5 research outputs found
Sensory memory for odors is encoded in spontaneous correlated activity between olfactory glomeruli
Sensory memory is a short-lived persistence of a sensory stimulus in the nervous system, such as iconic memory in the visual system. However, little is known about the mechanisms underlying olfactory sensory memory. We have therefore analyzed the effect of odor stimuli on the first odor-processing network in the honeybee brain, the antennal lobe, which corresponds to the vertebrate olfactory bulb. We stained output neurons with a calcium-sensitive dye and measured across-glomerular patterns of spontaneous activity before and after a stimulus. Such a single-odor presentation changed the relative timing of spontaneous activity across glomeruli in accordance with Hebb's theory of learning. Moreover, during the first few minutes after odor presentation, correlations between the spontaneous activity fluctuations suffice to reconstruct the stimulus. As spontaneous activity is ubiquitous in the brain, modifiable fluctuations could provide an ideal substrate for Hebbian reverberations and sensory memory in other neural systems
Investigations of changes of the neuronal representation of odors caused by associative and non associative learning in the antennal lobe of the honey bee, Apis mellifera
1\. Titelblatt und Inhaltsverzeichnis 2\. Einleitung 3\. Material und
Methoden 4\. Ergebnisse 5\. Diskussion 6\. LiteraturIn dieser Arbeit wurde mit Hilfe eines kalziumsensitiven Farbstoffes (FURA) an
Bienen die AktivitÀt der Ausgangsneurone des Antennallobus, den
Projektionsneuronen, in drei verschiedenen Versuchssituationen gemessen. Im
Sensitisierungsexperiment wurde untersucht, wie ein mögliches neuronales
Korrelat fĂŒr die im Verhalten gefundenen Reaktionen aussehen könnte. Es konnte
gezeigt werden, dass sensitisierte Bienen bis zu 6,5 Minuten eine höhere
duftinduzierte Kalziumkonzentration in Projektionsneuronen des wichtigsten
Glomerulus fĂŒr ein Duftmuster aufweisen als nicht sensitisierte Tiere. Die
Ergebnisse lassen vermuten, dass zumindest fĂŒr den ersten Messpunkt 30
Sekunden nach der Sensitisierung die erhöhte Kalziumkonzentration in den
Projektionsneuronen eine Verhaltensreaktion (PER) nach sich zieht. Im zweiten
Experiment wurde untersucht, ob und wie eine DuftprÀsentation die stetig
vorhandenen spontanen Kalziumfluktuationen in den Projektionsneuronen
verÀndert. Die SpontanaktivitÀtsexperimente zeigten, dass eine Duftstimulation
die Korrelation zwischen Glomeruli im Mittel senkt. Die Korrelation zwischen
Duftglomeruli steigt jedoch. Dieses Ergebnis lĂ€sst darauf schlieĂen, dass
Spuren des Duftes nach dessen Wahrnehmung im Netzwerk "AL" in Form einer
erhöhten Korrelation zwischen Duftglomeruli vorhanden sind. Die
Verhaltensexperimente wurden durchgefĂŒhrt, um zu untersuchen, wie
VerÀnderungen im Verhalten neuronal reprÀsentiert sind. Es konnte gezeigt
werden, dass die duftinduzierte Erhöhung der Kalziumkonzentration in den
Projektionsneuronen 5 Minuten nach einer differentiellen Konditionierung fĂŒr
den CS+ und die KontrolldĂŒfte verstĂ€rkt ist, nicht aber fĂŒr den CS-. Bei
Tieren, die 15 Minuten nach dem Training getestet wurden, wurde dieser Effekt
nicht gefunden. Es kann somit vermutet werden, dass fĂŒr eine
Verhaltensreaktion eine erhöhte duftinduzierte Kalziumkonzentration in den
Projektionsneuronen nur 5 Minuten nach dem Training nötig ist.In this work the activity of the output neurons of the antennal lobe
(projection neurons) of the honeybee was measured under three different
conditions, using a calcium-sensitive dye (FURA). The first experiment
investigated a possible neuronal correlate for behaviour following
sensitization. It appeared that up to 6.5 minutes after sensitization
sensitized bees showed a higher odor-evoked calcium concentration in
projection neurons of the most sensitive glomerulus of a given odor pattern
than non-sensitized bees. The results suggest that at least for the first
measuring point after sensitization (30s) an increased calcium concentration
in the projection neurons is required for a behaviour response (PER). The
second experiment tested whether and how an odor presentation changes ongoing
spontaneous calcium fluctuations in the projection neurons. It was shown that
mean correlation between glomeruli decreases after odor presentation.
Correlation increases between those glomeruli that are most sensitive to a
given odor. The results presume that after being perceived the odor leaves
traces in the network "AL" in form of an increased correlation between
glomeruli most sensitive to this odor. The last experiments were done to
investigate how changes in behavior are represented neuronaly. It could be
shown that 5 minutes after a differential conditioning the calcium
concentration in the projection neurons is increased for the CS+ and the
control odors, but not for the CS-. Animals tested 15 minutes after
differential conditioning did not show this effect. Therefore it can be
presumed that an increased odor-induced calcium concentration in the
projection neurons is necessary for a behavior response only 5 minutes after
training
Sensory Memory for Odors Is Encoded in Spontaneous Correlated Activity Between Olfactory Glomeruli
Sensory Memory for Odors is Encoded in Spontaneous Correlated Activity between
Sensory memory is a short-lived persistence of a sensory stimulus in the nervous system, such as iconic memory in the visual system. However, little is known about the mechanisms underlying olfactory sensory memory. We have therefore analyzed the effect of odor stimuli on the first odor-processing network in the honeybee brain, the antennal lobe, which corresponds to the vertebrate olfactory bulb. We stained output neurons with a calcium sensitive dye, and measured across-glomerular patterns of spontaneous activity before and after a stimulus. Such a single odor presentation changed the relative timing of spontaneous activity across glomeruli in accordance with Hebbâs theory of learning. Moreover, during the first few minutes after odor presentation, correlations between the spontaneous activity fluctuations suffice to reconstruct the stimulus. As spontaneous activity is ubiquitous in the brain, modifiable fluctuations could provide an ideal substrate for Hebbian reverberations and sensory memory in other neural systems