Salience, saccades, and the role of cortex

1999 ◽  
Vol 22 (4) ◽  
pp. 698-699
Author(s):  
Kathleen Taylor
Keyword(s):  
Superior Colliculus ◽  
Brain Areas ◽  
Cortical Level ◽  
Target Article ◽  
Walker’S Model ◽  
Subcortical Regions ◽  
Oculomotor Function ◽  
Saccade Generation

Findlay & Walker's target article proposes a model of saccade generation related to the underlying neuroscience. A problem with such models is the number of brain areas showing oculomotor function. Traditionally, therefore, models have been partial, usually concentrating either on cortex (Liu et al. 1997; Pierrot Deseilligny et al. 1995) or on the superior colliculus and brainstem circuits (Moschovakis 1994; Van Gisbergen et al. 1993). Findlay & Walker's model attempts to integrate both levels within a functional framework. To some extent it falls between two stools. For example, some functions that the authors ascribe to subcortical regions may actually occur at the cortical level.

The underrated role of the “move system” in determining saccade latency

1999 ◽  
Vol 22 (4) ◽  
pp. 681-682 ◽  
Author(s):  
Michael C. Dorris ◽  
Douglas P. Munoz
Keyword(s):  
Superior Colliculus ◽  
Target Location ◽  
Saccade Latency ◽  
Gap Effect ◽  
Target Specificity ◽  
Express Saccades ◽  
Latency Reduction ◽  
Extensive Training ◽  
Target Article

The Findlay & Walker target article emphasizes the role of the target-nonspecific “fixate” system while downplaying the role of the target-specific “move” system in determining saccade latency. We agree that disengagement of the fixate system is responsible for the target-nonspecific latency reduction associated with the gap effect. However, high target predictability and extensive training at a target location can also result in latency reductions, the culmination of this being express saccades. The target-specificity associated with the latter forms of latency reduction implicate a mechanism involving the move system. Recently discovered neurophysiological correlates underlying these behavioural phenomena reside in the superior colliculus.

Anatomy and physiology of saccadic long-lead burst neurons recorded in the alert squirrel monkey. II. Pontine neurons

1996 ◽  
Vol 76 (1) ◽  
pp. 353-370 ◽  
Author(s):  
C. A. Scudder ◽  
A. K. Moschovakis ◽  
A. B. Karabelas ◽  
S. M. Highstein
Keyword(s):  
Superior Colliculus ◽  
Brain Stem ◽  
Reticular Formation ◽  
Reticulospinal Neurons ◽  
Burst Neurons ◽  
Nucleus Reticularis ◽  
Discharge Patterns ◽  
The Brain ◽  
Saccade Generation

1. The discharge patterns and axonal projections of saccadic long-lead burst neurons (LLBNs) with somata in the pontine reticular formation were studied in alert squirrel monkeys with the use of the method of intraaxonal recording and horseradish peroxidase injection. 2. The largest population of stained neurons were afferents to the cerebellum. They originated in the dorsomedial nucleus reticularis tegmenti pontis (NRTP) including its dorsal cell group (N = 5), the preabducens intrafascicular nucleus (N = 5), and the raphe pontis (N = 1). Axons of all neurons coursed under NRTP and entered brachium pontis without having synapsed in the brain stem. Three axons sent collaterals to the floccular lobe, but other more distant targets of these and the other cerebellar afferents could not be determined. Movement fields of these neurons were intermediate between vectorial and directional types. 3. Four neurons had their somata in nucleus reticularis pontis oralis and terminations in the brain stem reticular formation. Each neuron was different, but all terminated in the region containing excitatory burst neurons, and most terminated in the region containing inhibitory burst neurons. Other targets include nucleus reticularis pontis oralis and caudalis, NRTP, raphe interpositus, and the spinal cord. Discharge patterns included both vectorial and directional types. 4. Two reticulospinal neurons had large multipolar somata either just rostral or ventral to the abducens nucleus. These neurons also projected to the medullary reticular formation, caudal nucleus prepositus hypoglossi, and dorsal and ventral paramedian reticular nucleus. 5. The functional implications of the connections of these LLBNs and those reported in the companion paper are extensively discussed. The fact that the efferents of the superior colliculus target the regions containing medium-lead saccadic burst neurons confirms the role of the colliculus in saccade generation. However, the finding that many other neurons project to these regions and the finding that superior colliculus efferents project more heavily to areas containing reticulospinal neurons argue for a diminished role of the superior colliculus in saccade generation but an augmented role in head movement control.

scholarly journals Similarity of superior colliculus involvement in microsaccade and saccade generation

2012 ◽  
Vol 107 (7) ◽  
pp. 1904-1916 ◽  
Author(s):  
Ziad M. Hafed ◽  
Richard J. Krauzlis
Keyword(s):  
Eye Movements ◽  
Superior Colliculus ◽  
Firing Rate ◽  
Related Activity ◽  
Movement Onset ◽  
Midbrain Structure ◽  
Fixational Saccades ◽  
Voluntary Saccades ◽  
Saccade Generation

The characteristics of microsaccades, or small fixational saccades, and their influence on visual function have been studied extensively. However, the detailed mechanisms for generating these movements are less understood. We recently found that the superior colliculus (SC), a midbrain structure involved in saccade generation, also plays a role in microsaccade generation. Here we compared the dynamics of neuronal activity in the SC associated with microsaccades to those observed in this structure in association with larger voluntary saccades. We found that microsaccade-related activity in the SC is characterized by a gradual increase in firing rate starting ∼100 ms prior to microsaccade onset, a peak of neuronal discharge just after movement onset, and a subsequent gradual decrease in firing rate until ∼100 ms after movement onset. These properties were shared with saccade-related SC neurons, recorded from the same monkeys but preferring larger eye movements, suggesting that at the level of the SC the neuronal control of microsaccades is similar to that for larger voluntary saccades. We also found that neurons exhibiting microsaccade-related activity often also exhibited saccade-related activity for slightly larger movements of similar direction, suggesting a continuity of the spatial representation in the SC, in both amplitude and direction, down to the smallest movements. Our results indicate that the mechanisms controlling microsaccades may be fundamentally the same as those for larger saccades, and thus shed new light on the functional role of these eye movements and their possible influence on sensory and sensory-motor processes.

Experimental test of two models for the role of monkey superior colliculus in 3D saccade generation

1993 ◽  
pp. 240-254 ◽  
Author(s):  
John Van Opstal ◽  
Klaus Hepp ◽  
Bernhard Hess ◽  
Dominik Straumann ◽  
Volker Henn
Keyword(s):  
Superior Colliculus ◽  
Experimental Test ◽  
Saccade Generation

Choosing a Markov blanket

2020 ◽  
Vol 43 ◽  
Author(s):  
Thomas Parr
Keyword(s):  
Markov Blanket ◽  
Target Article ◽  
The Relationship

Abstract This commentary focuses upon the relationship between two themes in the target article: the ways in which a Markov blanket may be defined and the role of precision and salience in mediating the interactions between what is internal and external to a system. These each rest upon the different perspectives we might take while “choosing” a Markov blanket.

Pulvino-cortical interaction: an integrative role in the control of attention

2019 ◽  
Author(s):  
Alexia Bourgeois ◽  
Carole Guedj ◽  
Emmanuel Carrera ◽  
Patrik Vuilleumier
Keyword(s):  
Executive Control ◽  
Sensory Information ◽  
Relevant Information ◽  
Cortical Circuits ◽  
Attention And Executive Control ◽  
Neural Communication ◽  
Subcortical Regions ◽  
Theoretical Proposal ◽  
Selection Of

Selective attention is a fundamental cognitive function that guides behavior by selecting and prioritizing salient or relevant sensory information of our environment. Despite early evidence and theoretical proposal pointing to an implication of thalamic control in attention, most studies in the past two decades focused on cortical substrates, largely ignoring the contribution of subcortical regions as well as cortico-subcortical interactions. Here, we suggest a key role of the pulvinar in the selection of salient and relevant information via its involvement in priority maps computation. Prioritization may be achieved through a pulvinar- mediated generation of alpha oscillations, which may then modulate neuronal gain in thalamo-cortical circuits. Such mechanism might orchestrate the synchrony of cortico-cortical interaction, by rendering neural communication more effective, precise and selective. We propose that this theoretical framework will support a timely shift from the prevailing cortico- centric view of cognition to a more integrative perspective of thalamic contributions to attention and executive control processes.

scholarly journals Stoichiometric Analysis of Shifting in Subcellular Compartmentalization of HSP70 within Ischemic Penumbra

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3578
Author(s):  
Federica Mastroiacovo ◽  
Francesca Biagioni ◽  
Paola Lenzi ◽  
Larisa Ryskalin ◽  
Stefano Puglisi-Allegra ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Neuronal Survival ◽  
Hsp 70 ◽  
Preclinical Models ◽  
Brain Areas ◽  
Cell Compartments ◽  
Control Brain ◽  
Disease Modifier ◽  
Subcellular Compartmentalization

The heat shock protein (HSP) 70 is considered the main hallmark in preclinical studies to stain the peri-infarct region defined area penumbra in preclinical models of brain ischemia. This protein is also considered as a potential disease modifier, which may improve the outcome of ischemic damage. In fact, the molecule HSP70 acts as a chaperonine being able to impact at several level the homeostasis of neurons. Despite being used routinely to stain area penumbra in light microscopy, the subcellular placement of this protein within area penumbra neurons, to our knowledge, remains undefined. This is key mostly when considering studies aimed at deciphering the functional role of this protein as a determinant of neuronal survival. The general subcellular placement of HSP70 was grossly reported in studies using confocal microscopy, although no direct visualization of this molecule at electron microscopy was carried out. The present study aims to provide a direct evidence of HSP70 within various subcellular compartments. In detail, by using ultrastructural morphometry to quantify HSP70 stoichiometrically detected by immuno-gold within specific organelles we could compare the compartmentalization of the molecule within area penumbra compared with control brain areas. The study indicates that two cell compartments in control conditions own a high density of HSP70, cytosolic vacuoles and mitochondria. In these organelles, HSP70 is present in amount exceeding several-fold the presence in the cytosol. Remarkably, within area penumbra a loss of such a specific polarization is documented. This leads to the depletion of HSP70 from mitochondria and mostly cell vacuoles. Such an effect is expected to lead to significant variations in the ability of HSP70 to exert its physiological roles. The present findings, beyond defining the neuronal compartmentalization of HSP70 within area penumbra may lead to a better comprehension of its beneficial/detrimental role in promoting neuronal survival.

scholarly journals Effects of Transcranial Ultrasound Stimulation on Trigeminal Blink Reflex Excitability

2021 ◽  
Vol 11 (5) ◽  
pp. 645
Author(s):  
Andrea Guerra ◽  
Edoardo Vicenzini ◽  
Ettore Cioffi ◽  
Donato Colella ◽  
Antonio Cannavacciuolo ◽  
...  
Keyword(s):  
Substantia Nigra ◽  
Superior Colliculus ◽  
Blink Reflex ◽  
Transcranial Ultrasound ◽  
Recovery Cycle ◽  
Brain Areas ◽  
Nucleus Raphe Magnus ◽  
Ultrasound Stimulation ◽  
Raphe Magnus ◽  
Interstimulus Intervals

Recent evidence indicates that transcranial ultrasound stimulation (TUS) modulates sensorimotor cortex excitability. However, no study has assessed possible TUS effects on the excitability of deeper brain areas, such as the brainstem. In this study, we investigated whether TUS delivered on the substantia nigra, superior colliculus, and nucleus raphe magnus modulates the excitability of trigeminal blink reflex, a reliable neurophysiological technique to assess brainstem functions in humans. The recovery cycle of the trigeminal blink reflex (interstimulus intervals of 250 and 500 ms) was tested before (T0), and 3 (T1) and 30 min (T2) after TUS. The effects of substantia nigra-TUS, superior colliculus-TUS, nucleus raphe magnus-TUS and sham-TUS were assessed in separate and randomized sessions. In the superior colliculus-TUS session, the conditioned R2 area increased at T1 compared with T0, while T2 and T0 values did not differ. Results were independent of the interstimulus intervals tested and were not related to trigeminal blink reflex baseline (T0) excitability. Conversely, the conditioned R2 area was comparable at T0, T1, and T2 in the nucleus raphe magnus-TUS and substantia nigra-TUS sessions. Our findings demonstrate that the excitability of brainstem circuits, as evaluated by testing the recovery cycle of the trigeminal blink reflex, can be increased by TUS. This result may reflect the modulation of inhibitory interneurons within the superior colliculus.

Sleep and memory: Definitions, terminology, models, and predictions?

2005 ◽  
Vol 28 (1) ◽  
pp. 71-72
Author(s):  
Jonathan K. Foster ◽  
Andrew C. Wilson
Keyword(s):  
Relevant Literature ◽  
Procedural Memory ◽  
Current State ◽  
Target Article ◽  
Walker’S Model

In this target article, Walker seeks to clarify the current state of knowledge regarding sleep and memory. Walker's review represents an impressively heuristic attempt to synthesize the relevant literature. In this commentary, we question the focus on procedural memory and the use of the term “consolidation,” and we consider the extent to which empirically testable predictions can be derived from Walker's model.

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