Van der Werf et al. - Midline Thalamic Nuclei

The Structure of Concern Project compares many theoretical models from many disciplines to the Adizes PAEI model, arguing that they must all be reflecting the same underlying phenomenon. One concern structure model is described below.

Functional localization in the thalamus, specifically in the midline and intralaminar nuclei, have a fairly direct bearing on concern structure patterns. Once thought to have a diffuse, global arousing effect upon the brain, these nuclei are now know to have specific cognitive, sensory and motor functions, involving not arousal so much as aware processing. To better understand the connectivity of these nuclei, Van der Werf et al. (2002) traced their afferent and efferent projections. They found that the midline and intralaminar thalamic nuclei are clustered into four groups, each with its own cortical and subcortical input and target structures.

The groups are described below in a very tentative PAEI order:

P – Limbic Motor Group (Posterior nuclei)
This group generates motor responses upon awareness of salient stimuli. It consists of the centre median and parafascicular nuclei, and heavily targets the basal ganglia, including the caudate, putamen and notably some pallidal targets as well: globus pallidus, subthalmic nucleus and substantia nigra. In fact, this group's projections cover the striatal projections of all the other midline and intralaminar nuclei, resulting in a double projection from these nuclei across the entire striatum. Strong return projections to the centre median from the putamen and dorsolateral caudate result in a closed sensorimotor loop. Parafascicular nuclei innervate the ventral and medial striatum, participating in limbic-associative motor processes. The strong involvement in motor control places this group with the P concern area of short-term/immediate goal achievement.

A – Cognitive Group (Lateral nuclei)
The lateral cognitive group includes the central lateral and paracentral nuclei, and the anterior part of the central medial nucleus. These nuclei project heavily to prefrontal and anterior cingulate cortices. Damage to this area can produce neglect, inattention and hypersomnolescence. It is also associated with the disruption of executive functions, leading to cognitive inflexibility and working memory disruptions. A-type coping and management skills rely very heavily on these kinds of executive functions, and they are vulnerable to the abovementioned disruptions.

E – Multimodal Sensory Processing Group (Ventral nuclei)
Made up of the reuniens and rhomboid nucleus and the posterior part of the central medial nucleus, this group does not project significantly to the striatum, unlike other groups. Instead, it targets primary and associative sensory and motor cortices, as well as parahippocampal cortices and the hippocampus proper. On the basis of this connectivity, Van der Werf et al. suggest that this group influences higher order affective, polysensory and cognitive processes. Reliable functional studies of this region are scarce. Expanding cross-modal awareness and sensory orientation help define the expanded zone of awareness for E’s pattern-seeking behavior.

I - Viscero-Limbic Group (Dorsal nuclei)
This clustering of the paraventricular, parataenial and intermediodorsal nuclei is characterized by output to the amygdala and the medial nucleus accumbens. This group also has the greatest connectivity with the medial prefrontal cortex. It participates with the other groups in outputs to the entorhinal and agranular insular areas, and also receives more monoaminergic input than the other groups, as well as input mediated by nitrous oxide. The paraventricular nucleus has been associated with stress and fear, and corticotrophin releasing hormone is present within it. Other viscerosensory functions include state-setting, visceral feedback and motivated arousal. This region is sensitive to cocaine conditioning. It is placed within the I domain largely because of its input-output relationships with important parts of the social brain.

In contrast with the strictly organizational observations regarding the synaptic organization of thalamic glomeruli, these four groups of thalamic nuclei subserving four different modes of awareness bear directly upon observed behaviors categorized within the structure of concern. The thalamus is also closely involved with the adjacent zona incerta, which is also organized in a fourfold manner relevant to the structure of concern.

1. Van der Werf, Y. D., Witter, M. P., & Groenewegen, H. J. (2002). “The intralaminar and midline nuclei of the thalamus. Anatomical and functional evidence for participation in processes of arousal and awareness.” Brain Research Reviews, 39, 107-140.
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