Neglect impairs explicit processing of the mental number line.

Area of Science:

• Cognitive Neuroscience
• Neuropsychology

Background:

• Visuospatial attention is crucial for numerical magnitude processing.
• Visuospatial neglect disrupts attentional orienting in both perceptual and numerical space.
• Patients with neglect show biases in numerical tasks, suggesting attention's role.

Purpose of the Study:

• To investigate how visuospatial attention deficits impact numerical processing under different task demands.
• To examine the interaction between neglect, task requirements, and numerical magnitude processing.

Main Methods:

• Administered number comparison and parity judgment tasks to patients with right hemisphere damage (with and without neglect).
• Utilized identical stimuli and response requirements for both tasks to isolate task demands.
• Analyzed performance for biases, asymmetric distance effects, and the SNARC effect.

Main Results:

• Neglect patients performed normally on the parity task (implicit processing) but showed biases in the number comparison task (explicit processing).
• Observed an asymmetric distance effect and a stronger SNARC effect in neglect patients, particularly for larger numbers.
• These findings suggest difficulties in orienting to smaller magnitudes and disengaging from larger ones on the number line.

Conclusions:

• Visuospatial neglect specifically impairs explicit numerical magnitude processing, not implicit processing.
• The observed biases are linked to disrupted attentional orienting in numerical space, mirroring visual attention deficits.
• Neglect's impact on numerical cognition involves failures in both orienting to and disengaging from numerical magnitudes.