrocortical loop. (A) A simplified model consisting of the claustrum, the cortex and various neuromodulatory structures that release serotonin (5-HT), acetylcholine (ACh) and dopamine (DA). The claustrocortical loop (Pathway 1) consists of the claustrum and the cortex causing either a net excitation or inhibition of each other. Both the claustrum (Pathway 2) and cortex (Pathway 3) receive heavy input from the neuromodulator pathways. These neuromodulator pathways are also capable of regulating themselves (black box 4). (B) An illustration of claustrum input to the cortex. A claustral projection neuron (PN) receiving a brief stimulus will fire action potentials, which sends excitatory input into cortex. The cortical interneuron (IN) fires action potentials due to the excitation and subsequently inhibits the cortical PN. The cortical PN, receiving feed-forward inhibition through the cortical IN and excitation by the claustral PN, might initially fire action potentials and will remain silent during the period of inhibition by the cortical IN. Conversely, a subset of cortical PN will be directly excited by the claustral PN. These changes in cortical PN and IN activity would typically last for 100–200 ms or until claustral PN activity is diminished.