The Evolution of Consciousness
Max R. Bennett in The Idea of Consciousness, 2020
Figure 6.15 shows a frog’s brain in dorsal (C) and lateral (B) view, together with a diagram (A) of the projection of the optic tract to the principal areas of the brain subserving vision. The large size of the optic tectum of the frog, compared with that of the cerebral hemispheres (Figures 6.15A, B and C), reflects the fact that it receives the entire retinal input to the brain, whereas in mammals the optic tectum, or superior colliculus as it is called for these species, receives only part of the retinal projection. It is therefore appropriate to inquire as to whether frogs are conscious of a visual perception in the tectum rather than the telencephalon. This optic tectum has been a source of modelling of neural networks for the reflex control of eye position in the frog. From the tectum, projections occur to motor neurons that control the left medial and right lateral rectus muscles of die eyes as well as to those controlling vertical movement. This tectum has also been subjected to a control system analysis of the process of eye movement involved in saccades (Figure 6.16). According to this theory, a retinotopic mapper occurs in the tectum which projects to a saccade burst generator in the brain stem. This then receives a code for target position as determined by the position of a peak of activity in a neural map. However, all of these considerations of the functioning of the tectum emphasize Dennett’s claim1 that ‘the toad’s status falls to “mere automaton” ‘. The question being asked is: does the tectum give rise to consciousness?
Brain Motor Centers and Pathways
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
The tectospinal tract (Figure 11.3), also known as the colliculospinal tract, is an extrapyramidal motor tract that coordinates head, neck, and eye movements. The tract originates in the superior colliculus, which is situated rostrally, just below the thalamus (Figure 12.17). The superior colliculus, together with the inferior colliculus, comprise the tectum, or roof of the midbrain, in humans. The part of the midbrain between the tectum and tegmentum constitutes the midbrain tegmentum. The two colliculi on each side form four prominences referred to as the corpora quadrigemina.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
(from Latin, tegumentum: a cover) Like the TECTUM, the tegmentum is regarded as part of the MIDBRAIN. The midbrain tegmentum lies immediately above the CEREBRAL PEDUNCLES (with the tectum, the other division of the midbrain) and contains the VENTRAL TEGMENTAL AREA and the SUBSTANTIA NIGRA. The term tegmentum however also covers an area of the PONS, containing a variety of fibre pathways and nuclei such as the PEDUNCULOPONTINE TEGMENTAL NUCLEUS.
The utility of quantitative MRI parameters in discriminating progressive supranuclear palsy from Parkinson’s disease
Published in Neurological Research, 2023
Halil Onder, Bilge Gonenli Kocer, Aynur Turan, Selcuk Comoglu
The crucial point was that we found a PPV of 100% in case of both high P/M and 3rd/bifrontal ventricle rates for the diagnosis of PSP. The gross examination of the brain in PSP often reveals distinctive features. The atrophy in the midbrain, especially the tectum, is the most characteristic finding [24]. However, the subthalamic nucleus atrophy as well as the dilatation of the third ventricle atrophy is also frequently observed in pathology examinations [24]. We think that the existence of the neuroradiological evidence of the atrophy of both of these two regions (mesencephalon and third ventricle) might provide a more reliable and comprehensive finding regarding the underlying PSP pathology. Therefore, instead of the use of complicated parameters such as MRPI and MRPI-2 the scopes of which are limited to the anatomy of the brain stem, we suggest searching for both of these two distinct regions (brainstem, third ventricle) to increase the diagnostic reliability of PSP subjects.
Adults are not older adolescents: comparing physical therapy findings among adolescents, young adults and older adults with persistent post-concussive symptoms
Published in Brain Injury, 2023
Jacob I. McPherson, Mohammad N. Haider, Theresa Miyashita, Lacey Bromley, Benjamin Mazur, Barry Willer, John Leddy
There are different mechanisms by which concussive head injuries can cause the sensation of dizziness. There can be trauma to the peripheral vestibular structures that receive and transmit sensory information and movement, including the utricle, saccule, semicircular canals and the vestibular portion of the eighth cranial nerve (9), or to the central vestibular structures such as the vestibular nuclear complex in the brainstem, the cerebellum, as well as structures of the reticular activating system, midbrain, and higher centers of cortical function (10). Pathology of the central vestibular structures can affect integration and processing of sensory input from the vestibular, visual, and somatosensory systems. In addition to vestibular causes, other post-concussive disorders that are associated with the sensation of dizziness include orthostatic intolerance syndromes (11) and cervical disorders (12).
Resection of the piriform cortex for temporal lobe epilepsy: a Novel approach on imaging segmentation and surgical application
Published in British Journal of Neurosurgery, 2021
Jose E. Leon-Rojas, Sabahat Iqbal, Sjoerd B. Vos, Roman Rodionov, Anna Miserocchi, Andrew W McEvoy, Vejay N Vakharia, Laura Mancini, Marian Galovic, Rachel E Sparks, Sebastien Ourselin, Jorge M Cardoso, Matthias J Koepp, John S Duncan
A single retractor was used to access and visualise the posterior temporal horn. The hippocampus was dissected free from its mesial attachment, the fimbria. Dissection through the fimbria exposed the hippocampal arcade overlying the mesial-most aspect of the parahippocampal gyrus. The dissection was then carried forward and the pes hippocampi, which forms the bulk of the posterior uncus was then divided along this plane. The remaining head, body and tail of the hippocampus were subsequently resected to the level of the tectum. After resection of the hippocampus, the remaining parahippocampal gyrus was removed using a subpial dissection technique and ultrasonic aspirator. The pes hippocampi were then removed to complete the resection of the uncus. The superior-most remnant of the amygdala was then resected and subpial dissection was performed along the inferior aspect of the endorhinal sulcus, using the 3D representation of the PC to aid resection. Care was taken not to breach the pia of the endorhinal sulcus so as not to damage the lateral lenticulostriate perforators. After macroscopic resection of the PC, an intra-operative MRI scan was performed prior to closure to confirm removal of the temporal portion of piriform cortex (Figure 5).
Related Knowledge Centers
- Alertness
- Brainstem
- Cerebral Aqueduct
- Diencephalon
- Pons
- Posterior Cranial Fossa
- Cerebrum
- Cerebral Peduncle
- Tegmentum
- Tentorial Notch