Brain connectivity in positive and negative syndrome schizophrenia

Abstract

If, as is widely believed, schizophrenia is characterised by abnormalities of brain functional connectivity, then it seems reasonable to expect that different subtypes of schizophrenia could be discriminated in the same way. However, evidence for differences in functional connectivity between the subtypes of schizophrenia is largely lacking and, where it exists, it could be accounted for by clinical differences between the patients (e.g. medication) or by the limitations of the measures used. In this study, we measured EEG functional connectivity in unmedicated male patients diagnosed with either positive or negative syndrome schizophrenia and compared them with age and sex matched healthy controls.Using new methodology (Medkour et al., 2009) based on partial coherence, brain connectivity plots were constructed for positive and negative syndrome patients and controls. Reliable differences in the pattern of functional connectivity were found with both syndromes showing not only an absence of some of the connections that were seen in controls but also the presence of connections that the controls did not show. Comparing connectivity graphs using the Hamming distance, the negative-syndrome patients were found to be more distant from the controls than were the positive syndrome patients. Bootstrap distributions * Corresponding author.Tel: (0)20 7594 8524; Fax: (0)20 7594 8517; e-mail: a.walden@imperial.ac.uk Preprint submitted to NeuroscienceJune 8, 2010 of these distances were created which showed a significant difference in the mean distances that was consistent with the observation that negative-syndrome diagnosis is associated with a more severe form of schizophrenia. We conclude that schizophrenia is characterised by widespread changes in functional connectivity with negative syndrome patients showing a more extreme pattern of abnormality than positive syndrome patients.

Sample Mean Versus Sample Fréchet Mean for Combining Complex Wishart Matrices: A Statistical Study

“…Such matrices arise frequently, e.g., in EEG studies for brain connectivity [26] and synthetic aperture radar research [12]. We assume K p, since then S has full rank p, and S is positive definite, with probability one.…”

“…The choices for p and K are applicable to the neuroscience studies [25], [26] mentioned in the Introduction; likewise the range of N considered. The same is true of these parameter choices in the further simulations to follow.…”

“…Our motivation to study this topic came from the desire to build improved graphical models for a rare heritage clinical dataset of p = 10 channel neuroscience data, used in schizophrenia studies [26]; see also [25]. The edges of the graphical model are determined from the partial coherencies.…”

Functionally aberrant electrophysiological cortical connectivities in first episode medication-naive schizophrenics from three psychiatry centers

“…With increasing number of independent brain processes, decreases of EEG coherence are to be expected. Several studies on scalp EEG connectivity in schizophrenia indeed reported decreased EEG coherence (e.g., Flor-Henry and Koles, 1984; Merrin and Floyd, 1992; Tauscher et al, 1998; Winterer et al, 2001), but others reported increases (e.g., Ford et al, 1986; Nagase et al, 1992; Mann et al, 1997; Wada et al, 1998) or increases as well as decreases depending on patients' subtype or medication (Knott et al, 2002; Medkour et al, 2010). Some coherence studies analyzed no-task resting, others task conditions, contributing to the differences in results.…”

How Different EEG References Influence Sensor Level Functional Connectivity Graphs

“…Strictly speaking, instead of describing the FCG similarity (Garces et al, 2016) intuitively, the RE can only detect the global difference between the two matrices. To further evaluate the quantized similarity between FCGs, this study exploited HD as another metric to differentiate the two graphs via the transformed times (Makram Talih, 2005; Medkour et al, 2010; van Wijk et al, 2010; Garces et al, 2016). …”