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Dementia in Movement Disorders
Published in W. R. Wayne Martin, Functional Imaging in Movement Disorders, 2019
Declines in the rates of cerebral cortical glucose metabolism in PSP correlate with changes in cognition. The average glucose metabolic rate in the cerebral cortex correlates with severity of intellectual decline as measured by the Wechsler Adult Intelligence Scale.43 The regional distribution of glucose hypometabolism also corresponds to the impairments seen in PSP. Relative loss of skills, such as verbal fluency and memory, are reflected in differing rates of metabolism in various regions of the cerebral cortex.44 Functional impairment of the frontal eye fields may contribute to the pronounced visuomotor abnormalities, and supplementary motor cortex dysfunction may contribute to the abnormalities in initiating movement often seen in these patients. Thus, the clinical symptomatology of PSP is consistent with the abnormalities in glucose metabolism seen by PET.
Neuropsychiatry: brain injury, mental health–substance use
Published in David B Cooper, Practice in Mental Health—Substance Use, 2018
Five major frontal-subcortical circuits have been described for this condition:8Dorsolateral-prefrontal circuit — executive function.Orbitofrontal circuit — social intelligence.Anterior cingulate circuit — motivation and emotional experience.Motor circuit — voluntary motor function.Frontal eye fields — eye movements.
Giacomo Rizzolatti (b. 1937)
Published in Andrew P. Wickens, Key Thinkers in Neuroscience, 2018
In 1971, Rizzolatti began his first experiments on monkeys. One of the brain regions that interested him were the frontal eye fields – an area located in the frontal cortex, just in front of the premotor cortex. This area was known to be involved in the shifting of gaze and the generation of eye movements, especially when tracking a moving object. However, in his attempt to record from neurons in this area, Rizzolatti also came across an adjacent region located in the premotor region itself, which only responded to visual stimuli close to the body or within the monkey’s reaching distance. This was an unexpected finding since this area of the brain was believed to be primarily involved in the planning and execution of motor action through its direct projections to the spinal cord. Rizzolatti also found that many of its neurons were bimodal, responding to both visual and tactile information, as occurs in hand-to-mouth movements. Clearly, the motor areas of the cortex still had secrets to give up, and in an attempt to elucidate their role, Rizzolatti began to map out its regions with new neuroanatomical techniques. According to Rizzolatti, this would show that the motor cortex does not consist of two main areas (e.g. primary and premotor areas) as classic accounts of the brain held but a mosaic of cortical areas with specific connections and functional properties. Rizzolatti would number these areas F1 to F5. Later, he would add two more regions (F6 and F7) to his classification of the premotor cortex.
Depressed skull fracture compressing eloquent cortex causing focal neurologic deficits
Published in Brain Injury, 2023
Alexander In, Brittany M. Stopa, Joshua A. Cuoco, Adeolu L. Olasunkanmi, John J. Entwistle
Traumatic causes of focal neurologic deficits may include intraparenchymal hemorrhage, subdural hematoma, epidural hematoma, or internal carotid artery dissection. However, altered mentation would usually be observed in the presence of intra- or extra-axial hemorrhage that is large enough to cause focal deficits. Although an internal carotid artery dissection may lead to contralateral hemiplegia, it typically is associated with headache, neck pain, or Horner’s syndrome and tends not to disturb the frontal eye fields. In the absence of trauma, the differential diagnosis of the observed symptomatology may include ischemic stroke or seizure activity. Ischemic stroke and seizure activity can certainly present in a similar fashion; however, gaze preference should be a differentiating factor between these diagnoses. In the setting of ischemic stroke, inhibition of the frontal eye field would cause gaze deviation toward the lesion. Comparatively, seizure activity would stimulate the frontal eye field and cause gaze deviation away from the lesion.
Comparison of Functional Connectivity during Visual-Motor Illusion, Observation, and Motor Execution
Published in Journal of Motor Behavior, 2022
Katsuya Sakai, Junpei Tanabe, Keisuke Goto, Ken Kumai, Yumi Ikeda
All channels were referenced to 10–20 system landmarks (nasion, inion, right, and left preauricular points) and recorded using a 3 D digitizer (3 SPACE®, Fastrak®, Polhemus Co., Ltd, Colchester, VT, USA) to determine which brain regions corresponded to each channel positions. All channels then converted these coordinates into the locations of 40 channels based on an estimated Montreal Neurological Institute (MNI) space using NIRS-statistical parametric mapping (NIRS-SPM) (Tsuzuki et al., 2007; Tsuzuki & Dan, 2014). NIRS-SPM transforms the functional image to MNI space using probabilistic registration in reference to 3D digitized data of all channels and landmark positions using the 10–20 system (Tsuzuki & Dan, 2014; Yamazaki et al., 2020). This analysis demonstrated that the regions of interest (ROI) were the dorsolateral prefrontal cortex (DLPFC, channels 1–4), frontal eye field (channels 5–9), PMC (channels 10–22), M1 (channels 23–27), somatosensory area (Sa, channels 28–31), and Pa (channels 32–40).
Disorders of vision in multiple sclerosis
Published in Clinical and Experimental Optometry, 2022
Roshan Dhanapalaratnam, Maria Markoulli, Arun V Krishnan
The supranuclear control of ocular movements is a complex but elegant network receiving input from the brainstem, cranial nerve nuclei, thalamus, basal ganglia and the cerebrum, as well as the vestibulocerebellar system.79 Such is the complexity of the network that several components are responsible for a single eye movement. Frontal eye field regions of the cortex are responsible for central primary gaze and a lesion in this area may result in an ipsilateral gaze deviation.80 Saccades are rapid intentional movements of the eyes to follow targets in the environment and can also be assessed when triggered by testing the vestibuloocular reflex (VOR), which keeps the eyes fixed on a target whilst the head is in motion. In contrast, pursuit is the ability to hold a steady gaze during motion.