Cingulate Cortex What And Where

Cingulate cortex is located in the medial walls of the cerebral hemispheres and is a subset of "limbic

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cortex." Limbic cortex includes all areas that receive fibers of anterior thalamic neurons. By modern convention, the subset of limbic cortex constituting cingulate cortex includes Brodman's areas 24 and 29 in small animals such as rabbits and rats. These and an additional area (23) constitute cingulate cortex in primates. A cytoarchitectural map of the primate limbic cortex is shown in Fig. 1.

Brodman's areas 24 and 29 are often referred to respectively as anterior and posterior cingulate cortex. Neurons in both areas receive afferent fibers from the anterior medial (AM) thalamic nucleus. However, the anterior cingulate cortex (area 24) is also innervated by projections of the medial dorsal (MD) and parafasci-cular thalamic nuclei. Neurons in the posterior cingu-late cortex (area 29) receive projections from all members of the anterior group of nuclei, the anterior ventral (AV), anterior dorsal, and the AM nuclei, as well as the ventral anterior and lateral dorsal thalamic nuclei. Neurons in midline and intralaminar thalamic nuclei send axons to both the anterior and the posterior cingulate cortex.

Cingulate cortical neurons are robustly responsive to multimodal (auditory, visual, somatic sensory, and visceral) stimuli, and they are richly innervated by fibers of the pons and midbrain that distribute the biogenic amines (dopamine, norepinephrine, and serotonin) as well as acetylcholine. Whereas norepi-nephrine, serotonin, and acetylcholine fibers fairly uniformly innervate both the anterior and the posterior cingulate cortex, only anterior cingulate cortex receives appreciable amounts of dopamine. Many additional afferent systems course to the cingulate cortex, including fibers from visual cortex, hippocampus, subiculum, entorhinal cortex, and amygdala. Cingulate cortical neurons send efferent fibers to most of the aforementioned thalamic areas, the subiculum, entorhinal cortex, and pons and to many areas of the striatal motor system, including the caudate nucleus, nucleus accumbens, and zona incerta. Moreover, in primates, cingulate cortical neurons project to multiple areas of the motor and premotor cortex. Thus, numerous parallel pathways exist whereby cingulate neurons can modulate motor output systems of the brain. Finally, the work of Patricia Goldman-Rakic and colleagues has demonstrated direct reciprocal projections of cingulate cortical neurons in primates to the lateral prefrontal and parietal cortex, areas involved in high-level perceptual and mnemonic functions.

Figure 1 Cytoarchitectural map of the limbic cortex in the rhesus monkey based on Brodman's divisions.

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