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. 2016 Nov 29;12(1):31.
doi: 10.1186/s12993-016-0115-y.

A functional magnetic resonance imaging investigation of visual hallucinations in the human striate cortex

Hina Abid  1 , Fayyaz Ahmad  2 , Soo Y Lee  3 , Hyun W Park  3 , Dongmi Im  3 , Iftikhar Ahmad  4 , Safee U Chaudhary  5
Affiliations

A functional magnetic resonance imaging investigation of visual hallucinations in the human striate cortex

Hina Abid et al. Behav Brain Funct. .

Abstract

Purpose: Human beings frequently experience fear, phobia, migraine and hallucinations, however, the cerebral mechanisms underpinning these conditions remain poorly understood. Towards this goal, in this work, we aim to correlate the human ocular perceptions with visual hallucinations, and map them to their cerebral origins.

Methods: An fMRI study was performed to examine the visual cortical areas including the striate, parastriate and peristriate cortex in the occipital lobe of the human brain. 24 healthy subjects were enrolled and four visual patterns including hallucination circle (HCC), hallucination fan (HCF), retinotopy circle (RTC) and retinotopy cross (RTX) were used towards registering their impact in the aforementioned visual related areas. One-way analysis of variance was used to evaluate the significance of difference between induced activations. Multinomial regression and and K-means were used to cluster activation patterns in visual areas of the brain.

Results: Significant activations were observed in the visual cortex as a result of stimulus presentation. The responses induced by visual stimuli were resolved to Brodmann areas 17, 18 and 19. Activation data clustered into independent and mutually exclusive clusters with HCC registering higher activations as compared to HCF, RTC and RTX.

Conclusions: We conclude that small circular objects, in rotation, tend to leave greater hallucinating impressions in the visual region. The similarity between observed activation patterns and those reported in conditions such as epilepsy and visual hallucinations can help elucidate the cortical mechanisms underlying these conditions. Trial Registration 1121_GWJUNG.

Keywords: Brodmann area; Functional magnetic resonance imaging (fMRI); K-means clustering; Logistic regression; Visual cortex; Visual hallucinations.

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Figures

Fig. 1
Fig. 1
Block representation of rest and stimulus presentation phases during fMRI scanning of a participant’s brain, for HCC, HCF, RTC and RTX, in 4 sessions. Each session remained for 160 s and comprised of 8 blocks with alternative rest and stimulus phases. 80 scans were taken in each session
Fig. 2
Fig. 2
Summary statistics plot of human visual cortex for four visual stimulus. The visual stimulus types are taken on x-axis and the average voxel activations are on y-axis. The boxplot displays the average voxel activations in the visual cortex of a single participant for each visual stimulus
Fig. 3
Fig. 3
Comparison of activated areas in the visual cortex of a subject. The figure shows a 2 × 2 display of statistical parameter maps (SPM) after presenting HCC, RTC, HCF and RTX. The significant activations are measured using t-scale at p < 0.05 (corrected)
Fig. 4
Fig. 4
Clustering of voxel activation information for HCC, HCF, RTC and RTX, in BA 17, 18 and 19. K-means clustering is used for cluster formation. The x, y and z—axes are labeled as the average voxel activations in BA 17, 18 and 19 respectively
Fig. 5
Fig. 5
Scatter matrix plot of activated information corresponding to visual cortical areas. The plot is a 3 × 3 display with BA 17, 18 and 19 shown in rows (columns) 1, 2 and 3 respectively. The off diagonal cells represents the pairwise correlation of clustered points in BA’s. The cells in lower triangle below the diagonal are the mirror images of the cells in the upper triangle above the diagonal of the matrix plot
See this image and copyright information in PMC

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