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The Arbitrary Mapping of Sensory Inputs to Voluntary and Involuntary Movement: Learning-Dependent Activity in the Motor Cortex and Other Telencephalic Networks
Published in Alexa Riehle, Eilon Vaadia, Motor Cortex in Voluntary Movements, 2004
Peter J. Brasted, Steven P. Wise
-5 0 5 10 15 Normalized Trial Number FIGURE 10.5 Three subpopulations of cells in the supplementary eye field (SEF), showing their change in activity modulation during learning (filled circles, right axis). Also shown is the monkeys' average learning rate over the same trials (unfilled circles, left axis). In the upper right part of the figure is a depiction of the display presented to the monkeys. The monkeys fixated the center of a video screen, and at that fixation point an initially novel stimulus (?) appeared. Later, four targets were presented, and the monkey had to learn — by trial and error — which of the four targets was to be fixated in order to obtain a reward on that trial in the context of that stimulus. The arrow illustrates a saccade to the right target. (A) The average activity (filled circles) of a population of neurons showing learning-dependent activity that increases with learning, normalized to the maximum for each neuron in the population. Learning-dependent activity was defined as significant modulation, relative to baseline activity, for responses to both novel and familiar stimuli. Unfilled circles show mean error rate (for a moving average of three trials), aligned on the first occurrence of three consecutive correct responses. Note the close correlation between the improvement in performance and increase in population activity. (B) Learning-dependent activity that decreases during learning. (C) Learning-selective activity, defined as neuronal modulation that was only significant for responses to novel stimuli. (Data from Reference 129.)
Clinical testing of mild traumatic brain injury using computerised eye-tracking tests
Published in Clinical and Experimental Optometry, 2022
Alice Cade, Philip RK Turnbull
Anti-saccades are voluntary saccades directed away from a presented target. They require the participant to inhibit their initial reflex to look towards the target and instead look away from the target.35 Compared to a conventional pro-saccade, this inhibition requires input from additional brain centres,40 making anti-saccades a useful tool for assessing diffuse brain injury post-mTBI. Nominally, anti-saccadic latency is about 30% higher than pro-saccades, and this longer latency is thought to represent the additional cognitive effort in the parietal cortex,41 frontal eye fields42 and supplementary eye fields needed to shift visual attention and inhibit a reflexive saccade towards the target.42,43 Patients with mTBIs would be expected to show an increased anti-saccade latency of around 40-50 ms over the typical delay of 240 ms in non-mTBI patients.40,41 These latency effects persist for approximately one week,40 potentially making anti-saccadic latency a good measure to distinguish if an acute mTBI has occurred. Interestingly, participants with previous mTBIs exhibit a deficit in anti-saccade accuracy (i.e. whether the participant performs the test correctly) for over five years post injury.44
Fixation stability as a biomarker for differentiating mild traumatic brain injury from age matched controls in pediatrics
Published in Brain Injury, 2021
Melissa Hunfalvay, Nicholas P. Murray, Frederick Robert Carrick
Depending on the type of eye movement, different brain regions become activated (12). For example, fixations involve specific cerebral and brainstem structures (11). These cerebral structures include the Parietal Eye Field (PEF), the Supplementary Eye Field (SEF), middle temporal and medial superior temporal areas, and the dorsolateral prefrontal cortex (12). Additionally, the Frontal Eye Field (FEF) neurons fire at the beginning of and during fixations (13). The brainstem also impacts fixations and includes the substantia nigra pars reticulata of the basal ganglia and the rostral pole of the Superior Colliculus (SC) (10). Examining the neurocircuitry regulating oculomotor behavior is valuable to understanding both normal functioning and the pathophysiology of diseases and injuries, including concussion (14,15).
Saccadic Eye Movements in Young-Onset Parkinson’s Disease - A BOLD fMRI Study
Published in Neuro-Ophthalmology, 2020
Anshul Srivastava, Ratna Sharma, Vinay Goyal, Shefali Chaudhary, Sanjay Kumar Sood, S. Senthil Kumaran
Functional neuroimaging has proved useful in exploring the saccadic circuitry and its intersection with cognitive circuitry.11 Furthermore, imaging studies have reported that saccadic tasks which involve inhibition of saccades versus simple visually guided saccades show different activation patterns. Greater blood-oxygen-level-dependent (BOLD) activity in the Frontal eye field (FEF) is attributed to saccadic initiation and reaction time.12 The supplementary eye field (SEF), a part of the medial frontal cortex is linked to saccadic tasks, which require performance monitoring.13 The frontal eye fields have been found to be activated more during response selection and saccadic goals.14 The frontal eye field is functionally distinct within itself where the lateral and medial FEF are involved in reflexive and volitional saccades respectively. The parietal eye field (PEF) and superior colliculus (SC) are also closely associated with reflexive saccades.12 The dorsolateral prefrontal cortex (DLPFC) is involved in the decision- making process by inhibiting undesirable reflexive saccades and therefore provides top down control of saccades.15 Error monitoring and saccadic inhibition are associated with anterior cingulate (ACC) activity as seen in antisaccades.12