Directed attention fatigue

Directed attention fatigue (DAF) is a neurological phenomenon that results from overuse of the brain’s inhibitory attention mechanisms, which handle incoming distractions while maintaining focus on a specific task. The greatest threat to a given focus of attention is competition from other stimuli that can cause a shift in focus. This is because one maintains focus on a particular thought by inhibiting all potential distractions and not by strengthening that central mental activity. Directed attention fatigue occurs when a particular part of the brain’s global inhibitory system is overworked due to the suppression of increasing numbers of stimuli. This temporary condition is not a clinical illness or a personality disorder. It is rather a temporary fatigue of the inhibitory mechanisms in the brain. According to inhibition theory, it is natural for one to alternate between periods of attention and distraction. Although one’s efforts may involve very different tasks, each incoming stimulus calls upon the same directed attention mechanism.

The concept of stress is used in many situations that would be described as mental fatigue, but the two concepts are distinctly different. Stress involves preparation for an anticipated event that has been evaluated as being threatening or harmful. Though mental fatigue may well result from stressful circumstances, it also arises out of hard work on a project one enjoys. In such cases, there is no anticipation of threat of harm present but still the result is fatigue. Characteristic of mental fatigue is difficulty focusing. For a mentally fatigued person, paying attention to something uninteresting is burdensome, even though focusing on something of great interest poses no particular challenge. Hence, there are two types of attention, distinguished in terms of the effort involved in their use and their changes in attentional shift:

Directed attention, or voluntary attention, requires a great deal of concentration and focus, and is employed in tasks such as problem solving. This type of attention employs the inhibitory mechanisms of the brain, which help block incoming stimuli that are unrelated to the task at hand. Several parts of the brain are involved in maintaining directed attention, primarily those located in the frontal lobe and the parietal lobe of the brain. Specifically, the mechanism of directed attention employs the prefrontal cortex (PFC), the anterior cingulate cortex (ACC) and the brain stem’s basal ganglia. Some fMRI studies have shown that directed attention involves changes in the anterior cingulate cortex and the lateral prefrontal cortex, perhaps as a consequence of increased connectivity between these two areas. Evidence also suggests that the right inferior frontal cortex (IFC) plays a specialized role in response inhibition. It seems that this region plays a key role in the integration of bottom-up response-related information and facilitates goal-directed behavior. While these areas of the brain are known to be involved in DAF, their specific molecular mechanisms in the perpetuation of DAF symptoms are not yet known.

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