COMMENTARY

The Neurobiology of ADHD

Robert D. Hunt, MD

Disclosures

September 25, 2006

In This Article

The Process of Attention

Consider the process of landing an aircraft, which has been studied extensively in terms of altitude variables, flight safety issues,[4] and the layout of instruments on the flight panel.[5] However, it is an interesting example in terms of attention because throughout the process of flying, a pilot's attention is alternatively proactive and responsive. The pilot has to maintain an automatic scan between the instruments that identify his current position in terms of pitch (climbing or descending), roll (turning), and horizontal/lateral (direction) axes. He must also track the gradual descent of altitude. In addition, air traffic control may alter his flight path to accommodate other aircraft in the landing pattern and in response to runway availability and wind direction on the ground. All of these accommodations are also made in a context of weather conditions, in order, for example, to avoid thunderstorms and minimize turbulence. But the pilot must also monitor the plane's internal conditions -- the power settings, manifold pressure, and fuel levels. In flight, the pilot must continuously shift attention to monitor the location and functioning of the plane using the internal flight instruments, and modify it if directions from air traffic control, ambient weather, or other nearby aircraft warrant it. Mastering an automatic scan between the instruments that identify the plane's direction, pitch (up for climb; down for descent), tilt (wings level or rotated), and air speed is an essential component of flight training. Finally, as the runway comes into sight, the pilot shifts his attention towards monitoring the craft visually, in relation to the touchdown markings on the runway.

As a pilot charts the course, he varies altitude, position and speed depending on location and direction from air traffic control. His principle source of information, the object of his attention, shifts from visually monitoring the instruments to auditory interactions with air traffic control. His cognitive set shifts in response to the varying priorities of changes in altitude, fuel consumption, direction, weather, and wind conditions. A sudden jolt or small shift in ongoing sounds may immediately demand a change of attention, either to weather conditions or engine performance. The priority of his attention shifts from internal instruments to external environment, from the cockpit to the runway, from auditory to visual, as he maintains and sustains a 3-dimensional picture of location and situation. Often a pilot has to override his strong tactile (proprioceptive) sensation, such as when the instruments tell him that he is descending to the left and his body feels as if he is climbing to the right. A major risk for an amateur pilot would be to become fixated or stuck on one instrument to the neglect of essential information from other sources. When conditions change, attention must follow.

The interwoven processes of attention can be subgrouped as: (1) the prerequisites for attention, which includes adequate arousal and alertness and the organization of goal-directed purpose or interest; (2) the content of attention, which extends to sensory processing, thoughts or ideas, and memory accessing; (3)the process of attention, which involves both receptive attention and expressive attention. In both directions, attention primarily constitutes enhancing the signal:noise gradient by magnifying sensory information, emotions, or thoughts that are relevant while concurrently inhibiting stimuli that distract or interfere; (4) brain structures involved in attention, including the parts of the brain specifically involved in ADHD, like the striatum and the prefrontal cortex; (5) the modulation of attention, which includes processes that amplify or reduce attention, such as mood.

This process of deconstructing attention always runs the risk of drawing artificial boundaries between the specific cognitive processes essential to sensory or information processing and those components that specifically embody the mechanism of selection and continuity that comprise attention.[5,6,7,8]

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