Unraveling anosognosia: revealing brain networks hidden in ignorance

Summary: Researchers have identified specific brain network connections associated with anosognosia, a condition in which patients are unaware of their neurological or psychiatric disabilities.

Using a technique called lesion network mapping, they identified separate networks linked to visual and motor anosognosia and a shared network responsible for awareness of these impairments. The shared network converged on the hippocampus and precuneus, both of which are associated with memory.

This is the first systematic analysis to highlight the role of the hippocampus in visual anosognosia.

Key Facts:

  1. Lesion network mapping was the main technique used by the researchers to examine the connectivity patterns of 267 lesion sites associated with vision loss or impairment (with and without awareness).
  2. Visual anosognosia, also known as Anton syndrome, involves complete cortical blindness and unawareness of this visual loss.
  3. This study identifies the role of the hippocampus in visual anosognosia for the first time, suggesting that memory-related structures are necessary to identify deficits by comparing current visual input with previous information stored in memory.

Source: Brigham and Women’s Hospital

Anosognosia is a condition in which a patient is unaware of a neurological deficit or psychiatric condition. Visual anosognosia, also known as Anton syndrome, is associated with complete cortical blindness and lack of awareness of vision loss.

Researchers at Brigham and Women’s Hospital, a founding member of the Mass General Brigham Healthcare System, sought to identify brain network connections associated with anosognosia.

The researchers analyzed the connectivity patterns of 267 lesion sites associated with visual loss (with and without awareness) or weakness (with and without awareness).

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To test whether these lesion-induced deficits map to specific brain networks, the researchers used a recently validated technique called lesion network mapping. They were also able to identify distinct network connections associated with visual anosognosia and motor anosognosia, and a shared network for awareness of these impairments.

The visual anosognosia network was defined by connectivity to visual and metacognitive processing areas, while the shared network for awareness was associated with memory in the hippocampus and precuneus-brain structures.

“Despite being described over 100 years ago, visual anosognosia has had little systematic analysis,” said corresponding author Isaiah Kledenick, an investigator in Brigham’s Center for Cognitive and Behavioral Neuroscience and Brain Circuit Therapy.

“Our results are the first to identify the role of the hippocampus in a systematic analysis of visual anosognosia.

“Memory-related structures are essential for identifying deficits by comparing visual inputs with previous information stored in memory while updating self-knowledge of performance relative to previous 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 film is credited to Neuronews

Original Research: Closed access.
Network localization of awareness in visual and motor anosognosia” Isaiah Kledenic et al. Neurological studies


Summary

Network localization of awareness in visual and motor anosognosia

objective

Ignorance of a deficit, anosognosia, can result from visual or motor impairments and provides insight into awareness; However, lesions associated with anosognosia occur in different brain locations.

methods

We analyzed 267 lesion sites associated with visual loss (with and without awareness) or weakness (with and without awareness). The network of brain regions connected to each lesion site was calculated using resting-state functional connectivity from 1,000 healthy subjects. Both domain-specific and cross-modal associations with awareness were identified.

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Results

A domain-specific network for visual anosognosia demonstrated connectivity to the visual association cortex and posterior cingulate, while motor anosognosia was defined by the insula, supplementary motor area, and anterior cingulate connectivity. Cross-modal anosognosia network defined by hippocampus and precuneus (false discovery rate) connectivity. p<0.05).

Explanation

Our results identify distinct network connections associated with visual and motor anosognosia and a shared, cross-modal network for awareness of deficits centered on memory-related brain structures.

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