The ability to focus is not governed by a single, centralized part of the brain but is an emergent property of multiple, large-scale neural networks working in concert. Attention is defined as the cognitive process of selectively concentrating on a discrete stimulus while simultaneously filtering out irrelevant information. This complex mental process requires continuous, coordinated signaling across various brain regions to manage alertness, orienting, and self-control.
The Tripartite Neural Network Governing Attention
The brain organizes its attentional capabilities into three distinct, yet interacting, neural systems. The Alerting network is responsible for achieving and maintaining a state of readiness to respond to incoming stimuli. This system is primarily associated with the brainstem, specifically the locus coeruleus, and sets the general level of arousal and vigilance.
The Orienting network is dedicated to selecting and prioritizing sensory information. This network is divided into two pathways: the dorsal and ventral attention networks. The Dorsal Attention Network (DAN) manages top-down, goal-directed attention, acting when a person intentionally chooses to focus on a particular location or object. Its core structures are the frontal eye fields and the superior parietal lobule, which work bilaterally to direct focus according to current behavioral goals.
The Ventral Attention Network (VAN), conversely, handles bottom-up attention, acting as a “circuit breaker” to reorient focus toward unexpected or highly salient external stimuli. This system is predominantly right-lateralized and involves the temporoparietal junction (TPJ) and the inferior frontal gyrus. When an unforeseen event, like a sudden loud noise, occurs, the VAN interrupts the DAN’s current activity to shift attention to the new, potentially significant, stimulus.
The Executive Control network performs the highest level of attentional management by resolving conflicts and making decisions about what to focus on. Anatomically, this network relies heavily on the prefrontal cortex and the anterior cingulate cortex (ACC). Its function is to manage and maintain cognitive control, allowing a person to suppress automatic responses in favor of deliberate, goal-oriented behavior. These three networks continuously interact to determine where, when, and how attention is deployed.
Functional Categories of Attention
These underlying neural networks manifest in observable cognitive functions. Selective Attention involves the ability to focus on a single object or task while actively filtering out distracting information. This function is closely linked to the Executive Control network, as it requires the suppression of irrelevant sensory input from both the environment and internal thoughts.
Sustained Attention, often referred to as vigilance, is the capacity to maintain focus on a continuous activity over a prolonged period. This ability relies heavily on the Alerting network to maintain a steady state of arousal, preventing the brain from drifting into its default resting state.
Divided Attention describes the ability to engage in two or more tasks simultaneously, such as driving while holding a conversation. While often perceived as true multitasking, this ability is frequently accomplished by rapidly shifting the focus of the Executive Control network between the different tasks. This rapid, flexible switching of focus allows the brain to manage multiple streams of information.
The Role of Neurotransmitters in Attentional Focus
The functional state of the attentional networks is dynamically regulated by several chemical messengers, known as neurotransmitters. Dopamine is particularly important for the Executive Control network, playing a significant role in motivation, reward processing, and the sustained maintenance of focus, especially in the prefrontal cortex. This neurotransmitter helps the brain determine the value of a stimulus, thereby influencing which goals are prioritized for attention.
Norepinephrine, produced by the brainstem’s locus coeruleus, is directly tied to the Alerting network. It modulates the overall level of alertness and arousal, enabling a rapid response to unexpected or salient stimuli. By broadcasting its signal widely, norepinephrine primes the cerebral cortex for faster and more efficient information processing.
Acetylcholine plays a distinct role in cognitive flexibility, which includes the ability to shift attention and maintain a steady focus during demanding tasks. This neurotransmitter is relevant for the general speed of information processing, acting to refine and sustain the brain’s engagement with a task. The coordinated release of these neurotransmitters allows the brain to transition smoothly between states of high arousal, directed focus, and cognitive flexibility.
Conditions Related to Attention System Dysregulation
When the interconnected attention systems do not function correctly, specific neurological conditions can arise. Attention Deficit Hyperactivity Disorder (ADHD) is understood to be a primary example of dysregulation within the Executive Control network and its associated pathways. The condition is linked to structural and functional differences in the prefrontal cortex, which impairs the ability to plan, inhibit impulses, and sustain attention.
The neurochemical basis of ADHD involves a dysfunction in the dopamine and norepinephrine signaling systems, often referred to as the catecholamine hypothesis. This dysregulation can lead to difficulties in maintaining the necessary level of focus for non-rewarding tasks and problems with self-regulation.
Spatial Neglect demonstrates a failure of the Orienting network, particularly the right-lateralized Ventral Attention Network. Patients with this condition, typically after a stroke damaging the right parietal lobe, fail to notice, respond to, or orient toward stimuli on the side of space opposite the brain injury. Crucially, this is a disorder of attention, not a sensory or vision problem, as the brain’s mechanism for awareness and orientation toward that side of space is compromised.