Final answer:
Attention influences brain evoked responses by increasing energy demands, leading to more blood flow and enhanced mental activity. It can also result in inattentional blindness and affect autonomic responses like the fight-or-flight reaction.
Step-by-step explanation:
Attention significantly affects the brain evoked responses by increasing the energy demands on the brain. This heightened activity can lead to increased blood flow to the brain, providing more glucose and oxygen which is necessary for heightened mental activity. The phenomenon of inattentional blindness, demonstrated by the selective attention test, reveals that when our focus is on a challenging task, we tend to miss other external stimuli. Moreover, attentional allocation can influence the autonomic functions such as the fight-or-flight response, mediated by the amygdala and limbic structures. For example, in a visual task where subjects recognize faces and respond by pressing a button, areas like visual sensory areas, integrating areas, motor areas, and more show increased activity, indicating active engagement of the brain beyond the commonly misunderstood '10% usage' concept.