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The Holistic Nature of Consciousness
Published in Max R. Bennett, The Idea of Consciousness, 2020
Francis Crick7 has suggested that the attentional mechanism for this process is centered in the thalamus. The sensory inputs to the neocortex arise from the thalamus (Figure 3.13). The principal neurons of the thalamus in turn receive connections from such sources of sensory information as the retina. The principal neurons in the thalamus are surrounded by a concentric layer of neurons called the reticular complex; this receives connections from the neocortex as well as from axons that leave the thalamus on their way to the neocortex. Most importantly, these reticular neurons make connections with the principal neurons of the thalamus that are only inhibitory. Within the thalamus itself there is another set of neurons, called the pulvinar, which also receives connections from the neocortex as well as projecting extensively to the neocortex. These pulvinar neurons, like those of the reticular complex, make inhibitory connections with the principal neurons of the thalamus. Crick has argued that if there exists consciousness of a particular aspect of the visual field then an attentional mechanism is operating that involves the reticular complex and the pulvinar. Neurons in these structures depress the sensory input from the thalamus to the neocortex that is not relevant to solving the binding problem associated with this particular aspect. The neuronal groups in the visual neocortex that are solving this problem are therefore given an excitatory advantage over those solving other binding problems.
The Epileptic Baboon, Hypothetical Neuronal Network and Action of Anticonvulsant Drugs
Published in Carl L. Faingold, Gerhard H. Fromm, Drugs for Control of Epilepsy:, 2019
Christian Menini, Carmen Silva-Barrat, Robert Naquet
The participation of subcortical nonspecific visual structures in PD induction does not appear essential since their lesion has little effects on photosensitivity. Bilateral lesion of the pulvinar is followed by a transitory decrease in the frequency of occurrence of ILS-induced PD. Since PD returned fully 1 week later, it was considered that this nucleus neither exerts a direct action in the elaboration of PD, nor is necessary for the transmission of PD-eliciting visual afferents to the FR cortex.39 Bilateral lesion of the superior colliculus has also only transitory effects on photosensitivity.53
Return to activity following concussion
Published in Brian Sindelar, Julian E. Bailes, Sports-Related Concussion, 2017
Brian Sindelar, Julian E. Bailes
A 14-year-old athlete sustained a total of four concussions playing middle school football, and remained symptomatic with headaches and dizziness. He was also noted to display a progressive deterioration in his school performance and an intermittent motor skill dysfunction leading to withdrawal from his classes. A brain MRI was obtained that was significant for a high-intensity lesion in the right pulvinar region (posterior lateral portion of the thalamus). Similarly to case I, presence of a structural abnormality along with progressive decline in cognitive functioning prompted counseling of the patients to cease all contact sport participation.
Thalamic neuromodulation in epilepsy: A primer for emerging circuit-based therapies
Published in Expert Review of Neurotherapeutics, 2023
Bryan Zheng, David D. Liu, Brian B Theyel, Hael Abdulrazeq, Anna R. Kimata, Peter M Lauro, Wael F. Asaad
Because classification schemes based primarily on local anatomy and histology do not capture the functional heterogeneity of individual thalamic nuclei, some modern thalamic classification systems are based on circuit topology[26]. Distinctions have been made based on (i) the characteristics of thalamocortical output – core versus matrix nuclei[27], (ii) input – first- versus higher-order nuclei[28], or (iii) both input and output[29]. For example (of [i]), the anterior nucleus of the thalamus (ANT) has been defined as a core nucleus because it provides focal projections as a node in the medial limbic circuit. The pulvinar nucleus, specifically the PuM, also possesses ‘core-like’ properties based on its distinct circuits involving the temporal lobe[24]. In contrast, matrix nuclei like the centromedian nucleus of the thalamus (CMT) are characterized by markedly more diffuse cortical projections[30]. Meanwhile, within the framework of the first- and higher-order nuclear scheme (ii): first-order nuclei receive ‘driver’ inputs from subcortical sites carrying primary sensory information (e.g. lateral geniculate nucleus [LGN] receives visual input from the retina), while higher-order nuclei (e.g. the pulvinar) receive driver inputs from cortical layer V and primarily participate in transthalamic cortico-cortical circuits[28]. This classification scheme is useful in that it highlights how the thalamus continues to be involved in information processing between areas of cortex in addition to modulating and relaying primary sensory information.
Thalamocortical neural responses during hyperthermia: a resting-state functional MRI study
Published in International Journal of Hyperthermia, 2018
Jing Zhang, Shaowen Qian, Qingjun Jiang, Guanzhong Gong, Kai Liu, Bo Li, Yong Yin, Gang Sun
Additionally, the temporal-thalamic connectivity was increased in the thalamic pulvinar with the posterior inferior temporal gyrus. This finding might reflect neural activity redistribution within temporal lobe. The inferior temporal gyrus processes visual stimuli of objects in our field of vision and is associated with memory and memory recall to identify that object. It is associated with the processing and perception created by visual stimuli, comparing that processed information to stored memories of objects to identify the object [39]. Disrupted connections in the pathways might result in altered visual information perception and processing. This finding might provide potential explanations for our previous study, which declared impaired early stage of face recognition during hyperthermia [40]. Additionally, compared with the frontal-thalamic and somatomotor-thalamic connectivity, the temporal-thalamic connectivity was relatively preserved during hyperthermia. The diversity indicated hyperthermia had selective impact on cortical-thalamic pathways.
Hyperactivity in motor response inhibition networks in unmedicated children with attention deficit-hyperactivity disorder
Published in The World Journal of Biological Psychiatry, 2018
Isabelle Massat, Hichem Slama, Thomas Villemonteix, Alison Mary, Simon Baijot, Ariadna Albajara Sáenz, Danièle Balériaux, Thierry Metens, Martin Kavec, Philippe Peigneux
Between-groups comparison disclosed higher RI-related activations (SS > SF contrast) in children with ADHD than TDC in a set of brain regions including the striatum (left caudate, bilateral putamen), the right insula and the right cingulate cortex (CC) (Table 2a, Figure 2). No higher RI-related activation was found in TDC as compared to children with ADHD. A priori-based ROI analyses disclosed higher RI-related activations in children with ADHD than TDC in the right caudate nucleus, bilaterally in the pallidum and the thalamus/pulvinar, and in the rIFG (Table 2b, Figure 2). No differential effects were found in the SMA/pre-SMA, and the STN ROIs. Differences in the right caudate and in the bilateral pulvinar remained significant after correction for multiple comparisons. Data inspection indicates a similar pattern of activation in all reported regions, with a higher than baseline signal change for SS trials in children with ADHD, whereas in TDC, responses were close to or below the baseline level (Figure 2). SF trial-related responses were close to or below the baseline in children with ADHD, whereas no significant changes were observed in TDC, except for the CC, in which activity was above the baseline in both groups (Figure 2). It is worth noting that in the rIFG, the right insula and right cingulate cortex, SF trial-related BOLD responses were higher in TDC than in children with ADHD. Inclusion of IQ, SSRT and age as potentially confounding covariates and comparison of subsamples by gender did not change the reported results (data not shown).