Summary: Researchers have mapped specific brain network connections linked to anosognosia — the condition in which individuals are unaware of their own neurological or psychiatric impairments. Using lesion network mapping, the team distinguished separate networks connected to visual and motor forms of anosognosia and identified a shared memory-related network that appears central to awareness of deficits.
By analyzing connectivity from lesion sites associated with loss of vision or motor weakness (both with and without patient awareness), the investigators showed that visual anosognosia and motor anosognosia correspond to distinct functional circuits. A common network that supports awareness across modalities converged on the hippocampus and precuneus, brain regions tied to memory and self-referential processing.
Key Facts:
- Researchers applied lesion network mapping to 267 lesion locations linked to either vision loss or motor weakness, comparing cases where patients were aware of their deficits versus unaware.
- Visual anosognosia (Anton syndrome) involves cortical blindness combined with a lack of awareness of that blindness.
- This study provides the first systematic evidence implicating the hippocampus in visual anosognosia, suggesting that memory-related brain structures are important for comparing current sensory input to stored information and updating self-knowledge about function.
Source: Brigham and Women’s Hospital
What is anosognosia? Anosognosia describes a condition in which a person is unaware of an existing neurological deficit or psychiatric disorder. When it affects vision — often referred to as Anton syndrome — patients can be cortically blind yet insist they can see. Understanding the neural networks behind this lack of awareness can illuminate how the brain monitors and updates knowledge about its own abilities.
A research team at Brigham and Women’s Hospital, part of the Mass General Brigham system, investigated the brain circuits tied to unawareness in both visual and motor domains. They examined 267 lesion locations previously associated with either visual loss (with and without awareness) or motor weakness (with and without awareness), mapping each lesion’s functional connections to large-scale resting-state networks derived from 1,000 healthy participants.
Using lesion network mapping, a method that links focal brain injuries to the distributed networks they disrupt, the investigators identified distinct circuit patterns for each form of anosognosia and a shared network that appears critical for awareness itself. The visual anosognosia network showed connectivity to visual association areas and regions involved in higher-order metacognitive processing, while the motor anosognosia network involved the insula, supplementary motor area, and anterior cingulate — regions important for interoception, motor control, and performance monitoring.
Importantly, the cross-modal network that correlated with unawareness across both visual and motor deficits centered on the hippocampus and precuneus. These structures are well known for their roles in memory consolidation, episodic recall, and self-referential thought, suggesting that awareness of a deficit requires access to stored information about prior abilities and ongoing comparison between current performance and past experience.
“Although visual anosognosia has been described for more than a century, formal, systematic analysis of its neural substrates has been limited,” said Isaiah Kletenik, MD, corresponding author and investigator in the Division of Cognitive and Behavioral Neurology and the Center for Brain Circuit Therapeutics at Brigham. “Our findings are the first to identify a role for the hippocampus in visual anosognosia in a systematic network-based analysis. Memory-related structures appear necessary for recognizing a deficit by comparing incoming visual information to previously stored information and updating one’s self-knowledge about abilities.”
About this psychology and neuroscience research news
Author: Haley Bridger
Source: Brigham and Women’s Hospital
Contact: Haley Bridger – Brigham and Women’s Hospital
Image: The image is credited to Neuroscience News
Original Research: Closed access. “Network Localization of Awareness in Visual and Motor Anosognosia” by Isaiah Kletenik et al., Annals of Neurology.
Abstract
Network Localization of Awareness in Visual and Motor Anosognosia
Objective
Anosognosia — unawareness of a deficit — can affect vision or motor function and offers an opportunity to study how awareness itself is generated. Lesions that produce anosognosia are found in many different anatomical locations, so the authors asked whether these disparate lesions might map onto common functional networks that explain the behavioral syndrome.
Methods
The team analyzed 267 lesion locations tied to either vision loss (with and without awareness) or motor weakness (with and without awareness). For each lesion, they computed the network of brain regions functionally connected to the lesion site using resting-state connectivity from a normative sample of 1,000 healthy adults. This approach allowed identification of both domain-specific circuits and cross-modal networks associated with awareness.
Results
The network specific to visual anosognosia was connected to visual association cortex and posterior cingulate regions, while the motor anosognosia network involved the insula, supplementary motor area, and anterior cingulate. A shared cross-modal anosognosia network was defined by connectivity to the hippocampus and precuneus (false discovery rate < 0.05), implicating memory-related structures in the awareness of deficits.
Interpretation
These findings reveal distinct network connections underlying visual and motor anosognosia and identify a common awareness network centered on memory-associated brain regions. The results support a model in which awareness of impairment requires comparison of current sensory or motor performance against stored memories of prior function, mediated by hippocampal and precuneus circuitry. Understanding these networks may guide future studies of self-monitoring, rehabilitation strategies, and targeted neuromodulation approaches for patients with anosognosia.