What are the effects of angular gyrus involvement?

Effects of Angular Gyrus Involvement

Angular gyrus involvement can cause a wide range of cognitive deficits including language processing problems, autobiographical memory impairment, spatial awareness issues, and difficulties with multimodal integration, with specific symptoms depending on which subdivision of the angular gyrus is affected and its connectivity patterns. 1

Key Functions and Deficits Associated with Angular Gyrus Involvement

Language and Communication Deficits

• Angular gyrus damage can lead to lexical agraphia (writing impairment) and sentence processing difficulties 1
• The left angular gyrus plays a critical role in language elaboration, making it particularly important for verbal communication 2
• Damage to the angular gyrus can disrupt its connectivity with language networks, as it serves as a connector epicenter linking multiple functional networks 2

Memory Impairments

• Angular gyrus dysfunction impairs autobiographical memory, particularly free recall of personal events, while cued recall may remain relatively intact 3
• Patients show reduced ability to experience autobiographical memories from a first-person perspective following angular gyrus disruption 3
• The angular gyrus plays a crucial role in integrating multimodal features during episodic memory retrieval, with greater activity observed during retrieval of integrated multimodal memories compared to unimodal memories 4

Spatial Cognition and Awareness

• Angular gyrus damage can cause left-right confusion and finger agnosia (inability to identify fingers), which are components of Gerstmann's syndrome 1
• The right angular gyrus is particularly important for spatial attention and awareness 2
• Attention deficits are common following angular gyrus damage 1

Numerical Processing

• Number processing impairments are observed following angular gyrus damage 1
• This contributes to the constellation of symptoms in Gerstmann's syndrome, which includes acalculia (difficulty with mathematical calculations) 1

Multimodal Integration

• The angular gyrus serves as a multimodal integration hub, combining information from different sensory modalities 4
• Damage disrupts the integration of sensory inputs that modulate motor control and planning 2
• Multivariate pattern analysis can distinguish episodic memory representations in the angular gyrus according to whether they are multimodal or unimodal in nature 4

Connectivity and Network Considerations

• The angular gyrus is positioned at the junction between parietal, temporal, and occipital lobes, making it a critical connector hub 2

• It has extensive structural connectivity through:

  • Association fibers (superior and inferior longitudinal fasciculi)
  • Short-range connections to parietal, occipital, and temporal regions
  • U-shaped fibers in the posterior transverse system
  • Striatal, thalamic, and brainstem connections
  • Inter-hemispheric homotopic callosal connectivity 2

• Angular gyrus is part of the Default Mode Network (DMN), with activity positively correlated with level of consciousness 5

• High-frequency repetitive transcranial magnetic stimulation (rTMS) over the left angular gyrus can improve consciousness levels in minimally conscious state patients, but not in vegetative state patients 5

Clinical Implications

• Symptoms following angular gyrus damage are heterogeneous due to:

  1. Damage to different subdivisions of the angular gyrus
  2. Disruption of different connectivity profiles
  3. Varying extent of lesions into neighboring regions 1

• Inter-patient variability in symptoms depends on:

  • Time post-stroke
  • Demographics
  • Therapy input
  • Pre-stroke differences in functional anatomy 1

• In opioid use disorder (OUD), neuroimaging studies have shown:

  • Increased amplitude of low-frequency fluctuations (ALFF) in bilateral angular gyrus compared to healthy controls 6
  • Increased dorsal anterior cingulate cortex (dACC) connectivity to the angular gyrus 6

Diagnostic and Treatment Considerations

• Modern lesion-symptom mapping approaches are needed to fully characterize angular gyrus syndrome 1
• Better integration of lesion and functional neuroimaging investigations is required to understand angular gyrus function as a hub within the DMN 1
• Neuromodulation targeting the angular gyrus shows promise for treating disorders of consciousness, with high-frequency rTMS over the left angular gyrus improving clinical scores in minimally conscious state patients 5