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Anatomy of the head and neck
Published in Helen Whitwell, Christopher Milroy, Daniel du Plessis, Forensic Neuropathology, 2021
The midbrain is divided into anterior and posterior portions at the level of the cerebral aqueduct. The anterior portion is termed the ‘tegmentum’ and is bounded by the crus cerebri. The posterior portion is the tectum, made up of the inferior and superior colliculi (corpora quadrigemina). The inferior colliculus forms part of the ascending auditory pathway whereas the superior colliculus is part of the visual system.
Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
The superior colliculus is a layered, multi-sensory structure that receives inputs from the retina, the visual, parietal, and frontal cortices, as well as inputs from the auditory and somatosensory systems. The superior colliculus has a major ascending projection to the frontal cerebral cortex through the medial dorsal nucleus of the thalamus. It projects to the nuclei controlling extraocular muscles that mediate eye movements, and to the cervical spinal cord through the tectospinal tract.
Neuro-ophthalmology
Published in Mostafa Khalil, Omar Kouli, The Duke Elder Exam of Ophthalmology, 2019
The eye movements are under voluntary or reflex control. The voluntary movements are initiated in the frontal eye field (FEF), Brodmann area 8, in the frontal lobe. The reflex movements are coordinated via the occipital cortex and superior colliculus in response to a visual stimulus.
Effect of selective attention on auditory brainstem response
Published in Hearing, Balance and Communication, 2023
Sathish Kumar, Srikanth Nayak, Arivudai Nambi Pitchai Muthu
The mean amplitude of peak V in active listening condition was larger than the peak V of passive listening with visual distractor and visual task conditions. However, the statistical difference was observed only in the contralateral response between active listening and passive listening with visual distractor condition. This result evidence the attentional modulation of brainstem activity. Increased peak V amplitude in the active listening condition can be attributed to the enhanced activity in the inferior colliculus due to attention [14]. Using functional Magnetic Resonance Imaging (fMRI) technique [14], demonstrated that attention enhances inferior colliculus activity through indirect activation of the superior colliculus. However, the statistical difference was seen only in the contralateral montage, not in the ipsilateral montage. This result can be attributed to the cross-over of the auditory fibres above the cochlear nucleus [45]. Also, the corticofugal system of the auditory cortex sends more dense projections to the ipsilateral peripheral structures than the contralateral structure [8]. Therefore, the attentional modulational would have more effect on the fibres’ responses crossed over to the other side.
Spatial neglect treatment: The brain’s spatial-motor Aiming systems
Published in Neuropsychological Rehabilitation, 2022
A. M. Barrett, Kelly M. Goedert, Alexandre R. Carter, Amit Chaudhari
Damage to subcortical structures has also been associated with spatial Aiming bias. In the same study of the neural correlates of directional hypokinesia that implicated frontal lobe regions, Sapir et al. (2007) also reported a strong association of this bias with damage of the ventral lateral putamen and claustrum, and speculated that this might result in a disruption of subcortical dopaminergic neurotransmission which can play an important role in spatial cognition as discussed above (Sapir et al., 2007). Another subcortical structure, the mammalian superior colliculus (SC) is a major hub of sensorimotor integration and neurons in deep layers of the SC are crucial to the generation of contraversive saccadic eye movements (Robinson, 1972). In addition, the SC has other motoric functions (Gandhi & Katnani, 2011), including multiple classes of neurons that are active prior to and during arm movements, and which may contribute to the control of visually-guided movements (Lunenburger et al., 2001).
Neural Organoids and the Precautionary Principle
Published in The American Journal of Bioethics, 2021
Jonathan Birch, Heather Browning
Yet no theory about the neural correlates of conscious experience (NCCs) in humans is uncontroversial, and different groups of researchers emphasize different brain regions and processes. Some argue that conscious experience depends on local activity in a particular area of the cortex, perhaps the “posterior hot zone” (Koch et al. 2016), while others argue that conscious experience depends on global ignition of many cortical regions (Mashour et al. 2020). Some highlight the role of thalamocortical connections (Aru et al. 2019), while others argue that midbrain regions such as the superior colliculus may be sufficient by themselves for conscious experience (Merker 2007). While views that focus on the cortex and the thalamus are considered more mainstream than Merker’s midbrain-centred view, none can be decisively ruled out.