Attention subcortical

The basal ganglia are a group of subcortical nuclei which are components of modular circuits involved in many cortical functions. They have received considerable attention from basic scientists and clinicians alike because of their prominent involvement in movement disorders, a spectrum of diseases including disorders which are characterized by poverty of movement (hypokinetic disorders), as well as disorders characterized by excess movement (hyperkinetic disorders). It has become clear in recent years that most basal ganglia disorders are not restricted to motor disturbances, but involve cognitive and emotional features as well. 

Frontal and subcortical lacunar infarcts typically affect attention, language, visuospatial function, and motor programming (Babikian et al. 1990). Compared to patients with Alzheimer s disease, those with vascular dementia show better orientation, recall, and language ability. On... 

Amongst other subcortical structures, neurons of the superior colliculus are involved in saccadic eye movements and attentional processes (Wurtz et al., 1982). Local deactivation of the superior colliculus decreases attentional task performance only in the presence of distractors. Again there appears to be a critical interaction between attention and arousal, with a specific attentional role for this particular locus remaining unclear. 

Figure la. Ascending activation from subcortical nuclei (see Fig. 2a) generates a stable platform of consciousness, essential for normal cognitive functions such as selective attention, learning and memory, and higher executive functions (Walker Ballard, 1998). 

The deficit of cortico-striatal innervation that is presumably responsible for reported losses of striatal glutamate uptake sites (Aparicio-Legarza et al., 1997 Simpson et al., 1992), is likely to contribute to the cognitive dysfunction of schizophrenia. These have been described as having similarities to the subcortical dementia (Pantelis et al., 1992) seen in a variety of neurodegenerative disorders disturbances of corticostriatal function are thought to underlie this pattern of cognitive deficits that include disturbances of attention, executive function and short-term memory. 

The role of these subcortical structures in the regulation of attention is less clear. The cerebellum is activated during many types of cognitive tasks, but its role in attention is not understood. It is likely that the caudate makes important contributions, but what these are and the ways in which they may be distinct from cortical contributions are currently under investigation (e.g., Crofts et ah, 2001). 

M. S. Keshavan, O. G. Bukstein and J. W. Pettegrew, Evidence of developmental alterations in cortical and subcortical regions of children with attention-deficit/hyper-activity disorder. Arch. Gen. Psychiatry, 2008, 65,1419-1428. 

Recently, attempts have been made to reconcile the deficiencies in the dopamine hypothesis by focusing on other neurotransmitters that may interact with dopamine in discrete cortical and subcortical neural circuits. In particular, the involvement of the glutamatergic system has received considerable attention. This possibility has arisen from the finding that dissociation anaesthetics such as ketamine and phencyclidine (PCP) can cause a schizophreniform psychosis in normal individuals. Such effects bear a much closer resemblance to the positive and negative symptoms of... 

Brain glucose utilization decreases when alertness and cognitive performance are impaired by sleep deprivation, especially in the prefrontal cortex, a region involved in alertness, attention, and higher order cognitive processes and in the thalamus, a subcortical structure involved in alertness and attention. 

This rather straightforward chain of situation-reaction relationship can be modified by characteristics of the situation such as additional emotional load caused by danger or time pressure. The "effort" system has the property to disconnect Arousal Systems 1 and 3 to prevent immediate action and dlitate deliberate analysis performed by certain cortical-subcortical brain circuits (Gray, 1982). However, Arousal System 1 facilitates the focusing of attention to the situational demands. In this case, an increase of spontaneous, nonstimulus-specific EDRs will indicate an emotional load that comes with the situation (Fowles, 1980). The ongoing central information processing will be reflected both by the dominance of the beta frequency band over the alpha band in the EEG and a decrease in heart rate variabihly (HRV). 

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