2008年9月一期的爱思唯尔期刊《大脑皮层》（Cortex）最近刊登了伦敦精神病学研究所的一项最新研究，研究对于人们出现的幻觉进行了研究，结合脑功能成像方法来捕捉产生幻觉瞬间大脑区域发生的变化，继而揭开产生的幻觉的原因。
幻觉是一种虚幻的表象，本来并不存在的某种事物，人们有时却感知它的存在。正常人偶尔会可出现幻觉，这往往与心理有密切关系，此外在受到突然强烈的刺激下亦可出现幻觉。但是另外一种持续时间较长，与心情无密切关系的幻觉，往往见于精神分裂症患者。对于幻觉的研究目前知之甚少，因为幻觉的产生具有不可预测性，同时往往瞬间发生。所以很难知道大脑出现幻觉时候的变化。为了研究产生幻觉时候脑部区域的变化，研究人员采用了特别的方法，比如使用闪烁的灯光，生动的颜色等，刺激人产生幻觉，同时结合使用的脑功能成像方法来捕捉产生幻觉瞬间大脑区域发生的变化，继而揭开产生的幻觉的原因。
研究发现，幻觉出现时候，脑内视觉系统有着明显地变化。研究人员认为视觉系统在传递信号中，由于外界干扰等因素，这部分信号在向大脑视觉系统传输中出现了短暂的“中断”，这使得人类的大脑对于处理信息发生了紊乱，继而导致了幻觉的产生。（生物谷Bioon.com）
生物谷推荐原始出处：
Cortex，doi:10.1016/j.cortex.2008.04.005，Dominic H. ffytche
The hodology of hallucinations
Dominic H. ffytche,
Centre for Neuroimaging Sciences, Institute of Psychiatry, De Crespigny Park, London, UK
Abstract
The hodotopic framework is a recent revision of Geschwind's disconnection paradigm incorporating advances in functional and white matter imaging. Its intention is to help clinico-pathological correlations across a range of neurological and psychiatric conditions and generate novel research questions. Here I consider hallucinations within this framework. The paper is divided into three parts. The first reviews the auditory and visual hallucination literature from the dual perspectives of dysfunction localised to specific brain regions (topological) and dysfunction related to connections between brain regions (hodological), combining evidence from tractography, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) studies. Patients prone to hallucinations have complex, task-specific hodological abnormalities that persist between hallucination episodes. During hallucinations, topological increases in activity are found whose location defines hallucination content and modality. Whether these activity increases are accompanied by transient hodological change is unclear. The second part of the paper addresses this issue in EEG and fMRI studies of a 200-year-old paradigm. Photic stimulation within a specific frequency and luminance range induces hallucinations of geometrical patterns, colours and motion in normal subjects. By comparing hallucination-inducing with control stimulation, topological activity increases were identified in visual areas whose specialisations matched the induced hallucination contents. During hallucinations, fMRI connectivity between LGN and cortex changed from a positive to negative relationship while EEG connectivity between occipital and other brain regions increased. The complex and dynamic topological and hodological changes during induced hallucinations are consistent with a shift in thalamocortical circuitry from tonic to burst mode and may have direct relevance to the Charles Bonnet Syndrome. The third part of the paper considers the relevance of the finding to other disorders, examines the strengths and limitations of our current imaging approaches to connectivity and looks to future developments in the field.
