Neglect

• Contralesional stimuli


  Things occurring on the opposite side to the lesion
• Ipsilesional stimuli


  Things occurring on the same side as the lesion
• Extinction


  Form of neglect - only occurs when stimuli occur on both sides of space
• Middle Cerebral Artery (MCA)


  • Largest branch of the internal carotid, supplies lateral and inferior frontal lobe, and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, Broca's area
• Anterior Cerebral Artery (ACA)


  • Supplies the medial frontal lobes, basal ganglia, primary motor cortex
• Posterior Cerebral Artery (PCA)


  • Supplies temporal and occipital lobes
• Clinical presentation of MCA stroke


  • Contralesional hemiparesis (weakness/inability to move opposite side of body/face)
  • Contralesional hemisensory loss (e.g. inability to feel touch on opposite side of body/face)
  • Hemianopia (loss of vision on opposite side of space)
  • Aphasia (if stroke affects the dominant hemisphere for language – usually left)
  • Hemispatial neglect
• Tests used to assess hemispatial neglect


  • Cancellation tests
  • Copying tests
  • Line bisection tests
• Hemispatial neglect is not specific to any sense
• A patient with neglect will have difficulty identifying contralesional visual, auditory and tactile stimuli
• Extinctionsymptom 


  Patients can detect contralesional stimuli - but not when they occur with ipsilesional stimuli
• Hemispatial neglect


  Disorder of attention and/or spatial representation, inability to consciously detect or respond to stimuli in the contralesional side of space
• Neglect is more common (and persistent) in right hemisphere stroke patients (38%) than in left hemisphere stroke patients (18%)
• Right hemisphere stroke patients may have additional (nonspatial) deficits that interact with and exacerbate spatial deficits
• Attention can operate at a late stage of processing - severity of extinction can be modulated by higher-level properties of stimuli
• Unattended items are processed up to the semantic level in extinction
• Preattentive processing


  Information processed prior to attention and awareness
• Types of preattentive processing


  • Task-relevance of stimuli (response related information)
  • Integration of features into whole objects/shapes
  • Emotional significance of stimuli
  • Semantic information
• Patients with neglect have trouble disengaging from stimuli on the ipsilesional side to focus on contralesional stimuli
• Spatial attention is a competitive process
• Neglect may not be a unitary disorder, but rather a syndrome with dissociable components
• Attention is...

  • Competitive
  • Operative in object-framed response
  • Operative on internal responses & external stimuli