The everyday expression "I cannot concentrate" could mean that relevant information is not being selected, a goal is not being sustained, a thought is intruding, the task is aversive, or a return after interruption is difficult. It is not one scientific outcome measure.
Posner's attention network theory, proposed by cognitive psychologist Michael Posner and Steven Petersen in 1990, states that human attention is not a single, general ability. Instead, it is managed by three distinct, anatomically and functionally separate neural networks: Alerting, Orienting, and Executive Control.
1 · The Alerting Network
- Function: achieves and maintains a state of high readiness, arousal, and sustained vigilance to process incoming stimuli. It handles rapid changes caused by warning or alert signals.
- Brain regions: right hemisphere structures, the brainstem arousal systems, and the locus coeruleus (which supplies norepinephrine).
- Primary neurotransmitter: norepinephrine.
2 · The Orienting Network
- Function: selects and prioritizes specific sensory information from the environment, either overtly by moving the eyes or head, or covertly by shifting mental focus without moving the body.
- Brain regions: posterior parietal cortex, superior colliculus, pulvinar nucleus of the thalamus, and frontal eye fields.
- Primary neurotransmitter: acetylcholine.
3 · The Executive Control Network
- Function: resolves conflicts between thoughts, feelings, or competing responses, monitors errors, and regulates goal-directed behavior.
- Brain regions: anterior cingulate cortex (ACC) and lateral prefrontal cortex.
- Primary neurotransmitter: dopamine.