Neglect Syndrome and the Spatial Attention Network

Introduction of Neglect Syndrome and the Spatial Attention Network

Neglect syndrome is a common neurological syndrome that mainly occurs after injury to the right hemisphere and is characterized by spatial and non-spatial defects. Neglect is not a single symptom, but a collection of uneven symptoms caused by discrete lesions in the right hemisphere. In patients with neglect syndrome, attention to contralateral events is significantly reduced, it showed unwillingness to shift their attention to the left, and unable to effectively find targets embedded in the left hemisphere. Side neglect syndrome is thought to reflect the damage of large-scale frontal and parietal lobe networks, and this network usually maintains the adaptive distribution of spatial attention. It is more likely to be a distributed cortical network spatial attention dysfunction, and it is not structural damage in a specific brain area.

Regulatory Mechanisms and Potential Targets

Most lesions of neglect syndrome are in the survey area of the right hemisphere, called the outer cortex. These include the inferior parietal lobule (IPL), the angular gyrus and the superior marginal gyrus, the temporal parietal junction (TPJ), the superior temporal gyrus (STG), and the frontal cortex, including the inferior frontal gyrus (IFG) and the middle frontal gyrus (MFG). On the other hand, neglect and/or spatial attention deficits are also associated with damage to the right dorsal cortex, including superior frontal gyrus/frontal eye field (SFG/FEF) and superior parietal lobe (SPL). In addition, some subcortical structures are also related to neglect, the thalamus and certain white matter, such as the upper longitudinal tract (SLF) II, SLF III and arcuate tract (AF), inferior longitudinal tract, inferior frontal occipital tract (IFOF) and extreme capsule (EmC).

Fig.1 Structural connectivity in the spatial attention network damaged in neglect patients. (Hattori, 2018)

Some current research results indicated that the choline system plays a role in guiding attention to discover and distinguish visual information, while the dopamine system is mainly related to the working memory process. However, the process of visual spatial attention and working memory is not completely separated, so the spatial attention network of neglect syndrome is also regulated by the interaction mechanism of the cholinergic system and dopamine.

Conventional Treatment of Neglect Syndrome

• Cueing

Many clinical methods use clues to break neglect and play an effective role in the early stages of the disease or cases of closed head injuries.

• Patching

When the irritation occurs in the opposing area, using a patch on the same diseased eye enhances the effect of the mound-like mechanism.

• Drug therapy

The results of the study show that cholinergic blockers reduce the cost of distracting attention, and norepinephrine reduces the alertness effect, indicating that drug treatment can be applied to neglect syndrome.

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Reference

1. Hattori, T.; et al. Structural connectivity in spatial attention network: reconstruction from left hemispatial neglect. Brain imaging and behavior. 2018, 12(2): 309-323.