Zusammenfassung
Einleitung: Die Aufmerksamkeit gilt als selektiver Aspekt der Wahrnehmung. Diese Selektion repräsentiert
eine Auswahl, die meist - aber nicht immer - begrenzt wird von der Art der eintreffenden
Information, der initialen Motivation und der angestrebten Ziele. Unter den verschiedenen
möglichen Differenzierungen dieses Konzeptes hat die Unterscheidung von automatischen
und kontrollierten Prozessen, die eng mit serieller und paralleler Verarbeitungen
verbunden sind, eine besondere Bedeutung. Neurophysiologie: Die selektive Aufmerksamkeit für einen bestimmten Reiz beinhaltet, dass ein Teil
der Information weitergeleitet wird zur Verarbeitung. Diese Weiterleitung erfordert
ein synchronisiertes Feuern der relevanten neuronalen Bahnen, das durch ein EEG ermittelt
werden kann. Bildet man die durch einen Stimulus ausgelösten EEG-Durchschnittswerte
(Ereigniskorrelierte Potentiale), dann sind Erregungs- und Hemmungskomponenten zu
erkennen, die sich den verschiedenen Prozessstadien vom Erkennen eines Signales über
die Hemmung interferierender Prozesse bis zur Kategorisierung des Reizes zuordnen
lassen. Bei der Abweichung von Stimuli werden negative Potentiale (Erregung) abgeleitet
(automatische Prozesse) und die zugehörigen Verarbeitungsspuren (kontrollierte Prozesse)
dargestellt. Gamma-, Beta- und Thetawellen im EEG reflektieren differenziert eine
„binding of stimulus features” in nähere und entferntere Hirnbereiche. Neurotransmitterfunktion: Die chemische Kodierung in dem neuronalen System erfolgt mit den biogenen aminen
Transmittern. Dies erlaubt eine Betrachtung der einzelnen Verarbeitungsschritte, die
zur Einordnung der Reize erforderlich sind. Die Kontrolle der Reizstärke erfolgt mit
Serotonin, Noradrenalin steuert die Einstellung und Dopamin ist zuständig für die
Umschaltung der Aufmerksamkeit. Die Acetylcholin-Aktivität scheint bei salienten Reizeigenschaften
eine automatische Verarbeitung zu fördern. Anatomie der Aufmerksamkeit: Funktionelle Kernspin-Resonanz-Bildgebungsverfahren von Hirnarealen, die bei Aufmerksamkeitsprozessen
aktiviert werden, zeigen, dass es „Epizentren” von Aufmerksamkeits-Funktionen gibt,
die variablen diffus verteilten Aktivitätsmustern übergeordnet sind. Die Frontalregionen
üben eine exekutive Kontrolle aus, werden jedoch in Konfliktfällen der Informationsverarbeitung
und bei Fehlermeldungen durch cinguläre Aktivitäten unterstützt. Teile der Parietallappen
links und rechts registrieren zeitliche und räumliche Aspekte von Ereignissen, deren
Relevanz durch Mustervergleiche im Temporallappen bestimmt werden. Die Auswahl der
für eine adäquate Reaktion erforderlichen Informationen - selektive Aufmerksamkeit
- erfordert daher ein Netzwerk koordinierter Reaktionen unterschiedlicher Hirnareale,
die auf elementare Steuerungsmechanismen des Hirnstammes zur Klassifizierung von Informationen
aufbaut.
Introduction: Attention is viewed as the selective aspect of perception. This selective process
is represented as a choice, often but not always constrained by the initial possibilities,
motivation and adaptive aims. Fundamental among numerous useful divisions of the concept,
is the differentiation of automatic and controlled attention that largely incur serial
and parallel processing of information. Neurophysiology: Selective attention to a stimulus implies that some information is passed on for
further processing - this passage depends on the synchronous firing of the relevant
neuronal pathways. The EEG sums these and a look at the average after an event shows
excitatory and inhibitory components (event-related potentials, ERPs) that relate
to the processing stages from registration, inhibiting interference from other processes
and stimulus categorisation. Negativities (excitation) can be recorded for deviant
detection (automatic) and attended traces (controlled processing). Gamma, beta and
theta frequency bands in the EEG reflect differentially the binding of related features
in nearer and further regions of function. Neurotransmitter Roles: The chemical coding of these neural systems with the biogenic amine transmitters
allows for a division of labour in the mechanisms necessary for „sorting” information.
These are described in terms of volume control (serotonin), tuning (noradrenaline)
and switching (dopamine). The effect of acetylcholine seems to reflect a mechanism
by which a stimulus by means of its salience captures automatic processing. An Anatomy of Attention: Functional magnetic imaging of brain regions activated during attentional processing
show that there are „epicentres” of attentional function superimposed on variable
diffusely distributed activity patterns. Frontal regions exert an executive role,
facilitated by cingulate activitiy in conflict and error-control. Parietal loci on
the left and right register temporal and spatial identification of events whose relevance
can be assessed by comparator mechanisms in the temporal lobe. Choices of what is
relevant - selective attention - for the adaptive organisation of response thus reflect
a concerted effort within a network of heteromodal cortices based on the basic mechanisms
for sorting information arising out of the brainstem.
Schlüsselwörter
Aufmerksamkeit - Ereignis-korrelierte Potentiale - Frontallappen - Parietallappen
- Temporallapen
Key words
Attention - Event-related potentials - Monoamines - Frontal cortex - Parietal cortex
- Temporal cortex
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1 MMN bei hyperaktiven Kindern zeigt eine mangelhafte Entwicklung an der rechten Seite
[6].
Robert D. Oades
Virchowstr. 174
45147 Essen
Email: oades@uni-essen.de