Brain Deficits in Visual Hallucinations

One the early things I was taught in my neuroscience training was that new-onset visual hallucinations need to be assessed for medical or "organic causes".

Auditory hallucinations were felt to be more characteristic of schizophrenia.

One medical disorder linked to visual hallucinations is dementia with Lewy bodies (DLB). 

DLB is second to Alzheimer's disease in producing neurodegenerative dementia. Visual hallucinations is a hallmark of DLB and is found in up to 70% of clinical samples with the disorder.

A recent study from France provides insight into the neuroanatomical correlates of visual hallucinations in DLB.

Researchers in this study used single-photon emission computed tomography (SPECT) in a group of 36 subjects with DLB who reported visual hallucinations.

This group of cases was compared to 30 subjects with DLD who did not report visual hallucinations.

Specific differences in blood flow were noted with visual hallucinations. Visual hallucinations subjects had diminished cerebral perfusion in the following regions.

• Left anterior cingulate cortex
• Left orbitofrontal cortex
• Left cuneus

Deficits in regional cerebral perfusion in several areas correlated with the severity of visual hallucinations:

• Bilateral anterior cingulate cortex
• Left orbitofrontal cortex
• Right parahippocampal gyrus
• Right inferior temporal cortex
• Left cuneus

The authors note the cuneus (also known as Brodmann's area 18). This region is known as a secondary visual integration area. Reduced blood flow to this region may contribute to visual processing errors and the subjective sensation of visual hallucinations. Perfusion deficits in more anterior regions may contribute to inability to recognize the visual hallucinations as abnormal.

This study is one of many emerging showing specific clinical features of neuropsychiatric disorders may relate to specific neuroanatomical deficits and impairment.

Readers with more interest in this topic can access the free full-text manuscript by clicking on the citation below.

Image of left cingulate cortex is an iPad screen shot from the app 3D Brain from the author's files.

Follow the author on Twitter @WRY999

Heitz C, Noblet V, Cretin B, Philippi N, Kremer L, Stackfleth M, Hubele F, Armspach JP, Namer I, & Blanc F (2015). Neural correlates of visual hallucinations in dementia with Lewy bodies. Alzheimer's research & therapy, 7 (1) PMID: 25717349