Term
| Lower level control consist of |
|
Definition
|
|
Term
| The brainstem network that generates premotor commands for saccades |
|
Definition
| burst neurons and ominipause neurons |
|
|
Term
|
Definition
| processes, includes primary structures involved in the actual generation of the pulse step controller signal to the oculomotor neurons |
|
|
Term
| The primary higher level control sturtures include |
|
Definition
| the frontal eye fields, parietal lobes, superior colliculus, and the cerbellum |
|
|
Term
|
Definition
| contain the Burst Neurons for horizontal saccades; Primary center responsible for generating horizontal conjugate gaze |
|
|
Term
|
Definition
| contain the burst cells for vertical saccades. |
|
|
Term
| Short- Lead (Excitatory Burst Neurons) |
|
Definition
| begin high frequency firing just before and during a saccade. They produce the pulse of neural activity that is correlated with the peak velocity and amplitude of a saccade. |
|
|
Term
| Long- Lead Excitatory Burst Neurons |
|
Definition
| exhibit firing rates that are of low frequency and irregular, and their activity may occur several hundred milliseconds before a saccade. They are probably involved in synchronization of overall premoter saccadic pulse generations |
|
|
Term
|
Definition
| are located in the nucleus raphe interpositus (RIP) of the midbrain, fire continuously except just before and during a saccade |
|
|
Term
| Four types of cells in PPRF |
|
Definition
| Burst Cells, Pause Cells, Inhibitory Burst Cells, Tonic Cells |
|
|
Term
|
Definition
| generate horizontal saccades that are ipsilateral to the N.VI. These discharge only when the need for a saccade arises. There are the long-lead (LLBN), and short-lead (EBN) burst neuron |
|
|
Term
|
Definition
| 1. These maintain tonic discharges except saccade in being generated - they stop discharging. 2.They inhibit the burst neurons within the same PPRF 3. Dysfunctional pause cells results in opsoclonus ( |
|
|
Term
|
Definition
| in the nucleus raphe interpositus (RIP) at the rootlets of the abducens nuclei. |
|
|
Term
| Pause Cells discharge continuously (tonic) except |
|
Definition
| iImmediately prior to, during saccades, and blinks. |
|
|
Term
| Pause Cells receive information from |
|
Definition
| higher level centers (FEF/SEF, Sup Coll., and LLBN) that a saccadic response is intended. The role of the pause cells is to tonically inhibit burst cells thereby prevent unwanted saccades during fixation. |
|
|
Term
| Pause Cells help synchronize the activity of |
|
Definition
| the premotor burst neurons. |
|
|
Term
|
Definition
| These act to inhibit the antagonist muscles of the intended eye movement |
|
|
Term
| Inhibitory Burst Cells discharge rates are |
|
Definition
| inversely proportional to those of the EBN |
|
|
Term
|
Definition
| These discharge in relation to eye position which increases proportionately with eccentric gaze position |
|
|
Term
| Long Lead Burst Neurons LLBN |
|
Definition
| are the site for saccade-specific integration of velocity to position signal. They receive excitatory signal from the superior colliculus. |
|
|
Term
|
Definition
| comparing the integral of an efference copy of saccade velocity and the integral of the input from SC. |
|
|
Term
| The two main brainstem targets of the cortical eye fields are the |
|
Definition
| the superior colliculus and the pontine nuclei, especially the NRTP (Nucleus Recticularis Tementipontis |
|
|
Term
| Higher Central Control Consist of |
|
Definition
| 1. Frontal Eye Fields 2. Parietal Lobes 3. Superior Colliculus 4. Cerebellum 5. Basal Ganglia |
|
|
Term
| In higher central control system the Contralateral Goal-directed fixed vector is |
|
Definition
|
|
Term
|
Definition
| contain a neural map of visual space thus provide the initial information on size and direction of intended saccade. Attention and selection. Send spatial localization signal (amplitude and direction) to the superior colliculus. Inhibits abnormal fixation reflexes. |
|
|
Term
| Stimulation at any site on the FEF elicits a saccade of a specific |
|
Definition
|
|
Term
| What is the most important for the generation of vertical and horizontal saccades |
|
Definition
|
|
Term
| Efferent projections from FEF go to |
|
Definition
| 1. The SC via the dorsal pathway 2. The PPRF via the ventral pathway 3. riMLF via a third intermediate pathway |
|
|
Term
| They receive sensory information from |
|
Definition
| POT and determine the occurrence of a future saccade, and computes direction and size of the saccade. |
|
|
Term
| Lesions of the FEF result |
|
Definition
| in increased saccadic latencies, slowed saccades, impaired predictive tracking (decreased frequency and size of movements and defects of saccades made to paired or multiple targets that are presented asynchronously |
|
|
Term
|
Definition
| Sends information related to localizing targets of interest plus computations of saccade amplitude and direction to the superior colliculus. Directs visual attention to objects in the extra personal space. They receive input signals from MST, supplemental eye fields, FEF, striate cortex. They project onto the dorso-lateral prefrontal cortex. |
|
|
Term
|
Definition
| Processes signals related to an intended saccade received from FEF, Parietal Lobes, and caudate nuclei, encodes it for the desired eye position change with respect to the fovea, and transmits it to the brainstem. |
|
|
Term
| The superficial-3 layers of the Superior Colliculus are what time of cells? |
|
Definition
| sensory cells with retinotopic organization and receptive fields. |
|
|
Term
| Cells in the deeper layers of the Superior Colliculus are |
|
Definition
| motor and have efferent projection to brainstem premotor neurons. They help determine direction, speed and accuracy of saccades for targets in the peripheral visual field. |
|
|
Term
|
Definition
| reduces the number of spontaneous saccades |
|
|
Term
|
Definition
| 1. Concerned with Saccadic Gain-Control or adaptive processes. 2. Receives input from brainstem structures involved in saccade generation, 3. Outputs to brainstem and other saccade-related sites to maintain, and/or adapt saccade gain 4. Controls accuracy of saccades, 5. Lesions of the cerebellum flocculus and vermis result in saccadic dysmetria (hypermetria). 6. Defect is ipsilateral in hemi-cerebellectomy 7.Total cerebellectomy produces persistent saccadic dysmetria (especially hypermetria). |
|
|
Term
| What kind of loop that the cerebellum profide? |
|
Definition
| The cerebellum provides a positive feedback loop with a gain of K that improves the the time constant of an inherently leaky brainstem NI |
|
|
Term
| The SNPR and the Caudate nuclei are the |
|
Definition
| nondopaminergic portions of the Basal Ganglia. |
|
|
Term
| SNPR and the Caudate nuclei |
|
Definition
| control saccade-related neuron in the superior colliculus. They selectively gate, reflexive and voluntary saccades generated by the superior colliculus. They facilitate the initiation of more voluntary, self-initiated forms of saccades - tasks involving prediction and memory. Aid steady fixation by preventing unwanted reflexive saccades. |
|
|
Term
|
Definition
| injection into the SNpr has a similar effect to injection of bicuculline (a GABA antagonist) into the superior colliculus. Repetitive, irrespressible saccades occur, which are directed contralaterally to the side of the injection. |
|
|
Term
| Bicucculine (antagonist to GABA). |
|
Definition
| When this injected in the SC. will have repetitive, irrespressible saccades that occur, which are direct contrallateraly to the side of the injection |
|
|
Term
| Lesions in the Posterior Commissure |
|
Definition
| produce abnormalities of upward gaze. |
|
|
Term
| Posterior Commissure may possibly account for |
|
Definition
| Possibly accounts for the dorsal-midbrain syndrome (Parinaud’s Syndrome) characterized by impairment of upwardly directed saccades – to – loss of vertical movements of the eyeball, convergence retraction, pupillary mydriasis, corectopia, light-near-dissociation |
|
|
