Brain oscillations and sustained attention

It has been mentioned that we rely on sustained attention to protect task performance against fatigue and distraction (Clayton et al, 2015) with the time-related variations in attention correlating with changes in specific cortical oscillations (Langner and Eickhof, 2013) The capacity to sustain one’s attention is of great practical Importance (Clayton et al, 2015) with sustained attention relying on interactions between oscillations across attention-related brain networks (Sarter et al, 2001) Studies using Neuroimaging research have suggested that sustained attention tasks elicit activations in a distributed network of brain areas (Langner and Eickhof, 2013). It has also been suggested by Langer and Eickhof (2013) that cognitive theories are being used to generate proposals about the regions to the constituent to the process of sustained attention. According to Johnson et al (2011), cognitive theories about time-related variations in attention are related to the amplitude of cortical oscillations. Sustained attention is defined by Roberton and Garavan (2004) as the self-directed maintenance of cognitive focus under non-arousing conditions. Roberton and Garavan (2004) stated that sustained attention is commonly studied with a task that requires unpredictable signals over an extended period with measures in fluctuations and deteriorations within the task being carried out (Mcdonald et al, 2009). Roberton and Garavan (2004) contributed and mentioned that differences in measures of performance have been suggested to reflect dissociable cognitive processes. This said it has been mentioned that it remains unclear whether fluctuations and deteriorations in attention reflect dissociable neural processes (Esterman et al, 2014). Cognitive control has proposed that sustained attention involves the activation of the anterior and posterior attention systems (Sarter et al, 2001) with the prefrontal regions of the brain stimulating prolonged control over processing through relays in the parietal cortex (Esterman et al,2013). However, research by Suss et al (1995) highlights that the frontoparietal systems do not support sustained attention by performing unitary operations it engages in multiple cognitive functions simultaneously This has been supported by Langner and Eickhof (2013) who state that during sustained task brain activation is distributed across numerous functionally separable brain networks. This network according to Suss et al (1995) is dependent t upon the following cognitive functions (i) monitoring and evaluation of ongoing cognitive processes, (ii) energisation of task-relevant processes, and (iii) inhibition of task-irrelevant processes. This neurocognitive theory (Anderson and Ding, 2011) suggests sustained attention depends on continuous activation of task-relevant activity (Bollimunta et al, 2008) and involves the posterior medial frontal cortex which includes the dorsomedial prefrontal and anterior cingulate cortex (Reinhart, 2011). The posterior medial frontal cortex has been suggested by (Oehrn et al (2014) to trigger adaptive modification of ongoing processing by communicating with the lateral prefrontal cortex which in turn transmits excitatory and inhibitory signals to lower-level sensorimotor areas. This is said to monitor ongoing mental processing and in turn signals the need for increased attentional control through the detection of inadequate cognitive focus (Elton. and Gao, 2014) and the adjustments of attention are strongly associated with the synchronisation of activity within the so-called executive control network (Seeley, 2007). In accordance, it has been mentioned that for these prefrontal activities to modulate sensorimotor processing, they must then be communicated to posterior brain areas (Anderson and Ding, 2011) and be facilitated by long-range, low-frequency (< 14 Hz) phase synchronisation (Wen et al, 2013). According to Cohen and van Gaal, (2013) this increased low-frequency phase synchronisation between frontal and posterior areas is commonly observed during the orientation of attention and is a predictor of the improvements in attention following momentary attentional lapse. Along with the posterior medial frontal cortex and the lateral prefrontal cortex, Dosenbach et al (2007) suggested that control of task-related processing is associated with synchronised activation in the cingulo-opercular network which includes the anterior cingulate cortex and anterior insulae and whose networks are continuously active during extended cognitive engagements as well as contributing to the and regulate activity in the default-mode network during visual attention tasks. These networks have been suggested to have strong associations between haemodynamic activity in specific brain regions and the core functions of sustained attention (Hinds, 2013). In addition to the front medial theta power, the excitation-inhibition homeostasis in the cortex has been linked with both attentional fatigue and enhanced attention task performance (Lal and Craig, 2001). In conjunction with the theta power, the alpha power reflects reduced attention when localised to posterior regions but has been suggested to improve attention when averaged across the scalp (Makeig and Jung, 1995) and has been found to decrease with cognitive fatigue and increase during periods of participant-assessed ‘on-task’ performance (Liu et al, 2010). Hom et al (2009) relate both theta and alpha power when suggesting that the deteriorations in attention are strongly associated with specific changes in oscillatory features (e.g., the ratio of theta to alpha power (Holm et al, 2009) it has been suggested by Lal and Craig, (2001) that its plays a positive role in attentional control. Sustained attention depends on the continuous activation of task-relevant activity (Reinhart et al,2011) as initiated by that and alpha waves, in relationship with these two oscillations there is the generation of localised gamma oscillations in task-relevant cortical areas (Bollimunta et al, 2008) which have been linked with enhanced attention to sensory inputs (Akimoto et al, 2013). There is a suggestion by Anderson, and Ding (2011) that localised gamma oscillations seem to promote the activation of task-relevant processes across the brain and are strongly modulated by the phase of low-frequency oscillations, initiated by the theta waves, reflecting a coupling for sustained attentional control. In conclusion, sustained attention relies on 1) cognitive monitoring/control functions mediated by theta oscillations, 2) communication across brain networks through low-frequency phase synchronisation, 3) gamma-mediated excitation of task-relevant cortical areas, and 4) alpha-mediated inhibition of task-irrelevant cortical areas (Akimoto et al, 2013). Bollimunta et al (2008) mentioned that these localised oscillations interact with one another across attention-related brain networks, as evidenced by gamma-theta power-phase coupling and anti-correlations between theta and alpha power in task-relevant sensory areas within sustained attention tasks.