The intralaminar and midline nuclei of the thalamus. Anatomical and functional evidence for participation in processes of arousal and awareness

Spikes, synchrony, and attentive learning by laminar thalamocortical circuits

“…The Synchronous Matching Adaptive Resonance Theory (SMART) model that is presented here shows how bottom-up and top-down pathways work together to accomplish this goal by coordinating processes of learning, attention, expectation, resonance, and synchrony. In particular, SMART explains how attentive learning requirements are realized by detailed brain circuits, notably the layered organization of cells in neocortical circuits and how they interact with first-order (e.g., the lateral geniculate nucleus, LGN) and higher-order (e.g., the pulvinar nucleus, PULV; Sherman and Guillery, 2001;Shipp, 2003), and nonspecific thalamic nuclei (van Der Werf et al, 2002).…”

“…Nonspecific thalamic nuclei, such as the midline and intralaminar nuclei (van der Werf et al, 2002), as well as "matrix" cells in the specific thalamic nuclei (Jones, 2002), derive their name from the fact that they receive diffuse innervations from the sensory periphery and the reticular formation, and project diffusely to the superficial layers of the cerebral cortex (Figure 1b).…”

“…The Synchronous Matching Adaptive Resonance Theory (SMART) model that is presented here shows how bottom-up and top-down pathways work together to accomplish this goal by coordinating processes of learning, attention, expectation, resonance, and synchrony. In particular, SMART explains how attentive learning requirements are realized by detailed brain circuits, notably the layered organization of cells in neocortical circuits and how they interact with first-order (e.g., the lateral geniculate nucleus, LGN) and higher-order (e.g., the pulvinar nucleus, PULV; Sherman and Guillery, 2001;Shipp, 2003), and nonspecific thalamic nuclei (van Der Werf et al, 2002).Corticothalamocortical pathways work in parallel with corticocortical routes (Maunsell and Van Essen, 1991;Salin and Bullier, 1995;Sherman and Guillery, 2002). Specific first-order thalamic nuclei relay sensory information to the cerebral cortex, whereas specific second-order thalamic nuclei receive their main input from layer 5 of lower-order cortical areas and relay this information to higherorder cortical areas (Sherman and Guillery, 2002, Figure 1a).…”

“…The term nonspecific, as opposed to specific, thalamic nuclei (both first-order and second-order nuclei), refers to the midline thalamic and the intralaminar nuclei. The term nonspecific derives from three characteristics of these nuclei, namely: (1) their diffuse innervation from pontine, medullary and mesencephalic reticular formation; (2) the signature of their stimulation in the cortical mantle (somnolence for low-frequency stimulation, arousal for high-frequency); and (3) the anatomical observation that they project to cerebral cortex in a fairly uniform fashion (Van der Werf et al, 2002). Most of the nonspecific thalamic nuclei are characterized by a high degree of convergent cortical input, widespread projections to large portions of neocortical layer 1, inhibition from the thalamic reticular nucleus (TRN), and strong neuromodulatory input from several brainstem centers (Van der Werf et al, 2002).…”

“…Anatomical studies in monkeys, cats and rats have established that the nonspecific thalamus (in particular, the midline and central lateral thalamic nuclei), whose activation is sensitive to the degree of mismatch, projects to the cholinergic nucleus basalis of Meynert (van Der Werf et al, 2002), one of the main source of cholinergic innervations of the cerebral cortex. The nucleus basalis of Meynert is also influenced by noxious stimulation and cortical control (Zhang et al, 2004).…”