ABSTRACT
The state of activation of the brain is closely related to the processes of attention and awareness. Activation circuits with diffuse projections to the cortex provided the neural substrate responsible for graded changes in excitability of cortical neurons and the state of consciousness. The information processing revolution in neurobiology, with its stronger emphasis on specific computational processes in the brain, has also transformed activation theories. Modulation is achieved by selectively enhancing activity in the cortical circuits regulating the information flow in the perceptual and action systems of the brain. The concept of mental effort became affiliated with the theory that activity of the brain depended on a ‘reservoir’ of limited resources allocated to cognitively demanding tasks. Attentional neglect implies that patients fail to attend to stimuli opposite to the side of the lesion in the brain. This confirms the importance of spatial selection mechanisms to direct attention to positions in the outside world.
