New Insights from a Not-So-Neglected Field: Hemispatial Neglect

Hemispatial neglect remains one of the most remarkable syndromes investigated by behavioural neurologists. It occurs only after relatively focal (or at least asymmetric) brain damage, most commonly stroke, but is occasionally observed in asymmetric atrophy syndromes such as corticobasal syndrome or Posterior Cortical Atrophy due to Alzheimer’s Disease pathology. It is also sometimes associated with other focal lesions such as tumor, abscess, head injury, or following resection. It is mild and transient in primates, even after large lesions, which reveals that only humans,who may have developed hemispheric asymmetry due to language, have hemispheric specialization for spatial attention or some aspect of attention such that a unilateral lesion causes marked hemispatial neglect. For example, Corbetta and Schulman [1] have proposed a model in which the dorsal spatial attention network is bilateral and symmetric, but the ventral nonspatial frontoparietal attention network is right-hemisphere dominant. Ventral lesions also cause physiological changes and disrupt connections to and within the spatial attention. Only a lesion to the ventral (right) network, which also affects the dorsal network, not the left dorsal network alone, causes marked hemispatial neglect. This model would account for more frequent and severe hemispatial neglect reported in many studies of neglect. However, Kleinman and colleagues [2] reported that hemispatial neglect is equally common after left and right hemisphere stroke, although the type of neglect observed is