Two neural systems for visual orienting and the pathophysiology of unilateral spatial neglect

Abstract

This chapter critically assesses current neurobiological models of attention and unilateral spatial neglect, particularly in relation to neuroimaging results acquired over the last decade. It highlights that these models do not account for significant discrepancies between lesion studies and neuroimaging results. It then reports a new experiment that clarifies some of these discrepancies and proposes a revision of current models. It is noted that lesions causing neglect in the frontal lobe do not match with frontal areas of activation during visuospatial attention; rather, they better match the location of regions mediating alerting/vigilance. Moreover, the current evidence supports a role for human anterior cingulate cortex (AC) in response evaluation and monitoring, and not stimulus selection or motivation. It is also shown that temporoparietal junction (TPJ) plays a critical role in alerting. The proposed model clarifies some of the discrepancies between neuropsychological studies of neglect and brain imaging studies of visuospatial attention, and provides novel information on the pathophysiology of neglect.

Cerebral correlates of visuospatial neglect: A direct cerebral stimulation study

“…Somewhat similarly, it has been proposed that, in right-brain damaged patients with damage to the IPL-TPJ, the deficit of spatial attention may result from a disconnection between these ventral regions and the SPL [Szczepanski et al, 2010]. Accounts of this sort predict that interference by DES with the function of the right SPL may bring about spatial neglect, causing a temporary left-right imbalance, with a right hemispheric dysfunction, and are consistent with the r Neglect and Direct Cerebral Stimulation r r 1345 r present findings, although the weak association between structural damage to the SPL and spatial neglect remains to be explained [see also Corbetta, 2002;Shulman et al, 2010].…”

“…The suggestion has been made that the lesions typically associated with spatial neglect, ''ventral'', perisylvian, involving the IPL, the TPJ, the STG, and the ventral premotor cortex [Committeri et al, 2007;Mort et al, 2003;Vallar, 2001;Verdon et al, 2010] cause a ''dorsal'' functional imbalance in the IPS-SPL, with a relative left hemisphere SPL hyperactivity being related to neglect severity [Corbetta et al, 2005[Corbetta et al, , 2008 for discussion]. Accounts of this sort predict that interference by DES with the function of the right SPL may bring about spatial neglect, causing a temporary left-right imbalance, with a right hemispheric dysfunction, and are consistent with the r Neglect and Direct Cerebral Stimulation r r 1345 r present findings, although the weak association between structural damage to the SPL and spatial neglect remains to be explained [see also Corbetta, 2002;Shulman et al, 2010]. Accounts of this sort predict that interference by DES with the function of the right SPL may bring about spatial neglect, causing a temporary left-right imbalance, with a right hemispheric dysfunction, and are consistent with the r Neglect and Direct Cerebral Stimulation r r 1345 r present findings, although the weak association between structural damage to the SPL and spatial neglect remains to be explained [see also Corbetta, 2002;Shulman et al, 2010].…”

Context-dependent modulation of natural approach behaviour in mice

“…Innate approach responses, therefore, must be triggered by specific combinations of visual features that indicate reward, but they must be flexibly modulated by internal state, context, or experience on distinct time scales [9]. Furthermore, the ability to control visual orienting responses is impaired in several prevalent neurological diseases and neurodevelopmental disorders [10] such as trauma-induced visuospatial neglect [11], post-traumatic stress disorder (PTSD) [12,13], attention deficit and hyperactivity disorder (ADHD) [14], generalized anxiety disorder [15], schizophrenia [16] and autism [17]. Currently, the mechanisms underlying conserved visually guided approach responses in mammals and their context-dependent modulation remain unclear.…”

Hemispheric asymmetries of motor versus nonmotor processes during (visuo)motor control

“…Whereas since left‐hemisphere motor dominance does not exclude the likelihood of right‐hemisphere lateralization of attention system [Corbetta and Shulman, 2002; Culham et al, 2006; Marshall and Fink, 2003]. This notion originates from patient observations revealing right more than left hemisphere lesions to be associated with a prevalence of unilateral spatial neglect, which is characterized by deficits in attending or responding to stimuli in the contralesional field [Corbetta et al, 2002b; Hillis et al, 2005; Karnath et al, 2004; Mesulam, 1999; Mort et al, 2003; Weintraub and Mesulam, 1987]. Previous fMRI research in healthy subjects has distinguished a dorsal (DAN) and a ventral attention network (VAN).…”