5 research outputs found
Die Rolle des mediotemporalen Areals im Gehirn der Primaten bei visuell geführten Handbewegungen
No full textDie Bewegungen unserer Gliedmaßen und Augen werden visuell gesteuert. Im Primatenhirn werden visuelle Signale der Retina innerhalb eines hierarchisch und parallel organisiertem Netzwerkes kortikaler Areale verarbeitet. Verschiedene Aspekte des visuellen Bildes werden in verschiedenen kortikalen Pfaden analysiert. Das mittlere temporale Areal (MT) im superioren temporalen sulcus ist bekannt für seine Rolle in der Wahrnehmung visueller Bewegung und der Steuerung der Augen zu bewegten Zielen. Mit 3 unterschiedlichen Methoden habe ich die funktionelle Bedeutung von MT für die visuelle Steuerung von Handbewegungen untersucht. Extrazelluläre Ableitungen zeigten eine Modulation der neuronalen Aktivität abhängig von der Ausführung manueller Folgebewegungen. Inaktivierungen durch Mikroinjektionen von Muscimol sowie Mikrostimulationen betrafen die Latenz und die Richtung der Handbewegungsinitiation. Die Ergebnisse deuten auf MT als eine generelle Quelle von visueller Bewegungsinformation.Most of our movements of the limbs and the eyes are controlled by visual signals. In the primate brain visual signals of the retina are processed within a network of cortical areas which features hierarchical and parallel organisation. Different aspects of the visual scene are analysed along different cortical pathways. The middle temporal area (MT) in the superior temporal sulcus is well known for its role in visual motion perception and the guidance of eye movements to moving targets. By three different methodological approaches I explored the functional significance of MT for the visual control of hand movements in the macaque monkey. Extracellular recordings showed a modulation of neuronal activity depending on the execution of manual tracking movements. Inactivation by microinjections of muscimol as well as microstimulation affected the latency and the direction of hand movement initiation. The results suggest MT to be a general source of visual movement information
Distinct feedforward and feedback pathways for cell-type specific attention effects
No full textSpatial attention increases both inter-areal synchronization and spike rates across the visual hierarchy. To investigate whether these attentional changes reflect distinct or common mechanisms, we performed simultaneous laminar recordings of identified cell classes in macaque V1 and V4. Enhanced V4 spike rates were expressed by both excitatory neurons and fast-spiking interneurons, and were most prominent and arose earliest in time in superficial layers, consistent with a feedback modulation. By contrast, V1-V4 gamma-synchronization reflected feedforward communication and surprisingly engaged only fast-spiking interneurons in the V4 input layer. In mouse visual cortex, we found a similar motif for optogenetically identified inhibitory-interneuron classes. Population decoding analyses further indicate that feedback-related increases in spikes rates encoded attention more reliably than feedforward-related increases in synchronization. These findings reveal distinct, cell-type-specific feedforward and feedback pathways for the attentional modulation of inter-areal synchronization and spike rates, respectively
Contribution of Ionotropic Glutamatergic Receptors to Excitability and Attentional Signals in Macaque Frontal Eye Field
No full textTop-down attention, controlled by frontal cortical areas, is a key component of cognitive operations. How different neurotransmitters and neuromodulators flexibly change the cellular and network interactions with attention demands remains poorly understood. While acetylcholine and dopamine are critically involved, glutamatergic receptors have been proposed to play important roles. To understand their contribution to attentional signals, we investigated how ionotropic glutamatergic receptors in the frontal eye field (FEF) of male macaques contribute to neuronal excitability and attentional control signals in different cell types. Broad-spiking and narrow-spiking cells both required N-methyl-D-aspartic acid and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor activation for normal excitability, thereby affecting ongoing or stimulus-driven activity. However, attentional control signals were not dependent on either glutamatergic receptor type in broad- or narrow-spiking cells. A further subdivision of cell types into different functional types using cluster-analysis based on spike waveforms and spiking characteristics did not change the conclusions. This can be explained by a model where local blockade of specific ionotropic receptors is compensated by cell embedding in large-scale networks. It sets the glutamatergic system apart from the cholinergic system in FEF and demonstrates that a reduction in excitability is not sufficient to induce a reduction in attentional control signals.</p
An Open Resource for Non-human Primate Optogenetics.
No full textOptogenetics has revolutionized neuroscience in small laboratory animals, but its effect on animal models more closely related to humans, such as non-human primates (NHPs), has been mixed. To make evidence-based decisions in primate optogenetics, the scientific community would benefit from a centralized database listing all attempts, successful and unsuccessful, of using optogenetics in the primate brain. We contacted members of the community to ask for their contributions to an open science initiative. As of this writing, 45 laboratories around the world contributed more than 1,000 injection experiments, including precise details regarding their methods and outcomes. Of those entries, more than half had not been published. The resource is free for everyone to consult and contribute to on the Open Science Framework website. Here we review some of the insights from this initial release of the database and discuss methodological considerations to improve the success of optogenetic experiments in NHPs
