Scholarship 10

10th Annual Scholarship (April 2009)


​             made to  Dr. Veena Kumari from England

on the subject of Functional MRI Investigation of Dysfunctional Impulsivity in Healthy People and Patients with

                           Schizophrenia



Report Abstract (699 words):


Dickman (1990) proposed two fundamental aspects of impulsivity: ‘dysfunctional’ and ‘functional’ impulsivity. Dysfunctional impulsivity reflects ‘recklessness without deliberation and evaluation of consequences’ and is generally associated with negative outcomes whereas functional impulsivity reflects ‘a fast responding to situational demands in order to maximise one’s circumstances’ (e.g. in sports) and often has positive outcomes. The aim of this study was to examine the brain basis of dysfunctional impulsivity in healthy people and in people with schizophrenia.
 

Data were collected as part of a larger neuroimaging project (Kumari et al., 2006, 2009). The fMRI data set consisted of whole brain fMRI images in 14 healthy controls (one excluded due to poor image quality) and 24 male patients with schizophrenia (3 excluded: one failed to follow task instructions and two had very high error rates). Ten of 21 patients had a history of serious repetitive violence but they did not meet the diagnostic criteria for co-morbid antisocial personality disorder (APD). All participants were male, right handed and between 18–55 years of age.  Dysfunctional and functional impulsivity was sampled using the Impulsiveness-Venturesomeness-Empathy questionnaire (IVE-7) (Eysenck et al., 1985). Within the Eysenckian framework, dysfunctional impulsivity (as in Dickman’s terminology) can be indexed using the Impulsiveness subscale while the functional impulsivity can be indexed using the Venturesomeness subscale of the IVE-7 (Eysenck, 2004). 
 

All participants underwent fMRI during a Go/NoGo task. It consisted of 450 visual stimuli displayed over a 7.5 minute period, produced using a PC and projector system within the fMRI scanner. The stimuli consisted of either a large black circle (designated as the Go stimulus) or a smaller black circle (designated as the NoGo signal).  The task required the participant to respond during the Go signals, using a button box, and to suppress their responses to the NoGo circles. The stimuli sequences consisted of 15 x 30-second blocks (each block had 30 stimuli signals). Stimuli blocks consisted of the Go condition (a constant series of execute signals) or the NoGo condition (where 20-40% of the signals were inhibitory, arranged pseudorandomly with Go signals). Response accuracy and latency data were obtained online for all participants. fMRI data were analysed using Statistical Parametric Mapping (SPM5).
 

The results revealed that people with schizophrenia and a history of serious violence had elevated Impulsiveness scores but had comparable Venturesomeness scores relative to non-violent schizophrenia patients and healthy controls. Impulsiveness scores did not correlate significantly with task performance in healthy controls or patients. Impulsiveness, but not Venturesomeness, scores correlated with lower activity in the anterior cingulate during the NoGO (relative to Go) condition healthy controls.  In the patient group, Impulsiveness was associated with reduced inferior temporal and hippocampal activity during the NoGO condition.
 

This is the first study to our knowledge to examine fMRI correlates of dysfunctional impulsivity, and indicates reduced anterior cingulate activity in men with high scores on this dimension. The finding showing an association between dysfunctional impulsivity and reduced hippocampal activity in the patient group is in line with our previously reported association between reduced hippocampal volume and dysfunctional impulsivity in schizophrenia (Kumari et al., 2009). The present findings, combined with our earlier observations of reduced anterior cingulate activation during a working memory task in violent APD individuals (Kumari et al., 2006), suggest that the association between dysfunctional impulsivity and antisocial and criminal behaviour may be mediated via deficient (inhibitory) functions of the anterior cingulate and hippocampus.
 

References
 

Dickman SJ (1990). Functional and dysfunctional impulsivity: personality and cognitive correlates. Journal of Personality and Social Psychology, 58(1), 95-102. 

Eysenck SBG (2004). How the impulsiveness and venturesomeness factors evolved after the measurement of psychoticism. In Stelmack RM (Ed), On the Psychobiology of Personality: Essays in Honor of Marvin Zuckerman. Elsevier: Oxford, pp 107-112

Eysenck SBG, Pearson PR, Easting G, & Allsopp JF (1985). Age norms for impulsiveness, venturesomeness and empathy in adults. Personality and Individual Differences, 6, 613–619.

Kumari V, Aasen I, Taylor P, et al. (2006). Neural dysfunctioning and violence in schizophrenia: An fMRI Investigation. Schizophrenia Research 84: 144-164.

Kumari V, Barkataki I, Flora S, et al. (2009).  Dysfunctional, but not functional, impulsivity is associated with a history of seriously violent behaviour and reduced orbitofrontal and hippocampal volumes in schizophrenia. Psychiatry Research: Neuroimaging 173(1):39-44.

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