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

Hina Abid,Dongmi Im,Fayyaz Ahmad,Iftikhar Ahmad,Soo Y Lee,Safee U Chaudhary,Hyun W Park

doi:10.1186/s12993-016-0115-y

Abstract

PurposeHuman 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.MethodsAn 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.ResultsSignificant 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.ConclusionsWe 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

Highlights

Cerebrum forms the largest part of human brain
Our results show that visual cortex exhibited significant activations upon presentation of each visual stimulus with highest activations observed for hallucination circle (HCC) proceeded by retinotopy circle (RTC), hallucination fan (HCF) and retinotopy cross (RTX) in order
Analysis of Functional magnetic resonance imaging (fMRI) data obtained from presentation of four visual stimuli Upon presentation of visual stimuli, blood-oxygen-level dependent (BOLD) signals were measured in the visual cortex

Summary

Introduction

Cerebrum forms the largest part of human brain. It comprises of an outer layer called the cerebral cortex which can be further divided into four lobes namely frontal, parietal, occipital and temporal lobe [1]. The cerebral cortex has been classified into 52 cortical Brodmann areas (BA) of which the occipital lobe containing the visual cortex has BAs 17, 18 and 19 [2]. Visual tasks processing related area ‘V1’ is located in BA (striate cortex) while ‘V2–V6’ are located in BA (parastriate cortex) and (peristriate cortex). The ventral stream (‘what pathway’) initiates with V1, passes through V2 and V4, and leads into the inferior temporal cortex (IT cortex). The dorsal stream (‘where pathway’) starts at V1 and proceeds to V2, V6 and V5

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