The brain accomplishes attentional selection through interacting networks of regions. The task-positive network (TPN), especially the dorsolateral prefrontal cortex and posterior parietal cortex, governs top-down, goal-directed attention by maintaining task goals and biasing perception toward relevant inputs. Counterbalancing this is the default mode network (DMN), including medial prefrontal cortex and posterior cingulate cortex, which is most active during rest, mind-wandering, and self-referential thought. The TPN and DMN tend to be anticorrelated during demanding tasks: when the TPN is engaged in focused work, DMN activity typically subsides, and DMN re-engagement often shows up subjectively as mind-wandering during study, though the two networks are not a strict on/off switch and DMN engagement during breaks supports consolidation and insight.
A set of additional regions supports and modulates these networks. The prefrontal cortex acts as the brain's executive control center for voluntary attention, inhibiting distractions, maintaining goal representations, and orchestrating deep study via top-down control over posterior sensory areas. The posterior parietal cortex acts as a spatial spotlight, directing orienting toward relevant stimuli and disengaging from irrelevant ones. The thalamus, particularly the reticular nucleus and pulvinar, functions as a filter and routing station that regulates which sensory signals gain access to the cortex. The basal ganglia help select and initiate goal-directed actions while suppressing competing routines, contributing both to deliberate attention and to habit formation. The superior colliculus in the midbrain handles fast, stimulus-driven shifts of gaze and attention, often before slower cortical processing takes over, and the locus coeruleus, a small brainstem nucleus, releases norepinephrine across the cortex to modulate arousal and vigilance.
Neurotransmitters shape how effectively these regions can do their work. Acetylcholine sharpens attention by boosting the signal-to-noise ratio in sensory cortex, amplifying behaviorally relevant inputs while suppressing background noise, and also enhances the encoding of new information. Dopamine, particularly from the ventral tegmental area and substantia nigra, signals reward prediction errors and motivates goal-directed behavior, sharpening attention toward reward-predicting cues and fueling curiosity and novelty-seeking. Optimal levels of norepinephrine sharpen focus, while too much produces distractibility and anxiety.
Stress hormones and growth factors also influence attention and learning. Cortisol, the primary stress hormone, follows an inverted-U relationship with cognition: moderate levels support focus and memory formation, while chronic or acute high levels impair prefrontal function and disrupt hippocampal memory consolidation. Brain-derived neurotrophic factor (BDNF), a protein that supports neuron survival and synaptic plasticity, is acutely elevated by aerobic exercise and is associated with improved learning, memory consolidation, and mood over time. Together these neuromodulatory systems set the global arousal and motivational tone within which the TPN and DMN operate, and Michael Posner's attention network theory usefully groups them into three functional networks that can be trained independently: alerting (sustained vigilance), orienting (shifting attention to sensory cues), and executive control (resolving conflict and managing goals).